Laser technologies - UNIDO Institute for Capacity Development

Laser technologies: a step forward for small and medium
enterprises
INTERNATIONAL CENTRE
FOR SCIENCE AND HIGH TECHNOLOGY
The opinions expressed in this publication do not necessarily reflect the views of the
United Nations Industrial Development Organization (UNIDO) or the International Centre
for Science and High Technology (ICS). Mention of firms’ names and commercial products
does not imply endorsement by UNIDO or ICS.
Any specifications or costs contained in this publication are for reference only; they reflect
the market conditions at the time of writing.
All pictures are in low definition in order to facilitate downloading and may not reflect the
true finish of products. For more defined pictures the reader should refer to ICS UNIDO.
No use of this publication may be made for resale or for any other commercial purpose
whatsoever without prior permission in writing from ICS.
Cover page insets include pictures of laser applications (from left to right, from top to
down):
□ marked metal component;
□ 2D cut on stainless steel sheet;
□ Cut and marked clothing items.
Thanks go to all the companies and institutions mentioned in the chapter on ‘SOURCES
OF INFORMATION‘and also to those that shared their know-how but prefer not to be
named.
ICS-UNIDO is supported by the Italian Ministry of Foreign Affairs
© United Nations Industrial Development Organization and the International Centre for
Science and High Technology, 2008
High Technology and New Materials
International Centre for Science and High Technology
ICS-UNIDO, AREA Science Park
Padriciano 99, 34012 Trieste, Italy
Tel.: +39-040-9228126 Fax: +39-040-9228122
E-mail: [email protected]
ii
Laser technologies: A step forward for small and medium sized enterprises
Prepared by:
Nicola Drago
Paolo Villoresi
Graziano Bertogli
INTERNATIONAL CENTRE FOR SCIENCE AND HIGH TECHNOLOGY
Trieste, 2008
iii
LASER TECHNOLOGIES: A STEP FORWARD FOR SMALL AND MEDIUM ENTERPRISES
Laser technologies
Lasers in the future: Perspectives for small and medium sized enterprises
ABSTRACT
This publication provides an overview of present and future laser technology applications for
industrial products manufacturing, e.g. metal and non-metal processing (cutting, marking,
welding) and quality control. The target audience is small and medium sized enterprises (SMEs) in
order to raise their interest in these technologies, which could be complementary and, in certain
cases, more profitable alternatives to conventional manufacturing technologies, due to their good
flexibility, quality of output and decreasing investment cost. This report is organised in two parts:
Laser technologies and Lasers in the future: Perspectives for small and medium enterprises
The first part of the report consists of a description of laser techniques, a review of some real
manufacturing cases in SMEs, and a review of some of the research and development (R&D)
literature. The applications (cutting, marking, inspection, manual welding) were chosen based on
the following criteria: a) highest market share, as an indication of reliability; b) investment of less
than €1 million; c) basic level competence required. These are suggestions only; there are many
other applications, and technology developments and improvements are continuing in aspects,
such as efficiency, cooling and space requirements, speed, flexibility and price. The
manufacturing sector was chosen both because of the high added-value of laser technologies in
this sector, and its importance in the industrial bases of developing or transition economies.
The second part of the report focuses on laser technologies and applications, e.g. a)
semiconductor high power lasers, b) continuous wave and pulsed fibre lasers, and c) solid state
disc and advanced CO2 lasers.
Furthermore, this publication examines some of the novel interaction mechanisms enabled by
these new technologies which provide opportunities for SMEs and entrepreneurs to undertake
novel processes.
Finally the input from the scientific research to the laser application market is reviewed along with
descriptions of applications with long term potential.
Laser technologies are a remarkable and a progressively more accessible option to obtain new
products from a variety of materials (metal, plastic, leather, wood, paper and others) in
competitive conditions. However, in calculating the returns from investment in laser technologies
it must be remembered that lasers are not a panacea for every industrial process; although they
may have advantages over other technologies, learning will be required through experimentation
with configurations and materials, co-design between client and supplier to provide product
enhancements, and formalisation of know-how to increase efficiency. Finally, SMEs will need to
find appropriate financing schemes for their investments.
This work is based on interviews with original equipment manufacturers (OEM), laser system
integrators and manufacturing SMEs that utilise these technologies, combined with a review of
some recent literature.
For a more theoretical approach, the ICS Lectures on Industrial Applications of Lasers (2000,
ISBN 92-1-106408-2) is recommended.
iv
Part 1: LASER TECHNOLOGIES
v
SUMMARY
ACRONYMS ......................................................................................................................... x
1
INTRODUCTION TO LASER TECHNOLOGIES ............................................................ 1
2
SAFETY AND ENVIRONMENTAL PROTECTION ......................................................... 4
3
METAL PRODUCTS .................................................................................................... 7
3.1
CUTTING............................................................................................................ 7
3.1.1
SMALL JEWELLERY AND DECORATION COMPONENTS....................... 11
3.1.2
PARTS FOR LIGHT INDUSTRIAL EQUIPMENTS ..................................... 12
3.1.3
CUTTING FOR FABRICATION.................................................................. 14
3.2
MARKING ........................................................................................................ 16
3.2.1
A MARKING CASE .................................................................................. 18
3.3
MANUAL LASER REFURBISHMENT OF DIES AND MOULDS......................... 20
3.4
LASER WELDING PROCESS ........................................................................... 22
4
NON-METAL APPLICATIONS: TEXTILE, GLASS AND OTHERS ................................ 26
4.1
A FASHION MARKING CASE ........................................................................... 29
4.2
TEXTILE PATCH PRODUCTION........................................................................ 32
4.3
CRYSTAL PROMOTIONAL GADGETS .............................................................. 34
5
LASER INSPECTION................................................................................................. 35
6
LOOKING AHEAD ..................................................................................................... 36
7
BIBLIOGRAPHY ........................................................................................................ 37
8
SOURCES OF INFORMATION .................................................................................. 40
9
ANNEX: ARTICLE SYNOPSIS.................................................................................... 41
vi
List of figures
Figure 1: laser components
1
Figure 2: potential harms from portable devices
5
Figure 3: laser on welding glove
5
Figure 4: burn from partial 2kW CO2 laser reflection
Figure 5: finger injury at the accident, after 10 days, after 21 days
5
5
Figure 6: 2D cut on stainless steel sheet
8
Figure 7: 3D cut on tube
8
Figure 8: reduced scrape
Figure 9: laser cut pendants for jewellery (on the right)
10
11
Figure 10: small size laser cut components
11
Figure 11: laser cut and engraved component
11
Figure 12: lay out with 2 cutting machines
12
Figure 13: laser cut stainless steel samples
13
Figure 14: laser cut item
13
Figure 15: lasing gas cylinders
Figure 16: cutting gas storage
13
13
Figure 17: 4-lasers lay-out
14
Figure 18: fabricated frame from laser cut components
15
Figure 19: laser cut profile in mild steel for fabrication
15
Figure 20: fabrication job-shop lay-out
15
Figure 21: marked metal coloured component
17
Figure 22: marked metal component
Figure 23: detailed picture marked on plate
17
17
Figure 24: marked instrument manifold
18
Figure 25: marking lay-out sketch
19
Figure 26: welded item
20
Figure 27: repaired mould
20
vii
Figure 28: welding in an inside edge
20
Figure 29: cross section of filler deposit
Figure 30: class I laser manual welder with open doors
20
21
Figure 31: mould repair with a class IV manual laser welder
21
Figure 32: Reflection coefficient, wavelength, materials
22
Figure 33: temperature and welding section
23
Figure 34: plasma generation
23
Figure 35: speed, power and penetration
23
Figure 36: influence factors
Figure 37: lap seam welding scheme
23
24
Figure 38: lap welding cross section
24
Figure 39: T-joint schemes
24
Figure 40: T-joint cross section
Figure 41: butt weld schemes
24
24
Figure 42: butt weld cross section
24
Figure 43: pump components
25
Figure 44: stainless steel container
25
Figure 45: clothing accessories
27
Figure 46: wood veneer
27
Figure 47: decoration on denim
Figure 48: embroidery cutting
28
28
Figure 49: graduated wear-effect on denim
29
Figure 50: composed pictures
29
Figure 51: marked golf with laser machining detail
29
Figure 52: holes in technical tissue
29
Figure 53: marked hearts on thick tissue
30
Figure 54: cut and marked accessories
Figure 55: textile marking lay-out
30
30
viii
Figure 56: embroidery with laser cutting
32
Figure 57: embroided item
Figure 58: embroided and laser cut item
32
32
Figure 59: printed, cut and applied patches
33
Figure 60: multicolour printed patch
33
Figure 61: 3D engraved crystals
34
Figure 62: 2D laser inspection equipment
35
ix
ACRONYMS
2D
3D
ABS
CAD
CAM
CNC
CO
CO2
CW
HAZ
HeNe
LAN
LASER
LCD
LIS
MAG
MIG
MPE
N2
Nd:YAG
OEM
PC
PET
PVC
QC
R&D
SME
STENT
TIB
TIG
UPS
xi ACRONYMS
Two dimensions
Three dimensions
Acrylonitrile butadiene styrene plastic
Computer Aided Design
Computer Aided Manufacturing
Computer Numerical Control
Carbon Monoxide
Carbon Dioxide
Continuous Wave
Heat affected zone
Helium Neon laser
Local Area Network
Light Amplification by Stimulated Emission of Radiation
Liquid crystal display
Laser Induced Super Plasticity
Metal Active Gas
Metal Inert Gas
Maximum Permissible Exposure
Nitrogen
Neodymium-doped Yttrium Aluminium Garnet
Original Equipment Manufacturers
Personal computer
Polyethylene terephthalate plastic
Polyvinyl Chloride plastic
Quality Control
Research and Development
Small and Medium Enterprise/s
A tube designed to be inserted into a vessel or passageway to
keep it open. E.g.: stents are inserted into narrowed coronary
arteries
German National Library of Science and Technology
(Technische
Informationsbibliothek
Universitätbibliothek
Hannover, http://www.tib.uni-hannover.de/en/)
Tungsten Inert Gas
Uninterruptible Power Supply
1
INTRODUCTION TO LASER TECHNOLOGIES
Innovation in manufacturing has a direct impact on the competitiveness of SMEs in terms of
costs, but it also may enable new product design that would be not be achievable with the use of
more conventional technologies. This is particularly true of laser technologies.
Following several decades of development and industrial use, lasers can now be considered to be
standard equipment, with wide commercial application and good reliability, comparable to other
tried and tested industrial machinery. The producers of industrial lasers provide guarantees for
their operation and specify standard maintenance programmes, which, in most cases, are less
demanding than are required for mechanical equipment.
The laser in a nutshell
Lasers are light sources. The concept is very versatile; they can emit
visible, infrared or ultraviolet spectra; they can generate long as well as
very short pulses (pulsed lasers), or very powerful steady beams
(continuous-wave, or CW, lasers), which are focused using simple
elements such as lenses or concave mirrors in small micrometre-size
spots, or to propagate nearly parallel beams extending for several
kilometres (collimated beams). They differ from a fire, the sun or an
ordinary light-bulb in terms of the intrinsic light generating mechanism
which radiates as a continuous repetition of spontaneous and disordered
processes, producing generally uniform illumination around them. The
generation of the light from lasers is by amplification of a well-ordered and
single-frequency seed, which produces a very directed emission, which is
single-coloured and coherent across the beam.
The core of the light amplifier is the gain medium, which may be based on
a gas, liquid or solid medium, chosen for its optical properties. The gain
medium transfers to the optical beam the energy received from the
external pump, the power supply. The amplification occurs within a
resonator, usually consisting of a pair of aligned mirrors, with parallel
surfaces, in which the seed grows through multiple passages through the
gain medium. The output beam slips off the resonator via one of the
mirrors which is semitransparent.
Figure 1 depicts the principal components of a laser:
1. Active laser medium;
2. Laser pumping energy;
3. High reflector;
4. Output coupler;
5. Laser beam
Figure 1: laser components
Clearly, there are more straightforward and affordable applications, such as cutting, marking, etc.,
which can be considered to be ‘frontier’ solutions but whose development will take some time for
1
them to be considered completely reliable. We have tried to select applications and technologies
that are simple and accessible for SMEs embarking on investment in laser technology, and to
highlight ongoing developments.
It should be remembered that as SMEs’ experience in using lasers accumulates, it will become
easier to introduce new technologies on the shop floor, progressing from simple laser operations,
such as marking, to cutting, and to more complex welding operations that facilitate the delivery of
new products or services.
The laser process has many similarities with other manufacturing processes, in which
relationships between customers and suppliers over design are very important.
Job shops or manufacturing facilities areas with short-time production planning, and product-line
manufacturers should choose their laser equipment taking account of the following points:
□ are there alternative, more economic technologies?
□ level of competence required for different processes (i.e. welding is normally more demanding
than cutting) and different materials (e.g. plastic or metal);
□ optimisation of operator time, especially in materials handling and tool change-out;
□ optimal choice of components: laser manufacturer, laser model and type of automation,
specific to the application;
□ availability of adequate infrastructure (gas, electricity, compressed air) and after-sales and
maintenance services;
□ capacity balancing in order to avoid high investments producing bottlenecks in other
production phases.
Laser cutting and marking can usually be achieved using standardised machines; welding
equipment is generally more specialised and needs adaptation to the customer’s application.
SMEs requiring customised equipment may be able to obtain a full-package system from the
OEM. Otherwise, they must use a systems integrator, i.e. a company that integrates standard
technologies in customised settings.
How lasers work
The laser beam interacts with materials in different ways depending on the type of
target, its absorption and composition, the laser colour or wavelength, and the
intensity of the laser beam.
The most common interactions are:
□ thermal: the laser light is absorbed and converted into heat. The local temperature
rises rapidly. Depending on the material this may induce melting, vaporisation,
combustion, degradation, surface hardening, etc.
□ photo-chemical: the light acts as a reagent and induces changes in the chemical
composition of the target material, or dissociation of molecules and disaggregation
of compounds.
□ nonlinear: the high intensity of the laser pulses induces local vaporisation or
defects in transparent materials, e.g. engraving on glass.
The industrial equipment has the characteristics and controls to allow precise
material removal (cutting, drilling, marking), joining (welding and soldering), and
different kinds of thermal surface modifications (hardening, alloying, cladding).
2
Laser market
Here we are interested in materials processing applications which use laser sources
that are different from the lasers used for telecommunication and optical storage
(e.g. optical fibre telecommunication, DVD-CD writers/readers, bar-code readers,
etc.). These latter are very low power, and cannot be used in manufacturing.
The global market for non-telecommunications lasers in 2007 was expected to
exceed US$6 billion, with a positive trend for volume and decreasing trend for prices.
The major industrial laser market players reported sales increases of 12%-18% in
2006 compared to 2005. Materials processing applications represent the vast
majority of these laser sales. Concerning types of lasers, the 2007 market share was:
solid state lamp-pumped, CO2 flowing, excimer, solid state diode-pumped, fibre, CO2sealed, other.
Laser types
Below is a list of lasers in general industrial applications.
□ Gas lasers: are the most widespread industrial lasers. They are based on a
gaseous gain medium, which is energised to produce the light amplification
through an electrical discharge. The most common application in this class is the
carbon dioxide, or CO2 laser, which is used for materials processing and has the
biggest market share, although other types (HeNe, Argon-ion, CO) are also
important. The CO2 laser emits infrared radiation at a wavelength of 10.6
micrometres, and can be produced from power outputs of a few tens of Watts (W)
to a few tens of kiloWatts (kW);
□ In solid state lasers: the gain medium is a doped crystal or glass, pumped by strong
flashlights or diode lasers. The most common type is the Nd:YAG laser, from the
Neodymium-doped yttrium aluminium garnet (YAG), whose wavelength is 1.06
micrometres, in the near-infrared, and is easily deliverable by fibre optic;
□ FibreFibre lasers: the gain medium is a piece of optical fibrefibre doped with
elements such as erbium or ytterbium. They require a diode laser as a pump,
injected into the gain medium. The infrared beam is of very good quality and their
output power has reached the kW range, and is naturally delivered by a fibrefibre.
This type of laser is the most recent development and is undergoing rapid growth.
□ Semiconductor – or diode – high-power lasers: these are very important sources in
the near infrared, which may reach kW output. They are based on telecom diode
laser technology, but are a thousand-fold more powerful while maintaining a 1
centimetre size. The beam is of lower quality than from other sources, and requires
advanced beam shaping optics to be launched in fibrefibres. Their initial and still
widespread use is for optical pumps in Nd:YAG lasers, as beneficial alternatives to
lamps. They are also used for low power applications, such as miniature welding,
for thermal treatment of metals using large spots which direct more sources,
reaching multi-kWs, and for welding plastics.
□ Chemical lasers: are powered by chemical reaction. Examples are hydrogen
fluoride or deuterium fluoride; they are only used where there is no electricity
available.
□ Excimer lasers: are very intense sources of ultraviolet light, used in medicine and
lithography, and are based on a gaseous gain medium strongly pumped by an
electron beam.
3
2
SAFETY AND ENVIRONMENTAL PROTECTION
Safety cannot be emphasised too much. Users of laser technologies must be aware of two main
issues for which solutions are widely available: the risks to operators’ eyes and skin, and the
emissions, which can affect the environment and threaten the health of operators.
In terms of protection, SMEs must take account of the following issues in order to introduce
safety procedures to protect personnel and the environment:
□ Laser class: this is clearly specified in the equipment documentation (brochure, manuals) and
on the equipment itself and is classified according to the international laser safety standard
IEC 60825-1. The classification can range from I the safest, to IV the most hazardous. A
description of these classifications is included at the end of this chapter.
□ Eyewear and wavelength: Operators must wear protective eyewear - ‘laser goggles’ - according
to the wavelength and laser class. Guidelines can be found in the national standards system or
in the European norm EN207 and EN208 or US norms ANSI Z136.1-2-3-5-6
(http://www.laserinstitute.org/store/ANSI/106A). Even exposure to relatively low power lasers
can be dangerous. Near-infrared laser radiation of 400-1,400nm wavelength may cause
heating of the retina, cataracts or burn injuries, which can occur without pain to the operator or
any immediate effect on sight. (A popping or clicking noise from the eyeball indicates retinal
damage, which could result in permanent blind spots).
□ Skin burns: exposure to high power beams at any wavelength can result in skin burns. Although
recovery will be complete, there will be short term pain and discomfort. Focused beams can
cause burns, and deep cauterised or bleeding holes or cuts.
□ Air contaminants: suitable capture devices must be installed to reduce the health and
environmental hazards from laser processing. Devices such as table exhaust systems, working
head integrated systems, total enclosures, and filters can be provided by the OEM or found on
the market. Due to their thermal character and the variety of applications and materials (metal,
wood, plastic, and others), laser processing can emit a complexity of air contaminants that may
be malodorous and have serious side effects for humans as 40%-60% of these contaminants
settle in the alveoli of the lungs. Certain plastics (PVC, PET, ABS, etc.) applications generate
dioxins; wood can generate flammable components and dust; chrome tanned crusts can
disperse heavy metal particles; and metals can generate metallic particles. The highest
emission rates are associated with laser cutting (>100mg/s); these levels may be 10 to 100
times lower for material removal or marking. Proper fume exhaustion devices must be installed
in production units.
□ Proper working conditions: laser operators must be ensured safe and comfortable working
conditions, and especially those working on higher classes of lasers or portable laser
equipment. This may include proper enclosures, wavelength specific eyewear, protective
clothing, safety interlocks, properly displayed safety information on laser radiation, warning
lights, plans of the laser sources in the building or area, in addition to standard operating
procedures and suitable education and training. Such precautions will enhance both safety and
productivity.
4
Exporting lasers
Although commercial laser systems are usually licensed, there are also
export controls to which lasers are subject, which limit the shipment of
products with potential military application, from Wassenar1 to nonWassenar countries. Initial developments in lasers were and still are
connected to weaponry. Their control is based on quantifiable parameters
such as power, wavelength, and overall efficiency and distinguishes
between lasers that can be freely exported and lasers that can only be
exported under licence, which include continuous wave CW, pulsed, and
tuneable lasers.
1
The participating Wassenar countries are: Argentina, Australia, Austria, Belgium,
Bulgaria, Canada, Croatia, Czech Republic, Denmark, Estonia, Finland, France, Germany,
Greece, Hungary, Ireland, Italy, Japan, Latvia, Lithuania, Luxembourg, Malta,
Netherlands, New Zealand, Norway, Poland, Portugal, Republic of Korea, Romania,
Russian Federation, Slovakia, Slovenia, South Africa, Spain, Sweden, Switzerland, Turkey,
Ukraine, United Kingdom, United States of America. Information is available at the
Wassenaar Arrangement website http://www.wassenaar.org/
Figure 2: Potential harms from
portable devices
Figure 3: Laser on welding glove
Figure 5: Finger injury at time of
the accident, after 10 days, after
21 days
Figure 4: Burn from partial 2kW
CO2 laser reflection
5
LASER CLASSES
(from Wikipedia: http://en.wikipedia.org/wiki/Laser_safety):
class I
A class 1 laser is safe for use under all reasonably-anticipated
conditions of use; in other words, it is not expected that the maximum
permissible exposure (MPE) can be exceeded. This class may include
lasers of a higher class whose beams are confined within a suitable
enclosure so that access to laser radiation is physically prevented.
class IM
Class 1M lasers produce large-diameter beams, or beams that are
divergent. The MPE for a Class 1M laser cannot normally be exceeded
unless focusing or imaging optics are used to narrow the beam. If the
beam is refocused, the hazard of Class 1M lasers may be increased and
the product class may be changed.
class II
A Class 2 laser emits in the visible region. It is presumed that the blink
reflex will be sufficient to prevent damaging exposure, although
intentional, prolonged viewing may be dangerous.
class IIM
A Class IIM laser emits in the visible region in the form of a large
diameter or divergent beam. It is presumed that the human blink reflex
will be sufficient to prevent damaging exposure, but if the beam is
focused, damaging levels of radiation may be reached and may lead to
a reclassification of the laser.
class IIIR
A Class 3R laser is a continuous wave laser which may produce up to
five times the emission limit for Class 1 or class 2 lasers. Although the
MPE can be exceeded, the risk of injury is low. The laser can produce
no more than 5 mW in the visible region.
class IIIB
A class 3B laser produces light of intensity such that the MPE for eye
exposure may be exceeded and direct viewing of the beam is
potentially serious. Diffuse reflections (i.e., that which is scattered
from a diffusing surface) should not be hazardous. CW emission from
such lasers at wavelengths above 315 nm must not exceed 0.5 watts.
class IV
Class 4 lasers are of high power (typically more than 500 mW if CW,
or 10 J/cm² if pulsed). These are hazardous to view at all times, may
cause devastating and permanent eye damage, may have sufficient
energy to ignite materials, and may cause significant skin damage.
Exposure of the eye or skin to both the direct laser beam and to
scattered beams, even those produced by reflection from diffusing
surfaces, must be avoided at all times. In addition, they may pose a fire
risk and may generate hazardous fumes.
6
3
3.1
METAL PRODUCTS
CUTTING
OVERVIEW
Laser cutting is the cutting of solid materials using a focused laser beam. It is by far the most
common application of industrial laser technologies and also one of the most standardised. The
materials to which it can be applied include mild steel, stainless steel, aluminium, alloy metals,
reflective metals such as copper and brass, glass, plastic, leather, wood, and in a wide range of
thicknesses. Most materials can be cut by a laser.
Laser cutting represents a step forward in product design, and especially in relation to the value
that is added to products requiring complex profiles or holes. In these cases, laser use is
profitable even for small production runs. The characteristics of commercial lasers make them
very flexible: no tooling, no mechanical contact, little inertia, very small cut width and restricted
thermally-affected zone, wide range of thicknesses of good finishing cutting, user friendly CNC
(computer numeric control) programming and interface to CAD (computer aided design), minimal
maintenance. However, the full benefits of their exploitation can only be achieved through
experience in use and the integration of design and manufacturing, i.e. design synergy between
client and supplier.
In the case of sheet metalworking, laser systems often substitute for the more conventional
guillotine shears and punching machines and avoid the use of ad-hoc tooling for curved profiles.
Lasers can cut down on 90% or more of a job-shop production. However, the entrepreneur must
be certain that working and safety conditions are met (see chapter Plant and Equipment), and
that adequate servicing facilities are available in the area and should ensure whether the product
could be produced more economically with other technologies such as ad hoc dies in automatic
machines in the case of long runs, or oxygen lance or plasma cuts in the case of less
complicated/lower finish work.
Reliable technologies (CO2 was introduced in the 1960s, Nd:YAG in the 1970s), programmable
logics, CAD/CAM nesting, adaptive diagnostic systems that monitor the region affected by the
laser beam, and automation, extend and ease the cutting jobs undertaken by SMEs, which can
exploit the system on a three-shift/day basis, 6,000 hours/year, will not be dependent on the
constant presence of an operator or on highly skilled operators to obtain the desired flexibility,
cutting profiles and quality made viable by the use of lasers.
The cut can be executed in two dimensions (2D), for instance on metal sheets, or in three
dimensions (3D) in the case of components that need to be cut in width, length and height such
as tubes.
CUTTING
7
Figure 6: 2D cut on stainless
steel sheet
Figure 7: 3D cut on tube
In principle, lasers can cut any complicated profile and a range of organic and inorganic
materials, which makes them one of the most flexible manufacturing technologies available, and
has brought a shift in product design.
SME operators usually consider laser applications to be most appropriate for high value-added
products, i.e. materials whose profiles and finishes justify investment in an expensive, though
reliable, technology. SMEs tend to purchase the highest power generation available in the market.
Many invest in an additional laser machine before the end of the cycle of depreciation of an
existing one to enable specialisation by material.
Depending on the application, SMEs can find commercial equipment with three to four axes
movements for 2D cutting or five to six axes for 3D cutting, whose beams can be delivered by
robot systems in the case of fibre lasers and also CO2 systems with more complex optic systems
which are normally only justified in high value added and capital intensive plants. Motion can be
via flying optics, sliding worktables or a hybrid solution.
Different materials may require different technologies:
□ CO2 lasers are especially indicated for mild steel, stainless steel, iron, nickel, tin, lead, PVC,
epoxy, leather, wood, rubber, wool, cotton, acrylics, polyethylene, polycarbonate. In spite of
their vast range of applications based on beam quality, low cost, and reliability, CO2 lasers
cannot be delivered by fibre optics because of their wavelength, They are thus not easily
manipulated by robots;
□ Nd:YAG lasers, whether lamp or diode pumped, are indicated for aluminium, copper, brass,
platinum, gold, silver, hastelloy, silicon nitrides, aluminium oxides, boron nitrides,
polycrystalline diamond, pyrographite, titanium, tantalum, zirconium, molybdenum, tungsten,
chrome, glass, quartz, asbestos, mica, and natural stones. Because of its wavelength, the
Nd:YAG laser can be transmitted through fibre optic and is suitable for robotic manipulation;
□ Ytterbium fibre lasers are another technology that has recently come onto the market. Their
current high price is counterbalanced by their greater efficiency (up to 30% at the time of the
publication), higher output power (commercial models up to 10kW or even scalable to 50 kW,
vs 4kW-6kW of CO2 and Nd:YAG), very high beam quality, simpler cooling (tap water), longer
pumping diode duration (25,000 vs 10,000 hours) and consequent lower maintenance costs,
which result in lower per hour operating costs, greater portability and novel application.
Ytterbium fibre lasers can be used to cut mild steel, stainless steel, titanium alloy, aluminium
alloy, galvanised steel, nitinol, inconel, and plastics.
□ Disc lasers are another recent technology, which has the same cutting applications as Nd:YAG,
but at higher power densities and wall-plug efficiency (15% at the time of the publication), thus
enabling faster and deeper cutting.
In 2006, the fibre and disc lasers had a +45% sales trend world wide compared to 1%-5% of the
more traditional CO2 and Nd:YAG, although the volume of sales of these latter two is 14 times
higher. The diffusion of fibre and disc lasers may erode the market shares of the more
‘conventional’ laser technologies as investment and running costs (especially linked to diode
8
CUTTING
duration and maintenance) decrease and facilities costs in the industrial environment come
down.
PLANT AND EQUIPMENT
Laser cutting equipment requires a series of working conditions to be fulfilled in order to maintain
reliability. In the reference case of a world standard 3.2kW CO2 machine cutting 3,000mm x
1,500mm sheets up to 20mm in mild steel, 12mm in stainless steel or 8mm in aluminium, the
following conditions would apply:
□ Electricity should be stable at 400V ± 10V nominal. Power consumption ranges between 27kW
and 53kW and the electric installations should bear 85kVA. In case of low stability,
interruptions or shading, the entrepreneur should consult with the laser OEM about whether it
is reasonable to use stabilisers, continuity groups, generators and/or switches from the grid to
preserve the equipment. In fact, interruptions may cause higher scrapes because of quality
problems and equipment damage.
□ Pure lasing and cutting gases should be available in adequate quantities, certified and
reasonably priced. Lasing gases could be delivered in batches of several cylinders while cutting
gases could be stocked in large pressure tanks (e.g. 5,000 litres) either owned or leased.
Impure gases or lack of gases can greatly reduce cutting speeds and maximum thicknesses. In
the case of high power CO2 cutting the following purity specifications apply:
GAS
GRADE
PURITY
CO2
4.8
99.998%
N2
5.0
99.9990%
He
4.6
99.996%
O2
3.5
99.95%
□ Compressed air, substituting N2, should be of hospital quality purity. Lubricant polluted
compressed air could damage equipment;
□ Cooling water should be demineralised with conductivity lower then 10-5 μsiemens/cm for CO2
lasers (fibre lasers require tap water). Higher cooling options may be selected in the case of
tropical temperatures;
□ Although a deep basement is not required, a flat stable base is required to maintain the
calibration positioning. For reference, calculate an approximate applied force of 27,000N for
the machine and 7,000N for the loading automation; additional criteria apply in the case of
faster equipment (e.g. with linear motors);
□ Adequate working space should be assigned to loading operations, off-loading, safety light
barriers and materials handling. For reference: with the exception of materials handling
runways, the surface required should be approximately 9m x 11m or, if a loading automation is
installed, 11 m x 13 m;
□ Safety devices for the protection of operators and the environment. Photovoltaic (PV) barriers
to prevent accidents are normally provided with the equipment; exhaust and dust filtration
must be carefully selected because the dust particles from these operations can be inhaled;
□ A personal computer (PC) and nesting/programming software are recommended to enable
process optimisation and cost reduction. Appropriate production planning, mixing of different
orders, and nesting software can reduce scrape material to less than 10% resulting in
significant cost reductions.
CUTTING
9
Figure 8: Reduced scrape
The investment required for a cutting system depends on the type of technology, equipment
standardisation, and automation. In addition, the entrepreneur should evaluate the Incoterms
and plant costs involved in housing this equipment, which will vary from country to country. At the
time of the writing, as a rule of thumb, a maximum of €500,000 would be needed for a mediumhigh cutting station: €300,000 for the complete cutting system based on a 3.2kW CO2 laser
source (for 3,000mm x 1,500mm plates), €20,000 for programming and nesting software and
€120,000 for loading automations if requested. Laser cutting SMEs tend to purchase the highest
power generation available in the market; however, such equipment may have higher costs (for
reference the most recent 6kW CO2 equipment and loading automation at 2008 prices costs
approximately €1 million), which enable state-of-the-art performance provided the appropriate
working environment, experience and maintenance are available. In principle, it is not necessary
to have the highest power and SMEs should evaluate the level of power appropriate to their
projected production.
For CO2-cutting running costs, commercial OEMs can estimate for customers the cost of different
applications (materials, thicknesses). The following are provided as a guide but will vary from
country to country and will also depend on the duty cycle:1
□ Electricity: an average of 70-80kW per machine in real terms;
□ Gas: lasing and cutting gases are supplied by a limited number of companies, and prices are
volatile. A rough estimate of lasing gas consumption may be in the range 1, 6, and 13
litres/hour respectively for CO2, nitrogen and helium, and 500-2,000 litres/hour for cutting
gases (CO2, nitrogen) in high power systems; mid- and low-power lasers may have a much lower
or even no consumption, as in the case of sealed tube lasers, available up to about 500W.
□ Maintenance: laser equipment tends to be reliable; however, good maintenance maintains
competitiveness because down-time and spare-parts are expensive. In the case of CO2
equipment, the entrepreneur may budget 1 day/month for preventive maintenance and, in
Europe, €10,000-25,000 in consumables and manpower/year, proportional to machine
performance. Items that need maintenance are filters, lenses (once or twice a year if the
machine is used properly), final stage valves, and telescopic covers in the case of faster
machines. Cut thicknesses and performances progressively decrease with longer maintenance
intervals.
□ Personnel for up/off-loading and programming;
□ Depreciation: depending on the allowed rates;
□ Compressed air
□ Raw materials (if applicable).
1
i.e. the time of laser-on, which may vary from 15-80%, and the hours of operation, normally 2,000-4,000 hours,
but could reach 6,000 hours, based on 20 hours/day, 5 days/week, and 10 hours/day 1 day/week on a 12 month
basis.
10 CUTTING
CUTTING EXPERIENCES
This chapter describes the products and plants from three family-owned job-shops with short or
very short production planning (4-30 days): small products frequently used for jewellery, stainless
steel components for equipment fabrication, and thick mild steel for buildings and equipment.
3.1.1
SMALL JEWELLERY AND DECORATIVE COMPONENTS
A 15-employee company registered in 2000 operates a 1,400m2 plant with two CO2 laser cutting
machines and a 100W Nd:YAG diode pumped laser marking machine, to produce flat
components for jewellery, decorative items and food equipment, with a production planning time
of up to 4 days.
The cutting machines have 2kW and 3kW output power and are generally used respectively to cut
3,000mm x 1,500mm and 4,000mm x 2,000mm stainless steel plates normally in 2mm
thickness, and less frequently because of market specialisation, exotic materials or thicknesses
up to 20mm.
The laser permits flexibility in terms of profiles, speed and quality, unachievable with traditional
technologies. Accurate selection of cutting speed allows adequate finishing, possibly avoiding
further grinding, brushing or polishing of the cut surfaces.
Figure 9: Laser cut pendants for
jewellery (on the right)
Figure 10: small size laser cut
components
After cutting, many items are marked with the Nd:YAG machine, which has a four-position
indexing table, to add further features or traceability.
Figure 11: Laser cut and engraved component
Of the 15 employees, 9 are involved in production and 6 cover the engineering, commercial and
administrative functions. The cutting laser operator, the marking operator and the programmer
have job-shop and technological expertise. They have attended OEM courses on safety and
machine working and inhouse courses on production organisation. No formal engineering
education is required for their jobs.
CUTTING
11
Figure 12 depicts the job-shop lay-out:
Raw material (metal sheets) warehouse
Finished
products
area
3,000mm x 1,500mm
2kW laser cutting
machine including
auxiliaries and safety
devices
Up and off loading
automation
4,000mm x 2,000mm laser
3kW cutting machine and
auxiliaries, including safety
devices
Door
Way out
Marking
machine
Offices and services
Offices and services
Figure 12: Lay out with two cutting machines
3.1.2
PARTS FOR LIGHT INDUSTRIAL EQUIPMENT
The production of metal components for light industrial equipment manufacturers is the daily
activity of a 20 employee SME that operates four different pieces of CO2 laser equipment cutting
3,000mm x 1,500mm plates, in addition to other traditional sheet metalworking machines and
welding workstations.
The long tradition in the sector began in the late 1960s based on punching machines and
guillotine shears, then CNC systems and, in 1989, the first laser cutting equipment. The
experience and the product specifications steered the company to specialise their laser
equipment according to materials and thicknesses. This required 30 day work plans. The
company uses the laser equipment only 2,200 hours/year per station, and operates 1 shift/day.
Being a supplier of OEM sub components, the SME stresses that a form of co-design between
client and supplier or mutual education to design for laser manufacturing is necessary in order for
the product to exploit the potentialities of the technology.
The products consist of cut, bent and welded metal sheets in mild steel up to 25mm, in stainless
steel to a maximum thickness of 15mm, in aluminium at 6mm, and in brass at 4mm, ready to
paint. Cutting is also done on bent components; machining is outsourced. Laser machines cut an
average 90% of all processed material, whether laser intensive, such as small parts, or materials
intensive such as thick plates, while the remaining rectilinear profiles are cut by CNC punching
machines.
12 CUTTING
Figure 13: laser cut stainless
steel samples
Figure 14: laser cut item
The company has always purchased the latest and most powerful CO2 models, in order to achieve
the highest speeds, thicknesses and flexibility and, at the time of the interviews, operated a
2.6kW, a 3kW, a 4kW and a 5kW machine, this last connected to an automated warehouse and
loading system. The possibility for using different equipment in parallel enables knowledge to be
accumulated in different materials and processes.
Because of the high volume of material being processed and the intensiveness of laser cutting,
the company utilises cylinders for lasing gases, packs of cylinders for cutting CO2 and a 5,000
litre nitrogen tank for cutting, all these costs being included in the laser evaluation.
Figure 15: lasing gas cylinders
Figure 16: cutting gas storage
The company relies on two high-school qualified mechanical technicians for nesting, programming
and minor problem solving and on four specialised workers for up/off-loading, programme recall,
and minor calibration procedures.
CUTTING
13
Figure 17 depicts the job-shop lay-out:
6
1
2
Semi-finished
warehouse for
bending
raw material
(metal sheets)
warehouse
Legend:
1.
2.
3.
4.
5.
6.
3.1.3
3
4
5
Punching, shears
equipments and sheet
metal warehouse
waterjet
Welding
workstations
and welding
robot
Stainless steel bending
equipments and sheet metal
warehouse
Offices
Finished
products
warehouse
Finished
products
warehouse
2.6kW
3kW
Automated warehouse
5kW
4kW
N2 storage
CUTTING FOR FABRICATION
This is a 17-employee job-shop with experience gained over 10 years, from operating three laser
machines, which uses a single standard 3kW CO2 machine to cut 90% of the metal needed to
feed conventional bending and welding workstations. Production focuses on mild steel and
stainless steel which is transformed from raw plates into components for equipment ranging from
industrial washing to injection moulding, naval interior wall panels and other shaped profiles. The
company cuts some 15 tons of metal/month and is now operating on a 15-day schedule
compared to the previous 60-day schedule because global supply chains have steered the
production towards less repeatable, more complicated, higher value added components with
stretched lead times.
The introduction of laser technology followed the use of more traditional guillotine shears and
squares and brought a change in design for manufacturing, to exploit the potential of lasers for
new product design.
Mild steel is cut in thicknesses of between 0.8mm and 20mm while stainless steel plates range
from 0.8mm up to 12mm. Key issues for the company are machine reliability and finishing, which
is inversely proportional to cutting speeds. As a reference, the complete cycle for a profiled plate
700mm x 350mm x 6mm, such as that depicted in Figure 19: laser cut profile in mild steel for
fabrication, is approximately 2 minutes.
14 CUTTING
Figure 18: fabricated frame from laser Figure 19: laser cut profile in mild steel
for fabrication
cut components
The company has four managers responsible for commercial deals, purchasing, production
planning and control, an administration staff, six welders, four punch and shearing machine
operators, and three laser operators. The work division is flexible to enable the company to cope
with several assignments.
The laser staff includes a designer responsible for nesting, programming and bills of materials, a
laser-machine operator who monitors programmes and production, and an off-loading operator
assisted by automated up-loading which extends lasing-times to more than 10 hours per day. The
laser team has extensive job-shop experience, familiarity with and interest in technology, and has
been trained in a one-week OEM course; none of the team has any formal engineering education.
Figure 21 depicts the various machines in the 2.000 m2 plant:
Bars and profiles
warehouse
bending
shears
bending
bending
punching
QC control and finished products
warehouse
bending
Welding workstations
Semifinished
deposit
for shears
3
2
1
Laser items:
1. Up-loading
automation;
2. CO2 laser
cutting
machine;
3. Off-loading
area and cutitem buffer
Metal sheet
warehouse
Figure 20: Fabrication job-shop lay-out
CUTTING
15
3.2
MARKING
OVERVIEW
Laser marking is a relatively low cost operation. It is used to permanently inscribe on the surfaces
of materials, graphic information, such as bar codes, alphanumerical tags, indicator lines in
gauges, drawings, etc., using a laser beam. Its use to allow product traceability or provide
information is growing. Laser marking can be a substitute for mechanical embossing, engraving,
or printing processes.
Laser marking permanently modifies the surface of a material. The laser emits short pulses (10200 nanoseconds) which make a disturbance (a single spot) on the surface that is visible when
illuminated. A single spot is of small diameter, in the range 30-500 micrometers, and can become
the element of a letter, a drawing or a graphic. The repetition of laser pulses is quite high, 10-100
kHz, and the position of the mark is directed by a pair of mirrors actuated by a computer
controlled driver.
In standard applications, the material surface is ablated by the laser beam when it reaches an
energy density above the ablation threshold of the material: a small volume of the material is
removed in vaporised state. A repetition of laser irradiation on a single spot results in a
progressive engraving.
Photochemically induced marking involves a permanent colour change, obtained by exceeding
the degradation threshold temperature; the process is quieter and produces fewer pollutants.
However, ablation is normally faster and deeper than photochemical induced marking.
It is possible to utilise different types of marking lasers depending on the materials and the
marking rate required. Solid state laser, such as Nd:YAG lasers, are best for marking metals and
dark plastics, CO2 systems can be used to mark ceramics, transparent and organic materials. In
the case of Nd:YAG lasers, a pump source using diode-laser or flash-lamp is required, depending
on the power. The diode-pumping technology, which is a more recent technology, involves smaller
equipment, lower maintenance costs, smaller power requirements, and less complicated cooling
(air instead of water), but is usually limited to use with sources of about 20W of output power.
CO2 lasers differ in terms of spot sizes which are larger. They are recommended for a variety of
relatively soft materials such as wood and plastic.
Marking speeds are proportionally slower when higher resolution is needed, and depending on
the characteristics of the material being engraved. The OEM or resellers can advise on which
equipment is best for each application.
16
MARKING
PERSONNEL AND EQUIPMENT
Usually one person can operate and program a laser marking system. This individual would need
some background in shop operations and some capabilities in the use of CNC systems. OEMs
normally provide programming and safety training as a package with the marking system.
Alternatively, an engineer could program the marking instructions and production staff could
operate the equipment following the instructions provided.
Depending on the manufacturer and the model, laser marking machines can process items
weighing up to 100kg, and up to 1,000mm x 400mm x 750mm in dimension, which would cover
a range of products including items of jewellery to bigger metal items or a series of smaller items
properly aligned on a pallet.
Figure 21: marked metal coloured
component
Figure 22: marked metal component
Depending on production needs, the marking laser can be integrated into an automated
processing line in the case of high volume applications, or can be a standalone workstation. A
standalone laser marking machine is quite small; a standard model requires a space of
approximately 1,000mm x 1,000mm÷1,500 mm x 2,000 mm (height) and foundations capable
of bearing 500kg weight or 800kg for larger three-phase equipment.
Figure 23: Detailed picture marked on
plate
In order to optimise operations, the system should be connected to a fume exhauster and filtering
device in compliance with the safety regulations and positioned in an easy-to-load place with
accessible and well organised feeding and stocking facilities.
The marking process is programmable via user-friendly software and can be controlled either
locally by the operator or remotely by an engineer across the company LAN.
The most common two-phase systems consume less then 2kW power and deliver beam power
ranging from 5W to 150W; three phase systems may require up to 5kW.
In terms of investment, a mid size, standalone marking system could be in the range €50,000100,000 including the software and operator training in programming, use and safety, from a
variety of marking system manufacturers. Companies also need to consider investment in a
MARKING
17
vacuum system, modifications to shop floor lay-out to house the new operation and perhaps
installation of a local area network (LAN) in the job-shop.
Running costs will include maintenance (mainly filter cleaning, according to the load, and
minimum annual laser maintenance), electricity costs, equipment depreciation and the cost of
the loan (if any) for purchasing the system. Not all SMEs have a cost-accounting administration,
and most estimate hourly costs with margins to cover all the above items.
A ballpark laser marking costing might be:
€88,300 +
Hypothetical equipment price including software
and training
€11,700 =
Interests (with a 5 years loan at 5% interest rate)
€100,000 /
Total equipment cost
5 years /
Years of depreciation
€20,000 +
€2,000 /
2,000 hours =
€11
Yearly cost of asset
Yearly quote of pumping diode substitution
(€10,000, 12.000 working hours, 2,400 working
hours/year)
One operator’s yearly working time
Equipment cost
In addition to this, the entrepreneur should consider the following
(depending on the Country) +
(depending on the OEM +
and the metals)
(depending on the Country =
and the Company)
Total €/hour
3.2.1
Electricity cost
Maintenance cost
Overhead costs
Reference hourly cost used in budget calculations
MARKING – A CASE STUDY
In the case analysed, the production of components for the petro-chemical industry requires laser
marking before assembly. The case study company is part of a large diversified group that
produces industrial hoses and machined components and employs 22 highly qualified people.
Operations include order processing, production planning and engineering and purchasing; most
of the company’s employees are engaged in the manufacturing and assembly areas, where the
marking system is installed.
There are seven product lines (valves and manifolds, pressure pneumatic transmitters,
pneumatic/electronic level transmitters, air filter regulators and vibration switches) and more
than 500 models in a list of about 5,000 components composed of stainless steel or exotic
materials, such as titanium, hastelloy, incalloy 825, inconel 625, monel 400 and others, which
are finally sold in the international market.
Figure 24: Marked
instrument manifold
18
MARKING
The marking operation involves a small percentage (5%) of the production, and is used to provide
traceability of components or to display information permanently.
A diode pumped Nd:YAG 2kW machine is operated by a trained worker 8-10 hours/day, 6
days/week. This operator and two other workers run the whole quality control (QC)-testing,
marking, assembly and shipment processes. Marking requires loading of up to six aligned items
and then pushing the start button, which automatically closes a sliding door which is a safety
feature. Processing takes between 6-10 seconds per item for photochemical marking and a
further 2-3 seconds for the engraving cycle after which the items are offloaded. The marking
process could be made more sophisticated by the addition of automated warehouse, materials
handling, loading and off-loading systems.
QC test benches
QC test benches
Assembly, packaging and shipment area
Marking laser
Storage of marked components before
Components ready for marking
Components ready for marking
Components ready for QC
Components ready for QC
Vacuum and filtering unit
Figure 25: Marking lay-out sketch
MARKING
19
3.3
MANUAL LASER REFURBISHMENT OF DIES AND MOULDS
OVERVIEW
Cracked moulds can cause problems in plastic injection moulding or metal die casting plants.
They can be repaired using traditional welding technologies, such as Tungsten Inert Gas (TIG), or
by deposit welding using by Nd:YAG lasers2 with a narrow filler wire; these repairs can be
accomplished in-house or outsourced to job-shops. Laser and TIG can be considered to be
complementary because of their different performance and hourly costs, which are higher for
laser due to the higher initial investment, but have some benefits over TIG. For example:
□ they do not require the mould/die to be heated before welding, which shortens the processing
cycle;
□ the heat affected zone (HAZ) is reduced because the sublimation and the cooling speeds are
high;
□ it is possible to weld in confined spaces (cavities, interfering contours);
□ the post processing finishing takes less time due to the laser’s finer welds.
THE PRODUCT
Laser deposit welding can be used to repair polymer injection moulds, pressure dies, punching
and cutting tools, forging dies and blowing mould tools.
Figure 26: welded item
Figure 27: repaired mould
Figure 29: cross section of filler deposit
Figure 28: welding in an inside edge
Commercial systems can handle base materials of up to 64 Rockwell Hardness (HRC) and
dimensions of 200mm x 200mm x 200mm to 500mm in length if the class I shields are open,
which provides a much bigger working area (class IV). In the case of bigger work-pieces (e.g.
1,700mm x 1,800mm), it is possible to purchase a laser system comprising the laser source, a
basement, a three axes mechanics and a laser head with no protective enclosure. In working
areas (class IV), operators are required to wear laser-specific eye protection (goggles) suited to
the wavelength applying; no other personnel should be within the radius of the laser beam
dispersion. Moulds for class I machines can exceed 300kg.
2
A video of mould reparation can be found at
http://www.sitec.lecco.polimi.it/SitoSITEC_IT/video/powerweldHQ.htm
20 MANUAL LASER REFURBISHMENT OF DIES AND MOULDS
EQUIPMENT AND PERSONNEL
Welding equipment used to repair moulds and dies is normally manual, using Nd:YAG laser
sources of approximately 80-120W average output. Depending on the mould dimension, the
shop-floor may decide to use class I systems with enclosures for small items, or class IV systems
without enclosures for bigger items. In the latter case the operator must wear laser goggles
suitable for Nd:YAG wavelengths of 1.064nm. Manual welding without filler wire can also be
operated.
Figure 30: class I laser manual
welder with open doors
Figure 31: mould repair with a
class IV manual laser welder
Operators would normally sit: in front of the enclosed work table or piece, inspecting the welding
area through a LCD screen or a magnifier, and controlling operations with a joystick. The operator
can command a motorised focus adjustment, a temporal pulse-shaping to induce post welding
annealing or can store a particular contour for repeat use (repeatability in standard 2D actuators
may be as low as 20μm). CAD drawings can be loaded in a variety of formats from those
developed for CNC. Due to the possibility to use very thin filler wires (ø 100μm÷400μm) and to
the laser weld characteristics, post processing takes much less than with TIG.
In terms of the plant conditions required to host the welding equipment, equipment with full
enclosure, in safety class I, would occupy approximately 1,000mm x 1,000mm x 2,000mm and
weigh in excess of 200kg. A larger station that is open and in safety class IV, would require at
least 1,000mm x 2,000mm x 2,000mm and a load bearing base capable of 400kg plus the
weight of the workpiece. Normally this equipment uses a three-phase energy supply at 400V with
a recommended continuity group, and requires a deionised water cooling loop for the laser
source.
For the applications described above, the welding station should be installed on a ground floor.
Insulation from vibration, for example, from traffic, railways, etc. is important; any strong vibration
could affect the precision of the process.
New manual laser welders that can be used for mould repairs cost in the range of €30,00080,000 at the time of the interviews. Among the running costs the main items are related to
power use (about 1.6kW for a medium station), maintenance and filler wire - estimated at
€1/hour and €200 for a 50m wire with ø0,8mm÷1.2mm, respectively). The main consumables
include laser-pumping lamps (€250/500÷1,000 hours) and replacement deionised water filters
(at least once a year) (€200), to ensure maximum conductivity of 10-5 μsiemens/cm.
The benefits related to production using laser and TIG versus the different costs of the two
technologies will need to be weighed. A TIG workstation costs about €5,000 and has an hourly
cost of €10 compared to €50 for laser. On the other hand, the laser processing is crucial in the
case of delicate or precise welding: it enables much higher precision, much smaller thermal
affected zone, and cheaper finishing costs. Moreover, small or complex weld positions are
impossible to reach using TIG.
Laser welding requires a certain level of process and metallurgic competence; therefore, it is
recommended that operators have some welding experience.
MANUAL LASER REFURBISHMENT OF DIES AND MOULDS
21
3.4
LASER WELDING PROCESS
Section 2.3 described a laser welding application that is believed to be particularly suitable for
SMEs because of its relatively low level of complexity and capital requirements.
Laser welding is a relatively new process, and it is usually capital-intensive industries that use its
high power applications. In processes based on fusion, lasers supply sufficient heat to melt the
material, and subsequent solidification creates the joint. The melt material could comprise the
two parts to be joined (joint welding) or a filler wire (deposit welding).
The amount of heat that is brought to the welding area has to be higher than the heat that is
dissipated, which depends on the reflection coefficient of the material(s) and the laser
wavelength. The transmission of heat inside the material is based on an effect known as keyhole.
In keyhole welding, a high power density >106 W/cm2 produces metal plasma in the material,
which enhances heat absorption and penetration. If there is insufficient power, the keyhole is not
generated, heat is transferred by conduction only, and penetration does not occur.
Lasers generate two types of plasma:
• metal vapour plasma, useful if it is inside the
keyhole, harmful if it is above the material
because it absorbs power;
• gas ionization plasma above the material,
harmful because it absorbs power.
These plasmas can be eliminated by a flow of
blown gas during the process. This gas can be
inert or capable of high-ionisation and serves two
purposes: it covers and protects the melt pool and
removes the plasma.
Figure 32: Reflection coefficient,
wavelength, materials
The parameters (see Figure 36: influence factors)
that must be considered in relation to laser
welding are:
• laser power, which determines the penetration depth and the welding speed (see Figure 33:
temperature and welding section);
• welding speed, which determines the penetration depth (see Figure 35: speed, power and
penetration);
22 LASER WELDING PROCESS
• type and flow of protection gas, which influence the quantity of plasma, the power required for
the process, the penetration depth and the welding speed;
• focal point position, which determines the distribution of power in the material, the penetration
depth, the joint width and the welding speed.
Figure 33: temperature and welding section
Figure 34: plasma generation
Figure 35: speed, power and penetration
Figure 36: influence factors
The most common types of joints accomplished by laser welding are:
• lap seam (see Figure 37: lap seam welding and Figure 38: lap welding cross section),
• butt welding (see Figure 39: T-joint schemes and Figure 40: T-joint cross section),
• T butt (see Figure 41: butt weld schemes and Figure 42: butt weld cross section).
LASER WELDING PROCESS
23
Figure 37: lap seam welding scheme
Figure 39: T-joint schemes
Figure 41: butt weld schemes
Figure 38: lap welding cross section
Figure 40: T-joint cross section
Figure 42: butt weld cross section
ADVANTAGES AND DISADVANTAGES OF LASER WELDING
The main advantages of laser welding are high penetration and speed, reduced HAZ and high
precision and good final quality. On the other hand there are disadvantages, such as the need for
complex and precise equipment, complex and expensive laser head motion, problems related to
use of filler materials, and the very precise alignment of the joint profile and the beam. In terms of
this alignment, a rule of thumb is one-tenth of the thickness with a maximum gap equal to 0.1mm
along the profile. It is extremely important that the two parts are cut and coupled with strict
tolerances and that the materials are carefully chosen. R&D in this area is ongoing; laser welding
system sales reflect these disadvantages and are much lower than those for cutting or marking
systems. 3D applications are mainly confined to capital intensive industries.
ALTERNATIVE TECHNOLOGIES
Comparison with other welding technologies can help in the choice of the most appropriate
technology:
• the electron beam has high power density and penetration, but requires quite complex
equipment that tends to incorporate little flexibility;
• TIG has good but lower than laser penetration, can be used manually and is less expensive in
terms of equipment. The HAZ is normally wider than with laser;
24 LASER WELDING PROCESS
• Metal Inert Gas (MIG) and Metal Active Gas (MAG) have good penetration, but lower than laser,
are less sensitive to the joint gap because they allow the use of filler materials, have a wider
HAZ, can be used manually and are less expensive than lasers.
MATERIALS
Laser welding is used for particular materials. With stainless steel it provides good welding, quite
good tolerance on technological parameters, good mechanical joint properties and does not
require protective gas.
Carbon steels are normally capable of being welded by lasers, provide less tolerance than
stainless steel in terms of technological parameters, provide good mechanical joint properties,
and are sensitive to oxides requiring welding to be done in an oxygen free atmosphere. They do
not require the use of protective gas. Galvanised steels have similar characteristics to carbon
steels in terms of suitability for laser welding with the addition that the zinc vapours are produced
before the melting temperature of the steel is reached, which affects the weld pool. This problem
is resolved by the introduction of a 0.1mm gap to facilitate vapour exhaust.
Laser welding of aluminium allows is only possible for some alloys; the mechanical properties of
joints are lower, welding speeds are high, and protective gas is required.
APPLICATIONS, EQUIPMENT AND PERSONNEL
Laser welding is common in the automotive sector for tailored-blanks and production of
mechanical components including gears, and in the food and medical industries for aesthetic and
precise welds.
In the power range 3kW-4kW, five-axis CO2 laser equipment is suitable for welding items up to
1,500mm x 3,000mm x 500mm volume. This would require an investment of between €0.6-1
million, plus approximately 10% for installation and training. Welding masks and fixing tools
depend on product design and flexibility required, and their costs can range from a few thousand
Euro for simple items that can be produced internally, to hundreds of thousands of Euro for
complex items. Where electricity supplies are not stable, adequate power infrastructures need to
be in place (UPS, generators). It should be remembered that joints have to be designed for laser
welding, which may require part or all of the existing engineering drawings to be reviewed.
In terms of infrastructure and power supply, these welding lasers require voltage fluctuations of
less than ±10%, wall-plug power of up to 100kW, and gas purity similar to that for laser cutting
equipment (see Section 3.1 CUTTING).
Costs differ from country to country and are mainly related to power, gas supply (may be the same
cost as for electricity but could be twice as much depending on the application and the materials),
loading and off-loading operators, and depreciation.
Capabilities in welding and laser welding in particular, are not as formalised as they are for laser
cutting. Thus, practical experience is very important. Operators must be skilled or trained in CNC
programming, in welding processes and in welding preparation and coupling. In the case of
repeat products of simple design, learning to use the welding equipment may take months;
additional training is needed if a new process needs to be engineered.
Progressive training, from spot welding of flat rectilinear profiles to curved profiles, through
polyhedron edge welding, might be the solution.
Figure 43: pump components
LASER WELDING PROCESS
Figure 44: stainless steel container
25
4
NON-METAL APPLICATIONS: TEXTILES, GLASS, AND OTHER
OVERVIEW
Lasers are used in the manufacture of clothing and accessories, shoes and decorative items in
non-metallic materials. Several new businesses are based on the use of commercial low-power
laser systems for cutting and engraving fabric, leather, wood, paper and many other materials.
If cutting activities predominate, a plotter cutting machine may be suitable for both cutting (at
high speed) and marking (at slow speed). In the case that high marking productivity is required,
then a plotter machine for cutting and a separate marking machine 10-30 times faster may be
preferred, depending on available finance.
The systems for this type of processing normally use CO2 laser sources with power ranging from
30W for low volume use to 400W for high volume or industrial use. The systems normally include
the laser source, the mechanics for beam positioning, the software and the safety devices; some
also include the vacuum and filtering unit and a range of other options. Full enclosure of the
working area allows the equipment to be classified as safety class I, reducing the safety
requirements in the workshop. These machines are easy to use and low maintenance since the
only interface with the operator occurs in up-loading the raw material, uploading the
drawing/pattern file, waiting for the work to be finished, and off-loading the finished product from
the machine. Monthly maintenance to keep the machine in good operative condition should be
scheduled.
In terms of shop-floor requirements, as this is sealed-gas equipment, there is no need for high
purity gas supplies. The main requirement is for a stable single phase 220V/110V energy supply.
The sealed gas units can be recharged when the lasing gas is exhausted. The equipment is
designed to work in a temperature range of 10°C-40°C and 10%-85% humidity. For higher power
than 60W, the OEM may recommend water cooling and in the case of tropical environments, a
chiller.
In the case of low temperature environments, the laser source should not be allowed to freeze as
this could permanently affect its operation. For the first shift of the day in the winter time, a warmup procedure may be needed, as indicated by the OEM.
Power consumption depends on the laser output power, and the speed and thickness of the
material, and will range between 1kW and 7kW. An area of approximately 1,500mm x 1,500mm x
1,200mm will be required to house the machine, depending on the model. It should be capable of
bearing loads exceeding 300kg.
Cut accuracy is about ±0,1mm, repeatability <±15μm. In terms of writing speeds, the most
advanced equipment can exceed 3m/s with accelerations of 8g with linear motors.
THE PRODUCT
Various materials can be processed by these lasers including:
□ wood for wooden toys, customised furniture, veneers (see Figure 46: wood veneer), parquetry
for mosaics;
□ leather for shoes, bags and other fashion items (see Figure 45: clothing accessories). Cutting
speeds can range from 50 to 100mm/s on leather of 2mm thickness;
□ textiles, for decorative clothing (Figure 47: decoration on denim, this took 4 seconds with a
30W marking machine; to decorate one side of a pair of jeans could take up to 1 minute with a
100W machine), micro perforation for technical textiles;
□ embroidery: in a production line, laser machines can cut the appliqué needlework after
embroidering (see Figure 48: embroidery cutting);
□ paper for stencils, piercing, papers for the printing industry;
□ acrylic tissues;
26 NON-METAL APPLICATIONS: TEXTILES, GLASS, AND OTHER
□ plastic and rubber for industrial product identification, decoration, gaskets, tampo-graphic
clichés and rubber stamps;
□ welding of transparent plastic parts, such as Plexiglas on opaque plastics;
□ plastic components for electronics, such as polyester and polycarbonate membrane
keyboards, phones.
The dimensions of the raw sheets can be up to 1,200mm x 700mm, and can range in thickness
from very thin to 200mm or more and up to about 25kg in weight.
Although the equipment is flexible in terms of raw materials types and surface finishing, for some
aspects it may be necessary to consult OEMs. For example, plastic items, such as PVC3 and PET,
need special care because of health-hazardous vapours, e.g. dioxins, that are released in the
laser process. It may be necessary to install special filters. Denim and some other textiles and
flexible materials may need a vacuum table in order to keep them flat to enable accurate cutting
and prevent fires.
Laser marking can make the chemicals, such as disposable acids, used in traditional processing
methods, redundant. It also guarantees better replication than mechanical wear-effect tools
(which often were manual).
Figure 45: clothing accessories
Figure 46: wood veneer
PERSONNEL AND EQUIPMENT
In terms of skills, operators must be able to use computers in order to load drawings and CAD
systems in the case that a new design is required. Up/off-loading machine operators do not
require any particular capabilities. In some cases, the equipment is configured the same as in a
PC compatible printer.
At the time of writing, a standard cutting plotter represented an investment of €10,000 for lowvolume low-power (25W output) applications or €70,000 for high speed cutting (for thick wood)
(350W output). Marking equipment costs from €20,000 for 30W equipment to €100,000 for
350W plus equipment for specific applications; most of this cost is in the laser source.
Installation and training probably involves two days and up to €1,000 depending on the distance
of the OEM from the customer’s premises.
Depending on the application, other investments might be considered worthwhile, e.g.:
□ vacuum table for textiles, which would cost around €5,000;
□ vacuum and filtering units, at a cost of €10,000 for the above mentioned power ranges
(required where PVC, PET, ABS, chrome tanned leather or other heavy contaminants are
involved);
□ equipment enclosures with suitable materials to upgrade safety from class IV to class I, which
could cost between €3,000 and €10,000, depending on the dimensions;
□ water chilling units.
3
Some legislations do not allow processing of PVC because of the dioxins generated,
NON-METAL APPLICATIONS: TEXTILES, GLASS, AND OTHER
27
Running costs are mainly related to power, ranging from 1kW-7kW, and the hours of use, the duty
cycle, the model, and the maintenance cycle. The latter includes:
□ effective suction (and in certain cases, compressed air) is required to maintain the reliability of
the machine. If contaminants are not removed this could reduce the life of the mechanical
guides from two years to six months, involving approximately €1,500 investment per
substitution;
□ cleaning of filters at least once a year, and more often in the case of dusty applications and
contaminating materials;
□ daily or weekly cleaning of lenses and mirrors. Dirty optics and dust deposits can cause
failures due to the laser not being completely reflected, causing overheating and damage to
the material. New lenses cost €150-300;
□ gas refills for the CO2 laser. Depending on the manufacturer and the model, in most low power
laser sources, the gain medium is sealed and does not require to be refilled. For medium to
high power, it should be refilled every 5,000-10,000 hours at a cost of around €2,000 (or
every 20,000 hours at a cost of €15,000 for 30W equipment and €30,000 for 115W
equipment). Some OEMs exchange exhausted tanks for full ones; others require the tank
change to be carried out by one of their employees.
Figure 47: decoration on denim
Figure 48: embroidery cutting
28 NON-METAL APPLICATIONS: TEXTILES, GLASS, AND OTHER
4.1
FASHION MARKING
Lasers facilitate the adoption of new designs, interpretation of stylists’ ideas, unpredictable
quantities and short time-schedules common to the fashion sector. This is the case in a small (3
employees) company, which uses eight CO2-laser machines to process a range of textiles
including cotton, polyester and technical tissues for their customers. Graphic skills, speed,
definition and know-how about materials and machine configuration, accrued through some 4-6
years of experience in the company enable the company to deliver prototypes and then produce
in bulk according to a time schedule.
The fashion sector has pronounced seasonality. In February, for instance, a stylist might bring a
concept sample to be interpreted, designed and prototyped by March. Two months later, the
company could receive orders in quantities ranging from a few thousand to hundreds of
thousands of items, required for delivery to retail shops in July. Unexpected repeat orders are
quite common. To accommodate these, the company calls on the services of a pool of 20
temporary workers, with experience in using lasers.
A graphic designer, a skilled machine operators and a stylist together decide on the best graphic
file for laser production. Their know-how allows them to render the idea graphically, and define
the appropriate configuration of laser power and speed to achieve the desired edge finishing, or
the precisely-graduated wear-effect, with tight tolerances and high replication for bulk production.
Figure 49: graduated wear-effect on
denim
Figure 50: composed pictures
Figure 51: marked golf with laser
machining detail
Figure 52: holes in technical tissue
The following parameters are important for quality marking and cutting:
□ flatness of the tissues on the working table, required for proper definition, and can be
supported by a vacuum table although seams and pockets, etc. make complete evenness
difficult to achieve;
□ operating area width: the wider the area, the less defined the work with the same machine;
□ material: a percentage of synthetic fibre improves cauterisation (thermo-welding) and reduces
fraying;
□ colour: thermal affected zones show up less on darker dyes. Colour changes resulting from
laser treatment are more common in immersion-dyed and wire-dyed textiles.
FASHION MARKING
29
Figure 53: marked hearts on thick tissue
Figure 54: cut and marked accessories
The power of equipment used for CO2 marking, ranges from 60W to 400W, enabling work
surfaces of 250mm x 250mm up to coils of tissue bigger than 2,200mm. The marking equipment
can also be used for cutting. The investment is largely proportional to laser source power and
ranges from €100,000 to €250,000 per machine. The case company made its equipment
purchases based on the expected market and products rather on power criteria.
Preparation
area
5
1
1, 2, 3, 4, 5, 6, 7, 8:
CO2 marking
stations
6
: individual
buffers
3
7
4
8
Quality control is
carried out at each
marking station by
the operator
2
Temporary
storage
Figure 55: Textile marking lay-out
A typical SME investment decision process for laser equipment for the fashion industry would
include:
• benchmarking equipment in terms of types of laser decorations. This could include typical wear
effects, stripe-construction, image impression, and paper-model cutting. The equipment would
likely require one operator and an area of 30m2-40m2;
• budgeting in relation to appropriate graphic workstations and software (normally commercial
software is available). The area required for a graphic workstation and an operator would be
approximately 25 m2;
• budgeting for the data sharing system, which could include a LAN (100Mb/s should be suitable
for a SME but bigger operations might require 1000Mb/s) to connect the workstation, the laser
and a server to archive the data typical of any material or process. Formalisation/codification
of the know-how (materials, procedures, processing parameters) is more helpful than tacit
knowhow which requires face to face transmission of knowledge;
• budgeting in time needed for training of operators and trials.
The main running costs for lasers are related to electricity usage, replacement of lasing gas, and
maintenance of optics and electronic components, which is carried out, machine by machine,
while temporarily inoperative.
This benchmarking may require companies to compare the outputs of three analyses:
30 FASHION MARKING
• monthly costs, such as the space rent, machine leasing (or loan and depreciation), staff costs,
previous running costs, other costs (such as overheads), expressed as cost per second.
Absolute costs will vary from country to country; however, estimates might be 45%-50% for the
leasing instalments, 35%-40% for operators, 8%-15% for space rent, 5%-7% for maintenance
and consumables;
• time and cost to finalise the graphics for typical decorations/works and to produce a lasered
prototype. Based on the estimated cost per second and the time schedule for production, the
cost per prototype, and the number of pieces per day and per month. Timing will be highly
dependent on factors such as complexity and operator skills; however, a ball park figure might
be 1 hour for a wear effect, 2 hours for a stripe-decoration, 3 hours for an image impression,
and half an hour for paper-model cutting;
• average time and cost to produce typical products in batches or in series. Based on
cost/second and time/piece, the cost of the product and the number of items per day or month
can be calculated, based perhaps on more than one minute for the same wear effect as above,
about 2.5 minutes for the stripe-decoration, about 6 minutes for the image impression, and
between 3 and 12 minutes for paper-model cutting, depending on the technology.
FASHION MARKING
31
4.2
TEXTILE PATCH PRODUCTION
Inkjet printing and laser cutting allow SMEs to produce textile patches.
Industrial embroidery is becoming more capital intensive in order to process sufficient volume
competitively. Specialised machines with multiple embroidery heads that operate 24 hours/day
and 7 days/week, combined with laser cutting heads, are capable of large volumes of outsourced
production in globalised value chains. This greatly reduces the margins for SMEs that produce
embroidery on a smaller scale.
The SME has two alternatives: higher value added embroidery or inkjet plotted patches to be
processed on the fabric or to be cut and applied afterwards. Sealed CO2 lasers can be used to
support cutting and application for both embroidery and printed patches.
Value added embroidery requires capabilities in terms of knowledge about the mechanical
properties of the fabrics being coupled (e.g. a very tough patch could stretch the base material),
resulting in the mechanical setting of the machine requiring frequent intervention. Investing in
machines with laser heads coupled with embroidering heads will bring advantage because off line
cutting solutions do not guarantee quality.
Figure 1: Embroidery with laser cutting
In the case of embroidery with laser cutting, flexibility in changing the design (and machine setup) from one batch to another and the capability to produce complex designs are of fundamental
importance and require fairly high level skills and good machine operation. An eight-head
embroidering machine and related services will require one operator and 50m2 of space. Output
in terms of embroidering should be 200 pieces/day.
Figure 2: embroided item
Figure 3: embroided and laser cut item
Inkjet patch printing and laser cutting are also low cost opportunities for SMEs. The investment
required is significantly lower than for embroidering machinery, i.e. in the range €30,000€50,000 rather than €100,000-€150,000. The machines require the same amount of space i.e.
50m2, but the overall dimensions of the plant will be less than 300m2. The inkjet and laser
systems can work on rolls of 1.5m width and produce up to 5,000 patches per day, which can
then be applied by small hot-presses at a rate of 400–500 pieces per day per operator. A small
press costs approximately €2,000. SMEs may consider outsourcing batches of over 10,000 items
to specialised suppliers, for delivery within say 30 days. At the time or writing, this was a lower
cost option and allowed more flexible and more remunerative smaller batch operations in house.
32 TEXTILE PATCH PRODUCTION
Figure 4: printed, cut and applied
patches
Figure 5: multicolour printed patch
Printing is also a simpler operation than embroidering for an SME as it is configured as a plotter
to the PC and can be executed on the finished garment, providing the flexibility to cope with
sudden variations in fashion or promotional demands (e.g. the launch of a new product, the
opening of a new branch, special events). Given the innovation in fabrics, and in printing films
and inks there is a big margin for experimentation. It is possible to program laser heads to
contour patches and mark some design on the inside of the item. Before the introduction of the
laser and the inkjet systems, the industry used serigraphy and shears that cut up to 20 layers
overlapped, which provided much less flexibility.
One skilled operator is required for the printing and cutting machine, one for graphic design and
one for the hot-presses. A new printing and cutting operator, without formalised training, will take
two years to become skilled in the job, involving much learning by doing and the associated costs;
to learn the skills of embroiderer takes three years. In order to reduce these costs, SMEs may pay
for operator training, perhaps in a more experienced company.
Inkjet printing and a laser cutting system would add the following costs: 40%-45% for inks and
print-base films, 20% for press personnel, and 20% for graphics personnel, 7%-8% for
maintenance (in the case of embroidering this would be around 35%).
TEXTILE PATCH PRODUCTION
33
4.3
CRYSTAL PROMOTIONAL GADGETS
The promotional gadget industry customises items such as pens, folders, key holders, crystals,
etc. with company names or logos, or personal images commemorating special occasions, e.g.,
anniversaries, inaugurations, new product launches and others, that occur throughout the year.
Competition in standardised items and cheaper raw-materials (lead content less than 19%) has
led to a margin-competition market, in which economy and premium products are differentiated.
In our case firm, a 1999-registered-SME engraves 2D and 3D images inside crystals, showing
software-graphic files or images of a person, if a scanner – or multiple scanners - captures the
input. Crystals can measure up to 200mm x 100mm x 100mm.
Most of the time, graphic and laser machine operators work together on a 1 shift/day basis; at
times of peak demand personnel numbers increase and work occurs in a two or three shift
operation.
Figure 6: 3D Engraved
crystals
The company relies on four diode-pumped green and infrared Nd:YAG machines with 7-8W peakpower that can accommodate 1,000 points/second up to 3,000 points/second. Depending on
the item design and the machine model, the engraving cycle can last from 1-20 minutes. A laser
machine can engrave one item per session or multiple items using a moving 400mm x 600m
worktable and automatic loading and off-loading devices. The investment required for such
equipment at the time of writing, ranges from €50,000 to €250,000.
Key parameters are the power, the speed, the temperature and humidity of the environment, and
the raw materials. Raw material composition, which can vary from lot to lot, influences the
configuration of the machine and the duty cycles; in the absence of certification of the
composition, in order to avoid cracks in the crystals, a series of trials will be necessary before
starting production.
34 CRYSTAL PROMOTIONAL GADGETS
5
LASER INSPECTION
OVERVIEW
Laser inspection is a visual verification and checking on 2D and 3D parts through a laser scan
that collects hundreds or even thousands of points per second with a certain degree of accuracy
(in commercial devices ± 0.05mm) and can digitise an image that can be compared with a CAD
drawing. The technology is also suitable for reverse engineering.
3D laser scanning is suitable for dimensional inspections, for instance, in automotive chassis, in
cast parts, such as engines or for weld checks/tracking in pipes. Commercial technologies can
scan a complicated automotive 50mm x 20mm shaped metal-sheet item with holes, in 4 minutes
collecting 1.6 million points in this timeframe.
This chapter discusses flat part inspection directly on the shop-floor, on-line or off-line, in which
the laser scan compares the item with the form and the tolerances required by the CAD.
The technology enables significantly shorter inspection times (and therefore lower costs of
machine downtime) than other optical or coordinate measuring systems, the possibility to get
automated statistical process control reporting and the possibility to reverse engineer parts.
Normally checks are carried out on first article inspection in the first batch to reveal any design,
tooling or other problems, enabling reconfiguration before main production thereby reducing
scrap costs.
This type of equipment requires stable 220/110V electric power and a LAN to load CAD drawings,
involving investment of the order of €70,000. Training personnel on software and machine use
takes approximately 3 days.
In terms of running costs maintenance consisting of cleaning and periodic substitution of the
glass surface is the most expensive, and could be up to several hundred Euros per month,
cleaning projector filters and in some cases re-calibration are required once a month. Commercial
systems do not require programming and self-calibrate at each check. Experience shows that
payback is around 1-2 years.
2D commercial devices scan with a visible laser diode beam at power in the range of mW, taking
approximately 500 points per second, and an inspection cycle of seconds or minutes.
The parts typically requiring inspection are the opaque components (in metal, plastics, paper
products, composite materials, rubber, cork, vinyl, felt, leather and fabrics), which are less than
2,440mm x 1,220mm with thicknesses up to 200mm and weighing up to 130kg.
Where the piece is wider than the standard worktable, it is possible to merge multiple inspections
carried out by a single scanner or multiple scanners.
Figure 7: 2D laser inspection equipment
LASER INSPECTION
35
6
LOOKING AHEAD
Lasers are a standardised technology in many manufacturing contexts; their use could increase
depending on how well they answer certain economic needs. These can be summarised as
reducing energy consumption (higher efficiency), lower maintenance costs (e.g. by improved optic
alignment), lower level financing (lower initial capital cost) and lower facilities costs (cooling, floor
space). The more mature CO2 and lamp-pumped Nd:YAG technologies will continue to undergo
improvement to meet these demands. However, it is expected that other technologies such as
fibre lasers, diode lasers, diode pumped Nd:YAG and disc lasers will be more efficient and will
progressively erode the market share of these two technologies in areas such as welding and
cutting, and will enlarge the spectrum of applications to 3D remote welding, micro-welding and
processing and portable processing.
36 LASER INSPECTION
7
BIBLIOGRAPHY
Below is a list of some useful reference works on lasers for materials processing:
1. Laser Institute of America LIA Handbook of Laser Materials Processing, Orlando: Magnolia
Publishing, (2001).
2. John Powell, Laser Cutting, London: Springer Verlag, (1998).
3. Walter Koechner, ‘‘Solid-State Laser Engineering’’, Springer (1996).
4. Dieter Schuoker, ‘‘High Power Laser in Production Engineering’’, (1999).
5. Walter W. Duley, ‘Laser Welding’, John Wiley & Sons inc. (1999).
6. Orazio Svelto, Principles of Lasers, (V ed.), Plenum Press (1999).
The following articles appear in major scientific and specialist commercial magazines or on
university websites. Many are subject to copyright and can be purchased over the internet or
obtained through the local university library system or through the German National Library of
Science and Technology (Technische Informationsbibliothek Universitätbibliothek Hannover,
http://www.tib.uni-hannover.de/en/) at nominal cost.
A summary of each article is provided at the end of this list, which may be useful if access to
internet or university database is not easy.
Table 1: year-sorted reference articles
AUTHOR
SOURCE
Summary
page
41
ID
TITLE
YEAR
1
Laser marketplace
2007: diode laser
market takes a
breather
Laser marketplace
2007: laser industry
navigates back to
profitability
Laser versus labour
2007 Robert V. Steele
LaserFocusWorld
magazine
2007 Cathy Kincade;
Stephen Anderson
LaserFocusWorld
magazine
41
2007 Tim Heston
Fabricating and
Metalworking magazine
Dipartimento di
Innovazione Meccanica e
Gestionale DIMEG,
Università degli Studi di
Padova
LaserFocusWorld
magazine
Optics and laser Europe
magazine
43
2007 Breck Hitz Leoma
Photonics Spectra
43
2006 Robert V. Steele
LaserFocusWorld
magazine
LaserFocusWorld
magazine
44
2
3
4
Non traditional
machining applications
2007 DIMEG
5
Elliptical beam speeds
laser cutting
Laser water jet cools
and cuts in the material
world
New laser export
controls set to take
effect
Laser marketplace
2006: diode doldrums
Laser marketplace
2006: market’s
messages are mixed
2007
6
7
8
9
BIBLIOGRAPHY
2007 Jacqueline Hewett
2006 Cathy Kincade;
Stephen Anderson
43
43
43
44
37
ID
TITLE
YEAR
AUTHOR
SOURCE
Summary
page
44
10 Integrated sheet-metal
production planning for
laser cutting and
bending
11 Fibre lasers make their
mark
12 Metal cutting at light
speed
13 Super saver laser
2006 B. Verlinden, D.
Cattrysse, D. Van
Oudheusden
International Journal of
Production Research
2006 Kimberley Gilles
14 3D advanced
technologies inspection
make food inspection
palatable
15 Development of a
technology of two-beam
laser welding and fullsize tests of oil and gas
transmission pipes
2006 Winn Hardin
Welding design and
fabrication magazine
Welding design and
fabrication magazine
Cutting tool engineering
magazine
Machine Vision On-line
45
Welding international
46
IPG photonics
Corporation The 2005
photonics handbook
Proceedings of
Institution of Mechanical
Engineers
Welding design and
fabrication magazine
46
2005 Susan woods
Cutting Tool Engineering
magazine
47
2005 Andy Sandford
Metalworking production
magazine
Critical Review: industrial
lasers and applications.
Proceeding of the SPIE
vol. 5706
Critical Review: industrial
lasers and applications.
Proceeding of the SPIE
vol. 5706
47
16 Fibre lasers: emerging
in major markets
2006 Richard Mandel
2006 Daniel Margolis
2006 AG Grigor Yants,
AN and NV Grezev,
IA Romanov,
VI Kazachkov,
FD Nuriakhmetov,
VN Goritskii
2005 Bill Shiner
17 Cost forecasting model
for order-based sheet
metalworking
18 A plan for productivity.
Laser cutting and
welding shops fight
tough competition
19 Laser like focus. 2-D
and 3-D laser cutting
machines add value to
shops
20 Very focused
2005 A. Bargelis; M.
Rimasauskas
21 Impact of industrial
needs on advances in
laser technology
2005 Paul Denney
22 Trends in laser material
processing for cutting,
welding, and metal
deposition using carbon
dioxide, direct diode,
and fibre lasers
23 Fabrication of 3-D
components by laser
aided direct metal
deposition
24 Development and
trends in laser welding
of sheet metal
2005 Wayne Penn and
the Alabama Laser
Team
38 BIBLIOGRAPHY
2005 Charles Bates
2005 Jyotirmoy
Mazumder,
Huan Qi
2005 F. Vollertsen
Critical Review: industrial
lasers and applications.
Proceeding of the SPIE
vol. 5706
Sheet Metal 2005,
Proceedings of the 11th
conference
45
45
45
46
47
47
48
48
48
ID
TITLE
YEAR
AUTHOR
SOURCE
Summary
page
49
25 High-power fibre lasers
– Application potentials
for welding of steel and
aluminium sheet
material
26 Small devices
manufacturing by
copper vapour lasers
2005 C. Thomy,
T. Seefeld,
F. Vollertsen
Sheet Metal 2005,
Proceedings of the 11th
conference
2005 S. G. Gorney, I. V.
Polyakov, M. O.
Nikonchuk
49
27 Fabrication flexibility. At
Work in Brazil’s ‘no-till’
zone
28 Let there be light
2004
Micromachining and
microfabrication process
technology, Proceedings
of SPIE Vol. 5715
Tooling and Production
magazine
Design engineering
magazine
LaserFocusWorld
magazine
Industrial Laser
Solutions magazine
Photonics Spectra
49
LaserFocusWorld
magazine
50
VIMs 2002 International
Symposium on Virtual
and Intelligent
Measurement System
proceedings
ICS UNIDO publication
51
29 Machine vision guides
lumber cutting
30 Material processing
with fibre lasers
31 CO2 lasers make the
cut
32 Fibre lasers grow in
power
33 Towards real-time
quality analysis
measurement of metal
laser cutting
34 ICS lectures on
industrial application of
lasers
35 Laser applications in
electronics and
optoelectronics industry
in Japan
36 Laser cutting: industrial
relevance, process
optimisation and laser
safety
37 High power fibre laser
2004 John Excell
2004 Yvon Bouchard,
Philip Colet
2003 Ruediger Hack
2003 Holger Schülter
2002 Valentin
Gapontsev,
William Krumpke
2002 Cesare Alippi,
Vincenzo Bono,
Vincenzo Piuri,
Fabio Scotti
2000 N. U. Wetter, W.
De Rossi, F.
Grassi, W.M.
Steen, Spero
Penha Morato
1999 Kunihiko Washio
1998 H. Haferkamp, M.
Goede, A. Von
Busse, O. Thürk
1991 V.P. Gapontsev;
L.E. Samartsev
SPIE conference on laser
applications in
microelectronic and
optoelectronic
Part of the opto-contact
workshop on technology
transfers, start-up
opportunities and
strategic alliances,
Québec, Canada
Institute of Radio
Engineering and
Electronics; USSR
Academy of Science
49
49
50
50
51
51
51
52
.
BIBLIOGRAPHY
39
8 SOURCES OF INFORMATION
USERS OF LASER SYSTEMS
COMPANY
APPLICATION
LOCATION
1
A4ricami Srl
Embroidery and textile patch production Correzzola (PD), Italy
www.a4ricami.it
2
Cantuna Cut Srl
Metal sheet laser cutting and marking
Pieve D’Alpago (BL),
www.axprofessional.it
and tooling production
Italy
3
Demont Srl
Promotional items
Bassano del Grappa
www.demontpromo.com
(PD), Italy
4
Inox Veneta SpA
Laser cut food and beverage production San Giacomo in Veglia
www.inoxveneta.it
plant components
(TV), Italy
5
Laser Style Italia Srl
Marking and cutting on textiles
Fanzolo di Vedelago
www.laserstyleitalia.it
(TV), Italy
6
Lorenzin Srl
Metal sheet laser cutting, bending, and
Sandrigo (VI), Italy
welding
7
M.C.M. Srl
Metal sheet laser cutting and fabrication Casalserugo (PD), Italy
8
MED Srl
Health Technologies engineering and
Maserà (PD), Italy
www.ideamed.net
manufacturing
9
Omesa Srl
Metal sheet laser-cutting, bending and
Brendola (VI), Italy
www.omesa.com
welding
Petrochemical industry instruments OEM Reschigliano (PD),
10 SAMI-Instruments Srl
www.samiItaly
instruments.com
11 TEC-SIM Srl
Pharmaceutical and chemical plant
Silea (TV), Italy
www.tec-sim.com
components
12 Zero Seven Studio
Laser Consultancy and Integration
www.zeroseven.it
MANUFACTURERS OF LASER SYSTEMS
COMPANY
APPLICATION
1 Prima Industrie SpA
Laser cutting, welding and marking
http://www.primaindustrie.com/
2 Rofin
Lasers for industry
www.rofin.com
3 Sei SpA
Laser cutting and marking
www.seilaser.com
4 Sisma SpA
Laser systems and laser sources for
www.sisma.com
jewellery
5 Trotec
Laser cutting, marking and engraving
www.trotec.net
UNIVERSITY
DEPARTMENT
1 University
of
Padova,
Department of Information
Engineering
www.dei.unipd.it
2 Polytechnic of Milan, SITEC
www.sitec.lecco.polimi.it/
40
LOCATION
Collegno
(TO),
Italy
Hamburg,
Germany
Curno (BG), Italy
Schio (VI), Italy
Marchtrenk,
Austria
SERVICE
LOCATION
Research, Graduate and Post-Graduate Padova, Italy
Education, R&D Services
Research, Graduate and Post-Graduate Lecco, Italy
Education, R&D Services
9 ANNEX: SUMMARIES OF ARTICLE
The following paragraphs provide summaries of the articles in Table 1: year-sorted
reference articles at page 37. The summaries do not conflict with copyright or
constitute plagiarism.
1.
Laser marketplace 2007: diode laser market takes a breather
By Robert Steele, published in Laser Focus World in February 2007,
downloaded at :
http://www.laserfocusworld.com/display_article/283868/12/ARTCL/none/n
one/LASER-MARKETPLACE-2007:-Diode-laser-market-takes-a-breather
The 2006 diode-laser market had mixed results The diode laser for optical
storage applications had a downturn due to a maturing market and
decreasing prices. On the other hand, most of the other applications,
including high-power-diode applications, experienced moderate growth. In
terms of revenue, following three years of steady growth, the market declined
from US$3.23 billions in 2005 to US$3.10 billions in 2006. In terms of
volume, there has been a 5% increase, with 815 million diode lasers shipped
in 2006 especially in consumer optical-storage applications confirming
growing demand, but at lower prices. In 2006 a new generation of high
capacity optical storage technologies, HD-DVD and Blu-ray, was introduced. In
telecommunication lasers, growth occurred in every segment: long-haul,
metro and access. Tuneable lasers saw rapid growth. Average power and
sales of pumping lasers increased while unit prices decreased and another
two years of good results was expected. Fibre laser pumping diodes showed
huge increase with 90% of the market going to IPG Photonics. The article
describes the market situation for other applications (LAN, bar code scanning,
sensing, entertainment, inspection and measurement) and diode-laser
products and configurations and describes the methodology used to collect
the data.
2.
Laser marketplace 2007: laser industry navigates back to profitability
By Kathy Kincade and Stephen Anderson, published in Laser Focus World in
2007, downloaded at: http://www.laserfocusworld.com/articles/282527
The 2006 worldwide laser business was surprisingly strong thanks, in large
part, to better-than-expected performance by the semiconductor industry and
the rebound of optical telecommunications. Non-diode laser sales grew 11%
while a general positive unit growth for diode lasers was offset by generally
declining prices with -4% in sales. A total market of US$6 billion with an 8%
revenue increase for all lasers was forecast for 2007. A fluctuating monetary
situation and renewed interest venture capital in optics and photonics-related
ventures will affect the future market. The European market grew by 12%15% particularly in Germany, Benelux, the UK and Italy, but also in several
Eastern European countries. The Asian market continues to represent great
potential for laser and photonics, with China considered to be more a
producer than a consumer. Important issues are the progressive
displacement of non-diode-lasers by diode-lasers from medical therapy to the
graphic arts, the growth of solid-state lasers, the challenge from fibre-lasers,
which grew 55% in terms of revenues between 2005 and 2006 and continue
to erode the market for lamp- and diode-pumped solid state lasers. Growth in
semiconductor manufacturing shows promise for the optoelectronics industry
while material-processing high-power (around 6kW) CO2 lasers as well as
laser marking systems grew by about 10% reaching US$1.7 billion in 2006.
The article reports the situation in the market for lasers for scientific
research, instrumentation, image recording, entertainment and display and
41
military and aerospace applications. There is a description of how the data
were collected.
42
3.
Laser versus labour
By Tim Heston, published in Fabricating and Metalworking in 2007,
downloaded at : http://www.fandmmag.com/print/Fabricating-andMetalworking/Laser-versus-Labor-/1$219
The article discusses optimising job-routines, planning and bottlenecks
through investment in automation and equipment as part of lean
manufacturing. Investing in high-end equipment can reduce bottlenecks and
optimise flows. Skilled machine operators represent value added, reflected in
the normally increasing wages versus equipment depreciation and
increasingly tougher market competition. It is necessary for job-shops to
analyse operator tasks when machines are operating to avoid skilled operator
time being spent on low-end activities. For instance, material handling and
tool change-out can be achieved by automatic specialised nozzle-lens
changes. Instead of focusing on cutting speeds, job shops should look at how
many parts can be completed within a certain time, which will be increased
with the application of automated materials handling, automated tool change
and especially by a good manufacturing plan from estimation to delivery,
through scheduling, production, post process inspection. Many job-shops
have moved to 3D laser cutting, a smaller but higher margin market that can
complement 2D works.
4.
Non traditional machining applications
By the Department of Innovation in Mechanics and Management of the
University of Padova, Italy, downloaded at:
http://www.dimeg.unipd.it/didattica/tecme4/8_Non_conventional.pdf
The text is part of a university course in Mechanical Technologies and
discusses elements of so-called non-conventional-machining technologies.
The presentation encompasses: applications, and many types of machining
including laser, chemical, thermo-chemical, ultrasonic, water-jet, abrasive-jet,
electric discharge, electron beam and electro-chemical machining and
grinding. The text provides a schematic illustration of the laser machining
process, the applications, the characteristics, and advantages and
disadvantages.
5.
Elliptical beam speeds laser cutting
Published in Laser Focus World in January 2007 downloaded at:
http://www.laserfocusworld.com/display_article/282651/12/ARCHI/none/N
Brea/Elliptical-beam-speeds-laser-cutting
The article focuses on a specific commercial application to accelerate silicon
wafer cutting. The elliptical beam enhances cutting speeds by 3 to 4 times
from 16.7mm/s to 62mm/s.
6.
Laser water jet cools and cuts in the material world
By Jacqueline Hewett and published in Optics and Laser Europe magazine in
March 2007, downloaded at: http://optics.org/cws/article/industry/27415
The article focuses on a commercial application that directs a laser beam into
a thin water-jet technology to cut, drill and dice materials as varied as gallium
arsenide and polycrystalline diamond. The advantages are no heat-affected
zones, parallel kerfs and the ability to cut thick and hard materials. The water
jet cools the work piece between laser pulses and expels molten materials
from the cut.
7.
New laser export controls set to take effect
43
By Breck Hitz of LEOMA and published in Photonics Spectra magazine in
January 2007, downloaded at:
http://www.photonics.com/content/spectra/2007/January/features/86091.
aspx
The article describes recent changes to the Wasenar export controls
compared to the early 1990s. These export controls are aimed at potentially
critical military laser applications. The article lists the countries that have
signed up to the Wasenar agreement and the criteria for free-export vs
licensed-lasers such as power, wavelength, and overall efficiency.
8.
Laser marketplace 2006: diode doldrums
By Robert V. Steele and published in Laser Focus World magazine in February
2006, downloaded at: http://www.laserfocusworld.com/articles/248128
The article describes the diode laser market situation in 2006. Although
several segments, particularly telecom and high-power applications, have
gained, price erosion has restrained revenue growth for the optical-storage
segment after a flat 2005. The diode market in 2005 was US$3.23 and
represented 59% of total commercial laser revenues, the most important
applications being for optical storage (54%). For 2006, moderate growth (9%)
was expected for all applications including telecommunications. The article
gives detail on optical storage, telecommunications, high-power diode
applications, and others. It describes the laser products and configurations
and how the data were collected.
9.
Laser marketplace 2006: market’s messages are mixed
By Kathy Kincade and Stephen Anderson, published by Laser Focus World in
January 2006, downloaded at:
http://www.laserfocusworld.com/articles/245112
The article describes the laser market situation in 2005 with low overall
growth masking some strong performance. The laser industry is considered to
be maturing, but still at an early stage. Growth is due more to new
applications than to increased volumes. Some system manufacturers
registered major increases over 2004 (more than 14% revenues). The
semiconductor market has stalled, although sales of flash memories are
encouraging. China continues to experience two-digit growth in most sectors
including both production and consumption of low-cost laser and laser
systems for domestic industrial applications such as marking and fabric
cutting. Europe has not fared as well as expected with only a 3% growth in the
machinery sector in 2005. Industrial materials processing (primarily metalworking and marking) have done better. Fibre lasers in general grew 53% on
2004 levels, and +47% from 2005 to 2006 (forecast). Fibre lasers for
industrial applications grew by 33%, of which more than 75% was at the
expense of mainly lamp-pumped Nd:YAG; the CO2 market (mainly for sheetmetal and plate cutting) which was not feeling the impact from fibre. The
article describes the medical therapy, basic research, instrumentation, image
recording, entertainment, military/aerospace laser segments and outlines the
methodology used to collect the data.
10.
Integrated sheet-metal production planning for laser cutting and bending
By B. Verlinden, D. Cattrysse and D. Van Oudheusden and published by the
International Journal of Production Research in January 2007, downloaded at
http://www.tib.uni-hannover.de/en/.
The paper discusses the need to reduce scrape material in 2D cutting and the
time-consuming set-ups for 3D bending through the use of an integrated
production planning model. The single optimised nesting of parts may require
44
additional setups at the press-brake while the proposed model integrates the
creation of feasible grouping of parts and the minimisation of the number of
set-ups at the press-brake. The total execution time reduction is expected to
exceed 4%, representing an average annual saving of about 10 days.
11.
Fibre lasers make their mark
By Kimberley Gilles, published in Welding Design and Fabrication in
September 2006, downloaded at
http://www.weldingmag.com/323/GlobalSearch/Article/False/31981/.
The article describes the characteristics and advantages of commercial fibre
lasers for marking: high contrast, permanent product identification, and little
processing debris. The text reports the improvements brought by the fibre
laser to power and beam quality, and the advantages of laser marking. It
discusses the lower levels of debris generated in the marking process when
using fibre lasers compared to Nd:YAG systems. Other advantages of fibre
lasers are small spot size, high beam quality, and compact size. Commercial
fibre lasers can avoid distortions - even cutting, welding and marking within
0.1mm. The duration of water cooled fibres is within the 400,000 hours span.
However, these lasers are more sensitive to ambient temperature than lamppumped lasers.
12.
Metal cutting at light speed
By Kimberley Gilles, published in Welding Design and Fabrication magazine in
September 2006, downloaded at
http://www.weldingmag.com/323/GlobalSearch/Article/False/31981/.
The article gives an overview of the spread of commercial laser technologies
for cutting in mid and high volume production shops based on the standards
achieved in the technology. In spite of a high initial capital investment, the
laser achieves higher speeds and reduces overall production costs, bringing a
series of advantages: no tooling, no lubrication, no contaminants, high
precision, replication and the possibility to cut abrasive, sticky and very hard
materials. Most laser cutting technologies use CO2 and Nd:YAG as the lasing
medium. This article reports on the types of cutting systems: flying optics,
hybrid and pivot beam. The current equipment operates at 1,000 2mm
diameter holes spaced 3.175mm in a piece of 1.016mm mild steel in 1
minute. Lasers can be fitted to industrial robots for 3D cutting with best
results in drawing stampings, and cutting hydro formed tube sections in the
range of 0.5mm to 5 mm. There is a trend for fibre lasers to progressively
replace CO2 and Nd:YAG in industrial applications.
13.
Super saver laser
By Daniel Margolis, published in Cutting Tool Engineering magazine in
February 2006, downloaded at
http://www.ctemag.com/archived.articles.search.php.
The article is about commercial marking solutions. Laser marking systems
range between US$35,000 and US$150,000, and prices are reducing, vs
US$10,000 for an inkjet printer. However their advantages include:
permanent marking, higher graphical adaptability, easier control, no
consumables, no surface degradation, 15 minutes training, and user friendly
software. Laser marking systems can be installed in computer numeric
control (CNC) systems to carry out more operations in parallel. The article
reports on a series of marking manufacturers and forecasts a transition from
the ink-jet to the laser system.
14.
3D advanced technologies inspection make food inspection palatable
45
By Winn Harding and published by the Machine Vision Online magazine in
August
2006,
downloaded
at
http://www.machinevisiononline.org/public/articles/archivedetails.cfm?id=2
827.
The article is on commercial solutions to automatically inspect and analyse
organic products from lumber to chicken, which vary from unit to unit.
Traditionally 2D vision systems have been used, but new applications are
emerging that require more data at higher speeds. In response to the need
for precise volumetric measurements, new commercial solutions combine 3D
laser measurement systems with 2D visual inspection systems in order to
meet the progressively stricter visual requirements for packaged food and to
optimise food production processes. A series of solutions focus on meat
portioning and quality assurance and there is an increasing need for
inspection of traditional food processing such as baking, fruit and vegetable
sorting. Colour systems can improve the contrast in 2D food inspection.
15.
Development of a technology of two-beam laser welding and full-size tests of
oil and gas transmission pipes
By AG Grigor Yants, AN and NV Grezev, IA Romanov, VI Kazachkov, FD
Nuriakhmetov, VN Goritskii and published by the Machine Vision Online
magazine in August 2006, downloaded through TIB Hannover at
http://www.tib.uni-hannover.de/en/.
The authors developed a technology with two beams at IPLIT, the Institute of
the Russian Academy of Sciences, in order to solve the problems generated
by the extreme hardness of the metal in the welded joints in pipe steels not
suitable for standard TU 14-3-1270-2001 and the cold Nordic temperatures (60°C). The two beams are combined in a single vapour gas channel. The
experimental results show that a range of distances can be maintained
between focusing spots. With an 8kW laser it is possible to weld 8mm
thicknesses with filler wire and 12mm without filler wire. The article describes
the different metallurgic structure of the welded joint areas and reports that
the property of the metal in the condition of bi-axial loading is stable.
16.
Fibre lasers: emerging in major markets
By Bill Shiner, published as an IPG Photonics Corporation technical papers in
2005,
downloaded
at
http://www.ipgphotonics.com/tp_fibre_laser_markets/resource_technical_de
livery.htm
The article describes modern commercial fibre lasers in terms of composition,
types (single mode, continuous and modulated, Raman shifted, Q-switched,
frequency doubled and tripled), output and wavelengths (from a few to a
dozen kilowatts with single mode lasers covering from UV through visible to
near-infrared spectrum), pumping and lifetime (high power diode bars and
single emitter pump diodes, from 10,000h to 200,000 hours), cooling (air or
tap water), and beam quality. The article reports on materials processing
applications of fibre lasers (including automotive welding and cutting,
sintering, marking, scribing, drilling and heat treating) and their advantages
(constant beam profile, no warm-up, micron-sized spots, high speeds and
weld penetration, compact size, wide range of applications due to the
different wavelengths, no maintenance).
17.
46
Cost forecasting model for order-based sheet metalworking
By A. Bargelis and M. Rimasauskas, published in Proceedings of Institution of
Mechanical Engineers in 2005, downloaded through TIB Hannover at
http://www.tib.uni-hannover.de/en/.
The article describes a cost forecasting method for order-based sheet
metalworking in a context of competition, falling prices and globalisation. The
article compares traditional manufacture (dies and presses) with rapid
manufacturing technologies such as CNC punching and laser cutting. The
article reports that the laser method has a margin of error between 1% and
15.5% and that it is easily applicable. Moreover, it accelerates cost
forecasting for commercial offers by 2-3 times and can be applied in both
industry and research processes.
18.
A plan for productivity. Laser cutting and welding shops fight tough
competition
By Charles Bates, published in Welding Design and Fabrication magazine in
2005, downloaded at
http://www.weldingmag.com/323/Issue/Article/False/11005/
The article reports on existing shops that invest in the latest technology and
automation and strive to improve the overall manufacturing process and
interpretation of customers needs. However, buying the most powerful and
speedy lasers is not the solution to all problems and job-shop capability is
very important in resolving a wide range of manufacturing problems and
translating customer needs by involving them in the design phase.
19.
Laser like focus. 2-D and 3-D laser cutting machines add value to shops
By Susan Woods in Cutting Tool Engineering magazine, October 2005,
downloaded at http://www.ctemag.com/pdf/2005/0510-lasercutting.pdf.
The article reports on the main industries that use commercial 2D and 3D
laser cutting, i.e. automotives (about 50%-60%), agricultural and construction
machinery, aerospace and steel processing centres, and the medical industry
– this last being a new outlet. Users range from small-shops to Tier 1
producers or automotive makers. The text describes some basic elements of
laser cutting such as materials (mainly mild steel, aluminium, stainless steel
and titanium), thicknesses and cutting speeds (for 2D: up to 48.26mm/s with
0.5mm-3mm thickness on steel, for 3D: 18mm in mild steel, 6mm in
aluminium, 8mm in stainless steel and titanium), tolerances (most
manufacturers hold ±0,0508mm to ±0,1016mm in sheet metal), and gas
assistance. It reports on the advantages that make lasers worth the
investment (no tooling costs or changes, no tool wear, repeatability, little
fixturing, finer finishing, touch free, and flexibility).
20.
Very focused
By Andy Sandford in the Metalworking production magazine in October 2005,
downloaded at http://www.ctemag.com/pdf/2005/0510-lasercutting.pdf.
The article provides information about the Association of Industrial Laser
Users, on its 10th anniversary. The association originated in a EU Eureka
project in the early 1990s and disseminates information from the countries of
Europe, organises seminars on laser applications, deals with enquiries and
questions about aspects of laser processing and works to educate the
subcontracting industry that lasers can be used in small job shops as well as
big organisations.
21.
Impact of industrial needs on advances in laser technology
By Paul Denney, published in the Critical Review: industrial lasers and
applications. Proceeding of the SPIE vol. 5706, in 2005, obtained via TIB
Hannover at http://www.tib.uni-hannover.de/en/.
47
The article reports on the diffusion and acceptance of lasers for cutting,
drilling, heat treating, welding, etc. The most popular applications are CO2 and
Nd:YAG, which have proved useful in almost all types of manufacturing
facilities. The barriers to their acceptance are: efficiency, maintenance,
investment cost, facility costs. Technological limitations will prevent lasers
from undergoing radical innovations, and new developments (fibre lasers,
disc lasers) will progressively replace them. New applications will be
developed such as 3D remote welding, micro-welding and micro processing,
portable processing. The article provides cost benchmarks.
22.
Trends in laser material processing for cutting, welding, and metal deposition
using carbon dioxide, direct diode, and fibre lasers
By Wayne Penn in the Critical Review: industrial lasers and applications.
Proceeding of the SPIE vol. 5706, 2005, obtained via TIB Hannover at
http://www.tib.uni-hannover.de/en/.
The article predicts trends in CO2 and Nd:YAG lasers and the newer fibre
lasers, highlighting that these last, although representing a quantum shift, are
not expected to replace the previous two lasers in certain industrial
applications (CO2 because of its safer wavelength and lower investment cost
and Nd:YAG because of its high power pulse). The article describes the types
of CO2 (conventional, axial and transverse flow, diffusion cooled) and diode
lasers and fibre lasers. Cutting, welding and metal deposition applications are
analysed in relation to both technologies and future trends are discussed.
23.
Fabrication of 3-D components by laser aided direct metal deposition
By Jyotirmoy Mazumder, Huan Qi and published in the Critical Review:
industrial lasers and applications. Proceeding of the SPIE vol. 5706, 2005,
obtained via TIB Hannover at http://www.tib.uni-hannover.de/en/.
The article describes the Direct Metal Deposition system, which can fabricate
three dimensional components directly from CAD drawings by delivering
various powder metals through the laser nozzle. The system eliminates
intermediate machining and considerably reduces final machining. The
interaction between the laser and the metal powder allows the material’s
microstructure to be tailored or new materials with advanced properties to be
created. Key application parameters are build rate and envelope, the ability to
make parts out of different materials, dimensional accuracy and minimum
feature size. The system was first commercialised in 2005, can be integrated
in currently available CNC machines and requires continuous corrective
measures to maintain tolerances and acceptable residual stresses. Key
conclusions are the importance of integration between design and
manufacture and the possibility for remote manufacturing.
24.
Development and trends in laser welding of sheet metal
By F. Vollertsen, published in the Advanced Materials Research Volumes 6-8
of Trans Tech Publications in 2005, obtained via TIB Hannover at
http://www.tib.uni-hannover.de/en/
The article reports on the potentials for reduction of distortions and hot
cracking in laser welding by types of materials: thin materials, steel to steel,
steel to copper, brittle materials, thick sheets. It also discusses some aspects
of fluid dynamics and alloying using filler wire. Laser welding in the last 20
years has undergone remarkable progress, technologies offer continuous
wave and pulsed solutions for different applications, the gain medium has
moved from CO2 to solid state, and the level of knowledge and expertise in
advanced processing techniques and metallurgy have helped to overcome
some former limitations.
48
25.
High-power fibre lasers – Application potentials for welding of steel and
aluminium sheet material
By C. Thomy, T. Seefeld, F. Vollertsen and published in Advanced Materials
Research Volumes 6-8 of Trans Tech Publications, 2005, obtained via TIB
Hannover at http://www.tib.uni-hannover.de/en/.
Fibre laser power is scaleable to 10kW with excellent beam quality. High
power fibre lasers are energy efficient, have a long lifetime, and are small
which have made them a viable alternative to solid state and CO2 lasers for
many applications. The authors tested a fibre laser, a Nd:YAG and a CO2 laser
of comparable power for steel and aluminium welding. The fibre laser
performed well, with improved welding speed and ability to cope with thick
sheets, especially welding with solid state lasers.
26.
Small devices manufacturing by copper vapour lasers
By S. G. Gorney, I. V. Polyakov, M. O. Nikonchuk, published in Micromachining
and microfabrication process technology, Proceedings of SPIE Vol. 5715,
2005, obtained via TIB Hannover at http://www.tib.uni-hannover.de/en/.
The article describes the characteristics of copper-vapour lasers in the
production of stents and other precision cut micro-components, whose
production requires low beam divergence, little treatment and heat treatment
zone, high accuracy and economic efficiency. The copper-vapour laser is
better suited to these applications than other small wavelength lasers such
as solid state or Excimer lasers. They can also be used to cut most materials
i.e. metals and alloys, semiconductors, ceramics, wood, graphite, and to treat
quartz. The main limitation is related to thickness, which should not exceed
500μm. Their large size and time needed to prepare them for operation
means that they are not widespread.
27.
Fabrication flexibility. At Work in Brazil’s ‘no-till’ zone
By the OEM Finn-Power, published in Tooling and Production magazine, 2004,
downloaded at
http://toolingandproduction.com/archives/1104/1104fabrication_flexibility.
asp.
This article reports on the use of a laser work centre in a market leading
Brazilian group that produces highly vertically integrated no-till seeding
equipment for agriculture. Lasers support the company’s need for flexibility
(2,000 components were previously outsourced) with linear motors and a
flying optics system with a working area of 3,000mm x 1,500mm x 100mm,
which processes mild steel 6mm thickness and aluminium 3mm thickness.
The group has equipped the system with automatic loading and off-loading
devices and operates 3 shifts per day, 7 days per week complying with the
daily, weekly and monthly maintenance schedule.
28.
Let there be light
By John Excell, published in Design Engineering magazine in 2004,
downloaded at http://www.listechnology.com/DesignEngineer-060404.htm
The article is based on an interview with the director of an aerospace
manufacturing research centre who states that laser technologies brought a
new manufacturing era due to their unprecedented complexity, strength and
low weight structures. At the heart of the spin-off company that he registered
is the development of a technique known as laser induced super (LIS)
plasticity to create a working cell completely based on lasers. LIS can create
the strongest known form of metal joints with homogeneous joining, and no
residual stresses. According to the interviewee, lasers will replace
conventional machine tools in a huge number of machining facilities.
29.
Machine vision guides lumber cutting
49
By Yvon Bouchard, Philip Colet, published in Laser Focus World in 2004,
downloaded
at
http://www.laserfocusworld.com/display_article/202939/12/ARCHI/none/F
eat/Machine-vision-guides-lumber-cutting
The article describes application of lasers for a vision system used to optimise
lumber cutting, and gives examples of how decreasing costs and increasing
ease of use and interfacing of vision systems enables the practical industrial
networking of vision and robotic systems. Key issues for competitive lumber
cutting are: reducing overheads and cutting errors, correct classification of
woods, yield optimisation, i.e. greater precision and speed. An OEM
incorporated machine-vision system is incorporated into its sawmill plants
that are equipped with cameras. Once the image is acquired, a specific
software and 2-80 lasers for triangulation (lasers project multiple lines of light
as the log comes down the arc) elaborate the information obtaining the best
yield cutting configuration, which is transmitted to the mechanical saws.
30.
Material processing with fibre lasers
By Ruediger Hack, published in Industrial Laser Solutions magazine in 2004,
downloaded at
http://ils.pennnet.com/display_article/167291/39/ARTCL/none/none/Mate
rial-processing-with-fibre-lasers/
The article reports the advantage of fibre lasers in marking, micro-bending
(for the hard disk industry) and micro-cutting applications (for the medical
devices industry). Other applications are annealing, selective soldering,
graphic arts. The main advantages are: high reliability, maintenance-free, high
wall-plug efficiency, compact design, easy-to-integrate beam delivery, coolerfree operations, small floor space, and beam delivery distances of up to 7m.
Fibre lasers are of particular interest for applications that need a small
focused spot and high power density, e.g. 100W can be focused to 5 microns
diameter with a brightness of more than 109 W/cm2.
31.
CO2 lasers make the cut
By Holger Schülter, published in Photonics Spectra magazine, 2003,
downloaded
at
http://www.photonics.com/printerFriendly.aspx?contentID=66470
This article reports the advantages of lasers versus plasma, waterjet and
punch-presses in flexible cutting and in particular of CO2-laser technologies
from the OEM’s point of view. Although CO2 lasers can offer power in excess
of 20kW, optimal power is 5kW predicting a factor of +1kW every 5 years. The
article benchmarks commercial solid state lasers with CO2 lasers, which
require an investment 2-3 times smaller and unrivalled cost per Watt, while
the former have much more flexible beam delivery conditions. The text reports
the importance of development of optics and of accurate CO2-laser
manufacturing and assembly in order to avoid harmful oil or solid-particles
contamination in the fast rotating turbo radial blowers, which ensure high
power to the equipment.
32.
Fibre lasers grow in power
By Valentin Gapontsev and William Krumpke, published in Laser Focus World
magazine, 2002, downloaded at
http://www.laserfocusworld.com/display_article/151027/12/ARCHI/none/F
eat/Fibre-lasers-grow-in-power
This article is about the evolution and characteristics of fibre lasers, invented
in 1963. Power has grown from a few milliwatts to 4W thanks to the cladding
pumping by high-power multimode diodes described in the article, which also
describes the function of the fibre laser. The advantages of these types of
lasers are high efficiency, compact dimensions, lifetime (30,000 hours vs
50
10,000 for solid state lasers), no necessity for air-cooling or maintenance. In
2000 power increased to 100W through addition of a multi-fibre side coupling
technology and, because of its brightness, it can be used for welding,
sintering and low-power brazing. Other advantages of fibre lasers are related
to the insensitiveness of the beam quality to the power operating point and
the possibility to transport the output for distances up to 100m. Combining
the output of several 100W-lasers, the OEM could scale up to 2kW suitable
for automotive welding, and even to 10kW.
33.
Towards real-time quality analysis measurement of metal laser cutting
By Cesare Alippi, Vincenzo Bono, Vincenzo Piuri, Fabio Scotti, published in the
VIMs 2002 International Symposium on Virtual and Intelligent Measurement
System Proceedings, 2002, downloaded at
http://www.photonics.com/printerFriendly.aspx?contentID=66470
The article describes an automated system for real-time quality monitoring in
laser cutting applications, for high-tech steel manufacturing industries.
Because of the sensitivity to even small variations in the metal reflectivity,
roughness, and oxidation and other risks such as metal eruption on optics
because of source instability, the reproducibility of laser metal welding
process could be affected and off-line inspections would not detect this. The
researchers developed a method based on digital image sequences of the
sparks generated during the cut, which can be used to estimate quality by
analysing the angle of the sparks and the cutting parameters (speed, type
and thickness of metal, laser type). The results are categorised as acceptable,
not acceptable, not classifiable with a mean classification error of about
0.18%.
34.
ICS lectures on industrial application of lasers
35.
By N. U. Wetter, W. De Rossi, F. Grassi, W.M. Steen, Spero Penha Morato,
published by ICS UNIDO in 2000, obtainable from ICS UNIDO or at
http://www.unido.org/en/doc/4490
The text in this book is part of a training package developed by ICS UNIDO
with the goal of examining and describing the most common types of lasers
used in industry, and providing some basic scientific background. The various
areas of industrial laser applications (cutting, welding, drilling, marketing and
scribing), as well as the all-important subject of the laser market, are covered
in detail in its seven chapters. The laser applications described are tailored to
the objectives of the high-tech industrial sectors of Latin America, and focus
on the expanding endogenous capacity in the laser field in that region.
Laser applications in the electronics and optoelectronics industries in Japan
36.
By Kunihiko Washio, presented at the SPIE conference on laser applications
in microelectronic and optoelectronic in January 1999, downloaded at
http://www.photonics.com/printerFriendly.aspx?contentID=66470
The paper discusses current status of and technological trends in laser
material processing applications in the electronics and optoelectronics
industries in Japan. The article describes typical applications (semiconductor
devices, display devices, circuit components, peripheral devices, energy
devices) by types of laser (Q-switched solid-state lasers, pulsed Nd:YAG, XeCl
Excimer, pulsed CO2, KrF or ArF Excimer). Representative applications are
photomask repairing, lithography, memory repairing, annealing, marking,
trimming, drilling, patterning, and welding for products ranging from mobile
phones to laptops, memory chips, to solar cells.
Laser cutting: industrial relevance, process optimisation and laser safety
By H. Haferkamp, M. Goede, A. Von Busse, and O. Thürk, presented at the
opto-contact workshop on technology transfers, start-up opportunities and
51
37.
strategic alliances, Québec, Canada in 1998, obtained through TIB Hannover
at http://www.tib.uni-hannover.de/en/.
The paper tackles two aspects of laser cutting: integrated quality control
techniques and environmental safety and health. It describes local high
resolution thermo-graphic measurement of the temperature distribution
within processing zones as a way to monitor process quality. Concerning
safety, the hazards involved in laser cutting are outlined: varying emission
rates with a complexity of air contaminants of which 90% are highly
breathable, and 40%-60% of which may remain in the alveoli. The article
describes different filtration systems, depending on the application and the
materials: cyclones, electrostatic filters, surface filters, adsorption,
absorption, combustion, biological filtration.
High power fibre lasers
By V.P. Gapontsev; L.E. of the Institute of Radio Engineering and Electronics;
USSR Academy of Science, 1991, obtained through TIB Hannover at
http://www.tib.uni-hannover.de/en/ and downloadable at
http://adsabs.harvard.edu/abs/1991assl.proc..258G .
The article describes a study on the possibility of increasing the output power
of fibre lasers by tens of watts and compares the advantages of these with
solid state laser: high optical damage threshold of quartz fibres, high single
pass gain, minimum forced water cooling or air cooling for power less than
10W, insensitivity to stresses due to temperature gradients typical of solid
state, low level of losses in the quartz fibres. The article forecast the
competition from fibre lasers vs high-power crystal lasers in several
applications with simple, compact, reliable and low-cost devices.
52
Part 2. Lasers in the future: perspective for small
and medium enterprises
53
SUMMARY
1
2
LASERS - THE WAY FORWARD......................................................................58
ADVANCEMENTS IN LASER SOURCES AND PROCESSES ...........................58
2.1
LASER sources improve and become more available ........................60
2.1.1
Evolving laser source schemes ....................................................61
2.1.2
Semiconductor power lasers........................................................61
2.1.3
Fibre lasers ....................................................................................65
2.1.3.1 CW fibre lasers status and perspective ......................66
2.1.3.2 Pulsed fibre lasers..................................................69
2.1.4
CO2, solid state, gas lasers...........................................................70
2.2
New interaction mechanisms...............................................................72
2.2.1
Exploiting a better beam quality ..................................................72
2.2.2
Novel processes based on short pulses......................................73
2.2.3
Improved versatility of laser sources ...........................................73
3 HOW RESEARCH CAN INFORM SMEs ..........................................................75
3.1
Direction of laser research ...................................................................75
3.2
Some examples of future developments ............................................75
3.2.1
Solar-pumped lasers.....................................................................75
3.2.2
Versatile microchannel drilling in transparent media ................76
3.2.3
The silicon laser ............................................................................76
4 CONCLUSIONS...............................................................................................78
REFERENCES.........................................................................................................79
54
List of Figures
Figure 1. Dr. Theodore H. Maiman and the scheme of his ruby laser.
Figure 2. Set-up for automated laser welding of luer-lock pipes for
application in the production of sterile components. The laser improves
welding by enabling a contactless process, with high speed and full
attainment of product specifications. Think Laser (Italy)
Figure 3. Optical power of mounted bars has grown at a compound rate of
about 15%. This may continue toward the kiloWatt per bar5.
Figure 4. Structure of a semiconductor or diode laser, with indication of
the layers to obtain the double heterostructure6.
Figure 5. Typical relation between a beam irradiated by a semiconductor
laser near the emitting surface, near field, and farther field. Typical values
of the near field size are 1 µm x few tens up to few hundreds of µm, while
the angular extension of the far field is about 50° in the fast axis (vertical
in the scheme) and a few deg. in the slow axis.
Figure 6. Single emitters semiconductor lasers, 6 W CW out of a 200 m
x 1 m active area. Emission available at different wavelengths including
808 and 840 nm. Footprint size is approx 6X10 mm. Spectra Physics –
Newport (USA) www.newport.com
Figure 7. Typical arrangement of a semiconductor laser bar, with the
parallel emission of many emitters
Figure 8. High power (60 W CW, 808 nm) semiconductor laser bars: fast
axis collimated (right) or not (left). The difference is the cylindrical lens
fixed in front of the emission area. The electrical connections are the
screws on top of the component. The footprint size is DILAS (D)
www.dilas.de
Figure 9. A pair of wavelength-multiplexed stacks (each consisting of three
sets of bars at different wavelengths) is spatially offset by half of the bar
separation for spatial interleaving. Spectra-Physics (USA) and University of
Southampton (UK).
Figure 10. Miniaturised power semiconductor lasers: the left and centre
ones with surface mount (TO 220 package) the right with the C-mount.
Osram (D)
Figure 11. The scheme of a power fibre amplifier
Figure 12. The fibre laser with several pump lasers connected, to generate
high power beams
Figure 13. Pump module assembly for high power fibre laser. IPG (Oxford,
MA USA)
Figure 14. High power fibre laser unit: assembly of the pump modules and
the fibre resonator, IPG (USA)
Figure 15. A fibre laser oscillator in operation, Laser Zentrum Hannover
(Germany)
Figure 16. Pulsed fibre laser in Q-switched operation, typically for marking
applications, IPG (Oxford, MA USA – left), SPI (Southampton, UK - right)
Figure 17. An ultrafast fibre laser (left) and the setup for its use in
micromachining. Laser Zentrum Hannover24 (Germany)
Figure 18. KiloWatt size CO2 lasers. Semilsealed type, left ElEn (Italy) and
difusion-cooled, right Trumpf (Germany)
Figure 19. Examples of state-of-the-technique station for manual welding
and molding repair, Sisma (Italy)
Figure 20. Principle of a kiloWatt Yb:YAG disk laser, pumped by
semiconductor lasers. Rofin (Germany)
Figure 21. Beam parameters product BPP as a function of emitter power
for different laser sources, IPG (USA)
58
59
60
61
62
62
63
63
64
65
65
66
67
68
69
69
70
70
71
71
72
73
55
Figure 22. Different finishing for cuts operated on a 1mm thick INVAR in
the nanosecond regime, 8 ns, 0.5 mJ per pulse (right) and femtosecond
regime 200 fs, 0.5 mJ per pulse (left) , Clark (Canada)
Figure 23. Laser welded automotive light and particular of the welded
area, Think Laser (Italy)
Figure 24. Solar powered Cr-Nd:YAG laser
Figure 25. Fabrication of microchannels in fused silica with circular cross
section femtosecond pulses, (a) end-face microscope image of a row of
microchannels and (b) SEM image of one of them.
Figure 26. Scheme of an ultrafast silicon laser
56
74
75
76
77
ACRONYMS
ABS
CAD
CAM
CNC
CO
CO2
CW
Er:YAG
FAC
HAZ
HeNe
LASER
LCD
LIS
MAG
MIG
MPE
N2
Nd:YAG
OEM
PC
PET
PVC
QC
R&D
SAC
SME
TIG
Tm-fibre
Yb-fibre
Acrylonitrile butadiene styrene plastic
Computer Aided Design
Computer Aided Manufacturing
Computer Numerical Control
Carbon Monoxide
Carbon Dioxide gas – used also as laser medium for mainly
industrial high-power use
Continuous Wave
Erbium-doped Yttrium Aluminium Garnet, laser medium mainly
for medical use
Fast Axis Collimation
Heat affected zone
Helium Neon laser
Light Amplification by Stimulated Emission of Radiation
Liquid crystal display
Laser Induced Super Plasticity
Metal Active Gas
Metal Inert Gas
Maximum Permissible Exposure
Nitrogen gas – used also as laser medium
Neodymium-doped Yttrium Aluminium Garnet, laser medium for
industrial, medical and scientific applications
Original Equipment Manufacturers
Personal computer
Polyethylene terephthalate plastic
Polyvinyl Chloride plastic
Quality Control
Research and Development
Slow Axis Collimation
Small and Medium Enterprise/s
Tungsten Inert Gas
Optical fibre with core doping of Tulium element, laser medium
mainly for medical use
Optical fibre with core doping of Ytterbium element, laser
medium mainly for industrial use
57
1 LASERS - THE WAY FORWARD
The capacity of lasers to generate new industrial solutions, new processes and to be
more financially viable has been proven. The first laser, produced by Theodore H. Maiman
on 16 May 1960 at the Hughes Research Laboratory in California, was a remarkable
scientific achievement, following four decades of effort and discovery. Maiman
introduced this new device to the world. He used the technique of shining a high-power
flash lamp on a ruby rod with silver-coated surfaces.i However, its introduction met with
some strong opposition. Charles H. Towner, who pioneered masers and lasers was
awarded the Nobel Prize for his efforts, in 1964, He reported that initially ‘many people
said to me—partly as a joke but also as a challenge—that the laser was "a solution looking
for a problem"’.ii
Figure 1. Dr Theodore H. Maiman and his scheme for a ruby laseriii
The introduction of the lasers was hampered by the complexity and fragility of the early
devices, often based on expensive and unfamiliar components. The barriers reduced as
the applications and versatility of lasers improved and expanded. More companies began
to produce lasers and more mechanisms were invented for laser light exploitation. More
novel products were produced that previously had not been possible and a virtuous circle
was set up, which turned what many had thought of as a scientific marvel into a
commodity.
The international market for lasers and their components is now very mature. Lasers
have brought a number of functions to everyday activities such as bar-code readers, DVD
and CD readers in computers, music/video players, screen pointers, pollution analysers
in towns and cities, and optical rulers and range meters, which have become universally
accepted.
Here we examine the current and future state of laser technology and point to areas
where developments in laser sources and applications could be effective and profitable
for SMEs and entrepreneurs looking to progress their business. As good information and
the capacity to forecast the economic evolution of an industrial sector is crucial in the
decision-making process, we hope that this work will be informative and improve
understanding of the present and future opportunities related to laser technologies.
2 ADVANCEMENTS IN LASER SOURCES AND PROCESSES
It is necessary to understand that envisaging a new application for laser technology is the
outcome of a series of questions deriving from the context of the application. The spur for
envisaging a new technique can include:
58
•
•
•
•
reducing processing times in order to increase production rates. This is
standard process-innovation;
exploiting a new interaction mechanism to improve the state-of-the-technique,
e.g. to reduce the side-effects of a welding process, or the heat transfer in the
drilling process of a delicate biological membrane;
improving general performance of a production system, e.g. by using a robotic
arm for laser beam delivery and operation in relatively small work stations;
reducing the cost of the production process by avoiding complex systems or
by reducing the space required for the production station or by significantly
reducing the costs of the process station, the power supply, the recycling of
associated components, or the disposal of production rejects.
Figure 2. Set-up for automated laser welding of luer-lock pipes for application in the production of sterile
components. In this case, the laser improves the welding because it enables a contactless process, with
high speed and full attainment of the product specifications. Think Laseriv (Italy)
To explain the role of the laser in an innovative production scheme, we need to focus on a
series of factors:
•
•
•
•
•
•
what process is the laser needed for?
what type of materials are used in the process and what are their
thermal/optical/chemical characteristics, in order to define the interaction
parameters?
what are the specifications for the laser source, in terms of wavelength, type
of operation, CW or pulsed, average/peak power, pulse duration, etc.?
what are the specifications for the system that guide the light to the point
where the process occurs?
what are the specifications for the optical system that delivers the radiation,
as the focusing unit or the collimator?
does the business plan for the laser solution indicate convenience with
respect to a traditional solution?
59
This last point has to be seen in the perspective of the expected lifetime of the new
technology, and an estimate of production development. It is separate from the technical
aspects listed, but equally important. In choosing the most appropriate laser technique,
the technical and economic experts need to have equal input.
Figure 3. The optical power of mounted bars has grown at a compound rate of about 15%. This may
continue towards the kiloWatt per bar5
2.1 LASER sources improve and become more available
The evolution of the laser market has provided opportunities for SMEs. In semiconductor
lasers, the price per watt has decreased from $2,000/W in 1987 to some $25/W in
2006 for high power bars,v and to some $6/W for fibre-coupled diodes, according to IPG
Photonics (Oxford, MA).vi These components are the basis of many laser applications and
are the pump sources for fibre lasers and most solid state lasers including versions of
Nd:YAG lasers.
In addition to decreasing costs, the capacity to generate more and more power (depicted
in Figure 4) has increased allowing reductions in the size of the laser source, making it
simpler and easier to mount on a compact station. Solutions once considered too
expensive for SMEs are now viable.
Below we review some laser source developments, driven by the research. We highlight
those that could be of interest to SMEs.
60
Figure 4. Structure of a semiconductor or diode laser, with indication of the layers required to obtain the
double heterostructure
2.1.1 Evolving laser source schemes
Developments in laser sources are aimed at increasing simplicity, wall-plug efficiency (the
ratio of emitted over absorbed power including chilling), reducing production costs and
maintenance requirements, and increasing ease of integration in process systems. In
most cases, these aspects have been addressed very effectively and to an extent were
unforeseen only ten years earlier.
2.1.2 Semiconductor power lasers
The high power semiconductor, or diode, laser is maybe the most important type of laser
component due to its versatility and reliability. Initial difficulties were related to the
thermal damage induced by absorption of the side of the laser beam inside the medium,
and the high dissipation resulting from the emission. The first aspect was addressed very
successfully by adding a near-transparent surrounding to the active medium, as depicted
in Figure 5, which shows the double heterostructure,vii which provides this
property.viiiImproved efficiency came from the remarkable progress made in the process
for manufacturing the layer structure, which resulted in a very pure laser medium.
61
Figure 5. Typical relation between the beam irradiated by a semiconductor laser near the emitting surface,
near field, and far away, the far field. Typical value of the near field size are 1 µm x few tens up to few
hundreds of µm, while the angular extension of the far field is about 50° in the fast axis (vertical in the
scheme) and a few degrees in the slow axis.
Laser beams are now very asymmetric, due to the large difference in the extension of the
laser’s gain medium in the direction normal to the junction and that parallel to it (see
Figure 6).
Figure 6. Single emitters semiconductor lasers, 6W CW out of a 200m x 1m active area. Emission available
at different wavelengths including 808 and 840nm. Footprint size is approx 6X10mm. Spectra Physics –
Newport (USA) www.newport.com
62
The direct use of the radiation is quite limited for the rapid spread of the radiation, which
causes a corresponding rapid decay of laser intensity along the emission axis. In order to
limit this phenomenon, a lens to reduce the fast axis divergence is often included in the
laser source. A second lens, which in some cases can be combined with the first, can be
introduced to achieve collimation of the slow axis. In the mid 1990s high power laser bars
began to be produced by combining a series of emitters (see Figure 7).
Figure 7. Typical arrangement of a semiconductor laser bar, with the parallel emissions from many emitters
A fast axis divergence lens can be used to collimate these emissions and exploit a system
for shared aperture component (SAC). Application of the radiation from the bars requires
equalisation of the beam parameter product (BPP) parameters along the slow and fast
axes.
Figure 8. High power (60W CW, 808nm) semiconductor laser bars: fast axis collimated (right) or not (left).
The difference is the cylindrical lens fixed in front of the emission area. The electrical connections are the
screws on top of the component. The footprint size is DILAS (D) www.dilas.de
The above described operation was achieved using different optical layouts. A solution
using the step-mirror design was introduced by Keming Du and co-workers at the
Fraunhofer Institute for Laser Technology, Aachen, Germany.ix A different but also very
effective solution exploiting micro lenses was introduced by the LIMO-Lissotschenko
Mikrooptik, Dortmund, Germany.x There are other schemes that use different geometries
of planexi or concave mirrors.xii
The technique for this power emission and handling using laser bars and beam shaping
optics has achieved several hundreds of Watts of power from a single fibre.
In applications where the process uses more than one wavelength, the combinations of
bars each emit on a different wavelength which are joined using dichronic mirrors. An
example of a beam combiner using high power bars is given in Figure 9.
63
Figure 9. A pair of wavelength-multiplexed stacks (each consisting of three sets of bars at different
wavelengths) is spatially offset by half of the bar separation for spatial interleaving. Spectra-Physics (USA)
and University of Southampton (Southampton, England)
The life of semiconductor lasers has increased by several orders of magnitude and
expected values in normal laser operations are now some 10-50,000 hours for
continuous-wave (CW) devices and several billion shots for pulsed lasers.
The future for semiconductor lasers looks promising:
-
the efficiency of radiation generation is increasing steadily. A US DARPA-funded
project, Super High Efficiency Diode Sources (SHEDS), is working on achieving
values of 80% of the ratio of electrical to optical power.xiii Several companies are
marketing a component with 60% efficiency, nearly 50% more than values two
years ago. In addition to reduced absorption in supply power, the high efficiency
enables reduced dissipation. Reducing the power of the cooler, and its size and
cost, makes thermal management of the source easier and cheaper. In addition to
the lower prices this will make many applications more attractive;
-
cooling of the laser sources bas been improved through a novel technique for the
transfer of heat from the laser active element and the exterior. For example, a
micro channel structure has been introduced,xiv to reduce thermal resistance and
deformation, improving laser operation;xv
-
the packaging of the laser bars is simpler and more compact. CW lasers of a few
Watts power have been produced using surface-mount geometry, which indicates
the direction towards the integration of the laser source inside the power supply
with a paramount change of the laser source concept. The diagram below (Figure
10) shows some early examples of this development, for fibre-coupled or free
space sources. The C-mount standard in the last picture is an evolution of the
single emitter laser with a reduced footprint of about 7x7mm.
64
Figure 10. Miniaturised power semiconductor lasers: the first and second with surface mount (TO 220
package) the last with a C-mount. Osramxvi (Germany)
Semiconductor lasers are eroding ever larger shares of the market for traditional solid
state lasers for industrial applications. Based on their intrinsic simplicity of operation and
rugged design, they are expected to expand in the future and especially in the context of
technologies for SMEs.
2.1.3 Fibre lasers
The high power fibre laser is a recent development in industrial lasers and has some
interesting characteristics. Its scheme is directly derived from devices in
telecommunication networks used to amplify optical streams of information along fibres.
This has eliminated the traditional scheme of detection, filtering and re-modulation of the
pulses in long distance data links.xvii
Figure 11. The scheme of a power fibre amplifierxviii
Figure 11 depicts a fibre amplifier, which is the core of the fibre laser. The illustration
shows the double-clad fibre, which is one approach to pump-core coupling: the pump
pulse is a laser beam on the wavelength of the absorbing band of the specific laser gain
element. This is usually focused on the external guiding structure of the fibre (green). The
blue core at the centre of the fibre is where the laser active element is positioned. The
optical pumping is achieved by the coupling of the pump radiation with the active core,
along the fibre, as shown in the ray representation. The amplified beam is emitted from
the core, with the divergence resulting from the guided mode. Other schemes were
demonstrated with interesting outcomes.xix The wall-plug-efficiency of high power fibre
lasers has achieved 25% value in the case of ytterbium core, operating at 1,080nm.
Figure 12 shows the complete laser, including the semiconductor pump lasers coupled
using fibre connections.
65
Figure 12. The fibre laser with several pump laser connected, to generate high power beamsxx
The powerful fibre laser is a synthesis of several independent achievements:
•
•
•
•
powerful pump power sources provided by fibre-coupled semiconductor
lasers;
development of new schemes for coupling the pump and the active medium;
introduction of reliable resonator mirrors inside the fibre, by means of
periodic modulation of the fibre refractive index, such as a Bragg mirror;
fabrication of high purity fibres, which reduce scattering and spurious
absorption. This is crucial for the increased power needed to control failures
in the components.
Progress in this type of laser has paralleled the progress made in photonic crystal fibres,
whose versatile design enables a variety of linear and non-linear optical effects.xxi
The most important characteristic of the beam generated by a fibre laser is its superior
brightness with respect to other sources of similar power. The internal core of the fibre
laser provides the laser radiation with a very regular (often near Gaussian) transverse
profile. The beam diameter in the fibre is similar to that in the core, which is a few
micrometers for low- to mid-power lasers up to about 100W, and from 50 to 100µm for
kiloWatt range lasers.
The table below indicates the laser elements, which are doped at the core for industrial
lasers and the corresponding wavelength range of the emissionxxii.
Element
Emission range
3+
ytterbium (Yb )
1.0-1.1 μm
erbium (Er3+)
1.5-1.6 μm, 2.7 μm
3+
thulium (Tm )
1.7-2.1 μm
This efficient and very small emissions area enables the radiation to be focused in order
to achieve higher intensities than obtained with solid state lasers of similar power. The
advantages are discussed below.
2.1.3.1
CW fibre lasers status and perspective
CW fibre lasers are improving in terms of the power emitted and in the variety of
wavelengths available.
As already mentioned, in order to increase the power, technological progress in fibre
construction, reduction of impurities, increased pump power and stability, coupling of the
66
pump to the core, etc. were required.xxiii The problems were related to non-linear
absorption and back reflection, due to the very high wave intensity inside the fibre, and
damage occurring at the interfaces, or the end face of the fibre.
The current CW fibre lasers are comparable if not superior, in terms of maximum power,
to traditional laser sources.xxiv Peak power can reach 50kW, according to IPG Photonics
(Oxford, MA), bigger than the most powerful CO2 sources. Figure 13 depicts a compact
source using a kW ytterbium fibre laser. The pump lasers for this Yb:fibre laser are a
series of modules of single emitter semiconductor lasers, that are closely arranged (see
Figure 14).
Figure 13. Pump module assembly for high power fibre laser. IPG (Oxford, MA)
67
Figure 14. High power fibre laser unit: assembly of the pump modules and the fibre resonator, IPG (Oxford,
MA)
68
CW lasers are likely to experience significantly improved performance and wider
application. The economic and technical advantages of these sources over more
traditional ones include higher efficiency, greater brightness or emitted power per unit
area of the emitter, and solid angle of emission, smaller size, and more convenient beam
delivery, via fibres that are tens or even hundreds of metres long. Their growth will cause
a reduction in the price per Watt, similar to that for semiconductor lasers.
Figure 15. A fibre laser oscillator in operation, Laser Zentrum Hannoverxxv (Germany)
2.1.3.2
Pulsed fibre lasers
Pulsed fibre lasers have not overtaken traditional Nd:YAG or CO2 lasers in terms of peak
and average power.
Figure 16. Pulsed fibre laser in Q-switched operation, typically for marking applications, IPG (Oxford, MA left), SPI (Southampton, UK - right)
69
The most popular application of pulsed fibre lasers is for marking surfaces, and for
resistor trimming, drilling of small holes and similar micromachining jobs.
The compact size of the source, combined with its rugged construction makes it a
candidate for low to mid power applications, about 20W, that require Gaussian profile
emitted beams. Another area of application is as a source of ultrafast duration pulses, i.e.
durations of sub-picoseconds (1 ps = 1 10-12 s) – or the femtosecond scale (1 fs = 10-15
s).
Figure 17. An ultrafast fibre laser (left) and the setup for its use in micromachining. Laser Zentrum
Hannover24 (D)
The technique used for the generation of these pulses is mode-locking, which is very
common in crystal lasers.7 The implementation of fibre into this technique is complicated
by the relatively low threshold or non-linear effects, which negatively influence
performance.xxvi
There is very little demand from industry for ultrafast sources. However, greater
understanding of the potential offered by ultrafast processes enabled by these sources is
expected to increase their application.
2.1.4 CO2, solid state, gas lasers
The CO2 laser, for many years has been the industry standard for metal cutting and
welding. Its technology is mature and can be considered the benchmark for comparison
with other newer sources.
Figure 18. KiloWatt size CO2 lasers. Semi-sealed type, left ElEn (Italy) and diffusion-cooled, right Trumpf
(Germany)
70
Large power systems are usually only used by the heavy industries; the several hundred
Watt to a few kiloWatt systems are the most attractive for SMEs. The demand for
advanced beam delivery for robotic welding, has highlighted the advantages of solid state
lasers such as the cylindrical-rod Nd:YAG laser. The pumping schemes in these types of
lasers are based on lamps that need to be replaced every few hundred hours of
operation, sometimes up to a thousand hours.
This type of Nd:YAG laser is the standard for several applications requiring tens to
hundreds of Watts of power. For SMEs with small to medium scale production, laser
technology has brought advantages and success in several types of applications.
Figure 19. Examples of state-of-the-technique station for manual welding and moulding repair, Sismaxxvii
(Italy)
For high power applications, these sources have been outperformed by a different type of
resonator, based on an active disc-shaped medium. These lasers are attractive in terms
of price per Watt for sources in the range of 1 to a few kW.
Figure 20. Principle of a kW Yb:YAG disk laser, pumped by semiconductor lasers. Rofinxxviii (D)
71
2.2 New interaction mechanisms
The developments in laser sources are continually extending the range of tools available
to laser applicators. The more direct effect of these developments is the reduced price
per Watt.
These new sources are spurring competition by reducing processing costs. However,
other interesting aspects are introduced with the sources, i.e. the power fibre lasers.
There are also other benefits which need some further explanation.
2.2.1 Exploiting a better beam quality
The description of the high power fibre laser shows the laser beam is emitted from a very
small active core. Numerical characterisation of the beam quality can be done by beam
parameter product (BPP), i.e. the product of the beam source size (the radius wo)
multiplied by the far field half-angle of the beam θf, based on the following equation:
BPP [ mm • mrad ] = θf • wo = λ [ μm ] • M2 / π
where M2 is the quality factor of the beam and λ is the laser wavelength.xxix The values of
interest to SMEs are plotted in the graph in Figure 21.
30.00
Lamp -Pumped
SS Lasers
BPP (mm x mrad)
25.00
BPP - CO2
BPP- Fiber Laser
20.00
15.00
Diode-Pumped
SS Lasers
10.00
Metal Cutting
5.00
0.00
0
2
4
6
8
10
12
14
Power ( kW)
Figure 21. Beam parameters product BPP as a function of emitter power for different laser sources, IPG
(Oxford, MA)
A low value of BPP produces a focus on a small spot, with high intensity on the irradiated
area. If the process is characterised by a threshold, e.g. in welding or marking processes,
a low BPP reduces the specification of the source power to accommodate this process.
This also reduces the area affected by the laser process. Therefore, a low BPP limits the
72
HAF of the material, and preserves the original structure of the sample. The advantages
of a low BPP are significant, and are the basis of current laser source developments.
2.2.2 Novel processes based on short pulses
The action of the laser pulse in the case of a surface process, such as marking or
trimming, is achieved in tens or one-two hundreds of nanoseconds. This is the typical
regime of operation in Q-switched lasers. A variety of sources may be effectively operated
in such a regime at different operational wavelengths.
Figure 22. Different finishing for cuts operated on a 1mm thick INVAR in the nanosecond regime, 8ns,
0.5mJ per pulse (right) and femtosecond regime 200fs, 0.5mJ per pulse (left) , Clarkxxx (Canada)
The investigation on the outcome of the process in the micrometre scale has shown that
in many cases it took place a significant interaction with the material close to the
processed zone. The reason for this is that in this time scale the thermal conduction may
induce a significant thermal cycle to this material, which results in evident
transformations and even formation of micro-cracks.
By repeating the above processes using sources emitting shorter pulses, as in the case of
the mode-locked laser generating ultrafast pulses, the results differ. The much shorter
pulse durations reduce the propagation of heat during the laser pulse, resulting in the
most efficient process. Ultrafast lasers have the fewest side effects and thus interest in
them is growing.
2.2.3 Improved versatility of laser sources
The change in technology from lamp-pumped to semiconductor-pumped lasers induced a
significant simplification of the laser source scheme and a reduction in its size and power
absorption. Fibre delivery of medium to high power beams allows the integration of a
laser source with a robotic arm or a similar device which operates on 3D targets.
Figure 23 depicts the final welding of the rear-light of a car, in which the curved profile
was successfully welded using a 35W semiconductor laser. The joint involved clear and
opaque thermoplastic moulded parts. The laser beam was focused by an optics freely
manoeuvred by a robotic arm. The light robotic arm is sufficient in this case; in the case
of the traditional mirror path, a much larger and more complex device would be required
73
Figure 23. Laser welded automotive light and particulars of the welded area, Think Laser (Italy)
74
3 HOW RESEARCH CAN INFORM SMEs
Here we highlight some areas of research that are likely to affect the laser market in the
future. From developments so far, it is clear that in the photonics area there is a very
close link between the laboratory and the market.
3.1 Direction of laser research
The general direction of laser research is towards extending the limits of the current
state-of-the-art. Lasers that are currently on the optical benches of research laboratories
will be available in the market in a few years, indicating the speed of improvement in the
power of commercial lasers, stability in terms of output power, etc. There is great interest
in the production of novel laser schemes, materials, pumping systems, operational
wavelengths and pulse durations.
Researchers in Italy have perfected techniques to generate and measure optical pulses
as short as 130 attosecondsxxxi (1 attosecond (as) = 1 10-18 seconds), thus for the first
time producing an artificial event shorter than the classical orbital period of the electron
in the hydrogen atom. The results of their work will likely be exploited to devise optical
tools for the remote controlled induction of chemical bonds, which could also have an
impact on industrial chemistry.
3.2 Some examples of future developments
A selection of results that could be of interest for future developments of SME-oriented
laser technologies are presented below.
3.2.1 Solar-pumped lasers
The idea of exploiting solar energy directly to energise laser pumping processes emerged
in the mid 1990s.xxxii However, its application has evolved only slowly.
Figure 24. Solar powered Cr-Nd:YAG laser
The growing interest in developing renewable energy sources and in more energy-efficient
processing, prompted a Japanese research group led by Prof. Yabe of the Tokyo Institute
of Technology to develop a laser pumped by solar radiation, used to induce an energy
75
cycle without the use of fossil fuel.xxxiii Figure 24 depicts the system, which produced a
laser output of 24.4W with a 1.3m2 Fresnel lens collecting solar light.xxxiv The researchers
claim that the system could achieve kiloWatts of laser output with a solar collector of
some 7m2.
This type of source could be used in many applications working flexibly according to the
available solar energy Figure 24
3.2.2 Versatile microchannel drilling in transparent media
Microstructures in transparent media are required for many applications, such as microfluidics, drug-deliverys, micro-motors and filtering of liquids. The interaction of ultrafast
pulses with doped glass enables the engraving of optical guides on glass. The research
group at the ULTRAS Laboratories in Milan, Italy, have produced such a guide on laser
active glass.xxxv
Figure 25. Fabrication of microchannels in fused silica with circular cross section femtosecond pulses, (a)
end-face microscope image of a row of microchannels and (b) SEM image of one of them.xxxvi
A further development involved producing a clear channel, a few tens of microns in
diameter, in the glass, again with free choice of the shape and intersection of the
channels.
This technique opens the possibilities for biophotonic devices integrating microfluidic
channels and optical waveguides in three-dimensional configurations incorporating novel
features.
3.2.3 The silicon laser
The possibility of transmitting information with light is limited by the emitters, lasers and
LEDs, which are made of different materials from the usual silicon information
processors. Direct laser emission from silicon are impaired by physical properties and
consequently research into methods to make silicon-based devices suitable sources for
short pulses is very active.
Researchers at the University of California, Santa Barbara (UCSB) have produced a laser
structure on a silicon wafer,xxxvii which produces picosecond pulses at high rates of
76
repetition, which is the essential characteristic of a source for integrated information
processing.
Figure 26. Scheme of an ultrafast silicon laserxxxviii
An electrically pumped, mode-locked evanescent laser on silicon has achieved four
pulses at multiple infrared wavelengths accompanied by 40GHz repetition rates. This
demonstrates that silicon lasers could significantly reduce the cost of lasers in numerous
integrated-circuit applications, and is promising for a wide number of applications.
77
4 CONCLUSIONS
The price per Watt of laser light has been steadily decreasing and it is reasonable to think
that this will continue into the future.
The advantages of lasers in manufacturing are manifold: many applications using lasers
show better quality, higher productivity and more opportunity for processing.
This report has demonstrated that there will be new opportunities in the near and longer
term future for entrepreneurs.
78
REFERENCES
Reference books on lasers and optics:
1.
2.
3.
4.
5.
O. Svelto, Principles of Lasers, 5th ed., Plenum Press 1999.
W. Koechner, Solid-State Laser Engineering, 6th ed., Springer 2006.
A.E. B. Saleh and M.C.Teich Fundamentals of Photonics, John Wiley Series in Pure
and Applied Optics 2007.
A. Siegman, Lasers, University Science Books 1986.
E. Hecht, Optics, 4th ed., Addison-Wesley 2001.
General books on laser applications
W. M. Steen, Laser Material Processing, 3rd ed., Springer 2005.
D. Schuoeker, High Power Laser in Production Engineering’, World Scientific, 1999.
J. Powell, Laser Cutting , Springer 1998.
Laser Institute of America LIA Handbook of Laser Materials Processing, Magnolia
Publishing 2001.
W. W. Duley, Laser Welding, John Wiley 1999.
In the indication of the references, the number in bolt type is the volume number and the
following one is the initial page of the article.
i
Theodore H. Maiman, Stimulated Optical Radiation in Ruby, Nature 187, 493 (06 Aug
1960).
ii Charles H. Townes, The first laser, from A Century of Nature: Twenty-One Discoveries
that Changed Science and the World, Laura Garwin and Tim Lincoln, editors. The
University of Chicago Press, 2007.
iii http://timeline.aps.org/APS/Timeline/Middle.cfm?EventID=109
iv Ch. 10 of W. M. Steen, Laser Material Processing, 3rd ed., Springer 2005 and
www.thinklasersrl.com
v M. Apter et al. High-power diode-laser bars come of age,
http://www.laserfocusworld.com/articles/250394.
vi T. Hausken, Battle heats up between bars and single-emitter diodes,
http://www.laserfocusworld.com/articles/266396.
vii R. Diehl, High Power Diode Lasers, Springer 2000.
viii O. Svelto, Principle of Lasers, 5th Ed., Plenum Press 1999.
ix K. Du, M. Baumann, B. Ehlers, H.G. Treusch, P. Loosen, ‘Fiber coupling technique with
micro step-mirrors for high-power diode laser bars’, OSA TOPS, 10, 1997.
x www.limo.de
xi S Bonora and P. Villoresi, Advanced optics expand the applications of high power diode
lasers, http://spie.org/x8699.xml and S. Bonora and P. Villoresi, Diode laser bar beam
shaping by optical path equalization, J. Opt. A: Pure Appl. Opt. 9 441 (2007).
xii S. Bonora, Compact beam-shaping system for high-power semiconductor laser bars, J.
Opt. A: Pure Appl. Opt. 9 380 (2007).
xiii http://www.darpa.mil/MTO/Programs/sheds/index.html
xiv http://www.ilt.fraunhofer.de/eng/ilt/pdf/eng/products/Heatsinks.pdf
xvhttp://www.laserfocusworld.com/display_article/255508/12/none/none/OptMN/Micr
ochannel-cooling-ups-power-capacity-for-laser-diode-bars
xvi http://catalog.osram-os.com/
79
E. Desurvire et al., Erbium-Doped Fibre Amplifiers, Device and System Developments,
Wiley-Interscience, 2002.
xviii C. Crossland, Thulium Puts Power Behind Eyesafe Fibre Lasers, NASA Tech Briefs,
March 2007, and http://www.nufern.com/.
xix A Tünnermann et al., The renaissance and bright future of fibre lasers, J. Phys. B: At.
Mol. Opt. Phys. 38 S681, 2005.
xx V. Gapontsev et al., 2kW CW ytterbium fibre laser with record diffraction-limited
brightness, Proc. Convergence on Lasers and Electro-Optics/Europe, Munich, Germany,
2005 p. 508. and http://www.ipgphotonics.com/
xxi J. C. Knight, Photonic crystal fibers and fiber lasers, J. Opt. Soc. Am. B 24, 1661 (2007)
http://www.opticsinfobase.org/abstract.cfm?URI=josab-24-8-1661
xxii Rare-earth-doped fibers, Encyclopedia of Laser Physics and Technology, http://www.rpphotonics.com/rare_earth_doped_fibers.html
xxiii J. Limpert et al., 500 W continuous-wave fibre laser with excellent beam quality,
Electronics Letters 39 645, 2003.
xxiv Y. Jeong et al., Ytterbium-doped large-core fiber laser with 1.36 kW continuous-wave
output power, Opt. Express 12, 6088 2004,
http://www.opticsinfobase.org/abstract.cfm?URI=oe-12-25-6088
xxv http://www.laser-zentrum-hannover.de/en/fields_of_work/laser
_development/fiber_laser.php
xxvi G. Agrawal, Nonlinear Fibre Optics, 4th ed., Elsevier 2006.
xxvii Ch. 4 of W. M. Steen, Laser Material Processing, 3rd ed., Springer 2005 and
http://www.sisma.com/
xxviii http://rofin.de/english/products/macro-laser/nd-yag-solid-state-lasers/disc-disklaser-principle.php
xxix Ch 2 of W. M. Steen, Laser Material Processing, 3rd ed., Springer 2005
xxx http://www.cmxr.com/Industrial/Handbook/Chapter4.htm
xxxi G. Sansone et al., Isolated Single-Cycle Attosecond Pulses, Science 314 443, 2006.
xxxii NREL Researchers Use Sunlight to Power Laser
http://www.nrel.gov/news/press/1995/solar.html
xxxiii T. Yabe et al., Demonstrated fossil-fuel-free energy cycle using magnesium and
laser, Appl. Phys. Lett. 89 261107 2006
xxxiv T. Yabe et al., High-efficiency and economical solar-energy-pumped laser with
Fresnel lens and chromium codoped laser medium, Appl. Phys. Lett. 90 261120 2007.
xxxv S. Taccheo et al., Er:Yb-doped waveguide laser fabricated by femtosecond laser
pulses, Optics Letters 29 2626 2004
xxxvi V. Maselli et al. Fabrication of long micro-channels with circular cross section using
astigmatically shaped femtosecond laser pulses and chemical etching, Appl. Phys. Lett.
88 191107, 2006
xxxvii M. Sysak et al., Experimental and theoretical thermal analysis of a Hybrid Silicon
Evanescent Laser, Optics Express 15 15041 2007
xxxviii B. Koch et al., Optics Express 15 11225 2007.
xvii
80
81
INTERNATIONAL CENTRE
FOR SCIENCE AND HIGH TECHNOLOGY
82