plastic welding instructions

Transcription

PLASTIC
WELDING
INSTRUCTIONS
Toll Free: 800-289-7505
Local:
401-683-3199
Fax:
401-683-3177
www.malcom.com
All Rights Reserved Malcom Company Inc.
www.malcom.com
MALCOM TECHNOLOGIES
207 High Point Ave. Unit 7B
Portsmouth, RI 02871
Table of Contents
Introduction
Welding Thermoplastics
Preparation for Welding
Types of Welds
Tacking
Pendulum Welding
Speed Welding
Ribbon Welding
Plastic Welding Repairs
Surface Preparation
Making the Welding Groove
Tack Welding
Welding Damaged Area
Welding PVC, PE or PP Pipes
Inserting a Riser
Making a Bell End
Leak Repair
Mirror Welding
Fabricating and Repair of Thermoplastic Lines and Tarps
Types of Weld on Flexible Lines
Welding Defects and Causes
Special Instructions for Specific Material Types
Frequently Asked Questions
Leister Plastic Welding Tools and Accessories
Help
References
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INTRODUCTION
If you are new to thermoplastic welding, rest assured that it is a simple process. Thermoplastic welding has been
successfully used for over 30 years. It is a process that most people can learn to do in a very short time. Many
products today are made with thermoplastics. Up till now there has been no simple means for repairing these
plastics. The Malcom plastic welding kit has all the tools needed to perform most plastic welding repairs and
fabrication work.
Information in this instruction booklet came from various sources including, Leister training programs that Malcom
Company employees attended in Switzerland, trade journal articles and reference manuals listed in the back of this
booklet (see page 25) and years of experience welding plastics.
There are many ways to weld plastics such as, hot plate, friction, vibration, hot gas and ultrasonic. Hot gas,
otherwise known as hot air welding, is the method that is used with the Leister tools and these instructions will
instruct you on how to do hot air welding.
In order to weld plastics, you must first have some basic understanding of what plastics are (see page 17), the
various types of welds commonly used (see page 4) and an understanding of the differences of tack welding,
pendulum welding and speed welding (see pages 5, 6 and 8). The Plastic Welding School plastic welding
instruction booklet is a basic training book that will help you understand what plastics are, the basics of welding
plastics and how to fabricate and perform plastic repairs (see page 10).
Only through practice welding will confidence be achieved to begin fabrication and perform repairs. Fabrication
and repairs of tanks, liners and structural items should be done only after practice welding and successful tests of the
welds have been achieved. Like metal welding, plastic welding takes some practice, but once learned, it is a simple
process. When you purchase the Malcom Plastic Welding Kit and you need additional help beyond this instruction
booklet, help is only a phone call away by simply calling our toll free number.
1-800-289-7505
www.malcom.com
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MALCOM TECHNOLOGIES
207 High Point Ave. Unit 7B
Portsmouth, RI 02871
Tele: 800-289-7505
WELDING THERMOPLASTICS
According to DIN 1910, part 3, (DIN = Deutch Industrial Norm, a German Standard) plastic welding is the joining
of thermoplastics using heat and pressure. The joined surfaces must be in a thermoplastic condition (soft and
pliable), not melted. Once plastic is melted, the molecular composition changes and the joint will become weak.
With the Leister tools hot air is used to precisely heat the plastic. Plastic welding can be done with or without
additional materials.
The necessary conditions for welding are:
1. A plastic joining area.
2. The merging of the plastic materials.
3. A heat source. (Leister tools)
4. The coordination of the process of the most important factors of heat - pressure - time
5. Only plastics that are thermoplastics can be welded and only like thermoplastics can be welded.
Each thermoplastic has a particular melting temperature and viscosity, therefore, it should be noted that only the
same thermoplastics could be welded to each other. Some thermoplastics, on account of their very high molecular
mass, do not achieve a sufficient ability to flow and cannot be welded. The ideal welding temperature varies
between the various types of plastics. The Leister tools allow you to dial in the correct temperatures of the various
plastics that you may encounter.
PREPARATION FOR WELDING
The welding base material must be prepared for welding. Many variables affect the type of weld to be used and the
type of weld is often determined by the person actually doing the welding. Repair welds are prepared differently
than for fabrication welding. However, in most cases, a groove must be made with a cutting devise (saw, router,
plane) in the base material where the weld is to take place.
Butt welds, edge welds and corner welds. Typically a 30° angle is beveled on both parts. This angle and
size of the bevel will depend on the welding rod you will use and the thickness of the base material. (See drawings
on page 4.)
Overlap Welds and Fillet Welds. These types of welds require little preparation since the parts to be joined
are placed on top of each other. (See drawings on page 4.)
On all types of welds, both surfaces to be joined must be free of all dirt, dust, oil, moisture and loose particles. Wipe
the edges off using a clean cloth. Do not use solvents. In the case of material that oxidizes (PP and PE materials),
removal of the oxidized surface must take place by means of scraping, grinding or sanding just before the weld is to
take place. Do not let the prepared parts sit longer than a few minutes prior to doing the welding because of
oxidation?
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TYPES OF WELDS
Outlined below are drawings of typical welds that are made with triangular and round welding rods. Note how the
base material has been prepared for the weld allowing a groove for the welding rod to fill into.
Butt welds, note V groove preparation
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Note angle of prepared areas for the welding rod on these various types of welds.
TACKING
After the parts have been prepped, they then need to be tacked together prior to welding so that they will not move
during the welding process. This is done with the Leister tacking tips. Basically, the parts are held in place and the
tacking jet is run along the seam. Tacking can be done either continuously or in spots dependent on the length and
structure to be welded. It is only tensile strength. Tacking eliminates clamps, jigs and additional labor.
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PENDULUM WELDING
The basic type of plastic welding is pendulum welding or hand welding. This type of welding provides the
beginner with a chance to determine the correct balance of heat, pressure and speed required to produce a good
weld. The round 5mm tip that comes with the Leister plastic welding tool is used for this type of welding. For
beginners, we recommended pendulum welding be used first as a means of practice in learning how to weld plastics.
A welding rod is required for pendulum welding. The rod is held in one hand while the hot air tool is held in the
other hand. If you are right handed, hold the rod with your left hand and the tool with your right hand. The rod is
led by hand. The method of pendulum welding is very well known and it is possible to learn this technique in a
short time.
The sequence of pendulum welding is as follows:
1) The welding rod is held with its end in the carefully prepared welding groove and at an angle of 90° to the grove.
(45° for polyethylene and fluorocarbons). The welding zone is heated with the moving of the hot air stream up and
down heating the rod and base material. A good start is very important. Most welds fail at the starting points. For
this reason, for multiple pass welds, stagger the starting points.
2) The hot air is directed partly at the welding rod and to a greater extent, into the groove with a pendulum
movement (from top to bottom, not in a circle) about 1/4" to 3/4" from the material to be welded. At the same time
the hand must exert even pressure of about five pounds on the welding rod. When it starts to form a bead along the
edges of the rod, move the tool along keeping the bead visible along the edges of the welding rod.
3) Three very important things must be known: a) Correct temperature setting (this can be set very reliably on the
electronically regulated hot air welding tools of Leister), b) steady welding speed and c) even downward pressure on
the welding rod. When these three factors are in correct relation to one another, a slight foamy wash will be formed
along the weld, but this wash must be neither brown nor black as it means degradation has occurred. A clean wash
is a necessary sign of a good weld. (See the photograph of pendulum welding on the next page.)
4) Once the weld has started, the hot air tool should continue to fan from the rod to the base material. Concentrate
on the base material about 60% of the time when using 1/8" rod and approximately 40% of the time with 5/32 rod.
Average welding speed is 4" to 6" per minute.
When you change your grip as you weld, be sure that the pressure on the welding rod does not change or you could
end up with a weak spot in your weld. When finishing a weld, hold the pressure on the rod till it cools. If you are
going to continue the weld after you stop, cut the rod at a 30° angle then cut the new rod at a 60° angle. When you
start the new weld, heat the two cut angles and join them together. Never splice welds by overlapping side by side.
When doing multiple passes, caution should be taken so that you do not overheat the entire mass resulting in a bad
weld. You may need to let the weld area cool between welds. Pendulum welding is often used where cracks or
splits pass through tight corners.
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Below is a drawing showing the angle of the welding rod during pendulum welding, as well as the movement of the
hot air tool during the welding process.
PENDULUM WELDING
Illustration of the wash created by pendulum welding of hard PVC with
5mm profile rod
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SPEED WELDING
When welding with the speed welding nozzles, the welding rod is inserted into the welding rod guide and is put into
plastic condition together with the base material in the pre-heated chamber. What this means is the base material
and rod is heated to the correct temperatures simultantiously because of the tip design. The pressure is also applied
on the welding rod by hand or with the tool dependant on what tip you are using. The speed tip design is such that
allows for better pre-heat and this effects the welding speed which is several times higher than with pendulum
welding. Average speeds for speed welding are about 40" per minute for PVC and 24" to 30" per minute for
polypropylene and polyethylene.
The photograph below shows speed welding with the push-on speed welding nozzles for round and profile rods. By
using these speed-welding nozzles with the appropriate size of welding rod profiles and by increasing the volume of
hot air on the groove and welding rod, the welding process can be considerably speeded up. Profile welding ("V"
rod) with speed welding nozzles results in welding speeds 10 - 15 times greater than pendulum welding with several
layers of round rod.
The mark of a good weld is the welding bead on both sides of the welding rod.
1. Prep the welding rod. Cut the end to a pencil point using a trimming knife or side cutters.
2. Fit the proper speed welding tip to the hot air tool nozzle and allow it to heat up for a few minutes.
3. When ready to start hold the hot air tool 3" from the base material perpendicular from the base material. Insert the
weld rod into the nozzle until it protrudes through the end by 1/8 inch. The protruding rod must be held beyond the
start of the V grove so that the heat is directed onto the start point for welding. Immediately place the tip of the
welding tip on the material at the starting point. Then apply pressure on the rod with your other hand and pull the
hot air tool towards you.
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4. Hold the tool so the speed welding nozzle base runs along the crack parallel to the surface. In the first few inches
of welding, pressure should be made on the welding rod with your hand. With the Leister push fit tips you should
maintain pressure on the welding rod throughout the weld. You can also apply some pressure with the hot air tool to
give you the smooth and uniform appearance to the weld. If you use a Leister automatic draw tip (part #26), the rod
will feed automatically once the weld has been started and at the correct angle.
5. When the surface plastic shows signs of slight glossy surface, move the welding nozzle along the groove. The
nozzle tip should rest on the rod in the groove while leading edge of the base of the tip there should be an air gap of
3mm. Feed the rod steadily into the nozzle with a downward hand pressure of about 5 pounds - sufficient to push
the softened rod into the grove. (Do not apply downward force to the weld via the hot air tool itself unless you are
using the Leister automatic draw nozzles.)
6. Correct mating between the welding rod and the material occurs when the rod is seen to soften and the new rod
moves down the nozzle feed. As the rod melts into the groove, two smooth continuous ridges will appear at the
edges accompanied by a slight wash at the sides of the weld. The angle that the tool is held to the base material
determines how fast you can weld. Changing the angle changes the preheat airflow which changes the rate of
speed. The preheat hole must always be in line with the direction of the weld. The welding speed should always be
at a fairly constant rate of speed. The hot air tool cannot be held still or you will burn the plastic.
7. When the weld has been completed, remove the hot air tool sliding the nozzle off the remaining welding rod. It
would be advisable to clean the welding tip as needed to assure a smooth airflow in the preheat chamber as well as a
smooth movement of welding rod.
Below are drawings of the speed tip and the welding rod positions during the welding process.
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RIBBON WELDING
Leister makes tips for strip or ribbon welding using a welding ribbon usually 1/2" by 1/16". The ribbon is applied
along the seam accordingly to form a weld. Ribbon is often used for doing repairs as a way to hold the broken parts
together while the weld is being made. Welding ribbon can be obtained in many sizes through The Malcom
Company.
PLASTIC WELDING REPAIRS
A step-by-step overview for repairs to plastic parts on trucks, campers, autos, RVs, motorcycles
and plastic boats.
Plastics are used everywhere now including automobiles, motorcycles, trucks, boats, computers, tanks and
containers, liners, furniture, vinyl materials, rafts, tents, tarps, roofs, floors, toys, storage bins, appliances, ventilating
duct work, you name it. Often these plastic 'things' need repair or need modification. Leister hot air tools are ideal
for doing repairs in the shop and in the field.
The only equipment needed can be found in The Malcom Company Plastic Welding Kit, which includes a hot air
tool, welding tips, welding rod, instructions, various hand tools for preparation, etc.
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The Malcom Plastic Welding Kit.
Preparation is the key in repairs. Before any repair work can be done, it is necessary to determine the type of plastic
to be welded. To run a test, take a small sample of the material to be welded and flame test it with a match.
Observe the flame and notice the smell it gives off. See the Leister Leaflet 21A back page. For an additional test,
make a small test weld on a similar piece of plastic. If the weld is strong, the correct welding rod is being used.
Always wait for the weld to cool before testing. The weld becomes stronger as it cools. Some manufacturers stamp
the material with identification codes.
SURFACE PREPARATION
Plastic vehicle body components can be repaired from either side based on how easy it is to gain access to the repair
area. With access to the backside of the part, reinforcement type welds can be applied for added strength. Clean off
any dirt and oil in the repaired area. If the part is painted, the paint must be removed as well.
MAKING THE WELDING GROOVE
At the end of each crack, a small hole must be drilled (1/8") to stop the crack from expanding. Next a 90 ° V shaped
groove must be prepared along the crack to allow for the welding rod that will fill in the crack. Begin and end the
groove about 1/2 inch beyond the crack. When the groove is finished the welding rod that will be used in the repair
should fit into it with a bit protruding over the top, about 1/16" This allows for proper penetration for the rod into
the groove and will eliminate the need to fill any low spots.
TACK WELDING
The next step is to tack weld the base of the damaged area. Tack welding holds the parts together so that they will
not move during the welding and filling in of the crack. Use the Leister tacking tips #28 or 10M. The tacking tip
should be held so that its pointed end is in contact with the material running along the entire length of the grooved
out area. The base of the welding tip should be about 20° off the plastic material.
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As the nozzle is drawn down the crack, the plastic is softened and the tip draws the softened materials together.
Avoid applying pressure to the tacking tip because the material is thin at the bottom of the groove that was prepared.
Misalignment of the part can be corrected by holding the sections together during the tacking process. Always clean
the tacking tip off when you are finished with it.
WELDING THE DAMAGED AREA
Much of the technique of the welding process has been reviewed earlier in the instruction book. Please review this
section now (see page 5). The welding can be done with either the pendulum or speed welding method. Begin the
operation with cutting the tip of the welding rod into a point. Then fit the proper tip onto the hot air tool and set the
correct temperature for the type of plastic and let the tool heat up for at least three minutes, then begin to weld.
When the welding has been completed and allowed to cool completely, the welded area can be cleaned up and
painted if desired. Using a scraper, plane, file or a sander, smooth the area. Often the area can be heated again with
the hot air tool to smooth over any rough surfaces that was made by the scraper, file, sander or plane. If painting is
desired, follow the paint manufacturers directions for surface preparation.
WELDING PVC, PE OR PP PIPES
The welding surface must be clean. Set the temperature on the welding tool to 300° C using a high fan setting and
allow 3 - 4 minutes to reach temperature. When repairing a crack, stop drill the end of the crack. Make a V groove
in the crack, clean the welding surface using the scraper, tack weld the crack before adding additional material to the
damaged area. Use the tacking jet nozzle # 28 or #10M.
Use the 5mm standard nozzle to tack triangular PVC rod to the end of the crack. Holding rod at a 90° angle to the
crack, concentrate the hot air stream onto the joining area of the rod and the damaged surface. Exert pressure on the
rod so that the melted plastic is forced down into the crack for a proper bond. Fill the crack. Repeat this method if
needed to completely fill the crack. Cut away excess rod. For large cracks, speed welding is the preferred method.
INSERTING A RISER
Drill an appropriate sized hole into the pipe. Clean the surface. Insert a riser till stable but not enough to restrict
flow. Pendulum welds the two pipes. Repeat weld as many times as necessary.
MAKING A BELL END
Remove any nozzle on the hot air tool. Rotate the pipe while heating so that the entire pipe end is consistently
heated. Push the heated pipe over the end of the same sized unheated pipe. If necessary, pendulum weld the end of
the exterior pipe onto the interior pipe.
LEAK REPAIR
Pin holes in bell ends, flanges and couplings, pendulum weld a small piece of rod over the hole. Push the excess rod
into the hole using the flat side of a screwdriver. Large holes stop drill the ends of each crack leading away from the
hole. Make a saddle to fit over the hole and weld into place.
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MIRROR WELDING
Mirror welding, also known as hot plate welding, is often used in pipe welding and profile welding of various types
of plastics. In mirror welding, two plastic parts are placed up against a hot plate and heated for a specified time at a
specified temperature. They are then removed from the plate and pushed together under pressure and held in place
for a specified time to cool and form the weld. These types of welds are very strong.
Leister manufactures many types of welding mirrors that fit onto the hot air tools. The Malcom Company also
imports a full line of welding mirrors from Italy manufactured by Tecnodue. Please ask your sales rep for further
details of these tools.
FABRICATING AND REPAIR OF THERMOPLASTIC LINERS AND TARPS
This would include tarps, tents, banners, pond liners, tunnel liners, landfill liners and caps. In addition, liners are
often used to line areas in a plant where toxic chemicals are housed and for lining tanks. These types of liners are
flexible and often reinforced. They can be welded with the Leister tools by overlapping the materials and inserting a
flat hot air tip between the overlap. While moving the tool along, apply pressure from the top with a roller. Some of
these liners can be welded with a welding rod as well. Many types of tips for this type of welding are available and
shown below.
For repairs, small patches can be cut out of the same material. When cutting patches, make them about 1" larger
than the damaged area and be sure to round off all the corners. Next, install the Leister wide slot nozzle onto the hot
air tool, set the desired temperature and let the tool warm up. Move the patch in place and hold down with roller in
the center of the patch. Insert the hot air tool between the patch and the base material and simply tack the center of
the patch in place.
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This prevents the patch from moving during the repair welding. This repair must be done against a hard surface.
Once the tack is made, start on the outside of the patch moving the hot air tool around the outer edge with the
pressure roller following it applying pressure.
Move the roller from the inside of the patch to the outside. Continue this around the circumference of the patch until
it is welded into place. We recommend that you practice this technique with some extra material prior to your first
attempt on doing a repair.
Fabrication of tarps and liners uses the same method. However, instead of a patch, you overlap the two pieces of
material where you want to weld by about two inches. Insert the nozzle in the overlap area and with the pressure
roller; apply pressure along the entire length of the seam. Malcom offers a Leister automatic welding machine that
will do these types of welds very consistently and you may want to consider this machine if you have a lot of
welding to do.
Welding a PVC-coated Army tent material with Leister HotJet S. Everything made of PVC
Polyethylene, poly-propylene and ABS, can be welded or repaired with the Leister Hand Held Hot Air Tools.
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TYPES OF WELDS ON FLEXIBLE LINERS
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WELDING DEFECTS AND CAUSES
DEFECT: Poor weld penetration or poor bonding
CAUSE: Improper or superficial preparation of the welding area.
Speed of welding was too fast or the temperature was too low.
The weld was made with dissimilar materials.
DEFECT: Uneven weld bead width
CAUSE: Welding rod was stretched.
Irregular pressure on the welding rod
DEFECT: Carbonized welding
CAUSE: Welding speed too slow
Welding temperature too high
DEFECT: Warping
CAUSE: Overheated repair area
Parts fixed under tension
Poor site preparation
DEFECT: No wash or bead is visible
CAUSE: Welding speed too fast
Temperatures too low
DEFECT: Low and deformed weld
CAUSE: Too much pressure has been applied to the welding rod.
Rotary burr was not correctly positioned during preparation.
SPECIAL INSTRUCTIONS FOR WELDING VARIOUS TYPES OF MATERIALS
PVC
When welding PVC, holding the tip 1/4” from the material and counting off four seconds may easily determine the
correct temperature. At four seconds the material should show a faint yellowish tinge. Adjust your temperatures
accordingly to achieve the desired results. With PVC, a good finished weld will appear uniform with no brown or
black discoloration. If insufficient heat has been applied, the rod will appear in its original form and can be easily
pulled back from the base material. Look for small flow lines on either side of the bead. Welding temps are around
400-450°F
There are two types of PVC materials, normal and high impact. High impact of type II PVC is modified with rubber
to increase impact resistance. Welding temperatures of this type is lower than normal type 1 PVC. Be sure that you
use the correct welding rod for the type or PVC you are welding.
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PE
There are two types of PE for industrial use, branched and linear or high density. The linear is more rigid and higher
temperature material. Both types have a tendency to degrade in sunlight and oxidize in air. The welding rod must
be of the same type of PE material. Max weld strength for PE materials is obtained 10 hours after the weld is
completed. PE is susceptible to stress cracking as well over time and you must consider this when selecting the
types of materials to use. With PE materials, an overheated weld will produce a flat bead with oversized flow lines.
PE materials become transparent when overheated like candle wax.
PP
Very similar to PE. It is linear and it is susceptible to stress cracking and oxidation. With PP materials, an
overheated weld will produce a flat bead with oversized flow lines. PP materials become transparent when
overheated like candle wax.
Acrylic
Similar to PVC in how it is welded. Acrylic was one of the first plastics to be welded in the 1940's in Germany to
repair airplane windows. Most acrylics can be welded to PVC. Care must be taken to not to char the material during
the welding process. Welding temps for acrylic are 500 - 550°F
FREQUENTLY ASKED QUESTIONS
Below we have some answers to frequently asked questions that you will find helpful in understanding the plastic
welding process using Leister welding tools.
WHAT ARE PLASTICS?
Plastics are not natural products; plastics are man-made, produced by a chemical process. Plastics are developed for
particular applications. The plastic molecules can be arranged in many ways to form various types of plastics like
Thermoplastics, Duroplastics and Elastomers (rubber). The specific properties of each type of plastic are defined by
how it is made or its "recipe" (the molecular construction, its molecular arrangement, the length of the
macromolecule and additives).
We are interested in thermoplastics because they are the only type that can be welded and formed with heat.
Thermoplastics change into a plastic condition with heating and keep their shape after cooling. After cooling, the
Thermoplastic returns to its original hard and firm state. Thermoplastics can be heated and cooled over and over
again.
A Duroplastic and a Elastomer cannot be welded without it being mixed with a thermoplastic. Duroplastics are
plastics that are hardened with heat. The shape of the plastic cannot be changed with heat. They are temperature
resistant and cannot be welded. Elastomers are plastics that can be formed with heat. Rubber is an elastomer.
Elastomers cannot be formed by melting and cannot be welded.
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WHY ARE PLASTICS BEING USED MORE FREQUENTLY TODAY?
Some of the more important reasons plastics are used more today are: Low weight with good mechanical qualities,
good electrical insulating ability, excellent resistance to chemicals and weather and low thermal conductivity.
Plastics offer varied processing possibilities. Plastics can be easily cut, filed, formed and connected. Many of the
techniques which are used for wood and metals can also be applied to plastics.
A good chemist can make a plastic for any application. In today's world, not only is plastic being used more, but
also new plastics are being made everyday. The welding characteristics of thermoplastics today vary greatly, so
plastic welding tools must be flexible yet very precise to weld these new thermoplastics properly.
HOW ARE PLASTICS MADE INTO A FINISHED PRODUCT THAT CAN BE PROCESSED FURTHER
BY THE PLASTIC FABRICATOR?
The main function in the manufacturing of plastics is in the mixing and kneading of various components of filling
materials, colors, plasticizers and lubricants. It is all based on a recipe that the chemist develops for particular
applications of the end product. Once the proper mix is obtained, the pellets are fed into an extruder or molding
machine and out comes the raw plastic, often ready for additional processing.
The most common methods for further processing of plastics are: pressing, molding and calendaring. The standard
forms of plastics which are utilized are, sheet stock, profiles, bars, rods, tubes, foils, pipe fittings, etc. For example,
from the extruder the material is made into a sheet stock, the sheet stock is sold to a fabricator who may form, mold,
shape or cut and weld the material into an end product.
HOW DO YOU RECOGNIZE THE DIFFERENT PLASTICS?
In order to work with plastics, it is necessary to determine what the material is. Different recognition methods are
used for determining what the plastic is. The most common one is the flame test. (See Leister Leaflet 21A for
details). Also on the market is a chemical test. Some plastics are clearly marked with the standard symbols listed
below:
PVC-P polyvinylchloride soft
PVC-U Polyvinylchloride hard
PE-HD Polyethylene high density
PE-LD Polyethylene low density
ECB Ethylene-Copolymer-Bitumen
EVA Ethylene-Vinylacetate-Copolymer
EPDM Ethylene-Propylene-Terpolymer-Rubber
ABS Acrylnitrile-Butadiene Styrene-Copolymer
PA Polyamide
PC Polycarbonate
PMMA Polymethylmethacrylate
PP Polypropylene
PS Polystyrene
PTFE Polytetrafluorethylene
PUR Polyurethane
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So that you can recognize which plastic you are dealing with, the following simple test is recommended:
1. A short test weld with the available welding rod. If the welding rod is fixed firmly, the problem is solved.
2. Take a small sliver or shaving of the material to be welded and light it with a match, observe the flame and smell
the smoke.
On PVC: blackish smoke and acrid smell.
On Polyethylene: no smoke, the material drips like a candle and also smells of wax
On Polypropylene: no smoke, the material drips like a candle and smells of burnt oil
On Polyamide: no smoke, pulls to form thread, smells of burnt horn.
On Polycarbonate: yellowish sooty smoke. Sweetish smell.
On ABS: blackish smoke, soot flakes, sweetish smell.
IS PLASTIC WELDING SIMILAR TO METAL WELDING?
No! Metal welding is made in a molten bath or with edges molten; the welding of a thermoplastic like PVC is made
with a plastified (pliable) surface. There is never a fused mass, but the base material and the welding rod or tape is
pressed together in plastified form. As there is no melting in the process, it is necessary to press the welding rod
into the prepared seam in order to get a joining. With pendulum welding the pressure is about 4.5 - 7 pounds.
WHAT ARE THE VARIOUS TYPES OF PLASTIC WELDING?
Plastics can be divided into three types of plastic welding. The first is friction welding, which includes sonic, spin
and vibration welding. The second category, thermal welding, includes such processes as hotplate and hot air
welding. Induction welding is the third category like electromagnetic welding. We will only be dealing with hot
air and hot plate welding.
DO I NEED TO USE NITROGEN?
Air serves as a heat transfer medium for the hot air welding. It is very seldom that other gases like nitrogen (N2) or
carbon dioxide (CO2) can bring advantages for welding plastics, which are sensitive to oxidation (Polyethylene and
polypropylene are sensitive to oxidation). The surface of the plastic materials that oxidize must be removed prior to
welding. This is most important. Soon after the oxidized surface has been removed, the welding must take place to
prevent further oxidation. Contrary to popular belief, the use of room air during the welding process does not speed
up the oxidation process to the point that it makes any difference in the integrity of the weld. The amount of time
the plastic is exposed to the air is what matters most. The longer the plastic material is left sitting, the more oxidized
it becomes. Welding oxidized plastic will produce a weak weld.
HOW STRONG ARE THE WELDS?
The strength of the weld depends on the type of weld and the composition of the plastic materials being welded.
Generally, the weld is as strong as the original material (90% or more).
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SHOULD I RUN MY TOOLS OFF COMPRESSED AIR OR A BLOWER?
You can use either compressed air or a blower. Compressed air is very expensive air compared to the cost of air
from a blower. When using compressed air, it is very important to have in line at least a 5-micron filter along with a
water extractor and a micro regulator within 10 feet of the tool. The tools typically run at about 1 - 3 psi of pressure,
so a micro regulator with a gauge on it from 0-10 psi is important to use. Better yet is to run the tools off a highpressure blower like the Leister Robust. This will assure you of clean, dry air and will save you from running
expensive air compressors. Up to six plastic welding tools can be run off of one blower.
DO I NEED TO USE WELDING ROD AND IF SO WHERE DO I GET IT?
In most cases you will need a welding rod except when you are doing overlap welding. You can make your own
welding rod out of extra or scrap parts. You can only weld like plastics together. The Malcom Company can
provide you with welding rod. Simply ask your sales rep for a quote.
DO I USE RIBBON, ROUND OR TRIANGULAR WELDING ROD?
Welding rod comes in three basic forms. Round, Ribbon and Triangular. Round is commonly used for welding in
general, however triangular is being used more and more today. Ribbon rod is a thin strip that can be used for filler
or in an overlap type weld.
The size of the welding rod depends on the base material thickness. For round rod, select a rod diameter size close
to the thickness of the base material. Some materials are thicker than the largest welding rod available. In this case
several passes of the round rod will be needed. Also, triangular rod may be best in this situation. They type of rod
you use will depend on your application.
WHAT ARE THE ADVANTAGES OF USING THE LEISTER 'V' TRIANGULAR WELDING ROD?
Much of the welding being done today is being done with triangular welding rod. The Triangular rod is designed to
fit into a beveled seam and deliver a flat, finished weld in a single pass. The weld is smooth, strong and neat in
appearance. Although welding speed is slower in inches per minute, the seam is finished in a fraction of the time
required by multiple passes with small diameter round rod. Please refer to the directive DVS 2207 part 3 of the
German Association for Welding Techniques for more technical information on this.
Leister makes special speed tips to accommodate this type for rod. The advantage of LEISTER profiled welding
rod can be shown with a simple drawing. Note that the welding rod completely fills the V area with one pass. The V
rod has more surface contact giving stronger welds.
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WHAT TEMPERATURES DO I WELD AT FOR THE VARIOUS MATERIALS?
Material Type Welding temperature
Polyporpylene (PP) 575 ° F
Polyethylene (PE) 550 ° F
Acrylonitrile Butadiene Styrene (A.B.S.) 500° F
Polyvinyl Chloride (PVC) 525° F
Polyurethane (TPUR) 575° F
See the chart below for the temperature setting on the Leister Triac tool 1A and 1G1 for the various Leister
tips with the various thermoplastic materials.
LEISTER PLASTIC WELDING TOOLS AND ACCESSORIES
For welding plastics, you will need the Hot air tool and a welding tip that directs the air stream onto the plastics
being welded. The complete line of Leister plastic welding tools and tips allow you to do any job. The Leister tools
and welding tips for plastic welding are shown in the Leister Leaflet SA11. The tips include round tips, tacking tips
and speed welding tips for both round and triangular welding rods. What tip you use will depend on your needs.
Leister also has high-pressure blowers that can be used instead of compressed air. If you use compressed air,
Malcom offers air filters and micro regulators. Consult with your Malcom salesperson for guidance on what tip and
tool will be best for your application. In the back of this instruction book, all the Leister plastic welding tools and
accessories are shown. A few of the more common tools are shown on the next page. Leister tools are made in
Switzerland and are of the highest quality. Leister is ISO 9001 certified with worldwide service in over 150
countries.
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Leister Diode PID
Plastic Welding Tool
1600 watts, power at 120V
Max temperature 1100° F, adjustable temps,
UL approved. Over 20 welding nozzles.
Requires air source, weighs just 21 ounces.
Suitable for use in the field, cold nozzle,
Digital display of actual and set temps
Leister Triac S
1460 Watts power at 120V
Max temperature 1300° F, adjustable temps. UL approved, over 20 welding nozzles available.
Built in blower with handle. Weighs 49 ounces, suitable for use in the field. Adjustable airflow.
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HELP
If you have questions, please call.
Our toll free number is 1-800-289-7505.
NOTES:
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REFERENCES
Leister Electro Geratebau
Training course #1, 1995
CH-6056
Kagiswil,
Switzerland
Leister Electro Geratebau
Training course #2, 1996
CH-6056
Kagiswil,
Switzerland
Welding Processes for Plastics, 1996
EWI Materials Joining Technology (Edison Welding Institute)
Robert A. Grimm
1250 Arthur Adams Drive, Columbus, Ohio 43221
Welding of Thermoplastics, 1993
Welding journal
Published by The American Welding Society
Bob Irving
DVS, DeutscherVerlag fur SchweiStechnik
Aachener StraSe 172
40223 Dusseldorf
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Plastic Boat Repair Instructions for building up skids and thin areas.
Basic tools needed for repair.
Select a plastic welding rod that matches the plastic and the color of the boat. The rod must be made out of the same
material as the boat. Using a clean paint scraper, scrape the welding rod surface that will be welded to the boat.
This will remove oxidized plastic on the welding rod.
Using a clean paint scraper, scrape the boat surface that will be welded. This will remove oxidized plastic on the
surface.
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Once the heat gun has reached set temperature, tack weld the welding rod in place. Push down on the rod as it heats
up. The heat gun should be moved up and down so that you heat the rod and the boat at the same time.
Set the heat gun to the pre-programmed setting for welding, in this case HD-PE plastic. Boat thermoplastic varies
between manufacturers.
In the above photo the welding rod has started to bend because it has been heated up. Continue pushing down on the
rod in order for it to create the tack weld.
Insert the heat gun between the rod and the boat as shown. Using the hand roller firmly press down as you push the
roller towards the heat gun. Slowly move the heat gun backwards while pushing down on the roller and moving it
towards the heat gun.
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.
Firmly press down on the hand roller working it back and forth making sure to work the edges. Look for squeeze
out along the edges. This action creates the weld. Pressure is very important when welding.
A proper weld will show a melted bead or plastic on both sides of the welding rod. If you move to slow you will
burn the plastic, if you move to fast you will not see the bead and you will have a less then ideal weld. Work the
roller along the edge of the weld area while heating it up to smooth out the edges.
When you have finished welding, using the cutters, cut the welding rod as close as you can to the surface.
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Work the roller along the edge of the weld area while heating it up to smooth out the edges and fare it into the
surface.
When completed you can either leave it as it is or scrape and grind it down further as desired.
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HOW TO REPAIR TEARS IN TENT AND TARP MATERIALS
HOW TO REPAIR TENTS AND TARPS WITH HEAT GUNS
Recommended Tools for Repair
Set Temperature for the material type being welded.
1. Weldy Temperature Controlled Heat Gun
2. ¾” flat wide slot heat gun nozzle
3. 1 ½” Silicon Roller
4. Shears /Scissors
5. Seam Probe, Awl or Ice Pick
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Tear shown in Tent or Tarp
Using scissors make a patch as shown
Tack Weld Patch
Insert Heat Gun as shown above while pushing down on patch with your index finger from the
opposite side from the applied heat in order to tack weld the patch in place. The photos show
that the material sides are reversed so that you can clearly see the repair.
Welding the patch in place.
Insert the nozzle between the patch and the tent/tarp while at the same time pressing down on the
heated material with the roller. Move the nozzle in and out of the patch while working around
the patch. Finish up by heating the edge of the patch while pressing the roller along the edge of
the patch to smooth over the wedge and blend it in.
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Testing the weld.
After the welding is finished, using a probe like the one shown, run it along the edge of the weld.
If the probe lifts the edge, then this area must be reworked by applying heat to the area and
rolling it out to weld the reworked area. This will prevent the wind, rain water and snow from
entering the patch which could result in pre-mature failure.
Turn the repair over and from the back side inject the Hot Air into the tear while using the roller
to press down on the heated area to weld it shut. Continue to apply the heat on the top surface
along the torn area and using the roller blend it in to the point that the tear practically disappears.
You are now finished.
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Other Applications include the repair of swimming pool liners and covers, decking and flooring
materials, thermoplastic roof membranes and inflatables.
Overlap welding reinforcements
Repair Pool Liners and Covers Fabricating and repairing tents
Repair and fabrication of boat covers Repair of inflatable party jumpers
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plastic welding instructions

Transcription

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