MEEG 401: Phase Three Report

Transcription

Phase 3 Report: Team EFC
Appendix
MEEG 401:
Phase Three
Report
Joseph Adelmann,
Steven Biebel,
Andrew Fitchwell,
Sarah Friedrich,
David Salindong
Table of Contents
1. Introduction
1
2. Background
2.1 Atomization
2.2 Relevant Technology and Regulations
2.2.1 Handheld Atomizer Spray Guns
2.2.2 Robotic Atomizers
2.2.3 Air-Bearing Motor Design
2.2.4 Existing Patent: Handheld Rotary Atomizer (Patent Number 5,803,372)
2.2.5 Ergonomic Considerations
2.2.6 EPA Regulations
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1
2
2
3
5
7
7
7
3. Project Definition
3.1 Motivation and Project Statement
3.2 Customers and Wants
3.3 Metrics, Constraints, and Target Values
8
8
8
9
4. Concept Generation
4.1Air-Bearing Motor
4.2Housing
4.3Trigger Mechanism
4.4“Click” Mechanism
4.5Handle
4.6 Final Concept
5. Prototype Manufacture, Testing, and Validation
5.1 Prototype Production
5.2 Prototype Evaluation: Testing Procedure
5.2.1 Dimensional Criteria
5.2.2 Performance Criteria
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10
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13
15
16
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1817
1817
Error! Bookmark not defined.18
6. Cost Analysis
2220
7. Updated Project Timeline
2320
Appendix A: Definition and Comparison of Ergonomic Factors
A1
Appendix B: Detailed Customer Definition and Wants Ranking
B.1 EFC (Sponsor; Contacts: Jeff Wallace and Gunnar van der Steur)
B.2 Large Automotive Companies (ex: General Motors, Ford, …)
B.3 Users (Paint Technicians)
B.4 Small Body Shops
B.5 Summary: Rankings of Wants
B1
B1
B1
B2
B2
B3
Appendix C: Detailed Target Value Formation
C1
Appendix D: Calculations
D.1 Bearing, Drive, and Shaping Air Supply Channel Dimensions
D.2 Gyroscopic Forces
D1
D1
D3
Appendix E: Complete Drawing Package
Appendix F: Assembly Instructions
F.1 Team EFC: Handheld Rotary Atomizer Assembly Instructions
EError! Bookmark not defined.1
F1
F1
F.2 Section-1: Motor Assembly and Placement
F.3 Section-2: Top Case Drive-Air Cavity Assembly
F.4 Section-3: Collar, Bell Cup, and Shroud Assembly
F.5 Section-4: Tube Assembly
F.6 Section-5: Needle and Back Assembly
F.7 Section-6: Trigger Assembly Instructions
F.8 Section-7: Knob Assembly Instructions
Appendix G: Project Timeline Gantt Chart
References
FError! Bookmark not defined.2
GError! Bookmark not defined.1
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1. Introduction
Figure 1: EFC Graphic [1]
Electrostatic Finishing Components and System, Inc. is an American engineering and
manufacturing firm based in Havre de Grace, Maryland. Their main business is to supply
electrostatic finishing components to the paint shops of large automotive manufacturers.
They design and manufacture large atomization systems for robot arm attachment. Since
the establishment of EFC in 1994, the company’s product offerings and client base have
grown significantly. The company now caters to both domestic and international clients
including “The Big Three” (General Motors, Ford, and Chrysler).
EFC’s robot-attached painting systems utilize either traditional spray or rotary
technology to atomize paint. This combination of technologies allows paint-shop robots the
versatility to complete the majority of jobs with high-efficiency and outstanding quality.
However, some areas (such as door jambs) are difficult for robots to paint effectively. For
this, human operators armed with traditional handheld high-volume-low-pressure (HVLP)
guns are necessary. Even though newer technology exists that is both more efficient and
compliant, it has yet to be adapted from the large robotic models to the handheld guns. In
this discrepancy lies the basic motivation for our project. By applying rotary atomization
technology to handheld models, users will be able to capture the efficiency and finish
quality benefits of rotaries at a smaller scale. With the development of a line of handheld
rotary atomizers, EFC hopes to not only please their current customers but also expand
their client base to smaller companies and body shops as well.
2. Background
2.1 Atomization
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Figure 2: Atomization Visual [2]
Atomization is the process by which a liquid stream is separated into an “atomic”
mist of extremely small particles. This effect is demonstrated visually in Figure 2 above.
Automotive manufacturers employ atomization to achieve the highest quality paint finishes
on their products. However, there are also concerns associated with the atomization of
paint. First of all, atomization is not the most efficient way to spread a coating. Typical
handheld guns are only around 60% efficient. The wasted paint, deemed “overspray,” can
cost manufacturers millions of dollars each year. Of additional concern is the high
composition of volatile organic compounds (VOCs) in traditional solvent-based paints.
Aerating these caustic chemicals is thus a concern that is closely monitored by law agencies
such as the EPA. New to the market, water-based (or water-borne) paints offer the more
eco-friendly alternative to solvent-based paints. However, the different properties of the
water-based paints make them more difficult to atomize using traditional methods. The
pushto develop technology that can sufficiently atomize either paint type while
maintaining superior finish quality and minimizing overspray is the underlying motivation
for this project.
2.2 Relevant Technology and Regulations
A variety of methods are currently employed to achieve atomization. These include
conventional, high-volume-low-pressure (HVLP), compliant, low-volume-low-pressure
(LVLP), airless, air-assisted airless (AAA), and rotary designs. Each method has its own
advantages and disadvantages that make them suitable for various settings and
applications. Since EFC’s current client base is limited to the automotive industry, it is the
technology used for automotive painting applications that is of interest here. The most
common atomizers used in automotive factories are HVLP and electrostatic rotary
atomizers [3, 4].
2.2.1 Handheld Atomizer Spray Guns
Even though automation has made robotic technology increasingly common in the
automotive manufacturing process, manual labor has not completely been replaced. In the
painting and coating step, workers paint the more obscure, difficult, or hard-to-reach
places with handheld spray gun atomizers. A manual gun would also be attractive to those
for whom automation is either unaffordable or unnecessary, such as small companies, local
body shops, or hobbyists. In the automotive industry, handheld atomizers are most
commonly powered by HVLP technology. An example HVLP gun is featured in figure 3.
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Figure 3: The Pressure Fed Compact HVLP gun made by DeVilbiss [5]. These guns represent high quality in the
industry and are made to be lightweight, ergonomic, and versatile.
HVLP guns use a high volume of compressed air at a lower pressure to atomize the
liquid paint. HVLP offers the necessary transfer efficiency (65 to 70%)to meet current EPA
standards. Although they achieve a good finish quality, these guns do not achieve as fine of
an atomization as the less-efficient conventional technology so the finish quality is not
quite as high [6]. Another disadvantage is that many of the current models cannot
successfully atomize more viscous paints (for example, water-based). Additional parts and
accessories can compensate for this deficiency, but at an additional cost and hassle for
users.
2.2.2 Robotic Atomizers
HVLP technology was also adapted for use on robotic arms. Even more recently, the
development of rotary atomization technology has led to a whole new family of robotic
atomizers. Rotary atomizers produce atomization that is both efficient and high quality. As
opposed to HVLP technology, rotary atomizers employ high rotational speeds and jagged
surfaces to achieve. A typical rotary atomizer currently produced by EFC is shown in figure
4.
Figure 4: Typical EFC electrostatic robotic rotary atomizer [7]
Figure 5 labels the important subcomponents within a rotary atomizer. The airbearing motor is encased within the topmost housing of the gun. The bell cup that extends
from the edge of the gun is connected to the end of the drive shaft. As the motor and bell
cup assembly rotate, pressurized paint is supplied through the center of the shaft and onto
the bell cup. The angular momentum forces the paint toward the sharp serrated edge of the
bell cup. The serrations separate the liquid paint into small airborne particle, thus
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achieving atomization. Compressed air, deemed “shaping air,” directs the airborne particles
toward the target. Electrostatic forces created by the mismatch in electric charge between
the paint and the target further attract the paint toward the surface.
Figure 5: Schematic diagram of EFC electrostatic Robotic Rotary Atomizer. The important subcomponents are
labeled [8].
With the use of electrostatic forces, EFC rotary atomizers can achieve efficiencies
greater than 90%. The paint finish quality also exceeds that of its HVLP counterparts. Not
only that, but rotary atomization itself is compliant with either solvent- or water- based
paints without the need for additional attachments. Intrinsic differences between the two
paint types place different requirements on the mode of electrostatic charge application.
For this reason alone, electrostatic rotary atomizers continue to be designed for a single
paint type. Figure 6 below show the heads of the current EFC electrostatic robotic rotary
atomizer models for solvent- and water- based paints respectively.
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Figure 6: EFC electrostatic rotary atomizer heads for solvent-based and waterborne paints. The differences
between them are impacted by the method by which the electrostatic charges are applied to the paint [9].
2.2.3 Air-Bearing Motor Design
Air-bearing motors are powered entirely by compressed air. Figure 7 features a
cutaway picture of a typical EFC air-bearing motor and housing used in their rotary
atomizers. The main components and airflow channels are labeled.
Figure 7: EFC's air-bearing motor for their rotary atomizers. The components and fluid passageways are labeled
[10].
The outer housing (shown in red) serves two important functions: holding the
bearings in place and directing compressed air flow. The back plate separates the main
compressed airline into 3 inlet ports. Each of these channels supplies pressurized air to a
different part of the motor and serves a different function. Inside of this outer housing rests
the carbon orifice bearings. The shaft is the centermost piece of the air-bearing motor. The
flywheel/ paddle assembly is attached at the back of the shaft, as shown in the diagram.
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One of the inlet ports at the back of the motor feeds “bearing air.” Bearing air is used
to support the shaft/ flywheel/ paddle assembly on a thin high-pressure film of air [11].
The high-pressure air is forced through small holes in the orifice bearings placed uniformly
along the length and circumference of the shaft. This creates a near frictionless
environment in which the shaft can rotate, allowing the motor to obtain extremely high
rotational speeds (greater than 80,000 rpm).
The second inlet port supplies “drive air.” Drive air is used to rotate the shaft/
flywheel/ paddle assembly with in the motor. Air jets are designed to strike the paddles on
the flywheel at a perpendicular angle to achieve the maximum torque. This torque causes
the shaft to rotate. The flywheel stores energy in the form of momentum. This is essential
to maintain motor speed through varying conditions (such as the addition of paint to the
bell cup).
The final inlet port delivers “brake air.” Brake air is applied in the opposite direction
of the drive air. It is used to maintain motor speed within a predetermined range and cease
motor rotation at the end of operation. Sensors monitor the current rotational speed of the
motor. When the speed exceeds a predefined limit, break air is applied to lower the speed
to be within the designated range.
Finally a fourth conduit in the back of the motor provides an escape route for the
used air. This “exhaust air” channel prevents high pressures from accumulating within the
motor and is essential to ensuring smooth and safe operation.
All EFC motors currently follow a similar design. The paddles on all of their motors
all have the same elliptical geometry and the paddle/ flywheel assembly is situated on the
back of the drive shaft. However, competitors have toyed with motors featuring different
geometries, such as the centered flywheel shown in figure 8 This seemingly simple change
impacts the location of the center of gravity of the motor, the geometry of the bearings, the
air channel plumbing, and the size and geometry of the entire motor casing.
Figure 8: This European air-bearing motor assembly is smaller than the typical EFC motors. The centered
flywheel/ paddle assembly also differs from the EFC motor, which has the flywheel on the end of the shaft. A
centered flywheel may allow for better balance and ergonomics within a handgun.
Recently EFC has also investigated the use of porous carbon in the motor bearings to
apply bearing air pressure even more uniformly and eliminate the need to drill holes for
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the bearing air jets. However, these bearings are significantly larger in order to obtain the
same pressure necessary to support the drive shaft.
2.2.4 Existing Patent: Handheld Rotary Atomizer (Patent Number 5,803,372)
Although no handheld rotary atomizers are currently being produced, a single
patent does exist for this type of mechanism. The patent explains the intricate details of the
design and provides insight into the basic concepts and technology that fuel the
mechanism. Through careful study, the team can incorporate certain general aspects with
their own innovative ideas to achieve a concept that better fulfills the wants, metrics, and
constraints of the design. The most important detail of the patent design is the safety
feature that prevents the motor from spinning when bearing air is not present. This
element cannot be duplicated without infringing upon the patent. [12]
2.2.5 Ergonomic Considerations
Since this product is destined for manual use, ergonomic factors are an important
consideration for the final design. Ergonomics of current spray atomizers were considered
as well as the ergonomics of related technology, such as paint pall guns and handheld
firearms.
From this research, the important elements that contribute to an ergonomic design
were isolated. These include gun length, trigger force, grip span, effective trigger length,
trigger cross section, handle length, handle cross section, handle material, angle between
handle and gun, weight, and torque on the wrist [13].Since a rotary atomizer contains
internal parts that spin at high angular velocities, the gyroscopic forces experienced by the
user should also be considered. Table A1 in Appendix A lists the ideal values as well as the
values of guns made by various competitors [14]. Figure A1 illustrates the referenced
dimensions. The optimal values represent the recommended values to prevent negative
effects on the health of a user due to prolonged exposure. They reflect the target values for
ergonomic considerations for design of a handheld spray gun.
2.2.6 EPA Regulations
A final consideration of high importance to this design is the existence of regulations
to which EFC’s customers must comply. The Environmental Protection Agency (EPA)
currently limits both the kind and efficiency of spray guns that can be used in the
automotive industry. HVLP represents the standard minimum to which other guns are
compared. Only guns that can prove efficiencies greater than or equal to that of HVLP are
permissible. The EPA also requires training for the personnel expected to operate the
equipment [15].
European and Canadian emissions standards currently are stricter than American,
but it is expected that American will soon enact similar federal regulations. States such as
California are already beginning to regulate VOCs in paint (their plan started to take effect
in 2009) [16]. The move to water-based paints is imminent, and even higher transfer
efficiency standards are bound to come.
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3. Project Definition
3.1 Motivation and Project Statement
The current need to develop new technology is needed that can sufficiently atomize
even water-based paints while also decreasing overspray seems to have been solved by the
introduction of the robotic rotary atomizer. The high transfer efficiencies, finish quality,
and versatility have caused many car manufacturers to begin replacing their factory robots
with this atomizing technology instead.
However, there are often hard-to-reach places within automobile frames that the
large robot-arms cannot handle. For this, paint technicians armed with smaller spray guns
are employed to coat these areas by hand. Small handheld guns also find use in smaller
body shops where a large robotic head is unaffordable and unnecessary for small touchups. Even though robot rotary atomizers have been introduced, this technology has yet to
be adapted to the manufacture of a small-scale handgun. Instead, the handheld spray gun
models carried by laborers still exercise the older, less efficient technology.
The team’s task is to design, prototype, and validate a handheld rotary paint gun.
This basic model is a proof-of-concept design, and will be the starting point from which EFC
engineers will develop a full line of handheld models for retail.
3.2 Customers and Wants
Four main initial customers are identified for the handheld rotary model. As the
funding company and eventual manufacturer and wholesaler of the product, EFC is the
most important customer to please. Next in line are EFC’s current customers: large
automotive manufactures. The final product must fulfill their wants in order to elicit a sale.
Those that actually use the product should also be considered in product design. Lastly
Thus, users encompass the third-most important customer. Small body shop owners make
up the final customer category. EFC does not currently sell their products to small body
shops, but hope to expand their client base with the introduction of this line of products.
Since this is only a potential customer, they are the least important group for consideration.
For a more detailed analysis of customer definitions and a summarized ranking of wants,
please see Appendix B.
It is important to note that a proof-of-concept prototype has vastly different
requirements than a product marked for sale. A proof-of-concept prototype should be as
simple and easy to manufacture as possible. While factors such as efficiency, safety, and
optimized ergonomic features are important to the final design, simplicity,
manufacturability, and performance are much more critical in an initial proof-of-concept
design. These additional factors will be addressed mostly during later design iterations. For
the initial design, it is most important to produce a product that is simple, manufacturable,
and performs the most basic necessary functions. For this reason, the customer and wants
rankings were modified to more closely reflect this stage of project development. This
ranking is listed in table 1.
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Table 1: Wants Ranking
Want
Simplicity
Manufacturability
Ergonomics
Functionality
Percent Importance
40
40
10
10
3.3 Metrics, Constraints, and Target Values
Utilizing the customer wants rankings, project definition, and relevant background
research, the team devised the metrics and target values that will be used to rate the
quality of the proposed concept and the performance of the developed prototype. Appendix
C outlines the detailed analysis of target value formation. Table 2 lists the important
metrics, target values, and constraints for the project. These wants and metrics were used
to evaluate the concepts generated during the second phase of the project and to select a
final concept for proposal.
Table 2: Ranking of Metrics and Target Values
Metric
Number of Speed Settings
Number of Shaping air settings
Adjustable paint flow output
Number of Parts
Number of Steps to Disassembly/Repair
Number of steps to clean
Weight
Overall Size (volume)
Handle Diameter
Cost of Prototype
Speed Range
Shaping Air Pressure Range
Paint Waste (Overspray)
Center of Gravity
Grip Span
Percent Importance
14
14
14
12
12
6
3
3
3
2
1
1
1
1
1
Target Value
5
5
Yes
Minimize
Minimize
1
< 2 pounds
Minimize
3-4 cm
< $10,000
0 to 30,000 rpm
0 to 60 psi
< 35%
In handle
4-7 cm
4. Detailed Design (EDIT)
Concept generation was broken down into subsystems which were then integrated
into a single final design. The generation of each subsystem was done independently and
then the group evaluated and examined each concept. Either individual concepts were
chosen, or more commonly two or more ideas were combined. These subsystems were
then assembled into the overall design concept. This complete concept represents the
convergence and optimization of desirable properties as indicated by the wants and
metrics rankings.
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4.1Air-Bearing Motor
The air-bearing motor is the most important and intricate part of the rotary paint
atomizing gun. Every rotary atomizer manufacturer manufactures their motors slightly
differently. For instance, all EFC motors have the flywheel and paddles in the back of the
shaft for easier disassembly. Instead, Team EFC decided to place the flywheel and paddles
in the center of the shaft in order to better balance of the gun. Furthermore, team EFC also
decided on different paddle geometry for the flywheel than EFC’s typical motor. Currently,
EFC places elliptically “crescent-shaped” paddles on the face of the flywheel. Team EFC has
placed flat-faced triangular paddles on the outer diameter of the flywheel shown in figure
9. This allows the air coming from the drive air tube to hit the face of the flywheel
perpendicularly, maximizing the force with which it hits it. Moreover, this makes it possible
to machine the entire air-bearing motor shaft out of a single piece of aluminum. Presently,
EFC constructs the shaft then has to heat treats the flywheel onto the shaft. With a single
piece, it should be easier to manufacture the shaft.
Flywheel
Figure 9: The Air-bearing shaft complete with centrally located flywheel and new paddle location and geometry
4.2Housing
The housing serves a plethora of important functions in the final design. In current
EFC robotic rotary atomizers, the main function of the housing is to hold all of the
components together and direct air to the proper components.. The drive air, bearing air,
shaping air, and exhaust air will all be directed via cavities and channels built into the
housing shown below in figure 10. The paint supply will feed into a cavity in the housing,
which is then directed into the shaft and onto the bell cup.
The housing will be entirely made of plastic in order to minimize weight. The
selected material, Acetron, is currently used by EFC because of its relatively low cost and
resistance to paint-thinning solvents. Eventually, EFC hopes to make these pieces via
injection molding. However, the initial prototype the design team will develop will be
completely machined. This is an important consideration in the prototype housing design.
All holes and cavities will need to be drilled, meaning that enclosed curved channels cannot
be used in this design.
Originally, the housing was going to be comprised of two pieces, a lower half with
the handle and an upper half seen in figure 10. It seemed that in this way, the housing
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would be easier to machine, especially the insides where there are space constrictions for
the tools. Moreover, this would installation of the shaft and air bearings easier because they
would just be placed in the lower half and the upper half would be bolted on top of them,
holding everything in place.
Upper Housing
Lower Housing
Figure 10: The old handle design showing the two parts
However upon further review, it was determined that the handle would be made out
of a single piece and the shaft and air bearings would be installed through the front of the
gun seen in figure 11. EFC had the tools necessary to get inside the housing and machine
out the spaces for the air bearings and shaft. It was determined that it would have been
difficult to machine the top and bottom halves to line up with enough precision for the
shaft to be properly balanced in the bearings in the old concept.
Housing
Figure 11: The new handle design (red component) made of a single piece
There has been a slight alteration in the shaping air chamber at the end of the gun.
Originally the housing itself would provide this chamber with the outer shroud in order to
limit the number of parts. However, once everything was assembled it was obvious that
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this would be impractical because of the position of the shaping air channel. The housing
would have needed to be thickened, which would have caused the overall weight to
increase and the feel of the gun may have been compromised. In place of that, a collar has
been designed to bolt onto the front of the housing. The outer shroud screws onto the
collar and creates the shaping air cavity in shown in figure 12.
Shaping air cavity
Collar
Housing
Outer Shroud
Figure 12: The front of the atomizers showing how the collar bolts to the housing and the collar screws to the
collar
4.3Trigger Mechanism
Staying in line with current technology, the rotary atomizer will have a variable,
trigger. Since this implementation is standard in current handheld atomizers, the
technology is well defined and understood, making design and manufacture simpler.
Connected to this finger surface are several other components including: trigger, needle,
spring, end cap, taper, casing, and pins.
In figure 13, the trigger is positioned outside of the housing and possesses two
holes. A pin inserts into the top hole and connects to small extensions on the housing itself.
The trigger will pivot about the pin upon trigger actuation. The second hole is located at the
back of the gun, through the end cap and a pin will connect it to the back of the needle. The
end cap has slots cut on either side that the pin passes through to limit the needle to
horizontal motion. This prevents interference between the needle and the rotating motor
shaft.
A major concern that surfaced during further trigger concept iterations is the
potential for paint to leak out the back of the gun or into the air cavity and air bearing
motor. In order to prevent this, Team EFC will adapt EFC’s current trigger technology.
Their paint tube will be used to encase the needle inside the air-bearing shaft. At the end of
this tube will be the taper which is in the front end of the gun near the bell cup. A front
flange was added to the tube, which seals off the air cavity from the air bearings and shaft.
The back portion of the tube has a hole from the paint feed in the housing to the inner
portion of the tube where the needle is seated. The tube now just slides into the back of the
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housing requiring no bolts. It has three O-rings in all to insure an air tight seal.
Furthermore, EFC’s existing needle design will be extended to fit the needs of this design.
When the trigger is disengaged the needle rests against the taper, ensuring no paint is lost.
In the front of the trigger end cap, there will be a casing that seals off the paint in the
back of the gun. The casing is a small plastic cylinder containing a hole through which the
needle passes. It also has inner and outer O-rings, which provide the seal. There is a spring
that goes around the back of the needle behind the in that connects it to the trigger which is
braced by the trigger end cap. This spring is what returns the needle end to the taper
sealing the tube when the user releases the trigger. The trigger end cap is then bolted into
the back of the housing to hold all of these pieces inside the gun.
By using EFC’s designs for these new parts, we are minimizing the chance of failure.
These parts have been tested by EFC and are already found in commercially available
atomizers. Moreover, their manufacturing techniques have already been perfected by years
of EFC manufacture.
Tube end
Pins
Tube
Trigger End Cap
Spring
Needle
Trigger
Casing
Figure 13: A section view of the trigger assembly
4.4“Click” Mechanism
EFC was interested in the implementation of a flow control mechanism in order to
vary the motor speed and shaping air. A “click” mechanism was developed by the team to
accommodate this constraint. However in an effort to decrease the difficulty in machining
due to the tight schedule, the “click” mechanism was not implemented on this prototype.
This prototype is EFC’s first iteration at designing a viable product so future iterations will
make use of the “click” mechanism.
Out of simplicity and ease of manufacture, it was decided that the same click system
should be used to navigate settings for both the motor speed and shaping air pressure. It
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was also decided that there would be five airflow settings as well as an “off” setting in
which air supply is completely blocked. The current design employs a shaft with varying
sized holes drilled through the cross section to alter fluid flow. The idea is that only one
through hole will match up with the main air feed and thus choke the flow. The click
mechanism consists of a click shaft, plate, and knob shown in figure 14.
Knob
Plate
Click Shaft
Housing
Figure 14: An exploded view of the click mechanism and how it was integrated into the housing
For the drive air click shaft, the through holes vary from zero to three millimeters by
six tenths of a millimeter increments and for the Shaping Air click shaft, the through holes
vary from zero to five millimeters by one millimeter increments. The detailed calculations
are outlined in Appendix D. As for the definitive click, a conventional ball bearing- spring
technique will be used. That is where a ball bearing is pressed against the rotating surface
by a spring.
Instead, for this concept, EFC’s standard restrictors were used in order to control
the motor speed. These restrictors were easier to implement than the click mechanism and
provide a rudimentary control over the motor speed. Two threaded holes were drilled from
the outside of the housing, through the drive air channels into the drive air chamber. Then
threaded restrictors were screwed into this hole. When the restrictor is screwed all the
way in, it completely shuts off the drive air. Using a tachometer, and varying the number of
turns the restrictors are loosened, EFC was able to determine that three turns of each
restrictor corresponds to the shaft rotating at 30000 rpm, the target value. There is no way
to vary the shaping air currently but it would be easy to utilize a restrictor for it as well to
provide some control.
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Restrictors
Figure 15: A cross section view of the concept displaying the restrictors
4.5 Handle
Handle concept generation leaned heavily on existing handle designs and ergonomic
factors. In addition to the handles of existing handheld atomizers, handles of related
technology were also considered, including paintball guns, handguns, and handheld power
tools. In determining the appropriate size of the handle, measurements were taken of some
industrial painters’ hands. This information indicated a target handle length and width.
Important considerations were functionality using either hand and making sure that the
handle grip is comfortable for a majority of operators. The bottom of the handle should be
large, but the top should be relatively small to accommodate the stroke of the trigger.
As per the actual dimensions of the handle, the critical ones were measured as
shown below in Figure 16 below. The current design has a lower handle width of 50.0
millimeters. According to Appendix A, the optimum value for the width should be between
30 and 37 millimeters. For this design, the bottom of the handle needs to be large enough
to have adequate space for both paint and air fittings. In the future, the handle width may
be reduced and then flare out at the bottom to provide a more comfortable feel while still
containing the two fittings. The entire height of the handle is 110 millimeters which falls
exactly into the optimal range of 102 to 125 millimeters.
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Height
Width
Figure 16: The housing showing the handle and how it was measured
The design has a grip span of approximately 4.5 cm to 6.5 cm, which fits precisely
between the target range of 4 to 7 cm.
4.6 Final Concept
The final concept contains the complete assembly of all aforementioned components
into a single system. Figure 17 shows an image of the final design completely assembled.
Appendix F contains the assembly instructions for the prototype.
Figure 17: Overall Assembly
Page 17
5. Prototype Manufacture, Testing, and Validation EDIT
5.1 Prototype Production
The timeline stipulated that Team EFC would deliver a completed drawing package
in Pro/ENGINEER on Nov. 3, 2010. The prototype was then delivered to us on Dec. 7, 2010,
giving EFC four weeks minus the holidays to manufacture the prototype. Given the amount
of work that needed to be completed, this was a strict deadline for the manufacturers.
First the drawing package went to EFC’s head engineer to be reviewed. He made a
number of alterations detailed in the concept generation section in order to increase the
manufacturability of the prototype. From there, these updated machine drawings went to
the machine shop workers to be manufactured.
Manufacturing the shaft, for example, is not as simple as just milling it out of a piece
of aluminum. Once the workers received the machine drawing, it needed to be
programmed into the CNC machines. Next the worker practiced manufacturing the part,
resulting in an iterative process to determine the best way to create the part. Then the part
was manufactured, which still could take multiple attempts. As a result of this, there were
many partially or fully completed versions of the parts created before the final version of
the part. In figure 18, there are two examples of earlier versions of the shaft and tube.
Figure 18: Early versions of the iterative manufacturing process
For instance the housing was created by first cutting a short cylinder on what
became the back of the handle so that the machine could grip it. Next the front of the
housing was machine with the mill and lathe until it was completely done. Then the front
portion was then clamped into the machine so that the cylinder could be cut off and the
back could be milled as seen in figure 19 below.
Page 18
Figure 19: The housing clamped into the mill
Once all the parts were complete the prototype was assembled following the
procedure described in Appendix E: Assembly Instructions.
5.2 Prototype Validation: Testing Procedure
With the prototype successfully built, a testing evaluation plan was designed and
implemented to analyze its actual performance for comparison with the predetermined
target values.
5.2.1 Testing Procedure
The testing procedure is comprised of a series of individual tests. Each of these tests
is designed to measure a single metric or set of metrics. The actual performance of the
prototype can be assessed by the culmination of these results. The parameters and
procedures of each test are described below.
Grip Span
Two separate data sets are necessary to obtain complete grip span data. The first
measurement was taken with a ruler from the midpoint of the disengaged trigger’s finger
surface (the location between the middle and pointer fingers) to its horizontal intersection
with the back edge of the handle. For the second measurement, the trigger was fully
engaged. The stroke length is simply the difference between these two grip span
measurements.
Weight
Weight was assessed using a digital scale with resolution of 0.1 oz. The handheld
rotary atomizer gun was be fully assembled sans hoses.
Center of Gravity
The location of the center of gravity was obtained by hanging the gun from multiple
axes and locating their intersection. This test is described more fully in Section _ of
Appendix _.
Trigger Force
Trigger force was measured with a compression force tester. The atomizer was
positioned with trigger parallel to compressive testing platform. Trigger was actuated
while recording trigger pull force. Maximum trigger pull force was recorded at the end of
the trigger stroke.
Shaft Balance
In order to guarantee stability in the shaft during rotation, each shaft is individually
balanced. This is done by removing some material from the shaft. EFC used a tolerance of
0.500 mg*in for the prototype’s shaft. To achieve this value, some material was removed
with a Dremel grinder from the inside of the shaft at each end. In all 14 mg was removed
from the front of the shaft and 7 mg was removed from the back to achieve the tolerance.
Page 19
Motor Speed
Motor speed was measured using a digital non-contact tachometer on the fully
assembled gun.The bell cup was marked with a black marker, which the laser tachometer
was able to locate throughout rotation. The drive air restrictors were slowly opened until
the desired 30,000 rpm motor speed was reached. The target speed corresponds to a
restrictor setting of three rotations. The picture in Figure _ below was taken during the
motor speed test once the desired rotational speed was obtained.
Figure 10: Motor Speed Test with Laser Tachometer
Paint Flow Rate
Paint flow rate was quantified in terms of volume paint sprayed per unit time. The
gun was sprayed into a graduated cylinder for a set amount of time (20 seconds). The total
volume collected was multiplied by three to obtain the volume flow rate per minute. The
test was performed without air pressure to ease collection of paint. It is pictured in figure _
below.
Formatted: Font: Italic
Figure 11: Paint Flow Rate Test
Air Flow Rate
Air flow rate measurements were obtained with a digital flow meter in line with the
input airline. Bearing and shaping air measurements were obtained with the drive air
Page 20
restrictors closed. Total air consumption was measured with the motor running at the
target speed of 30,000 RPM.
Wrist Torque
Wrist torque can be the result of multiple sources. First, the weight of the gun in
combination with an offset center of gravity can put cause the user to experience a torque.
Secondly, angular acceleration can lead to gyroscopic torques. Finally, the weight and
location of the fluid supply hoses. The hoses were designed to connect to the gun through
the handle, minimizing that source of wrist torque.
The remaining sources were analyzed using the same test, shown in Figure _. A
torque screwdriver was secured in a vice parallel to the floor. The atomizer was clamped at
the bottom of the handle to provide the maximum torque value, which was then attached to
the torque screwdriver. For the torque generated by the weight of the atomizer, the torque
wrench was attached to the side of the handle to simulate a user’s clenched fist moving
down. The atomizer was not turned on, but was free to rotate downwards. The wrist
torque was measured by the torque screwdriver and then recorded.
To measure the amount of gyroscopic torques caused by the angular acceleration,
torque screwdriver was attached to the back of the handle. This is to simulate the clenched
fist rotating side to side as a result of the gyroscopic torque. Then the drive air was turned
on and the torque value was recorded.
Figure 12: Preparing prototype for gyroscopic wrist torque test
Atomization of paint
Paint atomization is a subjective test. Paint was sprayed onto a test panel. Paint
particles were observed as a fine mist, proving paint atomization occurred. See Figure _
below.
Page 21
Figure 13: Prototype successfully atomizing paint
5.2.2 Test Results and Prototype Evaluation
The results of these tests are shown in Table _ below.
Specification
Grip Span (limits)
Trigger Stroke
Weight
Maximum Trigger Pull Force
Motor Speed
Paint Consumption
Air Consumption
Maximum Wrist Torque
Successful Paint Atomization
Target Value
4-7 cm
< 3 cm
< 32 oz
< 20 N
30,000 rpm
20cc/min
15 cfm
< 1 Nm
Yes
Actual Value
4.5 – 6.5 cm
2 cm
29.06 oz
18 Nm
>30,000 rpm
20cc/min
17.9 cfm
.28 Nm
Yes
On a whole, the prototype met or exceeded nearly all of the measured target values.
The only target value not explicitly met is that of air consumption. It should be noted that
this test was performed at the maximum motor speed and shaping air settings. The design
team predicts that the addition of the click system to regulate shaping air would remedy
this issue. Precautions should also be taken to prevent air leaks, as the connection between
the compressed air supply hose and the hose fitting was not entirely air tight.
The grip span, trigger stroke, and maximum trigger force were important in the
ergonomics discussion and easy to achieve from a design standpoint.
The weight metric was defined by the Sponsor early in the design process. Using
lightweight materials such as aluminum, plastic, and carbon, and minimizing the size and
number of parts, the senior design team was able to build a concept to adhere to this
criteria. Computation tools in SolidWorks and Pro/ENGINEER made it possible to estimate
and track the weight of the assembly throughout the design process. The final weight of the
prototype confirms these estimations.
One of the most important parameters was the motor speed. Normally EFC’s
atomizers run at 80,000 rpm, with a maximum speed around 100,000 rpm. However,
having never made an atomizer this small, a lower maximum desired speed was defined. A
motor speed of 30000 rpm can still achieve atomization, while limiting safety concerns.
Page 22
The prototype was able to easily achieve this value. However, more research and testing
should be performed before suggesting use at higher speeds.
Wrist torque is another ergonomic metric that relied on a number of different
variables. The easiest to control were the center of gravity, weight of the gun, and location
of the hose connections. To control gyroscopic forces, the mass of the rotating components
(shaft, fly wheel, and bell cup) mas minimized through the use of low-density materials. In
this way, even large angular accelerations were designed to produce relatively low
gyroscopic torques. Testing confirmed these calculations, and the minimal effect of
gyroscopic forces. Thus, wrist torque was minimized.
Most importantly, the gun successfully atomized paint. While design optimization is
still necessary to achieve the desired user control, transfer efficiency, and finish quality, the
successful atomization affirms the functionality of the proof-of-concept prototype: a
handheld rotary atomizer paint gun can successfully atomize paint.
6. Cost Analysis
At the beginning of the project, EFC management suggested a tentative $10,000
budget for the design of the prototype, but offering to pay more if necessary. After
submitting the final design, the design team worked with EFC engineers to estimate a cost
for the prototype. This estimate came out to a total of $6350. The detailed cost analysis is
outlined in Appendix G.
The prototype was manufactured entirely within EFC’s headquarters. EFC’s bulk
materials, machine shop, and machinists were used in the production. As each part was
made, the machinist recorded the amount of material used, the time required to set up the
machine, and the machining time of each part. In addition, the programming time for each
part on each machine was also recorded. Using this data, the team could accurately
calculate the cost of the final prototype: $7012. A part-by-part analysis of the prototype
cost is given by Table G2 in Appendix G.
This same data was also used to extrapolate the cost of mass production using the
same manufacturing methods (machining alone). The team calculated the projected total
cost and cost per gun for production runs of 100, 500, and 1000 guns. The total cost and
cost per gun are reported in Table 3 below. The detailed calculations can be found in
Appendix G.
Table 3: Projected Cost of Large-Scale Machined Manufacture
Lot Size
100
500
1000
Total Cost
$109,200
$543,100
$1.086 million
Cost per Gun
$1091.91
$1,086.16
$1,085.44
Page 23
7. Path Forward
The final prototype represents the significant progress made by the design team.
Since no rotary handheld paint atomizer currently exists, there is great potential to
influence both the retail and use of handheld atomizers in a variety of industries and
applications. Before the design is ready for retail and bulk manufacture, the design team
recommends further work on behalf of EFC’s research and development group. First,
additional tests should be performed on the prototype to fully define the current state and
identify any areas that need improvement. From this, EFC designers can begin modifying
this original design for a second prototype. EFC designers should also consider the addition
of features and functions deemed unimportant for initial design. These include ergonomic,
safety, and ease of use criteria. Lastly, alternative manufacturing processes should be
considered in addition to pure machining. When manufacturing parts in large numbers,
time, costs, and material waste can be reduced by considering alternative production
methods.
7.1 Additional Testing
Further testing is necessary to fully characterize the performance of the prototype.
The remaining criteria listed below require further testing.
1. Transfer Efficiency
2. Finish Quality
3. Service Life
Tests to evaluate transfer efficiency and finish quality are well-defined in the highquality paint atomization industry. Both qualities are evaluated from a single sample. A
panel, such as that previously shown in figure 13, is painted with the gun. The weight of the
panel before and after testing is noted, as well as the total paint used. Transfer efficiency
refers to the ratio of paint on the panel to total paint used, and is evaluated through the
change of weight in the panel. Finish quality is a function of various qualities. These include
orange peel, color variation, film build, and gloss. Each of these tests are performed on the
panel after it is baked for the paint to dry. Transfer efficiency and finish quality tests can be
performed simultaneously. Since an important functionality of rotary atomizers is its
impartiality to paint type, these tests should be performed using all paint types typical of
automotive painting.
Another important specification is the service life of the device. EFC currently
designs all of their guns to perform a minimum of 1,000 hours of continuous use before
requiring service, repair, or replacement. The prototype should be left running at the
maximum settings (30,000 rpm) to analyze the continuous service life of the motor. A
handheld gun will also encounter much more cyclic loading than the robotic atomizer
machinery: the motor and trigger will be engaged and disengaged multiple times as the gun
is used. As such, each of these mechanisms should also be tested cyclically to failure for an
accurate durability estimate.
Page 24
7.2 Suggested Design Iterations
First, EFC designers should review all of the tested data and modify or redesign to
fix any deficiencies of the first iteration prototype. The design team also recommends
considering alterations to reflect ergonomic, safety, and ease of use criteria.
7.2.1 Additional Features
One of the most unique features of the final concept design was the click mechanism
for controlling shaping air pressure and motor speed. Due to time constraints, however,
this feature was eliminated for the manufacture of the prototype. The design team
recommends implementing the click design into the second iteration of the gun. The results
of air consumption, air flow rate, and motor speed tests should allow EFC designers to
make any modifications to the hole diameters in the click mechanisms to predict better
results. The design team does not predict the implementation to be difficult, since the click
mechanism is designed to be mostly exterior to the remainder of the gun.
Since the first prototype was not intended to go to market, safety was not a major
concern in its design. For this reason, decisions were made to increase simplicity while
neglecting safety considerations. One of these decisions was the design of the bell cup. To
ease in manufacturing, the design team designed the concept to incorporate EFC’s standard
30 mm bell cup. This bell cup works well to atomize paint, but its sharp edge can pose a
serious safety hazard to handheld users. Since encasing the edge of the bell cup hinders the
performance of a rotary atomizer, the bell cup should instead be designed with a more
rounded edge.
A second important safety feature would be a Brake air system. The current drive
air system only introduces air into the motor in one direction. This allows the motor to
accelerate, but relies on friction alone to slow and cease motor rotation. With sharp parts
rotating at such high speeds, the inability to stop the rotation quickly poses a safety hazard.
It could also impact the durability and service life, since it would continue rotating long
after its necessary operation has ceased. A brake air system that provides drive jets in the
opposite direction could slow and cease motor rotation much more quickly. It would also
allow the motor speed to be monitored and maintained at constant setting more easily. A
brake air system is an important and necessary feature to incorporate into the final designs
for retail.
Finally, the design team recommends designing an electrostatic system for
implementation into a handheld model. The introduction of electrostatics can greatly
improve transfer efficiency, which would make the product even more attractive to
potential customers. However, its implementation should still meet important size, weight,
and safety specifications.
7.2.2 Suggested Alterations for Ergonomic Design
Ergonomics are an important consideration unique to handheld devices. Since EFC
has traditionally manufactured robotic arm attachments and systems, this has not played a
large role in their previous design projects. For initial proof-of-concept designing,
ergonomics also rank low in priority compared to simplicity, manufacturability, and
functionality. However, before the product is sent to market, this factor should certainly be
Page 25
addressed. Through benchmarking research, the senior design team has identified the
important features, dimensions, and systems that impact the ergonomic appeal of a spray
gun. These features, along with their target values and industry averages are provided to
give EFC designers team values to shoot for. Figure _ illustrates the referenced dimensions.
Figure _: Schematic drawing of a spray gun. Important dimensions and measurement points are labeled: A= gun
length; B= grip span (at the height of point b); b= point between index and middle finger for median male; C=
effective length of trigger (from point c to point c’); c= point at which surface of rear heel becomes more or less
parallel with upper part of gun; c’= corresponding point on trigger; D= distance between rear and front heel; d=
point at which surface of front heel becomes parallel with upper part of gun; E= width of upper part of handle; F=
width of lower part of handle; G= length of handle (from point c); H= angle between handle and upper part of gun.
Most of the suggested alterations concern the design of the handle and trigger. First,
the shape of the handle should be altered to fit more comfortably in the hand. For this, the
design team recommends an ellipsoidal handle shape (elliptical with straight sides) with
dimensions that adhere to the optimal grip span criteria.
The design team also recommends preserving the dual finger-trigger system since
most current spray atomizers contain dual-finger triggers. For this type of trigger system,
the design team recommends a handle that contains both a rear and front heel. This type of
handle design helps to distribute the weight of the gun across the hand and minimizes the
roll of friction in supporting the gun. The optimal distance between the rear and front heels
is 36-43 mm for men and 29-37 mm for women. Since painters tend to have large hands,
the design team recommends a distance of 38-40 mm. The grip of the trigger should
Page 26
comfortably fit the pointer and middle fingers. For this reason, the distance between the
bottom of the trigger and the top of the front heel should be minimized.
An additional ergonomic suggestion would be to control paint flow in an alternative
method to a variable trigger. A non-trigger can provide a more consistent flow rate, which
in turn leads to more consistent spray patterns and paint finishes. Thus, the senior design
team recommends implementing a third click system for paint flow rate control in addition
or in place of the variable trigger design.
Future designs should also continue to follow those ergonomic criteria already met,
including wrist torque, handle length, optimal grip span, and trigger force. Wrist torque is
an important consideration for handheld devices. Ergonomic research suggests that the
wrist torque of tools handled 10-30 minutes continuously or 1-4 hours intermittently per
working day should not exceed 1 Nm. Testing showed the current prototype design to
adhere to this constraint. The senior design team recommends that this value be
considered, monitored, and maintained in future concepts. Ergonomic research also
suggests that the maximum required trigger force should not exceed 20 N. Even though
most current spray guns greatly exceed this value, the design team still recommends future
designs that adhere to this requirement. Research also shows that the optimal grip span for
most people is between 50-60 mm. This means a grip span with limits between 40-70 mm
would be optimal. The grip span of the prototype falls precisely between these values and
should not be modified if possible. Finally, ergonomic reports recommend that tools that
require a power grip to have handles at least 125 mm in length. Current spray guns have
much shorter handles. The design team recommends a handle length of at least 110 mm
(the length of the current prototype).
7.2.3 Alternative Manufacturing Processes
Machining can be useful for making relatively simple parts and for achieving ____
tolerances. However, alternative manufacturing methods can be done faster, produce less
material waste, and be done at a cheaper price for large scale manufacture. The handle
takes a significant amount of time to manufacture, and with it mostly hollow, the material
waste is significant. Since the material is a thermoplastic, injection molding would be a
viable alternative production method. Necessary tolerances can be achieved with finish
machining, which would be less time consuming than machining the entire piece.
The team used the current .iges file of the handle and an online _______ to estimate
the cost of the tooling and manufacture of certain numbers of parts.
Similarly, pressed porous carbon bearings can be made more cheaply than the
machined. Carbon is difficult to machine to the precise tolerances and small size necessary
for this design.
8. Summary
The senior design team feels confident that the final concept design and resultant
prototype offer an innovative ______ starting point for further design and innovation
refinement to develop a final line for retail. By including additional features, making small
Page 27
alterations for ergonomic compatibility, and investigating the use of alternative
manufacturing methods for particular parts, the design team expects the final line to be
creativeinnovative, profitable economical, and profitable _________. The design team
expects EFC to raise the standard of handheld atomizers to a new level in terms of
efficiency, finish quality, simplicity and ______.
The team went through numerous Computer-Aided Design iterations before
beginning prototype manufacture. Each piece was individually modeled, then assembled to
gain an understanding of how they fit together. From these exact assemblies, prototype
manufacture presented new challenges resultant from the central flywheel geometry.
Further, the innovative “click” system had to be removed in the interests of time. Once the
manufacture had completed, the team undertook a comprehensive testing plan, which
validated that customer defined target values had been achieved. The design team expects
EFC use this prototype to raise the standard of handheld atomizers to a new level in terms
of efficiency, finish quality, simplicity and functionality.
The sum of the teams’ efforts, ideas, and materials have been passed along to EFC
machinists and engineers to complete the transition from conceptualization to commercial
realization. The prototype provided to EFC is the proof-of-concept/first iteration design to
validate that robotic rotary atomizer technology can successfully be applied to a handheld
design. With all of our knowledge, ideas, and materials now in the hands of EFC engineers,
it is up to them to make this conceptual idea into a reality.
Formatted: Indent: First line: 0.5"
Appendix A
Page A1
Appendix A: Definition and Comparison of Ergonomic Factors
The figure and data listed below were taken and modified from Bjoring and Hagg’s
paper on pray gun ergonomics [A1].
Figure A1: Schematic drawing of a spray gun. Important dimensions and measurement points are labeled: A= gun
length; B= grip span (at the height of point b); b= point between index and middle finger for median male; C=
effective length of trigger (from point c to point c’); c= point at which surface of rear heel becomes more or less
parallel with upper part of gun; c’= corresponding point on trigger; D= distance between rear and front heel; d=
point at which surface of front heel becomes parallel with upper part of gun; E= width of upper part of handle; F=
width of lower part of handle; G= length of handle (from point c); H= angle between handle and upper part of gun.
Table A1 below contrasts the optimal values with the real values of a variety of
actual spray gun models. The dimensions are labeled in figure A1 above.
Table A1: Values of Ergonomic Parameters for Ideal and Real Spray Guns
Manufacturer
Method
Model
Weight of gun, without
hoses (g)
Length of gun (mm)
Trigger force, middle
(N)
Trigger force, fully
depressed (N)
Optimal
ECCO
Low Pressure
40
ECCO
High Pressure
360
ECCO
-100
Kremlin
Combination
JX
Binks
-March 2
Binks
HVLP
BBR
640
600
550
535
660
600
Minimize
136
20
122
25
133
34
125
20
140
15
140
15
< 20
39
34
44
26
34
54
Appendix A
Grip-span, activated
trigger (mm)
Grip-span, unactivated
trigger (mm)
Distance between rear
and front heel (mm)
Effective trigger length
(mm)
Page A2
50-60
56
46
38
42
47
43
50-60
71
56
50
52
57
56
36-43
44
46
48
45
48
48
Maximize
42
44
44
43
45
45
Appendix B
Page B1
Appendix B: Detailed Customer Definition and Wants Ranking
B.1 EFC (Sponsor; Contacts: Jeff Wallace and Gunnar van der Steur)
As the funding company and eventual manufacturer and wholesaler of the product,
EFC is the most important customer to please. Their wants are listed below in order of
importance: the percent importance is written in parentheses.
1. Ergonomics (35%): First and foremost, EFC executives desire an ergonomic design.
Ergonomics is a general term, comprising elements of comfort, balance, weight, and
aesthetics.
2. Functionality (20%): Obviously, a successful prototype has to satisfy several criteria.
Primarily, the prototype must successfully atomize paint, but other considerations
include: even paint application (no drips), compatibility with both solvent-based
and water-based paints, and overspray minimization.
3. Ease of Use (20%): The prototype should feature a straightforward design that can
easily be understood by operators.
4. Durability (15%): A successful prototype should easily withstand the “wear and
tear” of everyday use without damage or diminished performance. Furthermore,
this includes material strength, material hardness, and service life.
5. Manufacturability (8%): In order for EFC to bring a prototype to mass production,
its design must feature a limited number of parts and machining time.
Manufacturability considerations consist of number of parts, number of steps to
assemble, and design precision.
6. Safety (2%): It must adhere to certain occupational safety standards in order to be
usable in factories.
B.2 Large Automotive Companies (ex: General Motors, Ford, …)
Large automotive companies currently form the largest customer base for our
sponsor, and thus are the second-most important customer to the design team. Therefore,
their wants and expectations must also be carefully considered in product design. After
careful collaboration with EFC (our closest link to these customers), a ranking of their
wants is listed below.
1. Value (60%): profitable, durable, functional. First of all, the product must exhibit
both functionality and efficiency. In this case the initial costs must be more-thancompensated for by material savings and increased quality paint-finishings.
Durability also plays a role, as a model with a long-lifetime will require less
maintenance and replacement costs over time, thus also decreasing costs long-term.
2. Meets or Exceeds Necessary Standards (EPA, OSHA, safety) (20%): Government
regulatory agencies such as the EPA and OSHA put regulations in place in the
interest of worker and environmental protection. Any equipment that a car
Appendix B
Page B2
company employs in its factories must comply with these regulations or risk fine,
court cases, or worse.
3. Ease of Use (20%): Equipment that is easy to use will less likely be damaged due to
user error. Features associate with this want include: well-defined settings, straight
forward operation, ease of cleaning, minimal number of steps to operate
B.3 Users (Paint Technicians)
This customer encompasses those that actually use the equipment. Although most
users do not buy the equipment themselves (automotive manufacturing managers do), EFC
is still very concerned with pleasing those who are most directly affected by their products.
Users form the third-most important customer base that the design team should consider.
Talking with Louie Scalia, an actual General Motors Spray Operator, allowed the team to
discover what features are important to this demographic.
1. Ergonomics (45%): A comfortable, non-aggravating design is very important to
those who have to hold the gun for a minimum of eight hours. An ergonomic design
will eliminate the “hand-sag” typical of the joint fatigue caused by current designs.
2. Ease of Use (35%): Easy to use tools are always a prime concern of their users;
however, this is especially true of Spray Operators, who often operate on incentive.
This is includes the number of speed settings, number of shaping air settings, and
number of steps to clean.
3. Durability (10%): An average day of work will include several instances of dropping
and banging, and the prototype should not be affected by this. These parameters are
along the same as the durability parameters for EFC.
4. Safety (10%): Obviously, Paint Spray Operators cannot be placed in danger by the
tool of their livelihood. The rotary atomizer spray gun cannot be any more
hazardous than what users are already accustomed to. This is the same as the safety
want for EFC.
B.4 Small Body Shops
The final customers relevant to this design project are local body shop owners. This
demographic is not currently one of EFC’s customers, but EFC executives hope to expand
their clientele with the introduction of a rotary handgun line. However, as this is only a
potential customer for EFC, body shop owners are thus the least important customers for
the design team to consider.
1. Value (60%): Understandably, small body shops operate small budgets; therefore,
their prime concern is value. The initial cost of the device should be outweighed by
the savings in paint costs due to increased efficiency.
2. Ease of Use (30%): Unlike large automotive manufacturers, small body shops do not
have the benefit of offering comprehensive equipment training to their employees
so they place great value on an easy to use design. Again the number of speed
Appendix B
Page B3
settings, number of shaping air settings, and number of steps to clean it are included
under ease of use.
3. Meets Regulations (10%): Automotive paint finishes are subject to very stringent
quality regulations, and body shops want to replicate the quality of a “factoryfinish.” A spray gun that allows small operations to meet the quality regulations of
the large manufacturers is significant.
B.5 Summary: Rankings of Wants
Once the customer priorities had been identified, and the wants of each customer
characterized, the team could then determine an overall ranking of wants along with their
percent importance. This is summarized in Table 1 below.
Table B1: Ranking of Customer Wants
Final Ranking
1
2
3
4
5
6
7
8
Want
Ease of use
Ergonomic
Value
Functionality
Durability
Meets Necessary Regulations
Manufacturability
Safety
Rate of Importance
28
23
19
10
9
6
4
2
1. Ease of Use: The spray atomizer will be used by a wide variety of users in a large
spectrum of applications; therefore, the ease of use ranked first. Spray operators
and their employers alike desire a straightforward design. For example, many
automotive operators are paid on incentive so they want to understand the basic
operation of their equipment so they can self-troubleshoot small problems. Further,
quick operator-based adjustments reduce the possibility of downtime which all
body shops desire (both large and small).
1. Ergonomic: EFC executives placed an initial emphasis on ergonomics because their
customers’ employees often have to spend an entire workday swinging an atomizer
in a repetitive sweeping motion.
Formatted: Normal, Indent: Left: 0.25",
Hanging: 0.25", No bullets or numbering
2. Value: value is always a major want because all purchasers want to gain a sizeable
return on their budgets. Large manufacturers desire a prototype that will
eventually generate paint savings that offset the initial investment cost, and small
body shops cannot spend divulge an exorbitant sum.
Formatted: Numbered + Level: 1 +
Numbering Style: 1, 2, 3, … + Start at: 1 +
Alignment: Left + Aligned at: 0.25" + Indent
at: 0.5"
1. Functionality: A paint atomizer that successfully meets or exceeds all customer
defined target values is the driving force behind this project. Furthermore,
functionality can be expanded to include the avoidance of paint fouling and the
minimization of overspray and drips.
Formatted: Indent: Left: 0.5", No bullets or
numbering
at: 0.5"
numbering
Appendix B
Page B4
2. Durability: The atomizer should be able to withstand the normal abuses of daily use
without failure or reduced performance. Further, the design should have the
capability to survive the standard industry cleaning practice of running solvent
through the machine after each day or shift without unnecessary wear.
3. Meets Necessary Regulations: The United States Environmental Protection Agency is
working toward the removal of solvent-based paints in favor of the more ecological
of water-based. The atomizer should have the capability to operate with water and
solvent-based paints to both meet current regulations and remain usable under
upcoming standards.
4. Manufacturability: EFC has the eventual goal of mass-producing the atomizer for
commercial sale. In order to adhere to this aspiration, the design must minimize
both the complexity of part manufacturing and the total number of parts. This
includes reducing machining time.
5. Safety: The Occupational Safety and Health Administration issues minimum
specifications that allow a spray gun to be used in factories. Obviously, in order for
EFC to sell to their customers, the atomizer must either meet or exceed these
standards. EFC engineers informed the team that they will consider additional
safety issues during successive iterations.
at: 0.5"
numbering
at: 0.5"
numbering
at: 0.5"
numbering
at: 0.5"
Formatted: Normal, No bullets or numbering
Appendix C
Page C1
Appendix C: Detailed Target Value Formation
The target values for each of the measurable metrics were either given by the
sponsor, or formed through benchmarking research. The target values that were defined by
EFC are listed in Table C1 below.
Table C1: Metrics and Target Values Defined by Sponsor
Metric
Number of Speed Settings
Number of Shaping air
settings
Adjustable paint flow output
Weight
Cost of Prototype
Speed Range
Shaping Air Pressure Range
Target Value
5
5
Yes
< 2 pounds
< $10,000
0 to 30,000 rpm
0 to 60 psi
The target values for certain metrics were fairly straightforward. Number of parts
and number of steps to disassembly and repair are both related to simplicity, and should
thus be minimized. The rest of the target values were based on the preliminary
benchmarking research.
All current spray guns are cleaned in one step: by passing paint cleaner through the
spray gun. At the end of daily use, they are left to soak in paint cleaner overnight. The
design team would like to keep the cleaning process at least this easy, thus limiting the
number of steps to clean to one.
The optimum trigger force, gun dimensions, and grip span are mostly impacted by
ergonomic factors. The target values represent the ideal values recommended for
ergonomic considerations. These parameters were also examined in current spray guns.
For many of the parameters, the current spray guns do not fall within this ideal range.
Thus, a larger range was considered acceptable for these parameters, even though the ideal
range still represents the optimal target value. Table C2 lists these dimensions with the
target value and the currently acceptable range.
Table C2: Metrics, Target Values, and Acceptable Ranges determined through ergonomics research and state-ofthe-art benchmarking
Metric
Gun Length (mm)
Grip Span: unactivated trigger (mm)
Grip Span: activated trigger (mm)
Trigger Force (N)
Distance between rear and front heel (mm)
Width Upper Handle (mm)
Width Lower Handle (mm)
Target Value
Minimize
50 – 60
50 – 60
< 30
36 – 43
<50
Current
120 – 140
45 – 70
40 – 60
25 – 55
40 – 50
25 – 40
25 – 40
Appendix C
Handle Thickness (mm)
Page C2
<30
15 – 25
A target value is not listed for the width of the upper handle because the width
depends on the length of the trigger stroke. However, it does need to be large enough to
allow the paint and compressed air to flow through the channel.
Page D1
D.1 Bearing, Drive, and Shaping Air Supply Channel Dimensions
The operation of a rotary atomizer gun depends on the air pressure in each of the 3
inlet air channels: bearing air, shaping air, and drive air. Designing the gun to provide the
necessary pressure in each channel is essential to correct operation. The channel diameters
were designed to achieve the necessary pressure values. The process used to obtain these
values is outlined below.
EFC currently designs off of empirical data. The design team decided to continue this
method. Through trial and error, EFC engineers have determined the optimal size and
number of drive air, shaping air, and bearing air jets necessary to achieve optimal
operation. Thus the design team chose to use these values to place and dimension the air
jets for each of these air ports. Table D1 below lists the size and number of air jets for each
bearing air, drive air, and shaping air.
Table D1: Air Jet Parameters for Inlet Air Channels
Air Channel
Shaping
Drive
Bearing
Number of Holes Nholes
40
4
24
Drive Jet Outlet Hole Diameters dout (mm)
0.7
1.0
0.2
To achieve maximum pressure and avoid choking the flow, the inlet area of each the
bearing, shaping, and drive air supply channels needs to be at least as large as the sum of
the jet outlet areas. The equation below relates the outlet and inlet diameter din for each of
the channels.
This simplifies to
√
Using the above equation, the inlet diameter of each air supply channel was
calculated. The results are listed in Table D2 below.
Table D2: Calculated Inlet Air Channel Diameters
Air Channel
Shaping
Drive
Bearing
Channel Diameter din (mm)
4.4
2.0
1.6
Page D2
To account for friction and other factors, the inlet diameters were assigned the
larger values listed in Table D3 below.
Table D3: Inlet Diameters of Shaping, Drive, and Bearing Air Supply Channels
Air Channel
Shaping
Drive
Bearing
Channel Diameter din (mm)
3
3
2
However, just because this is the diameter necessary to achieve maximum air flow
does not mean that the maximum air flow is needed for all channels. The variable drive air
and shaping air settings are achieved by varying the outlet air pressure. The click
mechanism achieves this by decreasing the area of the supply channel, which chokes the
flow. Thus, choking calculations of fluid flow were used to determine the settings to achieve
the motor speed and shaping air pressures designated by the sponsor.
To achieve this, the design team obtained experimental data from one of EFC’s
current rotary atomizer guns. This data relates compressed air usage to shaping air
pressure and motor speed. From this, the design team could estimate the choking diameter
at the specified mass flow rates. The equation for choked flow (equation D1 below) that
was used to determine the throat area A* is written below.
̇
√
From this, the diameter is a simple calculation. Since the motor in the handheld
prototype design is smaller than the one tested, a safety factor of 30% was used for the
drive air calculations. The choking diameters for motor speeds ranging from 15 to 30 krpm
are listed in Table D4 below.
Table D4: Empirically Calculated Drive Air Click Settings
Motor Speed (krpm)
15
20
25
30
Mass Flow Rate (kg/s)
0.02364
0.02873
0.03364
0.03148
Initial Velocity (m/s)
398.47690
484.30271
567.06328
530.51660
Throat Area (m2)
0.00002
0.00002
0.00002
0.00002
Diameter (m)
0.00453
0.00500
0.00541
0.00523
The shaping air data also came from a rotary atomizer that is larger than the
handheld prototype design. Since the mass flow of shaping air is directly proportional to
the size of the bell cup, the required mass of compressed air to achieve the same pressures
will be less than that of the test rotary atomizer. For a safety factor, however, the
compressed air usage was assumed to be the same for both guns. The choking diameters to
achieve shaping air pressure from 10 to 60 psi are listed in Table D5 below.
Page D3
Table D5: Empirically Calculated Shaping Air Click Settings
Pressure (psi)
10
15
20
25
30
35
40
45
50
55
60
Mass Flow Rate (kg/s)
0.02364
0.03078
0.03777
0.04407
0.05036
0.05666
0.06295
0.06939
0.07526
0.08212
0.08813
Initial Velocity (m/s)
398.47690
518.72734
636.61991
742.72323
848.82654
954.92986
1061.03318
1169.49435
1268.52411
1384.05884
1485.44646
Throat Area (m2)
0.00002
0.00002
0.00003
0.00003
0.00003
0.00004
0.00004
0.00005
0.00005
0.00006
0.00006
Diameter (m)
0.00453
0.00517
0.00573
0.00619
0.00662
0.00702
0.00740
0.00777
0.00809
0.00845
0.00875
Comparing these choking diameters with the total outlet jet diameter, it is clear that
the limiting factor is the outlet diameter of the jets. Therefore, the flow would choke at the
jets rather than in the click system settings. Therefore, the click settings were instead
designed to be evenly spaced between 0 and the inlet diameter. Table D6 lists these
settings for the shaping and drive air channels.
Table D6: Shaping Air and Drive Air Click Setting Diameters
Off
Shaping
Air
Drive
Air
0
Click 1
diameter
1
Click 2
diameter
2
Click 3
diameter
3
Click 4
diameter
4
Click 5
diameter
5
0
0.6
1.2
1.8
2.4
3
D.2 Gyroscopic Forces EDIT
The fundamental concept behind rotary atomization involves a shaft spinning at
very high angular velocity to atomize paint particles. This high rotation rate will produce
gyroscopic forces that resist the pendulum hand swing of spray operators. The gyroscopic
forces of the shaft, bell cup, and flywheel will each be calculated separately then summed.
Torque applied perpendicular to the axis or rotation is called precession, and the
fundamental equation behind this phenomenon is given below.
When rearranged this equation becomes the following:
All spinning components rotate at 30 000 RPM which is equivalent to 3141.5 Hz
The user input is taken as a sinusoidal function, and is governed by the following equation:
Page D4
Where
(
)
Hz
Now from the fundamental equation,
must still be calculated, so;
Since the maximum value of cosine is +1, the cosine part of the equation can be removed
Plugging-in all necessary quantities yields:
With all necessary equations derived, the gyroscopic force of each rotating component can
be calculated independently and summed to get the overall torque
The shaft calculations will be performed first
The moment of inertia of the shaft is given by the following equation:
Where
Hence
Lastly, the torque contribution of the shaft is
Now the calculations will be performed for the bell cup.
The moment of inertia of the bell cup is given by the following equation:
Page D5
Where
Hence
Lastly, the torque contribution of the bell cup is
3141.59
Now the flywheel calculations will be performed.
The moment of inertia of the flywheel is given by the following equation:
Where
Hence
Lastly, the torque contribution of the flywheel is
Finally, these values can be summed to get a total gyroscopic torque value
Thus the spray operator’s pendulum motion will be opposed by a total torque if 0.563 Nm
D.3 Center of Gravity
A major concern of this gun was its center of gravity. The goal was to get it as close
to the center of the handle as possible in order to reduce the amount of torque on the user’s
wrist. Solidworks is capable of calculating an assemblies center of gravity but the material
of each part would need to be defined. Solidworks did not contain all the materials that
Page D6
were used in this prototype so similar materials were chosen to at least determine a rough
value for the center of gravity.
A simple string test was utilized to determine a more accurate value. The prototype
was hung from the ceiling by string in two different positions. Pictures were taken of these
two positions and then overlaid in the same position using Microsoft PowerPoint, in figure
D1. Then lines were added to extend the string’s axis through the body of the prototype.
The intersection of these two lines provided the center of gravity. If the prototype were to
be cut in half along the z-y plane defined in the image below, the two sides would be mirror
images. Since it is symmetric along this plane, a third position was not necessary to
determine the center of gravity.
Z-axis
X-axis
Y-axis
Figure D1: The two images of the prototype hanging by string showing their intersection
The rough center of gravity provided by Solidworks was on the front of the
trigger where it appears to touch the housing. After conducting this image analysis, the
center of gravity is on the back of the trigger where it appears to touch the housing. This is
relatively close to the center of the handle and contributes to the low wrist torque values.
F.1 Team EFC: Handheld Rotary Atomizer Assembly Instructions
Page F1
Page F2
F.2 Motor Assembly and Placement
1. Place o-rings into the slots on each side of the Air-Bearings, then Place Air-Bearings onto
each end of the Shaft.
2. Place the Motor Assembly into the cavity in the handle. Make sure that the back AirBearing is flush against the back wall and that the front Air-Bearing is flush with the
front of the gun. Also make sure that the Paddle-Wheel sits in the Paddle-Wheel cavity.
F.3 Bell Cup Assembly
1. Hand thread on the Bell Cup.
2. Use a 20mm wrench to hold the shaft in place.
3. Hand tighten to stop.
Page F3
Page F4
F.4 Air Ring Collar Assembly
1. Place the Collar onto the front of the gun, roughly line up the holes.
2. Insert a screw into one of the four holes shift orientation of Collar as necessary until the
screw falls into place.
3. Hand tighten screw down and repeat for other four screws.
4. Using a 3mm hex key tighten the bolts down 1 turn at a time in start pattern to insure
uniform tightening. The bolts should be turned a total of 2 turns.
F.5 Shaping Air Ring Assembly
1. Screw the Shaping Air Ring onto the Collar until stop.
Page F5
Page F6
F.6 Needle and Tube Assembly
1. Slide the Needle and tube assembly into the back of the gun as shown, until firmly seated
in the back of the gun.
Page F7
F.7 Trigger Assembly Instructions
1. Slide Trigger and Linkage from the bottom of the handle as shown.
2. Stretch the Trigger posts out and slide the holes onto the trigger pinion on the top of the
gun.
3. Slide the center hole in the trigger linkage over the threaded end of the needle.
4. Place the washer on the threaded end of the needle.
5. Thread the nut onto the needle and hand tighten down.
F.8 Back Assembly
1. Place the spring over the threaded end of the needle and place the Back piece on.
2. Insert the screws into the holes and hand tighten down.
3. Using a 3mm Hex Key, tighten down the screws a total of 2 turns each.
Page F8
Appendix G: Cost Analysis
Page G1
G.1 Estimated Cost of Prototype
The design team consulted with EFC engineers and machinists to estimate the final
cost of the prototype. The cost was separated into 5 main components: raw material,
machine programming, manufacture, assembly, and miscellaneous parts. Considering all of
these categories, the design team estimates the cost of the prototype to be $6350. The cost
analysis is summarized in Table _.
Table _: Breakdown of Projected Prototype Cost
Subcomponent
Raw Material
Machine Programming
Manufacturing Motor
Handle
Housing
Shaping Air Shroud
Bell Cup
Assembly
Miscellaneous Parts
Total Cost
Time (h)
-40
10
4
2
2
4
2
--
Hourly Rate ($/h)
Sub-Cost ($)
-500
100
4000
75
750
75
300
75
150
75
150
75
300
75
150
-50
6350
G.2 Actual Cost of Prototype
Pure machinine from bulk material stock.
Programming and design rate: $125/hr
Manufacturing and assembly rate: $75/hr
Component
Material
Shaft
Air Bearings
Housing
AL 6061-T6
Carbon
7" dia x 6" L Black
Acetron GP
Paint
Injection
Tube
Paint
Injector
Shaping Air
Ring
Back Cover
Trigger Post
Trigger
Trigger
2.5” dia. x 5”L
Black Acetron GP
.5” dia. x 1.5” L
Black Acetron GP
2” dia. x 1.0” L
Black Acetron GP
2.5” dia. x 2.0” L
Black Acetron GP
3/8” dia. x 2.0” L
Black Acetron GP
5.25” dia. x 3” L
Nylatron, Blue
.5” dia. x 2.0” L
Material
Cost
$4.00
$40.00
Design
(h)
0.50
0.50
Programming (h)
2.00
2.00
Set-up
(h)
2.50
2.50
Manufacturing (h)
0.75
0.83
$45.00
4.00
5.00
2.00
2.75
$2.00
1.00
2.50
3.83
0.68
$0.75
1.00
1.00
3.50
0.17
$0.50
0.50
1.17
1.67
3.02
$1.00
1.00
1.50
1.50
0.38
$0.50
0.25
0.50
0.25
0.25
$17.50
0.50
1.00
0.50
0.50
$0.50
0.25
0.50
0.50
0.25
Quantity
1
2
Sub-Cost
$560.25
$705.00
1
$1,526.25
1
$778.00
1
$525.75
1
$560.50
1
$454.75
2
$151.00
1
2
$280.00
$169.75
Linkage
Trigger
Spring
Paint Needle
and Tip
Drive Air
Valves
Bell Cup
Bell Cup
Insert
Outer
Shroud
O-rings
Shaping Air
Ring Screws
Shaft
Coating
Assembly
Total Cost
Page G2
Black Acetron GP
St. Steel
$2.00
0.00
0.00
0.00
0.00
Black Acetron &
316 St. Steel
$4.00
0.25
0.75
0.25
0.28
Black Acetron GP
$0.35
0.50
0.00
0.00
0.00
1 ¼ dia. x 2” L
Titanium, Grade 5
$11.00
0.00
1.00
0.50
1.50
Black Acetron GP
$0.85
0.00
0.50
0.25
0.20
2.5" dia x 1.7" L
Black Acetron GP
Tekrez®
M3 x 8mm L Cap
Screw, St. Steel
$2.00
1.00
2.50
2.50
1.57
1
$15.00
0.00
0.00
0.00
0.00
1
$744.50
$15.00
$0.25
0.00
0.00
0.00
0.00
4
$1.00
Nickel + Diamond
$116.67
0.00
0.00
0.00
0.00
1
0.00
0.00
0.00
0.25
1
--
1
$2.00
1
$169.00
2
$63.20
1
$286.00
1
$97.10
$116.67
$18.75
$7,073.05
G.3 Projected Costs for Large-Scale Manufacture
Traditional Manufacturing: Pure machining
Using the set-up and manufacturing costs, but programming and design have already been
done.
Component
Shaft
Air Bearings
Housing
Paint Injection Tube
Paint Injector
Shaping Air Ring
Back Cover
Trigger Post
Trigger
Trigger Linkage
Trigger Spring
Paint Needle and Tip
Drive Air Valves
Bell Cup
Bell Cup Insert
Outer Shroud
O-rings
Shaping Air Ring
Screws
Shaft Coating
Assembly
Total Cost
Cost Per Gun
Material
AL 6061-T6
Carbon
7" dia x 6" L Black Acetron GP
2.5” dia. x 5”L Black Acetron GP
.5” dia. x 1.5” L Black Acetron GP
2” dia. x 1.0” L Black Acetron GP
2.5” dia. x 2.0” L Black Acetron GP
3/8” dia. x 2.0” L Black Acetron GP
5.25” dia. x 3” L Nylatron, Blue
.5” dia. x 2.0” L Black Acetron GP
St. Steel
Black Acetron & 316 St. Steel
Black Acetron GP
1 ¼ dia. x 2” L Titanium, Grade 5
Black Acetron GP
2.5" dia x 1.7" L Black Acetron GP
Tekrez®
M3 x 8mm L Cap Screw, St. Steel
Nickel + Diamond
--
Alternative Manufacturing Processes:
Cost: 100 Guns
$6,100.00
$20,575.00
$25,200.00
$5,400.00
$1,400.00
$2,856.25
$4,156.25
$1,362.50
$5,537.50
$2,112.50
$200.00
$2,543.75
$70.00
$12,425.00
$1,603.75
$3,131.25
$1,500.00
$100.00
Cost: 500 Guns
$30,200.00
$102,575.00
$125,700.00
$26,700.00
$6,700.00
$14,056.25
$20,556.25
$6,762.50
$27,537.50
$10,512.50
$1,000.00
$12,643.75
$350.00
$61,825.00
$7,943.75
$15,431.25
$7,500.00
$500.00
Cost: 1000 Guns
$60,325.00
$205,075.00
$251,325.00
$53,325.00
$13,325.00
$28,056.25
$41,056.25
$13,512.50
$55,037.50
$21,012.50
$2,000.00
$25,268.75
$700.00
$123,575.00
$15,868.75
$30,806.25
$15,000.00
$1,000.00
$11,667.00
$1,250.00
$109,190.75
$1,091.91
$58,335.00
$6,250.00
$543,078.75
$1,086.16
$116,670.00
$12,500.00
$1,085,438.75
$1,085.44
Injection molded handle and pressed carbon bearings
Break even point:
Reduces costs for 1000 guns
Page G3
References
Page i
References (?EDIT AT END)
[1] EFC Systems. EFC Graphic. JPEG Digital image. EFC Systems USA. Web. 01 Nov. 2010.
<http://www.efcusa.com/>.
[2] Tanner, Franz X. Schematic image of pressure driven spray. Digital image. Atomization
and Droplet Breakup Modeling of Diesel Sprays of. Michigan Tech, 04 Feb. 1999. Web.
01 Nov. 2010.
<http://www.math.mtu.edu/~tanner/Research/Atomization/poster_new/index.ht
ml>.
[3] "Midway Industrial Supply - Spray Guns Overview." Paint Spray Equipment: Spray Guns,
Booths, Finishing Systems. Web. 12 Sept. 2010.
<http://midwayis.com/spraygun.htm>.
[4] "Coating Equipment & Processes." International Equipment & Trade Credit
Financing !! Web. 12 Sept. 2010. <http://www.etfinancial.com/coatingsequip.htm>.
[5] "Hvlp vs Conventional Spray Guns Hvlp vs Air Assisted Airless." HVLP Spray Guns and
Paint Spayers - DeVilbiss Sharpe Binks Iwata Asturo Finest HVLP and Reduced
Pressure Spray Guns. Web. 12 Sept. 2010.
<http://www.spraygunworld.com/Information2/AAA/AAA vs hvlp vs rp.html>.
[6] "DeVilbiss Compact Pressure Feed HVLP Spray Gun." Welcome to DeVilbiss. Web. 12
Sept. 2010.
<http://www.devilbiss.com/Products/SprayGuns/ManualSprayGuns/HVLP/Compa
ctPressureFeed/tabid/1035/Default.aspx>.
[7] FS40R Rotary Atomizer Operation Manual. PDF.
[8] EFC Systems. FS16 Robot Mounted Electrostatic Rotary Atmoizer. Havre De Grace:
Electrostatic Finishing Components & Systems. PDF.
[9] EFC Systems. EFC Systems Introduces the FS30 Replacement Parts. Havre De Grace: EFC
Systems, Inc., Dec. 2008. PDF.
[10] EFC Systems. Air Bearing Motor Operation. PDF.
[11] Slocum, Alexander H. "Aerostatic Bearings." Precision Machine Design. Englewood
Cliffs, NJ: Prentice Hall, 1992. 580-625. Print.
[12] Patent 5803372. Print.
References
Page ii
[13] Patkin, Michael. A Check-List for Handle Design. Ergonomics Australia, 2001. PDF.
[14] "Model 2100 Manual Conventional Air Spray Gun From Binks." ITW Binks Spray
Finishing Equipment. Web. 12 Sept. 2010.
<http://www.binks.com/Products/SprayGuns/ManualSprayGuns/AirSpray/Model
2100/tabid/195/Default.aspx>.
[15] National Emission Standards for Hazardous Air Pollutants: Paint Stripping and
Miscellaneous Surface Coating Operations at Area Sources. Washington:
Environmental Protection Agency, 9 Jan. 2008. PDF.
[16] Waterborne Coatings. Sacramento: Department of Toxic Substances Control, Sept.
2006. PDF.
[A1] The Ergonomics of Spray Guns - Users' Opinions and Technical Measurements on Spray
Guns Compared with Previous Recommendations for Hand Tools. Elsevier:
International Journal of Industrial Ergonomics, 26 Feb. 1999. PDF

MEEG 401: Phase Three Report

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