a gasless method of spraying thermoplastic resin
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Theses and Dissertations
2005-11-28
A Gasless Method of Spraying Thermoplastic Resin A Gasless Method of Spraying Thermoplastic Resin
Dan T. Rogers Brigham Young University - Provo
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A GASLESS METHOD FOR SPRAYING
THERMOPLASTIC RESINS
By:
Dan T. Rogers
A thesis submitted to the faculty of
Brigham Young University in partial fulfillment
of the requirements for the degree of
Master of Science
School of Technology
Brigham Young University
December 2005
Copyright © Dan T. Rogers
All Rights Reserved
BRIGHAM YOUNG UNIVERSITY
GRADUATE COMMITTEE APPROVAL
of a thesis submitted by
Dan T. Rogers
Each member of the following graduate committee has read this thesis and by majority vote it has been found to be satisfactory. ______________________________ __________________________________ Date Perry W. Carter, Chair ______________________________ __________________________________ Date Kent E. Kohkonen ______________________________ __________________________________ Date A. Brent Strong ______________________________ __________________________________ Date Michael Swenson (Minor)
BRIGHAM YOUNG UNIVERSITY
FINAL READING APPROVAL
As chair of the candidate’s graduate committee, I have read the thesis of Dan T. Rogers in its final form and have found that (1) its format, citations, and bibliography style are consistent and acceptable and fulfill university and department style requirements; (2) its illustrative materials including figures, table, and charts are in place; and (3) the final manuscript is satisfactory to the graduate committee and is ready for submission to the university library. __________________________ _______________________________________ Date Perry W. Carter, Chair Graduate Committee Acceptance for the Department _______________________________________ Thomas L. Erekson Director, School of Technology Accepted for the College _______________________________________ Alan R. Parkinson
Dean, Ira A. Fulton College of Engineering and Technology
ABSTRACT
A GASLESS METHOD FOR SPRAYING
THERMOPLASTIC RESINS
Dan T. Rogers
School of Technology
Master of Science
This spraying method for thermoplastic resins is a new manufacturing process for
applying thermoplastics to a mold or surface in an efficient way that has the potential of
reducing cycle time. Spraying thermoplastic resins is similar to spraying other polymers,
such as paint, with the differences being higher pressure and temperature. This method
uses an injection molding machine with a modified nozzle to spray the plastic material.
In this study, temperature, pressure, and nozzle size were factors that influenced the
success of this spraying method.
The method of spraying in this study proved spraying without a gas is possible, a
statistical analysis of a series of sprayed samples was performed, and a summary
of the results is presented. This study is the only known method to use these procedures.
The purpose of this thesis is two fold. First, its purpose is to achieve a method of
spraying thermoplastic resins without the use of a combustible material. Second, if the
spraying method is found to be possible, the thesis investigates what factors, of those
selected; have a significant influence on the result?
There are other types of spraying plastic methods used currently in industry. One
such method, described in the project, is called Flame Spraying. This method, as well as
others, has proven to be useful in protecting metals, wood, and other materials from harsh
environmental and chemical elements.
The results of this study proved that gasless spraying of thermoplastic resin is
indeed possible and with further research this method can lead to a new manufacturing
process for producing plastic parts or coatings. Future studies can include modifying
factors such as temperature, plastic, pressure, tooling, and methods.
ACKNOWLEDGEMENTS
I want to thank several people who have made this thesis possible. Though some
may think that this has been an individual project in doing the research, writing, and
defending it, it has not been so. I am indebted to those who contributed to this project, in
direct and indirect ways, in the forms of ideas, feedback, and support. I first of all would
like to thank Perry Carter, whose influence had intrigued me to enter the masters
program, for his support and guidance through the last several years. I would also like to
thank my other committee members, Kent Kohkonen, Brent Strong, and Michael
Swenson for their suggestions, patience and flexibility. Also, a special thanks to Prof.
Paul Fields who helped make sense of the statistical analysis that I had started. I want to
thank my parents for their support and for the way that they taught me to live by hard
work and by enduring and their constant prodding and for their examples of how they
live their lives.
Most of all I want to thank my wife, Chen-Ju (Jonnice), for her faith in me to
complete this work, for the many trying times, and for her love and support. Finally, I
would like to thank my children Ian, Maiya, and Chelsea for the joy that they bring in my
life and for the all the times where this project took a back seat and they came first.
viii
Table of Contents
ABSTRACT........................................................................................................................ v
ACKNOWLEDGEMENTS.............................................................................................. vii
LIST OF TABLES............................................................................................................. xi
LIST OF FIGURES .......................................................................................................... xii
Chapter 1: The Problem...................................................................................................... 1
Introduction................................................................................................................. 1
Statement of problem.................................................................................................. 2
Contributions to be made by this thesis……………………………………………...3
Questions to be answered............................................................................................ 3
Delineation of the research project ............................................................................. 3
Definition of terms ...................................................................................................... 4
Chapter 2: Review of related literature............................................................................... 7
Historical background................................................................................................. 7
Flame spraying............................................................................................................ 9
High velocity oxyfuel (HVOF) ................................................................................. 12
Detonation gun spraying ........................................................................................... 14
Electric arc ................................................................................................................ 14
Conventional plasma spraying.................................................................................. 16
Vacuum plasma spray forming (VPSF) .................................................................... 17
Cold spraying ............................................................................................................ 18
ix
Summary of literature reviewed………………………………………..…………...19
Analysis and review of previous work in the field ................................................... 23
Chapter 3: Methodology or procedures ............................................................................ 25
Method followed……………………………………………………………………25
Description of research methodology or approach ................................................... 26
Research design ........................................................................................................ 26
Step by step method .................................................................................................. 35
Pilot studies .............................................................................................................. .38
Data collection and recording ................................................................................... 38
Statistical analysis ..................................................................................................... 39
Limitations ................................................................................................................ 40
Chapter 4: Findings........................................................................................................... 43
Findings……………………………………………………………………………..43
Statistical definitions of Terms ................................................................................. 43
Split plot experiment................................................................................................. 44
Response rank vs. run order...................................................................................... 48
Chi-squared test ........................................................................................................ 49
Regression summary................................................................................................. 50
F-test ......................................................................................................................... 51
Thickness by location ............................................................................................... 52
Interaction plot .......................................................................................................... 53
Effect of nozzle size on average thickness………………………………………….54
Velocity of material .................................................................................................. 55
x
Visual appearance of the specimens ......................................................................... 56
Chapter summary ...................................................................................................... 57
Chapter 5: Summary, Conclusions, Recommendations.................................................... 59
Brief summary .......................................................................................................... 59
Conclusions............................................................................................................... 60
Recommendations for further research ..................................................................... 61
Appendix........................................................................................................................... 65
Bibliography ................................................................................................................... 111
xi
LIST OF TABLES
Table 1: Comparison of thermal spray processes ……………………………………... 22
Table 2: Factor setting…………………………………………………………………..26
Table 3: Nozzle opening sizes ………………………………………………………….32
Table 4: Nozzle angle …………………………………………………………………..33
Table 5: Unipol DNDA-1107 Polyethylene, LLD ……………………………………...35
Table 6: Split plot design for spraying thermoplastic resin …………………………….40
Table 7: Split plot analysis diagram …………………………………………………....46
Table 8: Specimen thickness and variance data ………………………………………..47
Table 9: Effects of factors used in this study …………………………………………..48
Table 10: Chi-square analysis ……………………..…………………………………...49
Table 11: Regression analysis data …………………………………………………….50
Table 12: F-test analysis data …………………………………………………………..51
Table 13: Friedman test—thickness by location ……………………………………….52
Table 14: The 8 combinations of settings………………………………………………54
xii
LIST OF FIGURES
Figure 1: Metal and plastic spraying timeline…………………………………………….7
Figure 2: Spraying processes……………………………………………………………..8
Figure 3: Schematic of the wire flame spray process…………………………………….9
Figure 4: Diagram of wire flame spray tooling……………...………………………….10
Figure 5: Schematic of the powder flame spray process………………………………..10
Figure 6: Powder spraying tooling………………………………………………………11
Figure 7: High velocity oxyfuel spraying process………………………………………12
Figure 8: High velocity oxyfuel spraying……………………………………………….13
Figure 9: Detonation spraying gun diagram…………………………………………….14
Figure 10: Equipment for electric arc spraying…………………………………………15
Figure 11: Electric arc spraying process……………………………………………..…16
Figure 12: Plasma spray process………………………………………………………..17
Figure 13: Plasma sprayed parts………………………………………………………..17
Figure 14: Plasma spraying process schematic…………………………………………18
Figure 15: Cold spray gun………………………………………………………………19
Figure 16: Van Dorn injection molding machine……………………………………….27
Figure 17: Cross section of injection screw……………………………………………..27
Figure 18: Temperature control panel…………………………………………………..28
Figure 19: Control panel on injection molding machine………………………………..29
Figure 20: Spraying nozzle in location………………………………………………….30
xiii
Figure 21: Graphic of nozzle holder…………………………………………………….30
Figure 22: Steel nozzle holder…………………………………………………………..31
Figure 23: Spray nozzles………………………………………………………………..31
Figure 24: Nozzle opening……………………………………………………………...32
Figure 25: Nozzle angle…………………………………………………………………33
Figure 26: Pulling mechanism…………………………………………………………..36
Figure 27: Motor controller……………………………………………………………..36
Figure 28: Specimen 11 spray…………………………………………………………..37
Figure 29: Specimen 4 spray……………………………………………………………37
Figure 30: Specimen 7 spray……………………………………………………………37
Figure 31: Specimen 14 spray…………………………………………………………..37
Figure 32: Specimen 20 spray…………………………………………………………..38
Figure 33: Specimen 23 spray…………………………………………………………..38
Figure 34: Specimen 28 spray…………………………………………………………..38
Figure 35: Specimen 32 spray…………………………………………………………..38
Figure 36: Response versus run order…………………………………………………..48
Figure 37: Regression summary………………………………………………………...51
Figure 38: Mean thickness by location………………………………………………….52
Figure 39: Variance of thickness by location…………………………………………...53
Figure 40: Interaction of pressure and temperature……………………………………..53
Figure 41: Average thickness to factor settings………………………………………....54
Figure 42: Thickness variance to factor settings……………….…..………...………….55
xiv
Figure 43: Average velocity in mph per settings………………………...……………...56
Figure 44: Visual comparison versus weight……………………………………………56
1
Chapter 1
The Problem
Introduction
For decades, the spraying of polymers using a gas has been an efficient way of
applying protective coatings to surfaces such as walls, automobile panels, and structures.
These polymers include paints, foams, resins, and plastics. Most coatings are as thin as
1/32”, but can be several inches thick. These types of polymers are mixed using a static
mixer and then forced through a nozzle or they are flame sprayed by the use of a
flammable gas. Either way, the particles are atomized before they hit their target.
The method of spraying in this thesis is to melt a polyethylene material and apply
a pressure to cause it to eject through a nozzle at a sufficient speed to cause atomization.
This method avoids the use of hazardous gases which are used in most spraying methods.
The spraying of thermoplastic resin has been practiced for about 30 years.
Sprayed resins provide a protective coating for woods, metals and other materials from
harsh environmental elements. They may also provide protection in an environment
where high wear is common.
The most common methods for spraying plastics rely on a process called thermal
spraying. Thermal spraying consists of feeding small, granule-size beads through a flame
where they melt and are carried by a high-velocity jet of gas to a target. There are several
2
types of thermal spraying, namely: plasma spraying, high velocity oxy-fuel (HVOF),
plastic flame spraying and several others.
The thermal spraying process is not common and there are several people and
companies vying for the right to stick a formal name to it. Current names are: plastic
flame spraying (PFS), thermal spraying, and hot spraying. Further information on these
processes will be given in Chapter 2.
Statement of the problem
The thermal spraying plastic with a gas can be used in a controlled environment;
however, accidents can cause structural damage or physical injuries. These unexpected
events can be costly for companies and families. In addition, changes to spraying
processes to make them faster, cheaper, and better are continuous and could have
financial benefits. An alternative method to spray plastic without a gas is twofold: one,
to reduce hazards associated with gases and two, to increase the possibility of a financial
benefit.
The purpose of performing this study is threefold: 1) to spray thermoplastic
resins without the use of a gas to accelerate the particles, 2) to analyze three controllable
factors of temperature, pressure and nozzle size in a statistical analysis to find what
influences these have on the success of the process, 3) to help lead future persons to
further this study in creating new methods and parts.
3
Contribution to be made by this thesis
The contribution to be made by this thesis will be an analysis of three parameters
which affect this method of gasless plastic spraying. This information will be a source
which will lead to future applications and an evolution of this process. The addition of
this new thermoplastic molding process will compete with other plastic forming
processes such as plasma spraying, thermoforming and roto-molding as well as other
thermal spraying methods.
Questions to be answered
Five questions will be answered by this thesis. Is this process feasible? What
suggested applications and parts can this be used on or for? How do the factors in this
study influence the spraying process? What are some further studies that can be
performed? And how can gasless spraying of thermoplastic resins improve upon current
spraying processes?
Delineation of the research project
This study discusses the method of spraying thermoplastics without the use of a
gas by using a Van Dorn injection molding machine. The Van Dorn injection molding
machine is one of their earlier versions. The machine could run automatically or
manually. Tooling was made to hold the spray nozzle in place on the Van Dorn barrel
and a sliding aluminum plate was made to fit in the machine and a motorized wheel was
used to pull the plate at a constant speed. Two nozzle sizes were used and are named in
this study as smaller and larger. Two pressure settings were used the higher at 15,000 psi
and the lower at 13,600 psi. Two temperature setting were used the higher at 390º F and
the lower at 310º F. The material that was used in this project was Unipol™ DNB-1077
4
a linear low density polyethylene. A more complete description of the tooling, methods
and process is given in Chapter 3.
The objective of this study was to produce a method of spraying thermoplastic
panels without the use of a gas. A statistical analysis was performed comparing nozzles,
temperature, and pressure. The specimens were compared by their weights, uniformity,
and thicknesses and were evaluated by measurement and visual methods. Surface
preparation of the target material was not a factor that was analyzed.
Definition of terms
Thermal spraying- This is the main classification given for spraying of heated materials.
The processes in this method are commonly grouped in three main categories, each with
subsets: flame spraying, electric arc, and plasma spraying.
Plasma arc spraying- This process uses an extremely high temperature range
significantly higher than any known material melting point.
PFS (plastic flame spraying)- A term that is used which is synonymous with Flame
spraying.
HVOF (high velocity oxyfuel)- Consists of the use of a fuel gas and oxygen to create a
combustion temperature between 4500-5600°F. Combustion occurs at high pressures and
exits through a small opening creating a supersonic expulsion of gas and particles that
result in a dense and well bonded coatings.
LVOF (low velocity oxyfuel)- Another name for Powder flame spraying.
Hot spraying- Another term synonymous with thermal spraying, used mainly in Asia.
Arc spraying- In this process two consumable electrodes, connected to a high current
power supply are fed into a gun and make contact. The resulting arc between the two
5
electrodes melts the metal, and a stream of air moves the particles toward the target
surface.
Gasless atomization- The method, in this study, describing the spraying process without
the use of a fuel source.
Kinetic energy process- This is relatively new and includes cold spraying.
Flame powder process- A relatively slow process which melts powdered material by the
use of an oxyacetylene flame. The target material can get quite hot.
Wire flame- A flame is used to melt the material and air is used to atomize the particles.
Similar to Flame powder process, the target material can get quite hot and is just as slow.
Detonation gun- Uses a long barrel into which fuel, oxygen, and powdered feedstock is
fed into. An electric spark lights the gas and the particles shoot out the end to the target
material while keeping the target from heating up and while being energy efficient.
Conventional plasma- Also known as air plasma spray (APS). Temperatures generally
run in the 11,000-27,000°F range. Powdered material is fed into the gun by an inert gas
and is then propelled to the target surface by the plasma jet.
Vacuum plasma- similar to conventional plasma method but used in a chamber at 0.1-
0.5 atm resulting in denser and better adhesion properties.
Cold spray- The method of propelling powdered particles at a high speed to the target
material by the use of expanding gas and has relatively low temperatures (32-1470°F).
6
7
Chapter 2
Review of Related Literature Historical background
The earliest known documented records of thermal spraying are in the patents of
M.U. Schoop dating back to 1882-1889 in Zurich Switzerland. This method began with
feeding tin wires through a modified oxyacetylene welding torch. Around 1908, Schoop
patented the electric arc method and from there it took off and later developed in methods
that would accept materials in the powdered form and other methods we have today.
Currently, new methods are being developed and being improved upon. The method of
thermoplastic spraying is one branch of this that is rapidly growing. The following
timeline shows the basic advancement of thermal spraying through the last century.
Figure 1: Metal and plastic spraying timeline1
1 www.asminternational.org/bookstore, no author given.
8
Thermal spraying of thermoplastics began in earnest in the early 1980’s in
commercial settings. An ever increasing number of polymers are been sprayed including:
urethanes, ethylene vinyl alcohols, nylon 11, polytetrafluoroethylene,
polyetheretherketone, polyimide, polycarbonates, as well as several others. There are
four main categories of thermal spraying: flame spraying, plasma arc spraying, electric
arc spraying, and kinetic energy spraying, shown in the diagram below2. Within these
categories there are several methods. The three most commonly used methods used for
plastic spraying are in the flame spray category and are known as powder flame spraying,
wire flame, and high velocity oxyfuel spraying (HVOF). Other methods described in this
chapter are here for comparison, and are not suitable for spraying of polymers because of
degradation due to high heat.
2 www.asminternational.org/bookstore, author not given.
Current Thermal Spray Processes
Flame Spray Electric Arc Spray
Plasma Arc Spray
Powder Flame or LVOF
Wire Flame
Detonation Gun
HVOF
Electric or Wire Arc
Vacuum Plasma
Conventional Plasma
Cold Spray
Kinetic Energy
Figure 2: Spraying processes
9
Flame spraying
Flame spraying is the earliest method of thermal spraying and can be used in a
variety of applications and is used for both metals and plastics. The current methods in
use are either wire fed or powder fed. In either form the material is continuously fed into
the tip of the spray gun where it is melted. Lower burn temperature fuels like propane,
acetylene, or propylene are used for plastics. The differences between wire fed and
powder fed are the equipment, the rate each method deposits material, and the wire fed
method uses pressured air as the atomizing gas, whereas the powdered material method
has no atomizing stream of air.
For the continuous wire or stock feed method, the components that make this
possible are: a flame spray gun, a feeding mechanism, an air compressor and regulators,
and fuel gas and oxygen with regulators. Parts and equipment for this method are easy to
get and maintain.
Figure 3: Schematic of the wire flame spray process3.
3 http://www.usace.army.mil/inet/usace-docs/eng-manuals/em1110-2-3401/c-2.pdf, author not given.
10
For the powdered material method the equipment consists of fuel gas and oxygen
with regulators, an air compressor and regulators for the feeding of material into the gun.
Parts and equipment for this method are easy to get plus they are lighter in weight and
fewer parts are needed.
Figure 4: Diagram of wire flame spray tooling4
Figure 5: Schematic of the powder flame spray process5
4 http://www.usace.army.mil/inet/usace-docs/eng-manuals/em1110-2-3401/c-2.pdf 5 http://www.twi.co.uk/j32k/protected/band_3/ksrdh001.html, author not given.
11
Figure 6: Powder spraying tooling6.
Advantages of thermally sprayed thermoplastics are: Target material doesn’t
need to be heated or placed in a furnace, primer coats are not required. The plastic
coating covers sharp corners and surface imperfections. Can be used once cooled and
coatings have a resistance to chemical, impact and abrasions. Most surfaces are
compatible for thermal spraying; once the surfaces have been prepared they can be
sprayed from 0.002 to 0.250” thick. One layer spraying is all that is needed; the spraying
of another layer doesn’t bond well. The spraying process is quick and cooling time is
greatly reduced and the spray deposit can range from a fine grain to having an orange
peel appearance.
Disadvantages include the distribution of sprayed particles on the target material.
Thermoplastics can degrade, if it is overheated, with no visible signs. One must keep in
6 http://www.usace.army.mil/inet/usace-docs/eng-manuals/em1110-2-3401/c-2.pdf
12
the melt range for thermoplastic resins when using this tooling. Spraying layers of
material is not recommended as they do not form a good bond.
High velocity oxyfuel (HVOF)
High velocity Oxyfuel method of spraying is a common method of spraying
thermoplastics polymers according to the Handbook of thermal spray technology under
Introduction to thermal spray processing found at www.asminternational.org. Although
not much research has been done in this area when it comes to thermoplastics polymers it
appears to be a viable method to get good quality out of worn parts. This method uses a
gas fuel such as hydrogen, propylene, or propane, with oxygen to create a combustion
reaction with temperatures reaching the 4500-5600°F range. The shape of the gun, as
shown in figure 7, creates a high pressure combustion chamber when the equipment is in
use. With a small opening, the gases escape at a high velocity and it’s known for the high
kinetic energy it gives to the sprayed materials as they pass through the gun. Because of
this feature, the results are an extremely dense and well bonded coating, which makes it a
common method for several applications.
Figure 7: High velocity oxyfuel spraying process7
7 http://www.gordonengland.co.uk/hvof.htm, author not given.
13
Figure 8: High velocity oxyfuel spraying8
Advantages that come from using this method are lower production costs in the
forms of minimized down-time, waste reduction, and increased productivity.
Disadvantages are the hazards that come from using equipment and materials in a
combustion setting and are similar to what you would find in a welding environment.
The process creates high decibel ranges and ear plugs and other preventative measures
must be taken to conform to OSHA standards. Radiation in the wavelengths of UV and
IR occur and the covering of eyes and exposed skin is necessary to prevent eye damage
and burns. Eye shades from 3-6 for combustion and 9-12 for electrical processes are
recommended9. Fire is a common hazard use caution when handle equipment.
Mechanical hazards that deal with surface preparation, cleaning, spraying, finishing, etc.,
consult MSDS (Material Safety Data Sheets) for potential hazards. Finally, compressed
gases require safe handling and the use of proper equipment.
8 http://www.gordonengland.co.uk/hvof.htm, author not given. 9 American Welding Society, http://www.aws.org/technical/facts/FACT-20.PDF, author not given.
14
Detonation gun spraying
The process of detonation spraying is simple and the process yields extremely
good results and is used with metals. The process beings with a nitrogen purged gun
barrel then a fuel gas is inserted into the barrel along with powdered material and oxygen.
The spark plug ignites the mixture and the particles travel the length of the gun and are
deposited on a surface. The result is a dense low oxide coating.
Equipment used in this method are: a water cooled 1 meter gun, a spark source,
powder, nitrogen, fuel and oxygen sources, figure 9 Advantages are a dense low oxide
coating and low fuel consumption. The disadvantages however are much more
numerous. It is costly to run this equipment, the spray rate is extremely slow, power
consumption is high, and energy needed to melt the particles is high.
Figure 9: Detonation spraying gun diagram10
Electric arc
Electric arc spraying is one of the most economical methods of applying a
sprayed coating and is used with metals. It is simple fast and easy to use, set up, and it
doesn’t use a fuel gas. Equipment that is necessary is common to most manufacturing 10 http://www.gordonengland.co.uk/ds.htm, author not given.
15
settings. The operation of this method is uses an electrical source and an air source.
How this operation works is quite simple. The gun can be set to feed the material into the
gun at a specified speed according to the type of material that is used. Each wire is
charged, one positive and the other negative. As the material is fed through the gun the
two wires come close enough in proximity to each other and an arc is created, this is a
continual process as long as there is an electrical source. When this happens the material
is melted and compressed air atomizes the material and carries it to the target11.
Figure 10: Equipment for electric arc spraying
Applications include rebuilt or resurfaced coatings, bonding, conductivity
coatings, corrosion resistance and antiskid coatings. The benefits include minimal
equipment and few consumables; many types of materials can be used in this method; it
is a easy to use, operate, move and it’s reliable; it also is produces excellent coatings, can
be applied to large structures, and has a high production rate.
11http://www.sulzermetco.com/eprise/Sulzermetco/Sites/Products/AboutThermalSpray/arcwire.html
16
Figure 11: Electric arc spraying process12
Conventional plasma spraying
Commonly called atmosphere plasma spray (APS), this method operates at an
extremely high temperature range between 11,000 to 27,000ºF, which is well above any
known material melting point and used on metals. The gun uses several consumables,
like water, an inert gas like argon, nitrogen, helium or hydrogen, electricity, and
powdered material, this method is quite expensive to operate and maintain. Plasma
spraying has several advantages in that it can spray high melting point materials such as
tungsten and ceramics13. Plasma sprayed coatings are much denser, stronger and cleaner
than the other thermal spray processes, except HVOF and detonation processes, it has a
wide range of applications and it is versatile. The only drawbacks are that it is expensive
and somewhat complex.
12 http://www.gordonengland.co.uk/aws.htm, author not given. 13 http://www.pyrogenesis.com/vpsforming.htm, author not given.
17
Figure 12: Plasma spray process14
Vacuum plasma spray forming (VPSF)
Another plasma spraying method is performed
in a vacuum chamber with an inert gas and is
sometimes called ‘low pressure plasma spraying’
(parts are to the right15). This method is much like
APS except at low pressures. Low pressure plasma
spraying creates a dense even coated and clean part.
The absence of oxygen prevents some materials from
undergoing rapid oxidation during the process. Common parts made by this method are
rotated cylindrical objects as seen in Figures 12, 13 and 14. Both plasma spraying
methods are excellent in creating rapid prototype parts.
14 http://www.gordonengland.co.uk/ps.htm, author not given.
Figure 13: VPSF parts
18
m andrel p recond ition ing
deposition o f layers
rem oval o f m andrel
near-net-shape fo rm edcom ponent
Figure 14: Plasma spraying process schematic15
Cold spraying
The cold spraying method, or ‘room temperature spraying’, is one that uses
temperatures much lower than conventional methods of flame spraying. The use of this
method bypasses effects of high temperature. These effects include melting, oxidation,
vaporization, crystallization, gas vapors, and residual stresses. The process takes the
spraying material and by the use of a gas it converges to a point in the gun where
supersonic speeds are reached, see figure 15. The material is then propelled to the target
the particle hits with such great force that it creates a bond.
15 http://www.pyrogenesis.com/vpsforming.htm, author not given.
19
Figure 15: Cold spray gun16
Advantages that come from this technology includes low material oxidation,
retention of the original material properties, it has a high rate of deposition, high density
and hardness. Residual stresses are low and the coatings can be fatigue and corrosion
resistant. It provides greater wear resistance and can be applied to ceramics and glass17.
Some disadvantages include high gas consumption, harder materials cannot be
sprayed, some surfaces cannot hold sprayed material, and there is little information about
this procedure since it is a relatively new process. It is possible this method could be
used with thermoplastic resins. This is a new method and no studies have been found
using this tooling with thermoplastic resins.
Summary of literature reviewed
Powder flame spraying or (LVOF) and wire flame are the most common
methods to spray thermoplastic resins. They are the oldest method of thermal spraying
and parts and services are easily procured which help maintain a lower cost to maintain
the set up. Materials can be powdered or feedstock. For polymers it is suggested to use
16 http://www.cmit.csiro.au/innovation/2003-08/cold_spray.cfm, no author given.
20
in powered form. Once sprayed the material has low cohesive strength and high porosity
when compared to other methods.
High velocity oxy-fuel is another method that is common in spraying polymers
provided that the polymer is in powdered form. This method provides a more dense
coating and powdered or feedstock material can be used.
Detonation gun produces high strength and well bonded coatings that are dense.
Not commonly used to spray polymers. The process is slow, has high costs and the
system is not easily portable.
Electric arc is an energy efficient process when using conductive materials. It
doesn’t use a fuel gas. The system can run on electricity only. Advantages are simple
setup, low cost to maintain. Target temperature remains relatively low as to other
methods. It is not an easy method to spray polymers.
Conventional and vacuum plasma runs at extremely high temperatures that are
not suitable for polymers but are useful for other high melting point materials. These
methods produce high density coating that is stronger and cleaner than other methods,
except for HVOF and detonation processes. The system is expensive and complex to
operate, and is not easily moveable. They can deposit material at a high rate of speed.
Cold spray is the newest method that is performed at room temperature and
bypasses the effects of high temperature, which are melting, oxidation, vaporization,
crystallization, gas vapors and residual stresses. Disadvantages are: it has high gas
consumption and harder and higher melt temperature materials don’t do well using this
method. Due to the lack of research of this method, little information about it is
available.
21
The following table gives comparative information between each of the methods
listed above with the exception of cold spraying. Cold spraying information that was
found is added following the table.
22
Cold spraying has a gas flow ranging between 500-1500 m/s. Adhesive strength rivals that of HVOF and plasma spraying. Oxide content remain low with little oxidation taking place and remains in the 1-2% range. Maximum spray rate is about 15-16 kg/h. Table 1 was taken from www.asminternational.org/bookstore, author not given.
23
Analysis and review of previous work in the field
Nothing was found in the search for methods of gasless spraying of thermoplastic
resins and it is concluded that no one has reported anything like this in the past. As
stated in this chapter there are gas-atomization methods of spraying plastic that result in
nearly the same end product as gasless spraying.
Other industries which have similarities, and have shown to contribute to this
method are the airless paint spraying industry. And specifically, company called
International Paint who applies Chartek 7® has a method that has shown to be beneficial
in the spraying of highly viscous materials.
Airless paint spraying, in concept, is similar to the gasless method of spraying
thermoplastic resins with a difference of temperature. The airless paint spraying industry
has made much progress in developing nozzles for their industry. Nozzle sizes have
proven useful in applying them to the spraying of thermoplastic resins. Nozzles and
pressures must be monitored and regulated for a good coating.
A company called International Paint also shows that nothing is impossible
especially in their unique method of spraying a viscous material at extremely high
pressures. Their material, called Chartek-7™, is an intumescent material they spray onto
the structural surfaces of offshore oil rigs, refineries, tanks and several other structures
needing protection from fire and effects of harsh environmental elements. Their
procedure requires the use of a team of up to 4 people spraying and trolling the material
into place with the use of a wire mesh substrate. Controlling their process is critical and
downtime is costly. The material they spray is a thick two part epoxy material that is
heated between 120-160°F, rationed out by the use of a displacement pump, fed through
24
heated hoses to a mixing manifold and mixed by an inline static mixer. From this point
the material is fed to a high pressure airless spray gun and sprayed at a minimum of
7000psi and up to 13 gallons per minute17. A key thing to know about this material is
that it is a lightweight cementitious material that has the tendency to start curing as soon
as it is mixed. It has the consistency similar to peanut butter and appears to have sand
and short fibrous material well mixed together. Their nozzles are special made out of
carbide and range in the 1/4” – 5/8” range and they wear out quickly. This material is
relatively heavy and vicious. Keeping their equipment clean is extremely important; not
cleaning their equipment after use is costly. Applying their methods to the spraying of
thermoplastic resins may be of benefit.
17http://www.chartek.com/specsapps/Spec/PFPMats&App.pdf, no author given.
25
Chapter 3
Methodology or Procedures
Method followed
In this research, a modified injection-molding machine was used to preheat a
polyethylene thermoplastic resin and apply the force needed to cause the material to
atomize as it travels through a nozzle. The material used in this study was a low-
viscosity polyethylene called Unipol™ DNDB-1077. The target area consisted of a 1/2
inch aluminum sheet which was moved in front of the spraying nozzle to produce a
sample used in the evaluation of the spray quality. The parameters in this study that were
altered were the melt temperature of the thermoplastic resin, the pressure applied, and the
nozzle size. Each of these will be described further in this chapter.
A statistical analysis was performed to measure the parameters listed above, to
find out what effects these factors will have on the quality and what interactions that
there may be between them. It consisted of a 2 level analysis, assigning a high and low
level for each of the parameters. The parameters were limited to the three factors to see
which had the greater influence on spray quality; these are shown in Table 2. The
analysis had 8 different possible settings with a total of 4 samples made of each of these
setting. A total of 32 samples were made and evaluated.
26
Table 2: Factor settings
Low pressure of 13,600 psi
High pressure of 15000 psi
Small nozzle: opening size of .000124171 (#15)
Large nozzle: opening size of .000225134 (#10)
Low Temperature of 310ºF
High temperature of 390ºF
An inspection of the samples was done by a statistical analysis of the spray
pattern uniformity and a visual inspection of the resulting samples. The visual inspection
judged the evenness and how uniform the plastic samples were. Uniformity is how flat
and even the thickness of the samples were.
Description of research methodology or approach
The approach to this thesis, a gasless method of spraying thermoplastic resin, was
experimental. The idea of spraying thermoplastic resin without a combustible gas was
accomplished by heating the resin then spraying it through a nozzle at a high enough
pressure to cause the material to atomize and create panels, which will be called samples
or specimens in this document. Further details of methods and materials are discussed in
this chapter.
Research design
The equipment and materials which made this study possible were the machine
that was used, the spraying material and a few custom made tools. The Van Dorn
injection molding machine shown in Figure 16, (serial # 3471-35-307, Lot # 11, Model #
H-300) was used to spray the plastic material. This machine, like many others, is
operated by hydraulics of up to 2000 psi. The hydraulic cylinder is attached to a screw
which allows for the movement of material through the system.
27
Because of the difficulty of disassembling the machine a rough estimate was used
to find the forces that were acting on the material. The main cylinder has a diameter of
about 5.5 inches with a total area of about 24 in2. The screw cylinder is estimated to be
about 2 inches in diameter and has about a 3 in2 total area. By using these numbers the
pressure acting upon the material is calculated to be approximately 13,600 psi at the
lower pressure setting and 15,000 psi at the higher pressure setting.
Figure 16: Van Dorn injection molding machine
A hopper allows for the entry of material into the system. When the system is in
operation the material is heated and extruded through the nozzle at a high pressure, see
Figure 17.
Figure 17: Cross section of injection screw
Nozzle Holder
Screw Hopper
Hydraulic Cylinder
Spray Nozzle
28
Temperature is controlled by the control panel, Figure 18. There are 4
temperature zones along the screw and they are labeled as: nozzle, front, middle, and
back. If the temperature setting for the material calls for an extrusion setting between
370-390ºF then the settings may be according to the following: nozzle: 380ºF, front:
377ºF, middle: 370ºF, back: 365ºF
Figure 18: Temperature control panel
In this study temperature settings of 150ºC and 190ºC (about 310ºF & 370ºF)
were used. These values are at the low and the high end of the suggested melt
temperature for standard polyethylene material.
Running the machine included the use of the panel. Here is a brief description of
what was used or not used and what each of these performs (left to right in figure 19).
Pump No. 1 stop – This switch turns the hydraulic pump off.
Pump No. 1 start – This switch turns the hydraulic pump on.
29
Motor #2 jog – This turned the screw and helped to make sure there was enough
material in the machine and it would clean the machine nozzle if needed.
Motor #2 (off, on) – This was used to move the plunger back to its starting
position and allowed for the refilling of thermoplastic resin into the screw
chamber.
Operation (man., semi, auto) – This was kept on manual during the testing.
Manual plunger (forward off) – This was used in this study to actuate the
hydraulics and caused the force needed to get the thermoplastic resin through the
nozzle and atomized.
Manual mold (open, off, close) – This opens the mold if in the machine, for this
study this was not used.
Heater (off, on) – This switch turns the nozzle heater on or off. The other heater
controls are on the main panel.
Figure 19: Control panel on injection molding machine.
At the bottom of Figure 19 are the controls for the hydraulic settings. The two
faucet type knobs control the hydraulic pressure to the plunger/screw and the other is the
30
hydraulics for the mold. When the machine is in operation and while the silver button is
depressed the dial will give a hydraulic pressure reading of the hydraulic line. The lever
to the far right bottom controls the movement of the injector portion of the machine. In
setting this, the nozzle was move to a predetermined location and left in that position for
the duration of the spraying of samples. Figure 20 shows the location of the nozzle. The
nozzle was placed at a distance of 1 foot from the target.
Figure 20: Spraying nozzle in location.
A nozzle holder, Figure 21, was made to hold the nozzle at the tip of the screw.
The area in red is where the nozzle was located. The darker gray part is threaded on both
end and flats were made in the center portion. The lighter gray portion was also threaded
and flats created on the tip for removing and exchanging the spray nozzle.
Figure 21: Graphic of nozzle holder
31
Figure 22: Steel nozzle holder
The following photo shows the nozzles that were available for this study. Several of
these nozzles were used; some of them were plugged up during the procedure.
Figure 23: Spray nozzles
A list of the nozzles available and their measured sizes is given below. The
nozzles were engraved with a number to maintain traceability. The nozzle openings were
measured on an optical comparator and recorded. Nozzles which were used are
32
highlighted. The openings are oval in shape and the area is calculated by using the
following equation:
(X/2)(Y/2)�=Area
Figure 24: Nozzle opening
Table 3: Nozzle opening sizes
Nozzle X dimension Y dimension Total area1 0.0122 0.0063 0.0000603662 0.0122 0.0052 0.0000498263 0.0123 0.0048 0.000046374 0.0124 0.0049 0.0000477215 0.0122 0.0049 0.0000469516 0.0122 0.0048 0.0000459937 0.0122 0.0058 0.0000555758 0.0122 0.0065 0.0000622829 0.0289 0.0102 0.0002315210 0.0245 0.0117 0.00022513411 0.015 0.0068 0.00008011112 0.0117 0.0049 0.00004502713 0.0227 0.01 0.00017828514 0.016 0.0082 0.00010304415 0.0186 0.0085 0.00012417116 0.0253 0.0102 0.0002026817 0.0124 0.0056 0.000054538
Nozzles 2, 3, 4, 11 were used in initial testing. All these plugged up and were
made useless. Nozzles 9 and 14 initially gave results, but it was later determined that the
testing was flawed and one of the nozzles had become plugged. The corrections were
made to the test and nozzles 10 and 15 were used. The results are given in the following
chapter.
Y X
33
The angles were taken to be used in the analysis but were ruled out since there
were only two nozzles used in the study. The nozzle was viewed from the side on an
optical comparator as shown in the following diagram. ‘A’ refers to the depth of the
nozzle opening and ‘B’ refers to half the distance across the ‘V’ slot. With this
dimensions the angle of the nozzle was calculated using the formula:
Tan-1(B/A)*2 = nozzle angle.
Figure 25: Nozzle Angle
Table 4: Nozzle angle
Nozzle A B Angle Angle*2 1 0.0242 0.0138 29.69º 59.39º 2 0.0256 0.01 21.34º 42.67º 3 0.0242 0.0086 19.56º 39.13º 4 0.0261 0.0104 21.73º 43.45º 5 0.0269 0.0103 20.95º 41.90º 6 0.0257 0.0098 20.87º 41.75º 7 0.0241 0.0149 31.73º 63.45º 8 0.0259 0.0155 30.90º 61.80º 9 0.0332 0.0156 25.17º 50.34º 10 0.0256 0.0164 32.64º 65.29º 11 0.0283 0.0114 21.94º 43.88º 12 0.0254 0.0103 22.07º 44.15º 13 not measurable 14 0.0422 0.014 18.35º 36.71º 15 0.0422 0.0137 17.99º 35.97º
16 not
measured
34
Several attempts were made using nozzles with smaller openings and the results
were plugged nozzles. Larger nozzle openings were then used and the plugging was
eliminated.
The material which was used is called Unipol™ DNDB-1077; this is a linear low
density polyethylene. This material was chosen for this study as a suggestion from Dow
Plastics because of its low viscosity when it is melted, as compared to other materials,
and it has good material properties. At the onset of this study, information about this
material was lacking, further testing and studies of this material have recently allowed for
more complete data to be available. This information was not found out until after this
study was performed. When this study was performed, information on standard injection
temperatures for other polyethylene plastics was followed and the range was kept with in
310-390ºF. This temperature may seem low as shown by the information given below,
but it was able to give good readings. As of recent, the processing temp was updated to
be between 380-520ºF and the following information18 is not to be construed as material
specification data sheet. The material properties listed on the following page are general
specifications.
18 http://catalog.ides.com/datasheet.aspx?I=77174&PS=ASTM&E=9871, author not given.
35
Table 5: Unipol DNDA-1107 Polyethylene, LLD
Step by step method
Once the machine was set up as previously described with the tooling and
materials, machine operation was perform in the following manner. Before each shot
was sprayed the machine was filled with the thermoplastic resin and the settings of
temperature, pressure and nozzle size were verified. Once verified a video recording of
each spray was started. The manual plunger button was depressed and the aluminum
plate, about 20” in length, was actuated to its maximum speed of about 6.4 in/sec. Each
spray only took two seconds and each panel resulted in a length between 12-15 inches.
36
Figure 26: Pulling mechanism
Figure 27: Motor controller
When the spray was completed the vertical panel was quickly removed and laid
flat to prevent sloughing of the material. The specimen was allowed to cool on a flat
surface and the aluminum sheet was prepped for the next run. The video camera was
37
stopped and all the settings on the machine and the tooling were changed to meet the
requirements of the next run. The specimen was then identified by its run order.
The specimens were cut in half and measured at one inch increments across the
width of the spray. Thickness measurements were taken of these points and these were
used in the statistical analysis. Material weight was recorded to show how fast the
material was traveling through the nozzle. Visual analysis of each specimen was also
performed and can be left to the judgment of the viewer.
The following photos show typical views of each of the 8 different possible
settings that were in this study.
Figure 28: Specimen 11, low temp., high pressure, small nozzle
Figure 29: Specimen 4, low temp., low pressure, small nozzle
Figure 30: Specimen 7, high temp., high pressure, small nozzle
Figure 31: Specimen 14, high temp., low pressure, small nozzle
38
Pilot studies
Equipment and materials used in pilot studies of this process gave an
understanding that factors of temperature, pressure, and nozzle size used in this analysis
needed to be carefully monitored and controlled.
Data collection and recording
Several photos were taken of the machine, parts and samples. Photos of the
samples were evaluated and compared with each other. A video recorder was used to
capture the results of the spray pattern and for the time it took one complete spray.
Stills were taken from the video recording to show the pattern of the spray at atomization.
Figure 33: Specimen 23, high temp., high pressure, large nozzle
Figure 32: Specimen 20, low temp., high pressure, large nozzle
Figure 34: Specimen 28, low temp., low pressure, large nozzle
Figure 35: Specimen 32, high temp., low pressure, large nozzle
39
Times were taken from the video recording and used to evaluate the data. Each spray
came to a time of 2 seconds no matter what nozzle, pressure, or temperature was used.
The samples were weighed, compared and evaluated. All other information was written
down as the samples were being prepared. Samples were visually compared and a
measurement of the thickness of the material along the cross section was performed.
Detailed information and data will be given in Chapter 4.
Statistical analysis
The statistical analysis method which was determined to be most useful was the
Split Plot Design method. This method was chosen since it allowed the factor that wasn’t
easily altered to remain in blocks or groups, while the other factors were randomized.
This factor is also termed the whole plot factor. The factor that couldn’t be altered easily
was the temperature setting and time was needed to get it to the correct setting was
needed. The constant changing of temperature could have had an effect on the material
being sprayed and could have resulted in the material to begin degrading under constant
heat. To reduce the bias that could be introduced into this study the set of experiments
was ran 4 times in random order. Table 6 shows how this is set up.
40
Table 6: Split plot design for spraying thermoplastic resin
Run Coded Factor Levels Actual Factor Levels
Spray X1 X2 X3 X4
X1 Nozzle (Size)
X2 Velocity
(Pressure)
Random Spray
Number
X3 Temp.
(Celsius)
X4 Repe-tition
Random Order
1 - - - - Small High 2 150 1 2 2 + - - - Large High 4 150 1 4 3 - + - - Small Low 1 150 1 1 4 + + - - Large Low 3 150 1 3 5 - - + - Small High 2 190 1 6 6 + - + - Large High 3 190 1 7 7 - + + - Small Low 4 190 1 8 8 + + + - Large Low 1 190 1 5 9 - - - + Small High 2 150 2 10 10 + - - + Large High 3 150 2 11 11 - + - + Small Low 1 150 2 9 12 + + - + Large Low 4 150 2 12 13 - - + + Small High 4 190 2 16 14 + - + + Large High 1 190 2 13 15 - + + + Small Low 3 190 2 15 16 + + + + Large Low 2 190 2 14 17 - - - - Small High 1 150 3 17 18 + - - - Large High 2 150 3 18 19 - + - - Small Low 4 150 3 20 20 + + - - Large Low 3 150 3 19 21 - - + - Small High 3 190 3 23 22 + - + - Large High 1 190 3 21 23 - + + - Small Low 2 190 3 22 24 + + + - Large Low 4 190 3 24 25 - - - + Small High 3 150 4 27 26 + - - + Large High 2 150 4 26 27 - + - + Small Low 4 150 4 28 28 + + - + Large Low 1 150 4 25 29 - - + + Small High 1 190 4 29 30 + - + + Large High 3 190 4 31 31 - + + + Small Low 4 190 4 32 32 + + + + Large Low 2 190 4 30
Limitations
Limitations include all the machines, equipment, and tooling discussed herein and
an effort has been made to clearly define, explain, and describe actions taken.
Temperature, pressure, and nozzles sizes were the only parts that were adjustable and all
other factors that could be set were set at a setting and not altered. The thermoplastic
41
resin was limited to Unipol™ DNDB-1077 and no other material was evaluated in this
study. A different thermoplastic resin was used in the pre-testing phase but nothing
measurable came out of it.
42
43
Chapter 4
Findings (Analysis and Evaluation) Findings
After months of working to make sense of this analysis using the split plot
method, it was determined that extra help was needed to make sense of this study. By
acquiring the help of Prof. Paul Fields, who generously gave of his time and insight, the
results were clarified and additional information was added and presented in the results of
this study.
Statistical definitions of terms
�- termed as risk, the chance of being wrong, or doesn’t follow the norm. Usually
identified as a percentage that falls outside the normal probability.
Blocking factor- the factor that is used to show blocks or groups in an analysis.
It has no real effect on the result of the outcome.
Chi-squared- a non-parametric test of statistical significance. A correctly
performed test of statistical significance lets you know the degree of confidence
you can have in accepting or rejecting a hypothesis.
Correlation- a relation between two or more variables such that changes in one
are accompanied by changes in the other.
Factors- the items in a statistical analysis which are altered for each run in the
test.
44
F-test- a test used to analyze whether random samples taken from two or more
groups have the same standard deviation. This test can be a two-tailed test or a
one-tailed test.
Interaction- a term defining the effect of two, or more, variables or factors is not
additive.
p- the value under the distribution curve that is to the right of the F values.
Regression- indicates the nature of the relationship between two (or more)
variables and can be expressed algebraically
Split plot factor- the remaining factors which levels are easy to change within the
blocks or groups.
t- is a measure of how extreme a statistical estimate is.
Variance- is a measure of how spread out a distribution is. It is computed as the
average squared deviation of each number from its mean.
Whole plot factor- the factor which has levels that are hard to change from a
setting to another.
Split plot experiment
This method was chosen since one of the factors in this study couldn’t be altered
easily and made it easier to perform this study. This method’s origin came from and is
used widely in agricultural settings where some factors, like plots of ground, are hard to
change and small plots were used instead for the hard to change factor and is termed the
whole plot factor. In this study the whole plot factor is the temperature setting. For the
other factors which are easy to change are termed as the split plot factors.
45
In this analysis there is an additional factor called the blocking factor, X4, which
allows for added repetitions in the experiment. In this experiment the factors are named
as follows:
The following charts show the set up of the experiment for the analysis. The
analysis takes thicknesses of the specimens every inch and analyzes the uniformity of the
spray pattern across the specimen. An average thickness is taken and recorded and a
variance of the thicknesses is calculated. The variance is a measure of how spread out a
distribution is. In this study there were 4 repetitions and a step was added by taking the
variance of the variance. (Table 7).
A brief description of what is shown in Table 7. A ‘1’ represents a small nozzle,
low pressure, and high temperature. A ‘-1’ represents the large nozzle, high pressure, and
low temperature
X1 Nozzle (Size)
X2 Pressure Setting
X3 Temperature
(Celsius)
X4 Repetition
46
Whole Plot Factor
Nozzle Size
Pressure Temp Reps
X1 X2 X3 X4 X1X2 X1X3 X1X4 X2X3 X2X4 X3X4 X1X2X3 X1X2X4 X1X3X4 X2X3X4 X1X2X3X4
1 -1 -1 -1 -1 1 1 1 1 1 1 -1 -1 -1 -1 1
2 1 -1 -1 -1 -1 -1 -1 1 1 1 1 1 1 -1 -1
3 -1 1 -1 -1 -1 1 1 -1 -1 1 1 1 -1 1 -1
4 1 1 -1 -1 1 -1 -1 -1 -1 1 -1 -1 1 1 1
5 -1 -1 1 -1 1 -1 1 -1 1 -1 1 -1 1 1 -1
6 1 -1 1 -1 -1 1 -1 -1 1 -1 -1 1 -1 1 1
7 -1 1 1 -1 -1 -1 1 1 -1 -1 -1 1 1 -1 1
8 1 1 1 -1 1 1 -1 1 -1 -1 1 -1 -1 -1 -1
9 -1 -1 -1 1 1 1 -1 1 -1 -1 -1 1 1 1 -1
10 1 -1 -1 1 -1 -1 1 1 -1 -1 1 -1 -1 1 1
11 -1 1 -1 1 -1 1 -1 -1 1 -1 1 -1 1 -1 1
12 1 1 -1 1 1 -1 1 -1 1 -1 -1 1 -1 -1 -1
13 -1 -1 1 1 1 -1 -1 -1 -1 1 1 1 -1 -1 1
14 1 -1 1 1 -1 1 1 -1 -1 1 -1 -1 1 -1 -1
15 -1 1 1 1 -1 -1 -1 1 1 1 -1 -1 -1 1 -1
16 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
17 -1 -1 -1 -1 1 1 1 1 1 1 -1 -1 -1 -1 1
18 1 -1 -1 -1 -1 -1 -1 1 1 1 1 1 1 -1 -1
19 -1 1 -1 -1 -1 1 1 -1 -1 1 1 1 -1 1 -1
20 1 1 -1 -1 1 -1 -1 -1 -1 1 -1 -1 1 1 1
21 -1 -1 1 -1 1 -1 1 -1 1 -1 1 -1 1 1 -1
22 1 -1 1 -1 -1 1 -1 -1 1 -1 -1 1 -1 1 1
23 -1 1 1 -1 -1 -1 1 1 -1 -1 -1 1 1 -1 1
24 1 1 1 -1 1 1 -1 1 -1 -1 1 -1 -1 -1 -1
25 -1 -1 -1 1 1 1 -1 1 -1 -1 -1 1 1 1 -1
26 1 -1 -1 1 -1 -1 1 1 -1 -1 1 -1 -1 1 1
27 -1 1 -1 1 -1 1 -1 -1 1 -1 1 -1 1 -1 1
28 1 1 -1 1 1 -1 1 -1 1 -1 -1 1 -1 -1 -1
29 -1 -1 1 1 1 -1 -1 -1 -1 1 1 1 -1 -1 1
30 1 -1 1 1 -1 1 1 -1 -1 1 -1 -1 1 -1 -1
31 -1 1 1 1 -1 -1 -1 1 1 1 -1 -1 -1 1 -1
32 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
RunInteractions Between Factors and Blocks
Split Plot Factors
Table 7: Analysis diagram split plot
47
Table 8: Specimen thickness and variance data
Response
Y1 Y2 Y3 Y4 Y5 Y6 Y7 YAve Yvar df
0.06300 0.01100 0.15900 0.07800 0.17500 0.07100 0.12500 0.09743 0.00338 6 1
0.10800 0.05400 0.06100 0.06200 0.05400 0.04000 0.08500 0.06629 0.00052 6 2
0.08000 0.10000 0.14500 0.08000 0.16100 0.07500 0.05000 0.09871 0.00161 6 3
0.09600 0.05800 0.04800 0.06000 0.04600 0.07900 0.08700 0.06771 0.00039 6 4
0.08500 0.05700 0.19300 0.09500 0.20200 0.04500 0.06200 0.10557 0.00423 6 5
0.03500 0.02800 0.12500 0.05500 0.12500 0.03000 0.02500 0.06043 0.00204 6 6
0.12400 0.05500 0.18200 0.10500 0.16700 0.04800 0.15300 0.11914 0.00280 6 7
0.07800 0.06800 0.08000 0.05000 0.08400 0.05700 0.08200 0.07129 0.00018 6 8
0.12500 0.07900 0.17700 0.09700 0.16400 0.07500 0.09600 0.11614 0.00165 6 9
0.11100 0.05000 0.04900 0.06200 0.05300 0.05800 0.11000 0.07043 0.00077 6 10
0.03100 0.09500 0.14500 0.10600 0.12000 0.18700 0.00100 0.09786 0.00410 6 11
0.10000 0.05500 0.04600 0.07900 0.04500 0.06000 0.10000 0.06929 0.00057 6 12
0.08800 0.05700 0.21100 0.11100 0.17500 0.05400 0.07100 0.10957 0.00373 6 13
0.08000 0.04300 0.10400 0.07600 0.06000 0.10000 0.03800 0.07157 0.00067 6 14
0.07600 0.06000 0.12700 0.10700 0.17500 0.06000 0.08500 0.09857 0.00173 6 15
0.07000 0.03500 0.12500 0.05300 0.09500 0.04900 0.05300 0.06857 0.00098 6 16
0.07500 0.08300 0.17500 0.09300 0.20000 0.05700 0.10500 0.11257 0.00289 6 17
0.09000 0.04000 0.04900 0.08700 0.05700 0.03200 0.11100 0.06657 0.00087 6 18
0.05000 0.12800 0.14000 0.11000 0.10200 0.16100 0.00100 0.09886 0.00308 6 19
0.07500 0.08300 0.17500 0.09300 0.20000 0.05700 0.10500 0.11257 0.00289 6 20
0.08300 0.06700 0.18400 0.11300 0.18200 0.06000 0.07000 0.10843 0.00289 6 21
0.05000 0.04000 0.11500 0.06000 0.15100 0.02800 0.04800 0.07029 0.00204 6 22
0.13000 0.07500 0.18500 0.10700 0.14200 0.04800 0.08500 0.11029 0.00213 6 23
0.05000 0.02500 0.09300 0.09800 0.07100 0.02100 0.08400 0.06314 0.00100 6 24
0.08500 0.07100 0.21000 0.09300 0.17100 0.06500 0.08000 0.11071 0.00318 6 25
0.08500 0.06200 0.09000 0.05600 0.06400 0.07500 0.13200 0.08057 0.00067 6 26
0.08000 0.08000 0.16200 0.13200 0.10500 0.16000 0.00100 0.10286 0.00317 6 27
0.04500 0.09100 0.07100 0.06000 0.05900 0.07900 0.06700 0.06743 0.00022 6 28
0.08000 0.04500 0.22400 0.10900 0.21600 0.04900 0.10400 0.11814 0.00544 6 29
0.02300 0.03500 0.13800 0.05500 0.14300 0.02300 0.02800 0.06357 0.00288 6 30
0.14000 0.05900 0.19300 0.10900 0.20500 0.04000 0.10500 0.12157 0.00390 6 31
0.04800 0.03000 0.10300 0.06500 0.09300 0.02100 0.05500 0.05929 0.00092 6 32
Thickness Across SpecimenRun
This study suggests the factors that had significant effects are the nozzle size and
the combination of temperature and pressure. All other factors or combination of factors
had some effect but were not significant. See the following diagram for information.
48
Table 9: Effects of factors used in this study X1 X2 X3 X4 X1X2 X1X3 X1X4 X2X3 X2X4 X3X4 X1X2X3 X1X2X4 X1X3X4 X2X3X4 X1X2X3X4
SumProd = -0.03230 -0.00820 0.00759 0.00164 0.00157 0.00004 -0.00614 -0.01238 0.00140 0.00427 0.00081 -0.00396 0.00102 -0.00158 0.00914
Effect = -0.00202 -0.00051 0.00047 0.00010 0.00010 0.00000 -0.00038 -0.00077 0.00009 0.00027 0.00005 -0.00025 0.00006 -0.00010 0.00057
HO: Effects = 0 HA: Effects � 0 � = 0.050 df E = 16
t E = -6.1478 -1.5603 1.4453 0.3130 0.2982 0.0078 -1.1682 -2.3558 0.2668 0.8129 0.1538 -0.7536 0.1945 -0.3000 1.7402
p = 0.0000 0.1382 0.1677 0.7583 0.7694 0.9939 0.2598 0.0316 0.7930 0.4282 0.8797 0.4620 0.8483 0.7680 0.1010
Significant: X X
Response rank vs. run order
The response verses run order doesn’t show any correlation. This suggests that
the response is not affected by the run order. For a complete showing
of information refer to appendix E. The more scattered the points on
the graph the less likely there is to be correlation.
0
5
10
15
20
25
30
35
0 5 10 15 20 25 30 35
Run Order
Res
ponse
Ran
k
27 34 113 23 431 817 519 61 714 118 930 105 1228 147 1615 1511 13
22 199 1824 2022 1721 2216 2318 2112 2426 286 2625 252 2732 2920 3229 3010 31
Response Rank Run Order
Response Run Order
Response 1 t = 1.196
Run Order 0.2133 1 p = 0.241
Figure 36: Response versus run order
49
Chi-squared test
No evidence against normality. This shows that the observed outcome nearly met
the expected outcome and is close enough to consider the results normal.
Table 10: Chi-square analysis
Yvar
Mean 0.00211
Standard deviation 0.00140
Observations 32
Intervals Probability Expected Observed
z � -1 0.16 5.1 7
-1 < z � 0 0.34 10.9 10
0 < z �1 0.34 10.9 10
z > 1 0.16 5.1 5
Chi-square Stat 0.8856
df 1
p-value 0.3467
Chi-square Critical 3.8415
50
Regression summary
Table 11: Regression analysis data
Regression Statistics
Multiple R 0.8781
R Squared 0.7711
Adj R Squared 0.5565
Standard Error 0.0009
Observations 32
ANOVA
df SS MS F p-Value
Regression 15 0.0000465 0.0000031 3.5933 0.0077
Residual 16 0.0000138 0.0000009
Total 31 0.0000603
Coefficients Standard Error t Stat p-Value Lower 95% Upper 95%
Intercept 0.00211 0.00016 12.8537 0.0000 0.0018 0.0025X1 -0.00101 0.00016 -6.1478 0.0000 -0.0014 -0.0007X2 -0.00026 0.00016 -1.5603 0.1382 -0.0006 0.0001X3 0.00024 0.00016 1.4453 0.1677 -0.0001 0.0006X4 0.00005 0.00016 0.3130 0.7583 -0.0003 0.0004
X1X2 0.00005 0.00016 0.2982 0.7694 -0.0003 0.0004X1X3 0.00000 0.00016 0.0078 0.9939 -0.0003 0.0003X1X4 -0.00019 0.00016 -1.1682 0.2598 -0.0005 0.0002X2X3 -0.00039 0.00016 -2.3558 0.0316 -0.0007 0.0000X2X4 0.00004 0.00016 0.2668 0.7930 -0.0003 0.0004X3X4 0.00013 0.00016 0.8129 0.4282 -0.0002 0.0005
X1X2X3 0.00003 0.00016 0.1538 0.8797 -0.0003 0.0004X1X2X4 -0.00012 0.00016 -0.7536 0.4620 -0.0005 0.0002X1X3X4 0.00003 0.00016 0.1945 0.8483 -0.0003 0.0004X2X3X4 -0.00005 0.00016 -0.3000 0.7680 -0.0004 0.0003
X1X2X3X4 0.00029 0.00016 1.7402 0.1010 -0.0001 0.0006
HO: Coefficients = 0 HA: Coefficients � 0
According to this normal probability plot all specimens fall nearly in line except
for one outlier Figure 37 on next page. This suggests that the outlier may have been
caused by a plugging of the nozzle or by some other factor that wasn’t controllable. The
factor that caused this was undeterminable.
51
Normal Probability Plot
0
10
20
30
40
50
60
70
80
90
100
0.000 0.001 0.002 0.003 0.004 0.005 0.006
Response (Yvar)Pro
bab
ility
PROBABILITY OUTPUT
Percentile Yvar
1.5625 0.0002
4.6875 0.0002
7.8125 0.0004
10.9375 0.0005
14.0625 0.0006
17.1875 0.0007
20.3125 0.0007
23.4375 0.0008
26.5625 0.0009
29.6875 0.0009
32.8125 0.0010
35.9375 0.0010
39.0625 0.0016
42.1875 0.0017
45.3125 0.0017
48.4375 0.0020
51.5625 0.0020
54.6875 0.0021
57.8125 0.0028
60.9375 0.0029
64.0625 0.0029
67.1875 0.0029
70.3125 0.0029
73.4375 0.0031
76.5625 0.0032
79.6875 0.0032
82.8125 0.0034
85.9375 0.0037
89.0625 0.0039
92.1875 0.0041
95.3125 0.0042
98.4375 0.0054
X1 = -1 X1 = 1
Mean 0.00312 0.00110
Variance 0.0000011 0.0000008
Observations 16 16
df 15 15
F 1.4097
p-value 0.2571
F Critical one-tail 2.4034
X2X3 = -1 X2X3 = 1
Mean 0.00250 0.00172
Variance 0.0000023 0.0000014
Observations 16 16
df 15 15
F 1.6957
p-value 0.1586
F Critical one-tail 2.4034
F-test
This test was used to verify whether the
samples drawn have the same standard
deviation with a specified confidence interval.
There is no evidence showing that the variances
are not equal.
Figure 37: Regression summary
Table 12: F-test analysis data
52
Friedman Test
First Second Third Fourth
Location Rank Sum Rank Sum Rank Sum Rank SumY1 35.5 37.5 28.0 25.0
Y2 20.5 16.5 21.0 22.5
Y3 42.5 43.0 47.0 51.0
Y4 30.5 35.5 38.0 33.0
Y5 44.0 37.0 44.0 41.0
Y6 18.0 26.5 14.0 22.5
Y7 33.0 28.0 32.0 29.0
Fr Stat 16.018 12.723 23.196 18.254
df 6 6 6 6
p-value 0.0137 0.0476 0.0007 0.0056
Chi-square Critical 12.5916 12.5916 12.5916 12.5916
Full Factorial
Y1 Y2 Y3 Y4 Y5 Y6 Y7
Mean = 0.079 0.060 0.134 0.085 0.127 0.065 0.075
Var = 0.0008 0.0006 0.0029 0.0005 0.0032 0.0015 0.0014
Location
Thickness by location
These numbers verify what can be seen visually. Locations 3 and 5 are
significantly different than the other locations.
Table 13: Friedman test—thickness by location
Mean Thickness by Location
0.000
0.020
0.040
0.060
0.080
0.100
0.120
0.140
0.160
Y1 Y2 Y3 Y4 Y5 Y6 Y7
Location
Thic
knes
s (in
ches
)
Figure 38: Mean thickness by location
53
Variance of Thickness by Location
0.0000
0.0005
0.0010
0.0015
0.0020
0.0025
0.0030
0.0035
Y1 Y2 Y3 Y4 Y5 Y6 Y7
Location
Var
iatio
n of
Thi
ckne
ss (i
nche
s)
Figure 39: Variance of thickness by location
Interaction plot
The interaction of Pressure and Temperature suggests that viscosity and/or flow
rate has an influence on the uniformity of thickness of the specimens. Figure 40 shows
that for the least variation in thickness of sprayed panels low pressure should be used
with low temperature and high pressure should be used with high temperature.
Lo Hi
Hi 0.0030 0.0017
Lo 0.0015 0.0020
Pressure
Tem
p
Interaction of Pressure and Temperature
0.0000
0.0005
0.0010
0.0015
0.0020
0.0025
0.0030
0.0035
Lo HiPressure
Var
iatio
n in
Thi
cknes
s (in
ches
)
Hi Temp Lo Temp
Figure 40: Interaction of pressure and temperature
54
Effect of nozzle size on average thickness
Nozzle size had an effect on the average thickness of the sprayed specimens. As
shown by the following diagram. Figure 41 shows that in any case the large nozzle
deposited a thicker sample panel than the small nozzle.
1 Big Nozzle, High pressure, Low Temp2 Small Nozzle, High pressure, Low Temp3 Big Nozzle, Low Pressure, Low Temp4 Small Nozzle, Low pressure, Low Temp5 Big Nozzle, High pressure, High Temp6 Small Nozzle, High Pressure, High Temp7 Big Nozzle, Low pressure, High Temp8 Small Nozzle, Low pressure, High Temp
Average Thickness to Settings
0.00000
0.02000
0.04000
0.06000
0.08000
0.10000
0.12000
0.14000
0 1 2 3 4 5 6 7 8 9
Specimen settings from Table 14
Thic
knes
s
Figure 41: Average thickness to factor settings
The effect of nozzle size on thickness variation, Figure 42, show that in any case
the small nozzle produced a sample panel with less thickness variation than the larger
nozzle.
Table 14: The 8 combinations of settings
55
Thickness Variance to Settings
0.00000
0.00100
0.00200
0.00300
0.00400
0.00500
0.00600
0 1 2 3 4 5 6 7 8 9
Specimens by setting from Table 14
Thic
knes
s va
rian
ce
Figure 42: Thickness variance to factor settings
Velocity of material
Velocity of the material is a main result of the nozzle size. The higher
temperature and pressure didn’t have as great effect other than the material wasn’t melted
sufficiently it didn’t spray. The pressure setting was limited from 1800 psi to 2000 psi.
Any setting lower than 1800 psi would produce a stream and wouldn’t atomize. The
velocity is calculated by taking the quantity of the material in ounces divided by the
nozzle area, time and density of the material. It is understandable that not all the material
made it to the target some was left as overspray. The weight of the sample is slightly
less than the weight that went through the nozzle. The calculations are below the actual
theoretical velocity.
The calculations show that the highest value is 888 mph and the lowest is 645
mph. Data can be viewed in Appendix C. Averages for each setting are listed below.
Higher pressure, higher temperature, and smaller nozzle size give the faster readings.
56
small nozzle high pressure high temp big nozzle high pressure high temp856 809
small nozzle high pressure low temp big nozzle high pressure low temp849 766
small nozzle low pressure high temp big nozzle low pressure high temp838 766
small nozzle low pressure low temp big nozzle low pressure low temp795 697
Figure 43: Average velocity in mph per settings
Visual appearance of the specimens The visual appearance of the specimens didn’t depend upon the average thickness
across them. Infact, visual appearance of the specimens did not depend upon any set of
factors. Some visually good and bad ones came from the big nozzle low pressure and
low temperature and some visually good and bad ones came from the small nozzle high
pressure and high temperature. The following information gives the breakdown by visual
uniformity. One is best, on down to four being worst. The only factor correlation that
could be shown from the visual inspection was that the more material that was sprayed
the poorer the appearance became.
Visual (1-4) Factors1,1,2,3 Blank1,1,3,3 x12,3,3,3 x21,1,3,3 x1x22,3,3,3 x31,3,3,3 x1x32,3,3,3 x2x31,2,4,4 x1x2x3
Weight vs. Visual
20
30
40
50
60
70
80
90
100
110
0 1 2 3 4 5
Visual
Wei
ght (g
)
Figure 44: Visual comparison vs. weight
57
Chapter summary
The set up and analyzation of this study used the method of a split plot design.
This method was used since temperature was a factor which was hard to control. This
statistical analysis had four repetitions to reduce variance. The factors in the spraying of
thermoplastic resin were temperature, pressure, and nozzle size. Of these, it was found
that the nozzle size had the greatest effect on the thickness uniformity of the specimens.
The small nozzles resulted in one third the thickness variation of the larger nozzles. The
other two factors of pressure and temperature were found to have a correlation. They
gave the least variation when their settings were both at the low settings or both at the
high settings in this study.
Several tests were performed to verify that this study was set up correctly and that
no other outside influences caused significant errors. Besides the one outlier, everything
appeared to be in order and the results of this study are valid. It is possible that the one
outlier was caused by material that was blocking the nozzle.
The data was tested for response to run order and it was found that there was no
correlation based on run order. A Chi-squared test was performed to verify that the test
appeared to be normal in spread. There was no significant information which would let
one to believe otherwise and it appeared that it closely followed what was expected.
A regression analysis was performed and verified that each specimen that was ran
gave results that were expected, except for the outlier. The F-test verified there was no
evidence that would lead one to believe the variances were not equal.
58
Thickness by location was visually apparent and the statistical data verified it.
There were bands in the specimens were the deposited material was significantly greater
than other areas. Further testing will need to be performed to find causes of this anomaly.
A graph of average thickness to the nozzle choice showed that the smaller nozzle
gave samples that were lighter in weight. The nozzle choice also had a great effect on the
velocity of the material. Generally, the smaller the nozzle, the higher the temperature and
pressure the greater the velocity of the material through the nozzle.
Then for added information, the visual comparison to weight showed that the
more material in the specimen had a tendency to give it an unpleasing appearance.
59
Chapter 5
Summary, Conclusions, Recommendations Brief summary The need for an alternative method of producing thermoplastic resin parts quickly,
cheaply, and safely is growing. Gases and fumes produce a working hazard and a
method for producing an alternate process is needed as a safer alternative. The first part
of this study was to see if it was possible and secondly, if possible, what factors in the
study would produce a significant effect on the result of the specimens.
The Van Dorn injection molding machine was found to be suitable for this
project. This machine had a couple modifications in the form of a nozzle holder, and a
sliding panel. These modifications made it possible to get samples that were measurable.
Unipol DNB-1077 was used as the primary material used in this study. The controllable
factors in this study were the nozzle size, temperature, and pressure.
Spraying methods have been around since the late 1880’s and is mainly used in
spraying of metals. New processes and methods of spraying is increasing and
thermoplastic spraying is one of the methods that is growing and is showing promise. Of
all the methods of spraying three stand out as possible candidates. These are powder
flame spraying, wire spraying, and high velocity oxyfuel spraying; other methods listed
are not suitable for polymers due to their high operation temperatures.
60
A company called International Paint has shown significant advancements in the
spraying of a highly viscous material at extremely high pressures. Their material has the
consistency of a fibrous peanut butter. They have developed their own nozzles and
pressure systems that make it possible and has become an important product in protecting
structural integrity during fires on oil platforms and other storage devices. Paying
particular attention to this company’s methods and procedures may prove to be of benefit
in future studies of thermoplastic spraying.
The statistical analysis used in this study was a split plot design. This method of
analysis was perfect due to the temperature setting being hard to quickly alter. As a
result the temperature settings were kept in blocks and altered after every four runs. The
group of four runs is what is termed as “plot”. A repetition of 4 was utilized in this
analysis to get a better idea of what was really happening at each of the 8 different
settings. Prof. Paul Fields mentioned the set up and running of this analysis was done
perfectly and showed there was little bias introduced to this study.
Conclusions The study analyzed what effects the nozzle size, pressure setting, and temperature
had on the sprayed specimen. The thickness across each specimen was analyzed for
uniformity of thickness. The findings suggested that the nozzle size and the combination
of temperature and pressure settings had the most influence on the result. The smaller
nozzle size gave more uniform results. It is not known why the combination of high
pressure and high temperature and the combination of low temperature and low pressure
gave statistically comparable and more uniform patterns.
61
The response versus run order was found to not have an effect on the outcome.
The Chi-square test verified that the results fell closely in the expected probability. With
the exception of one outlier all samples fell close to the probability output. The F-test
verified whether the groupings or repetitions had roughly the same variances or in other
words they have the same standard deviation with the specified confidence interval.
Thickness by location showed convincing evidence that locations 3 and 5 are
significantly different than the other locations. This was influenced by all three of the
factors, but was reduced by the settings of the small nozzle, high pressure and high
temperature or small nozzle, low pressure and low temperature.
Velocity of the material was a side step in this analysis. Although the visual
appearance didn’t correspond to the velocity it was interesting to notice that the small
nozzle, high pressure and high temp gave a greater average velocity, which is intuitively
expected. The small nozzle at low pressure and low temperature setting gave better
overall results than the bigger nozzle at high pressure and high temperature and they were
virtually at the same exit velocity.
Graphing the specimen weight versus the visual evaluation showed that the
appearance was affected negatively by the greater amount of weight in the specimen.
Recommendations for further research During the course of this study several ideas came up on what could be future
studies that would progress this method to a higher level of analysis and control. These
issues include the use of a larger machine, larger quantities of materials, other types of
materials, higher pressures, higher temperatures, and other types of nozzles.
62
The use of the Van Dorn injection molding machine was sufficient to get this
study started. Although it produced measurable samples, a larger machine which can
handle higher pressures and quantities would have given much greater working
tolerances. The pressure setting was limited to the 13,600- 15,000 psi range anything
lower than this wouldn’t produce a desired result. The temperature control settings were
adequate. The distance to the target had a maximum of rough 12-14 inches. To get this
machine working took a little maintenance to correct leaking seals. In the end this
machine proved to be workable. The use of a larger machine that can feed higher
quantities of material would be desirable.
Different types of materials would be an interesting study to pursue. The use of a
low viscosity material heated within is melt index was beneficial to get an understanding
how this could work and to get a basic understanding of the effects of different factors
and settings. It is encouraged that other materials at slightly higher melt indexes be used
and for interesting outcomes.
As mentioned earlier the pressure setting was limited to hydraulic setting of 1800-
2000psi. A desire to have higher pressure settings was greatly needed and a small
tolerance range to work with kept If this was possible, the results could have produced
other outcomes that were not seen or achieved in this study.
Higher temperatures would also be interesting to follow up on. In this study the
material specification sheet was not complete at the beginning of this study. As a result
the general melt index for polyethylene was used. After a couple years it was found that
the specification sheet had been completed with updated information that would have
63
been useful on the onset. It is proposed that the use of this material be extended and
analyzed at higher temperatures as shown in the material data sheet.
The types of nozzles that work best are standard spray paint nozzles as shown
earlier in this study. An incentive to using new types of nozzles is the ones used in this
study are being phased out and are becoming harder to get and more expensive to buy.
The use of new nozzles which are quick exchange and reversible can greatly decrease the
down time associated with tool changes. Reversible nozzles can be quickly turned if they
become plugged and force the plugging material out of the nozzle within seconds.
Nozzles became plugged quite easily in this study and several were made useless.
A study can be done to explore processes this application can be used. Initially, it
was thought that this would be a good method for lining tanks. But it was found that the
panels were porous and would need a considerable amount of material to get the same
effect as a roto-molded part. Considering the use of an open mold for the spraying of
panels seems to be a likely possibility that could make panels at an increased pace as
compared to current methods.
64
65
Appendix
66
67
Appendix A:
Samples of specimens
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
Appendix B:
Cross section views of each specimen
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
A
ppendix C:
Whole Plot Factor
Nozzle Size
Pressure Temp Reps Response
X1 X2 X3 X4 X1X2 X1X3 X1X4 X2X3 X2X4 X3X4 X1X2X3 X1X2X4 X1X3X4 X2X3X4 X1X2X3X4 Y1 Y2 Y3 Y4 Y5 Y6 Y7 YAve Yvar df1 -1 -1 -1 -1 1 1 1 1 1 1 -1 -1 -1 -1 1 0.06300 0.01100 0.15900 0.07800 0.17500 0.07100 0.12500 0.09743 0.00338 6 12 1 -1 -1 -1 -1 -1 -1 1 1 1 1 1 1 -1 -1 0.10800 0.05400 0.06100 0.06200 0.05400 0.04000 0.08500 0.06629 0.00052 6 23 -1 1 -1 -1 -1 1 1 -1 -1 1 1 1 -1 1 -1 0.08000 0.10000 0.14500 0.08000 0.16100 0.07500 0.05000 0.09871 0.00161 6 34 1 1 -1 -1 1 -1 -1 -1 -1 1 -1 -1 1 1 1 0.09600 0.05800 0.04800 0.06000 0.04600 0.07900 0.08700 0.06771 0.00039 6 45 -1 -1 1 -1 1 -1 1 -1 1 -1 1 -1 1 1 -1 0.08500 0.05700 0.19300 0.09500 0.20200 0.04500 0.06200 0.10557 0.00423 6 56 1 -1 1 -1 -1 1 -1 -1 1 -1 -1 1 -1 1 1 0.03500 0.02800 0.12500 0.05500 0.12500 0.03000 0.02500 0.06043 0.00204 6 67 -1 1 1 -1 -1 -1 1 1 -1 -1 -1 1 1 -1 1 0.12400 0.05500 0.18200 0.10500 0.16700 0.04800 0.15300 0.11914 0.00280 6 78 1 1 1 -1 1 1 -1 1 -1 -1 1 -1 -1 -1 -1 0.07800 0.06800 0.08000 0.05000 0.08400 0.05700 0.08200 0.07129 0.00018 6 89 -1 -1 -1 1 1 1 -1 1 -1 -1 -1 1 1 1 -1 0.12500 0.07900 0.17700 0.09700 0.16400 0.07500 0.09600 0.11614 0.00165 6 910 1 -1 -1 1 -1 -1 1 1 -1 -1 1 -1 -1 1 1 0.11100 0.05000 0.04900 0.06200 0.05300 0.05800 0.11000 0.07043 0.00077 6 1011 -1 1 -1 1 -1 1 -1 -1 1 -1 1 -1 1 -1 1 0.03100 0.09500 0.14500 0.10600 0.12000 0.18700 0.00100 0.09786 0.00410 6 1112 1 1 -1 1 1 -1 1 -1 1 -1 -1 1 -1 -1 -1 0.10000 0.05500 0.04600 0.07900 0.04500 0.06000 0.10000 0.06929 0.00057 6 1213 -1 -1 1 1 1 -1 -1 -1 -1 1 1 1 -1 -1 1 0.08800 0.05700 0.21100 0.11100 0.17500 0.05400 0.07100 0.10957 0.00373 6 1314 1 -1 1 1 -1 1 1 -1 -1 1 -1 -1 1 -1 -1 0.08000 0.04300 0.10400 0.07600 0.06000 0.10000 0.03800 0.07157 0.00067 6 1415 -1 1 1 1 -1 -1 -1 1 1 1 -1 -1 -1 1 -1 0.07600 0.06000 0.12700 0.10700 0.17500 0.06000 0.08500 0.09857 0.00173 6 1516 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0.07000 0.03500 0.12500 0.05300 0.09500 0.04900 0.05300 0.06857 0.00098 6 1617 -1 -1 -1 -1 1 1 1 1 1 1 -1 -1 -1 -1 1 0.07500 0.08300 0.17500 0.09300 0.20000 0.05700 0.10500 0.11257 0.00289 6 1718 1 -1 -1 -1 -1 -1 -1 1 1 1 1 1 1 -1 -1 0.09000 0.04000 0.04900 0.08700 0.05700 0.03200 0.11100 0.06657 0.00087 6 1819 -1 1 -1 -1 -1 1 1 -1 -1 1 1 1 -1 1 -1 0.05000 0.12800 0.14000 0.11000 0.10200 0.16100 0.00100 0.09886 0.00308 6 1920 1 1 -1 -1 1 -1 -1 -1 -1 1 -1 -1 1 1 1 0.07500 0.08300 0.17500 0.09300 0.20000 0.05700 0.10500 0.11257 0.00289 6 2021 -1 -1 1 -1 1 -1 1 -1 1 -1 1 -1 1 1 -1 0.08300 0.06700 0.18400 0.11300 0.18200 0.06000 0.07000 0.10843 0.00289 6 2122 1 -1 1 -1 -1 1 -1 -1 1 -1 -1 1 -1 1 1 0.05000 0.04000 0.11500 0.06000 0.15100 0.02800 0.04800 0.07029 0.00204 6 2223 -1 1 1 -1 -1 -1 1 1 -1 -1 -1 1 1 -1 1 0.13000 0.07500 0.18500 0.10700 0.14200 0.04800 0.08500 0.11029 0.00213 6 2324 1 1 1 -1 1 1 -1 1 -1 -1 1 -1 -1 -1 -1 0.05000 0.02500 0.09300 0.09800 0.07100 0.02100 0.08400 0.06314 0.00100 6 2425 -1 -1 -1 1 1 1 -1 1 -1 -1 -1 1 1 1 -1 0.08500 0.07100 0.21000 0.09300 0.17100 0.06500 0.08000 0.11071 0.00318 6 2526 1 -1 -1 1 -1 -1 1 1 -1 -1 1 -1 -1 1 1 0.08500 0.06200 0.09000 0.05600 0.06400 0.07500 0.13200 0.08057 0.00067 6 2627 -1 1 -1 1 -1 1 -1 -1 1 -1 1 -1 1 -1 1 0.08000 0.08000 0.16200 0.13200 0.10500 0.16000 0.00100 0.10286 0.00317 6 2728 1 1 -1 1 1 -1 1 -1 1 -1 -1 1 -1 -1 -1 0.04500 0.09100 0.07100 0.06000 0.05900 0.07900 0.06700 0.06743 0.00022 6 2829 -1 -1 1 1 1 -1 -1 -1 -1 1 1 1 -1 -1 1 0.08000 0.04500 0.22400 0.10900 0.21600 0.04900 0.10400 0.11814 0.00544 6 2930 1 -1 1 1 -1 1 1 -1 -1 1 -1 -1 1 -1 -1 0.02300 0.03500 0.13800 0.05500 0.14300 0.02300 0.02800 0.06357 0.00288 6 3031 -1 1 1 1 -1 -1 -1 1 1 1 -1 -1 -1 1 -1 0.14000 0.05900 0.19300 0.10900 0.20500 0.04000 0.10500 0.12157 0.00390 6 3132 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0.04800 0.03000 0.10300 0.06500 0.09300 0.02100 0.05500 0.05929 0.00092 6 32
X1 X2 X3 X4 X1X2 X1X3 X1X4 X2X3 X2X4 X3X4 X1X2X3 X1X2X4 X1X3X4 X2X3X4 X1X2X3X4
SumProd = -0.03230 -0.00820 0.00759 0.00164 0.00157 0.00004 -0.00614 -0.01238 0.00140 0.00427 0.00081 -0.00396 0.00102 -0.00158 0.00914 S2P = 0.0000009 SP = 0.00093
Effect = -0.00202 -0.00051 0.00047 0.00010 0.00010 0.00000 -0.00038 -0.00077 0.00009 0.00027 0.00005 -0.00025 0.00006 -0.00010 0.00057 Runs = 8 Reps = 4 0.0000001 1
0.0000001 1
HO: Effects = 0 HA: Effects � 0 � = 0.050 df E = 16 n f = 32 SeE = 0.00033 0.0000011 1
0.0000031 1
t E = -6.1478 -1.5603 1.4453 0.3130 0.2982 0.0078 -1.1682 -2.3558 0.2668 0.8129 0.1538 -0.7536 0.1945 -0.3000 1.7402 0.0000009 1
0.0000000 1
p = 0.0000 0.1382 0.1677 0.7583 0.7694 0.9939 0.2598 0.0316 0.7930 0.4282 0.8797 0.4620 0.8483 0.7680 0.1010 0.0000002 1
0.0000003 1
Significant: X X 0.0000012 1
0.0000000 1
0.0000004 1
0.0000001 1
0.0000015 1
0.0000024 1
0.0000024 1
0.0000000 1
Response Variance df
Run
Spray Coating Thickness Experiment
RunInteractions Between Factors and Blocks
Split Plot Factors
Thickness Across Specimen
104
1 2 3 4 5 6 7 X1 = -1 X1 = 1 X2X3 = -1 X2X3 = 1
27 3 0.08000 0.10000 0.14500 0.08000 0.16100 0.07500 0.05000 0.00338 0.00338
4 1 0.06300 0.01100 0.15900 0.07800 0.17500 0.07100 0.12500 0.00052 0.00052
13 2 0.10800 0.05400 0.06100 0.06200 0.05400 0.04000 0.08500 0.00161 0.00161
3 4 0.09600 0.05800 0.04800 0.06000 0.04600 0.07900 0.08700 0.00039 0.00039
31 8 0.07800 0.06800 0.08000 0.05000 0.08400 0.05700 0.08200 0.00423 0.00423
17 5 0.08500 0.05700 0.19300 0.09500 0.20200 0.04500 0.06200 0.00204 0.00204
19 6 0.03500 0.02800 0.12500 0.05500 0.12500 0.03000 0.02500 0.00280 0.00280
1 7 0.12400 0.05500 0.18200 0.10500 0.16700 0.04800 0.15300 0.00018 0.00018
14 11 0.03100 0.09500 0.14500 0.10600 0.12000 0.18700 0.00100 0.00165 0.00165
8 9 0.12500 0.07900 0.17700 0.09700 0.16400 0.07500 0.09600 0.00077 0.00077
30 10 0.11100 0.05000 0.04900 0.06200 0.05300 0.05800 0.11000 0.00410 0.00410
5 12 0.10000 0.05500 0.04600 0.07900 0.04500 0.06000 0.10000 0.00057 0.00057
28 14 0.08000 0.04300 0.10400 0.07600 0.06000 0.10000 0.03800 0.00373 0.00373
7 16 0.07000 0.03500 0.12500 0.05300 0.09500 0.04900 0.05300 0.00067 0.00067
15 15 0.07600 0.06000 0.12700 0.10700 0.17500 0.06000 0.08500 0.00173 0.00173
11 13 0.08800 0.05700 0.21100 0.11100 0.17500 0.05400 0.07100 0.00098 0.00098
22 19 0.05000 0.12800 0.14000 0.11000 0.10200 0.16100 0.00100 0.00289 0.00289
9 18 0.09000 0.04000 0.04900 0.08700 0.05700 0.03200 0.11100 0.00087 0.00087
24 20 0.05700 0.10000 0.05400 0.09000 0.03500 0.09600 0.06000 0.00308 0.00308
22 17 0.07500 0.08300 0.17500 0.09300 0.20000 0.05700 0.10500 0.00289 0.00289
21 22 0.05000 0.04000 0.11500 0.06000 0.15100 0.02800 0.04800 0.00289 0.00289
16 23 0.13000 0.07500 0.18500 0.10700 0.14200 0.04800 0.08500 0.00204 0.00204
18 21 0.08300 0.06700 0.18400 0.11300 0.18200 0.06000 0.07000 0.00213 0.00213
12 24 0.05000 0.02500 0.09300 0.09800 0.07100 0.02100 0.08400 0.00100 0.00100
26 28 0.04500 0.09100 0.07100 0.06000 0.05900 0.07900 0.06700 0.00318 0.00318
6 26 0.08500 0.06200 0.09000 0.05600 0.06400 0.07500 0.13200 0.00067 0.00067
25 25 0.08500 0.07100 0.21000 0.09300 0.17100 0.06500 0.08000 0.00317 0.00317
2 27 0.08000 0.08000 0.16200 0.13200 0.10500 0.16000 0.00100 0.00022 0.00022
32 29 0.08000 0.04500 0.22400 0.10900 0.21600 0.04900 0.10400 0.00544 0.00544
20 32 0.04800 0.03000 0.10300 0.06500 0.09300 0.02100 0.05500 0.00288 0.00288
29 30 0.02300 0.03500 0.13800 0.05500 0.14300 0.02300 0.02800 0.00390 0.00390
10 31 0.14000 0.05900 0.19300 0.10900 0.20500 0.04000 0.10500 0.00092 0.00092
Response Rank Run Order
Interaction of Pressure and Temperature
Location Response by Nozzle Size
105
Response Run Order
Response 1 t = 1.196
Run Order 0.2133 1 p = 0.241
Correlation of Response Rank and Run Order
No evidence of correlation between the response and the run order.
0
5
10
15
20
25
30
35
0 5 10 15 20 25 30 35
Run Order
Res
ponse
Ran
k
Yvar
Mean 0.00211
Standard deviation 0.00140
Observations 32
Intervals Probability Expected Observed
z � -1 0.16 5.1 7
-1 < z � 0 0.34 10.9 10
0 < z �1 0.34 10.9 10
z > 1 0.16 5.1 5
Chi-square Stat 0.8856
df 1
p-value 0.3467
Chi-square Critical 3.8415
Chi-Square Test of Normality
No evidence against normality.
106
Regression Statistics
Multiple R 0.8781
R Squared 0.7711
Adj R Squared 0.5565
Standard Error 0.0009
Observations 32
ANOVA
df SS MS F p-Value
Regression 15 0.0000465 0.0000031 3.5933 0.0077
Residual 16 0.0000138 0.0000009
Total 31 0.0000603
Coefficients Standard Error t Stat p-Value Lower 95% Upper 95%
Intercept 0.00211 0.00016 12.8537 0.0000 0.0018 0.0025X1 -0.00101 0.00016 -6.1478 0.0000 -0.0014 -0.0007X2 -0.00026 0.00016 -1.5603 0.1382 -0.0006 0.0001X3 0.00024 0.00016 1.4453 0.1677 -0.0001 0.0006X4 0.00005 0.00016 0.3130 0.7583 -0.0003 0.0004
X1X2 0.00005 0.00016 0.2982 0.7694 -0.0003 0.0004X1X3 0.00000 0.00016 0.0078 0.9939 -0.0003 0.0003X1X4 -0.00019 0.00016 -1.1682 0.2598 -0.0005 0.0002X2X3 -0.00039 0.00016 -2.3558 0.0316 -0.0007 0.0000X2X4 0.00004 0.00016 0.2668 0.7930 -0.0003 0.0004X3X4 0.00013 0.00016 0.8129 0.4282 -0.0002 0.0005
X1X2X3 0.00003 0.00016 0.1538 0.8797 -0.0003 0.0004X1X2X4 -0.00012 0.00016 -0.7536 0.4620 -0.0005 0.0002X1X3X4 0.00003 0.00016 0.1945 0.8483 -0.0003 0.0004X2X3X4 -0.00005 0.00016 -0.3000 0.7680 -0.0004 0.0003
X1X2X3X4 0.00029 0.00016 1.7402 0.1010 -0.0001 0.0006
HO: Coefficients = 0 HA: Coefficients � 0
PROBABILITY OUTPUT
Percentile Yvar
1.5625 0.0002
4.6875 0.0002
7.8125 0.0004
10.9375 0.0005
14.0625 0.0006
17.1875 0.0007
20.3125 0.0007
23.4375 0.0008
26.5625 0.0009
29.6875 0.0009
32.8125 0.0010
35.9375 0.0010
39.0625 0.0016
42.1875 0.0017
45.3125 0.0017
48.4375 0.0020
51.5625 0.0020
54.6875 0.0021
57.8125 0.0028
60.9375 0.0029
64.0625 0.0029
67.1875 0.0029
70.3125 0.0029
73.4375 0.0031
76.5625 0.0032
79.6875 0.0032
82.8125 0.0034
85.9375 0.0037
89.0625 0.0039
92.1875 0.0041
95.3125 0.0042
98.4375 0.0054
Regression Summary
Normal Probability Plot
0
10
20
30
40
50
60
70
80
90
100
0.000 0.001 0.002 0.003 0.004 0.005 0.006
Response (Yvar)
Pro
bab
ility
107
X1 = -1 X1 = 1
Mean 0.00312 0.00110
Variance 0.0000011 0.0000008
Observations 16 16
df 15 15
F 1.4097
p-value 0.2571
F Critical one-tail 2.4034
X2X3 = -1 X2X3 = 1
Mean 0.00250 0.00172
Variance 0.0000023 0.0000014
Observations 16 16
df 15 15
F 1.6957
p-value 0.1586
F Critical one-tail 2.4034
F-Test Two-Sample for Variances
No evidence variances are not equal.
108
Y1 Y2 Y3 Y4 Y5 Y6 Y7 Friedman TestMean = 0.079 0.060 0.134 0.085 0.127 0.065 0.075
Var = 0.0008 0.0006 0.0029 0.0005 0.0032 0.0015 0.0014 First Second Third Fourth
Location Rank Sum Rank Sum Rank Sum Rank SumY1 35.5 37.5 28.0 25.0
Y2 20.5 16.5 21.0 22.5
Y3 42.5 43.0 47.0 51.0
Y4 30.5 35.5 38.0 33.0
Y5 44.0 37.0 44.0 41.0
Y6 18.0 26.5 14.0 22.5
Y7 33.0 28.0 32.0 29.0
Fr Stat 16.018 12.723 23.196 18.254
df 6 6 6 6
p-value 0.0137 0.0476 0.0007 0.0056
Chi-square Critical 12.5916 12.5916 12.5916 12.5916
Constant sweep time? Clogging and clearing?
Thickness by Location
Full Factorial
Location
There is strong evidence locations 3 and 5 are difference from the other locations.
Mean Thickness by Location
0.000
0.020
0.040
0.060
0.080
0.100
0.120
0.140
0.160
Y1 Y2 Y3 Y4 Y5 Y6 Y7
Variance of Thickness by Location
0.0000
0.0005
0.0010
0.0015
0.0020
0.0025
0.0030
0.0035
Y1 Y2 Y3 Y4 Y5 Y6 Y7
109
Lo Hi
Hi 0.0030 0.0017
Lo 0.0015 0.0020
Interaction Plot of Pressure and Temperature
Pressure x Temp Interaction = Flow Rate? Viscosity?
For most uniform coating, use the small nozzle with low pressure and low temperature or high pressure and high temperature.
By the equal variance t-test, there is no significant difference between low, low and high, high.
Pressure
Tem
p
Interaction of Pressure and Temperature
0.0000
0.0005
0.0010
0.0015
0.0020
0.0025
0.0030
0.0035
Lo HiPressure
Hi Temp Lo Temp
110
111
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http://www.chartek.com/specsapps/Spec/PFPMats&App.pdf, author not given.
http://www.cmit.csiro.au/innovation/2003-08/cold_spray.cfm, author not given.
http://www.gordonengland.co.uk/hvof.htm, author not given.
http://www.gordonengland.co.uk/ds.htm, author not given.
http://www.gordonengland.co.uk/aws.htm, author not given.
http://www.gordonengland.co.uk/ps.htm, author not given.
http://www.pyrogenesis.com/vpsforming.htm, author not given.
http://www.sulzermetco.com/eprise/Sulzermetco/Sites/Products/AboutThermalSpray/arcwire.html, author not given. http://www.twi.co.uk/j32k/protected/band_3/ksrdh001.html, author not given.
http://www.usace.army.mil/inet/usace-docs/eng-manuals/em1110-2-3401/c-2.pdf, author not given.