School of Science, Engineering and Technology

Department of Engineering

Drape Vacuum Thermoforming Machine

By

Alexis Arredondo, Alexia Maldonado, and James Curd

Senior Design Project Presented to the Department of Engineering

In Partial Fulfillment of the Requirements

For the Degree of

Bachelor of Science

In

MECHANICAL ENGINEERING

San Antonio, Texas

April 2021

Supervising Advisor:

Dr. Juan Ocampo ASSOCIATE PROFESSOR OF MECHANICAL ENGINEERING

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ABSTRACT

Vacuum Forming is the process of taking a flat sheet of plastic and changing it into a

contoured shape. This accomplished by putting a piece of plastic into some type of clamping

mechanism, heating the sheet up to a forming temperature, stretching the heated sheet of plastic

over the mold, sealing the heated plastic sheet on the edge of the mold base, and removing the air

from within the mold cavity. A second pressure forces the material up against the mold surface.

Is that a mouthful or what? Well, all of this is necessary to get the job done. Following this

process will allow the plastic to assume the shape of the mold surface. As one might imagine,

this is a versatile process and you can make a wide variety of parts using this manufacturing

process, but there are also some limitations as to what you can do. Pulling this heated plastic

over a mold is going to stretch the hot plastic unevenly causing thinning and weak spots in

various areas, depending on the shape of the mold and the forming technique you use. Air

trapped between the vacuum chamber and the mold is hypothesized to be one of the leading

causes of microscopic defects right behind inaccurate plastic heating.

Considering these facts and because injection molding does not have many of these

restrictions, why would anyone persist in doing vacuum forming? The simple fact is that vacuum

forming has some very big advantages over injection molding and also over other forming

processes. First, mold costs are dramatically reduced, in some cases by 90%. Second, we can

prototype small runs economically compared to other methods. And Fourth, we can get into the

vacuum forming business quite easier without the extensive capital costs. These and other

variable issues will be dealt with in a more detail manner later on. For now, we would like to

address the various methods and techniques used in the vacuum forming process.

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ACKNOWLEDGEMENTS

Through this difficult process we would like to thank the Dean of S.E.T., Winston Erevelles

for sponsoring this project and allowing us to be a part of the thermoforming team. We would also

like to thank faculty that helped during the duration of our stay here at St. Mary’s University as

well as guided us along the way with this project including Dr. Ocampo, Dr. McClung, Dr. Abbot,

Dr. Afrin, Mr. Cortina, Mr. Gutierrez, Mr. Vernon, Mrs. Jaszcz. Additional thanks for the technical

support given by the people from Helmy Plastics and the people over at Mission Metal Fabrication

for the donation of the stainless-steel sheet metal that enclosed our machine. We are so grateful

for the many people that have lent a hand in the production of this project.

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Table of Contents

1. INTRODUCTION .............................................................................................................. 1

1.1. HISTORY OF THERMOFORMING ..........................................................................................2

1.2. COMPONENTS OF THE THERMOFORMING PROCESS ...........................................................3 1.2.1. Thermoforming Plastics ......................................................................................................................... 3 1.2.2. Heating System ...................................................................................................................................... 4 1.2.3. Molds ...................................................................................................................................................... 7

2. PROBLEM STATEMENT ................................................................................................... 7

3. PROPOSED SOLUTIONS ................................................................................................... 8

4. OBJECTIVE .................................................................................................................... 10

5. DIVISION OF LABOR ...................................................................................................... 10

6. OVERVIEW OF LITERATURE SEARCH .............................................................................. 11

7. PROBLEM CONSTRAINTS, REQUIREMENTS AND SPECIFICATIONS ................................... 12

8. STANDARDS ................................................................................................................. 14

9. SUMMARY OF ENGINEERING METHOD ......................................................................... 19

9.1. ITERATIVE DESIGN SUMMARY .......................................................................................... 19

9.2. OVERVIEW OF SYSTEM ..................................................................................................... 24 9.2.1. Clamp Tray Design ................................................................................................................................ 24 9.2.2. Mold Design ......................................................................................................................................... 29 9.2.3. Heating element ................................................................................................................................... 32 9.2.4. Vacuum System .................................................................................................................................... 37 9.2.5. Moving Mechanism .............................................................................................................................. 43 9.2.6. Frame Design........................................................................................................................................ 49 9.2.7. Electrical components .......................................................................................................................... 55 9.2.8. Pricing ................................................................................................................................................... 59

10. PROTOTYPE FABRICATION AND TESTING ................................................................... 60

10.1. Clamp Tray ...................................................................................................................... 60 10.1.1. Initial fabrication process ................................................................................................................ 60 10.1.2. Clamping mechanism ...................................................................................................................... 66

10.2. Heating Components........................................................................................................ 71

10.3. Vacuum ........................................................................................................................... 74

10.4. Frame .............................................................................................................................. 77

10.5. Pneumatic Cylinders ........................................................................................................ 85 10.5.1. Clamp tray mounting pieces............................................................................................................ 85 10.5.2. Mounting cylinders to bottom frame.............................................................................................. 86 10.5.3. Mounting pneumatic cylinders to the top frame............................................................................ 89 10.5.4. Mounting guide rails ....................................................................................................................... 92

10.6. Brackets for heater .......................................................................................................... 94 10.6.1. Mounting the heater. ...................................................................................................................... 95

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10.7. Installing sheet panels ...................................................................................................... 97 10.7.1. HMI and operator sheet panel ........................................................................................................ 97 10.7.2. Side sheet panels ........................................................................................................................... 100

10.8. Electrical Components.................................................................................................... 101 10.8.1. Electrical enclosure ....................................................................................................................... 101

11. Final Design ............................................................................................................ 104

12. Conclusion .............................................................................................................. 108

12.1. Results........................................................................................................................... 108

12.2. Further Implementation ................................................................................................. 108

13. SMC Capstone Reflections ....................................................................................... 108

14. References .............................................................................................................. 109

15. Appendix ................................................................................................................ 110

15.1. Machine Frame .............................................................................................................. 110

15.2. Vacuum Camber ............................................................................................................ 111

15.3. Clamp Tray .................................................................................................................... 112

15.4. Pneumatic Cylinders ...................................................................................................... 115

15.5. Guide Rails..................................................................................................................... 117

15.6. Heater ........................................................................................................................... 119

15.7. Brackets ........................................................................................................................ 121

15.8. Sheet Panels .................................................................................................................. 122

15.9. Electrical Components.................................................................................................... 125

15.10. Pricing Chart .............................................................................................................. 128

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LIST OF FIGURES Figure 1 IR Spectrum ...................................................................................................................................................... 5 Figure 2 Drape Forming................................................................................................................................................ 12 Figure 3 Machine Design .............................................................................................................................................. 22 Figure 4 Clamp Tray ..................................................................................................................................................... 22 Figure 5 Overheating Heater ........................................................................................................................................ 22 Figure 6 Vacuum Chamber ........................................................................................................................................... 23 Figure 7 Tray for plastic in bottom position ................................................................................................................. 23 Figure 8 Tray for plastic in heating position ................................................................................................................. 24 Figure 9 Clamp tray 1st design ..................................................................................................................................... 25 Figure 10 Clamp tray 2nd design ................................................................................................................................. 26 Figure 11 Clamp tray fully assembled .......................................................................................................................... 26 Figure 12 Final Design Clamp tray ............................................................................................................................... 27 Figure 13 Final clamp tray design ................................................................................................................................ 27 Figure 14 Bottom clamp tray sketches ......................................................................................................................... 28 Figure 15 Top clamp tray sketch .................................................................................................................................. 28 Figure 16 Rubber seal ................................................................................................................................................... 28 Figure 17 Stormtrooper ................................................................................................................................................ 29 Figure 18 STMU ............................................................................................................................................................ 29 Figure 19 Rattler head .................................................................................................................................................. 30 Figure 20: Iron Man Mask (mold) ................................................................................................................................ 30 Figure 21: Gears (mold) ................................................................................................................................................ 31 Figure 22: Marianist Cross (mold) ................................................................................................................................ 31 Figure 23 Ceramic panel heaters.................................................................................................................................. 32 Figure 24 Final heating element................................................................................................................................... 33 Figure 25 First design of heating box ........................................................................................................................... 33 Figure 26 Final design of heating box .......................................................................................................................... 34 Figure 27 New mounting design .................................................................................................................................. 35 Figure 28 Vacuum Chamber sketches .......................................................................................................................... 37 Figure 29 Inside shell of vacuum chamber ................................................................................................................... 38 Figure 30 Bottom plate of vacuum chamber ............................................................................................................... 38 Figure 31 Vacuum chamber assembly ......................................................................................................................... 38 Figure 32 Pneumatic Cylinder ...................................................................................................................................... 44 Figure 33: 1/4 in General Purpose Air Regulator, 59 cfm Max. Flow .......................................................................... 46 Figure 34: Pressure Gauge, 0 to 1100 kPa, 0 to 160 psi Range, 1/8 in NPT, +/-3-2-3% Gauge Accuracy.................... 46 Figure 35: Pressure Gauge, 0 to 1100 kPa, 0 to 160 psi Range, 1/8 in NPT, +/-3-2-3% Gauge Accuracy (side) .......... 46 Figure 36: Tapped linear Motion Shaft. (McMaster Carr) ........................................................................................... 47 Figure 37: Flange Mount Linear Ball Bearing. (McMaster Car) ................................................................................... 47 Figure 38: Nitra Solenoid Valve .................................................................................................................................... 48 Figure 39: Solenoid diagram ........................................................................................................................................ 48 Figure 40: Flow Control Mufflers .................................................................................................................................. 49 Figure 41 Machine frame 1st Design ........................................................................................................................... 50 Figure 42 Frame structure 1st design........................................................................................................................... 51 Figure 43 Frame Structure 2nd design ......................................................................................................................... 51 Figure 44 Frame structure 3rd design .......................................................................................................................... 52 Figure 45 Machine frame with side paneling ............................................................................................................... 52 Figure 46 Final frame design ready for fabrication ...................................................................................................... 53 Figure 47 Final frame design with sheet panels. .......................................................................................................... 53 Figure 48: Static FEA..................................................................................................................................................... 54 Figure 49: FEA Factor of Safety .................................................................................................................................... 55

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Figure 50 KTP 700 HMI ................................................................................................................................................. 56 Figure 51: S7-1200 (1214C) PLC .................................................................................................................................. 57 Figure 52: Wire Color Codes (IEC)................................................................................................................................. 58 Figure 53: Example of Price Chart ................................................................................................................................ 60 Figure 54 Top Tray plasma cut ..................................................................................................................................... 62 Figure 55 Bottom clamp plasma cut ............................................................................................................................ 62 Figure 56 Cut out trays. ................................................................................................................................................ 63 Figure 57 Placement of bracket holes .......................................................................................................................... 63 Figure 58 Hinges for clamp tray with countersinks holes ............................................................................................ 64 Figure 59 Threaded holes for hinges ............................................................................................................................ 64 Figure 60 Hinges connecting the two trays together ................................................................................................... 65 Figure 61 Clamp tray with weather stripping to secure plastic during thermoforming process ................................. 65 Figure 62 Slits for adjustable cylinder mounting.......................................................................................................... 66 Figure 63 Hood pins for clamping ................................................................................................................................ 67 Figure 64 Holes on top clamp to hold locking nut ........................................................................................................ 67 Figure 65 Holes on bottom tray for insert .................................................................................................................... 68 Figure 66 Die tap for outside of insert.......................................................................................................................... 69 Figure 67 Insert to hold hood pin ................................................................................................................................. 69 Figure 68 Cuts for weather stripping............................................................................................................................ 70 Figure 69 New weather stripping ................................................................................................................................. 70 Figure 70 Clamp tray after screws were cut ................................................................................................................ 71 Figure 71 Shell for heating element ............................................................................................................................. 72 Figure 72 Heater shell with insulation and mounting sheet metal .............................................................................. 73 Figure 73 Heater shell with insulation and heating element ....................................................................................... 74 Figure 74 CNC program overview ................................................................................................................................ 75 Figure 75 Hollowed out images of CNC program ......................................................................................................... 75 Figure 76 CNC hollowing out aluminum block ............................................................................................................. 76 Figure 77 CNC machine drilling holes for screws ......................................................................................................... 76 Figure 78 Drill taps reference chart .............................................................................................................................. 77 Figure 79 First fabrication of machine frame............................................................................................................... 78 Figure 80 Second frame fabrication, used for testing. ................................................................................................. 79 Figure 81 Steel bars for machines frame ..................................................................................................................... 80 Figure 82 Horizontal band saw cutting members to size ............................................................................................. 80 Figure 83 Top half of our machines frame ................................................................................................................... 81 Figure 84 Magnetic clamps holding machines legs in place ........................................................................................ 81 Figure 85 Horizontal member holding legs in place ..................................................................................................... 82 Figure 86 Tacking holding all members in place .......................................................................................................... 82 Figure 87 Support beam for pneumatic cylinders ........................................................................................................ 83 Figure 88 Welding for heater supports ........................................................................................................................ 83 Figure 89 TIG welding work.......................................................................................................................................... 84 Figure 90 HMI supporting members of the frame ....................................................................................................... 84 Figure 91 Final machine frame..................................................................................................................................... 85 Figure 92 Cylinder mounting nut .................................................................................................................................. 86 Figure 93#10-32 tread tap ........................................................................................................................................... 86 Figure 94 Layout of reference strip for cylinders.......................................................................................................... 87 Figure 95 Reference strip ready to be drilled on the milling machine ......................................................................... 88 Figure 96 Using laser level to alight pneumatic cylinders ............................................................................................ 88 Figure 97 Clamped reference strip and cylinders ready for mounting ......................................................................... 89 Figure 98 Sketch up of where our cylinder mounting holes will be drilled .................................................................. 90 Figure 99 SolidWorks of holes placement for vacuum chamber .................................................................................. 90 Figure 100 Dial indicator used for prep process on all milling machine fabrication.................................................... 91 Figure 101 Holes that were drilled for mounting the top of the cylinders. .................................................................. 91 Figure 102 Mounted cylinders along with vacuum chamber and clamp tray ............................................................. 92

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Figure 103 SolidWorks sketch of guide rails mounting configuration ......................................................................... 93 Figure 104 Top sheet metal plate ready for mounting and all other components ...................................................... 93 Figure 105 Mounted guide rails for clamp tray ........................................................................................................... 94 Figure 106 Sketch of hole placement for bottom brackets .......................................................................................... 95 Figure 107 Sketch of hole placement for heater mounting brackets ........................................................................... 96 Figure 108 Holes for rivets to mount heater to brackets ............................................................................................. 96 Figure 109 Rivets used to mount heater ...................................................................................................................... 97 Figure 110 Heater mounted to machine ...................................................................................................................... 97 Figure 111 Milling machine cutting excess material for HMI slot ............................................................................... 98 Figure 112 Hole punch and prep holes ......................................................................................................................... 98 Figure 113 All holes punched out and ready for components...................................................................................... 99 Figure 114 Face sheet metal with HMI and other electrical components ................................................................... 99 Figure 115 Face sheet metal mounted to the machine ............................................................................................. 100 Figure 116 Side panels mounted to machine ............................................................................................................. 100 Figure 117 Electrical components enclosure .............................................................................................................. 101 Figure 118 Electrical enclosure................................................................................................................................... 101 Figure 119: Electrical Enclosure Mounted (Front) ...................................................................................................... 102 Figure 120: White Back panel .................................................................................................................................... 103 Figure 121 DIN rails holding electrical components................................................................................................... 103 Figure 122 Power supply mounting............................................................................................................................ 104 Figure 123 Final machine design without heat covers ............................................................................................... 105 Figure 124 Final machine design with covers ............................................................................................................ 105 Figure 125 Front view of machine .............................................................................................................................. 106 Figure 126 Left side view ............................................................................................................................................ 106 Figure 127 Right side view ......................................................................................................................................... 107 Figure 128 Back side view .......................................................................................................................................... 107

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LIST OF TABLES

Table 1 Plastics Forming Ranges .................................................................................................................................... 4 Table 2. Division of Labor ............................................................................................................................................. 10 Table 3: Heat Transfer Coefficient (k) .......................................................................................................................... 36 Table 4: Biot Number ................................................................................................................................................... 36 Table 5 Density of Plastic ............................................................................................................................................. 36 Table 6 Thermoplastic Properties table ....................................................................................................................... 37 Table 7: Heating Times ................................................................................................................................................. 37 Table 8 Pressure classifications .................................................................................................................................... 39 Table 9 Applicable number for St. Mary’s University ................................................................................................... 41 Table 10 ........................................................................................................................................................................ 42 Table 11 McMaster-Carr Specifications for pneumatic cylinders ................................................................................ 44

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1. INTRODUCTION Thermoforming is a manufacturing process where a plastic or acrylic sheet is heated to

pliable forming temperature. Thermoforming has benefited from applications of engineering

technology, although the basic forming process is very similar to what was invented many years

ago. Microprocessor and computer controls on more modern thermoforming machinery allows for

greatly increased process control and repeatability of same-job setups from one production run

with the ability to save oven heater and process timing settings between jobs. The ability to place

formed sheets into an inline trim station for more precise trim registration has been improved due

to the common use of electric servo motors for chain indexing versus air cylinders, gear racks, and

clutches on older machines. Quartz and radiant-panel oven heaters generally provide more precise

and thorough sheet heating over older Cal-rod type heaters, and better allow for zoning of ovens

into areas of adjustable heat once heated, it is formed to specific shape in a mold, and trimmed to

create a usable product. The plastic or acrylic sheet is also referred to as “film” in some industries.

The sheet or film can range from a thickness of .04” to 0.50” depending on the ability of the

company forming the product. Temperature varies in material types in an oven like heater in order

to permit it to be stretched into or onto a mold and then cooled to a finished shape. There is a range

of different methods in thermoforming and molding in this industry. Thermoforming processes

include injection molding, blow molding, rotational molding, Drape Vacuum Forming, etc. There

are dozens of thermoforming processes available in the industry. Certain thermoforming processes

will develop and mold a specific product easier to create a smoother and slick mold. For Example,

thick-gauge thermoforming is usually a process designed to form vehicle door and dash panels,

utility beds, or even plastic pallets.

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1.1. HISTORY OF THERMOFORMING

The earliest form of thermoforming is tracked as far back as the early Egyptians who

discovered that Keratin, a chemical in tortoise shells, could be heated and be formable. The

material was flexible enough to be formed and then draped over piece(mold) and cooled to produce

containers to hold food. Native Americans were able to discover that cellulose, a component of

tree bark, could be formed in the same way. However, the process gained greater popularity around

World War II with the development of thermoplastics. Aircraft canopies, turrets, and relief maps

were some products masses produced during the war and after it ended the process branched away

from military applications and became much more commercially based. By the 1950's production

levels were already high and equipment was being manufactured that continued to improve cycle

time and repeatability. In the 1960's thermoforming branched into the packing industry (especially

single serving foods) and the sign and appliance industries. By the 1970's high-speed machines

were now being demanded by industry. Machines were being produced that could make 100,000

thermoformed parts per hour. At these high rates the amounts of scrap plastic that was being

produced was extreme and methods were developed for recycling or reusing the leftover product.

Since the machines were operating at much higher speeds the process controls needed to be

improved and electronic and computer controls emerged onto the scene. In the 1980's, machines

had started with simple plastic resin pellets and formed them into sheets where were then fed into

the thermoforming machine. A phrase emerged during these times and was soon to be called

"pellet-to-product". In the 1990's, the world economy slowed thermoforming machine purchasing

and environmental concerns then shook the industry. Much of the fast-food industry stopped

serving take-out food in thermoformed packages and numerous smaller companies were forced to

close. However, in the past decade the industry has rebounded, and technological advances have

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been made. More computerizations have become common. The introduction of more precise

control and higher quality products was born in this era. However, this has reduced the number of

thermoforming “blue-collar" manufacturing jobs since computers can now automate much of the

process. We, as a generation, will continue to pioneer the thermoforming industry to improve the

overall process and efficiency of thermoforming products.

1.2. COMPONENTS OF THE THERMOFORMING PROCESS

1.2.1. Thermoforming Plastics

Thermoforming can exist because of the development of polymeric materials. Plastic

polymers are manufactured from low molecular weight monomers molecules that are obtained

after distillation from crude oil, coal, and natural gas. These monomers then undergo a chemical

process (addition and condensation reactions) with catalysts, high temperature, and pressure and

form into thermoplastics which are long chain, high molecular weight molecules. Thermosets,

once the resin has cured, cannot be reshaped, and are generally not used for thermoforming.

Plastics can be reformed into new shapes when heated and are the primary material used for

thermoforming. The plastic needs to be fed into the thermoforming machines and this is done in

two distinct fashions. These are either continuous sheets which are rolled around a spool or

precut panels, both available in numerous combinations of thicknesses and width. Three basic

methods are used for forming and they are calendaring, casting, and extruding. All involve the

addition of heat to the plastic resin and then reforming it into the desired shape. The most

common is extrusion where plastic pellets are converted into a melt flow and forced through a

die system and then cooled and cut into sheets or wound around a spool. Depending on the

application for which a part is being manufactured, specific material properties will be desired

and thus the thermoplastic sheet selection process will be unique since each polymer exhibits

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different mechanical properties. During the sheet manufacturing process, additives can be

blended into the mix that can change color and modify material properties. Pigments can be

added to create solid colors, or tints can be added to create a colored translucent effect both

having minimal effects on material properties. Patterns can be printed on for decorative purposes

and the automotive industry is now painting their rocker panel thermoforming stock before

forming, reducing the need to paint it after manufacturing and thus saving money. However, this

will alter material properties so the process may need to be updated to accommodate for this. For

example, for UV and chemical resistance layers of PMMA are put onto ABS, or for a flame

retardant barrier PVC. Common materials used in thermoforming applications are polypropylene

(PP), polystyrene (PS), Polyvinyl Chloride (PVC), Low Density and High-Density Polyethylene

(LDPE, HDPE), Cellulose Acetate, Polymethylmethacrylate (PMMA), Acrylonitrile-Butadiene-

Styrene (ABS), and Thermo Plastic Olefin (TPO). Each will have different forming temperatures

and different properties suited to the application. Typical forming ranges for numerous polymers

can be seen in the Table 1.

Plastics Temperature Range C

LDPE 470-630 C

HDPE 510-630 C

PS 510-630 C

PVC 530-630 C

PMMA 530-630 C

PET 605-630 C

Table 1 Plastics Forming Ranges

1.2.2. Heating System

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Heating of the plastic sheet is a critical part of thermoforming. Heat applied can come

from many different sources but must be identical for every cycle to ensure exact result every

cycle run. Up to 80% of the total energy needed for the entire thermoforming process is

consumed during the heating phase. Gas-fired convection ovens are commonly used for the

heating of extra-large panels and extra thick plastic gauge material. This process used mostly

because of its cost-effective solution for parts and products with extra-long heating cycle times.

Gas is less expensive than electricity. Although the control with gas is not as great as with

electric heating methods, temperature control is not as critical for these extremely large parts.

Radiant heating uses infrared light wavelengths to heat the surface of the material. The heat is

dispersed equally throughout the body of the polymer by conduction. If the material is

transparent some radiation may pass through the material. The IR spectrum ranges from 700nm

2500nm as listed in Figure 1.

Figure 1 IR Spectrum

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Some of the newest and most cost-effective radiant heaters are catalytic infrared heaters.

Gas and air are fed into an enclosed chamber that is raised to a pre-elevated temperature via

small tubing. In the chambers is a catalyst, typically platinum shavings, which triggers oxidation

of the gas without burning. This generates infrared heat that heats the sheet. These platinum

shavings emit longer wavelengths and should only be used for applications where a uniform

temperature is desired. Infrared radiation heaters are commonly in the electric form. Many of the

Infrared Heater’s cores are made of a high resistance wire (nickel-chrome alloy wire). When

electricity is run through this wire, the resistance makes it glow red hot. Many varieties of this

wire exist including tubular or rod heaters. Many of the coiled wires are enclosed in a steel tube

jacket. The jacket is filled with an insulating material. The heat from the wire makes the entire

tube extremely hot which will make the acrylic or plastic sheets formable and flexible. Infrared

Heaters come in many shapes, sizes, and wattages. Voltages are relatively more or less around

the same. The Infrared Heater can be arranged in numerous patterns and designs to provide

various heating arrays.

Ceramic Heaters are a very common heater used in the industry due to the many ways of

heating. They are more expensive than the tubular type, but the benefit of greater temperature

controllability outweighs the cost disadvantage. Safety is a main priority in our cause to action in

this project. Ceramic plates are made with coiled heating element wires. These coiled wires will

glow extremely red due to its temperature capability. When the current is passed through these

wires the entire heater system will emit radiant energy. Computers and systems will make the

desired output easier to control.

Quartz Heaters have become more common of the years and decades because if its

capability to produce high frequency. Quartz is manufactured and built in a tubular shape and the

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nickel-chrome wire is threaded all the way to its core. The ends of this tubes are fitted and

adjusted with porcelain caps with leads. Quartz specifically does not interfere with the infrared

wavelengths coming from the heater. The heater can be turned on and off between cycles which

instantly saves small amounts of energy every cycle that is run. A great amount of money and

energy savings will result from using these heaters.

1.2.3. Molds A mold is needed during the Thermoforming process. The mold is used to be formed to

into a designed object. A mold is usually lightweight, easily machined and has thermal

conductivity. The acrylic or plastic sheet is then covered around the mold once heated to its

correct temperature. The formed plastic over the mold can be easily removed. Plastic shrinkage

should be a consideration while thermoforming and designing the mold size. Advanced molds

for commercial and very critical products include internal tubing and are cooled actively at the

ending of the molding process. Cooling micro tubes can be inserted into mold by drilling a hole

into a mold before casting. Molds are categorized into two major groups called male and female

molds.

Female molds are molds made with a cave-like indention and an acrylic or plastic sheet is

heated to its desired temperature is forced into its cave-like indention by either a vacuum or

pressure coming from the outside or inside of the sheet.

2. PROBLEM STATEMENT The School of Science Engineering and Technology (SET) department at St. Mary’s

University needs a fully functional, safe, and new Drape Vacuum Thermoforming Machine in its

Engineering laboratory. The machine must be capable of thermoforming 12 x 12 plastic’s to at

least 3 different types of molds. The thermoforming machine must be designed with a Human

Machine Interface (HMI) connected to a Programmable logic controller (PLC). Since the machine

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will be used in the St. Mary’s lab, it must be designed with respect for the safety of St. Mary’s

Students. St. Mary’s does not currently have a Thermoforming machine in its possession. The

Senior design team must design and build this machine from scratch to be used for future students

attending St. Mary’s. To have a future plastic molding process available to students, the senior

design team must consider the proper heater, plastic, vacuum, PLC, and power usage of the

machine.

3. PROPOSED SOLUTIONS Our initial plan for our solution is to break down the machine into its different

components. These components include, acrylic materials, heating, cooling, clamping safety

features, sensors, the vacuum chamber, electronics, as well as mechanical structural components.

We plan to start with selecting the three acrylic materials we want to form, learn their material

properties and better understand them. We will then select the heating and vacuum element we

would like to use as well as the design for our vacuum chamber. We decided to start with these

components as we feel they are more important. We plan to develop a full understanding of the

components we select so that we may use them to the best of their ability while maintaining a

safe workspace. Following the selection of the heater and vacuum, we hope to start the process

of designing and get a better idea of the dimensions and structure of our machine. We also aim to

select the appropriate sensor early on so that we can get a better understanding of how they will

work and how they will function along with our programs. Two members of our group will be

working with Simatic step 7 as we build to make sure all key components work to our

requirements.

We plan to have a team member fully create the entire model on SolidWorks. It will

illustrate the actual size, features, and give the Science, Engineering and Technology school an

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idea of what to expect before spending money on the machine itself. We, as a group, have

experience with the Computer aid design (CAD) software, SolidWorks. SolidWorks will allow

us to see the different stresses and heat transfer around the Thermoforming Machine. We will

also discuss the option of purchasing a frame for the machine or constructing our own very

frame. We expect to run into complications having to do with the acrylic sheets due to fact of

none of us have experience working in that industry. Acrylic Material and bend and twist in

many ways due to temperatures varying at times. We will attack these obstacles accordingly with

the correct safety measures. We have a group of contacts and fellow engineers to reference with

experience in project management, construction, and engineering production if something in

these field were to go wrong. Questions regarding certain topics of interest will be directed to

one of the group members which their response will be evaluated and then be up to us as a team

to decide on the decision. Having the entire thermoforming machine communicating as we

would like in a safe and in the correct manner is extremely important. We are aware of the

potential dangers an operator or user can experience with a malfunction due to miscoding and

improper wire placing. We will have to make sure the hardware is properly connected. We

decided on Siemens’ SIMATIC STEP 7 PLC because of it being the most widely known and

used PLC engineering software in industrial automation. This will not only help St. Mary’s help

its engineering gather knowledge on Siemen’s technology, but also the industrial automation

world. We will most likely connect the following with an ethernet cable.

For our design final design sketches please refer to Figure 7 and Figure 8 on page 19

Iterative design summary.

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4. OBJECTIVE The objective for this project is to design and fabricate a drape vacuum thermoforming

machine that can mold 12’’x 12’’ sheets of thermoplastics.

While the machine should hold 12x 12 major objective is the usage of a PLC system and

the HMI (Human Machine Interface)/GUI (Graphic User Interface) so that the machine can be

user friendly. We want to make sure every code, wire, and piece is built with security and

purpose Safety is a major priority within our group. The safety of the user will be considered in

every step of the design process to protect the user from unnecessary harm. We will be checking

each other's work weekly in order to verify the thermoforming machine is up to date, meeting

safety codes, and correcting any potential outliers. A continuing objective that will take a

considerable amount of time will be development process of the Drape Vacuum Thermoforming

machine.

5. DIVISION OF LABOR Division of labor is shown below in Table 2 where even distribution of work was ensured

for each member.

Member Task

Alexis Arredondo Vacuum Selection

Electric Designs

PLC/HMI Programming

Circuit Fabrication

Alexia Maldonado SolidWorks Modeling/Design

Cost Analysis

Structural Components Selection/Design

Prototype Fabrication

James Curd Heating Components

Pneumatic Components

Cost Analysis

Circuit Fabrication Table 2. Division of Labor

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6. OVERVIEW OF LITERATURE SEARCH Bulleting-137-Thermoforming by Aristech Acrylics [1] gives good information for

beginners wanting to work with Thermoforming machines. The document informs the reader that

there a 3 commonly used thermoformable acrylic sheets that a company uses. These sheets

include GPA (General purpose Acrylic), Acrysteel I-GP (Impact Resistant Acrylic) and I-300

(crosslinked Acrylic)

The document then goes on to describe the thermoplastic heating consequences for the

user to be aware of. This involves situations where the temperature of the thermoplastic is either

too low or too high. The low temperature causes thermoplastic stresses in the formed part. With

the hot temperature the sheet is subject to blistering. Thus, causing for more work to recorrect the

error and potential damages to the plastic.

Temperature control and methods of heating material to consider. There are 3 ways to

heat the thermoplastic which include:

• Forced Air Circulating Ovens

• Infra-Red Heating

• Strip Heating

Heating must always be controlled when thermoforming a plastic. Heat sensors are used

to determine if the thermoplastic is ready to be formed to the mold. The thermoplastic is not to

go above 380 degrees Fahrenheit due to blistering potential.

Different ways of thermoforming are a topic of discussion in the document. The one that

applies to this project is given below in Figure 2.

12

Figure 2 Drape Forming.

Drape/Vacuum Thermoforming – is familiar with to the straight vacuum method used in

the Thermoforming industry. The difference in this method is the material being used is framed

and heated. A pressure differential is then applied around all corners of the material being

thermoformed. The material being folded around the mold should remain close to the original

thickness. Below is a list of steps for Drape Vacuum Thermoforming a sheet.

Step 1. The plastic sheet is clamped in a frame and heated. Heating can be timed or

electronic sensors a can be used to measure sheet temperature or sheet sag.

Step 2. Drawn over the mold – either by pulling it over the mold and creating a seal to the

frame, or by forcing the mold into the sheet and creating a seal. The platen can be driven

pneumatically or with electric drive. In some very small machines, the plate can be manually

moved up or the clamped sheet can be manually pushed over the mold.

Step 3. Then vacuum is applied through the mold, pulling the plastic tight to the mold

surface. A fan can be used to decrease sheet cooling time.

Step 4. After the plastic sheet has cooled, the vacuum is turned off and compressed air is

sent to the mold to help free it from the plastic. The platen then moves down pulling the mold

from the formed part. The formed sheet is unclamped, removed, and a new cycle is ready to start.

7. PROBLEM CONSTRAINTS, REQUIREMENTS AND SPECIFICATIONS

13

Given this project, there are constraints that need to be reviewed and addressed for the

design and fabrication of this machine. Below is a list of constraints for the thermoforming

machine project:

• Our project that we are designing must be economical. The drape vacuum thermoforming

machine team was granted $5000 to complete the project. The team must be able to use

the money in a justifiable way when attaining a new part or product as well as design for

long time usage of the machine.

• Durable and Reliable

• When called upon for use the machine must be ready to go and not have any issues

starting. It must also be put in use for long periods of time without breaking down or

wearing out. The life span of the machine must uphold for 10 years of constant usage.

• Safe (functioning and operation).

• An emergency off switch will be implemented if an accident should occur

• Constant inspections are to be done on unit.

• Small footprint, floor standing, mobile.

• PLC controls with HMI/GUI

• The purchase of the PLC would have to made.

• Frame for polymer sheets required to be mechanically clamped.

• Adjustment for the frame will have to be made to suit the different molds.

• Temperature should be controllable to allow for differences between different materials.

• Along with the purchase of the PLC, thermocouples would need to be attained so that the

temperature can be recorded.

• Must include molds for 3 simple products.

14

• All individual process steps should have adjustable timers (i.e., dwell times for heating,

vacuum applicant, cooling)

• Adjustable timers suitable will be evaluated and either purchased or created by the team.

• Adjustable vacuum

• Different vacuums are to be researched for suitable suction of the plastics and their

molds.

We are aware of the $5000 budget given. None the less, the budget does not mean to use

every penny within SET’s budget. We will take into consideration the cost for each product and

provide a detail-oriented excel sheet containing the cost of the material, potential cost savings.

We want to make sure the quality of the product does not change as a result of improving and

refining a new piece of machinery.

8. STANDARDS

For the project to be up-to-date and safe among any user operating this machinery, we

needed to make sure to abide by any safety codes relating to electricity and heating. We pulled

all the necessary standards for this machinery from several governing agencies dealing with our

components.

• Part Number: 1910

• Part Number Title: Occupational Safety and Health Standards

• Subpart: 1310 Subpart I

• Subpart Title: Personal Protective Equipment

• Standard Number: 1910.132

• Title: General Requirements

15

• GPO Source: e-CFR

1910.132(a)

Application. protective equipment, including personal protective equipment for eyes, face, head,

and extremities, protective clothing, respiratory devices, and protective Shields and barriers,

shall be provided used, and maintained in a sanitary and reliable condition wherever it is

necessary by reason of hazards of processes or environment, chemical hazards, radiological

hazards, or mechanical irritants encountered in a manner capable of causing injury or impairment

in a function of any part of the body through absorption, inhalation, or physical contact.

1910.132(b)

Employee-owned equipment. Where employees provide their own protective equipment, the

employer shall be responsible to assure its adequacy, including proper maintenance, and

sanitation of such equipment.

1910.132(c)

Design. All personal protective equipment shall be of safe design and construction for the work

to be performed.

1310.132(d)

Hazard assessment and equipment selection.

1310.132(d)(1)

The employer shall assess the workplace to determine if hazards are present, or are likely to be

present, which necessitate the use of personal protective equipment (PPE). If such hazards are

present, or likely to be present.

Users or operators will be obeying and abiding by OSHA’s respiratory protective equipment

codes.

16

205.3 General Electrical Maintenance

Electrical equipment shall be maintained in accordance with manufacturers’ instructions or

industry consensus standards to reduce the risk associated with failure. The equipment owner

shall be responsible of all the electrical equipment’s documentation. The user will also be

responsible for applying calibration decals to equipment to indicate the test or calibration date.

The overall condition of the equipment must be tested correctly and maintained with the correct

parameters in this field.

These decals or labels will provide the user or operator immediate indication of the last

maintenance day and if the tested device was found acceptable on the date of the test.

205.4 Overcurrent Protective Devices

Overcurrent protective devices shall be maintained in accordance with the manufacturers’

instructions or industry consensus standards.

205.7 Guarding of Energized Conductors and Circuit Parts

Enclosures shall be maintained to guard against unintentional contact with exposed energized

conductors and circuit parts and other electrical hazards. Covers and doors shall be in place with

all associated fasteners and latches secured.

205.9 Clear Spaces

Access to working space and escape passages shall be kept clear and unobstructed.

205.10 Identification of Components

Identification of components, where required, and safety-related instructions if posted, shall be

secured attached and maintained in a legible condition.

205.11 Warning Signs

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Warning signs, where required, shall be visible, secured attached, and maintained in legible

condition.

205.12 Identification of Circuits

Circuit or voltage identification shall be secured fixed and maintained in updated and legible

conditions.

225.1 Fuses

Fuses shall be maintained free of breaks or cracks in fuse cases, Ferrules, and insulators.

Fuse clips shall be maintained to provide adequate contact with fuses. Fuse holders for current-

limiting fuses shall not be modified to allow the insertion of fuses that are not current limitin.

Non-current limiting fuses shall not be modified to allow their insertion into current living fuses

shall not be modified to allow their insertion into current limiting fuse holders.

Again, our main priority is the safety of the of the users or operators. Listed in the NFPA 70E

Handbook figure 3, is a risk management process table. This table is designed for the user or

operator to access the risk in a specific given moment in the process operating the machinery.

18

1. The main objective here is freedom of harm (i.e., injury or damage to health). The user or

operator analyzing and estimating the level of risk is a combination of estimating the

likelihood of the occurrence of harm and the severity of that harm as well.

2. The level of risk is evaluated to determine if it is reasonable to conclude that freedom

from harm can be achieved or if further risk treatment is required.

3. Risk Treatment is referred to as risk control.

Therefore, a breakdown of the terminology located in figure 3 is identified as

• Hazard Identification: Find, list, and characterize hazards.

• Risk Analysis: Sources, causes, and potential consequences are analyzed to determine the

following.

a. The likelihood that harm might result.

b. The potential severity of that harm.

c. Estimate the level of risk.

• Risk Evaluation: The level of risk is evaluated to determine if the objective of freedom

from harm can reasonably be met by the risk control that is in place or is further risk

control required?

• Part Number: 1910

• Part Number Title: Occupational Safety and Health Standards

• Subpart: 1910 Subpart I

• Subpart Title: Personal Protective Equipment

• Standard Number: 1910.134

• Title: Respiratory Protection

• GPO Source: e-CFR

19

1910.134(a)(1)

In the control of those occupational diseases caused by breathing air contaminated with harmful

dusts, fogs, fumes, mist, gases, smokes, sprays, or vapors, the primary objective shall be to

prevent atmospheric contamination. This will be accomplished as far as feasible by accepted

engineering control measures (for example, enclosure or confinement of the operation, general

and local ventilation, and substitution of last toxic materials). When effective engineering

controls are not feasible, or while they are being instituted, appropriate respirators shall be used

pursuant to this section.

1910.134(b)

Emergency situation means any occurrence such as, but not limited to, equipment failure,

rupture of containers, or failure of control equipment that may or does result in an uncontrolled

significant release of an airborne contaminant.

These listed codes above will be the regulated codes declared by OSHA which the users or

operators will be abiding by in order to successfully maintain and have a safe machine to run

within the engineering laboratory.

9. SUMMARY OF ENGINEERING METHOD Below is our summer of engineering method…

9.1. ITERATIVE DESIGN SUMMARY Our design approach started with research in thermoforming. We needed to fully

understand the process to start our design. We started by doing research on the different types of

thermoforming plastics. We wanted to have a better understanding of how they form and what

their requirements were. We then started to narrow it down to a few plastics that we wanted to

work with. The next step was to breakdown the machine into its different components. These

components include the clamp, heater, vacuum, body structure, and the moving mechanism. We

20

needed to do research on each one of these components to get a better understand on how they

work and the different ways these components come together.

Once we established a better understanding, we started our design process. Now that we

knew the plastics that we would be forming we started looking at the heating temperatures we

would need to bring the plastics to their forming temperatures. We started with heat transfer

calculations assuming heater outputs and calculated the time it would take the plastic to heat up.

We also calculated the energy required to heat the plastics to its forming temperature. From there

we looked at the different possible heating element that would give us what we calculated. Once

selecting a heating element, we then needed to decide how we were going to mount it. Configuring

the dimensions was not an easy task, there was a lot more to consider than just making a box for

our heater.

While the heating element was being designed, we were also working on the vacuum

chamber as well as the clamping tray. Working on these two components together was important

because they work together in the thermoforming process to from the mold. The role of the tray

was to hold the plastics in place while it is brought up to be heated and then to bring it down on

top of the vacuum chamber to create the vacuum seal. The dimensions of both these components

needed to fit together to make this important step work. It took 3 different designs to come up with

one that would fit our machine. Once the vacuum chamber was designed, we could then move on

to the vacuum pump needed to pull the air out of the vacuum chamber. We then conducted the

appropriate calculations and were able to select a pump.

Once the pump was selected, we now had the dimensions of the pump so that we could

start designing the base on the machine. That was our last step as far as the machines structure.

We now had the dimensions or the heater, vacuum chamber, the pump, and clamp tray. Our

21

customer wanted a small footprint machine so making sure we had these dimensions as accurate

as possible was important. We would now shrink down the design of the frame so that there was

enough space to support all the components. We also needed to take the height of the machine into

consideration, since we were making this a desktop machine, we needed to make sure this machine

was not too tall for safety reasons as well as the users accessibility.

On top of the machines structure and overall design we concluded that it was inoperant to

make sure that the machine could easy be dismantled in case any repairs needed to be made. The

design we came up with allows the user to access the main components of this machine as easy as

possible while still having a sturdy foundation. Machines do break and do need repairs, so we

wanted to make this as simple for the user as possible. Another thing that we needed to consider

was the fact that us students must building this machine and have very little experience in doing

so. So, when it comes to putting this machine together, we wanted to have a design that would be

built separately tested and put together once it was done. We also designed it so that for any reason

due to human error if we need to make something bigger would be able to without the need to

make any dramatic changes to the design.

The overall design process was a complicated one and resulted in a lot of redesigning. We

constantly had setbacks and at times it felt like we were backtracking rather than progressing. As

far as having a design approach we thought we had a process that would work, the initial plan, the

research, the design analysis, testing, evaluating and the development of the machine. The design

process was a huge learning experience for us and something we can take away from. See Figure

3,Figure 4,Figure 5,Figure 6.

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Figure 3 Machine Design

Figure 4 Clamp Tray

Figure 5 Overheating Heater

23

Figure 6 Vacuum Chamber

Our design sketches came out to a more compact desktop machine. This is the design we

wish to follow throughout this design process. We made the design as simple as we could while

trying to maintain all the requirements. See Figure 7,Figure 8 for final design sketch.

Figure 7 Tray for plastic in bottom position

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Figure 8 Tray for plastic in heating position

9.2. OVERVIEW OF SYSTEM

9.2.1. Clamp Tray Design

The purpose of the clamp tray is to make sure that the plastic is held in place during the

thermoforming process. It is important that the frame is designed so that the plastic does not slip

out at any time during its thermoforming cycle. The frame also has an important job and that is

to create a vacuum seal for the vacuum chamber. Without this seal the plastic will not form

correctly with the mold. It is also important to make sure that the design is not too heavy for the

user to handle. Also, it critical to select a material with a high thermal conductivity so that the

frame does not take heat away from the plastic. With this being said the frame will get hot, that is

why we will be proving gloves for the user to wear while thermoforming. While designing this

frame those parameters were carefully taken into consideration. The first design we created was

far from these parameters. The frame ended up being too thick and too heavy. This design also

involved welding, which we have little to no experience in. The only good thing that came out of

25

the design is that it would have created a vacuum seal that we were looking for. Figure 9 below

is an image of what our first design looked like. Our first designs shown in Figure 9 was 14” x

14” x 3” frame, made from solid stainless-steel members that totaled a weight of 35 lbs.

Figure 9 Clamp tray 1st design

The second design we created eliminated the need for welding. We did this by reducing

the thickness to ¼ of an inch instead of a total of three inches. With that being said it would only

require two thin sheets of metal rather than multiple pieces needing to be put together. We could

now cut out the shape of the frame. The reduction in thickness not only made it easy to fabricate

but it also reduces the weight of the overall frame drastically. We then changed the material from

stainless-steel to 6061 Aluminum alloy, a more popular metal used for thermoforming trays. The

dimensions of the tray were still 14 x 14 inches with the inside diameter being 10 x 10. I did not

like this idea after creating it because it was now taking 2 inches away from the 12 x 12in plastic.

So, the new forming area would only be 10 x 10. We did in fact reduce the weight of the tray to

approximately 6 pounds. Figure 10 below shows the second design.

26

Figure 10 Clamp tray 2nd design

The designing of the tray did not stop here, we were still not satisfied. We wanted to

make sure that we would get the greatest forming areas out of the plastic as possible while still

having enough room to clamp it securely. We finally achieved this goal by making the size of the

vacuum chamber bigger so that we could increase the inside diameter of the tray. Our final tray

design resulted in a 13” x 13” x ½" profile. The reduced weigh of the tray was now

approximately 4 pounds. To secure this tray to make sure that it would stay closed we added

toggle clamps to the bars sticking out in the front. We also decided to do with door hinges to

secure the trays together in the back. Figure 11 blow shows our third design.

Figure 11 Clamp tray fully assembled

27

Our last and final design of the clamp tray resulted in rounded edges around the tray to

minimize any sharp edges. The corners of the top and bottom of the tray would be rounded with

a .5in radius. The final design was drawn up on solid works and is ready for the fabrication

process show in Figure 12.

Figure 12 Final Design Clamp tray

After further consideration of clamp tray needed to be modified to include guide rails.

We also change the toggle clamps to hood pins. We also needed to make holes for the flange ball

bearings. See Figure 13.

Figure 13 Final clamp tray design

28

Below are the design sketches we created before finalizing our tray on solid works.

Before each SolidWorks design, we need to sketch out the part to make sure that we had the right

dimensions to fit out vacuum. See Figure 14,Figure 15,Figure 16.

Figure 14 Bottom clamp tray sketches

Figure 15 Top clamp tray sketch

Figure 16 Rubber seal

29

9.2.2. Mold Design

In the constraints there are 3 different molds we were asked to design for this

project. When looking to molds it is best not to have the height of the mold excessively

high. This is so the plastic does not stretch and cause unsightly marks or tears. A

maximum 3 to 1 ratio between height of the mold and length of the mold is usually

established. Our initial designs are below in Figure 17,Figure 18,Figure 19.

Figure 17 Stormtrooper

Figure 18 STMU

30

Figure 19 Rattler head

Although we liked the initial designs, we decided to take a different route when designing

our models. See Figure 20,Figure 21,Figure 22 for refence. These models were designed in

Solidworks but were not fabricated. Instead, we are planning on using small materials in the

engineering lab as a proof of concept.

Figure 20: Iron Man Mask (mold)

31

Figure 21: Gears (mold)

Figure 22: Marianist Cross (mold)

32

9.2.3. Heating element

There were a couple heaters we were looking at when designing this machine. The first

choice was a ceramic heater because it distributes heat the evenly and can operate with different

zones when it comes to thermoforming, the downside being the price range is on the high end.

Straight calrods were the next choice for heating our plastic, spacing each one 1.5 inches apart in

our 12’’x 12’’ array. Unfortunately, TPS LLC, the thermoforming parts company we are

communicating with were having trouble producing calrods that short and in that array. TPS

referred us back to ceramic panel heaters in an aluminum casing in a 12’’x12’’ array as shown in

Figure 23.

Figure 23 Ceramic panel heaters

The temperature range for this heater is between 750 F – 1300F and the wattage given off

is 750 W per panel. We were worried that this heater would give off too much heat in our small

area so then we decided to look for smaller elements. The element we will be using for our machine

is shown in Figure 24.

33

Figure 24 Final heating element

The heating element is 12 inches in length and 12 inches in width so this would be a

perfect match for the sizing of our heater and requires 1000W, 120v. This element is the basis for

our calculations.

To mount the heating element, we will be placing it in a 14” x 14” x 2.5” aluminum box

that’s a 1/8” thick. The element would be supported by thin thrips like done in most household

ovens. The sides of the box would have aluminum tubes on the side to connect to supporting

members. See Figure 25 for assembly.

Figure 25 First design of heating box

34

With further evaluation of our heating box, we realized that we did not have anything that

would prevent the top of the box from getting too hot. We also didn’t have any design to keep

the heat from the element in the box. So, we decided to add fiberglass insulations on the inside

with sheet metal laying over it and secured with bolts and nuts. We also decided to omit he

aluminum rod on the side of the heater to reduce the weight of the box. Instead, we will be using

brackets to connect the box to the heater supports. See Figure 26 and Figure 27.

Figure 26 Final design of heating box

35

Figure 27 New mounting design

9.2.3.1. Calculations for Heating phase: The plastic is being emersed in a hot fluid when it is sent up to our heater. The best

method for our design to find the time it takes the plastic to reach a certain temperature is the

Lumped Capacitance method because of the convectional heat transfer from the element to the

plastic.

Lumped Capacitance method:

𝐵𝑖 =ℎ𝐿𝑐

𝑘< 0.1

Where:

𝐵𝑖 = Biot Number

𝐿𝑐 = Thickness of material divided by 2

𝑘 = Heat Transfer Coefficient

36

Heat Transfer Coefficient (W/m K)

HIPS 0.16

PETG 0.29

HIPS 0.19 Table 3: Heat Transfer Coefficient (k)

Biot Number

HIPS 0.0655

PETG 0.0361

PVC 0.0551 Table 4: Biot Number

For this method to work the Biot number for all the plastics must be below 0.1. If that

condition is met, the process can continue.

Heating Time

𝑡 =𝜌𝑉𝑐

ℎ𝐴𝑠ln (

𝑇𝑖 − 𝑇∞

𝑇 − 𝑇∞)

Where:

𝜌 = density of material

𝑉 = Volume of material

𝑐 = specific heat of material

𝑇𝑖 = Initial temperature

𝑇∞= Ambient Temperature (Heating temperature)

𝑇 = Final plastic temperature

Ex: For PVC

𝑡 =𝜌𝑉𝑐

ℎ𝐴𝑠ln (

𝑇𝑖 − 𝑇∞

𝑇 − 𝑇∞)

𝑡 =1420

𝑘𝑔𝑚2 ∗ 0.001524 𝑚2 ∗ 1255

𝐽𝑘𝑔 𝐾

13.75𝑊

𝑚2 𝐾

= 86.78𝑠 = 1.45 𝑚𝑖𝑛𝑢𝑡𝑒𝑠

Density (𝑔/𝑐𝑚3)

HIPS 1.04

PETG 1.27

PVC 1.42

Table 5 Density of Plastic

Heat Capacity 𝐶𝑝(J/kg*k)

37

HIPS 1402

PETG 1470 – 1530

PVC 1050 - 1460

Table 6 Thermoplastic Properties table

Heating Times (s)

HIPS 76.6

PETG 74.19

PVC 86.78 Table 7: Heating Times

9.2.4. Vacuum System

9.2.4.1. Design of Vacuum chamber The overall design on our vacuum chamber is shown below. The final dimensions are 12”

x 12” x 1.5”. The vacuum chamber will be made from 6061 Aluminum Alloy. We will be using

the CNC machine to hollow out a 12”x12”x1.5” block to make the top chamber of the vacuum and

an aluminum sheet 14” x 14” x ¼" as the bottom of the chamber. These members will be assembled

with ¼ 20” screws with epoxy to create a seal. Below are the sketches for the chamber as well as

the top and bottom assembly pieces in Figure 28,Figure 29,Figure 30,Figure 31.

Figure 28 Vacuum Chamber sketches

38

Figure 29 Inside shell of vacuum chamber

Figure 30 Bottom plate of vacuum chamber

Figure 31 Vacuum chamber assembly

39

9.2.4.2. Vacuum Calculations In order the choose the right pump for the correct application, we need to consider a few

things in mind. Power, Pressure, Sizing, etc. are some of the factors we need to consider when

choosing the right Vacuum Pump. See Table 8 for pressure classifications.

Vacuum type Maximum Pressure

(in mbars)

Minimum Pressure

(in mbars)

Molecules per cm3

Rough Vacuum 1 10-3 1016-1013

High Vacuum 10-3 10-7 1013-109

Ultrahigh Vacuum 10-7 10-12 109-104

Table 8 Pressure classifications

Boyle's Law: Under conditions of constant temperature, Boyle's Law gives the

relationship between volume and pressure for a fixed quantity of gas.

𝑃1 ∙ 𝑉1 = 𝑃2 ∙ 𝑉2

We will mostly be dealing with Viscous Flow because of the Rough Vacuum pressure.

We do not need a tremendous amount of power and suction. While accurate equations for

aperture flow are complex in the viscous flow regime, this approximation is often reasonably

valid:

𝐶𝑣 = 130𝐴

A= Area of circular or nearly square aperture

Cv = Conductance in I/s in viscous regime

So, 130 x 0.11045 (This is the area of the 0.375in tubing connecting to the Vacuum

Chamber) = 14.358 l/s

The conductance of the tubing flow is shown below. This will be used in later equations.

40

𝑡 =𝑉

𝑆𝑡ln (

𝑃1

𝑃2)

Where:

t = time to pump from pressure P1 to P2 (sec)

V = Chamber volume, incl, turbulation (liters)

St = delivered pump speed, (liter/second)

Vacuum pumps come in a variation of sizes and suction power. A 6 CFM pump from

CPS was determined as our choice of pump from a financial standpoint. We decided it wasn’t

too expensive for a 6 CFM pump from a highly respected and durable vacuum company. The

calculation in finding out the amount of time it going to take in order to thermoform a mold till

absolute pressure is displayed below.

𝑇 =(137.5)

1.883𝑙𝑛 (

14.49 𝑃𝑆𝐼

. 0004 𝑃𝑆𝐼) = 12.29 𝑆𝑒𝑐𝑠

The thinner the material, the smaller diameter the vacuum hole – usually 1mm diameter

holes for materials up to 2mm, and 1.5mm diameter for materials above 2mm in thickness. To

minimize witness(stress) marks when working with materials below 1mm, create 0.75mm or less

diameter holes.

Since our Polymer and Acrylics sheets are around the 0.06- and 0.065-inches mark

equaling around 1.524-1.651-mm. Accordingly to industry standards the thickness of the sheets

corresponds to the diameter holes to be 1mm wide.

Area of a circle = 𝜋𝐷2

4

We will be using the diameter of the Vacuum holes and the Diameter of the Piping

Vacuum hose connected to the Vacuum pump within this equation to determine the number of

holes needed in this Vacuum Chamber

41

1𝑚𝑚 = 0.039 = 0.04in

Area of Vacuum Holes within Chamber in inches: 𝜋(0.04)2

4= 0.001257𝑖𝑛2

Area of Piping Vacuum Hose: 0.3𝑖𝑛 =𝜋(0.3)2

4= 0.11045𝑖𝑛2

Method I found prescribed in Florian’s Practical Thermoforming was then implemented to do the

calculations which expressed in the formula below.

𝑁 =𝑃

𝑈÷ 𝐷 =

𝑃𝐷

𝑈

Where:

N = Number of Vent Holes required

P = Cross Sectional Area of the Vacuum Piping Used

U = Number of individual Molds

D = Drill-Bit Cross Sectional Area

Table 9 Applicable number for St. Mary’s University

When a clamped thermoplastic sheet is heated, it will begin to sag above a certain

temperature. The maximum tensile strain is located on the bottom surface and the maximum

compressive strain is on the top surface. For a rectangular sheet sag can be calculated by the

following equation below

𝑦 =𝛽𝑞𝐿4

𝐸(𝑇)ℎ3

Florian’s Method

Piping’s Cross-Sectional Area (P) 0.11 Inches2

Number of Individual Molds Used

(U)

1

Drill-Bit Cross Sectional Area (D) 0.000767 Inches2

Number of Vent Holes (N) 14.4 = 15

42

Where:

Y = Amount of sag in inches

q = Weight of the sheet in lb./in^2

L = sheet span in inches

E(T) = temperature dependent modulus in lb. F/in^2

β = function of sheet length to width

[2]Florian, John., Practical Thermoforming, 2nd Edition, Marcel Dekker, New York (1996).

(Sheet Length) / (Sheet Width) β

1.0 0.0444

1.2 0.0616

1.4 0.0770

1.6 0.0906

1.8 0.1017

2.0 0.1110

3.0 0.1335

4.0 0.1400

5.0 0.1417

Infinity 0.1421 Table 10

When the air bubble is sealed on all sides of the mold before the Vacuum Pump is

activated, a constant control volume is formed. Constant Control Volume is the actual Volume

within the vacant space between the mold, the acrylic or polyester sheet, and the surface of the

vacuum chamber. We can use the Ideal gas law equation below to find the pressure.

𝑃𝑉 = 𝑛𝑅𝑇

Where:

P = Pressure of the gas

V = Constant Volume

N = number of moles of gas, Constant

R = Universal Gas Constant

T = Temperature of the gas

The Ideal Gas Equation can be rearranged to calculate the estimated change in pressure

from the deformation of the plastic onto the mold. We know the initial air temperature

(Assuming Room Temperature) would be

43

T1 = 30C = 303K

T2 =? = (Average heating temperature for Acrylic sheet need to be around 230C, so 503K

P1 = 14.696 psi (atmospheric pressure)

𝑇1

𝑃1=

𝑇2

𝑃2

When we rearrange the equation, we solve for P2.

𝑃2 =𝑃1𝑇2

𝑇1=

14.969(503)

303= 24.85𝑝𝑠𝑖

Thus, the net pressure inside the volume is calculated by the formula below.

𝑃𝑁𝑒𝑡 𝐼𝑛𝑠𝑖𝑑𝑒 𝐵𝑢𝑏𝑏𝑙𝑒 = 𝑃2 − 𝑃𝑎𝑡𝑚 = 24.85𝑝𝑠𝑖 − 14.696𝑝𝑠𝑖 = 10.154𝑝𝑠𝑖

It is then calculated that the Acrylic Sheet will have around 10.154psi of force against the surface

when placed over the mold.

9.2.5. Moving Mechanism

9.2.5.1. Pneumatic Cylinders

When looking for mechanisms that lift heavy objects with little force, hydraulic or

pneumatic cylinders are usually a first choice. The difference between the two is that the

hydraulic cylinders use oil as a fluid and pneumatic cylinder use compressed air to push a piston

like rod through an enclosure to exert various pressures required to lift heavy objects. Similar

examples would be a hydraulic jack used to lift a car or a pneumatic door stopper.

For our lifting system only one pneumatic cylinder was required to lift the weight of the

clamping frame, but two cylinders were used to distribute the weight evenly. See Figure 32 and

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Table 11 McMaster-Carr Specifications for pneumatic cylinders for the pneumatic cylinder

reference.

Figure 32 Pneumatic Cylinder

McMaster-Carr Specifications

Bore Size 9/16”

OD 0.62”

Stroke 12”

Retracted 15.25”

Extended 27.25

Body Material 304 Stainless Steel

Rod Material 303 Stainless Steel

Rod Diameter 0.19”

End Type Threaded

Thread Size 10-32

Air inlet Size 10-32

Air inlet Thread Type UNF, Female

Maximum Cycles 7,920,000

Maximum Pressure 250 psi

Force @ 50 psi 13 lbs.

Force @ 100psi 25 lbs.

Force @ 150 psi 37.5 lbs.

Force @ 200 psi 50 lbs.

Pivot Pin diameter 0.16”

Temperature Range -20F to 200F

Table 11 McMaster-Carr Specifications for pneumatic cylinders

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9.2.5.2. Pneumatic Cylinder Calculations

Since the clamp frame is only 5 lbs. the pressure needed to lift the frame with two

pneumatic cylinders needed to be calculated. Using Pascal’s law, the pressure required to lift the

clamp can be found.

𝐹 = 𝑃𝐴

Where:

F = Load in lbs.

P = Pressure required

A = Area of pneumatic cylinder Bore

Before solving this equation, the area of the bore needs to be found. The diameter of the

bore for the pneumatic cylinder is 9/16”, and the formula for area of a circle is 𝐴𝐶𝑖𝑟𝑐𝑙𝑒 = 𝜋

4𝐷2.

For this specific application area of the pneumatic cylinder bore is:

𝐴𝑏𝑜𝑟𝑒 = 𝜋

4(

9

16𝑖𝑛𝑐ℎ)

2

= 0.2485 𝑖𝑛2

Going back to Pascal’s Law, the pressure required to lift 5lbs can now be found now that

area is calculated.

𝑃 =𝐹

𝐴=

5𝑙𝑏𝑠

0.2485𝑖𝑛2= 20.12 𝑝𝑠𝑖

This answer would be if there were only one pneumatic cylinder lifting a load but, in our

case, we have two cylinders lifting the clamp. Simply put, the pressure calculated must be

divided by 2 to get the pressure needed for each pneumatic cylinder.

𝑃𝑟𝑒𝑞 =20.12𝑝𝑠𝑖

2= 10.06 𝑝𝑠𝑖

To set the air pressure to 20 psi and air regulator and pressure gauge were added into the

system. If needed in the future, the air regulator can be set to different pressures for heavier

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loads. See Figure 33: 1/4 in General Purpose Air Regulator, 59 cfm Max. FlowFigure 33, Figure

34,Figure 35 below for air regulating components.

Figure 33: 1/4 in General Purpose Air Regulator, 59 cfm Max. Flow

Figure 34: Pressure Gauge, 0 to 1100 kPa, 0 to 160 psi Range, 1/8 in NPT, +/-3-2-3% Gauge Accuracy

Figure 35: Pressure Gauge, 0 to 1100 kPa, 0 to 160 psi Range, 1/8 in NPT, +/-3-2-3% Gauge Accuracy (side)

47

On their own, the pneumatic cylinders caused some instability, so the implement of guide

rods and ball bearings were put in place to erase the discrepancies. See Figure 36, and Figure 37

for guide rails and the ball bearing flange used to support the clamp tray.

Figure 36: Tapped linear Motion Shaft. (McMaster Carr)

Figure 37: Flange Mount Linear Ball Bearing. (McMaster Car)

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9.2.5.3. Solenoid Valves

The valve used on this machine will be a 5 port(4way), 2-position solenoid valve spring

return see Figure 38. This is a pneumatic directional control valve. The directional control valve

directs the flow of air in 2 different directions and is used with a double acting cylinder. Inside

the valve there is a spring that is electromagnetically charged when turned on, the output power

on the PLC will do this for us. This spring moves the small spool inside the valve, the movement

of the spool allows for airflow within the valve in different directions. The 2 positions let air

movement into and out of the double acting cylinder. There are 5 ports on the valve for this to

happen, 1 inlet port to the valve, 2 ports that allow air movement into and out of the pneumatic

cylinders and 2 exhaust ports. The port sizes for this valve were ¼” NPT and the airline size was

1/8”OD; 1/16 ID.

Figure 38: Nitra Solenoid Valve

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Figure 39: Solenoid diagram

To control the airflow through the solenoid valve, flow control mufflers were inserted

into the exhaust ports of the valve. Flow control mufflers are adjustable but do not have a

discrete value to show exactly the amount of airflow entering and exiting. See Figure 40.

Figure 40: Flow Control Mufflers

9.2.6. Frame Design

For the overall design of the frame our goal was to keep the machine relatively light so that

it could be moved around the lab with ease. We wanted a solid structure that would support each

component. We also did not want the base of the structure to be too tall considering it would be

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placed onto a desk. The base of our machine was going to be made from steel bars with sheet metal

panels on the sides. We wanted to make this design simple but sturdy. We came up with the idea

to have the steel members creating the supportive structure while the metal panels on the outside

hid the components that were going to be inside. We decided that we were going to use hollow

beams so we would be able to achieve the lightweight design. The idea was to have these members

cut and welded together. The panels on the outside would be bolted to the steel structure. We

decided to bolt them as opposed to welding them so if the user for any reason needed to access the

pump inside or need to repair a part, they would be able to take the side panel off to do so. Our

first design was very basic and did not include a space for the PLC controls. In Figure 41 is an

image of our first design. It was too big and needed to be reduced.

Figure 41 Machine frame 1st Design

Our second design we focused more on the steel structure to make it more secure and

added a spot for the PLC. We moved forward with this second design once the other main

components were finalized. We were able to shrink down the overall size. Like mentioned before

we wanted to design to be compact so that it would fit on a desk and be easy for the user to reach

and operate. In Figure 42 is the second design we came to.

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Figure 42 Frame structure 1st design

After further evaluation we were still not satisfied with this design. The top of the frame

did not have enough support for the rest of the components. The heater needed to have a more

solid structure to bolt into, so we decide to add beams that went across from the back of the

frame to the front. The extra support beams are shown in Figure 43.

Figure 43 Frame Structure 2nd design

With careful evaluation of this third design, we still were not satisfied. We were now

coming to the final design of our moving mechanics and needed to have a solid structure to

support those members. For our final design we then added two more members from the outside

members to the added center ones. See Figure 44 for final frame design.

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Figure 44 Frame structure 3rd design

Once the frame structure was finalized, we then proceeded to redesign and configure the

side paneling to finish out the design. We now had a solid structure and a space for the PLC

controls. We kept enough space inside this frame for our vacuum chamber along with the wires

and PLC and HMI components. The side panels are 1/8 in thick and the top panel is ¼ in thick.

The final frame design is show in Figure 45.

Figure 45 Machine frame with side paneling

During the fabrication process we decided to make a change to the frames design. We cut

back material under the face of the HMI. The reason we decided to go with this new decides is to

provide for a better weight distribution as well as a reduction in the material used. This would

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also provide extra support for the HMI and other electrical components. We also added two

supports on the bottom of the frame to add support for the vacuum pump. See Figure 46 for final

frame design.

Figure 46 Final frame design ready for fabrication

The changes that were made to the steel frame also had to be made to the sheet metal

panel on the outside. See Figure 47 for the final design of the frame with sheet metal on the

sides.

Figure 47 Final frame design with sheet panels.

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9.2.6.1. Finite element analysis

Although the frame would not be subjected to relatively heavy loads, we did a FEA in

Solidworks to show that the frame would not collapse and had a high factor of safety from the

loads we are required to put on it. The frame is made from A36 steel and the loads applied are

7.5lbs on each of the 3.5-inch bars to replicate the 4 steel bars and the heater box. The FEA also

consisted of 10 lbs on each of the two bars carrying the weight of the vacuum chamber as well as

15 pounds on each of the bars on the bottom to show the wight of the vacuum. See Figures

Figure 48: Static FEA and Figure 49.

Figure 48: Static FEA

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Figure 49: FEA Factor of Safety

The yield stress for A36 steel is 36, 260 psi but the highest stress given by the loads is

only 217.3 psi which is nowhere near yielding for this material. This also gives us a factor of

safety of 166.

9.2.7. Electrical components

9.2.7.1. HMI/PLC

The implementation of a human machine interface (HMI) and a programmable logic

controller were constraints from the beginning of this project. An HMI allows for a user to

interact with a piece of machinery often controlled by a PLC. There are many different HMIs

and PLC’s out on the market, but some of the biggest companies are Siemens, Allen-Bradly,

Schneider electric, and ABB. When deciding on which software and hardware to choose from,

we looked towards the technical knowledge of Mr. Gutierrez who has experience with

automation controls. It was decided that a Siemens HMI and PLC were to be used with this

thermoforming machine. A PLC and HMI are completely optional when dealing with machinery.

The Thermoforming process is all mechanical and can be done manual. A PLC and HMI were

implemented into this industry machine in order to have the user or operator see as many factors

56

as possible and variables when dealing with the industrial machine is on. These addition features

are not only a “techy” feature, but also make the machine more user-friendly.

The goal of any HMI screen is to develop “situation awareness”, or the ability to identify

the process and comprehend the critical elements of a situation. In the case of trying to increase

awareness, and also control a process through a schematic-style screen, the design of that screen

is going to be a major factor. This is all done with taking into consideration the voltage from the

HMI to the PLC.

The goal of the PLC is automating the processes that are manual. This includes the

powering and regulation of the vacuum pump, heater, relays, coils, air trays, and everything else

power by electricity insider the machine. The PLC works as the brain. The PLC will give power

to the individual systems when needed and programmable to show pressure gauge, pressures,

and other features.

See Figure 51, Figure 51.

Figure 50 KTP 700 HMI

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Figure 51: S7-1200 (1214C) PLC

9.2.7.2. Wiring Wiring a one of the most important features of this project. We decided to go with 16-

gauge wire throughout the entire thermoforming due to the fact of 16-gauge wire being able to

withstand the resistance, amperage, and frequency. We are dealing with 120V and 24V power

sources. For the machinery to work properly and conveniently; we had to convert the 120V AC

power coming from the wall to 24V DC power. The conversion of this is done accordingly with

a Crouzet power supply bank. The outlet will have a WHITE, GREEN, and BLACK cord with is

120V connecting to the Crouzet power supply bank and the output cords will be WHITE and

BLACK. Identifying which wires are energized with what power is extremely important and

detrimental to the user or operator's safety when working inside the electrical box.

We have fully separated signal wires, 24VDC wires, and 120VAC wires. This will make

it easier for the operator or user to be able to distinguish any major power sources. We needed to

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abide by the national wire codes for not only thermocouples, but also analog wires. Listed below

is the industry standard for thermocouples.

Figure 52: Wire Color Codes (IEC)

A Prosense Type K Thermocouple is being used for this project. The Thermocouple is made of

316 Stainless steel with a Temperature sensing range of 0-927-Degrees Celsius. The insulation

running from the thermocouple is Magnesium oxide (MgO). We were able to distinguish the

positive and negative cables in the thermocouple using the thermocouple codes issued within the

United States of America.

Electric Schematic Diagram of System

59

9.2.8. Pricing With the $5000 budget in mind, a pricing chart in excel was created with subsections

containing different major components to keep track of the materials we were purchasing. See

Figure 53: Example of Price Chart and appendix section 13.10.

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Figure 53: Example of Price Chart

10. PROTOTYPE FABRICATION AND TESTING

Below in this section we will be discussing the fabrication and testing process in detail

also with pictures and results. A lot of changes were made to the design throughout the process.

10.1. Clamp Tray

10.1.1. Initial fabrication process The fabrication of the clamp tray started with finalizing SolidWorks design. We would be using

the plasma cutting machine in the lab to cut out the tray from sheets of 6061 Aluminum. We

ordered two sheets of Aluminum ¼” thick, one sheet was 13” x 18” and the other 15” x 21.5”. For

us to use the Plasma machine you need to follow a few set up steps and convert the SolidWorks

file into a (.tap) Mach 3 file. The three steps to do this process involve three programs, V-carve

Pro, SheetCam, and lastly Mach 3. Since I already had my part drawn on SolidWorks, we did not

need to open V-Carve Pro. The first step was to convert the SolidWorks file to a DXF file so that

it could be opened in SheetCam. Once we opened SheetCam we were able to import the DXF file

and set up the operations parameters. This was done in the “Create a New Jet Cutting Operation”,

61

tab. We needed to select the correct tool and create a desired tool path. Setting the tool path was

critical. We either needed to offset the tool on the inside or the outside of out cutting path in order

to preserve the material and not cut into the area we needed. These toolpaths were set to each layer

that was created in SolidWorks. After this was completed, we then needed to generate a G-Code

for the drawing so that I would be converted into a (.tap) file and be recognized by Mach 3. For

the final step we could now open the Mach 3 program which connects directly to the machine. To

set this machine up we needed to make sure to “reference all axis” so that the machine would know

where it is located. Once the machine was ready, we then needed to move the tip to it desired zero

location for the cut. We also needed to set the tip .5 inches above the material and then zero all the

axes. Once all the axes are set, we then loaded our G-Code into the program under the “cycle start”

button and ran a simulation to make sure the part would be cut out correctly. Once the simulations

looked correct and ran smoothly, we then began our cut.

The cutting process started with the top clamp tray which unfortunately was not completely

cut out. The laser made the cut through the top surface and halfway through in other areas on the

material. We were not sure why this happened. For the next cut we decided to make a change the

speed of the laser from 40in/min to 35in/min for the bottom tray. There was an improvement in

the cut of this pieces. In most areas the laser went all the way through, but in some it did not. See

Figure 54 and Figure 55 below.

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Figure 54 Top Tray plasma cut

Figure 55 Bottom clamp plasma cut

To get the tray completely cut out of the sheet we decided to use a jigsaw. To use the

jigsaw, we first needed to sand down all the slag so that the blade would have a clear path to cut

on. This would also prevent the blade from snapping. This was done using a sanding disk. Next

to get the jigsaw in the groove of the cut we first needed to make a clear-cutting gap for the

blade. Once the path was ready to cut, we placed a piece of tape to create a visual line to follow,

then proceeded to cut out the rest of the tray. The cut-out trays are shown in Figure 56.

63

Figure 56 Cut out trays.

To join the top and bottom pieces together we used galvanized steel door hinges that

were two inches long and an inch and a half in debt. We first needed to prepare the holes were

the bracket and screws would line up on both trays so that they would fit together uniformly. We

measured an inch from each side of the tray and marked the ends to show where the brackets

would be placed. Next, we needed to mark where the holes needed to be drilled. We did this

with a center punch. see Figure 57.

Figure 57 Placement of bracket holes

Once the holes placements were made, we followed over each hole with a 1/16” drill bit

to set up a guide hole for the 26 bit. We then followed over the holes with a countersink so that

64

the screw would sit flush with the things. The holes on the hinges needed to be adjusted with the

counter sink as well. See Figure 58.

Figure 58 Hinges for clamp tray with countersinks holes

Once the holes were drilled in the trays, we followed through with a tap wrench using the

vertical milling machine as well as a thandel. See Figure 59. Once the holes were tapped were

attached the hinges to the trays. See Figure 60.

Figure 59 Threaded holes for hinges

65

Figure 60 Hinges connecting the two trays together

Next, we needed to add the weather stripping which would hold the plastic in place

between the two trays and create the seal at the bottom of the tray. We used Premium rubber

self-stick weather seal. We cut the stripping to the correct length on each with a 45-degree cut so

that the corners would fit other at a 90-degree angle. We stuck the stripping to the top of the

bottom tray at the inner edge. The stripping was also applied to bottom side of the bottom tray in

the middle. See Figure 61

Figure 61 Clamp tray with weather stripping to secure plastic during thermoforming process

66

To prepare the tray to be mounted to the cylinder we needed to drill a slit on each side of

the tray’s arms. We used the vertical milling machine to do this. The reason we drilled slits in the

arms rather than holes was because the arms were not perfectly lined up with on another due to

the cuts of the plasma machine. The slits would allow for us to adjust the position of the tray to

the vacuum and connect to the cylinders. See Figure 62.

Figure 62 Slits for adjustable cylinder mounting

10.1.2. Clamping mechanism For our clamping mechanism we originally wanted to use toggle clamps. After

purchasing and receiving them we realized we did not consider the spaces needed to open the

clamps, therefor they would not work with our design. so, we decided to change to hood pins see

Figure 63.

67

Figure 63 Hood pins for clamping

To mount the hood pins to the tray we needed to prep and drill the correct sizes first. We

started by marking where we wanted the pins to be placed on both the top and bottom trays. To

drill the holes, we used the milling machine. The first holes were made on the top half of the tray

starting with a center punch followed by a ¾ in drill bit. see Figure 64.

Figure 64 Holes on top clamp to hold locking nut

For the bottom half of the tray, we started with a center punch ¼ in drill bit. Once the

holes were drilled, we place the hood pins on the tray and clamped the tray closed. We realized

that there was too much space in between the two trays and needed to be adjusted. To do this we

needed to move the pin down, but to do so the hole needed to be treaded. Since we had already

68

drilled the holes, we now needed to make an insert. To make the holes for the inserts we needed

to start by making the hole bigger. To do this we used a 29/64 in bit followed by a ½ 20 tap. See

Figure 65 below.

Figure 65 Holes on bottom tray for insert

To fabricate the insert, we started with a ½ diameter aluminum rod. For this fabrication

process we used the lathe. We first needed to make a hole on the inside of the rod using a #9 drill

bit that would later be threaded with a M6x1 tap. This hole would hold the pin in the clamping

mechanics. Once the hole was made, we proceeded to the outside of the rod. The outside needed

to be threaded with a ½ 20 tap. The taping tool that was used was a die tap. See Figure 66 for die

tap. See Figure 67 for the rod.

69

Figure 66 Die tap for outside of insert

Figure 67 Insert to hold hood pin

Now that we have the center hole threaded, we can screw the insert into the bottom of the

clamp tray. To hold the insert in place we will be adding a nut on the bottom. See fig___

(add pic of insert in tray)

Now that everything is in place, we can assemble the hood pin to the clamp tray. See

fig__ for final assembly of clamping mechanism. ( add picture of clamped tray)

70

After some testing was done, we realized that the tray was not sitting flush with the

vacuum tray therefore the proper seal was not being created. We also assumed there was gaps in

the weather stripping where we had cut it and connected them in the corners. So, we decided to

remove all the weather stripping and redo them. We did this by cutting triangle into the strips and

then bending them together to create a 90-degree angle. See Figure 68 and Figure 69.

Figure 68 Cuts for weather stripping

Figure 69 New weather stripping

71

Once we placed the clamp tray back in place on the machine and clamped a piece of

plastic and realized that the back left half of the tray was not sitting flush with the vacuum

chamber allowing air to seep through. We the realized that the screws holding the hinges to the

top and bottom tray was keeping the assembly from sitting flush. We decided to remove the nuts

and grind the ends of the screws off flush with the surface of the tray with an air grinder

followed by a belt sander. See Figure 71.

Figure 70 Clamp tray after screws were cut

With the new weather stripping and the screw cut down to size we could proceed to the

final step and polish the clamp tray. We polished the tray with an air sanding disk. Please see the

figure ___ below for the final clamped tray.

(insert image of final clamp tray)

10.2. Heating Components

This fabrication process for the heating component started with the purchase of our heating

box shell. This box was made of 6061 Aluminum Alloy with the dimensions 14” x14” x 2.5” and

a thickness of 1/8”. The required thickness of aluminum that we needed was too thick for the metal

bending machine in the lab, so we were not able to fabricate this box on our own. We need the

help of M&M metals who had the material we needed as well as the machines to do so. This

72

company was located here in San Antonio which made this fabrication process fast and affordable.

The shell was fabricated by starting with a 19” x 19” x 1/8” sheet of Aluminum. 2 ½” x 2 ½”

squares were then cut out of each corner of the sheet so that the sheet could be bent into a box.

Once the sheet was bent into the shell the edges of the box where the cut sides met were welded

together to that there were no cracks or sharp edges. See Figure 71 below.

Figure 71 Shell for heating element

The next step for this box was to install the insulation and the heating element. We

purchased a fiberglass insulation blanket from Lynn that is 1/2in thick and was cut to a 14” x 14”

sheet using the shears on the metal bending machine in the lab. The insulation was then placed in

the bottom of the box. Next, with the sheet metal we had purchased from Home Depot we cut a

12” x 12” sheet using the same shears and placed it on top of the insulation blanket. On the inside

of the shell, we made 5 holes where the screws, washers, and bolts would go to secure the

insulation blanket and sheet metal. To make the holes we first needed to make sure they lined up

with the holes in the sheet metal, so we used a center punch to make indentions were the holes

needed to be drilled. We then followed over those holes to make them big enough for the next step

73

using a hammer and a chisel punch. After the indentions were made, we then used a vertical mill

to drill ¼ holes over the punches. Finally, we used a ¼ twist drill bit to smooth the edges of the

holes on each side. After the shell was ready for the insulation and sheet metal, we place them

back into their correct places and poked holes through the insulation in places of the 5 holes. The

screws were fed through both materials and though the shell with a washer and bolt to fasten the

other side. See Figure 72.

Figure 72 Heater shell with insulation and mounting sheet metal

The second to last step in the Heating box was to install the heating element. To do this we

need to drill two ½” holes into the side of the shell an inch from the insulation with two inches in-

between the holes. Two indentions were made using the same technique as before with the center

punches. Next to drill the holes we need to make sure they were exactly ½” in diameter. To do so

we used a hand drill with a step bit. This bit was labeled with several different diameters that

allowed you to make a hole of your desire with accuracy. Once the holes were made, we fed the

74

ends of the heating element through the holes and fasted the washers and bolts to the end. The full

assemble is show in Figure 73.

Figure 73 Heater shell with insulation and heating element

The final step was to install the thermal couple which will be controlling the heat of the

element…

10.3. Vacuum

The final design of the vacuum chamber consisted of an Aluminum block and a thin

aluminum plate screwed together with ¼-20 screws. The Block is made of 6061 Aluminum Alloy

with the dimensions of 12” x 12” x 1.5”. Both pieces were purchased from Westbrook metals here

in San Antonio. The dimensions of the plate are 14” x 14” x 1/8”, also made of 6061 Aluminum

Alloy. To make the inside of the chamber the block needs to be hollowed out. To do this we will

be using the CNC machine in the engineering lab at St. Mary’s. The first step in this process was

to finalizes the design on SolidWorks and convert the program into a dfx. file so that it can be

programmed to the machine. Mr. Vernon selected the appropriate bit size to hollow out the

Aluminum block. This process needed to be done in 5 layers, once the first layer is done the bit

75

will then push down creating the second layer until the 5th layer is done shown in fig Figure 74.

See Figure 75 for hollowed out image.

Figure 74 CNC program overview

Figure 75 Hollowed out images of CNC program

To create the holes for the screws we used the size 7 bit that we found using a Starrett tap

drill size chart. Shown in Figure 78. The size 7 drill bit fits the tap size of the ¼- 20 machine screw.

To move on with the machine process the machine needs to be cleaned and prepped. Since the

machine had been sitting there for a year without being cleaned due to COVID-19 the coolant and

oil had mixed and spilled in the bottom cartage creating a mess. There was also metal shaving that

need to be scrapped out of the bottom of the pan. The coolant needed to be properly disposed of

which we did not have the ability to do ourselves. A work order was put in to have it cleaned but

76

was declined three weeks later. This did set us back in our fabrications process as this part was one

of the main components of our machine. Thankfully, our shop professor Mr. Weir owns a machine

shop here in San Antonio and was able to machine the block of aluminum for us. See Figure 76

and Figure 77 for the CNC process.

Figure 76 CNC hollowing out aluminum block

Figure 77 CNC machine drilling holes for screws

77

Figure 78 Drill taps reference chart

10.4. Frame The fabrication of our machines frame was a critical one. We needed to make sure all the

dimensions were accurate. The most crucial part of the machines dimensions was the height of the

frame to correctly secure out pneumatic cylinders inside the machine. Our first machine frame

would be made from wood while our final machine frame would be made of steel. The reason we

wanted to start with wood is so that we could assemble the entire machine and make minor

adjustment to it as needed. With our experience in building, we know that human error happens in

any fabrication process. Going from design on paper to the actual product there is going to be

problems and changes that need to be made. Using wood would allow us to make these minor

adjustments without a lot of hassle. As we build, we would be able to disassemble and cut each

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member as needed verse us having a metal frame welded from the start. It’s a much easier and

cheaper way of ensuring our design is correct and applicable.

With that, our first design fell short an inch in height. The reason it was too short was

because we tried to get a head start on our project and build the height of the frame on solid works

without the correct dimensions of the cylinders. We did learn from this mistake and not only

corrected the height, but we were also able to make a different adjustment to the machine frame

that would not only save us space but would require less material resulting in us saving money.

Our first machine frame design is shown below in Figure 79. Unfortunately, with this fabrication

we were not able to adjust because it was too short and adding wood for height was not reasonable

or reliable.

Figure 79 First fabrication of machine frame

The second fabrication of the frame was taken at a different approach. Instead of using long

screws to secure one member to another we decided to make homemade brackets out of wood and

used shorter screws. This allowed us to rotate and cut the members without having to worry about

previous holes being in the way and having to work around them. This did require a little more

work but would better benefit us in the long run. Not only did using these brackets save us hole

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places and more room for cutting but it also provided us with a more secure frame that was level.

The finish product was symmetrical on all sizes and the frame did not wobble and was very sturdy.

This frame included the structural adjustment as well as the correct height for the cylinders. Below

in Figure 80 is the frame we will start our assembly on as well as test all our components.

Figure 80 Second frame fabrication, used for testing.

Once we made sure that everything would fit inside the frame, we proceeded to build our

steel frame. We started with five 6-foot-long rods. See Figure 81. We used the horizonal band

saw in the machine shop to cut the member to the correct size. The band saw was not level due to

a wheel that was broken so we leveled it using scrap aluminum and clipboards. Before cutting

our members, we needed to cut off ¼” from the started ended of the beam so that the first piece

would be square and clean. Then we proceeded to cut. See Figure 82.

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Figure 81 Steel bars for machines frame

Figure 82 Horizontal band saw cutting members to size

Once the members were cut, we then need to prepare the metal for welding. We did this

by sanding all the edged where the cuts had been made. We also need to wipe all the grease off

each ended where the members would be welded so that it would not affect the weld itself. The

welding process was an overwhelming task considering we did not know how to and had to learn

on the spot. The welding technique we started with was Tig welding. The first section that

needed to be welded was the top half of the frame. We started by clamping these members down

to the table and made sure that they were square and exactly where we needed them to be. Then

we began to weld. See Figure 83 for the top half of the frame.

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Figure 83 Top half of our machines frame

Next it was added the four legs of the machine. It was extremely critical that they were

square and level with the rest of the frame so that the frame would not wobble. We did this using

square magnets and a square level along with a mallet to move the members. See Figure 84.

Figure 84 Magnetic clamps holding machines legs in place

Once two of the legs had been welded on, we began adding the bottom members that

would be supporting the machines internal components. The reason we added this member

before all the legs were done was to make sure they the legs would stay straight as we are

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welding. The welding technique that we used for this step of the machine was called tacking.

Tacking is used to hold members in place without having to make a complete weld. When

welding members they tend to move and pull in the direction of the weld. So, this method was

used to prevent that as well as the help of the horizontal member shown in See Figure 85.

Figure 85 Horizontal member holding legs in place

We then proceeded to add the rest of the legs and supporting members using the tacking

method. See Figure 86.

Figure 86 Tacking holding all members in place

The next step was to add the supporting member on the bottom for the pneumatic

cylinders. It was very critical that this member was level with the outside members so that the

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sheet metal would sit flush inside the machine. We also had to make sure that the member was

the correct distance from the back of the machine and in the center of where the vacuum

chamber will sit so that that clamp tray would directly on top of it. See Figure 87.

Figure 87 Support beam for pneumatic cylinders

At this point of the welding process, we changed to MIG welding which was a much

faster process. This was also a learning experience considering we had never used this method

before. We were able to get more done in half the time. This technique would be used for the rest

of the machine and to complete the welds over the tacked areas. See Figure 88 and Figure 89 for

some of our welding work.

Figure 88 Welding for heater supports

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Figure 89 TIG welding work

Next, we proceeded to add the angle pieces of the frame that would hold the HMI and

controls and two support beams on the bottom for the vacuum pump. The HMI supporting

members consisted of two pieces cut to 8in with two 45-degree angles on each end. See Figure

90.

Figure 90 HMI supporting members of the frame

The final part of the welding process was to add the support members for the heater. This

was critical because they need to be lined up exactly with the members to the heater which

would allow it to sit directly over the vacuum chamber. this would then line the heating element

to sit perfectly even over the plastic for uniform heating. Once those members were added for the

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final step needed to grind the welds down on the top of the machine so that the sheet metal

would sit flush with the frame. Our final machine frame is show in Figure 91 below.

Figure 91 Final machine frame

10.5. Pneumatic Cylinders

10.5.1. Clamp tray mounting pieces

To move our tray up and down we will be using two pneumatic cylinders. To connect the

cylinders, we will be making a cylinder mounting nut. This consists of a two 2in cylindrical steel

rod with #10-32 thread size all the way through. To start this process, we would first cut the rod

into 2in length. Next, we will be using the lathe in the shop to machine the next few steps. We first

needed to make sure that the ends of the rods were perfectly straight. To do this we use a cutting

tool. Ones the ends were straight we then needed to drill a hole all the way through the cylinders.

To set the hole so that the drill bit would go through we needed to use a center drill. Once the holes

were set, we were able to drill the holes using the correct bit found on the chart seen in Figure 78

Drill taps reference chart. After the hole is drilled, we then needed drill the #10-30 treads all the

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way through shown in Error! Reference source not found.. Drilling these threads would allow

use to screw the cylinders into the bottom and a fastening screw through the top. See Figure 92

and Figure 93 for cylinder mounting nut.

Figure 92 Cylinder mounting nut

Figure 93#10-32 tread tap

The cylinder mounting nuts were available on McMaster-Carr where we purchased the

cylinders, however they were more expensive than we would like them to be, so we decided to

fabricate them on our own. This would also allow us to make any size we want while testing out

machine versus having to buy a new one ever time.

10.5.2. Mounting cylinders to bottom frame

The fabrication and placement of the cylinders was the hardest and most critical part of

the fabrication process. Due to the cylinders being flimsy we need to make sure that they were

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perfectly level and in the correct spot so that when connected to the clamp tray it would sit

directly over the vacuum chamber creating an airtight seal.

The first step in this process was mounting the bottom of the cylinders directly under the

holes of the tray. This was very hard since the holes on the tray had not evenly paced us from the

midpoint of the tray due to the cuts from the plasma cutter. So, we started by measuring the

distance between the holes of the tray and from the holes to the edges of the machine. We then

decided to use a strip of metal that we would drill holes in and use as a guide to mount. To make

sure that we were accurate we made a sketch on solid works with the correct measurement and

spacing of the cylinders on the strip of metal. See Figure 94 once the solid works was complete,

we drilled the holes using the milling machine the lab. We used this machine because we could

use the coordinates on the screen as reference and drill the holes accurately. See Figure 95 for

milling process on our strip of metal.

Figure 94 Layout of reference strip for cylinders

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Figure 95 Reference strip ready to be drilled on the milling machine

Once our reference piece was ready, we set it inside the machine with the cylinders on

top. Thanks to another senior design group in our class, we were able to level the cylinders using

their laser level that was part of their project. See Figure 96 Once they were set to where we

wanted them, we clamped the bar to the frame and began to make the holes and screwed the

cylinder in. see Figure 97.

Figure 96 Using laser level to alight pneumatic cylinders

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Figure 97 Clamped reference strip and cylinders ready for mounting

10.5.3. Mounting pneumatic cylinders to the top frame

Now that the cylinders are secure on the bottom, we could proceed to the top sheet metal of the

frame to secure the cylinders in place. Like said before this next step was just as critical as the

one before. The holes from the top and bottom of the machine needed to be lined up so that the

cylinder was level. We created a diagram, in SolidWorks. Were the holes for the cylinders would

be places, see Figure 98. We also needed to drill the holes where the vacuum would sit as well as

the holes for securing the plate to the frame. See Figure 99.

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Figure 98 Sketch up of where our cylinder mounting holes will be drilled

Figure 99 SolidWorks of holes placement for vacuum chamber

For the top plate we also used the milling machine in the lab and used the same technique

as before with the reference coordinates. Instead, this time we need to zero out the axis making

sure that the X and Y started it the top left corner. It was also very crucial that the plate was level

with the bit all the way down the table. We both referenced and leveled the plate using a dial

indicator and a ____show in Figure 100 below. Once the plate was clamped and ready to go, we

processed with drilling the holes show in Figure 101.

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Figure 100 Dial indicator used for prep process on all milling machine fabrication

Figure 101 Holes that were drilled for mounting the top of the cylinders.

Once the holes were drilled, we then placed the sheet, vacuum, clamp tray, and cylinders

in place on top of the frame to make sure everything was lined up. See Figure 102. This process

was a success, and we were able to secure the plate to the frame.

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Figure 102 Mounted cylinders along with vacuum chamber and clamp tray

10.5.4. Mounting guide rails

After the cylinders we secure in place we decided test them and realized that the

cylinders did not go off at the same time and were very unstable. Making minor adjustments to

the pressure and speed of the solenoids did not help so we decide that we needed to add guide

rails. This added another critical process to our fabrication. We purchased two guide rails and

two flange ball bearings. We now needed to make another hole in the tray for the guide rails

along with two more holes in the top sheet. We also needed to make a strip to support the rails at

the top so that the rails would be level and secure. We repeated the same process as before with

the top and bottom sheet. We started with the SolidWorks drawing shown in the Figure 103.

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Figure 103 SolidWorks sketch of guide rails mounting configuration

The easiest way to approach this and make sure the holes were lined up was to secure the

tray, and top sheet together and drill them at the same time. We started with a center drill then

followed over each hole with a ¼ in drill bit for the screws. Once the screw holes were drilled,

we followed back over the tray hole with a ½ bit for the guide and bearing to fit through. Once

the holes were ready, we placed the sheet back on top of the machine. See Figure 104.

Figure 104 Top sheet metal plate ready for mounting and all other components

Next, it was time to add the guide rails, clamp tray and vacuum together. We secured the

rails by feeding a screw through the bottom of the top sheet with a locking washer as well as a

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regular one. Once the bottom was secure, we screwed the bearings to the tray and placed the tray

on the guide rails. Then we placed the strip on the top with the same two washers See Figure

105.

Figure 105 Mounted guide rails for clamp tray

We then tested the cylinders again to see if our new design would fix our problem. The

guide rails worked, and we had our first successful test.

10.6. Brackets for heater

The brackets for the heater needed to be hand mad due to us not being able to find the

correct size that we needed. We needed to measure to make sure that the distance between the

heater and the mounting rails left enough space for our heat shields. We also needed to make sure

that the heater would be mounted directly about the vacuum chamber so that all the components

lighted up. These brackets would be made out 20-gauge steel sheets cut down to size using the

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shears in the lab. We cut 8 brackets to 1 ½in x 5in. This gave us enough room to bend them at a

90-degree agnel so that they would separate the heater 3in heater to supports on each side. To make

the hole where the screws would go, we lined up the brackets we purchased on top of the ones we

just made. Using a center punched we marked the holes on each side of the brackets. Once the

holes were marked, we used an 1/8 in bit on the drill press to drill the holes. We followed over

each hole with a counter sink to eliminate any sharp edges. Then we fed the bracket thought the

metal bending press at 2in. The brackets were now finished.

10.6.1. Mounting the heater.

To mount heater, we needed to cut some support beams out of the remaining material that

we had. They needed to be 17 ½ in long so that it would give us enough room for the brackets and

to ensure that the heater would be an inch away from the max height of the clamp tray. Four

members were cut to these exact measurements and wiped down to remove all the grease. Next,

we needed to predrill the holes where the brackets would be places. We drew a sketch so that our

holes would be as accurate as possible and make it easier to use the milling machine. See Figure

106 and Figure 107 below for our sketch.

Figure 106 Sketch of hole placement for bottom brackets

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Figure 107 Sketch of hole placement for heater mounting brackets

We drilled the holes again by using the X and Y coordinates on the milling machine with

an 1/8 drill bit. we set the bar flush with the end of the vise grip on the milling tables and set the 0

axis and proceeded to drill. Once all the holes were drilled into the steel bars, we then drilled the

brackets into the top and bottom. To connect the top brackets to the heater we decided to use

Aluminum rivets with a 1/8in diameter and 1/4 in grip range. We placed the bars with the top

bracket against the heater and clamped them together. Then, drilled a 1/8 in hole and fed the rivets

through. See Figure 108 and Figure 109.

Figure 108 Holes for rivets to mount heater to brackets

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Figure 109 Rivets used to mount heater

Once the brackets were secured to the heater we predrilled and drilled the holes in the top

sheet and mounted the heater to the machine. See Figure 110.

Figure 110 Heater mounted to machine

10.7. Installing sheet panels

10.7.1. HMI and operator sheet panel

To start this panel, we needed to draw out and mark the areas where the HMI, two power

buttons, key turn, and emergency buttons would sit. Once the holes were market, we would first

start with cutting out he hole for the HMI. Since stainless steel is hard to cut, we need to make a

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clear path for the milling machine to follow. we did this by using air die grinder with slitting saw.

We followed over the outline of where the HMI would sit. Once the path was made, we took the

sheet over the milling machine and used a 4-flute carbide milling cutter to cut the excess material

off so that the HMI would fit nice and snug. See Figure 111.

Figure 111 Milling machine cutting excess material for HMI slot

After the HMI space was cut out, we change to a 1/4 in drill bit and prepared to cut the

holes out for the rest of the components. Once the holes were cut, we used a 7/8 in hole punch to

cut the holes to the correct size. See Figure 112 for holes punch and ¼ in prep hole. See Figure

113 for the complete hole punching process.

Figure 112 Hole punch and prep holes

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Figure 113 All holes punched out and ready for components

After all the holes and HMI space was cut out, we assembled the components into the

sheet to see how everything would fit. See Figure 114 for full assembly.

Figure 114 Face sheet metal with HMI and other electrical components

Once the components were secured and fit, we put the sheet back on the milling machine

and drilled six ¼ in holes, three on each side ¾ in away from the edge. For the top screws on the

left and right side we placed a washer through each screw to elevate the top half of the sheet so

that it would sit flush with the side panels. The rest of the four holes just received screw by

themselves. See Figure 115.

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Figure 115 Face sheet metal mounted to the machine

10.7.2. Side sheet panels

The two side sheet panels need to be predrilled with the milling machine to make holes

for the mounting screws. We used a 1/8 drill bit and spaced theme evenly with 3 holes on the top

and bottom and back side. each hole was offset ¾ in from the edge so that the screw would

fasten in the middle of the 1.5in steel frame. See Figure 116.

Figure 116 Side panels mounted to machine

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10.8. Electrical Components

10.8.1. Electrical enclosure

The enclosure for the electrical components is a 16”x 16” x 6” indoor enclosure with

a hinge cover and knockouts. This enclosure houses the electrical controls for the

thermoforming machine consisting of the Siemens S7-1214C PLC, the SM 1231TC analog

module, 2 relays, 2 sets of terminal blocks, and a 24VDC 5 Amp power supply. See Figure

117 and Figure 118 and Figure 119.

Figure 117 Electrical components enclosure

Figure 118 Electrical enclosure

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Figure 119: Electrical Enclosure Mounted (Front)

To mount the enclosure onto the steel frame 3 new holes had to be made to have a better

fit. We wanted the diameter of the holes was to be kept relatively the same as the ones that were

originally in the enclosure with so 1/4" x 1-1/14” sheet metal screws.

To mount the white panel that the electrical controls will go on, four ¼” additional holes

were made into the electrical enclosure so that four 1/4 “bolts and nuts can connect the white

panel the electrical enclosure.

In addition to the ¼” holes, 5 evenly spaced holes were made into the panel to be able to

mount 2 Din rails with #8 machine screws.

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Figure 120: White Back panel

All the controls components are made to be able to snap onto a DIN rail. After the holes

were made in the back panel and the enclosure the 2 rails we are using were mounted into the

enclosure. The controls components were then placed onto the rails.

Figure 121 DIN rails holding electrical components

Instead of having the power supply on the side of the electrical enclosure it was decided

that a better placement would be at the top of the inside of the enclosure so that our power and

low voltage cords can be ran through the knockouts on the left side of the enclosure.

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Figure 122 Power supply mounting

11. Final Design

Our final design was constructed on SolidWorks with careful evaluation. Our main goal

was to keep our machine as simple as possible while being user friendly. We wanted to make

sure this design was easy to disassemble if need be. If any parts needed to be replaced the whole

structure is designed so that the user does not have to struggle getting to the area. It was also

designed and programmed for safety to ensure that no injuries may occur. See Figure 123-128.

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Figure 123 Final machine design without heat covers

Figure 124 Final machine design with covers

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Figure 125 Front view of machine

Figure 126 Left side view

107

Figure 127 Right side view

Figure 128 Back side view

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(insert images of final machine)

12. Conclusion 12.1. Results

12.2. Further Implementation

13. SMC Capstone Reflections

Alexia Maldonado | Mechanical Engineering

Alexis Arredondo | Mechanical Engineering

James Curd | Mechanical Engineering

Looking back on the past 4 years at St. Mary’s University, I cannot visualize the

adventure being any different. The path to this degree has made me question many things in

my life but it has allowed me to see the grit that future engineers from St. Mary’s have.

It’s crazy to think that I came in knowing no one but leaving with a family. Well, crazy for

me to think that way. I remember being stressed out and lonely, feeling like I was the

dumbest person in the room. Slowly but surely, relationships with new friends and professors

started to take shape and suddenly it wasn’t just me against the world but my family and I

against it all. Through thick and thin my friends, family and the professors at St. Mary’s have

decided to stay with me and I could not be more blessed. This senior design project being in

the time of 2020-2021 makes me think of Rocky Balboa’s infamous speech and how life hits

hard. Although this was my Senior Year, I have never been closer to dropping out. If it

weren’t for my family and friends, chances are you’d never see this. What I am trying to get

at is throughout all the coursework, the SMCs, the basic classes, and the Engineering classes

nothing shines brighter than the relationships built and nurtured through these 4 years. Thank

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you, St. Mary’s, for allowing me to push to new heights I didn’t think were possible. Thank

you, God.

14. References

[1] A. Acrylics, "Thermoforming," Technical Bulletin 137, p. 6, May 2014.

[2] J. Florian, Practical thermoforming : principles and applications, New York: Marcel Dekker,

1996.

[3] A. S. L. F. P. I. D. P. D. Theodore L.Bergman, Introduction to Heat Transfer, Hoboken, NJ:

John Wiley & Sons, Inc., 2011.

[4] W. C. a. D.G., Materials Science and Engineering: An Introduction, John Wiley & Sons,

Inc, 2014.

[5] "Thermoforming Manual and Trouble-shooting Guide," Warsaw.

[6] A. L. G. J. I. H. Philip M. Gernhart, Munson, Young and Okiishi's Fundamentals of Fluid

Mechanics 8th ed., Hoboken: Wiley, 2016.

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15. Appendix

15.1. Machine Frame

111

15.2. Vacuum Camber

112

15.3. Clamp Tray

113

114

115

15.4. Pneumatic Cylinders

116

117

15.5. Guide Rails

118

119

15.6. Heater

120

121

Thermal Couple

15.7. Brackets

122

15.8. Sheet Panels

123

124

125

15.9. Electrical Components

126

127

128

15.10. Pricing Chart

129