Thermoforming Workbook Draft

Higher Institute for Plastics Fabrication

WORKBOOK for

Thermoforming Practical Course

Prepared by

Thermoforming Department 1st Edition 2009 Page 1

Wo r k b o o k fo r T h e r m o fo r m i n g P ra c t i c a l C o u r s e

ACKNOWLEDGEMENT

In its program to continuously improve the quality of instructions at the Higher Institute for Plastics Fabrication, the Curriculum Steering Committee initiated the creation of the workbooks for all practical courses being offered in the Institute. The Committee is headed by Dr. Khaled Al-Ghefaili, and the members are Dr. Ahmad Al-Ghamdi, Mr. Hiroshi Takeshita, Engr. Issa AlKhormi, Mr. Sumio Iwase, Mr. Kazuhiko Sawada, Mr. Sanjay Rawat, Mr. Zakaria Musa, and Mr. Virgilio Calpe.

This is the HIPF Workbook for Thermoforming Practical Course.

The

contents of this workbook were compiled through the efforts of the members of the Thermoforming Department, namely, Antonio Pasaoa (Head of the Department), Rameshwar Selukar, Joy Falaminiano, and Koichi Inagaki (Japanese Expert Adviser).

Editing, formatting and design by Virgilio

Calpe.

April 2009

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TABLE OF CONTENTS Introduction … … … … … … … … … … … … … … … … … … .

4

Course Objectives … … … … … … … … … … … … … … … … .

5

Grades Summary Sheet … … … … … … … … … … … … … … ...

6

Workshop Activities Activity 1—Introduction– Basic Principles of Thermoforming… … ..

7

Activity 2—Thermoforming General Safety Instructions… … … … .

16

Activity 3—Materials and Their Applications… … … … … … … ...

30

Activity 4—The Thermoforming Machine and Mold … … … … … .

40

Activity 5—Thermoforming Methods & Processes… … … … … …

53

Activity 6—Manpower and Standard Operating Procedures … … …

64

Activity 7—Product Quality, Defects and Troubleshooting … … … ..

74

Activity 8—Hands–on and Practical Training (1)… … … … … … ...

83

Activity 9—Hands–on and Practical Training (2) … … … … … … .

89

Activity 10—Hands–on and Practical Training (3) … … … … … …

95

Glossary … … … … … … … … … … … … … … … … … … … .

101

References … … … … … … … … … … … … … … … … … … ...

118

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INTRODUCTION As the demand for plastics continuously grow through the years, invention of many plastics manufacturing processes took place. Thermoforming is one of them. Thermoforming is the process of forming a thermoplastic sheet into a threedimensional shape by heating it to render it soft and formable, then applying different vacuum and pressure to make the sheet conform to the shape of a mold or die. Initially, thermoforming was more of manual operation and used for very specific and limited application and selected materials with only single cavity and longer cycle time. But due to technological breakthrough and rapid development through the years, thermoforming has improved and, so far, is now one of the best improved technology in terms of efficiency. In today's rapid research and product development, consumers are working continuously with major resin suppliers, rigid sheet extruders and original equipment manufacturers in developing high-tech, multi-layered plastic systems, which equal or outperform traditional materials in many applications. Thermoforming production processes nowadays are employed for engineering applications to an extent that only a few decades earlier would have been deemed impossible. Continually improving thermoplastics, in conjunction with the most modern machinery, have not only increased output rates but also the quality and precision of the moldings. Besides traditional applications, thermoforming has conquered an important market share with the pressure forming method of packaging particularly the food packaging industries.

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COURSE OBJECTIVES The purpose of this workbook is to enable the trainees to understand and carry out important activities in relation to Thermoforming. Focus will be on the functions in Thermoforming and the terminologies used in the industry. Upon completion of this course, the trainee shall be able to:

•

Have awareness in the importance of Thermoforming Plastic Fabrication technology.

•

Discuss and explain the concept, Thermoforming plastic fabrication.

•

To operate the Thermoforming machine safely and appropriately.

theories

and

practices

of

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GRADES SUMMARY SHEET Trainee Name: _________________________ Group: ________ Semester ___ School Year ___________

ACTIVITIES

GRADE

Activity 1—Introduction: Basic Principles of Thermoforming Activity 2—Thermoforming General Safety Instructions Activity 3—Materials and Their Applications Activity 4—The Thermoforming Machine and Mold Activity 5—Thermoforming Methods & Processes Activity 6—Manpower and Standard Operating Procedures Activity 7—Product Quality, Defects and Troubleshooting Activity 8—Hands–on and Practical Training (1) Activity 9—Hands–on and Practical Training (2) Activity 10—Hands–on and Practical Training (3) AVERAGE GRADE

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WORKSHOP ACTIVITY #1

Introduction: Basic Principles of Thermoforming THEORETICAL BACKGROUND In Thermoforming, the plastic sheet material in rolls will be thermally heated to make it soft and formable, and then vacuum and/or pressure is applied to form the shape of the mold. The formed products will be cut & separated from the skeleton or the runner while the molded products will be collected and packed accordingly. The runner or skeleton will be crushed and pelletized to convert it back again into pellet form which will then be mixed with virgin materials, normally at 20-30% ,to re-process back again into sheets.

The Six (6) Main Processes of a Thermoforming Machine: 1. Unwinding or Unreeling of Sheet Roll—The sheet is unrolled to dispense the material into the feed zone. Using a guided chain, the sheet is conveyed and is passed through the heater. 2. Heating—The sheet is heated to make it soft at a set parameters. 3. Forming (Shaping & Cooling)—The soft sheet is formed to the shape of the mold and then allowed to cool. Page 7

Wo r k b o o k fo r T h e r m o fo r m i n g P ra c t i c a l C o u r s e WORKSHOP ACTIVITY #1—Introduction: Basic Principles of Thermoforming

Theoretical Background … continued 4. Cutting—The molded product is separated from the runner or skeleton 5. Stacking—The product is collected in a stack and then ejected to the conveyor for packing 6. Winding of skeleton—The skeleton is collected and removed for recycling. Thermoforming process is different from the other plastic fabrication processes because its raw material is not the usual pellets being melted through the use of extruder to produce the desired shape using a die or molds but rather using the finished product of Sheet Extrusion which is the rolled sheet as its raw material.

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Theoretical Background … continued

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Theoretical Background … continued The Thermoforming industry started from Vacuum Forming using rigid PVC sheet. Since polystyrene (PS) was developed, PS sheet penetrated rapidly the Thermoforming industry due to easier formability. Process development for Pressure Forming and Plug Assist Forming expanded further the industry. Recently, polypropylene (PP) sheet is used in applications, in which heat resistance or oil resistance is required, where PS sheet can not be used. There are actually many thermoforming processes now available in the market but the three most commonly used basic processes are: 1. Vacuum Forming Process—The oldest and cheapest process in terms of equipment cost. 2. Pressure Forming Process—The fastest among the processes in terms of production speed (more than three times that of Vacuum Forming) due to higher pressure. 3. Plug-Assist Forming Process—For deep draw shapes like drinking cups & bowls. Applications: Packaging trays, cups, bowls, automotive panels, car roof top, boat hulls, large panels, spa baths, kitchen sinks… possibilities are endless…

One of the most important industries that thermoforming serves, however, is the packaging industry. Advantages of Thermoforming are: 1. Cheaper equipment and mold cost 2. Higher productivity due to its high speed 3. Thinner wall product, therefore, lesser material consumption and cheaper products 4. Lower production cost due to above features The only disadvantage of thermoforming so far is its high scrap rate due to its inevitable runner being generated as part of it production processes.

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OBJECTIVES OF THE ACTIVITY 1. To learn the basics of the Thermoforming processes 2. To identify the main parts of Thermoforming machine and their functions

PROCEDURE PART I—The Basics of Thermoforming Processes 1. Go to the Workshop floor (per group) and observe how the Thermoforming machine run. The process will be explained to you by your Instructor. 2. Using the data sheet form, list down the different stages or functions of the Thermoforming machine. 3. Using a stop watch, take the actual time needed to complete each of the stages and compute for the total cycle time. 4. Look at the monitor of the control panel and compare the total cycle time (actual cycle time versus the recorded cycle time in the machine). 5. Write down your observation in your data sheet. PART II—The Six (6) Main Parts of Thermoforming Machine 1. Using the drawing of Thermoforming machine in your data sheet, label the six (6) main parts of the machine in the space provided. 2. Write down the corresponding functions of each of the six main parts of the Thermoforming machine.

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Report Form - Page 1 of 4

Cut Report Form and Submit to Instructor

DATA S H E E T ACTIVITY #1—Introduction: Basic Principles of Thermoforming TRAINEE NAME

GROUP NO.

PART I—The Basics of Thermoforming Processes STAGES OF THERMOFORMING

FUNCTION

CYCLE TIME

1. 2. 3. 4. 5. 6. TOTAL RECORDED CYCLE TIME (STOP WATCH) TOTAL CYCLE TIME FROM CONTROL PANEL

PART II—The Six (6) Main Parts of Thermoforming Machine

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QUESTIONS & EXERCISES Select the correct answer. 1.

Thermoforming is the process of forming a thermoplastic sheet into a desired shape, by __________ heating it to make it soft and formable, then applying vacuum and/or pressure to make the sheet formed to the shape of the mold. a. mechanically b. conductively c. thermally d. electrically

2.

In thermoforming process, after the forming takes place, the sheet is held against the mold surface until __________. a. heated b. cooled c. warmed d. shaped

3.

In thermoforming process, after the forming takes place the formed product parts are then __________ off from the sheet. a. trimmed b. stacked c. ejected d. contracted

4.

In thermoforming process, after the forming, cutting and punching take place, the punched out sheet or the runner is usually __________, mixed with virgin material, and reprocessed into usable sheet again. a. reground b. scraped c. recycled d. as is

5.

__________ is the one of the four resources of thermoforming process. a. Water b. Electricity c. Manpower d. Compressed air

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QUESTIONS & EXERCISES … continued 6.

__________ is a device used to make or transform a thermoplastic sheet into any desired shape using a mold by applying heat and pressure. a. Sheet extrusion machine b. Advanced molding machine c. Thermoforming machine d. Injection molding machine

7.

One of the main functions of the mold is to __________ the material to the surfaces of the mold. a. receive and distribute b. heat c. cut d. separate

8.

Thermoforming machine process arrangement is designed in such a way that the __________ station comes after the heating work station to form the shape of the mold. a. winding b. stacking c. forming d. heating

9.

Besides traditional applications, thermoforming has conquered an important market share of packaging with the __________ forming method. a. pressure b. vacuum c. simple d. plug-assist

10.

The only disadvantage of thermoforming so far is its high _______ rate due to its inevitable runner being generated as part of it production processes. a. economical b. scrap c. productivity d. rejection

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CONCLUSION & RECOMMENDATIONS

___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ________________________ DATE: __________________

TRAINEE’S SIGNATURE

INSTRUCTOR’S COMMENTS

TRAINEE’S GRADE FOR THIS ACTIVITY

________________________ DATE: __________________

INSTRUCTOR’S SIGNATURE Page 15



Thermoforming General Safety Instructions THEORETICAL BACKGROUND Respect for Human Life

The Lives of Workers are Protected

A Safe workplace has positive effects on Safety Management

Corporate Management

operations of the company.

A safety-oriented corporation is trusted Social Credibility

by Society.

Figure 2.0—Objectives of Safety Management

A company manages safety to achieve the objectives shown in Figure 2. Safety when it comes in Manufacturing environment has the following meanings: •

There are no accidents that result in personal injuries.

•

There are no accidents that result in damage to property such as facilities, machinery, equipment, materials, or products.

•

There are no accidents that affect residents and areas around the factory.

•

The factory is managed to ensure that the above conditions are maintained continuously.

Why Is Safety Important? The importance of safety at work place can't be over exemplified. It is mostly felt in factories where the laborers are exposed to sustained risk in their daily operations. Adaptation of safety measures not only ensures safety of the life of the workers, but also of their families and their dependents.

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Wo r k b o o k fo r T h e r m o fo r m i n g P ra c t i c a l C o u r s e WORKSHOP ACTIVITY #2—Thermoforming General Safety Instructions

Theoretical Background … continued 2.1.2 Who is Responsible for Safety? Factory Company Executives

Manager/s

Supervisor/s

Personnel / Machine Operators

Figure 2.1—Safety Responsibility

From the employer down to the lowest level of position in the company, each person has his own safety responsibilities. It is a requirement in an corporate institution that all employees are properly instructed and supervised in the safe operation of any machinery, tool, equipment, process, or practice which they are authorized to use or apply. Basically, the employer must provide training to each employee to do each aspect of their job safely, and must provide adequate supervision of each employee to assure that the training was effective and that the employees are following safe procedures.

Thermoforming Machine Safety As an operator, you must always follow the signs and symbols, and you must be safety conscious to avoid accident. Ignorance is not an excuse when accident happens. Therefore, developing a safety habit is the best policy that should be adopted by everybody.

Remember, the life you save, maybe your own! Safety Instructions 1. Machine is a potential source of danger if it is operated by untrained operator. 2. The general directives on work safety, accident prevention must be complied as per the Instructor’s instructions.

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Theoretical Background … continued 3. Always work with concentration and be conscious of safety aspects! 4. Prior to starting work, check the orderly condition of the machine, in particular the operability of the safety devices. 5. Clarify any queries or unclear matters you may have regarding the work with and on the machine before starting work!

Warnings and Symbols The following designations and symbols are used to convey important information. Caution: Warning of a general source of danger, the consequence of which can be personal injury and/or damage to property Danger caused by electrical current or voltage! Warning against injury such as electric shock through electrically conducting devices. Hot parts or surfaces! Warning against danger of burns from parts or surfaces that have high temperatures even after the machine has been switched off. Not allowed for person with cardiac pacemaker! Persons with a cardiac pacemakers are not allowed to work on subassemblies that bear this symbol because there is danger from noise influences due to the static charging of the plastics film. Stay Away! Don’t move close to the part, it is dangerous area.

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Safety Measures

Emergency Buttons Actuation of an EMERGENCY STOP button interrupts the control voltage, switches off the compressed-air supply and de-aerates the compressed-air network up to the inlets of the solenoid valves.

Mechanical Locking of the Sliding Doors Safeguard against reaching into the machine while it is running. Machine cannot be switch ON “O” when sliding door is open; it also advices not to open the sliding door during operation.

Hand Lever with Securing Pin For limiting the travel range of the reel mounting, in order to avoid the danger of crushing.

Safety Limit Switch on the Door of the Skeletal Re-winder Safeguard against reaching into the rotating skeletal mounting.

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Safety Measures … continued

Back-pressure valves in the connections of the pneumatic cylinders on pneumatically operated machine parts To prevent these machine parts from moving when the machine is at a standstill.

An electrical pressure switch, with a fixed setting of 4 bar If the operating pressure falls below this value, the control voltage is switched off and the compressed air system is de-aerated.

Safety valves with a spring-centered, disabled middle position for the top and bottom frames of the forming station To safeguard against any undesired movements.

See Actual Machine Part

Mechanically lockable main switch on the switch cabinet. If the main switch is in position "0", all electrical subassemblies (control unit, heaters, electronic system) are de-energized. The compressed-air network is deaerated up to the inlets to the solenoid valves.

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Special Danger and Measures

CO2 Fire Extinguisher Fires can occur if the plastic being molded is overheated.

Gases and Vapors Depending on the plastics to be molded, gases and vapors can be formed at the heating-up temperature. Therefore, consult your Instructors or supervisor, should you need to make necessary provision for suitable extraction.

Technical Data Sheet (Technical Bulletin) Important to keep the Technical Data / Safety Data Sheet from the Thermoforming Sheet manufacturer / supplier, in particular the permissible maximum temperature values. Certain plastics may burn explosively on heating, e.g., cellulose-based plastics. Foam films may be processed only if they are foamed with non-inflammable gases.

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Special Danger and Measures … continued Do not touch the heaters! Heater

There is a danger of burning the heaters even after the main switch had been switched off.

Compliance with the Safety Standards d ve o r p Ap

If the machine is linked to special devices (e.g., filling devices, crusher device, packers), compliance with the safety standards attachment of these devices must be properly observed.

Personal Protective Equipment (PPE) a. Wearing of an appropriate protective helmet: •

Auxiliary equipment temporarily attached to the machine at head height during tool changing poses a risk.

b. Wearing of an appropriate safety shoes (have a high anti-static action) : •

During the thermoforming process, the guidance, unwinding, steering and winding of thermoplastic materials can create very high static charges, which cannot always be discharged safely.

c. Wearing of an appropriate protective gloves (with sufficient level of protection): •

Danger of cuts from sharp edges

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OBJECTIVES OF THE ACTIVITY 1. To learn the basics of safety and safety signs 2. To develop safety awareness among trainees and learn the most common hazards that may lead to injuries like amputations, lacerations, crushing injuries and abrasions in Workshop and Machine Operations.

PROCEDURE PART I—Safety and Warning Signs 1. Walk around the Workshop area and locate all the safety signs. 2. Observe the Machine area for unsafe points and try to identify safety / warning signs found. 3. In your data sheet, correctly write the names of the safety devices and warning signs in the pictures. PART II—Safety Devices Commonly Found in Thermoforming Machines 1. Walk around the Thermoforming Machine and try to locate all the safety devices present. 2. In your data sheet, write down the names of the safety devices and their functions.

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DATA S H E E T ACTIVITY #2—Thermoforming General Safety Instructions TRAINEE NAME

GROUP NO.

PART I—Safety and Warning Signs SAFETY DEVICES AND SAFETY SIGNS IN THE

HIPF Thermoforming area

1.

2.

3.

4.

5.

6.

7.

8.

9.

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DATA S H E E T ACTIVITY #2—Thermoforming General Safety Instructions TRAINEE NAME

GROUP NO.

PART II—Safety Devices Commonly Found in Thermoforming Machines

1. ________________

2. ________________

3. ________________

4. ________________

5. ________________

6. ________________

7. ________________

8. ________________

9. ________________ Page 25


WORKSHOP ACTIVITY #2—Thermoforming General Safety Instructions

QUESTIONS & EXERCISES Part I—Fill in the blanks from the given choices. 1. What are accidents? Accidents usually result from a combination of factors that includes both _____________________machine condition and ___________________ human actions. 2. Write down the names of PPE equipment to be used for each category. Eye - ___________________________________ Face - __________________________________ Head - __________________________________ Feet - ___________________________________ Hands and arms - _________________________ Bodies - _________________________________ Hearing - ________________________________ 3. A _________ colored warning triangle with black graphical symbol indicates what the hazard is. 4. A _________ colored circle-with-slash with black graphical symbol indicates a prohibited action to avoid the hazard. 5. A __________ colored mandatory action circle with white graphical symbol indicates an action to take to avoid the hazard.

plugs, earmuffs / Yellow / Red / Blue hazardous / careless / safety glasses, goggles / face shields / hard hats / safety shoes /gloves / vests / earANSWERS:



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QUESTIONS & EXERCISES … continued Part II—Choose the correct answer. 1. Which is the correct shape and color for a “Prohibitory Sign”?

2. Which is the correct color and shape for a “Mandatory Sign”?

3. Which is the correct color and shape for a “Fire Sign”?

4. Which is the correct color and shape for a “Fire Sign”?

5. Which is the correct color and shape for an “Information Sign”?

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QUESTIONS & EXERCISES … continued 6. Which is the correct meaning of the given sign below? a. b. c. d.

No naked lights Smoke-free rest area No smoking Smoking allowed

7. What do blue and white safety signs tell you? a. Things you must not do b. Things you must do c. The nearest fire exit d. There is a hazard in the area 8. Which is the correct image below which represents “Danger, electricity”?

9. When used on site what does this sign mean? a. b. c. d.

Mandatory Safe condition Warning Prohibited

10. What is the correct meaning of this sign? a. b. c. d.

Ear protection may be worn This is a noisy area Caution, deaf people nearby Ear protection must be worn

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___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ________________________ DATE: __________________




________________________ DATE: __________________




Materials and Their Applications THEORETICAL BACKGROUND As an operator, you must always know the material properties and processing conditions such as temperature, density, shrinkage, and other factors, so that it would be easy to set the processing parameters when using different thermoforming machines and molds.

What are Plastics? •

Plastics are man made chemicals extracted mainly from petroleum.

•

They are basically composed of hydrocarbons: groups of linked hydrogen and carbon atoms. (Imagine them as a small train and carriage!)

•

Most plastics are made up of long chains of hydrocarbons. (Identical small trains joined together to form one very long train.)

•

More than 50,000 molecules (long trains) may be joined in chains to produce polyethylene (or polythene).

•

Very long straight or branched chains are present in thermoplastics: for example, polyethylene and polystyrene.

•

Thermoplastics always soften when heated and harden when cooled down.

•

This makes these plastics ideal for the vacuum forming process.

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Wo r k b o o k fo r T h e r m o fo r m i n g P ra c t i c a l C o u r s e WORKSHOP ACTIVITY #3—Materials and Their Applications


POLYSTYRENE (PS) Polystyrene can be transparent or can be made to take on various colors. It is economical and is used for producing plastic model assembly kits such as cell phones frames, CD "jewel" cases, and many other objects where a fairly rigid, economical plastic is desired. However, its major application is in the food packaging industries.

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Theoretical Background … continued Polystyrenes are classified into two types. 1. GPPS - General Purpose Polystyrene •

Main characteristics: transparent, stiff, and brittle

•

GPPS is very stiff but brittle, and highly transparent (clear) glassy material. Due to high gloss and sparkling appearance, it is widely used in thermoforming process to produce cups and trays with glossy surface.

•

GPPS is used as surface layer for multi-layer sheet combined with HIPS.

2. HIPS - High Impact Polystyrene •

Main characteristics: high impact, opaque

•

HIPS is produced by physically adding rubber during polymerization process of GPPS to make it more impact-resistant.

•

High Impact Polystyrene is rubber–modified GPPS.

•

HIPS is particularly suitable for thermoforming because of its rigidity and high impact strength which means that it can be formed, punched, and sawn without difficulty.

Typical raw materials for PS sheet produced by SABIC:

Melt flow index Izod Impact Strength

GPPS PS125

HI-PS PS330

Transparent

Opaque

7.0 g/10min

4.0 g/10min

12.0 J/M

110.0 J/M

Typical PS sheet which can be used for Practice training: Three layer PS sheets:

GPPS / HIPS / GPPS GPPS / (HIPS + Regrind) / GPPS

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Theoretical Background … continued POLYPROPYLENE (PP) •

The second important material for thermoforming is polypropylene, a plastic material synthesized by stereo-regular polymerization of propylene using Ziegler-Natta catalyst.

•

It is the highest volume polymer in the world

•

Main characteristics: lightweight, transparent, heat resistant, chemical/ oil resistant, low in cost.

Types of PP used in Thermoforming: •

Isotactic polypropylene - Crystalline plastics

•

Isotactic PP has three kinds: 1.

PP Homopolymer - Transparent, brittle at low temperature

2.

Block copolymer with ethylene - Opaque, High impact at low temperature

3.

Random copolymer with ethylene - More transparent, less stiff

Key Properties of PP Used in Thermoforming: 1. Higher melt viscosity to avoid excess sagging in the Heating Station. - PP grade with lower melt flow rate is selected. 2. Depend on customer’s need. -

for transparent & glossy need: homopolymer or random copolymer is selected.

-

for high impact at low temperature without transparency need: block copolymer is selected.

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Theoretical Background … continued Typical PP sheet used for Practice Training Raw material for PP sheet •

SABIC PP 83EK10 Melt flow rate :1.2g/10min. Izod Impact

•

:No break

PP sheet Monolayer PP sheet Three layer PP sheet: PP/PP +Regrind/PP

Importance of Recycling in Thermoforming In thermoforming process, about 20 to 50% of plastic is generated as waste after the cutting process depending on product design, such as Cup or Bowl. The residual sheet after cutting called skeleton is processed in a recycling machine to crush and pelletize. The pellets from the recycling machine is fed back into the sheet extruder to make a sheet. Summary The two kinds of plastics used in Thermoforming process are PS and PP. Recycling is very important in Thermoforming. PS—Amorphous structure gives easier formability. Majority among plastics used in Thermoforming is PS. PP—Crystalline structure gives superior characteristics such as higher heat resistance and oil resistance. However, some difficulties in thermoforming include sagging in the heating station and higher shrinkage rate in the forming station.

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OBJECTIVES OF THE ACTIVITY 1. To give a brief review of the characteristics of plastics. 2. To discuss the two major types of plastics and their characteristics that is commonly used for the plastics manufacturing sector. 3. To know the importance of each material and their applications to the Thermoforming Industry.

PROCEDURE 1. In the classroom, bring two pieces of water cups, one PP and one PS. Try to observe the difference in characteristics between polypropylene (PP) and polystyrene (PS). 2. In the Machine site, observe behavior of each material (PS and PP) during processing and try to note the differences. 3. In your Data sheet, write your observations for each material (PP and PS). Define their characteristics when it is being use in thermoforming application.

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DATA S H E E T ACTIVITY #3—Materials and Their Applications TRAINEE NAME

GROUP NO.

Observations on Thermoforming Materials POLYPROPYLENE (PP) _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________

POLYSTYRENE (PS) _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________

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QUESTIONS & EXERCISES Choose the correct answer. 1. What are the (2) two major categories of Thermoplastic Materials? a. (Semi-) Crystalline & Amorphous b. Polystyrene & PVC c. Polystyrene d. Thermoset & (Semi-) Crystalline 2. To which thermoplastics category does polypropylene and polyethylene belong? a. Amorphous b. Thermoplastic Elastomer c. (Semi-) Crystalline d. None of the Above 3. A commonly used plastics material for thermoforming. a. polyacetal b. teflon c. PET d. nylon 4. Which material is recyclable? a. Polystyrene b. Epoxy resin c. Phenolic resin d. Polyester 5. What material is characterized to be translucent crystalline polymer that exhibits high stiffness? a. Epoxy resin b. Polypropylene c. Phenolic resin d. Thermosets 6. What are the 3 types of polystyrene? a. GPPS, HIPS, Expandable PS b. Epoxy, Polyester, Polypropylene c. Polyimides, Polypropylene, Polyvinyl Chloride d. Polyacetate, Polycarbonate, Polypropylene Page 37




QUESTIONS & EXERCISES … continued 7. What is the general term for a wide range of synthetic or semi-synthetic polymerization products? a. Plastic b. Polypropylene c. Scrap d. Recycling Process 8. Higher melt viscosity leads to excessive sagging in the Heating Station. Hence, PP grade with lower melt flow rate is selected for thermoforming. a. True b. False 9. High Impact Polystyrene is rubber–modified GPPS. a. True b. False 10. Thermoformed products are also used in automotive sector. a. True b. False

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___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ________________________ DATE: __________________




________________________ DATE: __________________




The Thermoforming Machine and Mold THEORETICAL BACKGROUND The Components of a Thermoforming Machine - Illig RV53b

Thermoforming Machine is a device use to make or transform a thermoplastic sheet into any desired shape using a mold by applying heat and pressure. THERMOFORMING MACHINE PARTS & FUNCTION Main Control Panel The Main control panel system is a device that regulates the Machine Operation process of each part connecting to each other.

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Wo r k b o o k fo r T h e r m o fo r m i n g P ra c t i c a l C o u r s e WORKSHOP ACTIVITY #4—The Thermoforming Machine and Mold

Theoretical Background … continued Unreeling/Unwinding Station To introduce the sheet into the Feed zone up to Heating station, the following procedures must be followed: •

Rolled sheet must be properly inserted into the shaft.

•

Using the Lever arm loader, rolled sheet must be firmly positioned in the unwinding stand and the exact tension should be applied.

Heating Station Thermoplastic sheet is heated and softened in this station. The guidelines for heating the sheet are the following: •

Temperature should be properly controlled to prevent excessive sag.

Forming Station In this station, the thermoplastic sheet is formed into its desired shape, with the required thermoforming process. Parts of Forming Station: •

Clamping Frames—used to guide and hold the sheet during machine operation.

•

Tool (Mold)—a devise used to form the plastic sheet into the desired shape.

•

Plug-assist—A mechanical device used in thermoforming to help distribute the heated plastic sheet more uniformly before it actually seats on the mold. Page 41


Theoretical Background … continued Cutting Station In this station, the molded products are cut and separated from the sheet/runner. Parts of Cutting Station: •

Knife Core—aluminum block that supports the knife.

•

Cutting Knife—sharp edged metal part used to cut and separate the formed products from the sheet .

Stacking Station In this station, the finished products are collected to the desired amount using the pusher. Parts of Stacking Station: •

Stacking Cage—part of stacking station where molded parts are collected and stacked at the desired quantity.

•

Pusher—used to put the molded parts into the stacking cage.

•

Ejector Plate—a plate located on top of the stacking station used to push the products on top of the conveyor.

Winding Station In this station, the runner is rolled or collected. Skeleton sheet or runner should be properly positioned at the winding roller.

Page 42


Theoretical Background … continued THERMOFORMING MOLDS Thermoforming mold is a device used to form the plastic sheet into the desired shape. There are two types of thermoforming molds: •

Prototype (Low Volume Production), and

•

Aluminum (High Speed - High Production)

Prototype Mold This is the mold that is used to make a part that will be evaluated for fit and function. It is used for low-volume production runs. Different Kinds of Prototype Mold •

Plaster/3D Print—Plaster molds are cast directly from the model and used for prototyping. Other casting method is by the use of special 3D printing device to form a mold that is precisely to what is needed.

•

Wood—A wooden mold is used mainly for a customer required prototype or a very low volume production run.

•

Epoxy/Polyurethane—A thermosetting plastic mold used for short production runs that may last at 100 up to 300 parts (shots).

Aluminum Mold This is a kind of mold made of cast (or machine) aluminum that is prepared by casting or by layering. Their surfaces can be textured or polished to a high gloss. Aluminum is an excellent heat conductor and permits rapid heating and cooling for fast cycles. Different Kinds of Aluminum Mold •

Porous Aluminum—An aluminum material used for products that require high optical quality or other cosmetic applications.

•

Cast Aluminum—Cast aluminum material is commonly used for thin gauge applications and having difficult shapes.

•

Solid Aluminum—Dedicated for technical/engineered trays.

Page 43


Theoretical Background … continued TWO TYPES OF MOLD DESIGNS

•

Male Mold—A male mold or convex mold that has one or more protrusions over which the heated sheet is drawn to form a shape.

•

Female Mold—Female mold or concave mold that has one or more cavities into which the heated sheet is drawn to form a shape.

THREE (3) KINDS OF MOLD COOLING SYSTEMS

•

Ambient Air / Air Spray—most commonly used in vacuum forming applications.

•

In-direct Cooling—the cooling is done thru a cooling block.

•

Direct Cooling—mold with integrated cooling channels.

Mold Cooling Table Type of production Prototypes max 100 trays Medium production 100 to 5000str/m

Ambient air, air spray

Indirect cooling

Direct cooling

Al tool

With PU tool

PU, Plaster, wood

High vol. Production >5000 str/m

Page 44


Theoretical Background … continued VENTING/VACUUM HOLES Vacuum holes are mold features where the negative air (vacuum air) is allowed to pass upon forcing the softened plastic sheet against the mold.

Standard Drilled Holes Dimension: Ø 0.3mm, Ø 0.5mm, Ø 3mm, Ø 5mm

Page 45


OBJECTIVES OF THE ACTIVITY 1. To be able to know the different kinds of thermoforming machines, the parts and function of an ILLIG thermoforming machine and their specifications. 2. To be able to learn the importance of thermoforming mold, its parts and the different methods applied. 3. To have a total knowledge about mold assembly and mold parts.

PROCEDURE Part I—The Basic Parts of Thermoforming Machine 1. Go to the machine site and try to know the different parts of the Thermoforming Machine. 2. Observe the motion of the different moving parts of the machine and how the plastics products are formed. 3. In your data sheet, give the names of the parts that are shown on the page and explain the functions of each of the parts. Part II—Thermoforming Mold 1. Familiarize yourself with the different mold materials used for thermoforming mold and try to identify the parts and methods applied in the mold. 2. In your data sheet, match the word that identify each category or word that related to each other and to its application

Page 46



DATA S H E E T ACTIVITY #4—The Thermoforming Machine and Mold TRAINEE NAME

GROUP NO.

Part I—The Basic Parts of Thermoforming Machine 1.

Part: Function:

2.

Part: Function:

3.

Part: Function:

4.

Part: Function:

Page 47




GROUP NO.

Part I—The Basic Parts of Thermoforming Machine … continued 5.

Part: Function:

6.

Part: Function:

7.

Part: Function:

Page 48




GROUP NO.

Part II—Thermoforming Mold TYPES OF THERMOFORMING MOLDS 1. Low volume production mold 2. Prototype mold made of wood 3. High volume production mold 4. Thermosetting plastic mold 5. Mold that has convex surface 6. Mold used for technical trays 7. Mold that has concave surface 8. Mold for high optical quality product Answer: (Pick the Answer and Match the word) Porous Aluminum Mold, Male Mold, Aluminum Mold, Prototype Mold, Female Mold, Solid Aluminum Mold, Epoxy/Polyurethane Mold, Wooden Mold. MOLD’S COOLING SYSTEM 1. Cooling thru cooling block 2. Mold w/ integrated cooling channels 3. Ambient air / air spray 4. Vacuum holes Answer: (Pick the Answer and Match the word) In-direct cooling, Drilled holes under the mold, Direct cooling, Vacuum forming conventional cooling Page 49




QUESTIONS & EXERCISES Choose the correct answer. 1.

____________ is a device having parts that perform or assist in performing any type of work. Devices with no rigid moving parts can be considered as tools. a. Machine b. Mold c. Method d. Material

2.

____________is a device used to make or transform a thermoplastic sheet into any desired shape using a mold by applying heat and pressure. a. Recycling machine b. Sheet extrusion machine c. Thermoforming machine d. Injection molding machine

3.

Maximum cycle rate of Illig RV53b thermoforming machine is ____________ cycles per minute. a. 20 b. 22 c. 24 d. 42

4.

What are the main functions of the thermoforming mold? a. Receive and distribute the material to the surface of the mold b. Cool the material after forming (water or oil as coolant) c. Eject the molded product out of the mold d. All of the above

5.

This is a device used to form the plastic sheet into its desired shape. a. Mold b. Plug-Assist c. Knife d. Pressure

Page 50




QUESTIONS & EXERCISES … continued 6. Identify the thermoforming machine work station shown in the picture. a. Winding station b. Unreeling station c. Heating station d. Forming station

7. Identify the thermoforming machine work station shown in the picture. a. Winding station b. Heating station c. Unreeling station d. Forming station

8. Identify the thermoforming machine work station shown in the picture. a. Forming station b. Unreeling station c. Heating station d. Winding station

9. Identify the thermoforming machine part shown in the picture. a. Plug Assist b. Thermoforming Mold c. Clamping frames d. Knife-core Assembly

10. Identify the thermoforming machine part shown in the picture. a. Mold b. Clamping Frame c. Plug-Assist d. Knife-core Assembly

Page 51





___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ________________________ DATE: __________________




________________________ DATE: __________________




Thermoforming Methods & Processes THEORETICAL BACKGROUND Thermoforming is a simple process: a sheet of thermoplastic is heated and formed into a designed shape by applying heat and pressure. The sheet is stretched into a larger shape, which reduces the sheet’s original thickness and results in a bigger surface area. THERMOFORMING METHODS & PROCESSES 1. Vacuum Forming Method Vacuum forming is a process that involves forming thermoplastic sheets into three-dimensional shapes through the application of heat and pressure. Advantages: • Economical for small to medium production runs • Low tooling costs • Quick startup • High strength to weight ratio • Efficient prototyping • No need for painting; the color and texture are formed in. Vacuum Forming Schematic Diagram

Heater

Formed Product

Heated Sheet

Female Mold

Vacuum Air

Page 53

Page 53

Wo r k b o o k fo r T h e r m o fo r m i n g P ra c t i c a l C o u r s e WORKSHOP ACTIVITY #5—Thermoforming Methods & Processes

Theoretical Background … continued 2. Pressure Forming Method A thermoforming technique whereby vacuum and pressure is used to force the hot plastic sheet against a mold surface to get a very crisp impression of that surface. Pressure Forming Schematic Diagram Pressure Box

Pressure Box

Heated Sheet

Pressurized Air

Mold

Vacuum Air

3. Plug Assist Forming Method This is basically the same as straight vacuum forming. But, the heated and softened sheet is pressed down into the mold by a plug. After the plug reaches a predefined depth, a vacuum is created inside the mold so that the sheet is drawn down and forms the shape of the container. Advantages: • Economical for small to medium production runs • Low tooling costs • Quick startup • High strength to weight ratio • Efficient prototyping • No need for painting; the color and texture are formed in.

Page 54


Theoretical Background … continued Plug Assist Forming Schematic Diagram Plug Assist Heated Sheet

Mold

Vent

4. Other Thermoforming Processes

•

Straight Vacuum Thermoforming

•

Drape Thermoforming

•

Free Draw Thermoforming

•

Matched-Mold Thermoforming

•

Snap-back Thermoforming

•

Billow Forming

•

Twin-Sheet Forming

Page 55


OBJECTIVES OF THE ACTIVITY 1. To give trainees an in-depth knowledge on the three (3) kinds of thermoforming processes, and the advantages and disadvantages of each method. 2. To give trainees an introduction to all the processes of an ILLIG RV 53b thermoforming machine.

PROCEDURE Part I—Thermoforming Methods/Processes 1. Go to the machine site and try to observe the process that is being used to get a good product. 2. In your data sheet, explain each given Thermoforming process and draw a simple schematic diagram of each. Part II—Thermoforming Machine (ILLIG RV53b) Processes 1. Familiarize yourself with the thermoforming processes of an ILLIG RV53b thermoforming machine. 2. In your data sheet, explain the whole process of the basic Thermoforming Machine (iLLig RV53b) and its methods of process.

Page 56



DATA S H E E T ACTIVITY #5—Thermoforming Methods & Processes TRAINEE NAME

GROUP NO.

Part I—Thermoforming Methods/Processes 1. Vacuum Forming Process Explain the process: _______________________________________________________________________ _______________________________________________________________________ ________________________________________________________________________

_______________________________________________________________________

_______________________________________________________________________

_______________________________________________________________________

Draw the schematic diagram.

Page 57




GROUP NO.

Part I—Thermoforming Methods/Processes … continued 2. Pressure Forming Process Explain the process: _______________________________________________________________________ _______________________________________________________________________ ________________________________________________________________________

_______________________________________________________________________

_______________________________________________________________________

_______________________________________________________________________


Page 58




GROUP NO.

Part I—Thermoforming Methods/Processes … continued 3. Plug-Assist Forming Process Explain the process: _______________________________________________________________________ _______________________________________________________________________ ________________________________________________________________________

_______________________________________________________________________

_______________________________________________________________________

_______________________________________________________________________


Page 59




GROUP NO.

Part II—Thermoforming Machine (ILLIG RV53b) Processes

Explain each process: Station 1

Station 2

Station 3

Station 4

Station 5

Station 6

Page 60




QUESTIONS & EXERCISES Choose the correct answer. 1. Heating is done by top and bottom infrared ceramic heaters with built in thermocouple. Heating allows sheet to ____________ without any physical contact. a. melt

b. soften

c. burn

d. crush

2. Upon switching the machine on, the screen page ____________ appears on the display screen of control panel. a. main menu b. temperature menu c. production menu d. clear menu 3. In automatic mode the cutting and stacking station ____________ after starting production. a. do not run

b. run

c. simultaneously run

d. intermittent run

4. We can select the operation mode by selecting the symbols in OPERATION MODES. To run the machine in auto mode which symbol do we need to select. (Please put tick mark on correct symbol in following picture).

5. Forming station has ____________ mold to form the sheet into the desired shape. This is done by application of either air and/or vacuum. a. top and bottom

b. top

c. bottom

d. sides

Page 61




QUESTIONS & EXERCISES … continued 6. The function of the unreeling device is to ____________ the rolled sheet into the machine thru the feeder zone using a sensor to activate the loading automatically. a. unload

b. hold

c. load

d. remove

7. What process of thermoforming is being applied when heated and softened plastic sheet from extrusion is placed at the top of a female mold and formed by vacuum only? a. Straight vacuum forming b. Pressure

c. Match mold forming d. Billow forming

8. What process of thermoforming is being applied when heated and softened plastics sheet is placed at top of a female mold and formed by pressure and vacuum? a. Straight vacuum forming c. Thermoforming b. Pressure forming d. Billow forming 9. What process of thermoforming is being applied when heated and softened plastics sheet is placed at the top of a female mold and formed and pressed by plug and with application of vacuum? a. Plug-assist forming

c. Billow forming

b. Pressure forming

d. Vacuum forming


b. top

c. bottom

d. sides

Page 62





___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ________________________ DATE: __________________




________________________ DATE: __________________




Manpower and Standard Operating Procedures THEORETICAL BACKGROUND Take note that Standard Operating Procedures and Policies can be effective catalysts to drive performance improvement and improving the desired results. Manpower is either an abstract term for human labor effort (as opposed to machines, animals etc.) or the number of available/needed for professional or other tasks. In plastic fabrication, manpower is referred to as the operator of the machine. Included in the manpower lists are anybody (overhead) from the supervisory level up to the highest position working in the company. Standard Operating Procedure for iLLiG RV 53b Thermoforming Machine OPERATOR’S ROLE: 1. Step by step approach on how to operate the RV 53b Thermoforming machine and its auxiliaries from start-up to shutting down operation including safety, product quality (checking procedures). 2. How to apply 3 “S” in the Standard Operating Procedures. Summary of SOP are the following : 1.0

2.0 3.0 4.0 5.0

Observe the Safety signs 1.1 Important Safety Reminders 1.2 Additional Important Reminder Switch on the air compressor. Switch on the water chiller as shown and set the recommended water temperature (normally at 10°C) Open the main air and water supply line by turning on valve. General Machine check-up

Page 64

Wo r k b o o k fo r T h e r m o fo r m i n g P ra c t i c a l C o u r s e WORKSHOP ACTIVITY #6—Manpower and Standard Operating Procedures

Theoretical Background … continued 6.0

When checklist has been complied and everything have been fulfilled, switch on the main power supply and the light switch on.

7.0

To ensure absolute safety, the lead Operator must double check.

8.0

Machine Switching-on Procedure

9.0

Overview of Control Panel Screen

10.0

Follow the procedure to star the machine and run the machine.

11.0

Doing quality checks and production segregation.

12.0

Follow the procedure to shut down the machine.

13.0

Do the last ‘S’.

14.0

Reporting system

Following is the example of how SOP explains the parts, Functions and the detail pictures and video procedures for operating individual part of each work station. (Note: - For detail SOP please refer the Hand outs of day 6.) Sample of SOP: 1

Push the main heater button switch.

Page 65


Theoretical Background … continued Sample of SOP: 2 FUNCTION—The function of the Unreeling Device is to load the rolled sheet into the machine thru the feeder zone using a sensor to activate the loading automatically. 7

6 4 5

2

1

3

1. Control panel—used to activate the loading/unloading of rolled sheet materials 2. Tension adjuster—used to regulate the movement of the loaded rolled sheet 3. Lever arm loader—used to load/unload rolled sheet using the control panel 4. Shaft for roll sheets—used to hold and unwind the rolled sheet 5. Pneumatic cylinder of lever arm—used to activate movement of the lever arm loader 6. Sheet feed roller—used to guide the sheet into the feeder zone 7. Feeder zone—used to guide the sheet into the chain conveyor

Page 66


Theoretical Background … continued Sample of SOP: 3—Reporting: Production Data: Cycles per minute—is determined from the cycle time. Cycle time—Time required for one cycle. Sheet unwind to the forming machine—Length of the sheet web in mm up to behind the forming station, if a roller preheater or unwind device is used. Production cycles—Quantity of cycles run in the current operation program. Production time—Time required for production. Reading Production Data From Control Panel

Page 67


OBJECTIVES OF THE ACTIVITY 1. To learn the importance of manpower in the plastics industry, specially the role of an Machine Operator 2. To understand the importance of the Standard Operating Procedure and its application in machine operations

PROCEDURE Part I - Thermoforming Methods/Processes 1. Proceed to the Machine site and follow the Standard Operating Procedure (Machine Start-up and Machine Shutdown) in operating the Thermoforming machine. 2. Put a check in the box in your data sheet to indicate that you have properly done the step.

SOP for Machine Startup 1.

Follow Safety Instructions.

2.

Switch on the air compressor.

3.

Switch on the water chiller and set the recommended water temperature (normally at 10°C).

4.

Open the main air and water supply line by turning ON valve.

5.

Do General Machine Check-up.

6.

When checklist has been complied and everything have been fulfilled, switch on the main power supply and the light switch.

7.


8.

Do Machine Cycle/Production Procedure.

9.

Do quality checks and production segregation. Page 68


Procedure … continued

SOP for Machine Shutdown 1.

Push the button to turn-off machine cycle.

2.

Push the button to turn off the heating.

3.

Check the machine and take-out the products/ skeleton/ runner inside of the machine.

4.

Push button to turn-off the control voltage.

5.

Check the temperature. When the heating temperature decreases and reached 300ºC, switch off the chiller.

6.

Switch off the main power of Thermoforming machine.

7.

Switch off the compressor.

8.

Do the “5S”.

9.

Follow the reporting system.

Page 69



DATA S H E E T ACTIVITY #6—Manpower and Standard Operating Procedures TRAINEE NAME

GROUP NO.

Standard Operating Procedure 1. Machine Startup Steps 1.

Check

Follow Safety Instructions. •

Important Safety Reminders

•

Additional Safety Reminders (Advise by Instructors)

2.


3.


4.


5.


6.


7.


8.


9.

Do quality checks and production segregation.

Page 70



DATA S H E E T ACTIVITY #6—Manpower and Standard Operating Procedures TRAINEE NAME

GROUP NO.

Standard Operating Procedure 2. Machine Shutdown Steps 1.


2.


3.

Check the machine and take-out the products/ skeleton/ runner inside of the machine.

4.


5.


6.


7.


8.

Do the “5S”.

9.


Check

Page 71




QUESTIONS & EXERCISES Choose the correct answer. 1. Actuation of ___________ is necessary if an unwanted thing happens during machine operations. a. Emergency Button b. Switch Button

c. Switch Valves d. Control

2. Upon switching on the machine, the screen page ____________ appears on the display screen of control panel. a. main menu b. temperature menu c. production menu d. clear menu 3. In automatic mode, the cutting and stacking station ____________ after starting production. a. do not run

b. run

c. simultaneously run

d. intermittently run

4. We can select the operation mode by selecting the symbols in OPERATION MODES. To run the machine in auto mode, which symbol do we need to select? (Please put tick mark on correct symbol in following picture).


b. top

c. bottom

d. sides

Page 72





___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ________________________ DATE: __________________




________________________ DATE: __________________




Product Quality, Defects and Troubleshooting THEORETICAL BACKGROUND Quality is defined in everyday life and in business, engineering and manufacturing as the non-inferiority, superiority or usefulness of plastic products. As an operator, you must always know the different defects and their impact on quality of the products from the users point of view. You must know how to overcome and fix the various problems during production by making use of process parameters. The meaning of quality has developed over time with various interpretations below: 1. ISO 9000—"Degree to which a set of inherent characteristic fulfills requirements" 2. Six Sigma—"Uniformity around a target value" 3. Philip B. Crosby—"Conformance to requirements". Crosby treats customer expectations as a separate problem. 4. Genichi Taguchi—Taguchi's definition of quality is based on a more comprehensive view of the production system: Quality as "The loss a product imposes on society after it is shipped". Different Quality Concepts Many different techniques and concepts have evolved to improve product or service quality, namely; SPC, Zero Defects, Six Sigma, Quality Circles, TQM, Quality Management Systems (ISO 9000 & others) and Continuous Improvement. The quality of a product or service refers to the perception of the degree to which the product or service meets the customer's expectations.

Page 74

Wo r k b o o k fo r T h e r m o fo r m i n g P ra c t i c a l C o u r s e WORKSHOP ACTIVITY #7—Product Quality, Defects and Troubleshooting

Theoretical Background … continued Quality Drives Productivity Quality has no specific meaning unless related to a specific function and/or object. Quality is a perceptual, conditional and somewhat subjective attribute. In plastic fabrication industry, it is commonly stated that “Quality drives productivity.” Inspection, which is what Quality Assurance usually means, is historical, since the work is done. The best way to think about quality is in process control. If the process is under control, inspection is not necessary. Factors Influencing Product Quality Processing Parameters 1. 2. 3. 4.

Time Temperature Pressure Speed

Processing Components • •

Raw Material Quality Sheet Quality

Environmental Factors Climatic conditions—Any change in climatic conditions can change the process and, accordingly, the quality of the product changes.

Page 75


Theoretical Background … continued Achieving Quality To achieve good quality in the end product, the sheet thickness, the layer thickness and the surface area of sheet must be of good quality. All service conditions and the majority of end use applications involve some degree of mechanical loading. In general, thermoforming is possible with the sheet ranging in thickness from 0.5 to 15 mm. TROUBLESHOOTING Troubleshooting is not an exact science and often involves juggling a dozen or more variables in a single sheet. The best way to look at and solve these components are in three stages, namely: 1. The "Symptom": What is it that you see, feel, or measure? What is the viewed problem with the formed part? 2. The "Root Cause" or "Disease" Issue: There may be a number of these that could cause a similar "symptom." 3. The "Cure": What are the options that we have to get at the root cause of the problem?

Page 76


Theoretical Background … continued Common Forming Defects

•

Uneven wall thickness

•

Wrinkles

•

Warped parts

•

Incomplete forming of parts

•

Poor surface finish

•

Blushing or loss of color

•

Chill marks or mark-off

•

Nipple on mold side of formed part

•

Poor wall thickness distribution and excessive thinking in some areas

•

Shrink marks

•

Voids or bubbles in formed parts

•

Tearing of sheet during forming

•

Crazed or brittle parts

SUMMARY The most progressive view of quality is that it is defined entirely by the customer or end user and is based upon that person's evaluation of the entire customer experience.

Page 77


OBJECTIVES OF THE ACTIVITY 1. To learn the basics of Quality checking and its importance to the production. 2. To identify different kinds of product defects and perform troubleshooting.

PROCEDURE 1. Operate the RV53b Thermoforming Machine and collect product samples. 2. Segregate the good products and the rejected (bad) products. 3. Identify the kind of defect that the rejected (bad) products have. 4. Suggest a solution to eliminate the defects and do troubleshooting. 5. In your data sheet, write down the defects and explain what solution/s were made to correct the problem.

Page 78



DATA S H E E T ACTIVITY #7—Product Quality, Defects and Troubleshooting TRAINEE NAME

1

2

3

4

GROUP NO.

Description of Defects Found on Products

Troubleshooting: What did you do to correct the problem?

__________________________________

__________________________________

__________________________________

__________________________________

__________________________________

__________________________________

__________________________________

__________________________________

__________________________________

__________________________________

__________________________________

__________________________________

__________________________________

__________________________________

__________________________________

__________________________________

__________________________________

__________________________________

__________________________________

__________________________________

__________________________________

__________________________________

__________________________________

__________________________________

__________________________________

__________________________________

__________________________________

__________________________________

__________________________________

__________________________________

__________________________________

__________________________________

__________________________________

__________________________________

__________________________________

__________________________________

__________________________________

__________________________________

__________________________________

__________________________________

Page 79




QUESTIONS & EXERCISES 1. _________ is a degree to which a set of inherent characteristic fulfills requirements. a. ISO 9000 b. Quality Form c. Quality Data d. Fishbone Diagram 2. ___________ is one of the 4 factors that influence product quality. a. Temperature b. People c. Animals d. Food 3. ___________ is the process of recovering scrap or waste plastics products and reprocessing it again. a. Recycling b. Cycling c. Production d. Troubleshooting 4. When we get marks at the bottom of the thermoformed part, we need to increase the dimensions / numbers of ____________ holes. a. venting / vacuum b. cooling holes c. tube pipe d. PVC pipe 5. When the sheet is overheated, operator must reduce the heater temperature and decrease ________ time. a. cycle b. cutting c. speed d. clearance

Page 80




QUESTIONS & EXERCISES … continued 6. If pressure and/or vacuum timing is not optimized, then we get very good parts. a. True b. False 7. Sagging of material (when material touches the mold) results in folds on thermoformed part. a. True b. False 8. Besides traditional applications and the use of pressure forming method, thermoforming has conquered an important market share in the packaging industry. a. True b. False 9. Choose three (3) factors influencing product quality. a. Processing Parameters b. Processing Components c. Manpower d. Environmental Factors e. Machine Capacity f. Environmental Factors 10. Choose two (2) processing components. a. Raw Material Quality b. Temperature c. Manpower d. Pressure e. Sheet Quality f. Management g. Machine

Page 81





___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ________________________ DATE: __________________




________________________ DATE: __________________




Hands-on and Practical Training (1) THEORETICAL BACKGROUND After successfully completing all the topics from session 1-7, it is now time to apply all the principles, theories and actual machine practices that you have learned so that you will develop your skills (machine operation proficiency). However, since we have only one machine, you will be divided into 8 groups at 4-5 trainees per group. You are advised to review from time all the hand outs given to you aside from the classroom review class to be conducted by your Senior and Junior Instructions while you are waiting for your turn to operate the machine. You will also be taught on how to fill up the machine parameters, production report and activity report forms.

PRACTICE YOUR OPERATIONS SKILLS! 1.

2. 3. 4.

5. 6.

Now that you have learned the basics of the thermoforming process, it is time to practice your skills in running the plant and producing acceptable products. Strictly follow the Standard Operating Procedures (SOP) for each plant operations that you are going to perform. Use the worksheet tables and forms in the next pages to record your data. After each practice operations, write your general comment on the how well you have done your practice in the Conclusion & Recommendations page. Write down what you have done well, and what you should improve for the next practice. Enjoy practicing while being safe!

Page 83

Wo r k b o o k fo r T h e r m o fo r m i n g P ra c t i c a l C o u r s e WORKSHOP ACTIVITY #8—Hands-on and Practical Training (1)

STANDARD OPERATING PROCEDURES



2.


3.


4.


5.


6.


7.


8.


9.




2.


3.

Check the machine and take-out the products/ skeleton/runner inside of the machine.

4.


5.


6.


7.


8.

Do the “5S”.

9.


Page 84



DATA S H E E T ACTIVITY #8—Hands-on and Practical Training (1) TRAINEE NAME

GROUP NO.

MACHINE PARAMETER FORM

Illig Thermoforming Machine RV 53b Parameter Setting Record

Prepared by :

Checked by : Thermoforming Senior Instructors

Page 85




GROUP NO.

PRODUCTION REPORT FORM

Illig Thermoforming Machine RV 53b Production Report

Prepared by :


Page 86




GROUP NO.

ACTIVITY REPORT FORM

Illig Thermoforming Machine RV 53b Date:

Time:

Prepared by :


Page 87





___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ________________________ DATE: __________________




________________________ DATE: __________________






2. 3. 4.

5. 6.


Page 89





2.


3.


4.


5.


6.


7.


8.


9.




2.


3.


4.


5.


6.


7.


8.

Do the “5S”.

9.


Page 90




GROUP NO.



Prepared by :


Page 91




GROUP NO.



Prepared by :


Page 92




GROUP NO.



Time:

Prepared by :


Page 93





___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ________________________ DATE: __________________




________________________ DATE: __________________






2. 3. 4.

5. 6.


Page 95





2.


3.


4.


5.


6.


7.


8.


9.




2.


3.


4.


5.


6.


7.


8.

Do the “5S”.

9.


Page 96




GROUP NO.



Prepared by :


Page 97




GROUP NO.



Prepared by :


Page 98




GROUP NO.



Time:

Prepared by :


Page 99





___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ________________________ DATE: __________________




________________________ DATE: __________________



Glossary of Technical Terms for Thermoforming ABS

Acrylonitrile-Butadiene-Styrene terpolymer

Absorption

Is the process of radiant energy being absorbed in the plastic as it is being heated up.

Air convection

Heat energy transferred to a plastic via the movement of hot air about its surface area.

Air convection oven The chamber or structure used to deliver hot air to the surface of a plastic. AES

A saturated olefinic rubber modified styreneacrylonitrile terpolymer generally used in outdoor exposure applications.

Alkali

Acid-neutralizing chemical substance: a water-soluble chemical that reacts with acids to form salts, has a pH above 7, and turns red litmus paper blue.

Alloy

A combination of blended polymers or copolymers that result in unique physical properties not available in the single polymer. An example is Polyvinyl Chloride combined with Acrylonitrile-butadienestyrene.

Amorphous polymers

Polymers devoid of orderly molecular structures. They exhibit a broad melting range as opposed to crystalline structures.

ASA

An acrylic rubber modified styrene-acrylonitrile terpolymer generally used in outdoor exposure applications.

Atmospheric pressure

The pressure that is applied to the earth’s surface due to the weight of the air surrounding the surface of the earth. At sea level it is 14.7 pounds per square inch.

Banbury mixing

A system of mixing materials together using a pair of contra-rotating rotors that force the materials together (Continued on page 102)

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(Continued from page 101)

into a homogeneous blend through friction and pressure. This is an excellent mixing system and probably the best one available for compounding plastic alloys. Bank

A group of heating elements that are connected together with a common electric circuit.

Billow

Pre-stretching a heated plastic sheet by injecting air into a chamber that has the plastic sheet sealed over the edges of the chamber.

Black body

A body that emits the maximum amount of radiant energy at a given wavelength.

Black panel heaters (solar panels) Heaters with resistance wires imbedded in a routed out ceramic fiber refractory board and covered with a black panel quartz or glass plate. Bleed off

The act of letting air out of a mold chamber to allow a billow to stretch uniformly over a mold so the bubble does not burst during the forming operation.

Blisters

A depression on the surface of a heated plastic sheet or part caused by the rupturing of the surface of the plastic as the trapped gases are expanding very rapidly and escaping as the plastic is softening and allowing the rupture.

Bridging

This is a condition whereby the plastic stretching across a mold cavity during the forming operation does not pull down tightly against the mold surface.

Bubble

A pre-stretched piece of plastic that is obtained by sealing the plastic over a vacuum or pressure box and applying a vacuum or air pressure to this box causing it to develop a concave or convex hemisphere.

Calrod

A resistance wire packed in magnesium inside a stainless steel tube. When sending electricity through this wire, the tube will heat up and give off radiant and convective energy. (Continued on page 103)

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Catalytic gas heater An enclosed panel in which natural or propane gas enters into it and is dispersed throughout the panel and ignited. This causes the panel to give off heat through radiant and convective energy. Cavity mold

A female mold in which a part is drawn into it via vacuum or pressure.

Ceramic heater

A resistance wire trapped within a ceramic shell that will heat up when an electric current is passed through the wire. It is very efficient at given off radiant and convective energy.

Chain drive

A system of raising or lowering the platens on a thermoforming machine. Chain drives can also be used to shuttle the plastic into and out of the oven.

Chemical reactor

The vessel that is used to polymerize a monomer through the use of heat and pressure in the presence of a catalyst.

Chemical resistance The ability of a material to resist having its properties changed when being exposed to a substance that could potentially chemically attack it. Chill marks

A wavy surface imperfection that is caused by contact of the hot plastic to the mold surface before other parts of the hot plastic contact it.

Clamping frame (mechanism) A mechanical means of holding the edges of a plastic sheet while it is being heated in an oven. After the sheet is heated it provides a method of sealing the plastic to the mold edge to make it possible to draw a vacuum. Coefficient of thermal expansion The fractional change in length of a material in response to a change in temperature. For plastics this value is somewhere in the range of ten to the minus fifth, times the temperature change, times the length or thickness of the part in inches. (Continued on page 104)

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Commodity materials

Materials that generally are similar and can be bought and sold based on current market conditions. For instance, benzene is a commodity. What difference does it make where or who you buy it from?

Conduction

A method of transferring energy to a material or body through direct contact.

Conductive plastics

Plastics that can actually conduct an electric current, albeit very weakly and slowly, that will dissipate an electric charge.

Contoured box – snapback This is a box that has roughly the same shape as the mold you are trying to form the plastic over. It has calculated amounts of clearances that prevent the plastic from being pulled into the vacuum box too deeply so webbing and thinning do not occur. Convection

A method of transferring energy to a material or body via the use of fluids or air flowing about that body.

Cooling

The process of removing heat from a formed plastic part as it is drawn onto the mold.

Cooling lines

Tubes running through a mold that carry the fluid that either heats up or cools off the temperature of a mold to keep it consistent.

Cooling fixture

A device that is used to hold the shape of a part after it is removed from the mold and is cooling off. Typically it is used to maintain dimensional stability.

Crystalline polymers Polymers that have sharp melting points. Crystallinity

A state whereby the molecular structure of a resin arranges itself in a symmetrical, geometrical, threedimensional pattern forming a polymer.

Cycles – cycle time

A complete sequence of events that occur in making a plastic part from the loading of the sheet to the loading of the next sheet to make a second part. A time lapse (Continued on page 105)

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between identical spots within a repeatable sequence of events. Depth of draw

The distance that the mold protrudes out of the mold base or the depth the cavity extends within the mold from the mold base surface.

Die cutting

A system of trimming plastic parts that takes a steel rule die and applies enough pressure to cut through the desired areas of the plastic an stopping against a support plate. A second system is taking two sharpened edges and sliding them past each other through the plane of a plastic part.

Die lines

Linear grooves or depressions in the back of an extruded sheet that parallel the machine direction of the plastic sheet. They are usually caused by hang-ups in the die or nicks on the die lips.

Dimple

A depression in the surface of the plastic sheet or formed part. The dimple can be caused by a void within the plastic sheet or moisture within the surface of the sheet that ruptures when the sheet is heated.

Discoloration

The process of a plastic changing color through exposure of sunlight or applying a substance to the plastic that chemically attacks it.

Draft

The slope of the vertical edges of a mold that is used to facilitate the removal of the part from the mold.

Drape

The process of pulling a hot piece of plastic over a mold creating a seal along the mold edges.

Draw ratio (stretch ratio) The ratio of the starting thickness of the plastic sheet to the final thickness of the plastic on the formed part. Calculating this ratio depends on the geometry of the part. Elongation

The amount in length a material can increase without breaking when put under stressed tension. (Continued on page 106)

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Emissivity

The ratio of radiation intensity from a surface to the radiation intensity at the same wavelength from a blackbody at the same temperature.

Entropy

The tendency of an energy system or organized entity to break down.

EPDM

Ethylene Propylene Diene Monomer that is used as a rubber impact modifier in weatherable plastics.

Epoxy resin

A thermosetting plastic used for making molds or tooling fixtures.

Excessive moisture

The amount of water that is absorbed in the surface of a plastic sheet or resin that will keep you from processing it.

Female mold

A cavity used to stretch a piece of plastic over.

Fiberglass

Fine strands of glass usually encapsulated within a resin matrix. It can be used to make molds or structural parts.

Flammability

A measure of the extent to which a material will support combustion.

Flow characteristics The ability of a heated plastic to pass through a die, through an orifice, or over a mold in a smooth and uniform way to allow you to make a sheet or formed part. Foam core materials Materials that have gas expanded or air occupied structures between their solid exterior surfaces. Expanded vinyl or polyethylenes are good examples. Forming temperature

The temperature at which a plastic will shape into the geometry you are attempting to attain.

Forming temperature range The high and low points at which a plastic will be successfully shaped with the detail and dimensional tolerances required for an acceptable part. (Continued on page 107)

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Forming technique

A regimented process of steps that allow you to form a flat sheet into a desired shape. There are numerous processes that will accomplish this depending on how complex a shape you are trying to make.

Gas flame heating

A heating system that employs an open gas flame to heat up a plastic sheet. This system gives off both, convective and radiant heat energy.

Gas regulator

A device that controls the amount of gas that enters a gas heating system thereby controlling the heat output.

Gels

Hard particles of resin that are similar to the plastic matrix they are in but because of their molecular or cross-linked nature, will not blend in with the other plastic and will leave a tiny blip on the surface of the plastic sheet or part. If they are large enough they will show in the surface of the plastic part as the sheet is thinned out to form the part.

Glass transition temperature The temperature at which a rigid plastic softens enough to become somewhat rubbery. Hardness

The property of a material that determines how rigid or resistant to denting a substance is. In rigid plastics this is measured by a Rockwell hardness test.

Heat distortion temperature This is the temperature at which a plastic will begin to distort as measured with test bars using a standard ASTM test method. Heating oven

The device used to heat up a plastic sheet to forming temperature. Usually this type of oven is tightly zonecontrolled to distribute heat to the desired areas.

Heating profile

The pattern of heat being applied to a plastic sheet while it is enclosed within an oven so that the heat will be localized within the sheet and allow certain areas to stretch more than others during the forming process.

Heater types

These are the various types of elements that are used to heat up plastic sheet. General types listed in this (Continued on page 108)

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manual are: ceramic, solar panel, calrod, quartz, catalytic gas, open flame gas, nichrome wire, and air convection. High impact polystyrene This is a resin composed of numerous styrene monomer molecules polymerized into long polymer chains and dispersed with soft rubber particles throughout the rigid polystyrene matrix. Hot strength

The resistance of a heated plastic sheet to being stretched into the shape of a mold.

Hydraulic

A system of putting fluids under compression to move the platens on a thermoforming machine up and down. Usually used in conjunction with pressure-forming to allow maximum clamping pressure.

Hygroscopic

The characteristic within a plastic that gives it an affinity to pick up and retain moisture.

Impact strength

The ability of a material to undergo a sudden shock without breaking. This can be tested in plastics via a notched izod or falling dart impact test through standard ASTM test methods.

KORAD

An acrylic film used to hold color stability and UV degradation when laminated to plastic sheet.

Louvers

Air or lighting vents designed into a plastic part.

Male mold

A protrusion extending out of a flat plane that is used to form hot plastic over.

Materials

Plastic compounds used to construct useful shapes.

Material distribution

The process of stretching hot plastic over a mold and maintaining desired thicknesses in specific areas of the part.

Melt temperature (point) The temperature at which a polymer changes from a solid to a viscous liquid. (Continued on page 109)

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Micro-switch

A device used to electrically stop a moving part on a machine in the same place consistently.

Moat

A groove in a mold used to provide a good sealing point to prevent a plastic from breaking its vacuum bond with the mold as the plastic is shrinking during the cooling cycle.

Mold

(v) To shape a heated plastic sheet via heat and vacuum (pressure) into a desired geometry. (n) The cavity or protrusion used to shape a heated plastic sheet into a desired shape.

Mold base

The plane that a mold cavity or mold protrusion is mounted to that is used to seal off the hot plastic sheet during the vacuum part of the forming cycle.

Mold shrinkage

The amount that the plastic part shrinks in relation to the actual mold size after the part is removed from the mold and has reached ambient air temperature. This value is usually expressed in inches per inch. The typical shrinkage for ABS is .006” .001”.

Nichrome-wire heaters A type of heater unit that resembles a wire in a toaster. It typically heats up to its maximum or cools off fairly quickly. Notch sensitive

Most plastics exhibit a tendency to crack or break along a notch or scratch in the surface if an excessive bending stress is applied to that surface.

Ohms per square

The resistance to an electrical charge flowing across the same surface of a piece of plastic.

Olefins

A group of unsaturated hydrocarbons of the general formula CnH2n. Examples are polyethylene or polypropylene.

Orientation

The alignment of polymer chains to create stress in a given direction. With thermoplastic materials this condition causes the molecular structure of the plastic to be stressed more in one direction than the other. (Continued on page 110)

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Percentage timer

A timing device that has a total amount of set time, say 15 seconds as 100%. This timer can then be set at a certain percent, such as 50%, in which case it would be allowing a current to flow through a heating element for 7.5 seconds and not allowing it to flow for 7.5 seconds.

PETG

A clear, amorphous, glycol-modified polyester which is polymerized from dimethyl ester or terephthalic acid and ethylene glycol. This gives it a better forming window than PET.

Physical properties

Those characteristics that define the physical parameters of a material, such as stiffness, hardness, impact resistance, chemical resistance, etc. These properties can be tested and compared to other materials.

Physical testing

The process of measuring the characteristics of a material based on standard test methods.

Pimple

A raised area on a sheet of plastic or plastic part caused by a hardened particle or contaminant within the matrix of the plastic substrate.

Plastic sheet

A flat piece of plastic having a specific length, width, thickness and texture.

Plasticizer

A material that can be added to plastics that allow them to be processed more easily and can change certain of their physical characteristics such as toughness or flexibility.

Platen

A movable support mechanism that a plug or mold is attached to that assists in forming a plastic part.

Plug assist

A mechanical device used in thermoforming to help distribute the heated plastic sheet more uniformly before it actually seats on the mold.

Pneumatic

A system where a device is operated via the use of compressed air. (Continued on page 111)

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Polycarbonate

polyester of carbonic acid produced by using an interfacial reaction between dihydric or polyhydric phenols and a suitable carbonate precursor such as dichlorocarbonate. It is a clear, amorphous material with good impact strength and a high heat distortion.

Polycarbonate/ABS An alloy of the two different resins that will provide some unique physical properties depending on the mix of the two materials. Polyester

A resin made via the reaction of a dibasic acid and a dihydroxy alcohol. It is used as a resin base to make structural parts.

Polyethylene

A thermoplastic material made by polymerization of ethylene molecules. A large range of polyethylene’s can be made by varying the chain length and additives to the polymer.

Polymer

A organic substance obtained by joining the same type of monomers into long chains. For example ethylene is polymerized into polyethylene through heat, pressure and catalyzation.

Polymerize

The process of joining numerous like monomers into a long chain.

Polypropylene

A thermoplastic material made by polymerization of propylene molecules.

Polystyrene

A clear, amorphous, themoplastic material made by the polymerization of the sytrene monomer.

Pressure box

The reinforced box that is draped over the mold in the pressure forming system to provide the added force required to get good detail from the mold surface.

Pressure forming

A thermoforming technique whereby vacuum and pressure is used to force the hot plastic sheet against a mold surface to get a very crisp impression of that surface. (Continued on page 112)

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Processing

The act of converting a plastic resin or sheet into a useful form or shape.

Processor

The entity that converts a plastic resin or sheet into a useful form or shape.

Prototype mold

The mold that is used to make a part that will be evaluated for fit and function.

Punch press stamping The process of trimming a formed part by using a metal die clamped to a movable platen in a mechanical press. Forcing the platen against a fixed base pinches the desired surface of the plastic part and removes the unwanted excess. PVC

An amorphous thermoplastic material made up of vinyl chloride polymers. It is widely used in wire covering and where a chemically resistant plastic is needed.

PVC/ABS

An alloy of polyvinyl chloride and acrylonitrile butadiene styrene combined to maximize certain physical properties.

PVC/Acrylic

An alloy of polyvinyl chloride and acrylic combined to maximize specific physical properties.

Quartz heaters

A type of heater with about a one-half to three-quarter inch diameter tube with a resistance wire inside of it that is backed up by an internal reflector.

Radiant heat

An electromagnetic transfer of energy from a heating emitter to a material or body one would wish to raise the temperature of.

Radii

The rounded edges or curvature of the shape being dealt with. Typically these radii are designed into the part.

Reflected off energy The small amount of radiant energy directed at a plastic sheet that is left over from the energy that (Continued on page 113)

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penetrates through the sheet and is absorbed by the sheet. Regrind

The plastic materials that are reprocessed into plastic sheet or finished parts more than once.

Ribs

A raised or depressed area of a formed part that is designed into it to increase its structural integrity.

Robotic trimming

A mechanized method of performing a secondary operation on a formed part to enable it to comply with dimensional specifications.

Router

A high speed air or electrically operated cutting tool used to trim materials to dimensional specifications.

Sag

The amount of spherical deflection a flat plastic sheet experiences as it is heated to its forming temperature.

Sag bands

The supporting system that is attached to the clamping frame to obtain multiple minor sags when using a multiple cavity mold.

Sandblast

The process of forcefully blowing sand against an object to clean it or put a fine suede-looking surface on it.

Screening

The process of blocking out some radiant energy from reaching the plastic sheet suspended in an oven by putting in metal window screening between the plastic sheet and the heating elements used to heat the plastic.

Seal

The edge of a mold base that a hot piece of plastic is forced against to keep the vacuum enclosed within the mold chamber while a part is being formed.

Secondary draw ratio

After the initial thickness of plastic is determined on a formed part, the thickness of any secondary pockets or protrusions will be determined by the difference in thickness of the material now available divided by the area left over on the secondary area of the part. (Continued on page 114)

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Secondary operations

Those processes that are performed after the initial forming operation is completed, such as trimming and assembly.

Shrinkage

The phenomenon whereby a plastic decreases in size linearly and volumetrically as it is cooled. This term also refers to the inherent stress put into the extruded sheet during the manufacturing process.

Snapback

A thermoforming technique that first pre-forms a bubble into a pre-draw box, then plunges a male mold into the inside of the bubble, and as a final step, vacuums the bubble onto the mold.

Stiffness

A measure of the flexibility or rigidity of a material. This value is usually expressed in terms of flexural strength or flexural modulus.

Stress

Pressure applied to a given body to deform or fracture it.

Strength

the ability to withstand force, pressure, or stress. Also the ability to resist attack.

Symmetrical

An object having a mirror image of itself with respect to its centerline. One side of the part is identical to the other side.

Syntactic foam

A combination of inorganic foam spheres in a plastic foam matrix. This material is used for making insulative plugs to prevent chill marks.

Temperature controlled aluminum tooling Molds made with enclosed tubes buried within their surfaces that allow cooled or heated water or some other fluid to flow through them to control the temperature of the mold to within a few degrees Fahrenheit. Tensile strength

The pulling force required to stretch or break a given material. This value is usually expressed in pounds per square inch. (Continued on page 115)

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Texture (grain)

The pattern embedded into the surface area of a sheet or part.

Transmitted through

The condition where radiant energy given off an emitter goes through the object it is hitting rather than being absorbed or reflected off of that object.

Thermal conductivity

The amount of heat in BTUs which can be conducted through one square foot of any material one inch in thickness, in one hour, with one degree Fahrenheit temperature differential across the thickness (Btu/hr/ft2/F/in.).

Thermal expansion (Coefficient of) The fractional change in length (or volume) a one inch object will expanded or contract with a one degree Fahrenheit change in temperature. In ABS this value is approximately 5 x 10-5 per inch per one degree Fahrenheit change in temperature. Thermoforming

A system of changing a flat sheet of plastic into a desired shape.

Thermolator system A mechanical device that is used to regulate that temperature of a fluid that is subsequently pumped through heating or cooling lines embedded in a mold to control the mold temperature. Thinning

The process of taking a finite area of a hot sheet of plastic and stretching it over a protrusion or cavity of a larger area and distributing the plastic over this larger area as best as possible.

Tolerances

The maximum and minimum dimensions that are required to allow a formed part to be functional.

TPO

Thermoplastic olefin. Essentially it is a polypropylene blended with and EPDM rubber.

Trim

The excess material around a formed part that is not part of the finished product. This material is used for clamping or sealing purposes during the forming process. (Continued on page 116)

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Undercuts

Those indentations or extensions from a formed part that prevent the part from being removed from the mold without providing some type of movable mechanism on the mold itself.

Unistrut

A U-shaped channel with a clamping bar inside of it that can be adjusted very quickly by sliding the clamping bar in either direction of the channel.

UV resistant

The condition whereby a material, in this case plastic, will resist loosing its physical properties when exposed to the ultra-violet rays of the sun.

Vacuum

The absence of atmospheric gas within some given system.

Vacuum box

A five-sided structure on which a heated plastic sheet can be draped over the sixth side and a partial vacuum drawn within the box to form an inverted bubble.

Vacuum forming

A method of using vacuum to force heated plastic against a mold surface.

Vacuum forming techniques The various sequence of procedures one can use to shape a heated sheet of plastic to the configuration of a mold. Vacuum holes

The holes in a mold which air can pass through to allow the atmospheric pressure to force the hot plastic sheet against the mold.

Vacuum seal

The edge around a mold base that the heated plastic sheet is pressed against to allow a vacuum to be drawn and force the heated sheet against the mold.

Vacuum system

The mechanism whereby air is removed from an enclosed chamber to create a vacuum.

Vacuum volume

The size of the enclosed system in which the vacuum is employed. It also refers to the level of vacuum that is maintained within the system. Generally a large (Continued on page 117)

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vacuum holding tank is employed to keep the inches of vacuum from being drawn down to low. Voids

Small areas within a plastic matrix that have gas pockets instead of the solid plastic material that should be there.

Volume resistivity

The resistance of an electrical charge flowing through the solid structure of the material, in this case plastic.

Warping

The condition whereby a part is dimensionally distorted from its originally formed shape.

Wavelength

The distance measured from a point on an electromagnetic wave to the same point on the wave as it repeats its phase.

Wavelength of energy A measure of the type of energy given from various wavelengths of the electromagnetic spectrum. In plastics we are concerned with the infrared wavelength band of about .7 microns to about 100 microns. Weatherable plastics Those plastics that are resistant to physical degrading when exposed to the ultra-violet rays of the sun. Weatherability

The ability of a material to resist loosing its physical properties when exposed to sunlight.

Webs

Excess plastic material that is doubled up on itself and does not flow uniformly against a mold. It usually occurs on the corners of parts with small radii.

Wood tooling

Molds made of wood that are usually used to make prototype parts.

Yield point

That point of stress or strain which if reached will not allow the material to recover to its original shape. Its elasticity has been exceeded.

Zones

Those areas in a heating oven that the temperature is controlled independently from other areas.

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REFERENCES 1.

ILLIG Thermoforming - A practical Guide by: Günter Kiefer/Peter Schwarzmann

2.

Operating Manual for ILLIG RV 53b Machine- no. 593 EN/04.04-2 edition

3.

Textbooks from SPDC

4.

Various Thermoforming & Vacuum Forming websites from the internet

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Thermoforming Workbook Draft

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