Thermoforming Workbook Draft

Click here to load reader

  • date post

    24-Oct-2014
  • Category

    Documents

  • view

    277
  • download

    17

Embed Size (px)

Transcript of Thermoforming Workbook Draft

Higher Institute for Plastics Fabrication

WORKBOOKfor

Thermoforming Practical Course

Prepared by

Thermoforming Department 1st Edition 2009Page 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). Calpe. Editing, formatting and design by Virgilio

April 2009

Page 2

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

TABLE OF CONTENTSIntroduction . Course Objectives . Grades Summary Sheet ... Workshop Activities Activity 1Introduction Basic Principles of Thermoforming .. Activity 2Thermoforming General Safety Instructions . Activity 3Materials and Their Applications ... Activity 4The Thermoforming Machine and Mold . Activity 5Thermoforming Methods & Processes Activity 6Manpower and Standard Operating Procedures Activity 7Product Quality, Defects and Troubleshooting .. Activity 8Handson and Practical Training (1) ... Activity 9Handson and Practical Training (2) . Activity 10Handson and Practical Training (3) Glossary . References ... 7 16 30 40 53 64 74 83 89 95 101 118 4 5 6

Page 3

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

INTRODUCTIONAs 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.

Page 4

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

COURSE OBJECTIVESThe 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. theories and practices of

To operate the Thermoforming machine safely and appropriately.

Page 5

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

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

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

GRADE

Page 6

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 ThermoformingTHEORETICAL BACKGROUNDIn 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 RollThe 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. HeatingThe 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 eWORKSHOP ACTIVITY #1Introduction: Basic Principles of Thermoforming

Theoretical Background continued 4. CuttingThe molded product is separated from the runner or skeleton 5. StackingThe product is collected in a stack and then ejected to the conveyor for packing 6. Winding of skeletonThe 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.

Page 8

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 eWORKSHOP ACTIVITY #1Introduction: Basic Principles of Thermoforming

Theoretical Background continued

Page 9

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 eWORKSHOP ACTIVITY #1Introduction: Basic Principles of Thermoforming

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 ProcessThe oldest and cheapest process in terms of equipment cost. 2. Pressure Forming ProcessThe 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 ProcessFor 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.

Page 10

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 eWORKSHOP ACTIVITY #1Introduction: Basic Principles of Thermoforming

OBJECTIVES OF THE ACTIVITY1. To learn the basics of the Thermoforming processes 2. To identify the main parts of Thermoforming machine and their functions

PROCEDUREPART IThe 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 observa