PRACTICAL
`THERMOFORMING
`PRINCIPLES AND APPLICATIONS
`
`Taylor & Francis Group
`
`SECOND EDITION, REVISED AND EXPANDED
`
`CRCPress
`
`MacNeil Exhibit 2153
`Yita v. MacNeil IP, IPR2020-01139, Page 1
`
`

`

`PRACTICAL
`_ THERMOFORMING
`
`
`
`
`Yita v. MacNeil IP, IPR2020-01139, Page 2
`
`MacNeil Exhibit 2153
`
`MacNeil Exhibit 2153
`Yita v. MacNeil IP, IPR2020-01139, Page 2
`
`

`

`
`
`————=—=——_—_—____~ .—|
`
`Rubber C
`
`aes
`
`Defiant
`
`.
`
`Thermoplastic Polymer Additives:
`
`i
`
`I
`
`Barlow ompounding: Principles, Materials, and Techniques, Fred W.
`ies
`lymer Additives: Theory and Practice, edited by John T.
`Emulsion Polymer Technology, Robert D. Athey, Jr.
`Mixing in Polymer Processing, edited by Chris Rauwendaal
`Handbook of Polymer Synthesis, Part
`i
`Kricheldort
`’
`s A and B, edited by Hans R.
`
`y
`
`’
`
`t d b Joze! Bicerano
`
`a
`
`'
`
`erroelectric Polymers: Chemistry, Physi
`
`icati
`
`j
`
`7
`ee of Polymer Properties, Jozef Bicerano
`Hed Gieai leew
`ry,
`ysics, and Applications, edited by
`Degradable Polymers, Recycling, and Plasti
`by Ann-Christine Albertsson and SamuelJ. Huang
`amesbaa
`Pol
`is
`tics Waste M
`f
`A
`
`PLASTICS ENGINEERING
`
`Founding Editor
`
`Donald E. Hudgin
`
`Professor
`Clemson University
`Clemson, South Carolina
`
`20.
`
`21.—_
`
`22.
`23.
`24.
`
`25.
`26.
`
`27.
`28,
`
`29.
`
`30.
`31.
`
`32.
`33.
`34.
`
`35.
`
`36.
`
`37.
`
`38.
`
`39.
`
`Additional Volumesin Preparation
`
`T:
`
`t
`
`ki kK;
`
`gn of Pol meric
`
`ji
`
`i
`
`f
`
`Handbook of Thermoplastics, edited by Olagoke Olabisi
`
`lsayev
`
`Mallinson
`
`7
`
`
`
`edited
`
`Yita v. MacNeil IP, IPR2020-01139, Page 3
`
`MacNeil Exhibit 2153
`
`Polymer Toughening, edited by Charles B. Arends
`A
`Handbook of Applied Polymer Processin
`of
`g Technology,
`7
`P. Cheremisinoffand Paul N. Cheremisinoff
`ee aeroSy eo
`Diffusion in Polymers, edited by P. Neogi
`Polymer Devolatilization, edited by Ramon J. Albalak
`Ar‘aluc F ol merization F rinciples ar id F ractical Applicatior iS, Henry L.
`L
`y'
`uy
`i
`Cationic Polymerizations: Mechanisms, S
`edited by Krzysztof Matyjaszewski
`’
`Sees
`t
`:
`i
`nthesis, a
`icati
`Saag a teed mentals and Applications, edited by Malay K. Ghosh
`ba plastic Melt Rheology and Processing, A. V. Shenoy and D. R.
`Prediction of Polymer Properties: Second
`Editi
`i
`Jozef Bicerario
`Edition, Revised and Expanded,
`Practical Thermoforming: Princi
`icati
`Revised and Expanded, John Florian
`ee Se ESB
`>
`ples and Applicat
`iti
`:
`
`Polyimides: Funda
`
`Thermoplasti
`
`icati
`
`j
`
`i
`
`1. Plastics Waste: Recovery of Economic Value, Jacob Leidner
`2. Polyester Molding Compounds, Robert Bums
`3. Carbon Black-Polymer Composites: The Physics of Electrically Conduc-
`ting Composites, edited by Enid Keil Sichel
`;
`4. The Strength and Stiffness of Polymers, edited by Anagnostis E.
`Zachariades and Roger S. Porter
`;
`neering Applications, Charles P. Mac-
`5. Selecting Thermoplastics for Engi
`
`Dermott
`h Rigid PVC: Processability and Applications, edited by I.
`6. Engineering wit
`
`Luis Gomez
`omposites, D. H. Kaelble
`7. Computer-Aided Design of Polymers and C
`sites
`edited by James
`8. Engineering Thermoplastics: Properties and Applications,
`
`M. Margolis
`;
`9. Structural Foam: A Purchasing and Design Guide, Bruce C. Wendie
`10. Plastics in Architecture: A Guide to Acrylic and Polycarbonate, Ralph
`
`
`14,
`rties and Applications, edited by Swapan K.
`Montella
`Metal-Filled Polymers: Prope’
`
`Bhattacharya
`12. Plastics Technology Handbook, Manas Chanda and Salil K. Roy
`13. Reaction Injection Molding Machinery and Processes, F. Melvin Sweeney
`14. Practical Thermoforming: Principles and Applications, John Florian
`15.
`Injection and Compression Molding Fundamentals, edited by Avraam |.
`16. Polymer Mixing and Extrusion Technology, Nicholas P. Cheremisinotf
`;
`
`17. High Modulus Polymers: Approaches to Design and Development, edit
`by Anagnostis E. Zachariades and Roger S. Porter
`
`18. Corrosion-Resistant Plastic Composites in Chemical Plant Design, Johnt
`
`19. Handbook of Elastomers: New Developments and Technology,
`Anil K. Bhowmick and Howard L. Stephens
`
`MacNeil Exhibit 2153
`Yita v. MacNeil IP, IPR2020-01139, Page 3
`
`

`

`PRACTICAL
`THERMOFORMING
`PRINCIPLES AND APPLICATIONS
`SECOND EDITION, REVISED AND EXPANDED
`
`JOHN FLORIAN
`Consulting Design Engineer
`Bakersfield, California
`
`
`
`CRC Press
`Taylor & Francis Group
`Boca Raton London New York
`
`
`CRC Press is an imprint of the
`Taylor & Francis Group, an informa business
`
`Yita v. MacNeil IP, IPR2020-01139, Page 4
`
`MacNeil Exhibit 2153
`
`MacNeil Exhibit 2153
`Yita v. MacNeil IP, IPR2020-01139, Page 4
`
`

`

`CRC Press
`Taylor & Francis Group
`6000 Broken Sound Parkway NW,Suite 300
`Boca Raton, FL 33487-2742
`
`First issued in paperback 2019
`
`© 1996 byTaylor & Francis Group, LLC
`CRC Press is an imprint of Taylor & Francis Group, an Informa business
`Noclaim to original U.S. Governmentworks
`
`Preface to the Second Edition
`
`ISBN-13: 978-0-8247-9762-1 (hbk)
`ISBN-13: 978-0-367-40124-5 (pbk)
`This book contains information obtained from authentic and highly regarded sources. Reason-
`able efforts have been madeto publish reliable data and information, but the author and publisher
`cannot assumeresponsibility for the validity ofall materials or the consequencesof their use. The
`authors and publishers have attempted to trace the copyright holdersofall material reproduced in
`this publication and apologizeto copyright holders if permission to publish in this form has not
`been obtained. Ifany copyright material has not been acknowledged please write andlet us know so
`we may rectify in any future reprint.
`Except as permitted under U.S. Copyright Law, no partofthis book maybe reprinted, reproduced,
`transmitted,or utilized in any form by any electronic, mechanical, or other means, now knownor
`hereafter invented, including photocopying, microfilming, and recording, or in any information
`storage or retrieval system, without written permission from the publishers.
`For permission to photocopy or use material electronically from this work, please access www.
`copyright.com (http://www.copyright.com/) or contact the Copyright Clearance Center,
`Inc.
`(CCC), 222 Rosewood Drive, Danvers, MA 01923, 978-750-8400. CCCis a not-for-profit organiza-
`tion that provideslicenses and registration for a variety of users. For organizations that have been
`granted a photocopylicense by the CCC,a separate system ofpaymenthas been arranged.
`Trademark Notice: Product or corporate names may be trademarks or registered trademarks, and
`are used onlyforidentification and explanation withoutintent to infringe.
`Visit the Taylor & Francis Website at
`http://www.taylorandfrancis.com
`
`and the CRC Press Website at
`http://www.crcpress.com
`
`The rapid and accelerated growth of the thermoforming industry has not
`slowed despite the economicrecessionof the late 1980s and early 1990s. The
`economic downturn and environmental issues caused havoc, and unfortu-
`nately both entered into the business picture at the same time which had a
`devastating effect on some packaging manufacturers and suppliers. Among
`the hardest hit were thermoform product suppliers catering to high-volume
`‘de lines for fast-food packaging. Investment for new equipmentfor the
`nya aBay years experienced some weaknessas well. Despite theset-
`;
`» the t ermoforming industry has remained one of the fastest growing
`ueto its low initial investment requirements, superiorcycle repeatability, and
`adaptability to various product configurations.
`iss ee setback in productlosses in the fast-food areas were
`Aitke Alsa elequallyhigh-volume products. Such abrupt changes
`Keting he :
`may have caused some temporary oversupply and mar-
`— a a ners however, soon competitive forces leveled off. The
`rmotorming processors were not affected equally by the envi-
`i
`Tonmental
`Sean concerns or the general recession, which were regional, touching
`o
`as of the country more than others.
`.
`:
`oFal biehe outlookis bright, there is plenty ofopportunity for growth
`sire Kbtyet tate i myopinion, thermoformingmanufacturing methods
`
`a
`ed 50% oftheir growth potential. What was thought impos-
`
`Th
`
`iii
`
`MacNeil Exhibit 2153
`
`Yita v. MacNeil IP, IPR2020-01139, Page 5
`
`MacNeil Exhibit 2153
`Yita v. MacNeil IP, IPR2020-01139, Page 5
`
`

`

`iv
`
`Preface to the Second Edition
`
`Preface to the Second Edition
`
`v
`
`classes and seminars and at the University of Wisconsin—Madison.This wide
`range of experience has given me the opportunity to gain insight into the most
`pertinent and practical information on the thermoforming molding process
`This book coversit all, from the basic concepts to the latest innovations. The
`process methods described constitute fundamental techniques that suggest
`numerousvariations and combinationsfor the practical applicationof the ther-
`moformer. The book also contains comprehensive explanations andpossible
`causesof problems occurring during thermoforming.
`In this book,I left untouched the information that has not changed as
`well as the basic rules of the thermoforming process. I chose not to include
`brand and trade namesto avoid any commercialization. | mentioned a trade
`nameonly whena specific item is known solely by that name. I am confident
`that most makers and usersofthe materials and equipmentwill recognize their
`specific products, materials, equipment, and machinery, by either concept or
`function.
`One moretime, I would like to take this opportunity to thank my wife
`Judy, for her many yearsof understanding and support throughout my career.
`Patiently giving up her personaltime, she not only typed the manuscript but
`also helped shape the text to provide the clearest possible explanations that
`would be understandableto everyone, even those unfamiliar with the subject
`area. With God’s gracious help, we have accomplishedthis once again for the
`secondedition.
`
`sible to makein the past can easily be made today. Wecan only wonder what
`we will be able to produce in the future.
`The first edition of this book has been most successful. It is found on
`many thermoformers’ desks and is the foundation of my seminar programs.
`Theentirefield of thermoforming,including supportive and peripheralareas,
`is laid outfor the reader. To date,there is no bookonthis subject comparable
`in quality or detail. The few books that have been written on this subject either
`concentrate on a specific topic or give overwhelmingly complicated explana-
`tions of the technical concepts and includetheoretical formulasthat often do
`not produce real-life results.
`This second edition has been revised to update information that has
`changed since the first edition was published and expanded to incorporate
`subject areas that have come aboutsince and those that will be of greatest
`interest in the future. For example, I have covered theissue of plastics recy-
`cling, which in recent years has come into the spotlight. Recycling concerns
`must be addressed asthey will remain with us due to environmentalandleg-
`islative influences. Theywill affect all thermoformers as well as the end users
`of their products.
`The goalof the second edition remainsthe same:to provide the best and
`most detailed information, references, and guidance for the thermoformer,
`The uniqueness of my bookis thatit is written in a simple, easily comprehen-
`sible style and meets the needsof the widest range of people involved in the”
`
`thermoformingindustry, It is especially recommended for owners, managers,
`and design engineers,as they are the decision makers,as well as for newcomers
`
`to the industry. It could be used as a reference guide by practicing engineers,
`
`technicians, quality control and customer service personnel, equipment de-
`
`signers andbuilders, thermoplastic suppliers, sales and purchasing agents, and
`
`even thermoforming machine operating personnel.
`
`Theillustrations and tables in this book are prepared to emphasize only
`the concepts discussed. To achieve that, the figures of equipment and molds
`
`exclude all nonessential components not directly involved with the specifi
`
`explanation. Including all the necessary supporting, safety, and actuating
`
`mechanismsactually present would have madetheillustrations difficult to
`understand. The tables are also prepared with easy reading and referencing if
`
`mind.
`Overthirty-five years of involvement with the thermoforming process
`
`andits products has provided me with valuable knowledge and understanding
`
`of this manufacturing business. Working with many large and small firms
`balea a
`throughout North America, from Puerto Rico to Hawaii and Canada to Me x
`
`ico, I have encountered manydifferent manufacturing conditions, equipmem®
`
`variations, and technical challenges. In the last sixteen years I have been in
`
`volved with education—teaching the thermoformingprocess in various Pp ival
`
`John Florian
`
`Yita v. MacNeil IP, IPR2020-01139, Page 6
`
`MacNeil Exhibit 2153
`
`MacNeil Exhibit 2153
`Yita v. MacNeil IP, IPR2020-01139, Page 6
`
`

`

`
`
`Preface to the First Edition
`
`
`
`
`
`The thermoforming process has become oneofthe fastest growing plastics
`manufacturing methodssince the commercialization of thermoplastic materi-
`als dueto its superior adaptability, low initial investment, and excellent repeat-
`ing qualities, In just four decades, thermoformed goods have becomepart of
`many existing productlines. Thermoforming has completely replaced other
`
`processing techniques for some product lines and has even created new plastic
`
`product lines. Every year rapid developments and clever implementations of
`
`this manufacturing method allow it to compete with more established methods
`
`and to penetrate many new product categories. The possibilities for this indus-
`
`tty are extensive and the business opportunities within it are enormous.
`
`The rapid growth of the thermoforming industry and the keen competi-
`
`tiveness among thermoforming processors has kept many ofthe technical de-
`
`tails and developmentsandthe practical know-howinsecrecy.In recent years,
`
`with the crossover of personnel between companies, the flow of information
`hasincreased. Theliterature on thermoforming, however,still lags behind the
`
`industry's Projected boom, which hascreated the need for more education,
`Maining, and documentation.
`The thermoforming process can be used for material from the thinnest
`
`!
`I-gauge) to the thickest (heavy-gauge) material to manufacture products
`Om the Smallest to the largest possible size and to produce anywhere from
`mst
`a few pieces to an enormous quantity. Covering all the possible process
`
`
`
`
`
`vii
`
`MacNeil Exhibit 2153
`Yita v. MacNeil IP, IPR2020-01139, Page 7
`
`MacNeil Exhibit 2153
`Yita v. MacNeil IP, IPR2020-01139, Page 7
`
`

`

`viii
`
`Preface to the First Edition
`
`principleswithin a single workis therefore not an easy task. But, ofcourse, the
`similarities and overlapping process behaviorswithin these variations form an
`essential body of knowledgethatwill be of interest to all working in this field.
`The goalofthis bookisto provide information, references, and guidance
`on the thermoforming of thermoplastics in a simple and easily understood
`format. The book is intended to meet the needs of a wide range of people
`involved in thermoforming: business owners and managers, new and experi-
`enced engineers, product designers, quality control engineers and customer
`service personnel, equipment designers andbuilders, material and machinery
`suppliers, sales and purchasing agents, and the actual operating technicians.
`Theillustrations and tables for this book have been prepared to empha-
`size the basics. Theillustrations generally excludeall components that are not
`directly involved with the specific explanation in order to emphasizethe par-
`ticular thermoforming or equipmentfunctions. Underactual working condi-
`tions, with all supportive, safety and actuating mechanisms, these principles
`would not be so clearly illustrated. The tables are also prepared with easy
`reading and referencing in mind.
`Through my manyyears ofinvolvement with the thermoformingprocess,
`workingcloselywith manyhighly knowledgeable andskilled colleagues,I have
`gathered the knowledge and understanding ofthis process that have enabled
`me to complete this book. I would like to thank the many equipment and
`material suppliers who contributed information on their own products, ma-
`chinery, and instrumentation. Although specific brand and trade names have -
`been avoided throughout this book in order to minimize commercialization,
`
`their product concepts and functions are thoroughly represented and ex-
`
`
`plained here.
`1 wouldlike to thank Gerald Sitser for his help in editing and for
`
`filtering out my native language influences from this writing.
`
`Last but certainly notleast, I thank my devoted wife, Judy, for her tong,
`
`full understanding andtotal support throughoutmy career and forhertireless
`
`hours typing, proofreading, and reviewing this entire project, which took uf
`all of our extra time but, with God’s help, we werefinally able to complete. !
`
`also would like to thank the editors of Marcel Dekker, Inc., for their inte
`
`encouragement, and patience in working with me.
`
`
`
`
`
`John Flori
`
`
`
`
`Contents
`
`Preface to the Second Edition
`Preface to the First Edition
`
`1.
`
`Introduction -
`
`I. The Basic Concept of Thermoforming
`II. History of the Thermoforming Industry
`Ii.
`Products Made by Thermoforming
`IV. The Thermoforming Industry
`
`2. Components of the Thermoforming Process
`J. Thermoplastic Sheets
`Il. Clamping Mechanisms
`Ill. Heating Systems
`IV. Molds
`V.
`Forming Forces
`VI. Trimming
`i. Thermoforming Methods
`7 - f Basic Forming Techniques
`- Thermoforming Methods
`
`a
`.
`
`1
`
`1
`2
`6
`11
`
`13
`13
`46
`54
`#9
`99
`119
`119
`135
`
`ix
`
`MacNeil Exhibit 2153
`.
`Yita v. MacNeil IP, IPR2020-01139, Page 8
`
`MacNeil Exhibit 2153
`Yita v. MacNeil IP, IPR2020-01139, Page 8
`
`

`

`1 I
`
`ntroduction
`
`1. THE BASIC CONCEPT OF THERMOFORMING
`
`The thermoforming process is only one of many manufacturing methodsthat
`converts plastic resin material into numerous products. Yet in our modern
`life-style, we are coming to rely more and more on the benefits of thermo-
`forming and make extensive use of plastic products produced by this process.
`Thermoformingis the amalgamated description of the various thermo-
`plastic sheet-forming techniques, such as vacuum forming, pressure forming,
`matched mold forming, and their combinations. All of these forming tech-
`niques require a premanufactured thermoplastic sheet, which is clamped,heated,
`and shapedinto or over a mold. Products made by this process are generally
`finished after the trimming operation and are ready to be used. However, some
`thermoformed products are designed as componentsoflarger items, such as
`boats,aircraft, automobiles, or even smalleritems such as productdisplay trays.
`These parts may require additional workafter trimming, such as painting, print-
`ing, heat sealing, and gluing.
`The thermoforming process offers fast and uniform forming and there-
`fore lendsitself to automation and long-term production runs. With its rela-
`tively fast molding cycles and comparatively inexpensive mold costs, the ther-
`moforming process is often chosen as the mostcost-effective manufacturing
`method over all the other processes. The scrap created by the normal edge
`
`1
`
`Yita v. MacNeil IP, IPR2020-01139, Page 9
`
`MacNeil Exhibit 2153
`
`Typical Mold Arrangements
`(Il.
`IV. Limitations in Thermoforming
`
`4. Thermoforming Machines
`
`Introduction
`I.
`Sheet-Fed Thermoforming Equipment
`Il.
`III. Web-Fed Thermoforming Equipment
`IV. Corrugated Plastic Tubing and Pipe Machines
`
`5. Molds for Thermoforming
`
`I. The Basic Concept of Molds
`Il. Mold Temperature Controls
`IN.
`Special Molds
`IV. Common Mold Errors
`
`6. Economics of Thermoforming
`
`Introduction
`I.
`II, Thermoplastic Sheets
`HI. Quality Control
`TV. Equipment Purchases
`Vv. Cost and Financial Factors
`VI.
`Peripheral Factors in the Thermoforming Process
`VII. Troubleshooting
`
`7. The Human Element in Thermoforming
`
`Glossary
`Bibliography
`Index
`
`Contents
`
`164
`174
`
`183
`
`183
`186
`212
`262
`
`267
`
`267
`293
`305
`313
`
`371
`
`379
`385
`387
`
`MacNeil Exhibit 2153
`Yita v. MacNeil IP, IPR2020-01139, Page 9
`
`

`

`
`
`
`A. Preforming Sheet Behavior
`To form a thermoplastic sheetinto a final product shape, the sheet has to be
`held by all four sides. The captured thermoplastic sheet is then exposed to
`heat, softeningit and makingit stretchable for the shaping. The actual forming
`of the thermoplastic sheetis almost always madeby subjecting the heated sheet
`to the forming forces. After the forming, residual heat is removed from the
`formedpart,setting it into a permanent shape. With these steps, the forming
`cycle is considered complete.
`The heating cycle begins as the secured thermoplastic sheet is exposed
`to the heating apparatus discussed previously. There is no difference in the
`reaction to heating between the precut sheet or rolled material forms. The
`plastic material will react the same way in both cases, provided that the mate-
`rial source and thickness and exposed sheetpanelsizes match.Naturally, sheet
`materials from different sources can be comparedonlyif their raw resin type
`and sheet manufacturing techniquesare the same.A calenderedsheetwill not
`react the same wayas extrudedorcast sheet materials evenif they are made
`of the sameresins. On the other hand,resins having the same chemical com-
`position but different manufacturing sources and different polymerizations
`may not behavein the same way. Theoretically, the same thermoplastic mate-
`rials produced in the same mannerinto sheet form should provideidentical
`119
`
`Thermoforming Methods
`
`I. BASIC FORMING TECHNIQUES
`
`‘|
`
`Yita v. MacNeil IP, IPR2020-01139, Page 10
`
`MacNeil Exhibit 2153
`
`MacNeil Exhibit 2153
`Yita v. MacNeil IP, IPR2020-01139, Page 10
`
`

`

`behavior in the heating and forming process. Such similarities orslight differ.
`encescan only be pinpointed by experts.In all cases, a comparative study mug
`be made and analyzed for choosing the mostideal thermoforming condition,
`A thermoplastic sheet placed into a thermoforming machinewill provide q
`consistent sequence ofclues as to its behavior in the heating process. Most
`thermoforming practitioners fail to observe the behavior changes that take
`place in a sheetasit is being heated but beforean actualsagis noticed. Between
`the time of the cold sheet exposure andthe resulting sag, there are changesin
`the sheet that can be observed. Such changesare not necessarily slow and
`obvious; often, they occur in just a fraction of a second. The rapid changes
`could take place so quickly,in fact, that even with the bestskills of observation,
`they may pass unnoticed. Thatis the reason that for most thermoformers, the
`———————FF
`first clue to the change is sagging of the sheet. The sheet’s response to heatis
`mostlikely to follow the sequence shownin Figure 36.
`1. The cold thermoplastic sheetis placed into a sheet-holding apparatus
`andits exposure to heat begins.
`2. As soon as the plastic is exposed to the heat, various temperature
`levels are created within the plastic and the first changes can be observed. Due
`to a higher temperatureonits surface thanin its inner core and possible tem-
`perature variations on the surfaceitself, the partially heated plastic will go
`through a wavelike movement. This movementclosely resemblesa ripple spread-
`ing across the surface of a body of water. The reactionof the plastic sheet to
`the heat may comein such pronouncedlevels that the sheet shows an imme-
`diate but temporary sag. The sag rapidly disappears with further heating. This
`temporary condition should not be confused with materials displaying an im-
`mediate and permanentsag condition, which are discussed in a later section.
`It is possible that thermoplastic sheet materials will react only minimally to
`heat. In reacting to heat, some thermoplastic sheets never display anything as
`definedasa ripple-like expansion movement; they may showonlya slight color
`or surface sheen change. Someplastics provide such subtle clues as gaining
`moreclarity or getting either shinier or duller. Either way, a changewill take
`place that can be observed and recognized.
`3. As the sheetis further exposedto theheat, its normal reaction causes
`it to tighten up. This tightening gives the sheet the appearance ofwell-stretched-
`out material, almost like the skin surface of a drum.In this state, knowledge
`of the changing temperature conditionsis vital to successful heating.
`4. During the heating cycle a definite sag will appearin the heated sheet.
`Atthis point, the plastic will be heated and softened to the point whereits
`self-supportiveness is reduced andthe sheetwill yield to gravity. Actually, the
`softened plastic can no longer support its own weight and will stretch out of
`its original shape, creating a sag. The sag is a well-defined change in plastic
`
`to heat. With manyplastics, this is somewhattrue.If the plastic sheet does not
`have any orientation—orevenif it does butits weight, due to its gauge or panel
`size, cannothold itself up—a sag will develop. This maybethefirst observable
`reaction in the sheet when exposed to heat. Many thermoformers automat-
`ically use sag as the indicator for readiness of the thermoforming process,
`althoughthisis not a completely reliable method. Some thermoforming equip-
`mentbuilders even offer an electric-eye sensing device whichwill trigger an
`automatic forming cycle as soon as sag interrupts the light signals.
`
`Figure 36 Thermoplastic sheet behaviorin heating: (1) clamped cold sheet;(2) rippl-
`ing reaction to heat; (3) heat-tightening sheet; (4) sagging sheet; (5) overheatedsheet.
`
`Yita v. MacNeil IP, IPR2020-01139, Page 11
`
`MacNeil Exhibit 2153
`
`
`
`120
`
`Chapter3
`
`i—-——___________I-
`
`121
`
`behavior, and being so noticeable, most people recognizeit as the first reaction Thermoforming Methods
`
`MacNeil Exhibit 2153
`Yita v. MacNeil IP, IPR2020-01139, Page 11
`
`

`

`122
`
`Chapter 3
`
`A heated sheet that develops sag is not necessarily unusable. However,
`in mostinstances, sag should be avoided if possible. Using sag as an indicator
`of readiness for thermoforming is only slightly better than using measured
`time. The developmentof sag in the heated sheet will obviously be a more
`accurate indicator than the use of timers, which are completely unaffected by
`ambient and sheet temperature changes. For example, a manufacturing area
`could have wide temperaturevariations between the early morning andafter-
`noon hours and evengreater temperature changes between the day- and night-
`shift hours. If this is the situation,it is easy to see why sag would be a better
`indicator than timerunits.
`Developing sag in a sheet and using it for prestretching of the sheetis
`also acceptable.This is a commonpractice in moldless thermoforming orwhen
`deeper, well-tapered cavity shapes are formed.In fact, the use of developing
`sag will help to achieve better wall thickness distributions than its nonuse.
`Controlling the developmentandsize of the sag is not an easy task, Allowing
`sag to developin the heated thermoplastic sheet for thermoforming may not
`prove to be advantageousatall. Creating a predeterminedsag size, no more
`and noless, is one of the mostdifficult procedures. Since the sag is produced
`by the weightofthe plastic sheet, it is an ongoing, continuous process, At the
`point where the sagis judged to be of correct size,it is still expanding andwill
`rapidly stretch outof control. At the sametime,the plastic may notbe stretch-
`ing evenly, resulting in a nonidentical bulge shape, hindering uniformity in the
`shot-to-shot process.
`More important, and to the dismay of thermoformers, the developing
`sag in the plastic sheetalters the distance between the heated sheet and the
`heater units. Such a changein a given distance, especially when the sagging
`sheet drops closer to its center to the bottom heater element,will prove to be
`detrimental. This could cause runaway heating of the plastic, and the over-
`heatingwill accelerate greatly as the sheet comescloser and closerto the heater
`units. It is easy to see that a fraction of a momenton the timing controls may
`mean the difference between forming success and forming failure, In more
`cases, a sagging plastic sheetwill be hotter than is necessary for forming and
`shaping.
`5. Of course, the plastic sheet can be so neglected thatit will reach the
`point wherethe sag radically overdevelops and the sheet melts and flows apart,
`makingit no longer useful for thermoforming. At this point, not only is the
`thermoplastic sheetlost in the overheating, but the molten plastic canfall into
`the heater elements and resultin fire. By no means should neglect of the heated
`sheet continue this long. Most thermoplastic materials derived from petro-
`chemical andfossil-fuel sources, when exposed to extremeheat, will constitute
`a potential fire hazard. Precautions should be incorporated in thermoforming
`equipment which enablesit to preventignition of the plastic material, or even
`
`Thermoforming Methods
`
`123
`
`to put out the resultantfire. More important, these precautions should include
`good control of the sag and perhaps even its completeelimination.
`Thermoplastic sheet materials used in the thermoforming process to
`makevarious products are produced from different types of resins and in a
`multitude ofgauges and sheetsizes. Their reaction to heatisjust as wide rang-
`ing as their sources and forms. Some materials demand the mostprecise con-
`trol range in which to perform and not get ruined, while others are especially
`“lenient”regarding overheating. Such differences, shown in Figure 37, should
`be recognized and, when known,well respected. For example, biaxially ori-
`ented polystyrene sheets display one of the most narrow heat ranges between
`the formability temperature andtheloss of orientation, which comes aboutat
`the slightest overheating points. When high-impact polystyrenes (HIPS) and
`acrylonitrile-butadiene styrene (ABS)plastic sheets are heated, substantial
`overheating is possible without damage to the plastic. Working continuously
`with the various materials, thermoformingpractitioners will soon discover the
`specific sensitivity and “criteria windows”of the individualplastic sheets, as
`well as their behavior underdifferent heat ranges. Knowing where the data
`mayfall on the chart will help to achieve the most advantageous forming con-
`ditions. Each time a change is encounteredin thickness,color, resin material,
`heaters, or even ambient temperature, the reaction to heat will be altered.
`
`
`
`B. Moldless Forming
`
`Thermoforming a bowl or dome shape can be accomplished quite easily. In
`fact, such shapes can be obtained easily without the use of a mold. There are
`two basic ways to form the plastic moldlessly. The first and less complicated
`way consists of producing a sag in the clamped sheet. When a bowllike shape
`is approaching the desiredsize, it should immediately be removed from the
`heat source, for cooling. This allows the weight of the heated plastic sheet to
`form andstretch it. With this method, producing a bow! shape will take the
`longest time and the shape produced will never have a uniform curvature.
`Since the bowl shapeis the result of a sag that may produce unevenstretching
`of the sheet, the curvature of the bowl shape mayresult in inconsistent place-
`mentof the center point. Thesevariations in shape are easily found from one
`part to the next, giving the producta poornesting quality.
`The second way to produce bowl- or dome-shaped configurations with-
`out moldsis to build equipmentthat resembles a pressure box. Oneofthe walls
`of the box is actually formed by the clamped and heated plastic sheet. When
`the plastic sheet starts to show somesoftening, the box should beinternally
`pressurized. Thepressurewill force the softened sheet to bulge upward to form
`a domeshape.At low levels of pressure, the softened plastic can be kept from
`sagging and thusheld straight andflat. As the pressurelevelis increased, bulging
`
`Yita v. MacNeil IP, IPR2020-01139, Page 12
`
`MacNeil Exhibit 2153
`
`
`
`MacNeil Exhibit 2153
`Yita v. MacNeil IP, IPR2020-01139, Page 12
`
`

`

`
`
`
`
`
`
`Figure37Thermoformabilityheatrangechart.NotethenarrowformabilityrangeofOPSandthewider
`
`
`
`
`
`
`
`Chapter 3
`
`
`
`
`
`125
`
`Thermoforming Methods
`
`
`
`
`|
`|
`
`will appear; as the pressureis increased further, the size of the bulge will in-
`crease accordingly. With the force from the air pressure, the plastic will stretch
`and form into a domelike shape. Whenthe desired shapeis reached,further
`heating andanyincreasein pressurization must cease. Consequentcoolingwill
`take placeor,if desired, fan-forced cooling can be introduced to set the newly
`acquired shape into a permanent form. Forming domeswith this method of
`pressurized air is much more rapid than producing them by sag, and the com-
`parative shapes are more uniform.It is well known that this type of forming,
`despite improved qualities, will never produce as uniform a shape as would a
`mold. However,for the purposeofspecific products,this type of forming tech-
`nique is well accepte