Contents A NOTE TO PROSPECTIVE Thermoforming® Q U A R T E R L Y AUTHORS TECHNICAL SECTION TFQ is an “equal opportunity” publisher! You will note that we have Lead Technical Article: several categories of technical articles, A Solution for Warpage in Polymeric Products by Plug-Assist Thermoforming ...... 9 ranging from the super-high tech (sometimes with equations!), to Industry Practice: industry practice articles, to book How Much Data is Enough? ...... 14 reviews, how to articles, tutorial Industry Practice: articles, and so on. Got an article that doesn’t seem to fit in these categories? IR Scanning With Closed-Loop Feedback for Thin-Gauge Thermoforming ...... 16 Send it to Jim Throne, Technical Editor, Thermoforming 101: anyway. He’ll fit it in! He promises. [By The Cutting Edge ...... 19 the way, if you are submitting an article, Jim would appreciate it on Book Review: CD-ROM in DOC format. All graphs Mathematical Modeling for Polymer Processing: Polymerization, Crystallization, and photos should be black and white Manufacturing ...... 20 and of sufficient size and contrast to be scannable. Thanks.] DIVISION ACTIVITIES
Chairman’s Corner ...... Inside Front Cover Thermoforming® QUARTERLY Membership: Strength in Numbers ...... 2 A JOURNAL PUBLISHED EACH CALENDAR New Members ...... 3 QUARTER BY THE THERMOFORMING DIVISION 2006 Scholarship Winners ...... 4 OF THE SOCIETY OF PLASTICS ENGINEERS Fall Board Meeting Schedule ...... 8 Editor Council Report ...... 22 Gwen Mathis Salute to Glenn Blackburn ...... 28 (706) 235-9298 • Fax (706) 295-4276 [email protected] Thermoforming With Style ...... 30 Membership Application ...... 33 Technical Editor Index of Sponsors ...... 36 Dr. James Throne Sherwood Technologies, Inc. Board of Directors List...... Inside Back Cover 1797 Santa Barbara Drive Dunedin, FL 34698-3347 These sponsors enable us to publish Thermoforming QUARTERLY 1-800-273-6370 • Fax (727) 734-5081 [email protected] [email protected] Sponsorships Laura Pichon (815) 678-2131 Ext. 624 Fax (815) 678-4248 [email protected] Thermoforming Quarterly® is published four times an- nually as an informational and educational bulletin to the members of the Society of Plastics Engineers, Thermoforming Division, and the thermoforming industry. The name, “Thermoforming Quarterly®” and its logotype, are registered trade- marks of the Thermoforming Division of the Society of Plastics Engineers, Inc. No part of this publication may be reproduced in any form or by any means without prior written permission of the publisher, copyright holder. Opinions of the authors are their own, and the publishers cannot be held responsible for opinions or representations of any unsolicited material. Printed in the U.S.A. Thermoforming Quarterly® is registered in the US Patent and Trademark Office (Registration no. 2,229,747).
1 Thermoforming QUARTERLY MEMBERSHIP STRENGTH IN NUMBERS
BY CONOR CARLIN, MEMBERSHIP CHAIRMAN s the new membership knowledge that is shared. In addition to the benefits Achairman, I would like From conference centers in you receive as a member, to recognize the efforts of Nashville to congress halls in you are also encouraged to Mike Sirotnak over the past Salzburg, the wealth and contribute. We receive decade. During Mike’s breadth of thermoforming technical articles from tenure, the SPE Thermo- skills and techniques on universities in Europe as forming Division has display allows me to learn well as industry practice become one of the most something new every time. articles from seasoned successful divisions formers. Your feed- within SPE. Our group MEMBERSHIP REPORT back on the contents has steadily grown as of 6/1/06 of the Thermoforming over the years and is Quarterly are impor- renowned for having tant to the magazine’s members from a Primary Paid ...... 1,704 continued success. variety of industries. Secondary Paid ...... 541 In recent times, we It is my hope to have expanded our Total Membership ...... 2,245 build on the strong efforts to recruit Goal as of 6/30/2007 ...... 2,500 foundation left by members from our Mike. Just looking at burgeoning European the new members every Division and also to fill our When you participate as an quarter is an inspiration as ranks with the brightest SPE member, you are joining we continue to welcome minds from university the ranks of the experts. people from around the programs. Polymer scientists, process country and around the engineers, old sales hands globe. We are creating our I joined the SPE Thermo- and company executives are own worldwide network forming Division in 2000 and all in attendance at the and I am proud to be a part through every conference, annual conference. There is of it. I invite you to come and meeting and seminar I have no better place to take the join us. ■ attended, I am constantly pulse of our thermoforming impressed by the amount of industry.
Thermoforming QUARTERLY 2 WHY JOIN?
It has never been more important to be a To Our New Members member of your Jay Abbott Olivier C. Chris J. Hendryk John W. Meriton professional society Display Pack, Inc. Coquerel Plastic Package, DuPont Australia Grand Rapids, MI ABB Australia Pty Inc. Richmond, than now, in the Ltd. Australia Phillip J. Asker Sacramento, CA Victoria, Australia Vitasheet Group Ming L. Ho Michael Pastelak current climate of United Kingdom Chandrakant Pactiv AAI Corporation Doshi Corporation Hunt Valley, MD change and volatility Donald E. Bailey Rajoo Engineers Canandalgua, NY Sun Tech Parimal K. Patel Limited Fremont, CA in the plastics industry. Tuscaloosa, AL Veraval, India Marcus Holden Evans, CO Meng Y. Pun Bruce Belhoff Now, more than ever, Duane DeJong Texchem Whirlpool Daigo Ishiyama Display Pack Polymerds Sdn Corporation American Grand Rapids, MI Bhd. the information you Benton Harbor, Standard Fernando Moura Prai, Malaysia MI Piscataway, NJ access and the Duarte Brenda S. Phillip M. Timothy J. University of Richmond Jandrow personal networks you Bertrand Minho Printpack, Inc. Tripod Data Nike IHM, Inc. Guimaraes, Williamsburg, VA St. Charles, MO Portugal Systems create can and will Corvallis, OR Dennis Shimmell Lamar A. Bost John L. Durfey Corvac directly impact your Spartech Plastics Dekalb, IL Mark Kishel Composites Warsaw, IN Debra Gilmour Arrowhead Bryon Center, MI future and your career. Plastics Lou Calistro American Tony Straub Products Jetta Corporation Standard Mercury Marine Eaton, IN Edmond, OK Ontario, Canada Fond Du Lac, WI Randall K. Loga Active membership Adam Clark Thomas A. Goates Ron Starnes Tek Packaging Display Pack, Inc. Baxter Health Alto in SPE: Huntley, IL Grand Rapids, MI Corporation Albany, New Mountain Home, Dan P. Longhenry • keeps you current Dakheel Al Zealand AZ Tennant Company Dakheel Bayne Upton Laurence Golden Valley, • keeps you informed Kuwait Packing GE Healthcare Goddard MN Materials Co. Waukesha, WI Bonar Plastics • keeps you connected Safat, Kuwait Jean Christophe Ontario, Canada Cory S. White Mercier Mike E. Carley GN Plastics Co. Luke Gross Durand JSP Ltd. Mullinix Maquinaria New Baltimore, Chester, NS, The question really isn’t Packages, Inc. Envapac SA De MI Canada Fort Wayne, IN CV “why join?” but … Bob Whitish Leon R. Cole Robert Guldi Ed, Mexico GAFMC Plastics Ingenuity, Stryker Pamela Marks Inc. Wayne, NJ Instruments Sumitomo Cross Plains, WI Randy Cook Kalamazoo, MI WHY Corporation of Edward G. Wolk Caro, MI Paul Harris America Hampel TriEnda Houston, TX Corporation NOT? Portage, IN Germantown, WI
3 Thermoforming QUARTERLY 2006 SCHOLARSHIP WINNERS
SEGAN MEMORIAL thermoforming industry after graduation cluded modifying an old lab-scale SCHOLARSHIP while simultaneously working on a Mas- thermoformer, developing lab protocols ters of Business Administration. and research objectives, and making thou- LUCUS D. STALLBAUMER sands of test runs to develop the deep draw Pittsburg State University PAUL BERTSCH foam sheet process. The University of Washington plans to patent the process. Pittsburg, Kansas MEMORIAL SCHOLARSHIPS ADRIANE R. WILTSE Lucas Stallbaumer KURTIS J. SCHULTZ Pittsburg State University will be a graduate stu- Western Washington University dent in Plastics Engi- Pittsburg, Kansas Auburn, Washington neering Technology at Pittsburg State Univer- Kurtis Schultz will Adriane Wiltse will sity this fall. A mem- be a senior at Western be a senior at Pitts- ber of SPE, Lucas at- Washington University burgh State University tended ANTEC 2004, this fall working to- this fall, majoring in the 2005 Thermo- ward a B.S. in Plastics Plastics Engineering forming Conference, Engineering Technol- Technology with an and was featured in a Plastics Engineer- ogy. A member of the emphasis in manufac- ing magazine article on mentorship as a Phi Theta Kappa turing. Her interest in result of his internship with Joe Peters, Honor Society, Kurtis plastics was sparked, President of Universal Plastics. At Univer- is also a SPE member at age 11, by encour- sal Plastics, Lucas experienced all kinds and was the recipient of a scholarship from agement from a cousin who was graduat- of thermoforming applications and was the SPE Foundation last year. Kurtis held ing from PSU as a plastics engineer. charged with designing a package with an internship in the summer of 2004 at Adriane, too, decided to attend PSU where holes in the bottom so that it still contained Northwest Kayaks, where he used the she is a member of Student Government physical strength and durability. After thermoforming process for bulkheads, Association, University Ambassadors, and graduation, Lucas would like to work in hatch covers, and protective nose covers is currently serving as the president of SPE the automotive industry. for kayaks. His senior project is to develop Student Chapter at PSU. Adriane spoke at a thermoformed kayak seat/support system the 2004 Thermoforming Conference and for people who have restricted use of their attended the 2005 Conference. She has also GRIEP MEMORIAL lower extremities (paraplegics, amputees, worked as a General Plastics laboratory SCHOLARSHIP or those otherwise injured). Kurtis was also assistant, introducing freshman students to instrumental in writing a grant proposal on the Plastics Engineering Technology pro- KIM C. ACINGER behalf of the WWU Engineering Technol- gram at the university. After graduation, Pittsburg State University ogy Program for the Thermoforming Adriane hopes to work in the Pittsburg, Kansas Equipment Grant. thermoforming industry. Kim Acinger will JUSTIN J. DAMERON be a senior at Pittsburg STEPHEN M. PROBERT Pittsburg State University State University work- University of Washington Pittsburg, Kansas ing toward a B.S. in Woodinville, Washington Plastics Engineering Justin Dameron Technology with a mi- Stephen Probert will be a senior at nor in Manufacturing will be a graduate stu- Pittsburg State Univer- Management. She had dent in Mechanical sity working toward a an internship in the Engineering at the B.S. in Plastics Engi- summer of 2005 at University of Wash- neering Technology. Nike IHM in St. Charles, MO working pri- ington this fall. An He had an internship in marily in the thermoforming department, honors student, he is the summer of 2004 at processing twin-sheet. She plans to return also active in the UW Charloma, Inc. work- to Nike this summer for a second intern- Karate Club, the UW ing primarily with ship, doing project work in thermoforming. Yacht Club and the thermoforming machines. An active mem- She also interned in 2004 at Sika Corp. of Campus Crusade for Christ. Stephen’s un- ber of the SPE Student Chapter at PSU, Grandview, MO doing insert molding in dergraduate research was a “cup project” Justin attends many local Section meetings the injection molding division. Kim has – a successful attempt to thermoform a and has participated in a large number of been a lab assistant at PSU since Fall 2005 microcellular foamed coffee cup from re- plant tours to familiarize himself with all demonstrating thermoforming, extrusion, cycled bottles. The experience of aspects of plastics processing. Justin’s fu- compression, injection and blow molding, thermoforming a material that has not been ture plans include marriage to a fellow PSU as well as testing equipment such as commercially thermoformed will now be student this fall and a career in a Instron, Izod, DSC, and Melt Flow Index. incorporated into Stephen’s graduate re- thermoforming or rotational molding pro- She plans to pursue a career in the search. His work at MicroGREEN Inc. in- cessing plant upon graduation.
Thermoforming QUARTERLY 4 These sponsors enable us to publish Thermoforming QUARTERLY Need help with your technical school or college expenses?
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5 Thermoforming QUARTERLY THERMOFORMER OF THE YEAR CRITERIA FOR 2007
very year The SPE Thermo- ➢Has made a significant educa- Thermoforming Division Awards Eforming Division selects a indi- tional contribution to the Committee vidual who has made a outstand- Thermoforming Industry. % Productive Plastics, Inc. ing contribution to our industry and If you would like to bring some- Hal Gilham awards them the Thermoformer of one who meets some or all of these 103 West Park Drive the Year award. requirements to the attention of the Mt. Laurel, NJ 08045 The award in the past has gone Thermoforming Division, please fill Tel: 856-778-4300 to industry pioneers like Bo Stratton out a nomination form and a one- Fax: 856-234-3310 and Sam Shapiro, who were among to two-page biography and forward Email: the first to found thermoforming it to: [email protected] companies and develop our indus- try. We have included machine de- signers and builders Gaylord Brown You can also find the form and see all the past and Robert Butzko and toolmaker John Greip, individuals who helped winners at www.thermoformingdivision.com in develop the equipment and mold the Thermoformer of the Year section. ideas we all use today. We have also honored engineers like Lew Blanchard and Stephen Sweig, who You can submit nominations and bios at any time developed and patented new meth- but please keep in mind our deadline for ods of thermoforming. Additionally, we have featured educators like Bill submissions is no later than December 1st of McConnell, Jim Throne and Herman R. Osmers, who have both each year, so nominations received after that spread the word and were key fig- time will go forward to the next year. ures in founding the Thermoforming Division. We’re looking for more individu- als like these and we’re turning to These sponsors enable us to publish Thermoforming QUARTERLY the Thermoforming community to find them. Requirements would in- clude several of the following: ➢Founder or Owner of a Thermoforming Company ➢Patents Developed ➢Is currently active in or recently retired from the Thermoforming Industry ➢Is a Processor – or capable of processing ➢Someone who developed new markets for or started a new trend or style of Thermoforming ➢Significant contributions to the work of the Thermoforming Division Board of Directors
Thermoforming QUARTERLY 6 Thermoformers of the Year … 1982 William K. McConnell, Jr. McConnell Company 1983 THERMOFORMER OF E. Bowman Stratton, Jr. Auto-Vac Corp. 1984 THE YEAR 2007 Gaylord Brown, Brown Machine Presented at the September 2007 Thermoforming Conference in Cincinnati, Ohio 1985 Robert L. Butzko The Awards Committee is now accepting nominations for the 2007 Thermtrol Corp. THERMOFORMER OF THE YEAR. Please help us by identifying worthy candidates. 1986 This prestigious honor will be awarded to a member of our industry that has made George Wiss, Plastofilm Industries a significant contribution to the Thermoforming Industry in a Technical, Educa- 1987 tional, or Management aspect of Thermoforming. Nominees will be evaluated Dr. Herman R. Osmers Educator & Consultant and voted on by the Thermoforming Board of Directors at the Winter 2007 meet- 1988 ing. The deadline for submitting nominations is December 1st, 2006. Please com- Robert Kittridge plete the form below and include all biographical information. Fabri-Kal Corporation 1989 Person Nominated: ______Title: ______Jack Pregont, Prent Corporation 1990 Firm or Institution: ______Ripley W. Gage, Gage Industries Street Address: ______City, State, Zip: ______1991 Stanley Rosen Telephone: ______Fax: ______E-mail: ______Mold Systems Corp. 1992 Biographical Information: Samuel Shapiro Maryland Cup • Nominee’s Experience in the Thermoforming Industry. Sweetheart Plastics • Nominee’s Education (include degrees, year granted, name and location of 1993 university) John Grundy, Profile Plastics 1994 • Prior corporate or academic affiliations (include company and/or institu- R. Lewis Blanchard tions, title, and approximate dates of affiliations) Dow Chemical • Professional society affiliations 1995 James L. Blin, Triangle Plastics • Professional honors and awards. 1996 • Publications and patents (please attach list). John Griep • Evaluation of the effect of this individual’s achievement on technology and Portage Casting & Mold progress of the plastics industry. (To support nomination, attach substan- 1997 tial documentation of these achievements.) John S. Hopple, Hopple Plastics 1998 • Other significant accomplishments in the field of plastics. Lyle Shuert, Shuert Industries • Professional achievements in plastics (summarize specific achievements upon 1999 which this nomination is based on a separate sheet). Art Buckel, McConnell Company 2000 Individual Submitting Nomination: ______Title: ______Dr. James Throne Sherwood Technologies Firm or Institution: ______2001 Joseph Pregont, Prent Corp. Address: ______City, State, Zip: ______2002 Phone: ______Fax: ______E-mail: ______Stephen Sweig, Profile Plastics 2003 William Benjamin Benjamin Mfg. Signature: ______Date: ______2004 (ALL NOMINATIONS MUST BE SIGNED) Steve Hasselbach, CMI Plastics 2005 Please submit all nominations to: Hal Gilham, Manfred Jacob Productive Plastics, 103 West Park Drive Jacob Kunststofftechnik Mt. Laurel, New Jersey 08045 2006 Paul Alongi, MAAC Machinery
7 Thermoforming QUARTERLY THERMOFORMING These sponsors enable us to publish Thermoforming QUARTERLY DIVISION FALL BOARD MEETING SCHEDULE September 13th - 16th, 2006 Renaissance Nashville Hotel Nashville, Tennessee FOR RESERVATIONS: Call 615.255.8400 Request SPE Thermoforming Rate of $143.00 Wednesday, September 13th, 2006 Executive Committee Arrives Thursday, September 14th, 2006 7:30 am – 8:00 am – Breakfast – Executive Committee, Bluegrass Room 8:00 am – 9:00 am – Technical Chairs Meet with Executive Committee 12:00 pm – 12:30 p.m. – Lunch – Executive Committee 2:00 pm – James Alongi, Finance Committee Meet with Executive Committee Friday, September 15th, 2006 9:00 am – 10:00 am – Machinery Committee Meeting, Jazz Room 9:00 am – 10:00 am – Materials Committee Meeting, Classical Room 9:00 am – 10:00 am – Processing Committee Meeting, Belmont One Room 10:00 am – 4:00 pm – Committee Meetings, Belmont Three Room BOARD ON THEIR OWN Saturday, September 16th, 2006 7:30 am – 8:00 am – Breakfast – Board of Directors, Music City Ballroom 8:00 am – Noon – Board of Directors Meeting, Music City Ballroom 12:00 pm – 1:00 pm –Lunch Buffet, Music City Ballroom Foyer 6:00 pm – 8:00 pm – BOARD OF DIRECTORS SPECIAL EVENT – “An Evening at the Blue Bird Cafe,” Music City Ballroom Sunday, September 17th, 2006 6:15 pm – 6:30 pm – Ribbon Cutting Opening Exhibits, Convention Center 6:30 pm – 8:30 pm – Welcome Reception, Exhibit Floor, Convention Center September 18th, 19th & 20th, 2006 16th Annual Thermoforming Conference
Thermoforming QUARTERLY 8 LEAD TECHNICAL ARTICLE A Solution for Warpage in Polymeric Products By Plug-Assist Thermoforming1,2,3
BY H. HOSSEINI AND B. V. BERDYSHEV MOSCOW STATE UNIVERSITY OF ENVIRONMENTAL ENGINEERING, MOSCOW, RUSSIA Abstract there is another problem that the thermoforming industry must overcome. The sheet during inflation may have physical instabilities The thermoforming process is one of the most popular techniques such as sheet rupture and shrinkage that is exhibited in the final in polymer process. The broad spectrum of applications is because products. of its high performance, simplicity, compactness, and relatively Another inherent fundamental processing defect in the low-cost equipment. The fundamental defect inherent in thermoforming technology is part warpage that occurs during use. thermoforming technology is warpage of the products during their This is particularly apparent at high temperatures, Figure 1. The applications. This is particularly apparent when the products are warpage defect is understood as the process of non-uniform or used at high temperatures. The warpage defect is understood as heterogeneous change of the geometric dimensions of product with the process of non-uniform or heterogeneous change of the time, resulting in a change or distortion of their original form. geometric dimensions of product with time, resulting in a change Unfortunately, this problem has been overlooked or ignored in or distortion of their original form. The results of this work allow thermoforming literature [2]. thermoformers to find the causes of this warpage and to ascertain the processing conditions that give rise to this defect. This makes it possible to work out valid recommendations for the partial, and in some cases complete, elimination of warpage. Introduction Polymer processing production of all forms of polymeric articles has found great application in chemical industries. The thermoforming process is one of the most popular techniques in this field. Thermoplastic sheet or film-forming techniques are applied to various packaging applications such as medical devices, food containers, and pharmaceuticals [1-4]. The broad spectrum of thermoforming is because of its high performance, simplicity, Figure 1. The warpage of a polymeric product during its use. compactness, and relatively low-cost equipment. These factors make it possible to produce complex, large-scale configurations The results of this work allow thermoformers to find the causes and free-form shapes. In thermoforming, a heated plastic sheet is of this warpage and to ascertain the processing conditions that give stretched into a mold cavity by applying pressure, eventually rise to this defect. This makes it possible to work out valid assisted by direct mechanical loading [5,6]. When the sheet contacts recommendations for the partial, and in some cases complete, the cold surface of the mold, it is prevented from further elimination of warpage. deformation. As a result, the forming sequence yields a thickness variation in the final part. In addition to wall thickness variation, Mathematical Description and Rheological Model 1 Paper was published in the 2006 ANTEC proceedings and was presented at ANTEC on 8 May 2006. An analysis of the results obtained shows that warpage is caused 2 Paper retyped, partially rewritten, and edited by J. L. by relaxation of the residual or frozen-in stresses produced during Throne,Technical Editor, who is solely responsible for any omis- the thermoforming process. Consider the after-effects of the sions, commissions and other blunders. deformation process of a viscoelastic polymer that had been 3 Ed. Note: The mechanical deformation of plastic sheets, called subjected to the direct deforming influence of a fixed degree of “plug assist,” has been the subject of previous Tech Articles in this intensity under pure shear. Quarterly, at recent Thermoforming Conferences, and in a very The kinematics of the direct deformational influence on a important paper being given at the upcoming 2006 Conference in polymer has not been randomly chosen. It completely corresponds Nashville. The Editor believes that the approach given in this pa- per deserves further scrutiny by those examining the fundamen- to the deformation kinematics of a polymeric product at the initial tals of plug assist. (continued on next page)
9 Thermoforming QUARTERLY § H ~ · (continued from previous page) ¨ 2He t ¸ © I ¹ ~ ~ 1e t tp e 1 § H ~ · stage of pre-stretching with a plug [1]. In this case, the kinetics of ¨ 2He t ¸ 1 © I ¹ (3a) H ~ 1e the development of general viscoelastic and elastic deformations He t | ln § H ~ · ¨ 2He t ¸ © I ¹ ~ ~ resulting from the direct deforming effect on the polymer is given 2 1e t tp e 1 § H ~ · in the literature [1]. ¨ 2He tI ¸ ~ 1e© ¹ Assume that at a certain point in time, t I , the direct deforming effect on the polymer is instantly removed by the removal of any external effects on it. At that time, as a result of the deformation, ~t H ~ H ~ H ~ H ~ 1 2H t 2H t ~ (3b) H t | H t e e e e dt certain levels of general viscoelastic and elastic deformations have I ³ >@ 4 ~t been accumulated: H ~ H ~ I H tM ,He tI . This condition corresponds to the free or unconstrained condition ~ t ~ Now t , the dimensionless time and tI is the dimension- of the polymer in the molded product. Now, in accordance with T0 T the rheological model [1], for a polymer medium in the less time of plug-assist forming. Figure 2 represents the kinetics of unconstrained condition, the relaxation process will occur at rates the process of free relaxation of elastic deformations in a that relate to the reduction in the level of accumulated elastic viscoelastic polymer resulting in the uniaxial process of changing deformation. This is characterized by the following natural kinetic its original dimensions6. conditions:
(1) e e f
Where e is the strain rate tensor and e f is the flow strain rate tensor. The meaning of this condition is that in the absence of an external. influence on the polymer, the rates of deformation changes in the latter are determined only by the typical rates of the relaxation processes themselves. Applying this condition of the rheological model [1,7] to the kinematically determined process of deformation after-effects in a viscoelastic sheet or formed shape, the following system of differential equations that describe the kinetics of the procession are obtained4: Figure 2. The kinetics of the process of free relaxation, ~t > 4, of elastic deformations in viscoelastic polymers resulting in the process of chang- dc 2 1 >@E cc12 ~ (2a) c 1 e ing its original dimensions, tI = 4. [Ed. note: It appears that the vertical dt 2T0 T H H scale is , the top curve is , the second curve is e , and the horizontal scale is ~t .] H dH 1 1 (2b) c c1 e>@E cc 2 dt 4 T T0 Results and Discussion
H 2 2He Where c { O e e , c is the Cauchy strain, T 0 T is relaxation As shown above, the cause of molded part warpage during use time, is the flexibility parameter of the molecular chain, H is the is the accumulation of elastic deformations in the polymer. Because H Hencky strain, e is the elastic Hencky strain, e and is the elastic the accumulated elastic deformations in the polymer are usually strain ratio. non-uniformly distributed throughout the formed part, the The initial conditions for solving the system of equations relaxation process occurs at different rates across the part. This H ~ H ~ H tM ,He tI are determined by solving the deformation influences results in noticeably different rates of dimensional change in on the polymer. From an analysis of these equations, it follows different regions of the part, that is, the warpage as evidenced by H that the elastic deformation, e , accumulated during the the last set of equations above. On the basis of our analysis, we deformation sequence on the polymer, relaxes at a rate dependent find that the defect of warpage originates under the condition of on the removal of the mechanical field – in this case, the plug – the accumulation of heterogeneous elastic deformations in the from the polymeric sheet. This leads to the reduction in accumulated polymer during thermoforming, and it manifests itself through the general deformations as given by the second equation5. relaxation process of these deformations. For rigid chain polymer, ➝ 0, or for a low level of accumulated The equations above show that warpage is essentially determined H ~ He t by one of the fundamental rheological characteristics of polymers, elastic deformation, I , the following solutions follow: e o 1 the typical relaxation time, 0(T), which is temperature-dependent. Relaxation processes increase in rate, and, consequently, the rate 4 Ed. Note: The analysis that follows implicitly assumes uniaxial of warpage increases with increasing polymer temperature. deformation and relaxation. For multiaxial deformation and relax- Consider a quantitative characterization of the time-dependent ation, the scalar Cauchy, Henky, and elastic Henky strain terms warpage. A coefficient of dimensional change, ku , that integrally must be replaced with the equivalent tensors. 5 Ed. Note: Again, keep in mind that the authors appear to assume 6 Ed. Note: Unfortunately, the labels for the curves on in this figure that the mechanical deformation of the sheet with a plug is a uniaxial are obscured in the original paper. Those given in the figure cap- deformation process. tion are those proposed by this Editor.
Thermoforming QUARTERLY 10 characterizes the relative change in the original dimension of the minimized. This means that the profile of the pre-stretched sheet product is defined as: should be maximized to approximate the profile of the final product. S ~t (4) kuI 1 ~ ~ S t tI The Concept of Relaxation Pause ~ ~ ~ Unlike the forming process, the mechanical plug pre-stretching Where S t and S t t I are the current and original area of the lateral surface of the distorted part, respectively. process can be regulated through control of the plug motion. This Using well-known mathematical equations and the equations provides an opportunity to organize, at the plug stage, the relaxation given earlier, we obtain the following: process of elastic deformations accumulated in the sheet because
~ of the stretching action of the plug. The simplest of many possible H ~ 4 ~ ~ b z b ~ scenarios to achieve this is to create a relaxation pause between (5) S t tI 2Sr3 b dz ³ ~ 3 the pre-stretching step and the vacuum forming step. During this 0 b z pause, the accumulated elastic deformations can completely or ~r 1 H ~ ~ 0 H r0 ,t (6) ~ ~ ~ e ~ partially relax. The problem here is that during this pause, the pre- S t 2Sr3 b r0 1, t ~ dr0 ~ ³~ r stretched sheet may cool too much, making the forming step of the r0 rp 0 2 process difficult or impossible. Consider the necessary duration of § ~r · r H z ~ ~ 2 ~ ~ p ~ p ~ ~ this pause that would allow realization of the relaxation process. Whereb t tI { O z 0 1 ¨ H ¸ , rp { , H { , z { , and ¨ 1 ~r ¸ r r r © p ¹ 3 3 3 During the relaxation pause, a plug holds the stretched sheet. H ~ ~ ~ ~ 2 ~ ~ 2H r0 1,t b r0 1, t { O r0 1, t e 1 , where rp is the plug radius, r3 is One of the kinematic conditions of this process, corresponding to the initial radius of the sheet, r and z are the horizontal and vertical the absence of an external deforming influence, is: axes, respectively, and H is the depth of the deformed sheet. The H ~ ~ e function, H r 0 , t , is determined from solution of the set of earlier (8) = 0 differential equations (2a and 2b). Using equations (5) and (6) from equation (4), we obtain an Using this condition, from the rheological model for the expression that describes the kinetics of warpage as shown in Figure kinematically determined process of the relaxation in a viscoelastic 3. If we now assign an allowable value of the coefficient of polymeric medium [1], we obtain the following equation that dimensional change of the product, > k uI @ , with which the part is describes its kinetics: considered suitable for its use, the maximum permissible time of dc 1 1 its use is given as: (9a) c2 1 e>@E cc 2 dt 2T0 T
dH H (9b) 0 dt Figure 4 presents the kinetics of change of elastic deformations during the relaxation pause in a sheet stretched with a plug7.
Figure 3. The kinetics of the warpage of PS at T=353K. Curve is from equation (4) and the points are experimental data. [Ed. note: The verti- ~ cal scale is ku and the horizontal scale appears to be t .]
~ (7) >kuI @ kuI t Figure 4. The kinetics of the relaxation process, ~t > 4, of elastic defor- ~ ~ mations in viscoelastic polymers during the relaxation pause, t = 4. Where k u t is determined from equation (4). I H It is now apparent from the above analysis that the use period of [Ed. note: It appears the vertical scale is , the top curve is , the sec- ond surve is H, and the horizontal scale is ~ .] a polymeric product under the given temperature conditions, with e t the allowable coefficient of dimensional change, is essentially Comparing the differential equation systems (9a and 9b) and ~ (2a and 2b), it is seen that the relaxation processes in polymers determined by the elastic deformations, c r 0 , t I ,, accumulated in the product during its formation. The smaller they are, the longer under the conditions of limited and free after-effects vary only by will be the operational period of the product. their rates. Therefore, it is apparent that the practical task is organizing the 7 Ed. Note: Again, unfortunately the labels for the curves in this plug-assist thermoforming methods so that the total level of elastic figure are obscured in the original paper. Again, those given in the deformations – that is, the accumulated deformations during both figure caption are those proposed by this Editor. the plugging and the forming stages of the molding process – is (continued on next page)
11 Thermoforming QUARTERLY (continued from previous page) It follows from these equations that the procedure of the equation This is quite logical, considering that the limited conditions of systems (2a and 2b) that satisfies equation (11) is reduced to a the relaxation after-effects do not completely correspond to the search of the critical maximum value of the elastic deformation, ~ removed mechanical field, superimposed on the polymeric medium. c*0 tI . This value should not be exceeded in a given section of the This also slows the development of the relaxation process. For stretched sheet at the end of the relaxation pause. This value must rigid-chain polymers, ➝ 0, or at a low to moderate level of satisfy the condition in equation (11). H ~ He tI accumulated elastic deformation, e o 1 , the analytical solu- When this value is found, the duration of the necessary relaxation tion of equations (9a and 9b) is: pause is determined by solving the differential equation (9a). For
H ~ 2 r ,t the special case given above, when the obtained value is substituted He 0 M ~ ~ 1 e t t I as the current one, corresponding to the end of the relaxation pause H ~ e 1 2He r0 ,tM H ~ 1 1 e H r , t | ln H ~ in equation (10a), an expression is obtained that determines the (10a) e 0 2H r ,t 2 e 0 M ~ ~ 1 e t tI operational factors of the duration of the relaxation phase: H ~ e 1 2He r0 ,tM 1 e ~ ~ § c t 1·§ c t 1·½ °¨ 0 I ¸¨ *0 I ¸° (13) t pn T0 T ln® ~ ~ ¾ H ~ H ¨ c t 1¸¨ c t 1¸ (10b) H r0, t H r0 const ¯°© 0 I ¹© *0 I ¹¿°
The analysis of the equations obtained by numerical solution of The level of elastic deformation in the sheet can also be reduced the differential equations (9a and 9b) for common cases shows by decreasing the speed of the plug. This effect can be determined directly from the results in this work. However, in certain cases, that even in the most unfavorable conditions, > 1 and c(t ≈ 3), the accumulated elastic deformations are practically completely the time of sheet stretching will exceed the sum of the time spent stretching at a normal plug speed and the relaxation pause. This is relaxed in a time period not exceeding approximately 9 0(T). In thermoforming, most thermoplastic materials have typical apparent because, in the plug-assist stage, a much greater mechanical force is imposed on the polymer than the effect of the relaxation times in the range of 0(T ) ≈ 0.2 to 0.5 seconds. Thus, even in the most unfavorable situations, the maximum time relaxation pause. As a result, the rate of the relaxation step in the necessary for the relaxation process would not exceed about 4.5 plug assist step will be less than that in the forming step. seconds. Note also that the necessary time for the relaxation process during From [8], it was determined that for a Bi=0.04 and Fo=1.75, the relaxation pause can be reduced by raising the temperature of within this time frame, a polymer sheet with thickness of, for the sheet. This results in a reduction in the typical relaxation time. example, 1.0 mm and a temperature of T=140°C, cools only about However, as noted earlier, the thermoforming operating range, ° 10 C. This time is not considered critical when comparing the time Tg < T < Tm , limits the practical use of this option. spent during the pre-stretching phase of the process. For thinner sheets, the maximum duration of the relaxation pause Summary will obviously become critical. But this will occur only under the very strict requirements concerning the quality of the final product, The analysis conducted on the causes and conditions of warpage according to the admissible criterion of their distortion, viz, in thermoformed products under specific applications has yielded: k 0 . In less strict conditions, when some level of distortion is > uI @o • A method for calculation the operating conditions for admitted, as determined the value of > k u I @ , t , the time necessary for forming products that would ensure operation of the the relaxation pause, is determined as follows: final product with warpage not exceeding admissible The minimum duration of the relaxation pause should be a value values. that guarantees an infinitely large use time for a product with the • A method for calculating the maximum admissible allowable coefficient, k . Nominally, considering equation (4), > uI @ period for the use of polymeric products within which this is given as: the warpage would not exceed allowable limits. ~ ~ (11) S t o f t S tI 1 >kuI @ • Uneven strain recovery, caused by non-uniform orientation in the trim area is the major cause of long- ~ From the analysis of equation (6), the function S t is determined term part distortion and warpage. In some cases, 24- by solving the differential equations (2a and 2b). Solving the hour annealing at mold temperature prior to trimming 8 H H ~ can reduce warping . equations under different initial conditions, H r 0 , H e r 0 , t I ,, will always yield a solution that will satisfy the condition of equation (11). The results obtained in this work provide the following Acknowledgments expressions for determining the initial conditions specified above: This word was supported by the Laboratories of Moscow
2 ª ~ 4 ~ ~ 4 ~ º½ State University of Environmental Engineering and Moscow 1 1 c t 1 1 ~r b t § c t 1 1 ~r b t · H ~ ~ ° « 0 I 0 I ¨ 0 I 0 I ¸ »° H r0 , tM ln® ~ x ~ x 3 ~ x ~ x 3 4 ¾ 2 2 « c t 1 b t ~r ¨ c t 1 b t ~r ¸ » State University of Chemical Engineering. ° 0 I I 0 © 0 I I 0 ¹ ° ¯ ¬« ¼»¿
~ ª§ ~ · º 8 H 1 Hrp Ed. Note: The authors do not explicitly address this conclusion in H r ln«¨ ¸ 1» 0 2 ¨ 1 ~r ~r 2 ¸ ¬«© p 0 ¹ ¼» this paper.
Thermoforming QUARTERLY 12 References 4. G. J. Nam, K. H. Ahn, and J. W. Lee, Poly. Eng. Sci., 40, 2000, pg. 2232. 1. H. Hosseini and B. V. Berdyshev, Structural Plastics 5. Rush et al., U.S. Patent 5 641 524, 1997. 2005, Society of Plastics Industry, Orlando, Florida. 6. A. Wineman, Jnl. Non-Newt. Fluid Mech., 4, 1987, pg. 2. J. K. Thoren, Thermoforming, Hanser Publishers, 249. Munich, 1987. 7. A. I. Leonov, Rheol. Acta., 15, 1976, pg. 85. 3. J. K. Lee, T. L. Virkler, and C. E. Scott, Poly. Eng. Sci., 8. B. N. Udaev, Engineering Thermodynamics, in Russian, 41, 2001, pg. 1830. Moscow, 1988.
News from PennState, Erie, The Behrend College SPE Grant Will Help Purchase Thermoformer tudents in Penn State Behrend’s plastics engineer- Sing technology program will have access to the latest thermoforming equipment, thanks to a grant from the Society of Plastics Engineers Foundation. The Brookfield, Conn.-based foundation for the support of plastics and polymer education has awarded Behrend’s program a $10,000 matching grant for the purchase of a Formech 660 vacuum forming machine. Vacuum forming is a technology that forms sheets of plastic into a desired shape and is used to create prod- ucts that range from clamshell take-out food contain- ers to automotive body panels. Penn State ment as soon as it Behrend will match “We were very fortunate to get this grant from hits the floor.” the gift equally, and the thermoforming division of the SPE. This In addition to Formech, which is being used by stu- headquartered in piece of equipment will go a long way to dent researchers, Harpenden, En- improving the quality of education our students the Formech 660 gland, has agreed to will receive in the area of thermoforming,” will permit the col- a discounted flat Brian Young, assistant professor of lege the add a tech- price of $20,000 for nical elective in the 660, three re- Engineering, said. “I have several students who thermoforming, ducing plates, and are interested in starting research projects on develop training an optional cooling this equipment as soon as it hits the floor.” seminars and system. applied research The Formech 660 will be installed into the new projects that support local industry, and enhance the 160,000-square-foot Research and Economic Devel- employment prospects of plastics engineering technol- opment Center (REDC) opening on campus in fall. ogy graduates by exposing them to a growing “We were very fortunate to get this grant from the technology. thermoforming division of the SPE. This piece of Penn State Erie’s plastics engineering technology equipment will go a long way to improving the quality program boasts 100 percent job placement; more than of education our students will receive in the area of 300 inquiries were received in 2005 from companies thermoforming,” Brian Young, assistant professor of interested in hiring the year’s 40 graduates. Engineering, said. “I have several students who are Contact: Christine Palattela, 813.899.6063, interested in starting research projects on this equip- [email protected]. ■ (continued on next page)
13 Thermoforming QUARTERLY INDUSTRY PRACTICE How Much Data is Enough?1 BY RICHARD KNEBEL, CARL ZEISS IMT CORP., MINNEAPOLIS, MN
oordinate Measuring Machines or CMMs come in of this need when evaluating location and size. It is easy Cmany types, but one important area of distinction is to assume that if a particular feature has no specific form the method of data acquisition. requirement, data density is not an issue. But it is There are two basic types of CMMs – touch-trigger important, and especially so when form isn’t controlled probing and scanning. Today, the touch-trigger CMM is separately. Form deviation exists in all measured features, most common. It measures features by contracting only the magnitude of deviation varies. When form is individual points on the workpiece. The scanning probe not controlled separately through the use of a modifier SCMM uses a probe sensor that is, by itself, a small such as circularity or roundness of a bore, then limits of measuring machine. Linked to the larger CMM with size control the allowable form deviation. advanced control technology, it continuously scans the Studies show that a minimum of 300 points are contour of the workpiece surface. Scanning CMMs can required to approach the correct result for form such as collect hundreds or even thousands of independent points circularity of a diameter in the 25 to 70 mm range. Only to define a part feature in the same time it takes touch- above this level of data density will you begin to approach trigger probe CMMs to measure only four to eight points. 90% or more of the correct form value. Any method that When choosing a CMM, it is common practice to uses lots of data will see a more complete “picture” of obtain the machine’s measurement uncertainty from the the surface, and gain a better understanding of the true manufacturer. The data are compared to part size and high-to-low variation. Low data density most likely will tolerances to determine the suitability of a particular miss this variation and has the potential to be somewhat CMM for a given application. There is, however, once more repeatable. potential shortcoming. Specifications for measurement In other words, if repeatability of form was the uncertainty are made relative to traceable artifacts such primary objective, one could measure only four points as gage blocks and ring gages. and calculate, for example, flatness. In general, however, One might ask, what’s wrong with that? It’s common the benefit of high density data is obvious when looking practice to specify a system’s capability relative to known at the average results for many features. artifacts. But it must be understood that these known You may have heard the saying “form follows artifacts are produced to have nearly perfect form. They function.” Ad agencies often use it to describe a product are actually gages that are used to measure the CMM’s with a very functional appearance. The inverse of this performance. The fact that they have near-perfect form saying, “function follows form,” is true in metrology. makes them a relatively easy target to measure using low You cannot know the functional size and location without data density. understanding the form of a feature. In day-to-day use, CMMs must inspect imperfectly When evaluating a CMM, consider the influence that formed features. This task is much more difficult than form has on size and location. It can be greater than any inspecting artifacts with near-perfect form, because error inherent in the CMM. Select a system and method results can vary significantly depending on where the that can accurately measure production parts, not just CMM samples the feature. perfect artifacts. If a CMM must pass a gage repeatability Most people are aware of the need for high data and reproducibility or GR&R study, high data density is density when evaluating form, but there is less awareness the best defense when challenged to repeat readings on imperfectly formed elements. 1 This article has been edited from an article appearing in Manu- High data density also provides better functional facturing Engineering, November 2002, pg. 15. It is used with permission of Society of Manufacturing Engineers, www.sme.org, results that lead to fewer problems in assembly, lower and cannot be recopied without permission of the copyright holder. warranty costs, and improved overall production The Technical Editor is responsible for any rewriting, omissions, or processes. ■ errors in transcription.
Thermoforming QUARTERLY 14 THERMOFORMING These sponsors enable us to publish Thermoforming QUARTERLY DIVISION DVD’S STILL AVAILABLE
The first DVD is titled: “WHAT EXACTLY IS THERMOFORMING?”
This six-minute DVD introduces the viewer to the thermoforming process with examples of parts produced and a video of the process. Both thin gauge roll fed and heavy gauge cut sheet fed aspects of thermoforming are illustrated. It is for students, industry and anyone who wished to learn more about thermoforming.
The second DVD is titled: “FORMING EDUCATIONAL OPPORTUNITIES: GRANTS AND SCHOLARSHIPS OFFERED BY THE SOCIETY OF PLASTICS ENGINEERS – THERMOFORMING DIVISION”
This six-minute DVD discusses the 13 matching equipment grants of up to $10,000 and 20 scholarships up to $5,000 for college students. Information is provided for applying to these grants and scholarships. The Thermoforming Division of SPE has contributed over $150,000 in equipment grants and scholarships as of this date.
Both DVDs are free of charge and available from SPE through Gail Bristol at phone number 203-740-5447 or Gwen Mathis, Thermoforming Division, at phone number 706-235-9298.
15 Thermoforming QUARTERLY INDUSTRY PRACTICE IR Scanning With Closed-Loop Feedback for Thin-Gauge Thermoforing1 BY C. P. CARLIN, SENCORP, INC., AND C. CASALE, LAND INSTRUMENTS
hen Lexus introduced their slogan, “The equipped with a means of reading temperature. WRelentless Pursuit of Perfection®,” they However, what is easily forgotten at this stage of made a simple and bold statement. They explicitly the process is what really matters is the temperature stated what most businesses strive to achieve – of the sheet. Infra-red sensors, pyrometers, and the reduction in errors. Whether it is a program of heat guns provide a limited reading of the sheet. continuous improvement or lean manufacturing, The latest technology that allows for a more businesses today in North America understand that complete visualization of the sheet is an infra-red in order to remain competitive, they must reach line scanner, Figure 1. for perfection. This is a principle that has implications for today’s thermoforming industry. It has long been assumed that practice makes perfect. But what happens when outside factors influence what you’ve been practicing? In a process filled with variables, it is not always possible to have complete control. In thermoforming, if we focus on just the material (and assume there is no in-house extrusion), we find several factors that are outside the processor’s control. These factors include: • Basic material type/properties, • Thickness, • Material storage, and Figure 1. • Ambient room temperature. When taken by itself, the line scanner provides If we focus on what the processor can control, a graphical image of an entire index length of the the first stage of thermoforming is heating the sheet, scanning through a window of less than one sheet. inch or 25 mm, Figure 2. Oven temperature is both easy to control and When coupled with a powerful closed-loop easy to define. Whether the heating elements are system, this method of scanning becomes a serious quartz, ceramic, or other, all machines are advantage for the custom thermoformer. The process now becomes more mathematical and 1 This article is based on a case-study using a Land Instruments rigorous, allowing the operator to analyze and LFP7 line scanner and a Sencorp Series 2500SD in-line thermoformer. (continued on next page)
Thermoforming QUARTERLY 16 (continued from previous page) point. The operator only has control of the heater elements. When the closed-loop system is integrated, the situation changes dramatically. When setting up a job, the operator can start the scanner and view the sheet temperature profile on the control system screen. Next, the tolerance range of the sheet is entered into the program so that if a change in temperature is detected, the closed-look system will determine whether a single zone or the entire oven needs to be adjusted. The operator also has control of the number of indexes required before making any change, Figure 4.
Figure 2. monitor sheet temperature in a way that was previously unavailable. By scanning up to one hundred lines per second, a line scanner provides one thousand data points per line, or one hundred thousand temperature points per second (100,000/ sec), Figure 3.
Figure 4. Trial and error can be costly, especially when using expensive and complex materials. We are not thermoforming ovens, we are thermoforming sheet. Scarp, returns, and downtime all cost money. If all three of these variables can be reduced and/ or eliminated, the thermoformer is one step closer to perfection. ■
Figure 3.
The current system of heating the sheet relies on operator skill and savoir faire. Assuming a new job, the machine is set up and run until acceptable parts are formed. Then, the heater controls are calibrated to a set-point and the operator is alerted if the oven temperature is above or below this
17 Thermoforming QUARTERLY Twin-Sheet These sponsors enable us to publish Thermoforming QUARTERLY Thermoforming?
“This method is commonly used for making hollow articles. Two pieces of sheet are placed between the top and bottom dies of the mould, and compressed air or steam is blown in between them until the plastic has assumed the required shape. At the final stage of the moulding, extra pressure given to the edges of the mould causes the superfluous
sheet to be cut away, whilst PERFORMANCE. INNOVATION. DEPENDABILITY. the effective edges fuse together so that the finished Proven Partnership. articles are removed in one Worldwide Benefits. piece. The die is ventilated with very fine air outlets so For the best in trim-in-place and high volume thermo- as to obviate airlocks with forming equipment, parts and service, talk to the global experts at Lyle and Gabler. Call 989-435-7717 the resulting faulty for details, or visit lyleindustries.com. mouldings. The sheets of plastic are usually slightly heated before being placed in www.gabler-maschinenbau.de 4144 W. Lyle Road ■ Beaverton, MI 48612 the die. If steam is used for blowing, a pressure of about 50 lbs. per sq. in. is employed; if compressed air, the approximately double that pressure is necessary.”
F. W. Kellaway and N. P. Meadway, Introducing Plastics, The Scientific Book Club, London, 1945.
Thermoforming QUARTERLY 18 The Cutting Edge BY JIM THRONE, SHERWOOD TECHNOLOGIES, INC., DUNEDIN, FL
or those of you who came in late, Fwe have been examining the various aspects of part design. In this lesson, we focus on the edge or periphery of the part. The first thing we need to realize is that the part we’ve just thermoformed is still THERMOFORMING attached to the plastic that held it in the clamp frame while it was being formed. 101 This is true whether the entire assembly, formed part and edge material, is removed to a separate fixture or whether the formed part is punched from the trim material immediately after forming. is rough-cut initially. This edge finish Nevertheless, the trim edge charac- We’ve discussed trimming in earlier may be adequate if the cut edge of the teristics can be quite important to the tutorials. In this tutorial, we discuss the part is completely hidden in the final customer. There are three major issues characteristics of the edge itself. assembly. Polycarbonate skylights that with the cut edges of thin-gauge parts: are edged in aluminum are examples. • Trim dust and fibers, known as Registration Often the product requires a smoother angel hair and fuzz. edge. For robotic trimming to achieve the Trimming devices need to trim the part desired edge, the rough-cut edge is • Microcracks that can grow into the where the designer wanted it trimmed. routed a second time while the part formed part as it is flexed This means that the trim line and the trim remains on the trim fixture. • Jagged edges that can cut or abrade device must register. The accuracy of In some applications, the edge must the user registration is a design issue. In heavy be as smooth as the overall plastic gauge forming, it is impractical to ask a Edge and surface contamination are surface. Here are some ways of achieving trim device to trim within thousandths often the results of problems in the a very smooth, even polished edge. of the design trim line everywhere along trimming step. But not always. It is very the trim line. Heavy-gauge parts may be • Fine grit sanding followed by difficult to trim polystyrene without fixtured between the time they are Crocus cloth or 1200-grit polishing generating very tenacious trim dust. It is formed and the time they are trimmed. • The above method, followed by often difficult to trim polypropylene pr Fixturing allows for some residual stress pumice polishing PET without generating fibers and fuzz. relaxation and often improves the trim • For certain plastics, a light wipe Adding antistatic agents to PS, either as registry. In thin-gauge forming, the trim with a mild solvent will smooth trim an additive that is compounded into the device should be able to trim very close cuts. Care must be taken to polymer or as a topical coat to the sheet to the design trim line. Because many minimize the amount of solvent that prior to forming, helps the trim dust thin gauge parts are axisymmetric, is absorbed into the polymer. problem. If fuzz and fibers are meaning that the trim line is round, • Flame-polishing is popular with objectionable to the customer, they are registration focuses on the degree of transparent amorphous plastics such often minimized by passing the container ovality of the formed trim line prior to as acrylics and polycarbonates. edges through a hot air knife. The heat the trimming step. Thin-gauge parts are Flame-polishing is not shrivels the fibers to microscopic size. often trimmed within minutes of being Microcracks and jagged edges can also formed. Certain polymers such as recommended with plastics such as PVC. be “healed” by heating the edges with polypropylene continue to crystallize hot air. One approach is to collect and • Laser cutting. The laser is a high- after forming. As a result, the design trim nest a stacked, counted number of parts intensity beam that cuts plastic by line and the final part edge peripheral and pass the stack though a hot air tunnel melting and vaporizing it. The cut location may be quite different. prior to packaging or boxing for line is usually very smooth. shipment. ■ Heavy-Gauge Cut Edge Thin-Gauge Cut Edge The nature of the final cut edge Keywords: registration, flame polishing, depends strongly on the trimming device. Thin-gauge trimming is substantially laser cutting, trim dust, microcracks In many robotic trimming steps, the edge simpler than heavy-gauge trimming.
19 Thermoforming QUARTERLY There are seven chapters. There are there’s nothing in here on BOOK REVIEW many references to earlier, less thermoforming. If you want to learn complex efforts. The first chapter about the parameters that affect the considers the math of polymerization. cooling rate of your just-formed-and- The next three chapters focus on still-sitting-on-the-mold waiting-to- V. Capasso, Ed., Mathematical crystallite nucleation and the next two be-crystalline-eventually part, you’ll Modeling for Polymer Processing: on the mechanisms of crystallization. need to read the chapters you just Polymerization, Crystallization, The last section, 44 pages long, is skipped over. On the other hand, if Manufacturing, Springer Verlag, entitled “Manufacturing,” and you want to know what kinds of Berlin, 2003, 74.85 euro ($94), consists of one chapter, entitled issues face your sheet supplier, you “Modeling of Industrial Processes for 320+xiv pages, 90 figures, in English. might want to listen up (or in this Polymer Melts: Extrusion and case, read up)! Unfortunately, the Injection Molding.” Yep, you’re ll right, let’s get the bellyaching authors theoretically address only one right! Nothing on thermoforming! Aout of the way first. “Oh, Jeez, extrusion processing issue – flow another technical book!” “Who the “So,” you ask. “Why the heck are you reviewing this thing, anyway?” Well, instability, often called ‘melt heck reads all this stuff, anyway?” 4 don’t get your britches in a bunch just fracture.’ (The astute and well- “Why can’t this guy review a yet. Let’s keep in mind that some of educated reader should have learned practical book, like ‘Thermoforming the most challenging polymeric some of this arithmetic some time for Dummies’?” Okay, are you done? materials that we deal with are ago.) The authors add an additional Can I proceed? Thank you! (After all, crystalline in nature – polyethylene, term to the traditional KBK-Z this is my column, not yours!) polypropylene, TPO, PET … constitutive model to handle a newly- This is a technical book. Jam- Typically, we form these materials in defined effect the authors describe as packed with equations, most of which their amorphous, melt state. And then ‘spurt.’ (Your reviewer is not 1 appeal only to people of the ilk of we wait for them to crystallize … Or, comfortable replacing the traditional the particular author(s). The title with PET, maybe not. So chapters 2 ‘stick-slip’ concept with the authors’ intrigues – Mathematical Modeling through 6 form a basis for ‘Newtonian, latency, and spurt in Manufacturing! Wow! If we can understanding the various phases,’ though.) mathematically model, maybe we crystallization mechanisms. (Yes, Again, this is a collection of can predict. And if we can predict, Virginia, there are many mathematical treatises that is maybe we can eliminate many trial- mechanisms!) obviously not bedtime reading. And and-error steps as we bring a new The early chapters focus on it is not a book that will engender polymer/product to production. So, variations in Gibbsian cluster theory. heated debate on the Conference let’s see what’s between the covers. In short, how many molecules need floor. Nevertheless, many of us deal to collect in a given region before a First off, the book is a translation daily with semicrystalline polymers crystallite forms? How do they get of an edited collection of mostly and we should have at least get a European papers. The translation there? And why? There’s a nice section by the late A. Ziabicki, warm, fuzzy feeling that there are seems to flow well. In certain cases, underlying theories that describe why the equation jumps2 omit critical considered the father of modern crystallization theory, on the free our polymers behave the way they do. intermediate steps. In at least one energy of aggregation and … Oh … (And not necessarily the way we want case, the authors tacitly make a major, You’re not following along, are you? them to do!) very questionable assumption Well … Let’s see. Are you Because the book title purports to between equations which the interested in the theoretical reasons discuss the theory of processing (but reviewer believes calls into question why crystallization ceases for many doesn’t) and because the work their conclusions. polymers? No? Figgers. How about focuses extensively on crystallization mechanisms that promote pure kinetics but fails to apply same to 1 Ilk = type or kind. spherulitic crystallization rather than sheet extrusion, this reviewer gives 2 An ‘equation jump’ means that the text shish-kebabs? You know, the it only one-and-a-half books out of goes between two equations with little 3 explanation. Typically authors resort to the difference between quiescent crystal five. phrase, “therefore, …” growth and shear-induced crystal 3 Quiescent = quiet, still, tranquil, not growth? Not that, either? moving. Okay, then. Let’s jump right to the 4 Astute = discerning. manufacturing chapter. As I said, ~ Jim Throne
Thermoforming QUARTERLY 20 THERMOFORMING These sponsors enable us to publish Thermoforming QUARTERLY DIVISION TO FUND THE Acrylic Capstock and Film
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fund a program to Altuglas® and Solarkote® are registered trademarks belonging to Arkema. reward SPE Student © 2005 Arkema Inc. All rights reserved. Chapters who win the STRETCH Award. The Supplying the World with Plastic Processing Equipment STRETCH stands for Auctions • Appraisals • Liquidations New and Used Machinery Sales “Students Reaching Thermoforming • Injection Molding • Extrusion Blow Molding • Rotational Molding Excellence Through Why buy with Stopol: Chapters.” Application i If it is out there, we will find it. With our database of more than 27,000 companies, we will locate the equipment you need. forms are on the SPE i Our expertise and knowledge will provide you with the best machines to meet your needs. i Our vast inventory provides you with a variety of choices and alternatives. website: www.4spe.org. i Photos and video footage are available. Why sell with Stopol: The total amount is i Actively market your equipment to more than 27,000 companies, utilizing phone, fax, email and $5,000 and will be split advertising campaigns to get your equipment in front of qualified buyers. i We include your equipment on our web site which produces more than 125,000 hits per month. among the Student i We team with the most recognized and trusted publications in the plastics industry -- Plastics News, Modern Plastics, Plastics Hotline and Thermoforming Quarterly -- to market your equipment. Chapters who win the i Global presence with offices in London and Shanghai. Whether its remarketed plastics processing equipment, a plant auction, inventory liquidation, STRETCH Award with a or the sale and acquisition of a business, product line, or manufacturing license – Stopol is the resource. $500 limit per Chapter. STOPOL NEWS Lyle Industries, Inc. has announced the appointment of Stopol, Inc. as exclusive representatives to market Students lead busy lives the Lyle RFT Custom thermoformer and related equipment in North America. The RFT Custom offers complete form-trim stack capabilities in an economical, rugged package. Standard mold size is 32 x 36 inches. An available quick-change tooling package helps make the RFT Custom a versatile, efficient and we hope to motivate choice for a variety of applications, and the heavy duty construction helps ensure durability and precise thermoforming performance. them to complete all the requirements of the Stopol Office- Europe Stopol Office - Asia London Berkeley Square Shanghai One Corporate Center STRETCH Award. 2nd Floor 15F One Corporate Avenue Berkeley SquareHouse 22 Hu Bin Road London, W1J 68DUK LuWan District Phone: +44 (0) 207-887-6102 Phone: +86 21 6122 1302 If they do that, they are Fax: +44 (0) 207-887-6100 Fax: +86 21 6122 2418 [email protected] [email protected] truly an active chapter!
21 Thermoforming QUARTERLY Council Report … Charlotte, North Carolina
BY LOLA CARERE, COUNCILOR
his summary is intended to success of the recent vote on the dis- regions. Mr. Ratzlaff also indicated Thelp you review the high- solution. The motion to dissolve the that the International Committee is lights of the Council Meetings existing SPE Constitution passed by publishing a semi-annual newslet- held in Charlotte on May 7th, an overwhelming majority: 4,808 ter with additional details and sum- 2006. for, 153 against. Therefore, effective maries of activities throughout the Monday, April 10th, the new Bylaws world. Mr. Ratzlaff reminded the previously approved by Council ANTEC group of the Spanish-language se- became the official governing docu- Registration at ANTEC was ries for one set of seminars at NPE, ment for the Society. 2,063 (including registrants in the formation of the India Advisory seminars). A total of 206 registrants • Dr. Roger Corneliussen gave an Board, and network expansion with local Sections in Mexico and the attended 24 Society seminars. update on the Sections Committee Asia/Pacific rim area. Incoming President Tim Womer’s meeting. Issues discussed and pur- SPE mantra is “Are You In? (Inter- sued included regionalization and Governance Restructuring nationally Networked).” Section revitalization. Dr. Prior Past President Donna Davis Corneliussen recognized past Chairs presented data and progress on the Barbara Arnold-Feret and Alan From the Council Floor process for reviewing the current Arduini as well as Vice Chair Helen Each of the Society’s officers and governance structure. Ms. Davis re- Basso. vice presidents provided a brief up- viewed the mission statement of the date on their recent activities and • Bill Arendt provided an update Society and the philosophy the team liaison work. on the activities and plans for the has adopted in reviewing and evalu- Divisions Committee. Goals include ating potential changes to the cur- • Senior Vice President Vicki revamping/expansion of the Speak- rent governance structure. Flaris reviewed the International ers List, sponsoring new Divisions/ Awards, Fellows, Honored Service SIGs, and supporting Sections New Charters Member, and the other SPE award through MiniTecs. A Student Chapter was estab- programs and noted that the process lished at the University of Houston. • John Szymankiewicz provided has been completed for 2006. Dr. an update on ANTEC and the Awards and Recognitions Flaris also encouraged the submis- ANTEC Operating Committee. The In addition to the recognition of sion of names of additional candi- update included some details on the the retiring administration, the dates for the coming year. preparation for and results to date Michael Cappelletti Excellence • Kishor Mehta provided an up- on ANTEC 2006 in Charlotte, NC. Award was given to Hector Dilan. (Note: The James Toner Service date on the Constitution and Bylaws • Jon Ratzlaff provided an update Excellence Award was awarded at Committee (newly renamed going from the International Committee the Brookfield headquarters on May forward as the Bylaws and Policy on the work with headquarters and 19th, 2006 to two recipients this Committee) and the work on the re- local Sections to grow globally. Mr. year: Yetty Pauwels and Doris vision to Bylaws and dissolution of Ratzlaff gave details on the plan(s) the Constitution. He reviewed the to grow individual Sections/areas/ Thoren.)
Thermoforming QUARTERLY 22 Outgoing President Len Czuba • South Texas Section – Prior Past • Thermoset Division – Paid thanked his Executive Committee President Donna Davis presented a TopCon profits of $2,572. The Ther- for their hard work. Incoming Presi- check for $6,663 to SPE represent- moset Division also returned its dent Tim Womer introduced his ing new membership fees collected 2006 rebate check to SPE earlier this Executive Committee. New Execu- at the Polyolefins Conference. year. tive Committee Vice Presidents are: Barbara Arnold-Feret, Ken Braney, • Tex-La-Gulf Section – Rick • TPM&F Division – Sal Monte Dan Cykana and Bill O’Connell. Wagner presented a check for presented a check for $5,000 to the Paul Anderson is the 2006-2007 $32,308 to the SPE Foundation to SPE Foundation. Secretary and John Szymankiewicz begin a fund to provide scholarship • Vinyl Division – Presented a is the 2006-2007 Treasurer. and relief to victims of hurricanes check for $1,000 to the SPE Foun- Contributions and Donations Katrina, Rita, and Wilma. The con- dation Scholarship Fund and a check It is with grateful appreciation tribution to the Foundation repre- for $1,000 for the Student Author that the Society would like to ac- sents the entirety of the Tex-La-Gulf Travel Fund. ■ knowledge the following contribu- Section’s budget. tions and donations by its Sections and Divisions: These sponsors enable us to publish Thermoforming QUARTERLY • Bartlesville-Tulsa Section – Vivek Rohatgi presented a check for $1,000 to SPE. • Color & Appearance Division – Returned its $2,684 rebate pay- ment for the 1st and 2nd quarters. • Detroit Section – Tom Powers presented a check for $35,519 to the SPE Foundation for the Robert G. Dailey Scholarship, Hurricane Katrina Relief, International Award for Education, International Essay Award, and conferencing proceeds. • Electrical and Electronic Divi- sion – Amod Ogale presented a check for $946 to SPE, represent- ing the Division’s rebate from SPE for 2006. • Extrusion Division – Presented a check for $2,500 to the SPE Foun- dation Scholarship Fund. • Mid-Michigan Section – Ken Kerouac presented a check for $500 to the SPE Foundation for the Rob- ert Cramer Scholarship Fund. • Plastics Environmental Division – Dennis Denton presented a check for $13,000 from their GPEC pro- ceeds.
23 Thermoforming QUARTERLY These sponsors enable us to publish Thermoforming QUARTERLY
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Thermoforming QUARTERLY 24 These sponsors enable us to publish Thermoforming QUARTERLY
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**Please note the increase in sponsorship rates. This is the first increase since the inception of the Thermoforming Quarterly in 1981. We appreciate your continued support of our award winning publication. Patron - $625 (Includes 2.25" x 1.25" notice) Benefactor - $2,000 (Includes 4.75" x 3" notice) Questions? Please Contact: Laura Pichon Ex-Tech Plastics 815/678-2131 Ext. 624 [email protected] We Appreciate Your Support! From The Editor Thermoforming Quarterly welcomes letters from its readers. All letters are subject to editing for clarity and space and must be signed. Send to: Mail Bag, Thermoforming Quarterly, P. O. Box 471, Lindale, Georgia 30147-1027, fax 706/295-4276 or e-mail to: [email protected].
25 Thermoforming QUARTERLY These sponsors enable us to publish These sponsors enable us to publish Thermoforming QUARTERLY Thermoforming QUARTERLY
“FORMING EDUCATIONAL OPPORTUNITIES: GRANTS AND SCHOLARSHIPS OFFERED BY THE SOCIETY OF PLASTICS ENGINEERS – THERMOFORMING DIVISION”
The Thermoforming Division of SPE has produced a new six-minute DVD for educators. The DVD discusses the 13 matching equipment grants of up to $10,000 and how to apply for the grant. The 20 scholarships to college students are discussed and information is provided as how to apply for a scholarship. The Thermoforming Division of SPE has contributed over $150,000 in equipment grants and scholarships as of this date. The DVD is free of charge and available from SPE through Gail Bristol at 203-740-5447 or Gwen Mathis, Thermoforming Division, at 706-235-9298.
Thermoforming QUARTERLY 26 Thermoformers, have These sponsors enable us to publish Thermoforming QUARTERLY you discovered a forming tip that you are willing to share with your fellow formers? A time saver? Or a cost saver? Or something that will save wear and tear on your machine? Or your employees? Then the Forming TIPS
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27 Thermoforming QUARTERLY The Thermoforming Division Salutes a Pioneer Thermoformer … Glenn Blackburn
ost of Glenn Blackburn’s life was company was profitable and after years the Mdedicated to the Thermoforming plant grew to sales of $12 million. This Industry. His life ambition was to be a plant was Portage Plastics, later becoming veterinarian like his Dad. While Glenn was Portage Industries and finally Spartech only able to achieve an 8th grade education Plastics Portage facility. He hired many in a one-room school house before going people from outside of the plastics industry, to war, he enlisted in the army with hopes all of which became successful in the of receiving veterinarian training. His extrusion, thermoforming and compression hopes were dashed when horses were not molding industries. used during World War II. As a Staff In 1966, Mr. Blackburn was offered an Sergeant in the First Calvary Division of opportunity to become one-third partner in the Army, he served in Australia, New a small company in Winter Haven, Florida. Guinea, The Admiralty Islands, The His goal was to build machinery and Philippines and Japan. He was a liberator thermoformed plastic field boxes for the of the Japanese- held prison camp at the citrus industry. The company also did hand University of Santo-Thomas in Manila. lay-up of fiberglass for many different Fighting malaria that he had contracted products. With little or no money, 10 years Mr. Glenn Blackburn from the war made it difficult to work for soon slipped away as Mr. Blackburn technology and systems with customers as a period of time after the war. Upon developed a full line of containers for well as competitors. The doors of Progress returning to the United States, he worked agricultural use in harvesting and material Plastics were opened several times for and received training as a chemical handling. During this time the company seminars and tours for customers, bacteriologist. Working with groups in was reorganized several times as it tried to competitors and the local SPE chapter. Mr. companies such as BF Goodrich, find new markets in the South. Winter Blackburn was one of the founders of the Doebeckman and Dow Chemical, he Haven Plastics was dissolved in 1975 as Central Florida Chapter of SPE and assisted in the development of a plastic film Mr. Blackburn left his partners and formed encouraged his employees and others to that would be used to enhance the Artec Plastics, Rebel Plastics and join. longevity and storage of prepackaged Blackburn Industries. All of these Since the sale of Progress Plastics to cheese. Mr. Blackburn also worked on the companies carried on the agricultural line Triangle Plastics, Mr. Blackburn has been development of equipment to cut, slice and of formed containers while developing new enjoying an active retirement. He spends vacuum pack cheese precisely. Mr. markets. Mr. Blackburn was one of the first a lot of his time in his local community Blackburn obtained many patents during to develop a low profile wheeled refuse helping neighbors with home and garden his work. He received 13 claims, allowing container for municipal garbage pickup projects. He has returned to the Philippines the laminating and gluing of a mass of and installed this system into many cities Islands twice to visit WWII sites. He cartons all at one time by means of steam in the U.S. and as far away as Brisbane, frequently travels and speaks at Veterans and vacuum under precise timing and Australia. As Blackburn Industries grew, of Foreign War meetings. He has worked control. After two years of development the name was changed to Progress Plastics on his life memoirs from childhood days work, many pieces of equipment became Inc. Progress Plastics grew to be the largest through WWII. As one of the most available to the prepackaging industry. custom thermoforming company in the knowledgeable in the Thermoforming Some of the equipment was tested and put Southeast U.S. with 9 Rotary Industry, he is not wasting that talent either. to use in the sliced bacon department of thermoformers, several CNC routers, 13 Besides producing oil paintings and other Armour and Company. Mr. Blackburn compression molding presses and several arts and crafts with his wife Eunice, he still totally developed and directed the use of rotational molding machines. PPI had finds time to consult and help startup this equipment, which was the first to many reputable customers who chose companies as well as established produce marketable sliced bacon with a Progress Plastics because of the high thermoforming companies. Glenn has stairstep appearance. quality standards and immaculate plant that always been respected for coming up with During the 1950s, Mr. Blackburn was Mr. Blackburn demanded. His business a way to thermoform something when recognized and awarded the responsibility always had a competitiveness that was others said it had to be done by another to manage the operations of a small plastic fueled by ingenuity. Mr. Blackburn process. He is often called upon for his processing company in Portage, strongly believed in structured training of ideas in part, tool or process design. It Wisconsin. Only a few types of his employees. A five-year plan put wasn’t until after his retirement and in 2001 thermoplastic existed during those days. emphasis on specific training each year in that Mr. Blackburn was awarded a High Working long days and nights, he learned areas such as Safety, Quality, Efficiency School Diploma at a graduation ceremony fast and gained an education in plastic and Communications. Training took place for WWII Veterans. processing through trial and error. The continuously for skills in thermoforming Glenn’s three children – Dennis, Wanda challenge was immense with the company and other manufacturing methods. Mr. and Wendy – all live close to his central operating at a loss. One year later the Blackburn believed in sharing techniques, Florida home.
Thermoforming QUARTERLY 28 These sponsors enable us to publish These sponsors enable us to publish Thermoforming QUARTERLY Thermoforming QUARTERLY
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Some of Glenn Blackburn’s Accomplishments: 1. Developed a process for vacuum packaging and sealing of cartons of food products in stacks. 2. Worked with development of packaging films, Dow Chemicals (Saran Wrap), Doebeckman (Cellophane), B.F. Goodrich (Polyfilm). 3. Developed tooling and procedures for manufacturing a 5 gal. plastic pail liner. The material was .060 HDPE and a four cavity female mold with plug assist was used in this difficult project. 4. After other companies failed, Mr. Blackburn developed tooling and process to thermoform the 18” x 18” x 32” McDonald’s waste receptacle using a female mold. 5. Developed a method for impregnating anti-static solution onto HDPE extruded sheet prior to vacuum forming. This material was used to form several million trays for Johnson & Johnson and surpassed the required static decay factors. 6. Developed 7 thermoforming companies: Portage Plastics, Haines Industries, Winter Haven Plastics, Artec Plastics, Rebel Plastics, Blackburn Industries, and Progress Plastics. 7. Set up 2 different companies with equipment which included over 26 compression molding presses, blenders, extruders and other machining equipment to manufacture fiberglass flower pots as well as low- and high-voltage electrical housings. ■
29 Thermoforming QUARTERLY and formed the material around them,” Freeman says. Such secondary machining is a Thermoforming frequent means of executing com- plex part designs. For example, even though the thermoforming process with Style can only mold precise features on one side, additional structural sup- port and part nesting type features Technology can still be added to the back side advances have by bonding machined parts after increased forming. Vent openings on parts can designers’ be achieved by designing in deep drawn rib structures, then machin- flexibility. ing the openings off the backside. Freeman also refutes the myth that thermoformed parts cannot esigners who think that injec- strict part design to a more conser- achieve the same level of aesthetic Dtion molding is the only way vative style. quality of injected molded parts. to fabricate stylish plastic parts are A number of designers have al- “We not only can achieve injec- behind the times and need to take a ready gotten the message and are tion molding standards, we often ex- second look at thermoforming. working with Freetech to provide ceed them,” Freeman notes. “A While it’s true that thermoforming their customers with creative con- Class A finished, molded-in-texture, is ideal for large, flat parts, the cepts. For example, Lunar Design, thermoformed part generally looks capabilities of the process extend Palo Alto, California, has won five better than an injected molded part much farther, due to many technol- design awards from ID Magazine because we don’t have their issues ogy innovations and the availabil- for projects on which Freetech with swirls, sink marks, weld lines, ity of new sheet materials. thermoforms the enclosures. Frog gate marks, etc. On cars, plastic “There’s a huge amount of edu- Design, Sunnyvale, California, and bumpers and plastic lower side pan- cation that needs to take place Ziba Design, Portland, Oregon, have els are typically thermoformed be- among designers,” says Richard also each won a design award using cause we can consistently achieve Freeman, president of Freetech Plas- parts formed at Freetech. tics, Fremont, California. “I think “For the most part, we can du- we are just scratching the surface of plicate any part design that you can its potential.” do with injection molding,” Free- Freetech Plastics has been a man says. “We’ve never turned leader in stretching the design lim- away a customer because the part its of thermoforming and in devel- shape was too complex.” oping an approach that’s become Thermoforming also gives de- known as the West Coast Style of signers the freedom to use signifi- thermoforming. cantly fewer parts, notes Freeman, The West Coast Style concen- and new techniques are allowing trates on more dramatic shapes with them to do things they couldn’t do sweeping curves, deeper draws, before. For example, Freetech can larger undercuts, and the use of rib perform insert forming, which it structures. Because this approach re- does to produce the Xenogen enclo- lies on painting after forming, it sure (see photo on next page). This is an example of a pressure-formed eliminates the need to mold in tex- “For structural purposes, we in- grille that demonstrates the design flex- ibility that can now be achieved with ture and color, a need that can re- serted some machined corner blocks thermoformed parts.
Thermoforming QUARTERLY 30 “With a rotary machine and a four-up tool, we can get four shots a minute,” Freeman says. “You can- not get four shots a minute on large parts with injection molding.” So when should someone use thermoforming instead of injection molding? There’s not one simple an- swer. Volume plays a huge role, given the difference in tooling costs. Credence Kalos XW Testhead uses Lower volumes favor thermo- pressure formed enclosure parts that forming, since thermoforming tool- illustrate the curvaceous aesthetic representative of the West Coast style of ing costs are only 10 percent to 15 thermoforming. percent the cost of injection mold- ing tooling. the medical equipment segment be- Part complexity and shape are cause of the material’s high chemi- big factors, since they affect tool- cal resistance. ing costs. And, of course, size is im- Conventional thermoforming portant. Very large parts favor methods have long provided parts for commercial appliances such as Life Measurement’s Pea Pod air displace- thermoforming, while very small ment plethysmograph assesses infant parts favor injection molding, where refrigeration and vending machines, body composition. The top part of the machine enclosure is pressure formed by multi-cavity tooling can be used. For but the new techniques have also Freetech Plastics. medium sized parts, all the factors allowed thermoforming to provide innovative solutions in segments the Class A finish on a big part must be considered together: com- such as medical equipment, labora- where injection molding night not.” plexity, size, and volume. tory equipment, fitness equipment, Depending on a particular part Material choices also affect the business machines, and lawn and design and size, thermoforming can decision making process, since not garden equipment. Some manufac- often match, or even exceed, the all engineering resins are available turers of consumer electronics have productivity of injection molding by in the extruded sheet form that is even turned to thermoforming for using inline or rotary machines. used by thermoforming machines. However, resin suppliers con- the large housings used inprojection tinue to roll out new thermo- televion sets.Such parts were typi- formable materials every year. cally injection molded in the past. Available materials al- Thermoforming may not be the Xenogen Ivis 200 Laboratory Imaging System ready include the olefins, best route for every application, but also uses enclosure parts it should definitely be looked at first pressure formed at Freetech ABS, polycarbonate, ny- Plastics. lons, polyphenylene sul- on large parts. fide (PPS), and thermo- “The process has been too often plastic elastomerssuch as overlooked in the past,” Freeman DuPont’s Hytrel. Last says. “But it’s a process that design- year, DuPont also intro- ers need to be aware of and keep in duced a thermoformable their tool kit.” ■ version of its Delrin acetal. Freetech Plastics was Reprinted with the first company to dem- permission from onstrate the feasibility of Appliance Design magazine, thermoformed Delrin, which DuPont is aiming at copyright 2004.
31 Thermoforming QUARTERLY These sponsors enable us to publish Thermoforming QUARTERLY MARK YOUR CALENDAR! • • • 17th Annual Thermoforming Conference
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Thermoforming QUARTERLY 32 Society of Plastics Engineers MEMBERSHIP P.O. Box 403, Brookfield, CT 06804-0403 USA Tel: +1.203.740.5403 Fax: +1.203.775.8490 www.4spe.org ® APPLICATION Applicant Information
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Thermoforming QUARTERLY 36