![2.008x
Radiative heating of a plastic sheet
Lamp
Substrate
(to be formed)
h = thickness [m]
r = density [kg/m3]
cp = specific heat [J/kg-K]
a = total absorption coefficient of substrate [unitless]
plamp = lamp power [W/m2]
DT = temperature rise [K]](https://image.slidesharecdn.com/008xtf-compressed-161101220925/85/Thermoforming-MIT-2-008x-Lecture-Slides-33-320.jpg)
![2.008x
Radiative heating of a plastic sheet
h = thickness [m]
r = density [kg/m3]
cp = specific heat [J/kg-K]
a = total absorption coefficient
of substrate [unitless]
plamp = lamp power [W/m2]
DT = temperature rise [K]
theat =
ρhcp
aplamp
ΔT
Lamp
Substrate
(to be formed)
DT = 250 K
h = 1 mm
r = 1200 kg/m3
cp = 1200 J/kg-K](https://image.slidesharecdn.com/008xtf-compressed-161101220925/85/Thermoforming-MIT-2-008x-Lecture-Slides-34-320.jpg)
Thermoforming (MIT 2.008x Lecture Slides)
- 2. 2.008x What thermoformed object(s) have you used already today?
- 3. 2.008x What is thermoforming (process definition)? à Forming a sheet (typically a thermoplastic) by applying heat then pressure against a mold. Figure13.37fromFundamentalsofModernManufacturing(4thEdition)"by Groover.(c)JohnWiley&SonsInc.(2010).
- 4. 2.008x Vacuum thermoforming (vacuum forming, vacuforming) Excerpt from: https://www.youtube.com/watch?v=BqV_jsxD0UA http://formech.com/product/508fs/
- 5. 2.008x How is thermoforming similar to injection molding? à Both use heat and pressure to shape thermoplastics. How are thermoformed parts different from injection molded parts? à Thermoformed parts are typically thinner, and have less complex shapes then injection molded parts. à The dimensional quality (corners, edges) and tolerances of thermoformed parts are lower than injection molded parts.
- 6. 2.008x Agenda: Thermoforming § Basic equipment and process configurations § Polymer mechanics during thermoforming § Rate-limiting steps of thermoforming § The process window and design rules § Conclusion Extra: Other polymer forming processes
- 10. 2.008x Lego IM vs TF comparison
- 11. 2.008x The MIT 150 2.008 YoYo
- 12. 2.008x
- 13. 2.008x Thermoforming in the MIT shop
- 14. 2.008x Thermoforming in the MIT shop
- 15. 2.008x Thermoforming in the MIT shop Heater (also one above) Clamps Die (custom) Sheet
- 16. 2.008x
- 17. 2.008x What is different about this part? (hint: look at the surface features)
- 18. 2.008x Figures 13.36, 13.39 from Fundamentals of Modern Manufacturing (4th Edition) by Groover. (c) John Wiley & Sons Inc. (2010) Mechanical thermoforming Pressure thermoforming Clamps 2.008x
- 19. 2.008x Thermoforming: 3. Polymer mechanics during thermoforming
- 20. 2.008x How does the polymer stress-strain curve change with temperature? à Recall from IM: Glass transition and softening Figure 9.5 from Understanding Thermoforming (Second Edition) by J.L Throne. (c) Hanser, 2008. Increasing temperature ≈TgBreak Yield
- 21. 2.008x Temperature-dependent modulus of thermoplastic à Recall from IM: Glass transition and softening Figure 9.1 from Understanding Thermoforming (Second Edition) by J.L Throne. (c) Hanser, 2008.
- 22. 2.008x Implication: thermoforming temperature range Figure 9.6 from Understanding Thermoforming by J.L Throne. (c) Hanser, 2008. “Not too hot, not too cold. Just right.”Increasing temperature Forming range
- 23. 2.008x Demo: Stretching a thermoplastic Heat Heat Pull
- 24. 2.008x Where is the strain greatest? Figure 13.37 Fundamentals of Modern Manufacturing (4th Edition) by Groover. (c) John Wiley & Sons Inc. (2010).
- 25. 2.008x Where is the strain greatest?
- 26. 2.008x 0.394 mm 0.423 mm 0.290 mm R = 0.310 mm R = 0.201 mm 0.199 mm 0.154 mm 0.164 mm
- 27. 2.008x Generally, areas that touch the mold last are thinnest 0.394 mm 0.423 mm 0.290 mm R = 0.310 mm R = 0.201 mm 0.199 mm 0.154 mm 0.164 mm THICK AREAS THIN CORNERS AND EDGES The area that stretched the most to reach the bottom is the thinnest.
- 28. 2.008x Simulation of TF (ANSYS): predicts strain and thickness distribution “For thermoforming a medical device package” from http://www.ansys.com/Industries/Materials+&+Chemical+Processing/Polymer+Processing/Thermoforming (left) finite element mesh automatically refined to capture mold curvature details (right) predicted thickness distribution
- 29. 2.008x Thermoforming: 4. Rate limits and continuous processing
- 30. 2.008x What limits the rate of thermoforming? § Heating (à radiative transfer) § Stretching (à viscoelasticity) § Cooling (à contact with cold mold; see IM analysis) Video: https://www.youtube.com/watch?v=YQ-s1BILiag
- 31. 2.008x Radiative heating (infrared) Images from: http://heraeus-thermal-solutions.com/media/en/webmedia_local/media/pdfs/ir_basics_and_technology2014.pdf
- 32. 2.008x 0.2 mm thickness Images from: http://heraeus-thermal-solutions.com/media/en/webmedia_local/media/pdfs/ir_basics_and_technology2014.pdf
- 33. 2.008x Radiative heating of a plastic sheet Lamp Substrate (to be formed) h = thickness [m] r = density [kg/m3] cp = specific heat [J/kg-K] a = total absorption coefficient of substrate [unitless] plamp = lamp power [W/m2] DT = temperature rise [K]
- 34. 2.008x Radiative heating of a plastic sheet h = thickness [m] r = density [kg/m3] cp = specific heat [J/kg-K] a = total absorption coefficient of substrate [unitless] plamp = lamp power [W/m2] DT = temperature rise [K] theat = ρhcp aplamp ΔT Lamp Substrate (to be formed) DT = 250 K h = 1 mm r = 1200 kg/m3 cp = 1200 J/kg-K
- 36. 2.008x A continuous TF + packaging system (Ulma) Image from http://www.ulmapackaging.com/packaging-machines/thermoforming-and-blister/tfs-700 Video: https://www.youtube.com/watch?v=qC5KFpNnR_4
- 37. 2.008x Thermoforming: 5. Process window and design guidelines
- 38. 2.008x The thermoforming process window (P, T) Figure 9.8 from Understanding Thermoforming by J.L Throne. (c) Hanser, 2008.
- 39. 2.008x Pressure and temperature ranges (for pressure-controlled forming) Table 9.1 from Understanding Thermoforming (Second Edition) by J.L Throne. (c) Hanser, 2008.
- 40. 2.008x Thermoforming strains λ1/ λ2 = 1.28 λ1 = 1.50 λ1/ λ2 = 1.87 λ1 = 2.33 λ1/ λ2 = 4.01 λ1 = 5.17 λ1/ λ2 = 4.73 λ1 = 4.33 x1 x2 Draw ratio L1 L2 L0 Biaxial stretch ratio 5 cm 8 cm 10 cm ~ 2.03 Note, that DR = 1 for the sheet material prior to forming
- 41. 2.008x Areal draw ratios Figure 9.11 and Table 9.2 from Understanding Thermoforming (2nd Edition) by Throne. (c) Hanser, 2008.
- 42. 2.008x Additional TF design guidelines § Avoid sharp corners in mold (R ~2*thickness) or greater. § Use draft angle if possible. § No undercuts (unless multi-part tooling)! § When you want to simplify mold making, sharp corners are OK but beware of tearing. § For thin plastic, areal draw ratios >2:1 require careful optimization and suffer non- uniformity. Poor Design Good Design R = 2*t or greater t R Draft angle: ¼°min for female tooling 1°for male tooling
- 43. 2.008x Additional TF design guidelines Higher temperature: still cannot draw deep teeth; non-uniformity results Even higher temperature: tearing § Avoid sharp corners in mold (R ~2*thickness) or greater. § Use draft angle if possible. § No undercuts (unless multi-part tooling)! § When you want to simplify mold making, sharp corners are OK but beware of tearing. § For thin plastic, areal draw ratios >2:1 require careful optimization and suffer non- uniformity. Poor Design Good Design R = 2*t or greater t R Draft angle: ¼°min for female tooling 1°for male tooling
- 44. 2.008x Positive versus negative mold
- 45. 2.008x Comparison of surface profiles Positive mold Negative mold
- 46. 2.008x Pre-stretching to reduce thickness variation Figure 13.38 from Fundamentals of Modern Manufacturing (4th Edition) by Groover. (c) John Wiley & Sons Inc. (2010). https://www.youtube.com/watch?v=WJlXdb2zA0k
- 47. 2.008x Large TF tooling: car door panels
- 49. 2.008x What’s new (and coming soon)? § Bio-derived and biodegradable plastics § Formable fiber materials § Paper (complex product packaging) § Carbon fiber (dream of auto industry) For examples see: § http://vegware.com § http://www.billerudkorsnas.com/fibreform § http://www.darpa.mil/program/tailorable-feedstock-and-forming
- 50. 2.008x Reflection: the big four Injection Molding Thermoforming Rate High Greater (parts/time) Quality Good Less Cost Low (at high volume) Less ($/part, especially at lower volume) Flexibility Low (tooling cost high) Less: fewer shapes Greater: lower tooling cost
- 52. 2.008x How were these parts made? Image © Concept Sales Inc.
- 53. 2.008x Figure 19.1 from Kalpakjian and Schmid, Manufacturing Engineering & Technology (7th Edition) Polymer processing overall TP = thermoplastic TS = thermoset E = elastomer Plastic bottles Plastic bags à Same physics, different machine and product format
- 54. 2.008x Blow molding of plastic bottles Images: http://designtekplastics.com/tips/injection-molding-vs-blow-molding/, http://dtresource.com/images/what-is-stretch-blow- molding-300x210.jpg, http://dongkong.en.ec21.com/500ml_water_bottle_blow_mold--4844865_4844892.html Figure 13.32 from Groover, Fundamentals of Modern Manufacturing (4th Edition)
- 55. 2.008x Blow molding of plastic bottles Images: http://designtekplastics.com/tips/injection-molding-vs-blow-molding/, http://dtresource.com/images/what-is-stretch-blow- molding-300x210.jpg, http://dongkong.en.ec21.com/500ml_water_bottle_blow_mold--4844865_4844892.html Figure 13.32 from Groover, Fundamentals of Modern Manufacturing (4th Edition)
- 56. 2.008x Melt/Extruder (Like an IM machine) Rotating molds § 0.08 - 0.5 L containers (e.g., PP, HDPE) § Multimold wheel system (18-60 cavities) § Production rates of 7,500 - 30,000 bottles per hour (500kg/h)! Video of the machine: http://www.youtube.com/watch?v=u-eW2lrxrq0 Diagram and data from http://www.wilmingtonmachinery.com/media/pdf/small_bottle_insert.pdf Continuous process!
- 57. 2.008x How are trash bags made?
- 58. 2.008x Blown film extrusion Figure 13.16, Groover, Fundamentals of Modern Manufacturing (4th Edition)
- 59. 2.008x Figure 13.16, Groover, Fundamentals of Modern Manufacturing (4th Edition) Picture: https://www.hosokawa-alpine.com/film-extrusion/blown-film-lines/
- 60. 2.008x Figure 13.16, Groover, Fundamentals of Modern Manufacturing (4th Edition) https://www.hosokawa-alpine.com/film-extrusion/blown-film-lines/ https://images-na.ssl-images-amazon.com/images/I/61uTRra5KkL.jpg
- 61. 2.008x Rotational molding (‘Rotomolding’) Fig. 19.15, Kalpakjian and Schmid, Manufacturing Engineering and Technology Videos: https://www.youtube.com/watch?v=M0_l269cPvQ, https://www.youtube.com/watch?v=b619f-0QhEs
- 62. 2.008x References 1 Introduction Photo of Lunch Tray © St. Louis County, Minnesota. Photo of ATV by Vesa Minkkinen on Pixabay. This work is in the public domain. Photo of Fruit Container by Vedat Zorluer on Pixabay. This work is in the public domain. Photo of Refrigerator by US Consumer Product Safety Commission. This work is in the public domain. Positive Mold Vacuum Thermoforming: Figure 13.37 from "Fundamentals of Modern Manufacturing (4th Edition)" by Groover. © Wiley (2010). Image of Formech 508FS © Formech International Ltd. 2016. All Rights Reserved. 2 Process Equipment Basics Positive Pressure Thermoforming: Figure 13.36 from "Fundamentals of Modern Manufacturing (4th Edition)" by Groover. © Wiley (2010). Mechanical Thermoforming: Figure 13.39 from "Fundamentals of Modern Manufacturing (4th Edition)" by Groover. © Wiley (2010).
- 63. 2.008x References 3 Polymer Mechanics Stress-Strain vs. Temperature: Figure 9.5 from "Understanding Thermoforming (2nd Edition)" by Throne. © Hanser, 2008. Elastic Modulus vs. Temperature: Figure 9.1 from "Understanding Thermoforming (2nd Edition)" by Throne. © Hanser, 2008. Stress-Strain vs. Temperature: Figure 9.6 from "Understanding Thermoforming (2nd Edition)" by Throne. © Hanser, 2008. Book Cover: Denslow's "Three Bears" (1901) on read.gov: Library of Congress. This work is in the public domain. Positive Mold Vacuum Thermoforming: Figure 13.37 from "Fundamentals of Modern Manufacturing (4th Edition)" by Groover. © Wiley (2010). Image of ANSYS Simulation © 2016 ANSYS, Inc. All Rights Reserved. 4 Rate Limits Videos of Thermoforming and Sealing Packaging © ULMA Packaging, S.Coop. Images of Infrared Heating Process and Equipment © 2016 Heraeus Holding Video of TFS 700 Thermoforming Machine © ULMA Packaging, S.Coop.
- 64. 2.008x References 5 Process Window Stress-Strain vs. Temperature: Figure 9.8 from "Understanding Thermoforming (2nd Edition)" by Throne. © Hanser, 2008. Draw Ratio Diagram: Figure 9.11 from "Understanding Thermoforming (2nd Edition)" by Throne. © Hanser, 2008. Draw Ratios: Table 9.2 from "Understanding Thermoforming (2nd Edition)" by Throne. © Hanser, 2008. Video of Presuction © 2011-2015 EPW LLC Thermoforming with Prestretch: Figure 13.38 from "Fundamentals of Modern Manufacturing (4th Edition)" by Groover. © Wiley (2010). Image of Automotive Doors: © 2011-2015 EPW LLC 6 Conclusion Image of Carbon Fiber Manufacturing © Hearst Communications, Inc. Images of Paper Products © BillerudKorsnas AB
- 65. 2.008x References 7 Bonus Photo of Drinking Straws by User: Alexas_Fotos (Alexandra) via Pixabay CC0. This work is in the public domain. Photo of Water Bottles by User: PublicDomainPictures via Pixabay CC0. This work is in the public domain. Photo of Kayaks by User: vonpics via Pixabay CC0. This work is in the public domain. Photo of Trash Bag by User: cocoparisienne (Anja) via Pixabay CC0. This work is in the public domain. Photo of American Football by User: Hans (Hans Braxmeier) via Pixabay CC0. This work is in the public domain. Photo of Disposable Cup by User: rodrigolourenco (Rodrigo Lourenço) via Pixabay CC0. This work is in the public domain. Photo of Sprayer Tanks © Copyright 2016. Den Hartog Industries, Inc. Polymer Processing Overview: Figure 19.1 from Title: Manufacturing Engineering & Technology (7th Edition); Authors: Serope Kalpakjian, Steven Schmid; © Prentice Hall; (2013); Blow Molding: Figure 13.32 from Title: Fundamentals of Modern Manufacturing; Author: Mikell P. Groover; Publisher: Wiley; 4 edition (2010); ISBN: 978-0470-467002
- 66. 2.008x References Image of Bottle Blow Mold: Copyright ©1997-2016 EC21 Inc. All Rights Reserved. Photo of Injection Molded Parisons © Steven Daly. All Rights Reserved. Photo of Blow Molded Bottles ©2015 Design-tek Tool and Plastics Inc. Image of Blow Molding Machine © Wilmington Machinery. Image of Blow Molding Machine in Operation © Wilmington Machinery. Blow Film Extrusion: Figure 13.16 from Title: Fundamentals of Modern Manufacturing; Author: Mikell P. Groover; Publisher: Wiley; 4 edition (2010); ISBN: 978-0470-467002 Photo of Blow Film Extrusion Process © HOSOKAWA ALPINE Aktiengesellschaft. All Rights Reserved. Images of Hefty Garbage Bags © 1996-2016, Amazon.com, Inc. or its affiliates Rotomolding: Figure 19.15 from Title: Manufacturing Engineering & Technology (6th Edition); Authors: Serope Kalpakjian, Steven Schmid; Publisher: Prentice Hall; 6 edition (January, 2009); ISBN-13: 9780136081685 Video of Rotational Molding Machine © Reinhardt Rotomachines Video of Unmolding Rotational Molded Tank © Reinhardt Rotomachines