Design guidelines for the thermoforming process 1 Design guidelines for product engineers on the thermoforming process U aangeboden door: Batelaan Kunststoffen BV ● Veerpolder 8 ● 2361KV Warmond T: 071-5613301 ● F: 071-5616701 ● www.batelaan.nl Zonder schriftelijke toestemming van de ProducentenVereniging Thermoplasten (PVT) mag niets uit deze informatiemap worden verveelvoudigd en/of openbaar gemaakt door middel van druk, fotokopie, microfilm of anderszins, hetgeen ook van toepassing is op de gehele of gedeeltelijke bewerking. Deze informatiemap is gebaseerd op de trainingmodules, gerealiseerd in het kader van T-ForM. Voor de eventuele aanwezigheid van (zet)fouten en onvolledigheden kan de PVT geen aansprakelijkheid aanvaarden. PVT, Postbus 420, 2260 AK Leidschendam, [email protected] www.t-form.eu July 2008 1 Design guidelines for the thermoforming process 2 Contents Contents ................................................................................................................................ 1 1. Executive Summary ........................................................................................................... 5 2. Introduction ........................................................................................................................ 9 2.1 Thin Sheet Thermoforming ........................................................................................... 9 2.2 Thick Sheet Thermoforming ....................................................................................... 10 2.3 Tooling ....................................................................................................................... 10 2.4 Literature .................................................................................................................... 11 3. Thermoforming process ................................................................................................... 15 3.1 Bubble Forming .......................................................................................................... 15 3.2 Cavity Forming ........................................................................................................... 15 3.3 Drape Forming ........................................................................................................... 17 3.4 Variations to Avoid Excessive Thinning ..................................................................... 18 3.4.1 Cavity Forming with Plug Assistance ................................................................... 18 3.4.2 Billow Drape Forming ........................................................................................... 19 3.4.3 Snap-Back Forming ............................................................................................. 19 3.4.4 Reverse Draw with Plug-Assist Forming .............................................................. 19 3.4.5 Twin Sheet Forming ............................................................................................. 19 3.4.6 Other Techniques ................................................................................................ 21 4. Tooling ............................................................................................................................. 23 4.1 Tooling Costs: Thermoforming versus Injection Moulding ........................................... 23 4.2 Tooling: Design Considerations .................................................................................. 23 4.2.1 Thermoforming Mould Design Criteria .................................................................. 24 4.3 Heat Transfer Considerations ..................................................................................... 26 4.3.1 Mould Temperature Control .............................................................................. 27 4.4 Tooling Materials ........................................................................................................ 27 4.1.1 Wood ................................................................................................................... 30 4.4.2 Plaster ................................................................................................................. 30 4.4.3 Sprayed Metal Alloys ........................................................................................... 31 4.4.4 Resin Tooling ....................................................................................................... 31 4.4.5 Aluminium ............................................................................................................ 33 4.4.6 Steel .................................................................................................................... 33 4.4.7 Russian Tooling Practice ..................................................................................... 33 5. Proprietary resins and resin based materials for tooling ................................................... 37 5.1 Axson EPO 4042 EPO4042/L Epoxy Casting Resin ................................................... 37 5.2 Epon Epoxy Resins .................................................................................................... 37 5.3 Fablite ........................................................................................................................ 38 2 Design guidelines for the thermoforming process 3 5.4 Polylite Polyester Resin .............................................................................................. 38 5.5 Metapor Epoxy/Aluminium .......................................................................................... 38 5.6 Espor .......................................................................................................................... 40 5.7 Vestalloy ..................................................................................................................... 40 5.8 WIS Tooling ................................................................................................................ 41 5.9 Albright RT ................................................................................................................. 41 5.10 Poly Steel ................................................................................................................. 41 5.11 Microsyn ................................................................................................................... 41 5.12 Ren-Shape (Vantico) ................................................................................................ 42 5.13 Polyurethane Machinable Slab (Ureol Board Axson) ................................................ 43 5.14 Epoxy / Aluminium using Stereolithography (Escuelo Technica)............................... 43 5.15 Miscellaneous Materials ........................................................................................... 43 6. Tooling: plug assistance................................................................................................... 47 6.1 Plug Assisted Thermoforming ..................................................................................... 47 6.2 Plug Materials............................................................................................................. 49 6.2.1 Acetal (e.g. Delrin) ............................................................................................... 52 6.2.2 Hardened Felt ...................................................................................................... 52 6.2.3 Syntactic foam ..................................................................................................... 52 6.2.4 Wood ................................................................................................................... 52 6.2.5 Resins .................................................................................................................. 52 6.2.6 “Hytac” Syntactic foams ....................................................................................... 52 6.3 Friction Between Plug and Sheet................................................................................ 54 6.4 Mould Plug and Heat Transfer .................................................................................... 62 6.5 Plug Assisted Forming Experimental Work ................................................................. 62 7. Computerised process simulation .................................................................................... 67 7.1 Background ................................................................................................................ 67 7.2 Forming feometries..................................................................................................... 70 7.3 Computer simulation literature summary .................................................................... 71 8. References ...................................................................................................................... 77 Appendix .............................................................................................................................. 80 Planoxal-50 Aluminium Data Sheet .................................................................................. 81 RenShape® BM 5055 ..................................................................................................... 83 EPO 4042 / EPO 4042/L .................................................................................................. 85 LAB 1001 ........................................................................................................................