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plastic_fabrication processes
The document discusses several common plastic fabrication processes: injection molding, extrusion, thermoforming, and blow molding. Injection molding uses heated plastic that is forced into a mold cavity to form parts. Extrusion uses heated plastic that is forced through a die to form continuous profiles. Thermoforming involves heating plastic sheets and forming them into shapes using molds, vacuum, or pressure. Blow molding uses either extruded plastic tubes ("parisons") or pre-formed plastic pieces ("preforms") that are inflated using air pressure in molds to form hollow parts. Each process has characteristic equipment, materials used, part geometries produced, and mold/die considerations.
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- 1. Ch 6 METBD 470 Chapter9 – Plastic and Polymer Composite Fabrication Processes 1. Injection Molding (or compression or transfer) 2. Extrusion 3. Thermo-Forming 4. Blow Molding (injection blow molding with preforms or extrusion blow molding with parison) 5. Rotational Molding (combination of 3 and 4)
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- 3. Ch 6 METBD 470 MoldingProcesses for PE: Molding Processes for Nylon (30% GF):
- 4. © MFA andDC 2005 Desired Batch Size Screen on batch size* *Using the CES EduPack Level 2 DB Economicbatchsize(units) 1 10 100 1000 10000 100000 1e+006 1e+007 1e+008 Blow Moulding Powder methods Injection Moulding Sheet forming Die Casting Compression Moulding Expanded foam molding Rotational Moulding Rolling and forging Resin transfer molding (RTM) Electro-discharge machining Thermoforming Rapid prototyping Lay-Up methods Sand casting Polymer Casting Economic batch size Demo: the Process data-table
- 5. Ch 6 METBD 470 YouTube Videos: Blow Molding: http://www.youtube.com/watch? v=vSabFFQUr9E&feature=related Extrusion: http://www.youtube.com/watch?v=kpPS6S_EB4Q Injection: http://www.youtube.com/watch?v=bit- D1NnfjI&videos=BeAyHeQIsiY&playnext_from=TL&playnext=1 Thermoforming: http://www.youtube.com/watch?v=NPLWxxyIJcE
- 6. Ch 6 METBD 470 •Injection Molding – most common (60-70%) – Process Plastic pellets are heated in the injection unit and forced through a runner system/gate(s) into a cavity in a mold. Batch Process
- 7. Ch 6 METBD 470 •Injection Molding – Equipment • Clamping Unit (Ejection System) • Injection (Plasticating) Unit • Frame
- 8. Ch 6 METBD 470 •Injection Molding –Main functions of Plasticating unit 1.Convey solid material/melt 1.Mix to produce homogeneous melt 1.Melt material – Range of 300º F (PVC) to 740º F (Polysulphone) 1.Develop pressure for injection
- 9. Ch 6 METBD 470 •Injection Molding –Materials •Both amorphous and semi-crystalline are done easily •Narrow molecular weight distribution •With modifications to the equipment – thermoset materials and liquid Silicone can be used
- 10. Ch 6 METBD 470 •Injection Molding –Parts •Three dimensional •Can be very complex •Multiple cavitation is common (128 cavities)
- 11. Ch 6 METBD 470 •Injection Molding –Tooling - Molds •Generally steel, but some Aluminum tooling is used •High pressure process – molds are ‘beefy’ – Plastic pressures around 30,000 psi – Weight – LXWXH/4 (in inches) •Tooling is expensive and can take a long time to create
- 12. Ch 6 METBD 470 •Extrusion –Process Plastic pellets or powders are heated in a plasticating unit and the melt is forced through a forming die. Continuous Process
- 13. Ch 6 METBD 470 •Extrusion – Equipment • Injection (Plasticating) Unit • Frame
- 14. Ch 6 METBD 470 •Extrusion –Materials •Both amorphous and semi-crystalline are done easily •Wide molecular weight distribution
- 15. Ch 6 METBD 470 •Extrusion –Parts •Two dimensional – Sheet – Hoses – Line – Rod – Vinyl siding – Pipes
- 16. Ch 6 METBD 470 •Extrusion –Tooling - Dies •Generally steel – Aluminum is common though •Low pressure process – Tooling can be expensive – Shorter lead times
- 17. Ch 6 METBD 470 •Thermoforming –Process Sheet is heated and formed to the desired shape Can be a batch or continuous process Some consider Thermoforming to be a secondary process because the material needs to be formed into sheet prior to being thermoformed.
- 18. Ch 6 METBD 470 •Thermoforming –Process
- 19. Ch 6 METBD 470 •Thermoforming –Process
- 20. Ch 6 METBD 470 •Thermoforming –Process
- 21. Ch 6 METBD 470 •Thermoforming – Equipment • Heating unit • Vacuum unit • Tool or die
- 22. Ch 6 METBD 470 •Thermoforming –Materials •Both amorphous and semi-crystalline are done – Semi-crystalline are more difficult •Wide molecular weight distribution
- 23. Ch 6 METBD 470 •Thermoforming –Parts •Three dimensional •Generally simple shapes
- 24. Ch 6 METBD 470 •Thermoforming –Tooling – Dies or molds •Generally Aluminum, but prototypes are commonly made epoxy, wood, plaster, and composite materials •Low pressure process – Tooling is relatively inexpensive – Shorter lead times
- 25. Ch 6 METBD 470 •Blowmolding –Process –2 basic types •Extrusion Blow Molding –consists of an extruder that melts the plastic and forms it into a molten tube called a parison. Die closes around parison which seals both ends. Blow pin is insereted and inflates the parison to assume the contoru of the die. See http://www.youtube.com/watch? v=RcXB0NbbQzg&feature=related •Injection Blow Molding (large volumes) –Uses preforms - The preform is transferred on a metal shank, called the core rod and into a blow mold.
- 26. Ch 6 METBD 470 BlowmoldingEquipment • Depends on type of blowmolding you are doing – Extrusion » Extruder » Dies and Blowpins » Clamping system – Injection » Preforms (Injection molding machine) » Heating unit » Blowing machine
- 27. Ch 6 METBD 470 •Blowmolding –Materials •Both amorphous and semi-crystalline are done – Semi-crystalline are more difficult – Highly Crystalline materials (Nylon) are very difficult •Wide molecular weight distribution
- 28. Ch 6 METBD 470 •Blowmolding –Parts •Three dimensional •Generally simple shapes •Hollow •May need trimmed
- 29. Ch 6 METBD 470 •Blowmolding –Tooling – Dies or tools •Generally Aluminum (some may have brass inserts) – Steel Pinchoff areas •Low pressure process – Tooling is relatively inexpensive – Shorter lead times