VACUUM FORMING

VACUUM FORMING

1. Materials used

   • Acrylonitrile Butadiene Styrene (ABS)
   • Polyester Copolymer (PETG)
   • Polystyrene (PS)
   • Polycarbonate (PC)
   • Polypropylene (PP)
   • Polyethylene (sheet and foamed sheet) PE
   • Polyvinyl Chloride PVC
   • Acrylic PMMA

2. Products produced

   • Baths
   • Yoghurt Pots
   • Boat Hulls
   • Machinery Guards
   • Vehicle door liners
   • Refrigerator liners
   • Sandwich Boxes
   • Parts of vehicle cabs
   • Exterior shop signs

3. Nature of Use and Limitation

   • Use and Advantages
     • Low Cost: Low forming pressures
     • Inexpensive moulds/less time manufacturing
     • Prototypes, low quantity of large parts, medium size runs are therefore economical
     • For more continuous production of high volume: more sophisticated moulds+machines used
       • Yoghurt Pots
       • Disposable cups
   • Limitations
     • Requires a mould and extruded plastic sheets
     • Secondary process may be needed to trim formed sheet
       • trimmed waste can be re-ground + recycled

4. Process

   • Clamping
     • clamp frame to be powerful enough to hold plastic sheet during forming
     • Hold from 6mm to 10mm
     • Guarded + interlocked for automation
   • Heating
     • Uniformly located infra-red elements w/ aluminium reflective plate
     • Twin heaters and precise temperature readout are available for precision and speed
     • For higher temperatures use quarts heaters
   • Sheet Level
     • To stop sagging of plastic a photo electric beam scans just below and pumps air if it's broken
   • Pre stretch
     • Pre stretch after forming temp. reached
       • Done by making a 'bubble' of the plastic
     • Helps with minimum draft angles and high detail + even thickness
   • Vacuum
     • Vacuum sucks air from 'bubble'
   • Plug assist
     • A male plug tool that forces material into holes
     • Good for deep-draw moulds + no webbing
     • Made from resign (smooth and not conductor)
   • Cooling and release
     • Fans to speed up cooling (+spray)
       • Speed up by 30%
     • Temp controls
     • Release by reverse pressure form vacuum system
   • Trimming and finishing
     • Excess removed
     • Holes, slots and cut-outs drilled into part
     • Can also be painted/decorated and strengthened

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