AS - Graphics - Structural Foam

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AS-Level ­ Graphics ­ Structural Foam
This is a low pressure injection moulding process which process thermoplastics to create mostly
used to create large structural parts. Unlike other processes this requires low pressure and most
moulds are produced using aluminium.
How Is It Done?
The molten plastic is injected into a mould (which would be created from aluminium) after being
mixed with a blowing agent or high pressure gas. This then produces bubbles in the plastic causing it
to foam. The foam retains the properties of the plastic but it weighs less because of reduced density.
The plastic is injected at about 500°F then rapidly cooled to between 100 and 140°F. Once released
form the mould, naturally the part will deform from the mould shape due to the stress of the cooling
process. Therefore dimensions need to be thought about as the mould will have to be bigger than
the final product so that when it deforms it will end up the right size. The size difference will vary, it
depends on:
- Size of the machine
- Size of the mould
- Degree/ Direction of flow
- Movement of material in the mould
- Thickness of the mould sections
- Size of the nozzle
Made By Richard Francis - http://getrevising.co.uk/members/richard_francis1

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Properties:
Structural Foam uses low pressure which unlike conventional injection moulding which uses extreme
high pressure to force the materials into the cavities.
Compared structural foam takes advantage of a parts configuration; it's generally thick wall sections,
and then the foaming action within the resin blend. To allow the molten resin to flow much further,
with far less pressure, then the typical process would allow.…read more

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