Moulding And Forming Flashcards
What is acrylics heating point to be bent without cracking ?
150- 170
What can vacuum formers be used for ?
Making mounds and housing electronic components
HIPS is often the material used
How does vacuum forming work ?
- HIPS is heated
- Once hot the solid former is pressed into the HIPS
- The vacuum is turned in removing air from the former
- The HIPS takes the form of the solid former
The solid shape into the vacuum is called a former, the hollow part that has been vacuum formed is the mould
Since polymers have a low melting point once molten how can they be shaped ?
Injection moulding
Extrusion
What is injection moulding used for ?
To produce mass produced polymer parts
How does injection moulding work ?
- Granular plastic held in a hopper
- Moved via an Archimedean screw along a heated tube called a heating chamber
- Once melted it is pushed into the mould with a hydraulic ram which ensures enough material is pushed in
- The mould is then cooked so that the noodles plastic can be removed
How does extrusion work ?
- Granular plastic held in hopper
- Moved by archamidean screw along a heated tube called the heating chamber
- Once polymer is meted it’s pushed through a die mould into the shape of the extrusion
- There is no hydraulic ram in this process so molten plastic can be feed through the die continuously
What are some examples of extruded polymers ?
Plastic pipes
Tubes
Guttering
What is blow moulding used for ?
To shape plastics like bottles, barrels and similar shapes
How does blow moulding work ?
- Parisian is inserted into a mould
- The base of the parison is squeezed by the mould
- Air is blown into the parison which expands to fill the mould
- The finished products is cooled and released from the mould
What is press moulding used to make ?
Electrical fitttinfs, handles and many other products
But only thermosetting plastics can be used
