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Casting and moulding
- these processes can be used to make 3D parts in a single operation
- all involve some form of mould in the shape of the desired product
- they also all involve a change in state of the material used
- e.g allowing a liquid to set or cool, forming a solid
- e.g allowing a liquid to set or cool, forming a solid
- they also all involve a change in state of the material used
- all involve some form of mould in the shape of the desired product
- metal casting
- melted metal is poured into moulds
- and allowing it to cool
- can be used to make complicated 3D shapes
- can be used to make complicated 3D shapes
- and allowing it to cool
- sand casting
- mould is made form sand, with an added bonding agent
- the shape needed is pressed into the sand and then removed, leaving a shape for the metal to fill
- each mould is only used once
- the sand is shaken off the cast product after it has been soilidified
- over 70% of castings are made from sand casting
- iron is often cast using sand eg for car engine parts
- iron is often cast using sand eg for car engine parts
- the sand is shaken off the cast product after it has been soilidified
- each mould is only used once
- the shape needed is pressed into the sand and then removed, leaving a shape for the metal to fill
- mould is made form sand, with an added bonding agent
- die casting
- where lots of products are to be made
- car door handles, camera bodies
- car door handles, camera bodies
- moulds typically made from steel
- can bes used again and again but are very expensive to make
- can bes used again and again but are very expensive to make
- metals cast by this process must have a low melting point eg
aluminium and zinc, pewter
- where lots of products are to be made
- melted metal is poured into moulds
- if a large number of plastic products are to be made
- injection moulding
- used to make many different plastic parts
- injection moulding uses an expensive metal die
- the die might contain space for many small parts, or one large part
- the die might contain space for many small parts, or one large part
- plastic is injected into the mould under pressure
- only used with thermoplastics!
- process
- 1) Raw material: granules of thermoplastic
- these are fed into a hopper
- a rotating feed screw
- takes the granules through a heater where they are melted
- when enough melted plastic has reached the shot chamber, the feed screw is rammed forward
- this injects the plastic into the die under pressure
- after the plastic has cooled the mould is opened to release the finished mouldings
- after the plastic has cooled the mould is opened to release the finished mouldings
- this injects the plastic into the die under pressure
- when enough melted plastic has reached the shot chamber, the feed screw is rammed forward
- takes the granules through a heater where they are melted
- a rotating feed screw
- these are fed into a hopper
- may be repeated many time a minute
- 1) Raw material: granules of thermoplastic
- used to make many different plastic parts
- injection moulding
- extrusion process
- used to make continuous lengths of thermoplastic product
- eg pipes/ guttering
- alos used to provide parison used in blow moulding
- alos used to provide parison used in blow moulding
- eg pipes/ guttering
- lie injection, uses a hopper, heating chamber and rotating feed screw
- Melted thermoplastic is forced through a die
- it is not rammed to increase the pressure
- the extruded shape cools after leaving the die
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- Enter text here
- the extruded shape cools after leaving the die
- it is not rammed to increase the pressure
- used to make continuous lengths of thermoplastic product
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