Casting and moulding

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

Nächster

Casting and moulding

Beschreibung

Zusammenfassung der Ressource

ähnlicher Inhalt

	Erstellt von fampulli vor mehr als 11 Jahre