Moulding

• What is moulding?

  Shaping or forming material into a specific shape or design.
• What are the different types of moulding?

  Blow moulding, press moulding, extrusion & injection
• What is blow moulding used for?

  To make a variety of complex hollow shapes such as bottles for fizzy drinks, tablets or sun cream lotion.
• What is the process of blow moulding?

  • A parison of material is extruded into an open mould
  • The two halves of the mould close and pinch the parison so no air can escape
  • Compressed air is blown into the parison until the material fills the shape of the mould
  • The formed shape drops out of the blow moulding machine when the two halves of the mould open
  • A new parison is extruded ready to start the procedure again
• What is press moulding used for?

  To create electrical wall sockets and plugs
• What is the process of press moulding?

  • Two halves of the mould are heated to a temperature that can soften the polymer
  • A preform of the polymer is placed into the void at the bottom of the mould. The preform's volume is slightly bigger than that of the void it needs to fill
  • The two halves of the mould are forced together using a hydraulic press
  • The two halves of the mould remain together until cross-linking of molecules has completed
  • The two halves of the mould open and the moulded product can be removed
• What is extrusion used for?

  To create UPVC window frames and plastic pipes used by plumbers
• What is the process of extrusion?

  • Granules or molten polymer is held in a hopper
  • It's then moved by an Archimedes screw along a heated tube, called the heating chamber
  • Once the polymer is melted it's pushed through a die mould, which forms the shape of the extrusion
  • Once the shaped of the extrusion is formed, the polymer is quickly cooled in a water chamber so that it can retain its shape
• What is injection moulding used for?

  Used to make toothbrush handles, laptop casings, computer mice, car interior consoles, buckets and chairs
• What is the process of injection moulding?

  • Granules of polymer are fed into a hopper, a pigment is added at this stage if a specific colour is needed
  • It's moved via an Archimedes screw along the heating chamber
  • Once the polymer has become melted, its pushed through into a mould with a hydraulic ram - the use of the ram ensures just enough material is injected into the mould each time
  • The polymer cools quickly in the mould and the two halves of the mould are opened and ejector pins push the formed object from the mould