Extrusion, compression and rotation moulding
Extrusion moulding uses a standard extrusion machine. Plastic particles are dropped into a hopper and a screw thread sends them past heaters making them melt. The screw thread then forces them through a nozzle which produces a shape called a parson. The parson is put into a mould and trimmed at the top and squashed at the bottom. Air is then blown down the parson so that it takes the shape of the mould.
The compression moulding process is a method of moulding in which preheated polymers are placed into an open heated mould cavity. The mould is closed with a top plug and pressure is applied to force the material to contact all areas of the mould. Throughout the process heat and pressure are maintained until the polymer has cured.
Injection moulding is a production process for producing large quantities of identical items. Granulated or powdered thermoplastic material is heated, melted and then forced under pressure into a mould. Once in the mould the material cools, forming a component that takes on thenshape of the mould cavity.
