Injection moulding is a manufacturing process for producing
parts from both thermoplastic and thermosetting plastic materials. Material is
fed into a heated barrel, mixed, and forced into a mould cavity where it cools
and hardens to the configuration of the cavity. After a product is designed,
usually by an industrial designer or an engineer, moulds are made by a mouldmaker
(or toolmaker) from metal, usually either steel or aluminum, and
precision-machined to form the features of the desired part. Injection moulding
is widely used for manufacturing a variety of parts, from the smallest component
to entire body panels of cars.
With injection moulding, granular plastic is fed by gravity from a hopper into a heated barrel. As the granules are slowly moved forward by a screw-type plunger, the plastic is forced into a heated chamber, where it is melted. As the plunger advances, the melted plastic is forced through a nozzle that rests against the mould, allowing it to enter the mould cavity through a gate and runner system. The mould remains cold so the plastic solidifies almost as soon as the mould is filled.
1. Granules of plastic powder (note the plastics listed above) are poured or fed into a hopper which stores it until it is needed.
2. A heater heats up the tube and when it reaches a high temperature a screw thread starts turning.
3. A motor turns a thread which pushes the granules along the heater section which melts then into a liquid. The liquid is forced into a mould where it cools into the shape (in this case a DVD storage unit).
4. The mould then opens and the unit is removed.