Die casting is a precision casting technique that uses a permanent metal mould, or die, into which molten metal is poured directly. Metal is typically forced into the mould under pressure but gravity-feed systems are also used. Tooling costs and other capital costs are high due to the cost of designing dies. Operational costs, however, are relatively low, due to the high level of automation and the small number of production steps (i.e. direct pouring into a permanent mould rather than preparing destroyable patterns and/or moulds). The process, therefore, is best suited to mass production. Die casting is most suitable for non-ferrous metals with relatively low melting points (i.e. around 870oC) such as lead, zinc, aluminum, magnesium and some copper alloys (Luther, 1999).



Casing metals with high melting points, including iron, steel and other ferrous metals, reduces die life. Dies are usually made from two blocks of steel, each containing part of the cavity, which are locked together while the casting is being made. Retractable and removable cores are used to form internal surfaces. Molten metal is injected into the die and held under pressure until it cools and solidifies. The die halves are then opened and the casting is removed, usually by means of an automatic ejection system. The die is cleaned between each casting cycle, preheated and lubricated to reduce wear on the die, to improve surface quality and to aid ejection. Mould coating material can also be used to protect the molten metal from the relatively cool and conductive surface of the mould. Cooling systems are often used to maintain the desired operating temperature.