Die casting is an automated process that forms castings under high pressure in a metal mould. More details of the process can be found in the movie below:
Note: This animation requires Adobe Flash Player 8 and later, which can be downloaded here.
Typical items produced by die casting are toys and small precision parts such as sprockets and gears.
Aluminium, copper and zinc alloys are commonly used in die casting, ferrous alloys are harder to cast in this way as the moulds are made from hardened steel.
There are various methods of die casting;
- Gravity fed – Similar to permanent mould casting, the material is poured into the top of the mould & forced downwards by gravity.
- Pressure – The metal is forced into the mould under pressure.
- Cold chamber – Molten metal is poured into the system and then forced into the mould.
- Hot chamber – The metal is heated within the system & then forced from the crucible into the die.
- Squeeze – Similar to injection moulding, a given amount of material is forced into the mould.
- Very low unit cost.
- High definition & surface finish.
- Excellent dimensional accuracy.
- Cool metal mould gives fast solidification, leading to a fine grain structure.
- Can produce thin sections.
- A large capital investment is required to set up a die casting process.
- It is difficult to control the microstructure of the solid.
- The alloys used must have a low melting point, often at the expense of other properties, such as strength and stiffness.
- Cannot be used for complex shapes, as the casting couldn’t be ejected from the mould.
- Cannot be used for large castings.