Gravity Die Casting is a permanent mould casting process, where the molten metal is poured from a vessel or ladle into the mould. The mould cavity fills with no force other than gravity, filling can be controlled by tilting the die. Undercuts, and cavities can be incorporated into the component form with the use of sand cores. This process gives a good surface finish as well as better mechanical properties, both due to rapid solidification.
The casting process involves four basic steps explained below:
The die is heated and then sprayed with a refractory coating, and closed. The coating both helps control the temperature of the die during manufacture and it also assists in the removal of the casting.
Molten metal is then manually poured into the die, (although in some cases a machine can be used) and allowed to solidify.
The die is then opened and the cast parts either removed by hand or in some cases ejector pins are used on the mechanised machines.
Finally, the scrap, which includes the gate, runners, sprues and flash, is removed from the casting(s). The castings are then processed to remove sharp edges and excess material, then blast cleaned (if required) prior to despatch to the customer.