Gravity Die Casting
Gravity die casting uses a permanent metal mould. The casting and the related casting system must have a discharging capacity so that the casting can be removed from the metal mould. The mould consists of two halves that are pressed against each other with compressed air cylinders. During the casting process, the liquid aluminium is poured into the mould from above and the mould cavity is filled under the influence of gravity. That is why the process is called Gravity Die Casting.
Gravity die casting is often performed by hand, but it can also be fully or partially mechanised. Sand moulds or discharging metal moulds are used for the shapes of internal cavities. The strength of the gravity die casting can also be increased by means of heat treatment.
ADVANTAGES OF GRAVITY DIE CASTING
+ The availability of a permanent casting mould. This enables you to avoid the costs of the raw materials for processes such as sand casting and precision casting, which require that for every new casting the mould is destroyed and manufactured anew.
+ The casting has good dimensional accuracy, so it requires very little finishing.
DISADVANTAGES OF GRAVITY DIE CASTING
– Time-consuming production process
– High initial costs of the mould
– Low production speed. This is because the mould is out of action during the time needed for the casting to solidify, to remove it from the mould, clean the mould and, where necessary, supply new moulds.
USE OF GRAVITY DIE CASTING
Gravity die casting is generally used for small and relatively simple castings. Gravity die casting is less accurate than lost-wax casting, but if the mould halves are kept in good condition, good dimensional accuracy and a smooth product surface are possible.
With gravity die casting, the costs of the mould are around 30% lower than with high pressure die casting, but the product costs are 30% to 50% higher.
However, with a sufficiently high number of castings, gravity die casting is cheaper than sand casting despite the higher tool costs.