Gravitech

Aluminium Die casting at Gravitech

Die casting is the process of forcing molten metal under high pressure into mold cavities (which are machined into dies).

There is a furnace in which the aluminium is heated at a high temperature till it reaches a molten state. It is mixed with a substance that cleans the aluminium and brings the pure aluminium on top.

First the mold is closed. Then a ladle is used to collect the hot molten aluminium form the furnace and pour it into the mold cavity. After it cools down and solidifies (takes a minute or two) the die is opened again and the item is ready. Finally, the scrap, which includes the gate and runners, must be separated from the casting. This is done by hand or by sawing, in which case grinding is necessary to smooth the scrap marks. This scrap is recycled by re-melting it.

The mold is made of two parts which can be closed using nuts and bolts. While opening these have to be taken out and the mold is hit with a chisel in order to apply pressure to separate the two parts.

The entire cavity is required to fill before any part of the casting solidifies. Otherwise it creates discontinuities if the shape requires difficult-to-fill thin sections. There is a problem of air entrapment, because when the mold is filled quickly there is little time for the air to escape. This problem is minimized by including vents along the parting lines.

The die casting method is especially suited for applications where a large quantity of small to medium sized parts are needed with good detail and a fine surface quality.