Aluminium Gravity Casting

Aluminium gravity casting can also be referred to aluminium gravity die casting, chill casting or permanent mould casting.

The melted aluminium alloy is poured into the mould by means of gravity via a launder or ladle. The pouring rate is relatively low, yet the metal mould produces rapid solidification. Aluminium gravity casting can be operated either by hand or by gravity casting machines.

Advantage and disadvantages of aluminium gravity casting

  1. Aluminium gravity casting parts have excellent mechanical properties compared with die casting parts. Because aluminium gravity casting parts have lower gas porosity, the castings are generally sound, provided that the casting aluminium alloys used exhibit good fluidity and resistance to hot tearing. Besides, mechanical properties of permanent mould castings can be further improved by heat treatment
  2. Aluminium gravity casting is suited to high-volume production. Compared with aluminium sand casting process, aluminium gravity casting process uses permanent mould avoiding forming the sand shell moulds for each casting, thus saving considerable time for the casting process. Furthermore, aluminium gravity casting processes can be assisted by gravity casting machines, which can increase the production capacity dramatically.

Disadvantage of aluminium gravity casting:

  1. Low volume production compared with die casting.
    Compared with aluminium die casting process, aluminium gravity casting process has a lower production capacity. Even a gravity casting machine assisted process can not reach the high production capacity of the high pressure die casting process. In most aluminium gravity foundries, handwork is overwhelming. Thus a large order will require a much longer lead time than that of aluminium die casting process.
  2. High tooling cost compared with sand casting.
    Gravity casting can also be referred to metal mould gravity casting, for the solid metal moulds it use. Furthermore, the mould material used is expensive tool steel/iron. Compared with wooden or aluminium moulds for sand casting, a gravity casting mould is much expensive. Besides, if the mould is used for a gravity casting machine, ejection system, cooling system, and sprue system should be added to the mould. That also affects the cost.
  3. Minimum wall thickness possible is c. 3-5mm.

Gravity Images

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