Gravity die casting and it's process, advantages and disadvantages.

Gravity Die Casting:

•        Gravity die casting or permanent mould casting is a casting process in which the molten metal is poured into a metallic mould called die under the influence of gravity

•        Hence the name 'gravity die casting

•        The mould or die is usually made from cast iron, tool steel, graphite, copper or aluminum alloys and the choice for a particular material depends on the type of metal to be cast

•        Gating and risering systems are machined either in one or both the mould halves. Figure shows a permanent mould made in two halves which resembles a book. The mould halves are hinged and can be clamped together to close the mould.

Steps involved in the process:

•        The mould is cleaned using wire brush or compressed air to remove dust and other particles from it

•        It is preheated to a temperature of 200 - 280°C by gas or oil flame and then the surface is sprayed with a lubricant

•        The lubricant helps to control the temperature of the die thereby increasing its life and also assist in easy removal of solidified casting

•        The mould is closed tightly and the liquid metal of the desired composition is poured into the mould under gravity

•        After the metal cools and solidifies, the mould is opened and the casting is removed. Gating and riser systems are separated from the cast part

•        The mould is sprayed with lubricant and closed for next casting. The mould need not be preheated since the heat in the previous cast is sufficient to maintain the temperature.

Advantages:

• Good surface finish and close dimensional tolerances can be achieved

     • Suitable for mass production

     • Occupies less floor space

     • Thin sections can be easily cast

• Eliminates skilled operators

Disadvantages:

•Initial cost for manufacturing moulds (dies) is high

     • Not suitable for steel and high melting point metals/alloys

     • Un-economical for small productions