PERMANENT MOULD CASTING:
For large-scale production, making a mould, for every casting to be produced, may be difficult and expensive. Therefore, a permanent mould, called the die may be made from which a large number of castings can be produced. , the moulds are usually made of cast iron or steel, although graphite, copper and aluminium have been used as mould materials. The process in which we use a die to make the castings is called permanent mould casting or gravity die casting, since the metal enters the mould under gravity. Some time in die-casting we inject the molten metal with a high pressure. When we apply pressure in injecting the metal it is called pressure die casting process.
Adv: fine casting
Good surface finish
Close dimensional tolerance
Small core holes
Limitation: limited size
Not for complicated shapes
High cost
Not for all materials
Application: automobile piston
Gear blanks
Connecting rods
Aircraft fittings
For large-scale production, making a mould, for every casting to be produced, may be difficult and expensive. Therefore, a permanent mould, called the die may be made from which a large number of castings can be produced. , the moulds are usually made of cast iron or steel, although graphite, copper and aluminium have been used as mould materials. The process in which we use a die to make the castings is called permanent mould casting or gravity die casting, since the metal enters the mould under gravity. Some time in die-casting we inject the molten metal with a high pressure. When we apply pressure in injecting the metal it is called pressure die casting process.
Adv: fine casting
Good surface finish
Close dimensional tolerance
Small core holes
Limitation: limited size
Not for complicated shapes
High cost
Not for all materials
Application: automobile piston
Gear blanks
Connecting rods
Aircraft fittings
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