PRECESSION INVESTMENT CASTING:
The investment casting process also called lost wax process begins with the production of wax replicas or patterns of the desired shape of the castings. A pattern is needed for every casting to be produced. The patterns are prepared by injecting wax or polystyrene in a metal dies. A number of patterns are attached to a central wax sprue to form an assembly. The mould is prepared by surrounding the pattern with refractory slurry that can set at room temperature. The mould is then heated so that pattern melts and flows out, leaving a clean cavity behind. The mould is further hardened by heating and the molten metal is poured while it is still hot. When the casting is solidified, the mould is broken and the casting taken out.
The basic steps of the investment casting process are:
1. Production of heat-disposable wax, plastic, or polystyrene patterns
2. Assembly of these patterns onto a gating system
3. “Investing,” or covering the pattern assembly with refractory slurry
4. Melting the pattern assembly to remove the pattern material
5. Firing the mould to remove the last traces of the pattern material
6. Pouring
7. Knockout, cut off and finishing.
Adv: complex shapes, very fine details, close tolerance, better surface finish, no machining
Limitation: size and mass – maximum 5 kg
The investment casting process also called lost wax process begins with the production of wax replicas or patterns of the desired shape of the castings. A pattern is needed for every casting to be produced. The patterns are prepared by injecting wax or polystyrene in a metal dies. A number of patterns are attached to a central wax sprue to form an assembly. The mould is prepared by surrounding the pattern with refractory slurry that can set at room temperature. The mould is then heated so that pattern melts and flows out, leaving a clean cavity behind. The mould is further hardened by heating and the molten metal is poured while it is still hot. When the casting is solidified, the mould is broken and the casting taken out.
The basic steps of the investment casting process are:
1. Production of heat-disposable wax, plastic, or polystyrene patterns
2. Assembly of these patterns onto a gating system
3. “Investing,” or covering the pattern assembly with refractory slurry
4. Melting the pattern assembly to remove the pattern material
5. Firing the mould to remove the last traces of the pattern material
6. Pouring
7. Knockout, cut off and finishing.
Adv: complex shapes, very fine details, close tolerance, better surface finish, no machining
Limitation: size and mass – maximum 5 kg
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