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Investment Casting Processes

October 17,2019

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Wax Pattern Making

Wax replicas of the desired castings are produced by injection moulding using a metal die.

 

Wax Pattern Assembly

These patterns are attached via a "gate" to a central wax stick, referred to as a "tree" or "sprue", to form a casting cluster or assembly, and mounted on a pouring cup.

 

Shell Making

A shell is built by immersing the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand. Several layers may be applied in this manner.

 

Dewaxing

Once the ceramic is dry, the wax is melted out in an autoclave, creating a negative impression of the assembly within the shell. The shell mould is then fired in a high temperature oven.

 

Melting &Pouring

The shell is filled with molten metal using various techniques and, as the metal cools, the parts, gates, tree and pouring cup become a solid casting.

 

Knock out & Cleaning

When the metal has cooled and solidified, the ceramic shell is broken off by vibration or water blasting.

 

Cutting

The parts are cut away from the central tree using a high speed friction saw.

 

Finishing

Minor finishing operations, such as fettling and grinding, are undertaken to produce a metal casting identical to the original wax pattern. 


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