Investment Casting Process

STAGE 1

The first stage of the PICAST process is to produce an exact replica (or “pattern”) of the required casting. This is made by injecting wax into a die.

Aluminium dies are used, which are economical to make and easily modified if design changes are required. Loose pieces may be used to form any undercuts and internal detail.

STAGE 2

The wax pattern is assembled onto a wax feeder system. Each assembly or “tree” may have just one large pattern or many small patterns.

STAGE 3

The wax assembly is dipped into high-grade ceramic slurry by a large robot.

This is the most important coating as the metal will lie next to it when poured into the mould.

STAGE 4

Whilst the thin coating is still wet, larger particles of ceramic are dropped onto the wet surface, to build up a thicker coat. After drying, this coating process (or “investment” process) is repeated several times, building a shell mould thickness of approximately 10mm.

STAGE 5

After the final shell mould is dried, the wax is melted out in a steam autoclave, hence the name “lost-wax process”. The moulds are fired at over 1000°C to remove any remaining wax and to strengthen the mould.

STAGE 6

Molten metal is poured into the moulds whilst they are still hot, enabling the metal to run into thin wall sections.

STAGE 7

After cooling, the ceramic shell mould is broken away and each casting is cut away from the feeder system.

STAGE 8

The castings are carefully fettled, blasted and heat-treated. Setting operations may also be required. Material testing, x-ray, dye penetrant or machining can then be carried out, if this is required.