Investment Casting

Used to produce large numbers of high quality castings for aerospace and medical applications, investment casting uses a wax copy of the component, dipped (invested) in a ceramic slurry to produce a ceramic mould. The wax is then removed to leave the ceramic shell, into which molten metal is poured.

Also known as the lost wax process, Patterns of the castings to be made are moulded by injection of a special wax into a metal die. Cores of pre-formed ceramic may be incorporated into the wax patterns as they are moulded. The patterns are assembled into a cluster (often comprising tens or even hundreds of patterns) around a wax runner system. The ‘tree’ of patterns is then coated with 8-10 layers of a refractory material, each layer being dried or chemically cured before the next layer is applied.

The assembly is heated to remove the wax, then fired at high temperature to bond the refractory mould strongly. The hot mould is cast and when cool the mould material is removed by impact, vibration, grit blasting, high pressure water blasting or chemical dissolution leaving the castings, which are then removed from the runner system.

Used for special purpose parts and with specialised alloys, typical applications include Aircraft engine turbine blades, jewellery, medical implants, statues