Lost Foam Casting

A variation of the investment casting process, the pattern in lost foam casting is made of expanded polystyrene, dipped (invested) in a ceramic shell. Design flexibility is a key feature of this process, which lends itself to large castings, complex shapes and low part numbers.

Pre-forms of the parts to be cast are moulded in expanded polystyrene (or other expandable polymers) using aluminium tooling. Gluing EPS mouldings together can form complex shapes. The pre-forms are assembled into a cluster around a sprue then coated with a refractory paint. The cluster is invested in dry sand in a simple moulding box and the sand compacted by vibration. Metal is poured, vaporising the EPS pre-form and replacing it to form the casting.

Typical applications include large pumps, valve bodies, ship propellers, large engineering castings