Full-mold casting is a technique similar to investment casting, but instead of wax as the expendable material, polystyrene foam is used as the pattern. The foam pattern is coated with a refractory material. The pattern is encased in a one-piece sand mold. As the metal is poured, the foam vaporizes, and the metal takes its place. This can make complex shaped castings without any draft or flash. However, the pattern cost can be high due to the expendable nature of the pattern.
Minimum wall thicknesses are 2.5 mm, tolerances can be held to .3 % on dimensions. Surface finish can be held from 2.5µm to 25µm (0.1µin to 1.0 µin) rms. Size limits are from 400 g (1 lb) to several tons. No draft allowance is required.
Typical materials that can be cast with this process are aluminum, iron, steels, nickel alloys, copper alloys. Types of parts that can be made using these processes are pump housings, manifolds, and auto brake components.