Investment casting: how it works, costs and design rules

A wax copy of the part is coated in ceramic, the wax is melted out and metal is poured into the shell. It makes accurate, complex parts in steels and superalloys that are hard to machine.

Typical tolerance

±0.1 mm per 25 mm

Quantities

50 to tens of thousands

Lead time

6–12 weeks

Materials

Carbon and stainless steel, tool steel, nickel alloys, bronze, titanium

How it works

Wax patterns are injected into a mould (or 3D printed for small batches), assembled on a tree, dipped in ceramic slurry, dried, de-waxed and fired. Metal is poured in and the shell is broken off.

Benefits

• Complex shapes close to the final part.
• Almost any alloy.
• Good surface finish and fine detail.

Limitations

• Wax tooling cost.
• Longer lead time than machining.
• Size limited to about 1 m.

What drives the cost

• Wax tool, part weight and alloy.
• Cores for internal shapes.
• Machining of critical features.

Design rules

• Keep sections uniform and avoid heavy blocks next to thin walls.
• Allow 1–2 mm machining stock on precision faces.

Preparing your STEP file

• Send the final part; the foundry adds shrinkage and gating.
• Mark machined faces and datums on the drawing.

See also the full STEP export checklist and the comparison of all processes.