Sand casting: how it works, costs and design rules

Metal is poured into a mould made of compacted sand. It is the cheapest way to make large or heavy metal parts in small quantities: pump housings, machine bases, manifolds.

Typical tolerance

±1–3 mm

Quantities

1 to thousands

Lead time

3–8 weeks

Materials

Cast iron, steel, aluminium, bronze

How it works

A pattern of the part is pressed into sand to form a cavity, with sand cores for internal shapes. Metal is poured in, and after cooling the sand is broken away.

Benefits

• Large parts possible.
• Cheap patterns (wood, resin or 3D printed).
• Wide choice of alloys.

Limitations

• Rough surface and loose tolerances.
• Almost always needs machining afterwards.

What drives the cost

• Pattern and cores.
• Weight.
• Machining of functional faces.

Design rules

• Add draft of 1–3°.
• Walls typically at least 4–5 mm.
• Generous fillets everywhere.

Preparing your STEP file

• Send the finished part plus a cast version with machining stock.
• Specify machined faces, datums and casting tolerances (ISO 8062) on the drawing.

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