Die casting: how it works, costs and design rules

Molten aluminium, zinc or magnesium is forced into a steel die at high pressure. It produces near-net-shape metal parts such as housings, brackets and covers in large volumes.

Typical tolerance

±0.1–0.3 mm as cast

Quantities

5,000 to millions

Lead time

8–16 weeks for the die

Materials

Aluminium (e.g. EN AC-46000), zinc (Zamak), magnesium

How it works

The die is clamped and liquid metal is injected in milliseconds. After solidifying, the casting is ejected, the runners are trimmed and critical faces are often machined.

Benefits

• Thin walls and complex shapes in metal.
• Very low unit cost at volume.
• Good as-cast surface finish.

Limitations

• Expensive dies.
• Porosity limits welding and pressure tightness.
• Not suitable for all alloys.

What drives the cost

• Die cost and number of slides.
• Secondary machining.
• Part weight.

Design rules

• Use uniform walls of 1.5–4 mm.
• Add draft of 1–2°.
• Use generous radii to help metal flow.
• Add machining stock only where faces are machined.

Preparing your STEP file

• Send the as-cast model and the machined model separately.
• Show machined faces and datums clearly on the drawing.

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