Gravity Die Castings
Gravity die casting (permanent mould casting) pours molten metal into a reusable metal mould under gravity alone, giving sound, dense castings with better accuracy and finish than sand casting. It is common for aluminium parts that need heat treatment or pressure tightness.
What it is
The metal die is preheated and coated, then filled from a ladle. Sand or metal cores can form internal passages. Slower, calmer filling than high-pressure casting results in less porosity, so parts can be heat treated (for example LM25-TF) and machined deeply.
Tooling is cheaper than pressure die casting, making gravity die suitable for medium volumes.
Typical applications
- Pump bodies and impellers
- Cylinder heads and pistons
- Pressure-tight housings and valves
- Wheels and structural parts
- Electrical and lighting components
Suitable materials
- Aluminium alloys (LM6, LM25, LM4)
- Brass and bronze
- Magnesium alloys
Points to consider
- Good for pressure-tight and heat-treated parts.
- Minimum walls around 3–4 mm; thinner walls favour pressure die casting.
- Draft angles of 1–3° are needed.
- Tooling cost sits between sand patterns and pressure dies.
Frequently asked questions
Why choose gravity die casting over pressure die casting?
It produces denser castings with less porosity that can be heat treated and are better for pressure-tight parts, with lower tooling cost.
Can gravity die castings be heat treated?
Yes. Alloys such as LM25 are commonly heat treated to improve strength.
What volumes suit gravity die casting?
Medium volumes, from hundreds to tens of thousands of parts a year.