Aluminium Die Casting vs Gravity Die Casting
Pressure die casting vs gravity die casting for aluminium parts: wall thickness, volume, tooling cost, heat treatment and finish compared, with guidance on choosing.
By Sunmax Casting India Engineering TeamReviewed by [INSERT ENGINEER NAME, ROLE]5 min read
Both processes use a permanent metal mould, but they fill it very differently — and that changes cost, wall thickness and what you can do with the part afterwards.
The core difference
- Pressure (high pressure) die casting injects molten aluminium into a steel die at high speed and pressure.
- Gravity die casting pours molten aluminium into a permanent mould and lets gravity fill it.
Side-by-side comparison
| Factor | Pressure die casting | Gravity die casting |
|---|---|---|
| Wall thickness | Thin (typically 2–4 mm) | Thicker (typically 4 mm and above) |
| Cycle time | Short | Longer |
| Tooling cost | Higher | Lower |
| Economical volume | Medium to high | Low to medium |
| Surface finish | Very good as-cast | Good |
| Heat treatment (T6) | Not usually possible | Possible |
| Internal soundness | Some entrapped gas possible | Generally sounder |
| Dimensional repeatability | Excellent | Good |
When to choose pressure die casting
Choose pressure die casting when you need thin, light parts in volume — housings, covers, brackets, enclosures — and when as-cast detail and consistent dimensions reduce machining.
When gravity die casting is better
Gravity die casting suits thicker, structurally loaded parts that must be heat treated for strength, and programmes where volumes do not justify the higher die casting tool cost.
Questions to ask before deciding
- What is the annual volume over the life of the product?
- Does the part need heat treatment or very high ductility?
- Can walls be made thinner and more uniform?
- Are there pressure-tightness requirements?
- How much machining does the current design need?
If you are unsure, send the drawing to a die caster for a DFM review — the answer is usually clear once wall thickness, volume and heat-treatment needs are on the table.
Frequently asked questions
Is pressure die casting cheaper than gravity die casting?
Per part, usually yes at medium to high volumes because cycle times are much shorter. Tooling for pressure die casting costs more, so at low volumes gravity casting can be cheaper overall.
Can I convert a gravity casting to pressure die casting?
Often, if the walls can be made thinner and more uniform and the part does not need conventional heat treatment. A DFM review will show what must change.