Casting
Die Casting vs Permanent Mold Casting
Die casting injects molten aluminum or zinc into a steel die at 1,500 to 25,000 psi. Permanent mold casting gravity pours metal into a reusable iron or steel mold. You trade tooling money for cycle speed: die cast tools cost 3 to 5 times more but cycle in under a minute.
| Die Casting | Permanent Mold Casting | |
|---|---|---|
| Tooling cost | $40,000 to $150,000 H13 steel die | $15,000 to $35,000 iron or steel mold |
| Cycle time | 30 to 60 s | 3 to 6 min |
| Minimum wall thickness | 1.0 to 2.5 mm | 3.5 to 5 mm |
| Tolerance | ±0.1 mm on first 25 mm | ±0.4 mm on first 25 mm |
| Surface finish | Ra 1 to 2.5 µm as cast | Ra 3 to 6 µm as cast |
| Heat treatability | T5 only, gas porosity blisters at T6 | Full T6 solution treat capable |
| Economic volume | 10,000+ parts/yr | 500 to 10,000 parts/yr |
Choose Die Casting when
- Annual volumes above 10,000 parts
- Walls under 2.5 mm or thin complex ribs
- Net shape features that eliminate machining
Choose Permanent Mold Casting when
- Pressure tight or T6 heat treated parts
- Runs of 500 to 10,000 pieces
- Tooling budget under $40,000
The verdict
Above roughly 10,000 parts per year, die casting wins on unit cost and thin walls. Choose permanent mold for runs of 500 to 10,000 parts, pressure tight castings, T6 heat treatment, or walls over 4 mm. If porosity or weldability matters, permanent mold is the safer default.
Cost comparison
A single cavity die cast tool for a 1 kg aluminum housing runs $50,000 to $120,000; the equivalent permanent mold runs $15,000 to $35,000. At 45 second cycles versus 4 minute cycles, die casting drops machine and labor cost per part from roughly $4 to under $1.50. Crossover typically lands between 8,000 and 15,000 pieces. Below that, the permanent mold amortizes better despite the slower cycle, and it keeps the T6 option open.
Common questions
Can die castings be heat treated to T6?
Usually not. Conventional high pressure die castings trap gas that blisters at solution treatment temperatures around 985 F, so they are limited to T5 aging. Vacuum assisted die casting can reach T6, but it adds cost. Permanent mold castings take full T6 routinely, which is why structural and pressure tight parts often go that route.
Why is die cast tooling so much more expensive?
The die sees molten metal slamming in at up to 25,000 psi and thousands of thermal cycles per day, so it needs hardened H13 tool steel, cooling lines, slides, and ejection systems. A gravity permanent mold sees near zero pressure and can be machined from cheaper iron with simpler construction.