How is die casting machine tonnage chosen?

From the projected area of the casting and runners times the metal pressure, with a safety margin, so the die stays shut during the shot.

Why can't aluminium use a hot-chamber machine?

Molten aluminium attacks the steel parts sitting in the melt, so aluminium needs a cold-chamber machine.

Are die castings porous?

Some porosity is normal. Vacuum die casting and good die design reduce it where parts must be pressure-tight or welded.

Die casting machine: hot and cold chamber, tonnage

A die casting machine forces molten metal into a hardened steel die under high pressure, then opens the die and ejects the solid casting. Hot-chamber machines, used for zinc, keep the injection unit in the melt and cycle very fast. Cold-chamber machines, used for aluminium, ladle metal into a shot sleeve for each shot. Machines are rated by the clamping force that keeps the die shut.

Quick facts

Main types: Hot chamber (zinc), cold chamber (aluminium, brass)
Clamping force: About 80–1,600 tonnes typical
Cycle time: Seconds to about a minute
Injection pressure: Several hundred bar on the metal
Automation: Ladle, die spray and extraction robots
Tooling: Hardened H13 steel dies

Main parts

Clamping unit with toggle and platens
Injection system (shot cylinder and plunger)
Holding furnace (hot chamber) or ladle (cold chamber)
Die spray and cooling
Ejectors and part extraction

Hot or cold chamber?

	Hot chamber	Cold chamber
Metals	Zinc, some magnesium	Aluminium, brass, magnesium
Speed	Very fast	Slower
Die life	Longer	Shorter (hotter metal)

Good to know

Tonnage needed rises with the casting's projected area
Vacuum assistance reduces porosity in critical parts
Die cost is high, so die casting suits large quantities

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Questions

How is die casting machine tonnage chosen?: From the projected area of the casting and runners times the metal pressure, with a safety margin, so the die stays shut during the shot.
Why can't aluminium use a hot-chamber machine?: Molten aluminium attacks the steel parts sitting in the melt, so aluminium needs a cold-chamber machine.
Are die castings porous?: Some porosity is normal. Vacuum die casting and good die design reduce it where parts must be pressure-tight or welded.

The figures on this page are typical values for guidance, written by Diemeco from standard engineering practice. They are not a specification: confirm grades and properties with the relevant standard or the supplier's mill test certificate, and tolerances with your workshop. Last checked 23 October 2026.