Tutorial on Die Casting

[Magneto]

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Molten aluminum, magnesium or zinc alloys are injected into the water-cooled dies under high pressure. The dies open and the part is ejected. The flash is removed, usually by a trimming die, and finished.

There are two types of machines: cold chamber and hot chamber.
In a cold chamber process, the molten metal is ladled into the cold chamber for each shot. There is less time exposure of the melt to the plunger walls or the plunger. This is particularly useful for metals such as Aluminum, and Copper (and its alloys) that alloy easily with Iron at the higher temperatures.
Instead in a hot chamber process the pressure chamber is connected to the die cavity is immersed permanently in the molten metal. The inlet port of the pressurizing cylinder is uncovered as the plunger moves to the open (unpressurized) position. This allows a new charge of molten metal to fill the cavity and thus can fill the cavity faster than the cold chamber process. The hot chamber process is used for metals of low melting point and high fluidity such as tin, zinc, and lead that tend not to alloy easily with steel at their melt temperatures.

Process properties:
Advantages:
high production, good tolerances, low part price, good surface finish.
thin walls.
Disadvantages:
limited to nonferrous metals and fairly small parts.
expensive tools, long lead time, required draft angles.
Typical Parts:
automotive parts, industrial tool and motor housings, plumbing fixtures.