This technical information has been contributed by
The American Die Casting Institute

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Everything You Need to Know About Die Casting:
Hot-Chamber and Cold-Chamber Processing

There are two basic die casting processes: hot-chamber and cold- chamber. The hot-chamber process is used for zinc alloy ZA-8 and magnesium Alloys AZ91B and AZ9ID. The cold-chamber process is used for aluminum alloys ZA-12 and ZA-27, and magnesium alloys AZ91B and AZ91D, particularly for large castings.

In the hot-chamber die casting process, the plunger and cylinder are submerged in the molten metal in the holding furnace. The energy to pump the metal into the die cavity is provided by a hydraulic pump and stored in an accumulator. Oil is supplied at a rate that will bring the pressure to the desired operating level each time a slot is made.

The operating sequence for the hot-chamber cycle: when a shot is made, the plunger is driven downward, forcing molten metal through the gooseneck and nozzle into the die cavity. After the cavity is filled, the metal is allowed to solidify, the casting is ejected, and the cycle repeated. A die lubricant, or mold release compound, is periodically sprayed onto the die to facilitate release of the casting. The system refills automatically when the plunger is withdrawn because the gooseneck and plunger are submerged in the molten metal.

The operating sequence for the cold-chamber process: the operating sequence is essentially the same as for hot chamber, except for the manner in which the molten metal is fed into the shot system prior to injection into the die. In the cold-cha ber process molten metal is ladled, either by hand or machine, or pumped into a horizontal shot cylinder. A hydraulically actuated plunger then advances to force the metal into the die.

The differences in metal feed give the hot-chamber process several advantages:

There are five significant characteristics common to both cycles which should be noted:

This technical information has been contributed by
The American Die Casting Institute

Click here to find suppliers

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