Cold chamber die casting is ideal for metals with high melting points and corrosive properties, like aluminum.

Unlike the hot chamber die casting process, cold chamber solves the corrosion problem by separating the melt pot from the injector components. In the cold-chamber process, metal is transferred by ladle, manually or automatically, to the shot sleeve. Actuation of the injection piston forces the metal into the die—this is a single shot operation. This procedure minimizes the contact time between the hot metal and the injector components, which helps to extend their operating life.

It is possible to cast lower melting point alloys using the cold chamber process but when you consider the advantages of the hot chamber process it usually makes more economical sense to use the hot chamber method for metals like zinc and magnesium.

During cold chamber die casting, the molten charge, which consists of more material than is required to fill the casting, is ladled from the crucible into a shot sleeve where a hydraulically operated plunger pushes the metal into the die. The extra material is used to force additional metal into the die cavity to compensate for shrinkage, which takes place during solidification.

The main components of a cold chamber die casting machine are shown below. Injection pressure of over 10,000psi or 70,000KPa can be obtained from this type of machine.

Operating sequence of the cold chamber die casting process.

The die is closed and the molten metal is ladled into the cold chamber shot sleeve.

The plunger pushes the molten metal into the die cavity where it is held under pressure until it solidifies.

The die opens and the plunger advances, to ensure the casting remains in the ejector die. Cores, if any, retract.

Ejector pins push the casting out of the ejector half of the die and the plunger returns to its original position.