Hot-chamber die casting vs cold-chamber die casting from Chinamfg's blog

Die casting falls into two main subtypes: hot-chamber die casting and cold-chamber die casting. These subtypes differ in terms of where the metal is melted and how it is injected. Crucially, only certain materials are suitable for hot-chamber die casting. (Note that cold-chamber die casting still requires fully molten metal; it does not process metal in its solid form.)

The main feature of a hot-chamber die casting is an ability to heat up metal within the die casting machine. Sometimes called gooseneck machines, these systems contain an internal combustion area and a pot for the molten metal. A piston (hydraulic or pneumatic) forces molten metal from the chamber into the die, whereupon the chamber can be immediately re-filled in preparation for the next shot.

Cold-chamber die forging requires the external heating of die casting materials, and the molten metal must then be transferred to the die casting machine with a transfer tube or ladle. A ram forces the molten metal from the chamber into the die (at a higher pressure than is used for hot-chamber die casting). This process is slower, since the metal needs to be transferred from the external source for each shot.

Although hot-chamber die casting is faster, it is more limited in its material compatibility. It typically only works for metals with a low melting point such as zinc, magnesium, and lead alloys. It cannot process aluminum alloys, since these can pick up iron from the chamber.