Die casting is a casting process widely used in the manufacturing industry, which involves pressing molten metal into the cavity of a pre-shaped mould. When they achieve a molten state, base metals such as zinc, aluminium, copper, magnesium and lead are first heated. The freshly molten metal is then, using pressure, pushed into a pre-shaped mould. It's removed from the mould until the molten metal has cooled and hardened. With that said, there are two types of die casting processes that are different: hot and cold.
Overview of Hot-Chamber Die Casting
The same method previously mentioned is used for hot-chamber die casting: molten metal is pushed by pressure through the cavity of a pre-shaped mould. The distinguishing aspect of hot-chamber die casting is that, instead of a separate machine or furnace, metal is heated inside the casting machine.
Hot-chamber casting machines, also known as gooseneck machines, have a built-in furnace in which metal is heated to reach a molten state. They use a piston driven by hydraulic power that pushes molten metal out of the furnace and into the die. A relatively quick method is hot-chamber die casting, with a typical period lasting only 15 to 20 minutes. While it is not acceptable for high melting point metals, it is suitable for zinc alloys, tin alloys and lead alloys.
Overview of Cold-Chamber Die Casting
You can presume, based on its name, that cold-chamber die casting involves pushing cold metal through a mould's cavity, but this is not generally true. The use of molten metal that is forced into a mould is still needed for Cold-chamber die casting. The distinction between these two methods is that inside the casting machine, hot-chamber die casting heats the metal, while in a separate furnace, cold-chamber die casting involves heating metal and then moving the newly melted metal to the casting machine.
With cold-chamber die casting, metal in a separate furnace is first heated to reach a molten state. Then the molten metal is taken to the casting machine where it is fed into the chamber of the machine. To push the molten metal into the cavity of the mould, the system uses a pressurised plunger.
Certain forms of metals can only be processed using cold-chamber die casting, those with a high melting point. For metals such as aluminium, magnesium and copper, the high temperatures needed to achieve a molten state means a separate furnace must be used, which is why some manufacturers prefer cold-chamber die casting over hot-chamber die casting.