Cold Chamber Die Castings

Cold Chamber Die Castings

There are two main methods of the die casting process-hot chamber and cold chamber die casting. Cold chamber refers to die casting that is done when the metal injection mechanism is separate from the furnace and unheated. It is used to cast alloys with higher melting points and metals like aluminum, brass and copper. These metals cannot be cast in a hot chamber because they would cause damage to the pumping system, since they require such a high melting point temperature. By separating the furnace and chamber, cold chamber die castings minimize the amount of heat, and thus reduce the chance of corrosion in the plunger. While the cycle time for cold chambers is still fast-between 10 seconds and 2 minutes-it takes longer than the hot chamber die casting process, which is used when metals have a lower melting point, and can therefore be cast inside a furnace. Cold chamber die casting is the more popular alternative because of a cheaper cost of production and more durability. The products exhibit naturally smooth surfaces, and therefore require less secondary processing. Products made from cold chamber die casting are found and used within the automotive, industrial and commercial spheres.

The cold chamber die casting process begins when the metal material is heated until molten in a furnace. Since the holding pot is kept separate from the die casting machine, the molten metal is either automatically or manually transferred from the furnace to the cold chamber by a ladle instead of pumping. A plunger forces the metal into the injection sleeve of the die under great amounts of pressure; between 2 and 20 thousand psi. The exposure time for the molten metal to plunge the walls of the mold is much less than hot chamber molding because the metal tends to cool very quickly. After the cast has solidified, it is removed from the mold and taken to any necessary post processing. Since the holding pot is not located inside the furnace, cold chamber die casting machines are larger and bulkier than their alternatives.