Die casting is a very versatile and cost effective process for components requiring high yearly volumes and complex geometries. Typically, the zinc die casting process is considered when yearly volumes reach at least 15,000 parts. Lesser volumes may require other zinc casting processes such as sand casting or graphite permanant molding. Die casting is a net-shape process, and cost savings can be achieved by eliminating secondary machining and assembly operations required by other processes. Often, when converting components to zinc die castings, the assembly can be redesigned to allow the consolidation of multiple parts to one net shape shape die cast component.
There are two zinc die casting processes: Hot Chamber and Cold Chamber. The Hot Chamber process is used for alloys with low melting temperatures and a low attack rate on steel components. This process is used for most of the zinc die casting alloys, and is more economical. In this process, the metal pump (gooseneck) is immersed in the molten zinc alloy (thus the name "hot chamber"), pumping metal directly from the furnace to the die. Advantages include faster cycle times, smaller runner systems (and resulting air in the process) and lower processing costs compared tot he cold chamber process.
Hot chamber zinc alloys include the Zamak alloys, ZA-8, ACuZinc 5, and EZAC. Typically Zamak 3 is the first alloy choice in North America due to its combination of alloy cost, properties, and castability.
The Cold chamber process is similar to the Hot chamber process except that the molten metal is poured into a horizontal cylinder, and then injected into the mold. Alloys that require the Cold chambe process (such as Aluminum alloys or ZA-12 and ZA-27 zinc alloys) have a higher attack rate on iron and steel components.