Die casting is a metal casting process that is characterized by forcing molten metal under high pressure into a mold cavity. The mold cavity is created using two hardened tool steel dies which have been machined into shape and work similarly to an injection mold during the process.
Most die castings are made from non-ferrous metals, specifically zinc, copper, aluminium, magnesium, lead, pewter and tinbased alloys. Depending on the type of metal being cast, a hot- or cold-chamber machine is used.
The casting equipment and the metal dies represent large capital costs and this tends to limit the process to high volume production. Manufacture of parts using die casting is relatively simple, involving only four main steps, which keeps the incremental cost per item low. It is especially suited for a large quantity of small to medium sized castings, which is why die casting produces more castings than any other casting process. Die castings are characterized by a very good surface finish (by casting standards) and dimensional consistency.
Advantages of die casting:
- excellent dimensional accuracy (dependent on casting material, but typically 0.1 mm for the first 2.5 cm (0.005 inch for the first inch) and 0.02 mm for each additional centimeter (0.002 inch for each additional inch);
- smooth cast surfaces;
- thinner walls can be cast as compared to sand and permanent mold casting (approximately 0.75 mm or 0.030 in);
- inserts can be cast-in (such as threaded inserts, heating elements, and high strength bearing surfaces);
- reduces or eliminates secondary machining operations;
- rapid production rates;
- casting tensile strength as high as 415 megapascal;
- casting of low fluidity metals.