Complex parts can be diecast at a high volume so many manufacturers use these parts both in their products and equipment. Before the vacuum and injection molded plastics are formed, diecast parts provide the exterior shape of many common products and consumer items, such as cash registers and parking meters. Many modern parts which require the strength of metal use whole diecast parts, such as gumball machine bases, sink faucets and a wide range of metal parts used in automotive and industrial machinery. Computers and electronic industries also use high tolerance magnesium diecastings as housings and interior enclosures as well as miniature zinc diecast parts for various electronic equipment applications.
Before parts can be cast, a cavity must be tooled into the desired shape of the part. For closed diecasting, which are the majority of castings, this cavity is cut into in two separate metal blocks; in order to form a complete mold, the tooled blocks are placed together with cavities aligned. This cavity is called a die. Once the die has been created, it is smeared with lubricant that controls the temperature of the die and assists in part removal once the cast is complete. The die is then closed while the metal will be poured and injected into the die under high pressure by a plunger. The pressure will remain in the die until the cast is solidified in which only then the die will be opened and the ejector pins will push out the shots. The piece of metal will be considered a shot until the surrounding excess material is removed from the casting. The cast part is tooled and then put through additional secondary processes such as surface finishing, painting, plating and machining.
Diecasting is a high volume, low cost means of forming relatively complex metal parts. These parts do not have high strength and often have micro fractures and inconsistencies which can lead to part failure or breakage under strain, corrosion or heat stress which is why parts are often heat-treated and carefully tested after manufacturing. Critical applications requiring high strength, high resistance parts use forging rather than diecasting. Although the diecastings process is not capable of manufacturing high strength, high resistance parts, diecast parts can reach far greater complexities with much higher tolerances than any other metal forming process.