In the casting process according to the different metal casting process can be divided into gravity casting and pressure casting.

Gravity casting refers to the metal liquid under the action of gravity into the model of the process, also known as casting. Broadly speaking, the gravity casting, including sand casting, metal casting, investment casting, Lost Foam casting, mud casting and other processes, in the narrow sense, the gravity casting refers to the metal casting. Pressure casting refers to the metal liquid under the action of other external forces into the model of the process.

Precision casting is the metal casting on the die casting machine, is the most efficient casting process, die casting machine can be divided into hot chamber die casting machine and cold chamber die casting machine two categories. Hot chamber die-casting machine is highly automated, material loss is very small, the production efficiency than the cold chamber die-casting machine to improve a lot. But the hot chamber die-casting machine by the heat capacity constraints, is still only used for zinc alloy, magnesium alloy, low melting point of the metal casting production. Currently widely used aluminum alloy die castings, due to the high melting point of aluminum, can only be produced in the cold chamber die casting machine. The main feature of precision casting is the metal hydraulic pressure in the case of high pressure, high-speed filling cavity, and under high pressure forming, solidification.

The disadvantage of die casting is that the metal liquid in the high-pressure, high-speed filling the cavity during the process, inevitably the cavity of the air wrapped in the casting inside the formation of subcutaneous pores, so aluminum Precision die-casting parts should not heat treatment, zinc alloy die casting should not surface spray (but can paint). Otherwise, the internal stomata of the castings will undergo thermal expansion and cause the casting to deform or bulge when heated as described above. In addition, the die cutting of the mechanical cutting allowance should also be smaller, generally about 0.5mm, can reduce casting weight, reduce the amount of cutting to reduce costs, but also to avoid penetrating the surface dense layer, exposed subcutaneous stomata, resulting in Workpiece scrap.