Die casting is a kind of metal mould pressure casting on die casting machine, which is the most efficient casting technology at present. Die casting machine is divided into hot chamber die casting machine and cold chamber die casting machine. The hot chamber die casting machine has high degree of automation, less material loss and higher production efficiency than the cold chamber die casting machine. However, restricted by the heat-resistant ability of the parts, it can only be used for the production of low melting point materials such as zinc alloy and magnesium alloy at present. The widely used aluminumcan only be produced on the cold chamber die casting machine because of its high melting point. The main feature of die casting is that the metal liquid fills the cavity under high pressure and high speed, and forms and solidifies under high pressure. The disadvantages of die casting are: because the air in the cavity is inevitably trapped in the casting to form subcutaneous pores in the process of filling the cavity under high pressure and high speed, so the aluminum alloy die casting is not suitable for heat treatment, and the zinc alloy die casting is not suitable for surface treatment Spray (but spray). Otherwise, when the air hole in the casting is heated by the above treatment, it will encounter thermal expansion and cause the casting to deform or bubble. In addition, the machining allowance of die casting should also be smaller, generally around 0.5mm, which can not only reduce the weight of the casting, reduce the amount of machining to reduce the cost, but also avoid penetrating the surface dense layer, exposing the subcutaneous pores, resulting in workpiece scrap.