Precision casting can also be divided into gravity casting and pressure casting according to the pouring process of molten metal. Gravity casting refers to the process of pouring molten metal into a mold under the action of the earth’s gravity, also known as casting. Gravity casting includes sand casting, metal casting, investment casting, clay casting, etc.; gravity casting in a narrow sense refers to metal casting. Die casting is the process in which molten metal is injected into a mold under the action of other external forces (excluding gravity). Die casting includes pressure casting, vacuum casting, low pressure casting, centrifugal casting, etc. In a narrow sense, pressure casting refers to the pressure casting of metal molds by a die casting machine, referred to as die casting. The hardware factory has long been engaged in the gravity casting of sand and metal molds. These casting processes are currently the most commonly used and relatively low-cost in non-ferrous metal casting.

Sand casting is a traditional casting process that uses sand as the main molding material to make molds. Sand molds generally use gravity casting, and low-pressure casting and centrifugal casting can also be used when there are special requirements. Sand casting has a wide range of adaptability and can be used in small blocks, large blocks, simple blocks, complex blocks, single pieces and large batches. The mold for sand casting, which used to be made of wood, is called a wooden mold. In order to overcome the shortcomings of wood molds such as easy deformation and damage, all sand molds are changed to aluminum alloy molds or resin molds with high dimensional accuracy and long service life. Although the price has increased, it is still significantly cheaper than the molds used in permanent mold casting, especially in small and high-volume production. In addition, sand molds have higher refractoriness than metal molds, so materials with higher melting points, such as copper alloys and ferrous metals, also use this process. However, sand casting also has some disadvantages: since each sand mold can only be poured once, the mold is damaged after obtaining the casting and must be reshaped, and the production efficiency of sand casting is low; due to the overall soft and porous sand, sand casting has low dimensional accuracy and rough surface. However, the technology accumulated by the precision foundry for many years has greatly improved the surface condition of sand castings, and the effect after shot peening is comparable to that of metal castings.