In the casting process of machine bed castings, the principle of high-temperature oven and low-temperature casting should be followed. Because raising the temperature of molten metal is beneficial to the complete melting of inclusions, slag floating, easy to remove slag and degassing, reduce the slag inclusion and porosity defects of machine tool castings; The lower casting temperature is beneficial to reduce the gas solubility of liquid metal, liquid shrinkage and the baking of high temperature liquid metal on the surface of the cavity, so as to avoid defects such as porosity, sand sticking and shrinkage cavity. There are many classification methods for castings: according to the different metal materials used, they are divided into steel castings, cast iron castings, copper castings, aluminum castings, magnesium castings, zinc castings, titanium castings and so on. Each type of casting can be further divided into different types according to its chemical composition or metallographic structure. For example, cast iron can be divided into gray cast iron, nodular cast iron, vermicular cast iron, malleable cast iron, alloy cast iron, etc.According to the different casting methods, castings can be divided into ordinary sand castings, metal castings, die castings, centrifugal castings, continuous casting parts, investment castings, ceramic castings, electroslag remelting castings, bimetal castings, etc. Among them, ordinary sand casting is the most used, accounting for about 80% of the total casting output. And aluminum, magnesium, zinc and other non-ferrous metal castings, most of them are die castings.Therefore, on the premise of filling the mold cavity, a lower pouring temperature should be used as far as possible. The operation of pouring liquid metal from the ladle into the mold is called pouring. Improper pouring operation will cause defects of machine tool castings such as insufficient pouring, cold insulation, porosity, shrinkage and slag inclusion, and cause personal injury.