Compared with other mechanism manufacturing processes, the valve manufacturing process has the following characteristics:

①The manufacturing process and inspection process of valve blank are more complicated.

The casting blank of the valve is a thin-walled shell with a complex structure. The casting requires smooth surface and clear casting, especially dense defects. In order to meet the above requirements, a series of process measures should be taken during casting, such as the selection of high refractory molding materials and control of sand moisture, the modeling should be layered to ensure the hardness of the sand, the use of a reasonable gating system and strict control of pouring speed and temperature. Due to the high technical requirements, the casting process of the valve blank is far more complex than that of the general casting.

In addition, in addition to checking the size, position accuracy and appearance of the valve blank, some also have a variety of tests such as metallographic structure, mechanical properties, corrosion resistance and non-destructive testing, so the valve inspection process is also more complex.

②It is difficult to install valve parts on machine tools

The structure and shape of the main parts of the valve are more complex, and some parts are thin and slender parts with poor rigidity. When machining on machine tools, positioning and clamping are more difficult, so complex special fixtures are often required.

Some valve parts, the positioning base precision is low, the surface roughness is high, and sometimes even the use of non-machined surface positioning. The precision and surface roughness requirements of the machining sealing surface and other parts are very high, so it is difficult to ensure the processing quality. Therefore, in order to meet the needs of the process, it is often necessary to improve the accuracy of the positioning base and reduce the surface roughness, or to process the positioning base on the non-machined surface, which increases the complexity of the valve manufacturing process.

③Machining is difficult

Due to the wide variety of valve materials, in addition to a variety of cast iron, carbon steel, most of its high strength, corrosion resistance and high hard material cutting performance are very poor, it is difficult to make parts to achieve the specified processing accuracy and surface roughness. The geometric accuracy and surface roughness of the sealing surface of the valve are very high, so it increases the difficulty of valve machining. At the same time, the poor cutting performance of the valve material has brought many new problems to the processing methods of the valve, tool materials, cutting parameters, process equipment and so on.