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

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

The casting blanks of the valves are complex thin-walled shell parts. The casting requires a smooth surface and clear characters, especially with few defects. To meet these requirements, a series of process measures should be taken during the casting process, such as selecting high-temperature-resistant molding materials and controlling the moisture content of the molding sand. During the molding process, it is necessary to layer and compact the sand to ensure the hardness of the sand mold. A reasonable pouring cap system and strict control of the pouring speed and temperature should also be adopted. Due to the high technical requirements, the casting process of the valve blanks is far more complex than that of ordinary castings. 

In addition, the valve blanks are not only inspected for dimensions, positional accuracy and appearance, but also undergo examinations such as metallographic structure, mechanical properties, corrosion resistance and non-destructive testing. Therefore, the inspection process for valves is rather complex. 

2. Installing the valve component on the machine is quite difficult. 

The structures and shapes of the main components of the valves are quite complex. Some of the parts are thin-walled and long, with poor rigidity. During machine processing, both positioning and clamping are quite challenging, so complex special fixtures are often required. 

Some valve components have relatively low precision of the positioning base surface and high surface roughness. Sometimes, non-processed surfaces are even used for positioning. The precision and surface roughness requirements for processing the sealing surfaces and other parts are very high, so it is difficult to ensure the processing quality. Therefore, to meet the requirements of the process, it is often necessary to improve the precision of the positioning base surface and reduce the surface roughness, or to process a positioning base on the non-processed surface. This increases the complexity of the valve manufacturing process. 

3. The mechanical processing is very difficult. 

Due to the wide variety of valve materials, apart from various cast irons and carbon steels, the cutting performance of most high-strength, corrosion-resistant and high-hardness materials is very poor, making it difficult to achieve the specified processing accuracy and surface roughness for the parts. Moreover, the geometric shape accuracy and surface roughness requirements of the valve sealing surfaces are very high, thus increasing the difficulty of valve mechanical processing. At the same time, the poor cutting performance of valve materials also brings many new problems to the processing methods, tool materials, cutting parameters, and process equipment of the valves.