What are the characteristics of valve manufacturing process? Compared with other mechanism manufacturing processes, the valve manufacturing process has the following characteristics:
First of all, the manufacturing process and inspection process of valve blank are relatively complex. The casting blank of valve is a complex thin-walled shell. The surface of the casting is required to be smooth and clear, especially with dense defects. In order to meet the above requirements, a series of technological measures should be taken during casting. For example, the electric control valve should select the molding material with high fire resistance and control the moisture content of molding sand. During molding, it should be compacted layer by layer to ensure the hardness of sand mold. It should adopt a reasonable pouring cap mouth system and strictly control the pouring speed and temperature. Due to the high technical requirements, the casting process of valve blank is far more complex than that of general castings. In addition, in addition to checking the size, position accuracy and appearance of the valve blank, there are also many kinds of tests such as metallographic structure, mechanical properties, corrosion resistance and non-destructive testing, so the inspection process of the valve is also complex.
Secondly, it is difficult to install the valve parts on the machine tool. The structure and shape of the main parts of the valve are more complex. Some parts are thin and slender with poor rigidity. When machining on machine tools, it is difficult to locate and clamp, so complex special clamps are often needed. For some valve parts, the accuracy of locating base surface is low, and the surface roughness is high, sometimes even non machined surface is used for locating. The precision and surface roughness of the processed sealing surface are very high, so it is difficult to guarantee the processing quality of the pneumatic control valve. Therefore, in order to meet the needs of the process, it is often necessary to improve the accuracy of the positioning surface and reduce the surface roughness, or to process the positioning surface on the non machined surface, which increases the complexity of the valve manufacturing process.
At last, it is difficult to machine. Because of various kinds of valve materials, except for various kinds of cast iron and carbon steel, most of the high-strength, corrosion-resistant and hard materials have poor cutting performance, so it is difficult to make the parts reach the specified machining accuracy and surface roughness. However, the requirements of geometric shape accuracy and surface roughness of valve sealing surface are very high, which increases the difficulty of valve machining. At the same time, the poor cutting performance of valve material brings a lot of new problems to the valve processing method, tool material, cutting parameters, process equipment and so on.