To improve the roughness of its surface and the out of roundness of the ball. Grinding is precision machining. The grinding of a sphere is different from that of a flat plate and a cylinder. It is particularly required to have a uniform degree of processing. The high labor intensity of manual processing requires high technology, low work efficiency, difficult quality control, and easy to scrap. According to the above processing characteristics, the ball grinding is realized by mechanical equipment. It is more in line with its work characteristics. The movement track of the ball grinding equipment for advanced hard seal pneumatic ball valve is more consistent with the geometric shape of the ball. The structure is compact, reasonable, scientific, and simple to operate. Use the concentric inner hole of the sphere to cover the sphere on the inner expansion sleeve of the elastic center of the main shaft. Rotate with the spindle at low speed to improve its machining accuracy. The lapping tool rotates on the spherical surface at an angle of 25 degrees by adjusting the pressure of the spring. Grind the shaft sleeve and rotate the rocker arm on the main shaft. The lapping tool can be made of ordinary cast iron or brass. Material sources are extensive. The ratio of the outer diameter of the lapping tool to the diameter of the sphere should be 6/10, and the ratio of the outer diameter of the lapping tool to the inner diameter should be 5/9. The speed of the lapping tool is too fast to avoid frequency vibration and overheating, which will affect the accuracy. The ball shall be carefully checked before grinding, and there shall be no bruises, defects and other defects near the sealing belt. The difference in geometric shape of large-sized spheres will be larger during surface hardening treatment, so it is recommended to use coarser grinding emery for grinding. The upper limit of grinding pressure can be selected. Due to the change of sand particles in the grinding process, lubricating fluid should be added in time to improve work efficiency. The key point of the first grinding is to correct the geometric tolerance. Be careful and patient.

Positive action of valve positioner: when the input current signal increases, the air pressure output to the diaphragm head increases;