Imaginary tool tip and tool tip fillet (A. Imaginary tool tip B. Actual tool cutting point) In order to eliminate the machining error caused by turning tool tip fillet, it is necessary to know the size of tool tip fillet radius first. The result of measuring the tool tip with a tool measuring instrument is R0.21mm. The CNC system of the lathe used for machining is Fanuc OI Mate, which has the function of tool tip arc radius compensation. Therefore, the tool radius compensation command (G41, C42) can be used for tool tip fillet radius compensation. According to the forward direction of the tool path, the tool is located on the right side of the workpiece, so G42 tool compensation command should be used. The tool compensation is related to the orientation of the imaginary tool tip relative to the center of the tool tip fillet (8 orientations in total). The orientation code in Figure 4 is 3. After determining the relevant parameters, first determine the position of the turning tool on the X axis and Z axis with the trial cutting method, and enter the compensation value, then enter the tool tip radius R and the imaginary tool tip orientation code T (see Table 1). Table 1 Tool compensation table Tool complement number XZRT01120900.213 NC machining procedure is as follows: rough machining engineering sequence N50 G00 X0 Z37N60 G42 G01 Z35N70 G03 X0 Z0 R37 F0.05N80 G40 G00 Z37... As long as the tool is set according to the fixed position, machining can be carried out. After cutting, remove the cutter head through the hole with diameter of 28, move the cutter bar along the Z axis (not moving in the X direction), remove the workpiece, install new parts, then set the cutter bar in position, install the cutter head, and continue processing. The test results show that the dimensional accuracy and surface quality of the shell parts of the pneumatic ball valve machined by this method are completely qualified.

2、 There are many kinds of butterfly valves, and there are many classification methods.
1. Classification by structure
(1) Center sealing butterfly valve
(2) Single eccentric sealing butterfly valve
(3) Double eccentric sealing butterfly valve
(4) Triple eccentric sealing butterfly valve