1) process analysis of part drawing The surface of this part is composed of cylinder, cone, straight arc, reverse arc and thread. Several diameters have strict requirements on dimensional accuracy and surface roughness. The tolerance of spherical dimension Sφ50㎜ also has the function of controlling spherical shape (line contour) error. Complete size and clear outline description. The material of the parts is 45 steel, without heat treatment and hardness requirements. Through the above analysis, the following technical measures can be taken. (1) For several dimensions given on the drawing with high accuracy requirements, because of their small tolerance values, it is not necessary to take the average value when programming, but the basic dimensions can be taken. (2) On the contour curve, there are three arcs, two of which are contour curves that pass through quadrants and change the feed direction. Therefore, mechanical clearance compensation should be carried out in the machining process to ensure the accuracy of contour curve. (3) In order to facilitate clamping, the left end of the blank should be turned out of the clamping part (double dotted line part) in advance, and the right end should be roughly turned out and drilled with a central hole. Choose φ60㎜ steel bar as blank. (2) Selection of equipment According to the shape and material of the parts to be processed, TND360 CNC lathe is selected. (3) Determine the positioning datum and clamping mode of the parts ① Positioning datum Determine the blank axis and the large end face at the left end (design datum) as the positioning datum. (2) Clamping mode: the left end is centered and clamped by a three-jaw self-centering chuck, and the right end is supported by a movable center. (4) Determine the processing sequence and feed route processing sequence according to the principle of from coarse to fine, from near to far (from right to left). That is to say, rough turning should be carried out from right to left (leaving 0.25㎜ finish turning allowance), then finish turning from right to left, and finally thread turning. TND360 CNC lathe has the functions of rough turning cycle and thread turning cycle. As long as the programming instructions are used correctly, the CNC system of the machine tool will automatically determine its feed route. Therefore, the rough turning cycle and thread turning cycle of this part do not need to be determined manually (but the feed route of fine turning needs to be determined manually). As shown in fig. 2, the parts are finely rotated and fed from right to left along the surface contour of the parts. Fig. 2 Feed route of finish turning contour (5) Tool selection ① Select φ5㎜ center drilling center hole. (2) rough turning and flat end face, choose 900 carbide right deviation cutter. In order to prevent the interference between the secondary flank and the contour of the workpiece (which can be checked by drawing method), the secondary deflection angle should not be too small, κ = 35 0. (3) Select 900 cemented carbide right-hand turning tool for finish turning, and select 600 cemented carbide external thread turning tool for turning thread. The arc radius of the tip should be smaller than the minimum fillet radius of the contour, and r ε = 0. 15 ~ 0.2 ㎜. Fill the selected tool parameters into the NC machining tool card (see table 1) for programming and operation management. Table 1 NC machining tool card product name or code ×××× part name Typical shaft part drawing number×××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××× When turning threads, refer to the formula (5- 1) n =320 r/min to calculate the spindle speed. (3) Select the feed speed of rough turning and finish turning, then determine the feed speed of rough turning and finish turning as 0.4㎜/r according to the actual processing situation, and then determine it as 0. 15㎜/r according to the formula. Based on the previous analysis, fill in the NC machining process card shown in Table 2. This table is the main basis for compiling the machining program, and it is also the guiding document for the operator to cooperate with the NC program for NC machining. The main contents include: step sequence, step content, tools used in each step and cutting amount, etc. Table 2 Typical shaft parts NC machining process card unit name ×××× product name or code part name Part drawing number ×××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××