First, process analysis

       1. The piston rod is subjected to alternating load during normal use. The sealing device reciprocally rubs the surface at φ50mm×770mm, so the hardness and wear resistance are required.

       2. The structure of the piston rod is relatively simple, but the length to diameter ratio is very large. It belongs to the slender shaft type parts and has poor rigidity. In order to ensure the machining accuracy, the roughing and the fine car are separated during turning, and the coarse and fine cars are used uniformly. The tool holder is used to reduce the deformation of the workpiece during machining. The center frame is used when machining the threads at both ends.

       3. When selecting the positioning reference, in order to ensure the coaxiality tolerance of the parts and the mutual positional accuracy of each part,

All machining operations are positioned in two center holes, in line with the principle of benchmarking.

       4. When the outer surface is ground, the workpiece is easy to produce a knife and elastic deformation, which affects the accuracy of the piston rod. Therefore, the center hole should be repaired during processing, and the center hole should be cleaned, the tightness between the center hole and the tip should be appropriate, and good lubrication should be ensured. Grinding wheel is generally selected: abrasive white corundum (WA), particle size 60#, soft or medium and ceramic bond in hardness, and the width of the grinding wheel should be narrower to reduce the radial grinding force, pay attention to the choice of grinding amount during processing. In particular, the grinding depth is small.

       5. When grinding φ50mm×770mm outer circle and 1:20 taper, the two processes must be carried out separately. When grinding 1:20 taper, the test piece must be ground first, and the workpiece can be formally ground after the test piece is qualified.

       6, the 1:20 conical surface inspection, is to use the standard 1:20 ring gauge color inspection, the contact surface should be no less than 80%.

       7. In order to ensure the stability of the processing precision of the piston rod, manual alignment is not allowed in the whole process of processing.

       8. When nitriding, the threaded part should be protected by a protective device.