Determination and Process Analysis of Piston Rod Blank
Jun 29, 2022
The working mode of the piston rod is in the form of reciprocating motion. In order to increase the life of the piston rod and reduce the wear amount of the piston rod, 38CrMoAlA alloy structural steel is selected for the blank. Since the production type belongs to batch production, in order to improve the production efficiency, it is recommended to use the free forging method to manufacture the blank.
According to the machining accuracy requirements of the part drawing, the dimensional tolerance level of the forgings is 8-12, the piston rod is selected for small batch production, and the cylindrical blank is considered. The production method of the blank is free casting, which is operated according to the size requirements of the piston rod part drawing and the actual processing requirements.
When selecting the positioning datum, in order to ensure the coaxiality tolerance of the parts and the mutual positional accuracy of each part, all machining processes are positioned with two center holes, which conforms to the principle of datum unification. According to the technical requirements and assembly requirements of the piston rod, the center hole of the left and right end faces and the two end faces of the piston rod should be selected as the precision benchmark.
Many surfaces on the part can be processed with the two end faces as the benchmark; the central axis of both ends is the design benchmark; the central axis is selected as the benchmark to ensure the machining position accuracy after the surface, and to achieve the coincidence of the design benchmark and the process benchmark. Since the finishing process of the two-axis surface requires a small and uniform allowance, it can use itself as a reference.
During processing, the center hole should be repaired, and the center hole should be clean, the tightness between the center hole and the top should be appropriate, and good lubrication should be ensured. When grinding φ50mm×770mm outer circle and 1:20 taper, the two processes must be carried out separately. When grinding a 1:20 taper, the test piece must be ground first, and the workpiece can be formally ground after the test piece is qualified.
