Process Analysis and Working Mode of Piston Rod Parts
Jun 08, 2022
In normal use, the piston rod is subjected to alternating loads. There is a sealing device at φ50mm×770mm to rub its surface back and forth, so it requires high hardness and wear resistance. The piston rod is made of 38CrMoALA material. After the φ50mm×770mm part is quenched and tempered and surface nitrided, the core hardness is 28~32HRC, the surface nitriding layer depth is 0.2~0.3mm, and the surface hardness is 62~65HRC. In this way, the piston rod has both toughness and good wear resistance.
The structure of the piston rod is relatively simple, but the ratio of the length to the diameter is large. It belongs to the slender shaft and has poor rigidity. In order to ensure the machining accuracy, the rough turning and fine turning should be separated during turning, and the tool rest should be used for both rough and fine turning. , in order to reduce the deformation of the workpiece during processing, and use a rack when processing the threads at both ends.
When selecting the positioning datum, in order to ensure the coaxiality tolerance of the parts and the mutual positional accuracy of each part, all processing procedures are positioned with two center holes, which conforms to the principle of datum unification. When grinding the outer surface, the workpiece is easy to deform and elastically deform, which affects the accuracy of the piston rod.
Therefore, the hole should be repaired during processing, and the hole should be kept clean. The tightness between the hole and the top should be appropriate, and there should be good lubrication. General selection of grinding wheel: abrasive white corundum, particle size 60#, medium-soft or medium-hardness, vitrified bond, in addition, the width of the grinding wheel should be narrower to reduce the radial grinding force, pay attention to the selection of grinding amount and grinding depth during processing Be small.
When grinding φ50mm×770mm outer circle and 1:20 taper, the two processes should 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. In order to ensure the stability of the machining accuracy of the piston rod, manual alignment is not allowed in the whole process of machining.
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 advisable to use the free forging method to manufacture the blank.
