Piston rod

As the name implies, it is a connecting part supporting the work of piston. Most of them are used in the motion actuating parts of cylinder and cylinder. It is a moving part with frequent movement and high technical requirements. Taking the hydraulic cylinder as an example, it consists of cylinder, piston rod (cylinder rod), piston and end cap. Its processing quality directly affects the life and reliability of the whole product. Piston rod is required to be machined with high surface roughness ranging from Ra0.4 to 0.8um, which requires strict coaxiality and wear resistance. The basic characteristic of cylinder rod is slender axis processing, which is difficult to process and has been plagued by the processors.

Processing Technology

(1) When the piston rod is used normally, the piston rod should bear alternating load and the surface should be rubbed back and forth, so the piston rod should be both hard and wearable.

(2) In general, 38CrMoALA material is used for piston rod, and part of it is treated by quenching and tempering and surface nitriding. Its core hardness is 28-32HRC and surface hardness is 62-65HRC, which makes it tough.

(3) The structure of piston rod is relatively simple, but the ratio of length to diameter is relatively clear, so it belongs to slender shaft parts, but its rigidity is not very good. Therefore, in order to ensure its processing accuracy, the piston rod should be processed separately by rough turning and fine turning, so as to prevent the deformation of the workpiece in the process of processing. Also note that the center frame should be used when processing the threads at both ends.

(4) When choosing the positioning datum, all processing procedures should adopt the two-center hole positioning method to unify the specifications, in order to ensure the coaxiality tolerance of parts and the accuracy of each part's position.

(5) When grinding the surface of the outer circle, it is easy to produce elastic deformation, which affects the accuracy of the piston rod. Therefore, the center hole should be repaired and cleaned, and the tightness with the top should be appropriate, and the lubrication should be good. In addition, the width of the grinding wheel should be narrower to reduce the radial grinding force.

(6) When grinding taper, the specimen should be grinded first, and the taper can be grinded only after the grinding test is qualified.

(7) In order to ensure the stability of the piston rod processing accuracy, manual straightening is not allowed during the whole process of processing; during nitriding operation, the threaded part of the piston rod should be protected by protective devices.