EXTENSION ROD

Piston rod introduction

The piston rod is a connecting part that supports the work of the piston. Most of them are used in the cylinder and cylinder movement executing parts, and are a moving part with frequent movement and high technical requirements. Taking a hydraulic cylinder as an example, it consists of a cylinder, a piston rod (cylinder rod), a piston, and an end cover. The quality of its processing directly affects the life and reliability of the entire product. The piston rod has high processing requirements, and its surface roughness requirement is Ra 0.4-0.8 μm, which requires strict requirements on coaxiality and wear resistance. The basic feature of the cylinder rod is the slender shaft machining, which is difficult to process and has always plagued the processor.

Piston composition

The piston assembly includes: a piston, a piston ring, a support ring, a piston rod, and the like. Depending on the type of construction, the piston can be divided into a cylindrical piston (longer than the diameter), a disc piston (longer than the diameter), a stepped piston, a combined piston and a plunger piston.

Role of the piston rod

The function of the piston rod is to connect the piston and the crosshead, transmit the force acting on the piston and drive the piston to move.

Basic requirements for the piston rod:

(1) have sufficient strength, rigidity and stability;

(2) Good wear resistance and high processing precision and surface roughness requirements;

(3) Minimize the effect of stress concentration on the structure;

(4) Ensure reliable connection and prevent loosening;

(5) The design of the piston rod structure is to facilitate the disassembly and assembly of the piston. [2] 

Processing Technology

The piston rod is rolled to improve the surface corrosion resistance and delay the generation or expansion of fatigue cracks, thereby improving the fatigue strength of the cylinder rod. By rolling forming, the rolling surface forms a cold hardening layer, which reduces the elastic and plastic deformation of the grinding contact surface, thereby improving the wear resistance of the cylinder rod surface and avoiding burns caused by grinding. After rolling, the surface roughness value is reduced to improve the compounding property. At the same time, the friction damage to the sealing ring or the sealing member during the movement of the cylinder rod piston is reduced, and the overall service life of the oil cylinder is improved. The rolling process is an efficient and high quality process.

Product Usage

Piston rods are mainly used in hydraulic and pneumatic, engineering machinery, piston rods for automobile manufacturing, guide columns for plastic machinery, roller shafts for packaging machinery and printing machinery, textile machinery, shafts for conveying machinery, and linear optical axes for linear motion.

Stainless steel piston rod

Stainless steel piston rods are mainly used for hydraulic and pneumatic, engineering machinery, and piston rods for automobile manufacturing. The piston rod is processed by rolling, and the residual stress on the surface layer is left to help the surface of the surface crack, which hinders the expansion of the erosion. Thereby, the surface corrosion resistance is improved, and the generation or expansion of the fatigue crack can be delayed, thereby improving the fatigue strength of the cylinder rod. By rolling forming, the rolling surface forms a cold hardening layer, which reduces the elastic and plastic deformation of the grinding contact surface, thereby improving the wear resistance of the cylinder rod surface and avoiding burns caused by grinding. After rolling, the surface roughness value is reduced to improve the compounding property. At the same time, the friction damage to the sealing ring or the sealing member during the movement of the cylinder rod piston is reduced, and the overall service life of the oil cylinder is improved.

The rolling process is a high-efficiency and high-quality process. The 160mm diameter doctor's cutting pinch is used as an example to show the rolling effect. After rolling, the surface roughness of the cylinder rod is reduced from Ra3.2 to 6.3 μm before the rolling of the building to Ra 0.4 to 0.8 μm, the surface hardness of the cylinder rod is increased by about 30%, and the fatigue strength of the cylinder rod surface is increased by 25%. The service life of the cylinder is increased by 2 to 3 times, and the rolling process is improved by about 15 times compared with the grinding process. The above data shows that the rolling process is highly efficient and can greatly improve the surface quality of the cylinder rod.

Cause of overheating of the piston rod

(1) The piston rod and the stuffing box are deflected during assembly, causing local friction and should be adjusted in time;

(2) The holding spring of the sealing ring is too tight and the friction is large, which should be adjusted properly;

(3) The axial clearance of the sealing ring is too small, and the axial clearance should be adjusted according to the specified requirements;

(4) If the amount of oil is insufficient, the amount of oil should be increased appropriately;

(5) The piston rod and the sealing ring are not well worn, and the running-in should be strengthened during the research;

(6) Impurities are mixed in the gas and oil and should be cleaned and kept clean.