The sliding or crawling of the hydraulic cylinder piston will make the hydraulic cylinder work unstable. The main reasons for the sliding or crawling of the piston of the hydraulic cylinder:
(1) The inside of the hydraulic cylinder of the hydraulic cylinder is stagnant. The internal parts of the hydraulic cylinder are improperly assembled, the parts are deformed, worn, or the geometric tolerance exceeds the limit, and the action resistance is too large, so that the hydraulic cylinder piston speed changes with the stroke position and slips or crawls. The reason is mostly due to the poor assembly quality of the parts, the surface scars or the iron filings produced by sintering, which increase the resistance and reduce the speed. For example: the piston and the piston rod are not concentric or the piston rod is bent, the hydraulic cylinder or the piston rod is offset from the guide rail installation position, the sealing ring is installed too tightly or too loosely, etc. The solution is to repair or adjust, replace damaged parts and remove iron filings.
(2) The hydraulic cylinder's lubrication is poor or the hydraulic cylinder bore diameter is out of tolerance. Because the piston and the cylinder, the guide rail and the piston rod all move relative to each other, if the lubrication is poor or the hydraulic cylinder bore is out of tolerance, the wear will be aggravated and the linearity of the cylinder center line will decrease. In this way, when the piston is working in the hydraulic cylinder, the frictional resistance will sometimes increase and decrease, resulting in slippage or crawling. The elimination method is to grind the hydraulic cylinder first, then prepare the piston according to the matching requirements, grind the piston rod, and configure the guide sleeve.
(3) The hydraulic pump of the hydraulic cylinder or the hydraulic cylinder enters the air. Compression or expansion of air can cause the piston to slip or crawl. The troubleshooting measures are to check the hydraulic pump, set up a special exhaust device, and quickly operate the exhaust for several times throughout the entire stroke.
(4) The quality of hydraulic cylinder seals is directly related to slippage or crawling. When the O-ring seal is used under low pressure, compared with the U-shaped seal, due to the higher surface pressure and the larger difference in dynamic and static friction resistance, it is easy to slip or crawl; the surface pressure of the U-shaped seal increases with the pressure However, although the sealing effect is correspondingly improved, the difference between dynamic and static friction resistance also increases, and the internal pressure increases, which affects the elasticity of the rubber. Due to the increase in the contact resistance of the lip, the sealing ring will tilt and the lip will extend. It is also easy to cause slippage or crawling. To prevent it from tipping over, a support ring can be used to keep it stable.
