The sliding or crawling of the hydraulic cylinder piston will make the hydraulic cylinder work unstable. The main reasons are as follows:

　　The inside of the hydraulic cylinder is stagnant. The internal parts of the hydraulic cylinder are improperly assembled, deformed, worn, or the shape and position are out of tolerance, and the action resistance is too large, which causes the piston speed of the hydraulic cylinder to vary with the stroke position, causing slippage or crawling. Most of the reasons are due to the poor assembly quality of the parts and the iron filings on the surface due to sintering, which increases the resistance and reduces the speed. If the piston and the piston rod are not concentric or the piston rod is bent, the installation position of the hydraulic cylinder or the piston rod on the guide rail is offset, and the sealing ring is too tight or too loose. The solution is to re-repair or adjust, replace damaged parts, and remove scrap iron.

　　The hydraulic cylinder is poorly lubricated or the bore diameter of the hydraulic cylinder is out of tolerance. Due to the relative movement between the piston and the cylinder, the guide rail and the piston rod, if the lubrication is poor or the diameter of the hydraulic cylinder is out of tolerance, it will aggravate the wear and reduce the linearity of the cylinder center line. In this way, when the piston works in the hydraulic cylinder, the frictional resistance will increase and decrease, resulting in sliding 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.

　　 The hydraulic pump or hydraulic cylinder enters the air. The 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 entire stroke for several times of exhaust.

　　 The quality of the seal is directly related to sliding or crawling. Compared with the U-shaped sealing ring, when the O-shaped sealing ring is used under low pressure, due to the higher surface pressure, the difference in dynamic and static friction resistance is larger, and it is easy to slip or crawl. As the pressure increases, the surface pressure of the U-shaped sealing ring increases. 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. As the contact resistance of the lip increases, the sealing ring will overturn and the lip will stretch, which may easily cause sliding or crawling. In order to prevent it from tipping over, a support ring can be used to maintain its stability.