The sliding or creeping of the hydraulic cylinder piston will cause the unstable operation of the hydraulic cylinder

(1) The hydraulic cylinder is sluggish inside. Improper assembly of internal parts of hydraulic cylinder, deformation, wear of parts, or out-of-limit shape and position tolerance, and excessive action resistance make the piston speed of hydraulic cylinder change with different stroke positions, causing slipping or crawling. Most of the reasons are due to the poor assembly quality of parts, surface scars or iron chips produced by sintering, which increases the resistance and reduces the speed. For example, the piston is not concentric with the piston rod or the piston rod is bent, the installation position of the hydraulic cylinder or piston rod is offset from the guide rail, and the sealing ring is installed too tight or too loose. The solution is to repair or adjust again, replace damaged parts and remove scrap iron.
(2) Poor lubrication or out-of-tolerance machining of hydraulic cylinder bore. Because the piston and cylinder barrel, guide rail and piston rod are in relative motion, if the lubrication is poor or the bore diameter of the hydraulic cylinder is out of tolerance, the wear will be aggravated and the straightness of the cylinder barrel centerline will be reduced. In this way, when the piston works in the hydraulic cylinder, the friction resistance will increase and decrease, resulting in slipping or crawling. The elimination method is to repair the hydraulic cylinder first, then prepare the piston according to the matching requirements, repair the piston rod, and configure the guide sleeve.
(3) Air enters the hydraulic pump or cylinder. Air compression or expansion will cause the piston to slip or crawl. The elimination measures are to check the hydraulic pump, set up a special exhaust device, and quickly operate the full stroke to exhaust several times.
(4) The quality of seals is directly related to slip or creep. When the O-ring is used under low pressure, compared with the U-shaped sealing ring, it is easy to slip or creep due to the high surface pressure and the large difference between dynamic and static friction resistance; The surface pressure of the U-shaped seal ring increases with the increase of the pressure. Although the sealing effect also increases, the difference between the dynamic and static friction resistance also increases. The internal pressure increases, which affects the rubber elasticity. As the contact resistance of the lip increases, the seal ring will tip over and the lip will extend, and it is also easy to lead to sliding or crawling. In order to prevent it from tipping over, support environmental protection can be used to maintain its stability.