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

1. Internal astringency of hydraulic cylinder. Improper assembly of parts inside hydraulic cylinder, deformation, wear, or form position tolerance overlimit, excessive movement resistance make the speed of hydraulic cylinder piston change with the travel position, appearing slipping or crawling. The reason is most poor assembly quality of parts, surface scarring or sintering generated iron chips, so that resistance increases and speed drops, such as piston and piston rod different center or piston rod bending, hydraulic cylinder or piston rod to guide the location of migration, sealing ring installed too tight or loose and so on. The solution is to repair or adjust, replace damaged parts and remove scrap.

2. Poor lubrication or poor machining of hydraulic cylinder aperture. Because the piston and cylinder, guide rail and piston rod have relative movement, if the lubrication is bad or hydraulic cylinder aperture is out of tolerance, it will aggravate the wear, so that the straightness of cylinder center line is reduced. In this way, the piston working in the hydraulic cylinder, the friction resistance will be larger and smaller, resulting in sliding or crawling. The elimination method is to first grinding hydraulic cylinder, and then according to the requirements of the preparation of piston, grinding piston rod, configuration guide sleeve.

3. The hydraulic pump or hydraulic cylinder enters the air. Compression or expansion of air causes the piston to slip or crawl. The elimination measure is to check the hydraulic pump, set special exhaust device, quick operation of full stroke back and forth several exhaust.

4. Seal quality is directly related to sliding or crawling. When the o ring is used under low pressure, compared with u-ring seal, it is easy to slip or crawl due to high surface pressure and large difference of static and static friction resistance. U-shaped seal surface increases with the increase of pressure as the pressure. Although seal effect also increase, the dynamic and static friction resistance is larger, the difference between the internal pressure increases, which have the influence of rubber elasticity. The contact resistance is increased due to the lip margin. Sealing ring will be tilting and lip edge elongation, also easy to cause slipping or crawl, which can be used to prevent the tilting bearing ring keep its stability.