The hydraulic cylinder often has a jumping and stopping movement state during operation, which we call creeping phenomenon. This phenomenon is especially easy to occur at low speed, which is also one of the main faults of hydraulic cylinder.To solve the problem of hydraulic cylinder creep, we must study the cause of this phenomenon. After summarizing, we found that the cause for hydraulic cylinder creep not only have something to do with the hydraulic cylinder itself and also related to other factors outside the cylinder. Let’s talk about it today.
Internal causes of hydraulic cylinder creep failure
① There is residual air in the cylinder, and the working medium forms an elastic body.
Troubleshooting method: Fully exhaust the air; check whether the diameter of the hydraulic pump suction pipe is too small, and the suction pipe joint should be well sealed to prevent the pump from sucking air.
② The sealing friction is too large.
Troubleshooting method: The piston rod and the guide sleeve are matched with H8/f8, and the depth and width of the sealing ring groove are strictly made according to the dimensional tolerance; if a V-shaped sealing ring is used, adjust the sealing friction to a moderate degree.
③ The sliding parts of the hydraulic cylinder are severely worn, strained and bitten.
a. The load and hydraulic cylinder are poorly centered.
b. The installation and adjustment of the mounting bracket are poor.
Troubleshooting method: Carefully align after reassembly, and the rigidity of the mounting bracket should be good.
c. The lateral load is large.
Troubleshooting method: Try to reduce the lateral load, or improve the ability of the hydraulic cylinder to withstand the lateral load.
d. The cylinder or piston assembly expands and deforms under force.
Troubleshooting method: Trim the deformed parts, and replace the relevant components when the deformation is serious.
e. Electrochemical reaction occurs between the cylinder and the piston.
Troubleshooting method: Replace the material with less electrochemical reaction or replace the parts.
f. The material is poor, easy to wear, tear, and bite.
Troubleshooting method: Replace the material and perform appropriate heat treatment or surface treatment.
g. There are many impurities in the oil.
Troubleshooting method: Replace the hydraulic oil and oil filter after cleaning.
④ The piston rod is bent in full length or partly.
Troubleshooting method: Correct the piston rod; when the piston rod of the horizontally installed hydraulic cylinder is too long, it should be supported.
⑤ The coaxiality between the inner hole of the cylinder and the guide sleeve is not good, causing the phenomenon of creeping.
Troubleshooting method: Ensure the coaxiality of the two.
⑥ The linearity of the cylinder bore is poor (drum shape, taper, etc.).
Troubleshooting method: Repair by boring and grinding, and then match the piston according to the bore of the cylinder after boring or add an O-ring rubber seal.
⑦ The nuts at both ends of the piston rod are too tight, making its coaxiality poor.
Troubleshooting method: The nuts at both ends of the piston rod should not be too tight. Generally, they can be tightened by hand to ensure that the piston rod is in a natural state.
External causes of oil cylinder creep
The reasons outside the hydraulic cylinder may be the following 5:
① The rigidity of the motion mechanism is too small, forming an elastic system.
Elimination method: appropriately increase the rigidity of the relevant components and reduce elastic deformation.
② The installation position accuracy of the hydraulic cylinder is poor.
③ The difference between the static friction coefficient and the dynamic friction coefficient between the relatively moving parts is too large, that is, the friction force changes too much.
Elimination method: apply a layer of anti-climbing oil (such as molybdenum disulfide lubricant) between the relative moving surfaces and ensure good lubrication conditions.
④ The manufacturing and assembly quality of the guide rail is poor, which increases the friction and the force is not good.
Elimination method: improve the manufacturing and assembly quality.
⑤ Air is mixed in the oil, and the working medium forms an elastic body. This is one of the important reasons for the crawling phenomenon of the hydraulic cylinder movement.
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