What Is The Reason For The Hydraulic Cylinder Piston Rod Crawling?

- Sep 09, 2019-

The factors that generally cause crawling are as follows: It is necessary to determine which point is wrong according to the specific situation:

 

1. The hydraulic cylinder caused by the problem of seal material is crawling at low speed. The common sealing materials for hydraulic cylinders are nitrile rubber, polyurethane rubber, polytetrafluoroethylene, etc. Due to the hardness, strength and followability of the material, it directly affects the sliding surface. Friction, in addition to the lip seal, the fluctuation of the oil pressure causes a change in the contact pressure between the seal area and the contact surface, thereby causing a change in the speed of the hydraulic cylinder.

 

2. The influence of the machining accuracy of the parts, the machining accuracy of the inner wall of the cylinder and the surface of the piston rod, has a great influence on the low speed stability of the hydraulic cylinder. In particular, the geometric accuracy has a greater influence. The straightness is the key. The straightness guarantee is the most difficult to ensure during the machining process. For the hydraulic cylinder with a long stroke, the straightness of the inner wall of the hydraulic cylinder and the surface of the piston rod is The main factors affecting the low speed stability of hydraulic cylinders.

 

3. The hydraulic cylinder has a low-speed crawling caused by the presence of gas in the rod cavity and the rodless cavity. Since the gas is mixed in the hydraulic oil, the volume changes under the action of the pressure, and even a gas moment occurs under the action of the high pressure, thereby causing the hydraulic pressure. The speed of the cylinder is unstable.

 

4. The low-speed crawling caused by the improper design of the hydraulic cylinder, the sliding fit clearance between the internal piston of the hydraulic cylinder and the cylinder block, the piston rod and the guide sleeve is too large, causing uneven pressure on the sliding surface, resulting in uneven friction, causing The hydraulic cylinder crawls at a low speed; if the sliding fit clearance is too small, and there are tolerances in the manufacture of the parts, the pressure on the sliding surface is uneven, resulting in uneven friction, causing the hydraulic cylinder to crawl at a low speed.

 

5. The low-speed crawling caused by the uneven friction of the guiding elements in the hydraulic station. The common guiding materials for hydraulic cylinders are QT500, ZQAL9-4, non-metallic support rings, etc., especially the non-metallic support rings are not uniform in size, and some non-metallic support rings are used with oil. The temperature change size increases or decreases, that is, the dimensional stability in the oil directly causes a change in the matching clearance, which easily causes the speed of the hydraulic cylinder to be unstable.

 

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