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How to choose the Materials of Hydraulic Cylinder Seals Bearing
2014-02-27 09:46:28

How to choose the Materials of Hydraulic Cylinder Seals Bearing
 

Hydraulic cylinder is the major executive component of construction machinery. Many of actions can be finished by the cylinder. Bearing bushing material has a great impact on the quality of hydraulic cylinder. Regularly the non-metallic materials which are used for bearing bushing are nylon 1010 and POM.

 

Ⅰ.Bearing Bushing Assembly Position and Gap

Bearing bushing is inserted in the groove inside the guide sleeve, supporting and guiding the piston rod. And the best designed gap between bearing bushing inner diameter and piston rod outer diameter is 0.08-0.16mm.

If the assembly gap is less than 0.08mm, it will lead to large piston rod motion resistance, tremble the hydraulic cylinder, fasten the bearing bushing wear and even accompany with noise. As a result, the bearing bushing will lose the supporting function. While the assembly gap exceeds 0.16mm, the bearing bushing easily occurs with partial rod mill and unilateral force, resulting in cylinder leakage and piston rod with oil.

 

2. The best designed gap between bearing bushing outer diameter and cylinder tube inner diameter is 0.1-0.19mm.When the assembly gap is less than 0.1mm, the piston rod motion resistance increases, it can not keep the uniform motion. And this phenomenon becomes more obviously when in high oil temperature. That will result in the bearing bushing loses the supporting function and the baffle on the piston rod or the outer edge of piston easy to scratch the inner cylinder wall, leading to serious cylinder scrapped.

It is thus clear that, assembly gap is essential to the quality of hydraulic cylinder and should be adjusted by bearing bushing.

 

Ⅱ.Performance Features of non-metallic materials

 Nylon 1010

1. Nylon 1010 has high strength, strong rigidity, good heat resistance and easy molding. Meantime it also has large hygroscopicity, shrinkage and poor dimension stability, so it is greatly influenced by temperature. Its working temperature range is -30-80℃.

POM

2.POM is a high melting point, high-density, crystalline linear polymer, has a good comprehensive performance. Its tensile strength, impact toughness, stiffness, fatigue strength, creep resistance and dimensional stability are good. POM has small water absorption, good chemical resistance and solvent resistance capability, especially organic solvents and oils. Even at high temperatures, the weight change is only 0.3% -3% in the organic solvent; the dimensional change is 0.1% to 1%. Working temperature is generally -40-140 ℃. However its disadvantage is easily decomposed by heating and more difficult molding than Nylon.

 

Ⅲ.The Application Range and Processing Method of the Two Kinds of Materials

1. Nylon 1010 has a high hardness, strong rigidity, good processing technology, but influenced greatly by temperature. It is suitable for dump trucks, construction machinery, machine tools and equipments which have small temperature influence.

2. POM has excellent mechanical properties, can be used together with a common thermoplastic molding method. So it can be widely used in the automotive industry, mechanical industry, electronic industry, building materials and other industries. In addition, POM also can be instead of copper, zinc, aluminum and other nonferrous metals, used for producing structural parts. Particularly it is suitable for making friction resistance and withstands high loads of parts.

3. Both two kinds of materials have good practicability and workability. With raw material cast into bars or pipes, can be processed molding by lathe, scraping after molding and other processing can be performed.

 

Ⅳ.Materials selection for bearing bushing

Material selection for bearing bushing is primary based on hydraulic cylinder working temperature. In general working temperature, bearing bushing can be made of nylon 1010. And in high working temperatures, it should be made of POM.


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