Selection Criteria for Hydraulic Cylinder Seal Supporting Material

Hydraulic cylinder is completed by the fuel tank of the main construction machinery parts. Bearings, punches impact on the quality of the cylinder bushing material, bearing non-metallic materials are usually used for nylon 1010 and polyoxymethylene liner.

First, the bearing assembly parts and assembly clearance

1. The inner sleeve of the bearing sleeve on the guide sleeve (the material is ductile iron), the punch acts as the inner and outer diameter of the piston rod to guide and support the optimum design of the piston rod, 0.08-0.08 mm. When the resistance is less than 0.08 mm, the piston rod and the cylinder shaking movement, the bearing with sound, when the liner wear faster, serious, loss of support role; clearance more than 0.16 mm, it is easy with the piston rod partial grinding, lining Sets of force, unilateral leak cylinder, piston rod oil.

2. Bearing bushings and cylinder contact within the cylinder, 0.1-0.1 mm is the best design of the outer diameter of the gap. And the movement resistance of the piston rod is increased so that uniform movement can not be maintained and the oil temperature is high. Propagation is less than the bearing lining, punch piston rod baffle or piston is easy to cut into the outer cylinder wall, serious waste when the cylinder.

Visible, is essential to the quality of the cylinder assembly gap. Assembly clearance should be adjusted bearing bushings, as shown in Figure 1, bearing bushing assembly to adjust the gap to the size of the main B, the tolerance requirements of millimeters. Two kinds of materials

Second, the performance characteristics

Nylon 1010 strength, rigidity, heat resistance, forming technology is better; water absorption and shrinkage, dimensional stability, greatly affected by temperature, the working temperature range of – 30 ~ 80 ℃.

POM is a high melting point, high density, crystalline linear polymer, punch has a good overall performance, tensile strength, impact toughness, hardness, fatigue strength and creep resistance and dimensional stability are very good, small Water absorption, chemical resistance and solvent resistance, especially good resistance to organic solvents and oils. Even at high temperatures, the change in weight of polyoxymethylene in general organic solvents is only 0.3% to 0.3% with only 0.1% to 0.1% change in size. Operating temperature is generally – 40 ~ 140 ℃. The disadvantage is the thermal decomposition, forming more difficult than nylon.

Third, the scope of application of the two materials and treatment methods

1. Nylon 1010 has a high hardness, rigidity, good processing technology, but subject to a great temperature. Applicable to construction machinery, press machine equipment, such as less affected by temperature.

2. POM has excellent mechanical properties, and can be used for thermoplastic general molding method, in the automotive industry, machinery industry, electronics industry, building materials and other industries widely used. Instead of copper, zinc, aluminum and other non-ferrous metals production structure POM can be. Particularly suitable for the production of frictional resistance and high load part.

3. The two materials have good practicability and operability. Cast into a rod or pipe with raw materials, can be processed with an ordinary lathe molding, you can also adjust their research and other processing after molding. As a result, it is applicable not only to mechanical manufacturing, but also to maintenance of equipment.

Fourth, select the lining material

According to the above two material properties of the analysis, the working temperature of the cylinder, punch to determine the material selected as the main basis for the bearing bush. Nylon 1010 with the general operating temperature; usually, the cylinder at high temperatures should be selected POM as bearing bushings. Our factory has been producing a number of nylon 1010 bearing cylinder cylinder, processing dimensions are in line with the design, punch assembly gap adjustment is also within the scope of the design requirements. Perform the pressure test as required to assemble the cylinder. But because it is produced in the summer, the higher the ambient temperature, the cylinder piston rod shaking part, accompanied by sound, and so on, and so on.

Serious maintenance found that nylon bearing dimensions outside the tolerance, the direction of the standard diameter than 0.10 mm. Punch In order to verify the validity of this conclusion, we have done an experiment. Spend a few minutes in the size of the nylon 1010 bush and place it into the beaker to add enough water to the boil. 8-10 hours, measurement and expansion of more than 5%. Punch using paraformaldehyde as a bearing bush, cylinder crawling, trembling, and this phenomenon, such as sound after being eliminated.

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