The crawling phenomenon in hydraulic cylinders may be caused by the following reasons:
- Air Infiltration into the Cylinder:
Air entering the hydraulic cylinder increases the compressibility of the fluid, leading to significant pressure fluctuations during movement. This results in intermittent motion or uneven speed (“crawling”). - Trapped Air in the Cylinder:
Gas trapped in the rod-side or non-rod-side chambers undergoes volume changes under pressure, potentially causing gas implosion, which destabilizes cylinder speed. - Improper Design Clearances:
Excessive or insufficient sliding fit clearances between the piston and cylinder bore, or between the piston rod and guide sleeve, create uneven pressure distribution on sliding surfaces. This causes inconsistent friction and low-speed crawling. - Uneven Friction from Guide Components:
Non-metallic support rings with uneven dimensions or thermal expansion/contraction (due to oil temperature changes) alter fit clearances, leading to speed instability. - Seal Material Issues:
Inadequate hardness, strength, or conformability of seals affects friction against sliding surfaces, resulting in speed variations. - Poor Machining Precision:
Low straightness of the cylinder bore’s inner wall or piston rod surface compromises stability during low-speed operation. - Low Installation Accuracy:
Misalignment with guide rails, positional deviations, or improper installation can destabilize cylinder motion. - Piston Rod Defects:
Bent piston rods, insufficient rigidity, or poor concentricity disrupt smooth movement. - Other Factors:
- Poor lubrication of guide rails.
- Improper seal tightness.
- Clogged filters.
These issues can further destabilize cylinder performance.