Common Faults in CNC Lathe Hydraulic Systems

I. Main Fault Phenomena and Causes

1. Abnormal Pressure

 Insufficient Pressure: May be caused by a malfunctioning relief valve, decreased hydraulic pump volumetric efficiency, or internal leakage, resulting in insufficient clamping force or weak tool changing.

 Excessive Pressure or Pressure Fluctuations: Caused by a broken pressure regulating valve spring, a damaged pressure gauge, or system blockage, which can easily lead to pipe bursts or component damage.

2. System Leakage

 External Leakage: Caused by loose joints, aging seals, or pipe corrosion, which not only wastes oil but also poses safety hazards.

 Internal Leakage: Caused by worn valve cores or cylinder seal failure, resulting in sluggish operation and unstable speed; the fault point is difficult to diagnose.

3. Excessive Oil Temperature

 Cooler failure, prolonged overload operation, or improper oil viscosity can lead to accelerated oil oxidation, aging seals, and decreased system efficiency.

4. Noise and Vibration

Poor oil suction in the hydraulic pump can cause cavitation, producing a "clicking" sound; pump wear or loose pipelines can also cause abnormal vibration.

5. Abnormal Actuator Operation

Hydraulic cylinder creep: Air in the system, poor guide rail lubrication, or oil contamination can lead to unstable movement.

Reversing failure: Burned-out solenoid valve coils, stuck valve cores, or interrupted control signals can cause malfunctions such as the turret not rotating or the chuck not releasing.

6. Oil Contamination

External impurities or increased internal metal shavings can cause valve port blockage and accelerated pump wear, which is a major cause of cascading failures.

7. Hydraulic Pump Failure

Bearing damage, decreased volumetric efficiency, or excessive suction resistance can cause insufficient oil supply and pressure fluctuations. Regular checks of its working capacity are necessary.

II. Typical Failure Case Reference

1. Tool Post Cannot Reverse: The output signal is normal, but the movement is only in one direction. Investigation revealed a stuck solenoid valve core, which was manually corrected.

2. Excessive Z-axis movement load: The hydraulic system overheats and experiences severe pressure fluctuations. This can be resolved by adjusting the relief valve in the accumulator control valve group.

3. No response from the chuck: Insufficient hydraulic system pressure or abnormal lever movement requires checking the interface connections and oil circuit patency.