How to diagnose lubrication system faults in vertical lathe machines?

I. Preliminary Judgment Based on Fault Phenomena
Lubrication system abnormalities are usually accompanied by obvious external signs, which can be quickly identified through sensory observation:

1. Abnormal Oil Pressure: If the oil pressure alarm light on the control panel flashes or the buzzer sounds, first check if the oil pressure is too low or too high. Low pressure is often caused by insufficient oil, worn oil pump, or clogged filter; high pressure may be related to excessive oil viscosity or a stuck pressure relief valve.

2. No Oil or Slow Oil Drip at Lubrication Points: Observe whether there is continuous oil flow from the spindle box oil window and guide rail lubrication points. If there is no oil in some areas, it may be due to blocked oil pipes, a faulty oil distributor, or a damaged metering component. For example, a TH8640 vertical machining center experienced a large amount of lubricating oil leakage into the cutting fluid due to a broken Y-shaped seal in the Y-axis lead screw nut lubrication metering component.

3. Lubricating Oil Contamination or Deterioration: Take a sample to check the color and condition of the oil. If the engine oil is black, contains particulate matter, or is milky (foamy), it indicates oxidation or contamination with water or cutting fluid. The machine must be stopped immediately to check for leaks in the cooling system or poor ventilation.

4. Abnormal noises or temperature rise: Metallic friction sounds, knocking sounds, or a significant increase in bearing temperature during operation are often direct signs of insufficient lubrication. The machine should be stopped immediately, and the oil circuit checked for blockages to prevent serious accidents such as bearing seizure or failure.

II. Step-by-Step Diagnostic Process

1. Check Oil Level and Quality: With the machine stopped, check the oil level on the oil window to see if it is between 1/2 and 2/3 of the mark. Rub an oil-soaked finger between the oil and the window; there should be no grainy feel or unusual odor. If the oil level is low, add oil and observe if oil supply is restored. If the oil quality is abnormal, replace it and clean the oil tank.

2. Verify the Automatic Lubrication System's Working Status: Start the lubrication pump and observe the oil flow at each lubrication point in "manual" or "jog" mode. If oil is not flowing from a single point, disconnect the oil pipe and blow compressed air in reverse to clear any blockages. If multiple points are without oil, focus on checking the oil pump output pressure and the patency of the oil filter.

3. Troubleshoot the oil pump and pressure control components. Use a pressure gauge to measure the actual pressure of the lubrication system and compare it to the equipment's standard value (usually 0.2–0.4 MPa). If the pressure is too low, check for wear on the oil pump gears and blockage of the inlet filter. If pressure cannot be built up, check if the pressure relief valve is stuck or if the adjusting spring is faulty.

4. Check the lubrication lines and metering elements. For equipment using volumetric or progressive lubrication systems, confirm that the metering elements at each branch lubrication point are compatible and intact. There have been cases where misusing a single-line damping metering element in a volumetric system led to lubrication failure. When a leak is found, focus on checking the oil pipe joints, seals, and welds; replace the sealing material or retighten if necessary.

5. Combine with CNC system alarm information. CNC vertical lathe machines are usually equipped with lubrication monitoring functions. If the PLC reports alarms such as "lubrication timeout" or "insufficient oil pressure," the specific trigger point can be viewed through the diagnostic screen to help determine whether it is a sensor false alarm or a real fault.

III. Typical Fault Case References

Case 1: High Lubricating Oil Consumption, Oil Mixed in Cutting Fluid
The fault manifests as frequent oil replenishment required by the lubrication station. Investigation revealed that the problem was not due to insufficient lubrication intervals, but rather a damaged seal on the Y-axis leadscrew nut lubrication metering component, causing lubricating oil to flow directly into the cutting fluid system. Replacing the metering component resolved the fault.

Case 2: Lubrication Pressure Failure to Build
The lubrication pump operates normally, but the system has no pressure. Inspection revealed that the metering component model is incompatible with the system type (ASA-5Y is used for volumetric systems). Replacing it with a ZSAM-20T dedicated component restored normal operation.

IV. Preventive Diagnostic Recommendations: Record the number of times the lubrication pump is started and the pressure value weekly to establish a trend record and promptly detect performance degradation; Clean the oil nozzles and filters monthly to prevent dust blockage; Change the lubricating oil and clean the oil tank every 2000 hours. The oil should be changed after the first 300 hours of operation to remove impurities during the break-in period.