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Overheating And Non-Rotating Failure Case Analysis Of CNC lathe Spindle Motor

Overheat analysis of spindle motor of CNC lathe:
1. Overheating failure of spindle motor of CNC lathe

1. Failure phenomenon

A CNC lathe has a “knife” phenomenon during machining operation and causes tool damage.

  • a. Use manual JVC jogging mode to adjust the lathe X and Z axes to the origin, restart the processing program, and carry out a test run. When the table is quickly fed to the processing position, the spindle still does not rotate. At this point, it is diagnosed as a fault in the AC variable frequency spindle motor speed control system .
  • b. It is analyzed that the spindle motor is controlled by the AC frequency converter (because the machine tool manufacturer does not provide internal drawings of the AC frequency converter). Therefore, the “mathematical fuzzy inspection method” is used, and the internal of the AC frequency converter is regarded as a “black box”. Only the external functional interface status needs to be checked To judge.\
  • c. First check the LED alarm display content of the AC inverter control system.
  • d. In order to distinguish between overheating (referring to the overheating of the motor itself) or overloading (referring to the excessive load on the motor and excessive rotation) protection, the motor shell was very hot when touched by experience. After a period of forced cooling with a large fan, the motor heat decline. After re-commissioning, the spindle motor rotates normally; so far this example is judged to be a typical motor overheating fault. After disassembling the spindle motor, after careful inspection, it was found that the bearing of the independent cooling fan motor was damaged and the heat dissipation was poor, which caused the spindle motor to overheat and alarm, which caused the spindle of the CNC lathe to stop rotating suddenly during the machining operation, and a “gnaw” failure occurred.
  • e. After replacing the independent cooling fan motor, the CNC lathe is working normally and the fault is eliminated.

2. the failure of the spindle motor of the CNC lathe does not rotate

1. Failure phenomenon

When a CNC lathe is turned on in early production, the spindle motor does not rotate, and the spindle frequency conversion system LED also displays an alarm, but the spindle motor shell is not hot and other functions of the CNC system are normal.

2. Fault detection, analysis and processing

  • a. Use manual and JVC jogging mode to adjust the worktable to its original position, restart the lathe to reproduce the fault, so as to confirm the authenticity of the fault, and the result proves that the fault is still the same.
  • b. Touching the spindle motor housing temperature by hand is not high, according to the spindle motor has no temperature rise, so as to rule out the failure caused by excessive mechanical load.
  • c. Check the relevant control interface of the inverter and the built-in PLC of the numerical control system as shown in Figure 2; first measure +24, ALM a group of control signals are in place, no problem, suspect that the built-in overload control signal of the spindle motor is not sent to the inverter interface When the removed OHS1, OHS2 set of control signal lines is ok, and the OHS1, OHS2 signal on the side of the overheating device is detected, the closed point of the device is not closed, proving that the built-in overheating device has been damaged. Because there are no spare parts, carefully remove the overheating device, carefully grind the contacts, the trial production and processing are normal, and the fault is eliminated.

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