02 ALARM — EXCESSIVE SPEED DEVIATION / COOLING FAN STOPPED

Identify which module displays the '02' alarm. If it is on the Power Supply (PSM/Converter), it indicates the internal cooling fan has stopped. Inspect the fan for dust or foreign material, and clean it. If the fan still does not run, check its cable connection and replace the cooling fan motor.

If the '02' alarm is on the Spindle Amplifier (SPM), it means 'Excessive speed deviation'. If the alarm occurs during motor acceleration, verify the acceleration/deceleration time parameter (e.g., parameter No. 4082). Increase the value to provide a sufficient margin for the spindle inertia.

If the alarm still occurs during acceleration, check the speed detector parameters and motor-specific parameters in the CNC. Ensure they match the motor specifications according to the FANUC parameter manual.

If the '02' alarm occurs during a cutting operation, the cutting load has likely exceeded the motor output power. Check the load meter indication and modify the CNC program to reduce the cutting load (e.g., lower feed rate, reduce depth of cut).

If the alarm occurs during cutting despite a light load, or during normal rotation, check for mechanical slippage between the spindle and the motor. Clean the pulleys and adjust the drive belt tension to prevent slipping.

If the alarm persists on the Spindle Amplifier, the feedback cable or the spindle sensor may be defective. Inspect the feedback cable and connections, and replace the cable or sensor if damaged.

If all above checks are normal and the '02' alarm persists on either the Power Supply or Spindle Amplifier, the internal control printed-circuit board or the amplifier module is defective. Replace the corresponding amplifier module.

If none of the above steps resolved the alarm, contact an authorized FANUC service representative.