Setting Sensor Gap on Fanuc Spindle Motor

Setting the Sensor Gap

The following steps are for a NEW INSTALL of a Spindle Motor when the machine has a belt driven spindle. When belt tension makes the sensor gear ride too close or too far away from the sensor, an Alarm 2 or an Alarm 31 – speed deviation alarm – will occur.

When this happens, follow the steps below to re-gap the sensor:

  1. Undo the fan wires inside the terminal box.
  2. Remove the 4 bolts holding the fan shroud and fan to the motor. 
  3. Remove the 4 screws holding the sensor cover to the motor.
  4. Loosen the 2 screws holding the sensor in place and slide a piece of standard copy paper or cigarette cellophane between the sensor and gear. Leave just enough gap to slide the paper out between the gear and sensor. (Lightly press the sensor to the gear using the paper or cellophane to set the gap.)
  5. Tighten the 2 screws holding the sensor in place and slowly turn the motor shaft to make sure the gear and sensor are not rubbing.
  6. Re-attach all the bolts and screws in reverse order.

Get your Fanuc CNC machine back up and running.

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