During machine operation, the FANUC spindle motor is cooled by an internal cooling fan. If the fan stops working or rotates abnormally, the spindle motor may overheat, which can lead to machine alarms or even machine stoppage.
In environments where coolant or oil mist is present, contaminants may accumulate on the fan. In extreme situations, these foreign materials may ignite due to excessive heat.
For safety reasons, the spindle motor fan cover is made of flame-retardant resin (V0 level according to UL94 standards). Under normal conditions without foreign materials, fire will not spread. However, regular inspection and cleaning are strongly recommended.
It is recommended to inspect and clean the spindle motor fan every 3 months.
1. Visual Inspection
While the machine is powered on, visually check whether the fan is rotating.
Inspection method
Observe the spindle motor fan during operation.
Judgment
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If the fan rotates normally → No abnormality
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If the fan stops rotating → The fan must be replaced
2. Fan Current Measurement
Measuring Equipment
Clamp meter
Measuring Location
Fan power cable inside the machine electrical cabinet
Measuring Method
Install the clamp meter on one of the fan power cables and measure the current value.
Judgment Criteria
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If the measured current is below the reference value and not zero, the fan is operating normally.
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If the measured current is higher than the reference value or equal to zero, the fan should be replaced.
Below is the reference current value for αiI-B and βiI-B series 200V spindle motors.
| αil-B | αilP-B | αilT-B | αilPT-B | βil-B | βilP-B | βilT-B | βilC-B | Reference Value[A] |
| 1/1.5 | 1/1.5 | 0.11 | ||||||
| 2/3 | 2/3 | 3/6 | 3/6 | 0.11 | ||||
| 6/8 | 6/8 | 8/12 | 12 | 12 | 8 | 0.16 | ||
| 12~22 | 12~22 | 12~22 | 22 | 15 | 15~30 | 15 | 0.24 | |
| 30/40 | 30/40/50 | 40 | 0.54 | |||||
| 50/60 | 60 | 0.50 |
If you need the current reference values for other spindle motor fan series, please contact the REACO CNC technical team for assistance.
3. Insulation Resistance Measurement
Measuring Equipment
Megohmmeter (Insulation resistance tester)
Measuring Location
Circuit breaker or terminal block connected to the fan power cable inside the machine cabinet.
Measuring Method
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Turn off the machine power.
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Measure insulation resistance between one of the three power wires and ground.
Judgment Criteria
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Insulation resistance above 100MΩ → Normal
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Insulation resistance below 100MΩ → Replace the fan
If the fan shares a circuit breaker with other equipment, disconnect the fan power cable and measure between the cable and ground.
4. Fan Removal Procedure
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Confirm that the power supply is completely turned off
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Remove the four screws of the spindle motor terminal box
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Remove the terminal box cover
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Use a pointed tool to disconnect the fan power cables from the terminal block
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Disconnect the ground wire
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Remove the four screws on the red fan cover
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Remove the fan assembly from the motor body
5. Fan Cleaning
Cleaning steps:
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Use air gun to remove dust and contaminants from the red fan cover
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Blow compressed air through the cone opening and impeller gap to remove internal debris
If the fan is heavily contaminated, replacing the fan is recommended.
6. Fan Reinstallation
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Pass the fan power cables through the rubber sleeve into the terminal box
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Install the four screws of the red fan cover
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Connect the fan cables and ground wire to the terminal block
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Reinstall the terminal box cover
Fan Cable Wiring
The fan cable includes:
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3 power wires
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1 ground wire
Connection details:
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Red wire → FMU terminal
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White wire → FMV terminal
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Blue / Black wire → FMW terminal
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Yellow-green wire → Ground terminal screw
7. Operation Check
After installation, confirm:
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The fan rotates normally
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The rotation direction is correct
8. Fan Replacement
After removing the fan from the motor body:
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Remove the four screws inside the red cover
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Remove the four screws outside the red cover
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Replace the fan unit
Conclusion
Regular inspection and cleaning of the FANUC spindle motor cooling fan is an important preventive maintenance task. Proper maintenance can effectively prevent spindle motor overheating, reduce machine downtime, and extend the service life of CNC equipment.
Reference Source: Beijing FANUC. This article is based on technical documentation provided by Beijing FANUC.
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