Pre-Holiday CNC Maintenance Checklist: FANUC CNC Systems, Servo Amplifiers & Motors

Introduction: Why Pre-Holiday CNC Maintenance Matters

Before long holidays, many CNC machines will face extended shutdown periods. Without proper pre-holiday inspection and maintenance, issues such as moisture ingress, dust accumulation, battery failure, and electrical faults may occur, often leading to unexpected alarms or breakdowns when production resumes.

To help customers reduce post-holiday downtime and protect critical CNC components, we recommend performing the following pre-holiday maintenance checks for CNC systems, servo amplifiers, and motors.

1. CNC System Maintenance Inspection

1.1 Paper Tape Reader (For Older CNC Systems)

Many legacy CNC systems still use paper tape readers as the program input device. System parameters and machining programs are read into the CNC through the tape reader. If contamination is present on the optical reading components, incorrect data input may occur.

Inspection & Maintenance Points:

• Regularly inspect and clean the reading head (light-emitting and light-receiving sections).

• Clean the tape pressure plate and tape guide path to remove dust and oil residue.

• Clean and lubricate all moving parts, including:

  • Drive rollers

  • Guide rollers

  • Pressure rollers

  • Tension arm rollers

Ensuring smooth movement and clean optical surfaces helps prevent program reading errors.

1.2 Battery Maintenance (CMOS Memory)

For CNC systems that use CMOS memory to store parameters and machining data, batteries are critical to prevent data loss during power-off periods.

Key Recommendations:

• Batteries are automatically charged when the machine is powered on.

• Under normal conditions, batteries can retain data for over 1000 hours after power-off.

• For machines that will remain idle for long periods, power on the machine periodically according to the manual to recharge the battery.

• If a battery alarm appears on the CRT screen or indicator lights, the battery voltage is too low and must be replaced.

Important Notes:

• Always replace the battery while power is ON to avoid data loss.

• Never reverse battery polarity.

1.3 CNC Cabinet Door & Air Filter Management

Proper sealing of CNC cabinet doors is critical for system reliability.

Best Practices:

• Avoid opening CNC cabinet doors unnecessarily, especially during operation.

• Never run the machine with cabinet doors open for heat dissipation.

• Clean or replace air filters regularly.

Opening cabinet doors allows dust, oil mist, and metal particles to enter, which can:

• Reduce insulation resistance

• Cause PCB and electronic component failure

• Lead to irreversible damage

For machines with spindle control systems installed in power cabinets, poor sealing may also cause spindle control failures.

1.4 Power-On Operation During Long-Term Shutdown

For CNC machines that will not be used for an extended period:

• Power on the CNC system regularly, even with machine axes locked.

• Allow the system to run idle to generate internal heat.

• In high-humidity environments, daily power-on is strongly recommended.

This helps remove moisture inside the CNC cabinet and maintains stable electrical performance. In practice, machines left unpowered during humid periods are far more likely to experience failures.

2. Servo Amplifier Maintenance Inspection

Servo amplifiers are sensitive electronic components that require a stable operating environment.

2.1 Operating Environment (Daily Inspection)

• Ambient Temperature: The temperature around the high-power panel should be between 0–45°C, and inside the electrical cabinet, it should be 0–55°C.

• Humidity: Must be below 90% RH (Non-condensing).

• Dust and Oil Mist: These substances should not be adhered to or near the servo amplifier.

• Cooling Air Passage: The cooling fan motor must operate normally without any obstructions to airflow.

• Abnormal Vibration and Noise: There should be no unusual noises or vibrations that were not previously present. Vibration near the servo amplifier must be below 0.5G.

• Power Supply Voltage: For 200V input types, the range should be 200–240V. For 400V input types, the range should be 400–480V.

2.2 Servo Amplifier

• Overall Unit (Daily): There should be no abnormal noise or odors, and no accumulation of dust or oil mist.

• Screws (Periodic): Screws must not be loose.

• Fan Motor (Daily): There should be no abnormal vibration or noise, and it must rotate normally. It should be free of dust and oil mist.

• Connectors (Periodic): Connectors must not be loose or damaged.

• Cables (Periodic): There should be no signs of overheating or deterioration of the outer sheath (such as discoloration or cracking).

2.3 CNC System (Daily Inspection)

• Battery for Absolute Pulse Coder: The machine operation panel or screen must not display a low battery voltage alarm for the absolute pulse coder.

2.4 External Equipment (Periodic Inspection)

• Electromagnetic Contactor: There should be no abnormal noise or chattering during operation.

• Leakage Circuit Breaker: The leakage tripping device must function correctly.

• AC Reactor: There should be no abnormal vibration or noise.

Important Notes:

1. Fan Motors: These are components requiring regular maintenance. It is recommended that users perform daily inspections and carry out preventative replacement.

2. Maintenance Parts: Both fan motors and batteries require periodic maintenance; it is advised to keep spare parts on hand.

3. Motor Maintenance Inspection

3.1 External Appearance of the Motor

• Cracks and Deformation: Check the motor for any scratches, cracks, deformations, or bulging. If internal parts are visible or if the motor interferes with surrounding components, replace the motor or the affected parts immediately. Minor surface peeling or scratches may sometimes be repaired; please consult the maintenance department.

• Moisture and Stains: Clean off any moisture or stains immediately upon discovery. If the motor is constantly wet due to cutting fluids or condensation, preventative measures must be implemented.

3.2 Operating Conditions

• Temperature and Humidity: Ensure the motor is used according to the machine's specifications. Generally, the ambient temperature should be maintained between 0–40°C (30°C for spindle units), and the environment should be free of condensation.

3.3 Connection Status

• Cables: Check for damage to the cable jacket, exposed conductors, damaged conduits/supports, abnormal bending, or loose terminals. If there are signs of liquid seepage, it may enter the motor or connectors; confirm and take preventative action.

• Connectors and Terminals: Check for cracks, exposed terminals, looseness, or falling off. Any liquid causing a fault must be removed. Damaged connectors or terminals must be replaced. For resin-molded motors (like linear motors), the entire motor may need replacement if these parts are damaged.

3.4 Motor Operation

• Noise and Vibration: Check for abnormal noise and vibration both during rotation (axis movement) and when stopped. Abnormal noise during rotation may indicate issues with the bearings or internal motor components.

• Running State: Confirm the motor runs smoothly and normally. If the circuit breaker trips during operation, it may be due to an abnormality in the motor windings.

• Overheating: Check for abnormal heat during a normal duty cycle. Note: The motor surface can be very hot during or right after operation; do not touch it with bare hands. Use temperature labels or surface thermometers.

3.5 Electrical Characteristics

• Winding Resistance: If the resistance value exceeds the specified range, the motor must be replaced. Note: When measuring winding resistance, disconnect the motor from the amplifier and measure via the power line or connector closest to the motor.

• Insulation Resistance: Refer to the specific measurement methods and judgment standards provided in separate tables.

3.6 Cooling Fan (For motors equipped with fans)

• Noise and Vibration: Confirm there is no abnormal noise or vibration and that air is blowing normally. Abnormal noise when the motor is stopped may be caused by the fan motor itself.

• Running State: Replace the fan motor if it does not rotate when powered, if the blades do not move even when turned by hand, or if air is not being blown despite rotation (which may be due to accumulated chips or debris).

3.7 Forced Cooling Device (For liquid-cooled or external cooling systems)

• Condensation (Overcooling): Ensure forced cooling does not cause condensation on the motor surface. This often happens if the cooling system continues to run after the machine stops. Wipe off any condensation or water droplets immediately to prevent shortening the motor's lifespan.

• Leakage and Clogging: Check cooling pipes for leaks or blockages. Do not drive the motor until these are resolved. If liquid leaks from the spindle motor (main body) through a through-hole, the cooling joint may need replacement. If liquid leaks from a linear motor body (coil slider), the slider must be replaced. After any leakage, perform electrical performance tests (winding and insulation resistance).

4. Recommended Operating Environment (Reference)

This device must be operated and maintained within specific environmental parameters to ensure its performance and longevity:

• Temperature: The operating temperature range is 0°C to 58°C, while the storage and transportation range is -20°C to 60°C, with a maximum temperature fluctuation of 0.3°C per minute.

• Humidity: Relative humidity should normally remain below 75%, though it can reach up to 95% for short periods (less than one month), provided there is no condensation.

• Vibration Resistance: During operation, vibration must be kept below 0.5G (compliant with IEC68-2-6 standards), while non-operating vibration should stay below 1.0G.

• Altitude: The equipment is designed to operate at altitudes up to 1,000 meters, and can withstand altitudes up to 12,000 meters when not in use.

• Atmospheric Conditions: The surrounding environment must be free from corrosive gases and protected from direct contact with cutting fluids, lubricants, or metal chips.

Conclusion

A thorough pre-holiday maintenance inspection is one of the most cost-effective ways to protect your CNC equipment, reduce unexpected downtime, and extend the service life of critical components. By following these inspection guidelines for CNC systems, servo amplifiers, and motors, you can ensure a smooth restart after long shutdown periods.

Data Source: Beijing FANUC

This article is intended for technical reference and preventive maintenance guidance.