Common Fault Types and Handling Methods of Servo Motors

As the core power component of industrial automation equipment, servo motors are widely used in robotics, CNC machine tools, precision instruments, and other fields. However, long-term high-load operation or improper use may lead to various faults, directly affecting production efficiency and equipment lifespan.Today, PHM has compiled common fault types of servo motors, practical solutions, and a handy troubleshooting mnemonic to help engineers quickly locate problems and reduce downtime losses! Let’s take a look!

1. Motor Overload/Overheating

❌ Fault Symptoms: • The motor stops suddenly during operation, and the driver displays an "overload" alarm. • The motor casing temperature rises abnormally, even becoming hot to the touch.

 ▶️ Possible Causes: 1. The load exceeds the motor's rated torque (e.g., mechanical jamming, worn transmission components).

2. Poor heat dissipation (damaged fan, dust accumulation on heat sinks).
3. Incorrect driver parameter settings (e.g., too low current limit value).

→ Handling Methods:

✅ Check the mechanical structure for jams, clean foreign objects, or lubricate transmission components.

✅ Clean the cooling fan and air ducts; replace the cooling fan if necessary.

✅ Verify driver parameters and adjust the current limit or acceleration/deceleration time. 2. Motor Vibration or Abnormal Noise

❌ Fault Symptoms: • Obvious vibration or harsh noise during operation. • Significant jitter at low speeds.  ▶️ Possible Causes: 1. Worn motor bearings or lack of lubrication. 2. Eccentric or loose coupling installation. 3. Encoder signal interference.

 → Handling Methods:

✅ Stop the machine to check bearing condition, add special lubricating grease, or replace bearings.

✅ Re-calibrate the coaxiality of the coupling (error should be <0.02mm).

✅ Inspect the encoder cable shield layer and keep it away from strong electromagnetic interference sources. 3. Encoder Faults

❌ Fault Symptoms: • The driver alarms "encoder error". • The motor cannot position accurately, with position deviation.  ▶️ Possible Causes: 1. Broken or poor contact in the encoder cable. 2. Contamination of the encoder's internal grating. 3. Signal anomalies due to strong electromagnetic interference. 

→ Handling Methods:

✅ Use a multimeter to check the continuity of the encoder circuit and replace damaged cables.

✅ Clean the encoder grating disk with alcohol swabs (operate with caution!).

✅ Install a ferrite core or replace the encoder cable with one with better shielding performance. 4. Brake Failure

❌ Fault Symptoms: • The motor shaft cannot stop immediately after power-off, with inertial sliding. • Burnt smell from the brake pads. 

▶️ Possible Causes:

1. Excessive wear of brake pads.
2. Abnormal power supply to the brake coil

. 3. Mechanical jamming causing the brake to fail to release. 

→ Handling Methods:

✅ Measure the resistance of the brake coil (typically 20–100Ω) and replace the damaged coil.

✅ Manually test the flexibility of the brake action and clean internal rust.

✅ Regularly check the thickness of brake pads (recommended to replace every 5,000 hours).

5. Communication Abnormalities

❌ Fault Symptoms: • Communication interruption between the driver and the host computer. • Jumping or loss of feedback data. 

▶️ Possible Causes: 1. Loose communication cable connectors.

2. Mismatched protocol configurations (e.g., baud rate, station number).
3. Module damage due to external voltage fluctuations.

→ Handling Methods:✅ Re-plug the communication interface and replace ordinary cables with shielded twisted-pair cables.

✅ Verify the communication parameter settings between the PLC and the driver.

✅ Install a power filter or isolation transformer.

6. Preventive Maintenance Recommendations 1. Regular Maintenance: Clean the motor surface dust every 3 months and inspect the cooling system.
7. Lubrication Management: Replace bearing lubricating grease according to the manufacturer’s recommended cycle (NSK LGHP2 is recommended).
8. Parameter Backup: Save the driver parameters in normal operation for easy fault recovery.

 💡 Appendix: Fault Handling Mnemonic 1. Troubleshooting follows order: mechanical first, then electrical; start with jams and lubrication to save time and cost!

2. No panic for motor overload: check load first, then clean dirt; maintain cooling fans regularly, calibrate parameters for safety.
3. Vibration and noise need vigilance: bearing lubrication is priority one; precise coupling alignment, keep signals away from interference.
4. Encoder faults cause inaccurate positioning: cable shielding is fundamental; clean gratings with alcohol, ferrite cores ensure stability.
5. Brake failure leads to long sliding: measure coil resistance carefully; clean rust for smooth action, replace worn parts regularly.
6. When communication is interrupted and data is lost, start by plugging and unplugging the connector; check protocol parameters thoroughly, install filters for stable voltage.
7. Three treasures of preventive maintenance: cleaning, lubrication, and parameter backup; inspect both mechanical and electrical systems to save time, reduce costs, and minimize faults! → Mnemonic Interpretation: • "Mechanical first, then electrical": Most faults originate from mechanical issues (e.g., jams, wear). Prioritizing mechanical checks quickly narrows down the problem scope. • "Cleaning, lubrication, and parameter backup": These three core maintenance actions can prevent 80% of sudden faults. • "Ferrite cores ensure stability": Encoder signals are prone to interference; adding ferrite cores or shielded cables significantly improves stability. Conclusion The stable operation of servo motors relies on daily meticulous maintenance. When encountering faults, follow the principle of "mechanical first, then electrical" to avoid costly waste from blind component replacement.