During industrial production, mechanical equipment is often affected by various environmental and operating conditions. As a result, servo motors can encounter several common issues.

Below, Song Nguyen shares some frequently observed servo motor faults along with their causes and corrective actions.

6 Common Servo Motor Issues

Abnormal Motion

This issue typically occurs during feeding or cutting operations, often due to unstable speed feedback signals, such as:

• Cracked or damaged encoder.
• Poor electrical contact at connectors or loose screws.

If the problem appears when the motor changes direction (forward ↔ reverse), the common causes include:

• Excessive mechanical backlash in the drive system.
• Servo controller gain set too high, causing instability.

Creeping

Usually occurs during start-up, acceleration, or low-speed operation. Common causes:

• Poor lubrication in the transmission mechanism (ball screw, linear guide).
• Low servo gain, causing slow response.
• External mechanical load is too high.

Important note:

If the coupling between the servo motor and the ball screw is loose or cracked, synchronization between the two shafts will be lost, leading to speed oscillation (intermittent fast–slow motion).

Vibration

When operating at high speeds, vibration may occur, sometimes accompanied by an overcurrent alarm.

Main causes include:

• Improper speed loop parameters, leading to instability and mechanical oscillation.
• Bearing wear at the front or rear of the motor, causing shaft imbalance.

Torque Reduction

When the motor transitions from stall torque (at standstill) to high-speed operation, a sudden drop in output torque may occur.

Primary causes:

• Reduced heat dissipation efficiency of motor windings.
• High temperature buildup in mechanical components.

At high speeds, winding temperature increases rapidly. Therefore, always check and confirm load suitability before long-term high-speed operation.

Position Error

Occurs when the servo shaft moves beyond the set position tolerance.

Common causes:

• Position tolerance limit set too tight.
• Incorrect servo parameters.
• Contaminated or damaged encoder.
• Accumulated mechanical backlash in the transmission chain.

Non-Rotation

In addition to pulse and direction signals, the control system must also send a Servo ON (enable) signal to the drive.

If the motor does not rotate, check the following steps:

• Verify that the control system outputs pulse and direction signals.
• Check the control wiring connections.
• Observe the I/O status on the driver display for confirmation.
• Check the electromagnetic brake — ensure it is released and not holding the shaft.
• Inspect both the driver and motor for hardware faults.
• Check the coupling between the servo and the ball screw — the key may have slipped, or there may be mechanical damage.

Servo motor faults can originate from electrical, mechanical, or control software issues. Accurate root-cause analysis and regular preventive maintenance are key to maintaining the precision, reliability, and lifespan of servo systems in modern industrial production.