Servo Drive Troubleshooting: Causes & Fixes

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Problems on this page:

Following (position) error fault Servo overheating or overload Oscillation or hunting Encoder or feedback fault Overvoltage fault when braking Holding brake not releasing or not holding Lost reference position after power off Communication fault with the controller

Following (position) error fault

Hits OEE: Availability

Symptoms: Drive faults on excessive following error and the axis stops mid-move.

Mechanical binding or overload

Check for binding and jams; confirm the load and inertia.

Tuning gains too low

Re-tune the loop gains for the load.

Encoder feedback fault

Check the encoder, coupling and cable.

Prevention: Mechanical condition checks, correct tuning, encoder integrity.

Servo overheating or overload

Hits OEE: Availability

Symptoms: Drive or motor overtemperature or overload fault, thermal trips.

Continuous load above rating

Check the duty cycle and sizing; reduce load or upsize.

Mechanical drag or misalignment

Fix binding, alignment and lubrication.

Cooling or ambient issue

Clean heatsinks and fans; check panel cooling.

Prevention: Correct sizing, mechanical health, cooling maintenance.

Oscillation or hunting

Hits OEE: Performance

Symptoms: Axis vibrates, buzzes or oscillates around position, poor finish.

Gains too high

Reduce the loop gains; re-tune for stability.

Mechanical backlash or resonance

Remove backlash; add a notch filter for resonance.

Loose coupling or mounting

Tighten the coupling and mounts.

Prevention: Stable tuning, backlash control, secure mechanics.

Encoder or feedback fault

Hits OEE: Availability

Symptoms: The drive faults on feedback loss or an encoder error and the axis stops.

Damaged or loose feedback cable

Check the connectors and replace cables worn by drag chains.

Cable shield not grounded correctly

Ground the shield the way the drive maker shows.

Encoder damaged by impact or contamination

Replace the encoder or the motor.

Feedback cable run next to power cables

Separate feedback and power cables.

Prevention: Flex-rated cables in drag chains, inspected on a schedule.

Overvoltage fault when braking

Hits OEE: Availability

Symptoms: The drive trips on DC bus overvoltage while decelerating or lowering a load.

Deceleration too fast for the energy returned

Lengthen the deceleration ramp.

Braking resistor missing, failed or too small

Check the resistor and its wiring and size it for the duty.

Brake resistor parameters wrong

Set the resistor parameters to match the fitted resistor.

Frequent lowering of heavy loads

Consider a regenerative supply where lowering is frequent.

Prevention: Braking resistor checked after any repeated overvoltage faults.

Holding brake not releasing or not holding

Hits OEE: Availability

Symptoms: The motor strains against the brake, or a vertical axis sags when stopped.

No brake supply voltage

Check the brake supply and the brake output on the drive.

Brake worn or contaminated

Test the holding torque as the maker describes and replace the brake if it fails.

Brake timing parameters wrong

Set the brake open and close delays to the drive maker's guidance.

Work done on a vertical axis without support

Support vertical axes mechanically before any work.

Prevention: Brake tests on vertical axes at planned intervals.

Lost reference position after power off

Hits OEE: Quality

Symptoms: The axis needs homing after every power cycle, or positions are offset after a restart.

Encoder backup battery flat

Replace the battery as the maker describes, usually with power on.

Axis not homed after power-up

Home incremental axes after every power-up.

Home sensor moved or dirty

Clean and re-set the home sensor.

Coupling slipped between motor and axis

Tighten the coupling and re-reference the axis.

Prevention: Encoder battery changes on a schedule.

Communication fault with the controller

Hits OEE: Availability

Symptoms: Drives drop off the network and axes stop with a communication fault.

Damaged network cable or connector

Replace damaged cables and connectors.

Shield and grounding faults

Ground shields as the network installation guide shows.

Wrong or duplicate address after a drive swap

Check the drive address after replacing a drive.

Firmware or parameters do not match after a swap

Load the matching firmware and parameter set.

Prevention: A backup of every drive's parameters kept with the machine documents.

Guidance only. Always follow lockout/tagout and your site's safe-work procedures, and verify against OEM manuals before acting.

Alarm codes: Omron servo error codes · SANYO DENKI alarm codes · Delta ASDA alarm codes · ACOPOS error codes · Schneider Lexium 32 error codes · Rexroth IndraDrive error codes · Kollmorgen AKD fault codes · Yaskawa SERVOPACK alarm codes · Allen-Bradley Kinetix fault codes · Mitsubishi MELSERVO alarm codes · FANUC servo amplifier alarm codes

Related equipment guides: electric motor · PLC controls · VFD drive · servo motor · encoder · tube bender · turret punch press · UPS system · stepper motor · linear actuator · HMI panel

Stop the same fault coming back

Recurring servo drive stops usually trace to a cause you cannot see by hand. The partner we recommend is Fabrico: it tracks OEE and downtime live from PLCs, IoT sensors or AI cameras; where cameras are fitted, the video of a stop sits next to its machine data so the cause can be reviewed; and a technician opens the work order from the stop in the same system. Data is hosted in the AWS EU region, and Fabrico and the company behind it hold ISO/IEC 27001, ISO/IEC 20000-1 and ISO 9001.

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Methods that cut recurring stops: the six big losses · root cause analysis · preventive vs predictive maintenance · TPM · SMED & changeover