C-10 Robot Joint 4 Servo Motor (AC111-009) Intermittent EtherCAT Communication Loss

Description

We are experiencing intermittent faults on our C-10 series robot on production line 3. The system is throwing an E-4502 'Drive Communication Fault' error, specifically pointing to the Joint 4 axis. This joint uses the NXB-SRV-AC111-009 Ac Servo Motor. The issue happens randomly, sometimes after hours of normal operation, causing the entire line to stop. We have checked the external EtherCAT cabling between the controller and the motor, and everything appears secure. We've also power-cycled the controller and the robot, which temporarily clears the fault, but it always returns. The motor doesn't seem to be overheating, and there are no unusual vibrations or noises before the fault occurs. This unplanned downtime is becoming critical, and we need assistance in diagnosing whether this is a configuration issue or a hardware failure with the motor itself.

Symptoms

• Intermittent 'Drive Communication Lost' alarm on controller
• Robot C-10 halts mid-cycle
• Joint 4 position drifts slightly before faulting
• Error code E-4502 logged in the system event log

Resolution

Troubleshooting determined the cause to be an internal failure of the EtherCAT communication board within the NXB-SRV-AC111-009 servo motor on Joint 4. Swapping the motor with a known-good spare resolved the communication errors immediately. The original motor exhibited the fault even when tested on a bench with a direct connection, confirming the internal hardware issue. The robot's Joint 4 was re-mastered and the system was tested under a full production load for 24 hours without any recurrence of the E-4502 error.

Resolution Steps

1. Verified the integrity and proper seating of the EtherCAT cables at both the motor and the controller cabinet; no issues found.
2. Monitored the drive status in the diagnostic software and observed intermittent packet loss specifically for the Joint 4 motor.
3. Powered down the robot and followed lockout/tagout procedures.
4. Replaced the suspect Joint 4 motor with a new NXB-SRV-AC111-009 Ac Servo Motor from maintenance stock.
5. Powered on the system and confirmed stable EtherCAT communication with the new motor via the diagnostic panel.
6. Performed a zero position mastering for Joint 4 to calibrate the new motor.
7. Ran the production cycle for 24 hours under observation with no recurrence of error E-4502.
8. Advised customer to process an RMA for the faulty motor and order a replacement spare.