Intermittent Motor Power Fault on R-100 Robot After Cable Replacement

Description

We recently replaced a worn motor power cable on our R-100 robot (Joint 4 axis) with a new NexBot Safety PWR511-008 Motor Power Cable. Since the replacement, the robot has been experiencing intermittent halts during its pick-and-place cycle. The controller logs show a recurring E-2103 error, indicating a motor power phase loss. The fault seems to happen randomly, but we've noticed it's more frequent when the arm is performing high-speed extension and retraction movements. We have visually inspected the cable's path and don't see any obvious pinching or damage. The connections at both the controller end and the motor end appear to be seated correctly, but the problem persists. This is causing significant unplanned downtime on our assembly line, and we need to identify the root cause quickly. We suspect either a faulty new cable or an underlying connection issue that we're missing.

Symptoms

• Robot intermittently halts during operation.
• Controller displays E-2103 (Motor Power Phase Loss) error.
• Faults occur most frequently during high-acceleration moves of Joint 4.
• Slight audible buzzing near the Joint 4 motor connector just before a fault.

Resolution

The root cause was determined to be an improperly torqued connector on the NexBot Safety PWR511-008 Motor Power Cable at the Joint 4 motor. Although the connector was hand-tight, it was not secured to the manufacturer's specified torque value of 8 Nm. The intermittent connection caused micro-arcing and phase loss during high-vibration movements, triggering the E-2103 fault. A service technician used a calibrated torque wrench to tighten the connector to the correct specification. Following this corrective action, the system was tested extensively under full production load for several hours with no recurrence of the fault. The case was closed after confirming stable operation with the customer.

Resolution Steps

1. 1. Performed standard lockout/tagout (LOTO) procedure to de-energize the robot controller and cell.
2. 2. Visually inspected the NXB-SRV-PWR511-008 cable run from the robot base to the Joint 4 motor; no external damage was found.
3. 3. Attached a calibrated torque wrench to the connector at the Joint 4 motor housing.
4. 4. Measured the existing torque and found it to be approximately 4 Nm, which is below the required specification.
5. 5. Tightened the connector to the manufacturer-specified torque of 8 Nm.
6. 6. Removed LOTO and powered on the robot system.
7. 7. Cleared the E-2103 fault from the controller log.
8. 8. Executed a diagnostic routine with repeated high-acceleration movements for all axes for 30 minutes, confirming the fault did not reappear.