Intermittent Position Tracking Fault on Axis 2 of LA013-010 Robot

Description

We are experiencing an intermittent but increasingly frequent issue with our NexBot Robotics LA013-010 robot arm, SKU NXB-ROB-LA013-010. During our primary palletizing routine, the robot's J2 axis will occasionally overshoot its target position by a few millimeters, triggering a position tracking fault and halting the production line. The error code displayed is E-4115. We have tried re-mastering the robot and reducing the acceleration parameters in the program, but the issue persists. The problem seems more pronounced when the arm is fully extended and carrying a payload near its 120 kg capacity. All PROFINET communication with the PLC remains stable during the fault, and the other five axes perform flawlessly. We suspect a potential mechanical issue, perhaps with the J2 motor brake or the gearbox, as there is a noticeable low-frequency vibration from the base of the arm just before the fault occurs. We need assistance diagnosing whether this is a hardware failure requiring replacement parts.

Symptoms

• Robot overshoots programmed waypoints on J2 axis
• System throws E-4115 (Axis Position Tracking Error)
• Visible vibration in the robot arm during J2 deceleration
• Fault occurs more frequently with heavier payloads

Resolution

Troubleshooting determined that the electromagnetic brake on the J2 axis servo motor was failing to disengage cleanly, causing excessive drag and leading to position tracking errors. The motor was drawing higher than normal current trying to overcome the resistance, especially under heavy load. The issue was not correctable through software or recalibration. The entire J2 axis motor assembly, which includes the motor, encoder, and brake unit, was replaced. After installation of the new assembly (Part: NXB-MOT-S45B-J2) and subsequent axis mastering, the robot passed all diagnostic and production tests without any further positioning faults.

Resolution Steps

1. Confirmed proper 480VAC supply to the controller and robot.
2. Performed a system backup of the current robot configuration and programs.
3. Following LOTO procedures, powered down the robot and controller.
4. Mechanically supported the robot arm with an overhead crane to prevent movement upon brake release.
5. Disconnected motor power and encoder cables from the J2 axis motor and removed the faulty assembly.
6. Installed the new J2 axis motor assembly (Part: NXB-MOT-S45B-J2) and torqued mounting bolts to specification.
7. Reconnected all cables and removed the mechanical arm support.
8. Powered on the system, performed the J2 axis mastering procedure, and loaded the backup.
9. Executed the palletizing program for one hour at full speed and maximum payload to confirm the resolution.