LA013-009 Axis 4 (J4) Overheating and Position Deviation Fault

Description

Our NexBot Robotics LA013-009 robot, which is used for a palletizing application, has started to intermittently fault out mid-cycle. The teach pendant displays error E-3104, related to axis position deviation. Our maintenance team has observed that the motor housing for Axis 4 is extremely hot to the touch, significantly hotter than the other axis motors. We can also hear a high-pitched whining sound from the J4 assembly just before the fault occurs. The robot is operating well within its 120 kg payload limit, handling boxes that weigh approximately 85 kg. We have checked the PROFINET connection and it appears stable. The issue is causing significant downtime on our primary packaging line. We have tried power cycling the controller, but the fault returns within 20-30 minutes of restarting the production cycle. We need urgent assistance to diagnose and resolve this.

Symptoms

• Axis 4 (J4) motor running at abnormally high temperature.
• Robot halts mid-cycle with a position tracking error.
• Audible whining noise from the J4 gearbox assembly before faulting.
• Error E-3104 (Axis Position Deviation) displayed on the teach pendant.

Resolution

After remote diagnostics and an on-site evaluation, the issue was traced to a premature failure of the harmonic drive and brake assembly within the Axis 4 motor unit. The excessive heat was generated by increased friction from worn internal components, leading to the brake slipping and causing the position deviation fault under load. The resolution was to replace the entire J4 motor and gearbox assembly. The replacement part corrected the temperature, noise, and faulting issues. The robot's mastering was updated and it has since passed all operational tests under full load.

Resolution Steps

1. Follow standard LOTO (Lockout/Tagout) procedures to safely de-energize the robot controller.
2. Manually release the brake for Axis 4 and carefully move the arm to a secure, supported position for maintenance.
3. Disconnect the main power and encoder feedback cables from the J4 motor assembly.
4. Unfasten the mounting bolts securing the J4 motor and gearbox unit to the robot arm structure.
5. Carefully remove the faulty J4 motor assembly.
6. Install the new J4 Motor/Gearbox Assembly (SKU: NXB-MTR-J4-R20-A) and torque bolts to manufacturer specifications.
7. Reconnect the power and encoder cables to the new motor.
8. Power on the system, perform the axis mastering procedure for J4, and clear all system faults.
9. Run the robot through several slow-speed cycles, then gradually increase to full production speed while monitoring J4 motor temperature and performance.