Axis 4 Overheating Fault and Position Errors on NexBot Vision MA012-011

Description

We are experiencing a recurring issue with our NexBot Vision MA012-011 robot, SKU NXB-ROB-MA012-011. During our primary machine tending cycle, the robot will intermittently stop and throw an over-temperature fault for the Axis 4 motor. The cycle involves rotating a 22kg machined part 180 degrees. The fault, E-3104, appears on the teach pendant after about 45 minutes of continuous operation. The housing for the Axis 4 motor is extremely hot to the touch, significantly more so than other axes. We have verified that the ambient temperature is within the specified operating range and that there are no obstructions around the arm. After a cooldown period of 20-30 minutes, we can restart the cycle, but the problem always returns. This production stoppage is becoming critical for our line.

Symptoms

• Robot halts operation mid-cycle
• Teach pendant displays 'E-3104: Axis 4 Motor Over-Temperature'
• Axis 4 motor housing is hot to the touch
• Fault occurs under high-duty cycle with near-max payload

Resolution

Remote diagnostics and log analysis indicated a failing brake coil within the Axis 4 servo motor. The coil was not fully disengaging, causing excessive drag and leading to the thermal overload condition. The intermittent nature was consistent with the coil's performance degrading as it heated up. The resolution was to replace the entire Axis 4 motor and gearbox assembly to ensure long-term reliability. The new assembly was installed, the robot was re-mastered, and the motion parameters were verified. The robot has since completed multiple 8-hour shifts without recurrence of the fault.

Resolution Steps

1. Perform a full LOTO (Lock-Out/Tag-Out) on the robot controller and main power disconnect.
2. Mechanically brace the robot arm to prevent uncontrolled movement once the faulty motor brake is removed.
3. Disconnect the power and encoder cables from the Axis 4 motor.
4. Carefully unbolt and remove the existing Axis 4 motor and gearbox assembly.
5. Install the replacement Axis 4 servo motor assembly, part number NXB-MOT-A4-R20.
6. Reconnect and secure the power and encoder cables.
7. Remove the LOTO and power up the system.
8. Perform the Axis 4 mastering procedure followed by a full six-axis mastering check.
9. Run the production program in a continuous test loop for two hours to validate the repair and monitor motor temperatures.