MA012-001 Robot Arm Faults with J2 Axis Overcurrent Error During High-Reach Motion

Description

Our NexBot Robotics MA012-001 robot arm, SKU NXB-ROB-MA012-001, has started to intermittently fault during a new machine tending cycle. The fault occurs when the arm is nearly at its full 1710 mm extension, moving a 22kg part. The controller screen displays error code E-4502 and the robot stops immediately, requiring a full reset to clear. This seems to happen specifically when Joint 2 (J2) is commanding a high-torque move to lift the part out of the machine. We have verified the payload data in the controller is correctly set to 22kg with the proper center of gravity. We have also inspected the power cables to the J2 servo motor and see no visible damage or loose connections. The incoming 3-phase voltage is stable at 400VAC. The issue is causing significant production downtime as it happens several times per hour.

Symptoms

• Robot stops mid-cycle and requires a manual reset.
• Controller displays 'E-4502: J2 Axis Servo Drive Overcurrent Fault'.
• The fault occurs specifically during high-extension, high-acceleration movements.
• Audible click as the J2 motor brake engages upon fault.

Resolution

The root cause was identified as an improperly tuned acceleration parameter for the J2 axis in relation to the new motion profile. While the payload data was correct, the program's acceleration/deceleration values for the extended reach move were causing a current spike that exceeded the servo drive's configured software limit, triggering the E-4502 protective fault. The issue was not a hardware failure but a tuning mismatch. By increasing the drive's peak current tolerance parameter and slightly smoothing the motion profile in the robot program, the current demand was brought back within acceptable limits, resolving the fault.

Resolution Steps

1. 1. Connect to the robot controller with the NexBot Service Suite software.
2. 2. Navigate to the 'Servo Drive Parameters' menu and select the Axis 2 drive.
3. 3. Locate parameter '4-12: Peak Current Limit' and increase the value from 150% to 175%.
4. 4. In the robot program, locate the motion instruction for the problematic move.
5. 5. Change the motion termination type from 'Fine' to a 'CNT10' (continuous) type to smooth the acceleration into the next point.
6. 6. Save the updated parameters and the robot program.
7. 7. Perform a cold restart of the robot controller to ensure all parameter changes are applied.
8. 8. Run the machine tending cycle continuously for one hour to validate that the E-4502 fault does not reoccur.