Intermittent Overcurrent Fault on Axis 2 of R-50 Robot with MD132-015 Drive

Description

We are experiencing an intermittent fault with one of our R-50 series robots on the main assembly line. The robot will stop mid-cycle and the teach pendant displays an axis drive fault. The issue seems to be isolated to Axis 2. We have checked the mechanical components for any binding or obstructions and found none. The robot can be homed and jogged without issue, but the fault appears randomly during high-speed production cycles, typically during sharp acceleration or deceleration. The drive in question is the NexBot Vision MD132-015 Multi-Axis Servo Drive (SKU: NXB-SRV-MD132-015). We've tried power cycling the entire cell, which clears the fault temporarily, but it always returns within a few hours of operation, causing significant downtime. We suspect a potential issue with the servo drive itself, as the motor and cabling appear to be in good condition. We need assistance diagnosing whether this is a configuration issue or a hardware failure.

Symptoms

• Robot stops unexpectedly during operation.
• Teach pendant displays error code E-4210 (Drive Overcurrent Fault).
• The status LED on the MD132-015 drive flashes red.
• Fault is specific to Axis 2 and occurs under heavy load.

Resolution

After guiding the customer through diagnostic steps, the issue was isolated to the NexBot Vision MD132-015 drive. The technician on-site was instructed to swap the motor and encoder cable connections for Axis 1 and Axis 2 at the drive terminals. Upon running the machine, the E-4210 fault migrated from Axis 2 to Axis 1. This test confirmed that the motor, gearbox, and cabling for the original Axis 2 were functioning correctly, and that the fault was originating from the Axis 2 output channel within the servo drive unit. The root cause was determined to be a failing power stage component for one of the axes inside the drive. The customer was advised to replace the faulty drive. A replacement NXB-SRV-MD132-015 was dispatched and installed, which fully resolved the production stoppage.

Resolution Steps

1. Perform a full LOTO (Lockout/Tagout) on the robot cell's main power disconnect.
2. Open the control cabinet and locate the NXB-SRV-MD132-015 servo drive.
3. Carefully label and disconnect the motor power and encoder feedback cables for Axis 1 (X1) and Axis 2 (X2) from the drive.
4. Swap the connections: Connect the Axis 1 cables to the X2 terminals on the drive, and the Axis 2 cables to the X1 terminals.
5. Remove LOTO and power on the system. Manually jog the axes at low speed to confirm the control swap.
6. Run the production program and observe the system. The E-4210 fault now appeared on Axis 1, confirming the drive was the source of the fault.
7. Power down the system via LOTO and replace the faulty NXB-SRV-MD132-015 unit with a new one.
8. Restore the original wiring configuration, power up the system, load the configuration parameters, and verify that the issue is resolved.