Troubleshooting Error E-8014: J4 Axis Position Tracking Fault on NXB-ROB-LA013-005

Related Products

Tools Required

• Lockout/Tagout (LOTO) kit
• Multimeter
• Hex key set
• Torque wrench
• NexBot controller interface software

Article

Overview

This article provides troubleshooting procedures for the error code E-8014: J4 Axis Position Tracking Fault on the NexBot Robotics LA013-005 6-Axis Robot Arm (SKU: NXB-ROB-LA013-005). This error indicates that the robot's controller has detected a significant discrepancy between the commanded position and the actual reported position of the J4 axis (wrist twist). This fault will cause the robot to stop its current program and enter a fault state to prevent equipment damage or personal injury.

Symptom

When an E-8014 fault occurs, operators will typically observe the following:

• The robot comes to an immediate, controlled stop.
• The teach pendant or HMI displays the alarm: "E-8014: J4 Axis Position Tracking Fault".
• The robot becomes unresponsive to jog commands for the J4 axis, and possibly all axes, until the fault is cleared.
• In some cases, an unusual noise (grinding, whining) may be heard from the J4 axis motor just before the fault is triggered.

Cause

The E-8014 fault can be triggered by several underlying issues, ranging from mechanical problems to electrical failures. The most common causes include:

1. Mechanical Binding: An external obstruction, debris in the joint, or internal gear train failure is preventing the J4 axis from moving freely.
2. Excessive Load: The robot is attempting to move a payload that exceeds the 120 kg limit or has a center of gravity that creates an excessive moment on the wrist, causing the motor to lag.
3. Encoder Malfunction: The J4 axis absolute encoder (related part: NXB-SNS-ABS141-008) is failing. This can be due to a damaged encoder disk, communication failure, or a loose connection, resulting in incorrect position feedback to the controller.
4. Servo Drive Fault: The servo drive module responsible for powering and controlling the J4 axis motor (e.g., NXB-SRV-MD132-009) is malfunctioning.
5. Cabling Issues: The motor power cable or the encoder feedback cable for the J4 axis is damaged, disconnected, or has intermittent connection issues. This is common in applications with extensive wrist articulation.
6. Lost Mastering/Calibration: The robot has lost its calibration data for the J4 axis, causing the controller to calculate position incorrectly.

Resolution Steps

WARNING: All troubleshooting steps must be performed by qualified personnel. Follow all site-specific Lockout/Tagout (LOTO) procedures before performing any physical inspection or maintenance. The NXB-ROB-LA013-005 operates on high voltage (400-480VAC).

Step 1: Initial Assessment and Power Cycle

1. Record any secondary fault codes displayed on the controller.
2. Note the robot's position and the task it was performing when the fault occurred.
3. Perform a controlled shutdown of the robot controller.
4. Wait 60 seconds, then power the controller back on.
5. Attempt to clear the fault from the teach pendant. If the fault clears and does not immediately return, carefully jog the J4 axis at a very low speed (5%) to see if the fault reoccurs. If it does, proceed to the next steps.

Step 2: Inspect for Mechanical Obstructions

1. Apply LOTO procedures to de-energize the robot.
2. Thoroughly inspect the J4 axis and the attached end-of-arm tooling (EOAT). Look for any signs of collision, foreign objects, or debris that could restrict movement.
3. If your system has a manual brake release for the J4 axis, release the brake. Carefully and slowly attempt to move the axis by hand. It should move smoothly with some resistance from the gearbox. Any grinding, clicking, or binding indicates a severe mechanical issue that requires service from a certified technician.

Step 3: Inspect Cables and Connections

1. Ensure the robot is de-energized (LOTO).
2. Inspect the entire length of the robot's wiring harness, paying close attention to the cables that articulate with the J4, J5, and J6 axes.
3. Look for signs of chafing, pinching, cuts, or abrasion.
4. Check that the motor power and encoder cable connectors at the base of the robot and at the J4 motor are securely fastened.

Step 4: Diagnose Encoder and Servo Drive

1. Power on the robot controller (LOTO can be removed for powered diagnostics by qualified personnel).
2. Navigate to the controller's diagnostic or I/O status screen.
3. Monitor the live position data for the J4 axis. If the position value is erratic, frozen, or shows , it strongly suggests a problem with the encoder (NXB-SNS-ABS141-008) or its connection.
4. Check the status of the servo amplifier or drive module for the J4 axis (e.g., NXB-SRV-MD132-009). Look for any specific alarm LEDs or status codes on the drive itself, which may indicate an overcurrent, overvoltage, or internal fault.

Step 5: Re-Master the Axis

If no physical faults are found and the encoder appears to be communicating but the fault persists, the mastering data may be corrupt.

1. Follow the detailed procedure in the NXB-ROB-LA013-005 Maintenance Manual for re-mastering (re-calibrating the zero position) of the J4 axis.
2. This procedure requires specific fixtures and software access and should only be performed by a trained technician.

Step 6: Component Replacement

If diagnostics confirm a component failure, replace the faulty part.

• Encoder: If the encoder is deemed faulty, replace it with part number NXB-SNS-ABS141-008. Re-mastering will be required after replacement.
• Servo Drive: If the drive is faulty, replace it with part number NXB-SRV-MD132-009. Ensure all drive parameters are correctly configured from a backup before returning the robot to service.

Prevention

• Regular Inspections: Periodically inspect the robot's cabling for wear and tear, especially around the wrist axes.
• Proper Programming: Ensure robot programs use smooth motion paths and avoid unnecessarily high acceleration/deceleration on the J4 axis.
• Load Verification: Verify that the weight and center of gravity of all end-of-arm tooling and parts are within the robot's 120 kg payload and moment specifications.
• Scheduled Maintenance: Adhere to the maintenance schedule outlined in the robot's service manual, which includes gearbox lubrication and mechanical inspections.

Keywords