Troubleshooting Error E-1124 (Axis Position Fault) on STP113-009 Stepper Motor

Related Products

Tools Required

• Safety glasses
• Lockout/Tagout kit
• Multimeter
• Hex key set (metric)
• Torque wrench (5-20 Nm range)
• Screwdriver set

Article

Overview

This article provides troubleshooting procedures for Error E-1124 (Axis Position Fault) related to the NXB-SRV-STP113-009 Stepper Motor. This error indicates that the robot controller has detected a discrepancy between the expected and actual position of a motor, or that the motor is unable to complete a commanded move. This fault typically occurs on the minor axes (J4, J5, J6) of NexBot C-5, C-10, and S-3 series robots where the STP113-009 is commonly used.

Following these steps will help you systematically identify the root cause, which could be mechanical, electrical, or a component failure, and restore the system to operational status.

Symptom

The primary symptom is the immediate cessation of robot operations, accompanied by the following indicators:

• Error Message: The teach pendant or control software displays "Error E-1124: Axis Position Fault" along with the identifier for the specific axis (e.g., J4, J5, J6).
• Motion Halt: All robot movement stops, and the brakes on all axes may engage.
• Unresponsive Axis: The faulted axis will not respond to manual jogging commands.
• Audible Noise (Optional): In some cases, the motor may emit a humming or grinding sound just before or during the fault, indicating high load or stalling.

Potential Causes

An E-1124 fault can be triggered by several conditions:

1. Mechanical Binding: An obstruction, excessive friction, or damage to the driven linkage prevents the motor from rotating freely.
2. Electrical Connectivity Issues: A loose or damaged power/control cable to the NXB-SRV-STP113-009 motor can cause intermittent signal loss and step count errors.
3. Motor Overload: The operational load exceeds the motor's 1.9 Nm holding torque capacity. This can be caused by an oversized payload, excessive acceleration/deceleration parameters, or a collision.
4. Incorrect Drive Parameters: The motor driver configuration (e.g., current limit, microstepping) in the robot controller does not match the requirements for the STP113-009.
5. Component Failure: The stepper motor itself or its associated driver has failed internally.

Resolution Steps

WARNING: Always follow proper safety procedures, including powering down the robot and applying lockout/tagout (LOTO) measures before performing any physical inspection or maintenance.

1. Identify the Faulted Axis and Review Logs

• Note the specific axis (J4, J5, or J6) identified in the error message on the teach pendant.
• Access the robot controller's event log to find any preceding warnings or related errors that might provide additional context.

2. Perform a Mechanical Inspection (Power Off)

• With the robot powered down and locked out, carefully attempt to move the affected joint by hand (if brakes are released via a manual release mechanism).
• The motion should be smooth. Feel for any points of resistance, grinding, or catching.
• Visually inspect the axis linkage for foreign debris, signs of collision damage, or improperly seated components.

3. Verify Electrical Connections

• Inspect the motor cable connector at the NXB-SRV-STP113-009 motor body. Ensure it is securely seated and the locking mechanism is engaged.
• Trace the cable back to the robot controller or junction box. Inspect its full length for signs of pinching, abrasion, or sharp bends.
• Disconnect the cable at both the motor and controller ends (with power OFF) and inspect the pins for damage, corrosion, or contamination.
• Using a multimeter, perform a continuity check on each wire in the cable to rule out an internal break.

4. Check for Motor Overload

• Verify that the robot's end-of-arm-tooling (EOAT) and payload are within the robot's specified weight and center of gravity limits.
• Review the motion program for excessive acceleration or deceleration values that could cause the motor to stall. Reduce these values by 10-15% and test the program again.

5. Review Drive Parameters

• In the robot controller's configuration software, navigate to the axis drive parameters for the faulted motor.
• Confirm that the settings match the specifications for the NXB-SRV-STP113-009. Key parameters include the rated voltage (24VDC) and current settings. An incorrect current setting can lead to insufficient torque (too low) or overheating (too high).

6. Isolate the Faulty Component

• If the issue persists and another identical axis is available, you can swap components to isolate the failure. This is an advanced step.
• Motor Swap: Swap the suspect STP113-009 motor with a known-good motor from another axis. If the E-1124 error follows the motor to the new location, the motor has failed and must be replaced.
• Driver Swap: Swap the motor driver in the control cabinet. If the error moves with the driver, the driver is the point of failure.

7. Replace the NXB-SRV-STP113-009 Motor

• If the motor is confirmed to be faulty, order a replacement NXB-SRV-STP113-009.
• Follow the detailed replacement procedure in your specific robot's service manual.
• Ensure the four mounting bolts are tightened evenly in a star pattern to the specified torque (typically 5.0 Nm for M5 bolts, but confirm in your manual).
• After replacement, perform an axis calibration or mastering procedure as required by the robot controller.

Prevention

• Adhere to the robot's scheduled preventative maintenance plan, including lubrication and inspection of mechanical joints.
• Ensure robot programs use smooth motion profiles and avoid exceeding payload specifications.
• Periodically inspect motor cables for wear, especially near moving joints, and ensure proper strain relief is in place.
• Keep the robot's work environment clean to prevent debris from causing mechanical obstructions.

Keywords