Troubleshooting Error E-1601: Protective Stop - Excessive Force Detected on FLR022-004 Robot Arm

Related Products

Tools Required

• Teach Pendant
• Laptop with NexBot Control Suite
• Allen Wrench Set
• Digital Multimeter

Article

This article provides troubleshooting steps for the error code E-1601 (Protective Stop - Excessive Force Detected) on the NexBot Robotics FLR022-004 Collaborative Robot Arm. This error indicates that one of the robot's six joints has detected a force or torque exceeding its pre-configured safety limits, causing the robot to execute a protective stop to prevent injury or damage. This is a core safety feature of the power and force limiting technology integrated into the C-5 series robots.

Symptom

When error E-1601 occurs, you will typically observe the following:

• The robot arm immediately halts all motion.
• The teach pendant or HMI displays the message: "E-1601: Protective Stop - Excessive Force Detected". The message may also indicate which joint (J1-J6) triggered the event.
• A red or amber status indicator light on the robot controller is illuminated.
• The robot's brakes are automatically engaged, making the arm rigid and difficult to move manually until the fault is cleared.

Cause

The E-1601 error is triggered by the robot's internal sensors detecting an unexpected force. The most common causes include:

1. Unintended Collision: The robot arm has physically collided with an object in its workspace, such as a fixture, a misplaced part, or personnel. This is the most frequent cause.
2. Incorrect Payload Settings: The defined payload mass or center of gravity in the control software does not accurately reflect the end-of-arm tooling (EOAT) attached. This causes the robot to calculate incorrect joint torques, potentially exceeding safety limits even during normal motion.
3. Aggressive Motion Programming: The programmed acceleration, deceleration, or cornering values are too high for the configured payload, leading to inertial forces that surpass the protective stop thresholds.
4. Singularity Point: The robot's path takes it too close to a wrist or shoulder singularity, causing one or more joints to attempt excessively high-speed movements, which can be interpreted as a high-force event.
5. Environmental Factors: Excessive vibration transmitted through the robot's mounting surface can be misinterpreted by the joint sensors as an external force.
6. Hardware Issue: In rare cases, a faulty internal joint sensor or a damaged communication cable (e.g., EtherCAT cable) can transmit erroneous data, falsely triggering the error.

Resolution Steps

WARNING: Always prioritize safety. Ensure the robotic cell is in a safe state before approaching the hardware. Follow all local lockout/tagout (LOTO) procedures if hardware inspection is required.

Step 1: Assess the Situation and Ensure Safety

Before attempting to clear the error, visually inspect the entire workspace. Identify any obvious obstructions or collision points. Ensure no personnel are within the robot's reach.

Step 2: Identify the Point of Failure

Review the error log on the teach pendant. Note which joint triggered the stop and the timestamp. Correlate this information with the robot's program to identify the exact motion or program line where the fault occurred. This context is critical for diagnosis.

Step 3: Clear the Fault

1. If a physical obstruction caused the stop, carefully remove it.
2. On the teach pendant, navigate to the alarm screen and press the 'Clear Fault' or 'Reset' button.
3. You may need to re-enable motor power by pressing the corresponding button on the teach pendant. The status light on the controller should return to green.
4. If possible, use the manual jog function at a low speed to move the robot away from the fault position.

Step 4: Verify Payload and Tool Center Point (TCP) Settings

Incorrect payload data is a common hidden cause of E-1601 errors.

1. Navigate to the 'Tool & Payload' configuration menu in the control software.
2. Confirm that the selected payload accurately matches the currently installed EOAT. The NXB-ROB-FLR022-004 has a maximum payload of 10 kg.
3. Verify that the mass (kg) and the Center of Gravity (X, Y, Z coordinates relative to the tool flange) are entered correctly. If unsure, re-run the payload identification wizard.

Step 5: Review and Optimize the Robot Program

If no collision or payload mismatch is found, review the robot's motion profile.

• Reduce Acceleration/Deceleration: Locate the motion command that triggered the error. Reduce the acceleration and deceleration percentages for that move (e.g., from 80% to 50%) and test the program again.
• Smooth Corners: For sharp directional changes, replace MoveL commands with MoveJ where possible, or add a blend radius (cornering) to smooth the transition between linear movements. This reduces inertial spikes at corners.
• Check for Singularities: Analyze the robot's path to ensure it does not pass near a singularity point. Adjust the waypoint or change the robot's configuration to avoid these positions.

Step 6: Inspect Hardware and Environment

If the error persists without a clear cause, perform a hardware check.

1. Execute a proper shutdown and LOTO procedure for the robot controller.
2. Check that the robot base is securely fastened to its mounting surface (e.g., stand NXB-MNT-813-003). Loose bolts can cause vibration.
3. Inspect the main robot communication cable (e.g., EtherCAT cable NXB-CBL-512-004) for any signs of physical damage, pinching, or abrasion. Ensure connectors at the robot base and controller are fully seated.
4. If the problem consistently occurs on the same joint, contact NexBot Robotics Technical Support to perform advanced diagnostics on the joint's internal sensors.

Prevention

• Thorough Path Simulation: Use offline programming and simulation software to validate all robot paths for potential collisions before deploying them on the physical NXB-ROB-FLR022-004 arm.
• Accurate Payload Data: Implement a strict procedure to update the robot's payload settings every time the end-of-arm tooling is changed.
• Conservative Programming: Start with conservative motion parameters (lower speeds and accelerations) and gradually increase them as the program is validated.
• Routine Maintenance: Periodically inspect the robot's mounting hardware and cabling for any signs of wear, damage, or loose connections as part of a scheduled maintenance plan.

Keywords