Checklist: Verifying Cobot Safety Before Commissioning

Bringing a collaborative robot into a production environment requires more than just connecting power and control systems. A safe cobot deployment depends on a series of specific mechanical, electrical, and logical checks that verify the system behaves exactly as designed. Skipping these steps leads to unexpected stops, false alarms, or worse, safety incidents. The checks below follow a logical sequence, moving from physical hardware to software configuration and finally to operational testing. Treat this as a mandatory pre-production phase. Do not allow untrained personnel to operate the cell until every item is signed off.

Mechanical and Structural Verification

The first layer of protection is the physical cell. Before any software is loaded, the cobot and its fixtures must be mechanically secure. This prevents structural failure from causing a hazard.

1. Verify mounting torque. Check the mounting flange and bolts. Use a calibrated torque wrench to confirm fasteners meet the manufacturer specifications. A loose flange can vibrate and damage the controller over time.
2. Inspect cable management. Ensure the robot cable is not pinched, stretched, or rubbing against sharp edges. The cable should have enough slack to allow the full range of motion without tension.
3. Check fixture stability. Any end effectors or tooling attached to the cobot must be rigidly fixed. A loose gripper or suction cup can drop a part, creating a crush or cut hazard.
4. Confirm guard boundaries. If the cell uses physical barriers, verify they are anchored. If it relies on safety fencing, check that the gates have interlocks and that the fence height prevents a person from reaching the robot.

Red flag: If the cobot sways or vibrates at low speeds, the mounting or the payload balance is likely incorrect. Stop and re-check the base bolts and the center of gravity of the attached tool.

Electrical and Control System Checks

The electrical architecture determines how quickly the robot reacts to danger. A delay in stopping can turn a minor contact into a serious injury.

Component	Check Requirement	Typical Failure Mode
Emergency Stop (E-Stop)	Hardwired circuit, independent of PLC logic	Delayed response or failure to cut power
Light Curtain	Beam alignment, break beam test	False triggers or missed detection
Safety Relay	Proper contact rating, no bypassing	Contact welding or signal loss
Grounding	Continuity test to chassis	Electric shock risk during faults

1. Test emergency stop circuits. Press each E-Stop button. The robot must stop power immediately. Do not rely on the controller’s software stop. The physical circuit must drop voltage.
2. Verify interlock wiring. If the cell uses safety fencing or light curtains, check the wiring. Open the gate or break the beam. The robot must stop within the defined reaction time.
3. Check grounding continuity. Measure the resistance between the robot chassis and the ground terminal. It should be very low. Poor grounding can cause static discharge or make the chassis live during a fault.
4. Inspect controller wiring. Look for loose terminal blocks or damaged insulation. Heat and vibration loosen connections over time.

Red flag: If the E-Stop button requires two presses to reset, or if the reset requires a specific sequence that confuses operators, the wiring or the controller settings are incorrect. Keep the reset simple.

Software Configuration and Safety Zones

Software settings define the “soft” limits of the cobot. These must be configured to match the physical reality of the cell.

1. Define the work zone. Set the x, y, and z limits in the controller. These should be slightly larger than the actual workpiece dimensions to account for tolerance.
2. Configure velocity and acceleration. Set the maximum speed for the robot. Lower speeds reduce the kinetic energy available during a collision. For human-adjacent tasks, use the lowest speed that still meets production targets.
3. Set force limits. This is the core of a safe cobot strategy. Configure the power and force limiting parameters. The robot should stop when it detects a force exceeding the threshold.
4. Enable collision detection. Ensure the controller’s collision detection algorithm is active. Test it by applying a known force to the arm. The robot should stop and log the event.

Red flag: If the force limit is set too high, the robot will feel stiff and may push back against a human operator. If it is set too low, the robot will stop during normal operation, causing false alarms.

Operational Testing and Verification

Once the hardware and software are configured, you must test the system in a controlled environment. This is where you verify that the safe cobot actually behaves as intended.

1. Perform a dry run. Run the program without the end effector. Watch for unexpected movements or collisions with the frame.
2. Test with a dummy load. Attach a weight equivalent to the production part. Run the program. Check for sag, vibration, or unexpected stops.
3. Simulate a collision. Have a trained operator apply a steady force to the arm at the worst-case angle. The robot should stop immediately.
4. Verify the stop behavior. When the robot stops due to a collision, it should not restart automatically. It must require a manual reset or a specific operator action.
5. Check the alarm log. Review the controller logs for any hidden errors or warnings. A clean log indicates a stable configuration.

Red flag: If the robot stops but the alarm is unclear, the operator will not know what happened. Ensure every stop condition generates a specific, readable alarm code.

Documentation and Training

A safe cobot is not just a machine; it is a process. Without documentation, the safety setup degrades as staff change.

1. Write the risk assessment. Document the hazards identified, the controls implemented, and the residual risk. This is a legal requirement in many regions.
2. Create an operator manual. Include a clear explanation of how to start, stop, and reset the robot. Use pictures where possible.
3. Train the operators. Do not assume prior knowledge. Show them what to do if the robot stops unexpectedly. Explain why they must not bypass the safety features.
4. Schedule maintenance checks. Set a recurring task to re-verify torque, sensor alignment, and force limits. Wear and tear change the behavior of the system over time.

Red flag: If the risk assessment is a generic template with no cell-specific details, it is useless. Tailor it to your specific cobot model and workspace.

Final Pre-Commissioning Sign-Off

Before you hand the cell over to production, complete a final walk-through. This is the last chance to catch small issues that could become large problems.

1. Walk the perimeter. Check that no wires are dangling and no tools are left on the floor.
2. Verify all E-Stops are accessible. An operator must be able to reach an E-Stop without moving their body into the robot’s path.
3. Confirm communication with the PLC. If the cobot is part of a larger line, test the handshake signals. Ensure the PLC can send a “start” command and receive a “stop” signal.
4. Get sign-off from the safety officer. A second set of eyes can catch blind spots. Have someone who was not involved in the integration review the checklist.

Red flag: If any item on this checklist is marked “N/A” without a clear reason, investigate why. “N/A” often means “we forgot to check.”

By following this checklist, you create a foundation for a safe cobot that protects people and equipment. It is not a one-time task. Revisit it whenever you change the payload, the workspace, or the robot model. Safety is a continuous process, not a single event.