Modern industrial robots are robust; issues with joints, motors, encoders, and controllers are rare. However, robot cells are intricate assemblies with numerous components that will wear and eventually fail over time. Cables, even the high-flex versions, are an example of where faults can occur. Good robot troubleshooting skills are essential to get to root causes like these quickly and minimize lost output.
Unscheduled stoppages, like those resulting from a robot problem, disrupt production operations and are usually expensive. In many cases the brief interruptions resulting from intermittent faults are some of the worst as they lower OEE and sap the morale of those working with and around the robot system.
Industrial automation troubleshooting is a very specific skill, although not one taught in college classes. It demands a thorough understanding of the machinery, knowledge of the likely failure modes, and a logical and pragmatic approach to diagnosis and problem resolution.
Tips for Robot Troubleshooting
When a problem is reported some initial questions help direct the diagnostic approach:
- Is the system stopped? Intermittent faults are harder to diagnose and often need a period of extended observation. A full stoppage is sometimes easier to resolve but almost always needs a faster response.
- What is the nature of the problem? Is the robot dropping parts, moving to the wrong position or something else?
- Has anything changed? A change in part dimensions, a modification to the end effector or a software update can all cause a robot problem. In cells using vision systems, even a variation in shade or surface texture can be enough to confuse a camera.
Having gained a sense of what might have caused the problem, preliminary things to look for include:
- Fault or alarm codes on the pendant. FANUC provides extensive support for fault-finding and debugging, including fault history and a chart of the most common faults, so start by looking at what the system is telling you.
- Confirm that safety mechanisms haven't been triggered. A common reason for robot to stop is a switch or sensor somewhere in the cell indicating a gate or guard is open.
- Check operation of sensors. Part presence sensors can get dirty, preventing the PLC from signaling the robot to start its cycle.
- For gripping problems, check the condition of the end effector. For example, suction cups can split and not apply the holding force needed. In pneumatic systems check there’s sufficient air.
- Restart the system. Sometimes this is all that’s needed to clear registers and reset flags.
If the system still won’t run or an intermittent fault occurs again, more detailed investigation is needed. This should include:
- Check basic electrical components. Look for blown fuses, bad switches and faulty solenoids. Replace batteries, then check for broken wires (as can occur in high-flex cables) and shorted motors.
- Consider programming errors. For new or updated programs, verify that the commands don't direct the robot arm to unattainable positions.
- Explore noise spikes. Factories are electrically noisy, especially around welders, and this can cause intermittent or seemingly random events or faults.
- Test motors and servo systems. Motors can overheat, encoders can fail and other faults can develop.
Support Is Available From Acieta
While regular preventive maintenance mitigates downtime risks in a robot cell, it doesn't offer full-proof protection. Having a team with proficient robot troubleshooting knowledge is crucial. Furthermore, if internal resources are unable to restore system functionality, having access to a robot expert is invaluable.
Acieta is fully prepared to support every facet of robot system operation. We offer a wide array of services, including preventive maintenance, training, and support during breakdowns. Contact us for further assistance or more information.