Industrial robot maintenance is about more than preventing unplanned downtime. It’s also about ensuring products meet quality standards, that workers stay safe and that the business maximizes its ROI from the machine.
Articulated robots, along with the growing use of collaborative robots (cobots), are essential to modern manufacturing operations. They do repetitive, messy and hazardous jobs such as welding, painting, material handling, machine tending and assembly. Without robots, productivity and quality would be lower and costs would be higher.
If regular maintenance is skipped or not done well, performance issues will emerge, or the robot may stop working completely. Performance problems include reduced repeatability, increasingly erratic movements and grippers failing to grasp correctly. When any of these happen, operators may, with the best of intentions, bypass safety systems in an effort to restore production without stopping an entire cell or line.
As they are complex machines, robot maintenance differs significantly from that of other equipment and requires specialized skills. Many manufacturers handle this by contracting with a specialist.
Defining industrial robot maintenance
“Robot” and “robotics” are broad terms used for any system that can operate autonomously. In manufacturing, “industrial robotics” refers to machines that move through free space, following a path that’s usually pre-programmed. A newer trend is for some robots, particularly mobile ones, to autonomously navigate through complex environments.
Most industrial robots use a five- or six-axis articulated arm configuration, although gantry (cartesian) and SCARA (selective compliance articulated robot arm) robots are also quite common. Packaging increasingly sees high-speed “delta” configuration robots mounted over conveyors while growing numbers of cobots are used around human workers.
In warehousing, autonomous mobile robots (AMRs) are being used to deliver and retrieve packages and totes. These are an evolution of the autonomous guided vehicles (AGVs) some manufacturers have long used for material delivery.
Maintenance for robots stands apart from other types of industrial maintenance due to the intricate nature of the equipment, the reliance on precise positional data and the potential consequences of any malfunctions.
This means a robot preventive maintenance program goes beyond common routine maintenance tasks like inspection and lubrication. In addition to verifying robot cell safety, regular maintenance should address sensor operation and calibration, monitoring of motion and control system checks, software integrity testing, and program management.
Key components and common maintenance tasks
The modern robotic arm is a complex electromechanical assembly incorporating servomotors, gears and encoders. These provide position feedback to the controller, which calculates the movements of each motor. Most companies program offline but use a pendant at the robot for program modifications.
To complete the robotic system, various sensors detect part presence, and an end effector or end-of-arm-tooling (EOAT) grasps the part or tool as needed. Interlocks ensure the cell stays properly guarded, and proximity sensors detect workers inside the work envelope.
A robot maintenance schedule usually involves frequent sensor cleaning and inspections of components that can wear quickly or become damaged. These are primarily the cables and/or hoses taking power to the EOAT and returning signals to the controller. Cables move with the arm and often fret against rigid cell components. To reduce the frequency of faults, they should be engineered for high-flex usage.
Other important aspects of robot preventive maintenance are:
- Cleaning and testing the EOAT, with repairs performed as necessary
- Cleaning, inspecting and replacing the teach pendant if necessary
- Cleaning all joints to prevent the infiltration of dirt and liquids past the seals
- Lubricating at the frequency recommended by the manufacturer
- Monitoring for motion faults like vibration, noise or inconsistent positioning
- Replacement of batteries that provide memory backup
- Replacement of control cabinet air filters
- Full tests of all cell safety systems
- Harmonic drive wear checks
- Backlash measurement
- Brake inspection
- Thermal imaging checks
- Software backup procedures
- Periodic controller firmware updates
Robot manufacturers provide detailed maintenance schedule recommendations to avoid unplanned machine downtime. These must be modified to account for service environment and intensity of usage.
Preventive vs. predictive vs. prescriptive robot maintenance
There are three main types of maintenance strategies that can be applied to keeping robotics systems in good working order. These are:
- Preventive maintenance, which is based on performing regularly scheduled tasks as recommended by the manufacturer
- Predictive maintenance, which uses information from condition monitoring sensors to schedule work to prevent failures before they occur
- Prescriptive maintenance, which is driven by recommendations made by advanced AI algorithms and data analysis
Each of these brings its own unique set of advantages and specific use cases. Robots can generate a wealth of operational data that makes them ideal for AI-based maintenance analysis, for example. Sensor data also enables real-time performance analysis that supports predictive maintenance efforts, which can lead to a leaner spare parts stockroom because teams will be able to predict with greater certainty when specific industrial automation components will be needed.
AGVs and special considerations
Unlike industrial robots, AGVs roam throughout the factory and/or warehouse. This creates some additional maintenance requirements. In particular:
- Inspect the condition of tires or tracks and ensure proper wheel alignment, as deterioration could cause slippage and navigation issues.
- Check the health of the power or traction battery to prevent the vehicle from becoming stranded.
- Ensure sensors are clean and functioning correctly.
- Perform software updates, especially those used for mapping, to avoid collisions or inefficiency.
- Perform any required calibrations.
- LIDAR sensor maintenance.
- Battery cycle life monitoring.
- Charging station inspection.
- Network connectivity reliability.
- Fleet management software health.
Challenges and warning signs of impending robot issues
These machines seldom stop working without warning—there are usually indications that robot repair will soon be needed. For example, robot technicians and others working around the robot should look out for:
- Motors and joints becoming abnormally hot
- Unusual arm noises
- Vibration (often most apparent in the EOAT)
- Drifting from programmed paths and having trouble grasping parts properly
- Servo following errors
- Encoder drift
- Increased power consumption
- Communication timeouts
An alternative to relying on observation is to implement appropriate predictive maintenance sensors. An analytics package could use signals from temperature and vibration sensors to predict when failure is likely, allowing timely dispatch of a robotics repair technician.
Given the high costs of and disruption caused by a robot breakdown, which could include missed shipments in JIT environments, predictive maintenance technology is often a very astute investment.
Get expert help with industrial robot maintenance
Faults with robots and robot cells can lead to quality problems, scrap and waste material. They can also pose safety risks as operators attempt to rectify problems on the fly. If the faults result in complete robot failure, the consequences will quickly ripple through the plant, with downstream machines and even entire lines being stopped.
The solution lies in prioritizing robust robot maintenance programs that detect and prevent problems before they interfere with production. Well-maintained industrial robots and AGVs lead to better throughput, fewer disruptions and a stronger bottom line.
ATS offers manufacturers industrial maintenance services that range from help with temporary spikes in workload to support for articulated robots and assistance with implementing predictive maintenance. Contact us to learn more.
