Improving uptime in industrial robotic systems

October 05, 2018 // By Clemens Müller
Machine maintenance can sometimes seem like a black arts. A seemingly reliable machine suddenly stops working and, despite everyone’s best efforts, cannot be brought back to life. Along comes a member of the maintenance team and, after some beard scratching, tinkering inside the machine and a few words of encouragement, the machine springs back to life.

The reality is often more pragmatic. Schedules of work are arranged to optimize uptime and undertake preventative maintenance during periods that have the least impact on manufacturing. However, there are still times when maintenance engineers seemingly ‘sense’ impending failure of their robots and automation equipment. Could the implementation of sensing technologies, beyond the sensors needed for process monitoring, deliver improvements in predictive maintenance?

 

Scheduled downtime to improve uptime

It is unlikely that we will see factories with row upon row of unskilled worker undertaking the menial manufacturing tasks that were common at the turn of the 20th century. Today’s factories are highly automated with barely the need for a human hand to touch the product during the manufacturing process. The maintenance teams play a key role in keeping the machines alive, as unplanned downtime can quickly eat into slim profit margins.

At the heart of any manufacturing operation is a maintenance, repair and operation (MRO) plan. Through careful scheduling, preventative maintenance (PM) is arranged so that it has minimal impact on the manufacturing flow. The PM plan, when implemented well, can extend the life of the machines and robots being used. A robot’s life can extend to 20 years if regularly maintained, providing the organization with an excellent return on investment (RoI).

Robot manufacturers, such as Yaskawa, Fanuc and Kuka, supply detailed PM plans. They cover a range of activities, from visual inspections of motion, cables and harnesses, to repeatability checks, memory backups and lubrication. These scheduled maintenance intervals can lie anywhere from around 4,000 to 10,000 hours of operation.


Fig. 1: Industrial robots are provided with a
preventative maintenance plan. Adherence
to the plan can result in 20 years of service.

Of course, customer demand and PM schedules cannot always be synchronized with one another. Robot loading, motion and speed can result in more or less wear, resulting in maintenance occurring either too often, or not often enough. Operator training can also have an influence on wear. If the emergency halt button is used to stop the robot out of convenience, rather than following using the manufacturer’s shutdown mechanism, the braking system can suffer from early wear.

To date, continual improvement programs (CIP) have been the primary method used to file away at reducing unexpected downtime while achieving a happy medium of planned downtime. But even these are reaching the point where the cost of improvement outweighs the potential cost savings.

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