Industrial robots perform key tasks at various points in automated production. Technically induced operational interruptions must therefore be reliably avoided - even if the manipulators and control systems used have been in operation for many years or even decades. Tailor-made maintenance strategies are the prerequisite for this. DIN 31051, which also applies to industrial robots, specifies various approaches and describes the main types of maintenance as corrective, preventive and predictive. Corrective maintenance involves replacing worn parts and repairing defective system components. Such unplanned downtimes are extremely cost-intensive for companies. In addition, experience shows that selective corrective maintenance results in faster overall machine wear.

According to the definition in DIN EN 13306, 7.1, the task of preventive maintenance management is to reduce the probability of failure or limited functional performance. In systems with industrial robots, the probability of failure is directly linked to the life cycle of the robot. This can be fundamentally and sustainably improved through preventive maintenance management. In the long term, preventive maintenance management ensures that the value of the production goods is maintained and forms the basis for long-term budget planning. An annual inspection by the robot manufacturer documents the condition of the systems and can serve as a basis for audits and maintenance planning.

There are also economic advantages to preventive maintenance management: assuming an increase in efficiency of 0.25% per year, a better maintained machine with 4,000 operating hours per year will stand idle 10 hours less. Assuming a machine hourly rate of 2,500 euros, this corresponds to a saving of 25,000 euros in one year.

In addition, long-term studies by customers have shown that the significant improvement in system availability has greatly reduced storage costs, as many critical spare part components no longer need to be kept in stock at all times. This also has a positive effect on risk assessment.

Retrofit as a low-cost alternative

High availability and a longer service life of industrial robots also mean a better return on investment. Whereas a product cycle used to be designed for a total service life of eight to a maximum of twelve years, today it is often 16 to 24 years. However, the actual life cycle of a robot has remained unchanged at five to eight years, which means that conversions or new purchases during the product cycle need to be considered.

As an alternative to cost-intensive new purchases, which often entail a generation change at the manufacturer and thus additional costs for reprogramming and employee training, robot manufacturers also offer replacement devices and systematic retrofit programs in order to keep production disruption to a minimum. Finally, the use of an identical model does not constitute a "substantial modification of machinery" within the meaning of the EC Machinery Directive. This means that no new safety test and no new CE marking are required, which is why many customers prefer replacement and retrofit programs.

Software options for end-to-end condition monitoring

Software support makes it possible to adapt maintenance intervals to the specific system, detect wear at an early stage and positively influence system availability and robot service life.

© Yaskawa

Predictive maintenance allows system-specific maintenance management to be created from the time of purchase. Data should be retrievable in order to reflect the condition of the robot and the system. Continuous condition monitoring allows irregularities in wear and tear to be detected at an early stage. This data can then be used to take appropriate countermeasures or schedule preventive maintenance.

Robot manufacturers generally offer software options for continuous condition monitoring, which can be used to visualize the condition of individual robot components. The "Yaskawa Cockpit" software platform, for example, makes it possible to collect and analyze relevant process and system data not only from robots, but also from entire networked production systems in a scalable database in real time or to make it available for external processing. Visualization takes place directly and comprehensibly in the software platform. Among other things, the company relies on the standard OPC UA interface.

The live data collected over a certain period of time represents the performance of a system, from which conclusions can be drawn about possible weak points. Based on the performance data, Yaskawa Cockpit projects a forecast of the future performance of the plant. At the same time, the software generates schedules for preventive maintenance and necessary measures to keep production running as smoothly as possible. In the event of a malfunction, the system provides targeted information to get production up and running again quickly. The data can be passed on to existing ERP, MES, big data or AI environments under the highest security standards to enable well-founded decisions to be made on this basis.

In addition to preventive maintenance by the robot manufacturer, a 360° image of the robot and the system can be created. Thanks to this data, it is possible to adapt maintenance intervals to the specific system
to detect irregular wear at an early stage and counteract it, and to positively influence system availability and robot service life through hardware and software optimizations.

Total Customer Support

Nevertheless, the possibilities of regular maintenance also have their limits. These are often reached, for example, when the system with the robot is to be used for other purposes or converted to a completely new product. Even in such cases, it is desirable to continue using as many system components as possible. In contrast to a retrofit, however, a complete modernization of the system usually means a "substantial modification of machinery" within the meaning of the EC Machinery Directive (Machinery Directive/2006/42/EC). In this case, the safety technology must also be upgraded to the current state of the art, which then also requires renewed CE certification. Yaskawa covers this need with its engineering and CE and safety consulting services.

Retrofit programs and safety consulting are components of a broad service portfolio that Yaskawa has combined under the heading "Total Customer Support (TCS)". The focus is on preventive maintenance, service and spare parts support, optimization and modernization as well as optimum all-round support throughout the entire product life cycle.

The author: Siegfried Schauer, Supply Chain Management TCS, Yaskawa Europe - Robotics Division

This article first appeared on our sister portal www.scope-online.de