Producing ever more complex products in ever smaller batch sizes with high efficiency poses enormous challenges for their manufacturers and therefore for machine and system manufacturers and automation specialists. Production systems must be able to adapt automatically to product changes. At the same time, they must become more productive and more flexible. In machine and production plant construction, however, maximum productivity and maximum flexibility were long considered incompatible.

Industrial robots are seen as one of the means of resolving this conflict. Since the market launch of the first electrically driven six-axis articulated arm robot almost 50 years ago, robots have been taking over work that is too dangerous, too complicated, too heavy, too dirty or too monotonous for humans. Since then, their use before, between and after the individual machines has made it possible to automate even complex production chains consistently and with a high degree of flexibility.

Robot flexibility in the machines

However, until now robots have mostly worked in their own stations, the fenced-in robot cells. There they remain alone or among themselves. However, there are also tasks in and around production or packaging machines for which robots, with their power, repeat accuracy and highly flexible kinematics, are ideal. The desire to utilize the advantages of robotics within individual machines is therefore obvious. This is because robots are much more adaptable than the devices often used previously, which are usually designed as special mechanical constructions for a single purpose. When integrated into machines, robots can take over processing steps such as the clamping, unclamping and reclamping of workpieces between individual processing steps. They can also feed and position parts in packaging or assembly systems and destack and palletize them. The more flexible robots are not only easier to adapt to the production requirements of different product variants, they can also be used for functions that could only be realized to a limited extent or not at all with other means. This includes fully automatic retooling of the machine configuration, including tooling for a batch or workpiece change.

Integration with hurdles

While robots have been part of everyday life in large production lines in the automotive industry for decades, they are rarely found as an integral part of machines. There are perfectly understandable reasons for this. Industrial robots are designed as completely independent systems. This is why each of them has its own control system. Communication between a machine controller and the robot controller usually takes place via interfaces, some of which are even hard-wired. This limits the possibilities for synchronizing the motion sequences. As a result, it is not easy to achieve the cycle times expected of modern production machines.

The effort required to integrate a robot into machines is also considerable in other respects. Engineering, diagnostics and maintenance are carried out using separate, mostly proprietary systems. They are largely carried out using proprietary programming languages. Specialist knowledge is therefore required for robot programming. This also makes it difficult to integrate the robot programs into the rest of the machine automation system. This is one of the reasons why many machine builders shy away from the topic of robotics.

The direct integration of robot kinematics into the machine automation system is an alternative to integrating a robot as a stand-alone machine. However, there are a number of framework conditions that need to be taken into account that are not relevant when using an industrial robot as a stand-alone machine. Above all, absolute synchronization with the often very fast motion sequences in the machine is usually essential. Only uncompromising real-time behavior, both in terms of motion execution and data communication, makes it possible to combine many subtasks in the product creation process and thus significantly increase the degree of automation of a machine.

Integration with Drive

There are several options for the direct integration of robot kinematics. Whether six-axis articulated arm, SCARA or delta robots, the motors and gears of industrial robots are usually very carefully matched to their mechanical motion axes. The same applies to their interaction with the drive controllers or controls. In some cases, these are also special developments by the robot manufacturer. The integration of the robot kinematics as a mechatronic unit, i.e. including the servo drives and drive controllers, therefore promises fast results without compatibility issues on the robot side. This allows a machine builder or automation specialist to concentrate on the sequence control without having to worry about the path control of the axes. This is always an advantage if the machine controller supports the integration of the robot's drive components well, but does not have its own functions for controlling the robot movement. The elimination of the separate robot controller and the separate control cabinet often required for this alone makes a significant contribution to the greater cost-effectiveness of the overall machine.

Full integration increases productivity

The deep integration of robot kinematics into production or packaging machines can increase their productivity and flexibility enormously. © prescott09/stock.adobe.com

The most effective way to integrate robots into machines is as mere electromechanical units. In this case, automation engineers only use the kinematics, including the motors and gears. They therefore only lend the machine a robot arm. This shifts the interface between the traditionally separate worlds of mechanical engineering and robotics even further to the periphery. In this case, the robot arms are controlled via servo amplifiers or drive controllers that match the overall control of the machine. These can be the same drive controllers that are also used to control all other movement axes in the machine. These are addressed via the same system bus as all other peripheral modules.

The servo drives used to control the robot axes are also usually available with integrated safety functions. In many cases, these use the same internal communication networks for safety-related reactions via integrated safety protocols. As the robot kinematics can be seamlessly integrated into the safety technology of the overall machine in this way, there is no need for a separate safety controller for the robot. This standardization of the hardware not only benefits the machine user in terms of operation and maintenance. It also has the advantage that all elements of the control technology - the sequence, motion and safety control - form a uniform, self-contained unit.

The most obvious benefit is in the area of programming. If the machine control system provides appropriate functions for path planning, there is basically no difference for the developers of the machine software between implementing a single axis or a robot in a machine. This means that all aspects, all modules of the machine software can be incorporated into a complete software package. This makes it possible to simulate the machine as a whole and test the interaction of all systems on the digital twin before investing in the construction of expensive prototypes. This deep integration also facilitates precise synchronization between machine and robot movements. Thanks to the rapid response to sensor signals in the microsecond range, the robot can pick up or set down moving workpieces without slowing down or even stopping the process. The resulting change of method in workpiece manipulation can increase the productivity and flexibility of a machine enormously.