We usually see industrial robots working as standalone complete machines. However, in recent times, there has been much talk of cobots—robots that are optimised to work with humans. No less exciting is the use of robots in conjunction with production and packaging machinery. A silver bullet is not forthcoming, instead we have three completely different ways to lend machinery a robot arm. When correctly implemented to suit the respective application, machine builders and automation engineers can bring about a real boost in efficiency.
Producing ever more complex products in ever smaller batches that are also extremely cost effective, poses enormous challenges to their manufacturers, the machine and plant builders and also automation specialists. The aim is for the production plants to automatically adjust to changes in products. To do this, the plants must become more productive yet also have greater flexibility. However, for a long time the field of machine and production plant design did not feel that maximum productivity and maximum flexibility went hand in hand.
And this is where industrial robots are regarded as one way to resolve this conflict of objectives. Since the launch of the first electrically driven six-axis articulated arm robot almost 50 years ago, robots have been undertaking work that is too dangerous, too complicated, too heavy, too dirty or too monotonous for humans. From then on, complex production chains have been continuously automated and with a high degree of flexibility by employing robots upstream of, between and downstream of individual machinery.
Flexible robots in machinery
To date, robots have generally worked in their own stations—fenced robot cells. In these cells, the robots are standalone robots or grouped together. Robots do lend themselves to some tasks in and around production or packaging machinery, however, thanks to their power, repetition accuracy and very flexible kinematics.
The desire to make the most of benefits offered by robotics within individual machinery is therefore obvious. Robots are much more adaptable than those devices often used previously. Those devices are usually designed as special mechanical constructions to work on a single purpose.
Enabling Industry 4.0
When integrated within machinery, robots can assume responsibility for machining steps such as clamping, unclamping and repositioning of workpieces that take place between the individual machining steps. Robots can also feed and position parts in packaging or assembly plants, as well as de-stack parts and put them on pallets. In the plastics industry, it has long been standard practice during injection moulding that robots feed inserts or demould the finished injected parts.
Robots with greater flexibility are not only easier to adapt to the production requirements of various product variants, but they can also be used for functions that could only be achieved to limited effect or even not at all using other means. These functions include a fully automatic retooling of the machine configuration, such as tooling for a change in batch or workpiece, as a prerequisite for production in accordance with Industry 4.0 principles.
Barriers to integration
While robots have been part of day-to-day tasks in large production lines in the automotive industry for decades, they are rarely viewed as an integral part of machinery. And there are quite understandable reasons behind this viewpoint. Industrial robots are designed as completely independent systems, which is why each of them has its own control system, generally in its own control cabinet.
Communication between a machine control system and the robot control system usually takes place via interfaces—often even hard-wired. This communication method limits the ability to synchronise motion sequences, meaning that it can be tricky to achieve the cycle times expected of modern production machinery. It also takes a considerable amount of effort to integrate a robot into machinery.
Engineering, diagnostics and maintenance are carried out via in-house, mostly proprietary systems. And in-house programming languages are also generally at play. All this means that special knowledge is required to program robots. In addition, this makes it difficult to integrate the robot programs into the rest of machine automation. This is one of the reasons why many machine builders shy away from the topic of robotics.
Deeper integration
As an alternative to integrating a robot as an autonomous complete machine, it is also possible to directly integrate robot kinematics into machine automation. However, some basic conditions must be taken into account. These conditions are irrelevant when using an industrial robot as a single machine.
Absolute synchronisation, in particular, with the often very fast motion sequences in the machine is usually non-negotiable. Only uncompromising real-time behaviour in terms of both motion execution and data communication enables scores of subtasks to be merged within the product development process. As a result, a significant increase in the machine’s degree of automation is brought about.
Integration with Drive
Options to directly integrate robot kinematics are actually available. However, some robot manufacturers are still reluctant to sell their products other than in the form of complete machines. There are also multiple possibilities behind this reluctance.
Whether six-axis articulated-arm robots, SCARA robots or delta robots: The motors and gears of industrial robots are usually very carefully adapted to their mechanical motion axes. The same applies to their interaction with drive regulators or controllers. In some cases, these regulators and controllers have been specially developed by the robot manufacturers themselves.
Integrating robot kinematics as a mechatronic unit (i.e., including the servo amplifiers or drive controllers) therefore promises quick results without robot-based compatibility issues. A machine builder or automation specialist can focus on sequence control, without having to worry about the continuous path control of the axes.
It is always beneficial if, on the one hand, the machine control system supports integration of the robot drive components but, on the other, does not have its own functions to control the robot’s motion. The mere absence of separate robot control systems and the often-required own control cabinet plays a vital role in increasing the complete machine’s cost-effectiveness.
Full integration boosts productivity
Robots are most effectively integrated into machines as mere electromechanical units. Automation specialists only utilise the kinematics, including the motors and gear drives. Therefore, they are actually only lending the machine a robot arm. This shifts the interface between the traditionally separate worlds of mechanical engineering and robotics even further to the periphery.
The robot arms are controlled via servo amplifiers or drive controllers that match the machine’s overall control system. These drive controllers may be the same ones that are also used to control all other motion axes in the machine. They are addressed via the same system bus—usually Industrial Ethernet for high-performance machines—as all other peripheral modules.
The servo amplifiers used to control the robot axes are also usually available with integrated safety functions. In many cases, these amplifiers use the same internal communication networks for safety-related reactions via integrated safety protocols. A separate safety control unit for the robot is not required, as robot kinematics can be seamlessly integrated into the safety technology of the complete machine.
Changing methods to boost productivity
This hardware standardisation not only brings advantages to the machine user in terms of operation and maintenance. It also has the advantage that all elements of control technology—sequence, motion and safety control—form a standardised, closed-loop unit.
The most obvious benefit is in the area of programming. If the machine control system provides corresponding functions for continuous control path planning, machine software developers will not notice discernible difference between implementing a single axis or a robot in a machine.
This means that all aspects, all modules of the machine software, can flow into a complete software engineering plant. Developers can simulate the machine as a whole and test the interaction of all works on the digital twin prior to investing in the construction of expensive prototypes.
This deep integration also facilitates accurate synchronisation between machine and robot movements. The rapid reaction to sensor signals in the microsecond range allows the robot to grab or set down workpieces in motion, without slowing down the process or even stopping it. Changing methods in workpiece manipulation made possible by this can greatly boost a machine’s productivity and flexibility.
Images: Adobe Stock
