When is a collaborative robot the most appropriate option?

Interreg Factory 4.0

 

Cobots are gaining popularity in the industry because they are easy to set up, program and operate, while also providing secure collaboration with people and flexibility. However, this does not have to be at the expense of industrial robots. The choice rather depends on the application and environment.

The technology of collaborative robots was developed almost a decade ago. Today there are about 30 manufacturers worldwide of mostly small robots with a payload of up to 7 kg, which focus on simple manipulation tasks. Success factors are the ease of operation and the fact that these robots proved to be a perfect first introduction to robotics. The resulting optimism has motivated many new users to take their first steps, to become familiar with the technology and to take a more pragmatic approach to robotics applications.

Some new applications were not suitable for conventional robots because they were too large, not flexible enough or too expensive. Industrial users are increasingly investing in this new technology to get rid of the annoying security fences that come with space requirements and extra costs in traditional robot cells. Cobots are cost effective, flexible and easy to implement due to their core tasks (easy handling).

Cobots can be seen as the next step in the evolution of conventional robots, as they offer the reconciliatory prospect of man and machine no longer competing in the smart digital factory of the future, but working side by side. This does not mean that industrial robots in their cells are a thing of the past, but rather that cobots will complement them.

After the search to implement collaborative robots, they are now looking for ‘effectively usable applications’: applications in which the interaction between man and robot offers real advantages. It is no longer a question of introducing the cobots at any cost, but of finding the most suitable robot solution for each application.

Safety

There was still a lot of work to be done in the area of safety in the human-robot interaction. Today, we no longer speak of a safe robot, but about a safe application. An individual safety assessment must be carried out for each robotic workstation. This not only concerns the robot itself, but the entire situation of the workstation (position, direction of movement, speeds, grippers/tools, workpieces, installation, safety technology) and this for each individual situation, to be conducted by a certification body. In the industry it is known that 80 percent of all ‘collaborative’ robots end up behind a safety device - in many cases this is a safety fence.

However, how can a robot be safe in the vicinity of people and at the same time be almost as fast as we are used from traditional robots? The answer is called ‘hybrid collaborative robot’: a full industrial robot that can work at high speed, but which automatically slows down to a safe speed as soon as a person enters the immediate vicinity of the workplace. Standard safety features are used to detect whether or not someone is present via a laser scanner, safety curtain or mat. This technology is needed in many projects, with or without a cooperating robot, to deal with hazards caused by tensioning devices, grippers or workpieces. In this way, it can also be used to set the robot in a different mode.

The time span of human-robot interaction in relation to the total cycle time is essential when designing a workstation:

Permanent human-robot-interaction : If robots and people work together permanently, if speed is not a decisive factor or if people still have to pass by the robot, then cobots may be the right concept. Cycle times are not the main goal, but rather the synergistic effects achieved through smart parallel or cooperative work between man and robot, e.g. for support tasks or to cover or machine workpieces during manual assembly.

Temporary human-robot interaction : If there are longer phases in which people and robots work together and other phases in which there are no people present, hybrid collaborative robots are a useful option. This also applies to workstations in the middle of a passageway where employees pass with unpredictable frequency and duration of passage.

Minimum human-robot interaction : If the interaction between man and robot is limited to a very short period of time (e.g. loading and unloading workpieces), classical industrial robots are usually the most useful option. They stop when a person is present, but make full use of their speed advantage for the rest of the time.

Costs

Compared to a traditional industrial robot, a collaborative robot is not cheaper to buy, at least not in realistic terms, when payloads and significantly higher performance are taken into account. Add to this the cost of collaborative grippers rather than simple 2-finger grippers, an injury-free design of the equipment, employee guidance on the human-machine interface, access and safety technology and the necessary safety assessments by the operator with the risk of the possible need for rework and it becomes clear that a workstation with collaborative robot in the industry will generally be more expensive than a traditional robot cell.

Simple operation

A major advantage of collaborative robot technology is the simplified operation, parameterisation and programming, in particular the intuitive manual guidance, but also the tablet-like redesign of the robot control unit, compared to the traditional menu-based or code-based manual control devices (teach pendant).

Each of the three technologies has its advantages and disadvantages: manual guidance is good for frequent adjustments of simple pick-and-place applications, but it is hardly possible to learn processes with lasers or trajectories with trembling hands to within one hundredth of a millimetre accuracy. The traditional hand-held equipment offers full functionality and is the preferred choice for experienced robot programmers when the application is rarely reprogrammed and the full logic, function and command range of the robot control must be used. A tablet-based user interface, on the other hand, is a nice medium for the ‘app generation’.

Easy commissioning and integration

Movies about unpacking the cobot, e-learning, FAQs, how-to-blogs, plug&play: all this can be found in the world of collaborative robots and offers basic knowledge and simplifies commissioning for inexperienced users and system operators. Unfortunately and despite everything, very few robotic workstations in the industry can easily be built together without the necessary experience.

Conclusion

Collaborative robots offer opportunities for applications that require real human-robot interaction, including new applications for which conventional robots were previously too large or economically unattractive. However, further development is required, including increasing payloads, better operability of all robotic systems, the development of plug-and-play ecosystems, ...

Cobots will not replace traditional robots, but rather complement them, as a new element in the toolbox of flexible automation, which is first and foremost technology-neutral, bound to an intelligent, suitable and economical solution, and not to the unconditional implementation of collaborative robot technology.

(Source : Yaskawa)

This article is written in the context of Interreg Factory 4.0.