Industrial robot or Cobot: Which robot is better suited?

Cobots are considered an appealing and cost-effective entry point into automation. In contrast to industrial robots, people can work with or alongside Collaborative Robots (or Cobots) without the need for additional separating or non-separating protective devices. However, this is only possible under strict regulations and with limited force and performance.

Collaborative working, therefore, comes at the expense of the robot's performance. It's not uncommon for it to only become evident after the purchase that a Cobot may not be the best fit for your application. Here, you'll find out how to avoid this risk.

Can people always work hand-in-hand with Cobots?

Under real conditions, companies often find that they can only use their cobot with additional safety equipment. This turns the basic idea of this type of robot on its head: Working directly with or next to humans becomes impossible. This applies, among other things, when fast traversing is required or the robot arm is equipped with components (for example, grippers or tools) that are not designed for collaborative work. Cobot manufacturers do not always communicate these conditions fully - to the displeasure of users.

Digital Robot and Cobot: What unites and sets them apart?

Since 2010, there has been a hype around Cobots. They simplify, expand, and make automation more affordable for many applications. These features also apply to Digital Robots. They also revolutionize industrial robotics through the fusion of powerful hardware, user-friendly software, and the capabilities of the Industrial Internet-of-Things (IIoT). Both types of robots are particularly interesting for small and medium-sized enterprises (SMEs).

To implement the "Safety First" principle, robots must inherently have emergency stop and safety hold functions, multi-stage consent buttons on the control panel for manual operation, and an operation mode selection adjustable by key. Unlike Cobots, Digital Robots (and other industrial robots) do not work directly hand-in-hand with humans without separating or non-separating protective elements. To effectively use robots in industry, a safety interface should be prepared to mechanically and electronically integrate these protective elements.

However, people can still work closely with Digital Robots: on one hand, physically in secure manual operation, and on the other hand, in ongoing operation from a protected distance. This is where the digital twin of the real Digital Robot proves to be a helpful tool. It is displayed 1:1 on the touchpad or external screen, enabling easy graphical programming in teach mode. Programmed applications can also be vividly validated through the digital twin without having to move the actual robot.

Subsequent processes can be simulated using the operating software even before the start of the project - if desired, even before the real robot has arrived at the company. Networking through the Industrial Internet of Things (IIoT) further expands and simplifies the possibilities of (digital) collaboration, especially in areas like Predictive Maintenance and transparency in fleet management.

An initial interim conclusion

Especially SMEs want to enter automation easily and quickly. Therefore, initially, options like Cobots and Digital Robots are suitable for them. However, smaller and medium-sized businesses often lack the time, financial budgets, and experience to thoroughly engage with the right type of robots for their application.

In terms of safety technology, there is generally more clarity with Digital Robots compared to Cobots. The following will provide the key information about ISO standards, EU directives, and CE marking that go hand in hand with this.

What does human-robot collaboration actually mean?

The ISO standard (ISO 10218) relevant for the safe operation of industrial robots describes requirements for robot manufacturers as well as system integrators and builders in two parts. The standard distinguishes between four forms of human-robot collaboration:

• Safety-rated monitored stop
• Hand guidance
• Speed and separation monitoring
• Power and force limitation by inherent design or control

Actual collaboration only occurs in the last mentioned form. In the others, either the human or the robot is working. In the professional field, the terms coexistence or cooperation have been established instead of collaboration.

Literally, ISO 10218-1 states: "The robot is only one component in a finished collaborative robot system and is insufficient on its own for safe collaborative operation. The application of collaborative operation must be determined through the risk assessment conducted during the design of the application system."

Applied to Cobots, this means: Cobots must be built in such a way that they pose no danger to humans when they touch them (un)intentionally.

When is the collaboration between a Cobot and a human ensured?

For a long time, it was unclear what requirements needed to be met for effective collaboration. In 2016, in addition to the ISO standard, the technical specification ISO/TS 15066, applicable to Cobots, was published. It provides a closer description of the safety features that must be in place for collaborative work. For instance, it mentions a risk-free contact surface (no sharp or pointed areas and edges), sufficient enclosures and/or padding, as well as the avoidance of potential points of contact at head height.

A distinction is made between quasi-static contacts (a body part gets caught between a robot and a surface) and transient contacts (robot and human collide). ISO/TS 15066 goes into great detail and provides threshold values for nearly 30 body zones from head to foot in a pain threshold table. This clearly demonstrates the high standardized requirements in human-robot collaboration and thus, the challenges for Cobots. Manufacturers primarily address these by employing sensitive sensors in the joints of the robots, which monitor compliance with the threshold values.

Why is the CE marking so important and who is responsible for it?

Production facilities can verify compliance with safety requirements through the CE marking on the robot. The CE marking demonstrates that a machine manufacturer meets all necessary EU directives for their product. Only "complete machines" are allowed to carry a CE marking.

Since a robot arm without additional components is considered an "incomplete machine," the CE examination can only be conducted after the addition of further components (such as tools or grippers) for the entire system. The intentionally simplified and streamlined nature of Cobots may suggest that they are already "complete" according to EU directives. Therefore, companies considering automation with this type of robot should carefully assess the extent to which the responsibility for the CE marking has been transferred to them. Without this marking, the complete robot system is not allowed to operate!

For companies that receive non-CE certified "incomplete" robot arms and must conduct the assessment themselves, this can lead to delays and additional costs. In practice, industrial facilities usually rely on specialized external experts for the acceptance of the CE marking, including safety-related inspections.

Renewed safety check in the case of changes to the work area or the application 

Particularly in the case of Cobots, due to the extended safety requirements in view of the direct cooperation with humans, such an inspection may only become necessary later or again. For example, if the robot's working area changes or tools or grippers are replaced. 

This is where CE-compliant quick-start bundles (including safety technology and end effectors) or plug-and-play solutions prove to be an advantage. These are offered by manufacturers of both innovative Digital Robots and Cobots. In the best case, this provides production with a validated and tested all-in-one solution.

When is direct collaboration with cobots not possible?

It can be particularly frustrating for companies just embarking on the path of automation to realize during the risk assessment that the desired Cobot cannot be used collaboratively without separating or non-separating protection. This may be necessary, for example, if the gripper is sharp-edged or pointed, posing a risk of injury (as mentioned above). The same applies if the robot is intended for tasks like welding, milling, or laser work. Direct collaborations with humans are then naturally ruled out.

It is particularly disruptive for production planning if collaborative work is no longer possible due to a change of tool or application for the mentioned safety-related reasons. Another type of robot would then have proved to be a more sensible choice for the company.  

In any case, collaboration between humans and Cobots is a limiting factor. If they work directly next to or with each other, the speed of the robotic system is reduced to a low, low-risk level. Digital robots, which are also extremely compact and agile, can reach speeds of more than four meters per second. As a result, significantly higher production outputs are possible with them.

Furthermore, companies should consider in advance: the mandatory sensors for Cobots increase the price compared to other robots with comparable performance. It should therefore be truly necessary or at least very likely that humans and machines will come into contact during work. Otherwise, the lighter construction of Cobots, resulting in their lower performance, may bring disadvantages.

Which type of robot is the best solution for entering automation? 

• The ability for a human to work directly with a Cobot is not guaranteed. It may also turn out that collaboration is not practical for the planned application. For example, because legal requirements mandate that the Cobot can only work very slowly in tandem with a human.

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  The initially lower price of a Cobot can increase by several thousand euros due to the additional safety technology required.

• The mandatory CE conformity assessment for the application represents a higher effort for Cobots compared to Digital Robots. This is due to the particularly detailed and strict guidelines and standards for collaborative robots.

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  All of these points should be taken into account by companies when comparing Cobots with the equally flexible, cost-effective, and intuitively operable Digital Robots, to avoid any unpleasant surprises later on.