3 Things You Must Be Aware of Before Using a Collaborative Robot

Key Takeaway: You will gain an understanding of the critical safety factors to consider before you begin using a collaborative robot.

Introduction

Collaborative robots (cobots) are everywhere these days. The potential for automating manual processes is vast. If you visit a trade fair, as I did a few weeks ago, you will find robots on every other stand, to say the least.

However, it is my impression that many users simply do not realize the responsibility they assume when using them. I have written this blog post to help you understand what to be aware of when you and your company want to benefit from a collaborative robot. It gets a bit technical—please bear with me—but I promise you, it is important.

A Collaborative Robot is "Partly Completed Machinery"

When putting a collaborative robot into service, the Machinery Directive 2006/42/EC constitutes the applicable European regulations. This directive states that a machine must be CE marked before it is put into use.

You have likely seen the CE mark on a wide range of everyday products. For example, if you buy a robotic lawnmower, the manufacturer has CE marked it, ensuring it is safe and complies with the requirements of the Machinery Directive.

A collaborative robot, however, is viewed as partly completed machinery according to the Machinery Directive. Partly completed machinery is an unfinished machine that does not yet have a specific purpose. This means the robot manufacturer cannot CE mark it as a finished machine.

“‘partly completed machinery’ means an assembly which is almost machinery but which cannot in itself perform a specific application. A drive system is partly completed machinery. Partly completed machinery is only intended to be incorporated into or assembled with other machinery or other partly completed machinery or equipment, thereby forming machinery to which this Directive applies”(Source: Machinery Directive 2006/42/EC)

This means that when, for example, Universal Robots sells a UR5e robot, it is not intended for any specific application. It is not delivered with a gripper or a tool that defines a specific purpose. Therefore, the robot manufacturer has not CE marked it and does not bear full responsibility for it—unlike the manufacturer of the robotic lawnmower.

They do, however, provide comprehensive assembly instructions stating how it should be used and which safety features it includes.

Who Bears the Responsibility?

Before you unpack the robot and start it up, it is vital to understand where the responsibility for the final machine lies.

The answer is that the manufacturer bears the responsibility for the final machine—the person or company that gives it a specific purpose. You become the manufacturer (or integrator) as soon as you connect and set up the robot, program it, and mount a gripper or tool.

According to the Machinery Directive, you have now commissioned a machine where the robot is an integrated part (partly completed machinery). Under the law, you are now considered the manufacturer. You are responsible for CE marking the robot according to the Machinery Directive. This means that all requirements in the Directive and its related harmonized standards must be met and documented.

This can sound difficult and daunting if you have never built machinery before. To some extent, it is—after all, this is what I do for a living. In short, it means that as the integrator of the robot, you are liable in the event of an accident. You are also responsible for providing the CE marking documentation to the authorities if something goes wrong. If the authorities can prove that the Machinery Directive was not followed, you may face a liability case.

Risk Assessment

What can you do? You start by performing a risk assessment.

There are two primary sources of danger to be aware of: the movements of the robot and the object (the tool) mounted at the end of the arm. The software controlling the robot's movements and the tool is therefore essential for user safety.

In extreme cases, a welding unit or a sharp object could be mounted on a cobot. Even if the robot's movements are not inherently dangerous, the tool certainly can be. Therefore, ensure you perform a risk assessment before using the robot with its specific tool or gripper. This is a requirement of the Machinery Directive.

The risk assessment is the most fundamental document for any machine. Here is a proposal for how a risk assessment process for a collaborative robot might look:

1. Identify Hazards: Start with a detailed review of the robot’s workspace. Identify all potential hazards, including robot movements, tools, accessories, and human interactions. Document them. Remember that the workpiece or item the robot handles can also pose a risk.
2. Assessment: Once hazards are identified, evaluate them based on the probability of an injury occurring and the potential severity of that injury.
3. Implementation of Risk Reduction Measures: Based on the assessment, take appropriate precautions. This may include changing the robot program, adding safety measures like emergency stops or fencing, or adjusting the workspace. The tool itself may also need to be adapted or changed.
4. Continuous Revision: Risk assessment is not a one-time event. It is important to regularly review and update it, especially when changes occur in the workspace or the work process. The same applies if the tool or workpiece is changed.

There are many ways to conduct a risk assessment. The above is merely a suggestion and a simplified way of looking at the process. The standard EN ISO 12100:2011 describes in detail how a risk assessment should be performed.

Most importantly, you must review the "Essential Health and Safety Requirements" of the Machinery Directive. They are the alpha and omega when it comes to identifying hazards. You will find them in ANNEX I, and I have linked to the Machinery Directive and other relevant documents at the bottom of this post.

Closing Words

Collaborative robots currently exist in a bit of a gray area. Regarding the law—the Machinery Directive—there is no room for doubt: a full CE marking is required as soon as a cobot is put into service, as it is viewed as partly completed machinery.

CE marking a machine is a comprehensive process typically performed by machine manufacturers or specialized consultants. Conversely, many people who do not work with machinery daily are not familiar with the rules or the responsibility they are assuming.

A collaborative robot often has built-in safety functions, which means it does not necessarily pose a direct risk of injury. Therefore, one might mistakenly believe they have purchased a finished machine that is 100% safe.

If you want to use a collaborative robot but are unsure how to handle safety, it is a good idea to reach out to a consultant or a machine builder. If a supplier implements a robot for you, ensure they take responsibility for the final machine. This means they must CE mark it according to the Machinery Directive.

Note: While general guidelines for the use of collaborative robots apply across industries, special rules may apply to trade fair setups and educational institutions.

‍