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Collaborative Robot Safety
Installing a cobot safely requires a detailed risk assessment. Consideration should be given to the risks that may occur during the cobots cycle, its movements and the human interaction
What safety is involved around a collaborative robot?
Although there is lots of safety information available regarding collaborative robots, it is often overlooked due to the way cobots have been marketed. Often sold as 'safe out of the box', this is true until the tooling or gripper is attached to the end. This then changes the whole safety of the cobot and the safety of the application then needs to be risk assessed.
Installing a cobot safely requires a detailed risk assessment. Consideration should be given to the risks that may occur during the cobots cycle, its movements and the human interaction. As cobots are lightweight and portable they have a variety of uses within the same work environment. For each separate task and location, a risk assessment should be completed.
Talk to us as you begin your collaborative journey. We understand the safety and can assist and guide you, to ensure that what you want to achieve is achievable. Design concepts, risk assessments and safety testing are just some of the ways in which we can help.
Common Mistakes Made With Cobot Safety
Assuming that cobots are inherently safe
Yes, cobots are a safe alternative to traditional industrial robots. They are designed to operate or work around humans, however, this doesn't mean that they are safe. You need to assess them on an application basis. It is often assumed that cobots are safe in all situations. As a result, they can end up performing dangerous actions with the cobot.
Not doing a risk assessment
It is critical when implementing cobots to have a detailed risk assessment. You need to properly assess all aspects of the task and judge its overall safety. Unfortunately, some people think that they can bypass the risk assessment when it comes to cobots, referring back to the statement above. This is not a good idea!
The detail within the risk assessment
One of the most common mistakes with cobots is capturing the correct detail in the risk assessment. A rough outline of the task will show a basic operation, but won't go into enough detail to identify the potential safety issues. The flip side to this is over-complicating the risk assessment. Too much detail, however and things could be easily lost. Keep the functional requirement specification separate from the risk assessment.
The cobot and its installation is defined as a machine and is subject to all the legal requirements of the machinery directive and other applicable directives. This must be fully risk assessed and the technical file built and retained for 10 years. Within the UK, the requirements of PUWER, also need to be met. Currently the guidance for collaborative robot safety can be found in ISO/TS 15066
Failing to account for end tooling & parts
The safety limits of collaborative robots only apply to the robot itself. The end of arm tooling you choose for the application and the part you handle can have a huge impact on the overall safety of the robot and the application. Long parts could extend beyond the work-space. Just because the cobot won't go outside the work-space doesn't mean the part won't. What about weight? If the part is heavy it could fall to the floor, injuring a person. The cobot application could be safe but the risk assessment should capture the end of arm tooling and parts being handled and any hazards that either of these may create.
Only considering normal operation
Issues often occur when something unexpected happens. The risk assessment needs to consider both foreseeable and unforeseeable hazards. Consider the 'what ifs'. There's no such thing as a stupid question.
Only considering the risk from one activity
It is easy to consider the risks based on normal operation. Cobot applications have many different steps to create a working process. All of these affect the safety of the overall task. Give consideration to those tasks that are not an operation.
Not involving the relevant people
A risk assessment created by a single person may capture certain hazards, but they may not see everything that poses a risk. Having those who will use or maintain the cobot application involved is a key element to the overall safety process.
Using a risk assessment to justify a decision
There are cases where people have used the risk assessment to justify decisions which have already been made.
For instance, a person might decide they don't want to purchase a laser safety scanner, so they use the risk assessment to show that one is not needed. This can be seen as a method to justify what can be seen as an unsafe solution.
Not considering ALARP
ALARP stands for "As Low As Reasonably Practicable." It's a phrase that is pushed out across the safety industry, with a view to reduce the risk of an activity as low as is reasonably practicable. This means that you should consider all of the risks of the robot application and reduce them to a sufficient level.
Not linking hazards with reduction measures
A thorough risk assessment identifies which parts of the robot application are likely to cause a hazard. Identifying them is one thing, however you also need to say how you will mitigate these hazards with some form of a reduction measure. By doing this, it will show that the identified hazard has been addressed and at the same time not introduced any further hazards.
Not keeping up to date risk assessments
The risk assessment is only useful if it applies to the current application. If your risk assessment was written at the time of manufacture or on installation, its likely that it will be out of date. 2 years ago.
Collaborative robot programming interfaces are easy to modify allowing for different or extra end effectors, picking different parts or moving them to a completely new task. As a result, the risk assessment should be regularly updated.