(Translation of German Websites)
A collaborative robot – also called Cobot – you can buy easily. In many cases the prices of these robots are low. Furthermore, the performance of such robots sounds good. For instance, they are advertised to be ready for use within short time without any programming knowledge. And: They are praised to be used without any safety fence.
However, should you perhaps know anything about safety? We collected some important steps on the way to your safe Cobot project.
A successful Cobot project needs a suitable application. This is because of occupational safety. Speed, force, pressure and space are often restricted.
Select
Step 1: Selection of robot
For selection of robot as part of your Cobot project you should take some time. In any case, statements such as “This robot is the cheapest” or “This robot has the most payload” should never be the exclusive criteria for your buy.
Despite produktion requirements, from the perspective of occupational safety, you should answer following questions:
- Which safety functions does the application require?
- Does the selected robot provide these safety functions?
- Can the robot manufacturer prove the required safety level?
If the Cobot is foreseen to be used without safety fence from experience the safety functions force- or torque monitoring, speed monitoring and space monitoring are always required.
According to the relevant standards EN ISO 10218-1 and EN ISO 10218-2 these functions shall fulfill Category 3, PLd. This control requirement is related to EN ISO 13849-1. Each robot supplier should be familiar with these requirements. Please ask!
Make
Step 2: Risk assessment, construction, parametrization, validation
A central point of safety related construction within Cobot project is the parametrization of safety functions. This includes:
- What is the maximum speed limit the robot inclusive tools and workpieces shall not exceed?
- What is the maximum space limit the robot inclusive tools and workpieces shall not exceed?
- What is the maximum force or pressure limit the robot inclusive tools and workpieces shall not exceed?
Forces or pressures coming from a possible contact between robot and human body parts generally can be determined reliably only by measurement. Therefore, you should determine the later measurement points already within risk assessment. In case of table applications, a measurement point covering the possible clamping situation of hands in the robot tool area normally is indispensable. In many cases, another measurement point is the incidental bump of robot arm at upper body.
After construction and parametrization of Cobot system you should measure the contact forces and pressures as part of validation at running system. Please record data. If limits are exceeded during measurement parameters mentioned above or other constructive details shall be adjusted. Examples are surface shape, moving mass or path planning. The measurement then shall be repeated. Further information and permissible limits you can find in DGUV FBHM 080.
Record
Step 3: Documentation
The risk assessment is part of the technical file and shall be recorded according Machinery Directive. Examples of written risk assessments you can find e.G. in DGUV-Information 209-074.
As required for each other machine also a Cobot system requires an instruction handbook which shall be delivered with the Cobot-system. Please be aware of the so-called Indented Use. This means: For what is the machine intended to do and for what not.
Provide an EC declaration of conformity. Examples you can find also in DGUV-Information 209-074.
Provide a type plate at the Cobot-system showing name and address of integrator, description of the machine and CE-mark.
Ready !
Of course only important, experience based points have been summarized here. Further information you can find at the website of Berufsgenossenschaft
