Robotics – Compliant Collaboration

The subject is aimed primary at heavy industry, with robotic integration which may include pick and place, part manipulation, laser cutting or welding or paint spraying amongst many to choose from and is largely relevant to machinery designers and machinery integrators however is useful information to all stakeholders looking to implement robotics into their product solution.

Regulations and Standards

Robots fall under the definition of machinery and are likely to fall within the scope of The Supply of Machinery Safety Regulations 2008 (Unless covered by exemptions e.g. not used within military of naval purposes). These robots, and assemblies to which the robots are integrated, are required to comply with the relevant essential health and safety requirements (EHSR).

All machinery must have been designed to eliminate, reduce or mitigate risks to an acceptable level, which is evidenced through the risk assessment process. ISO 12100 provides guidance for risk assessment and directs designers towards various other standards for more specific information relating to management of the potential risks.

Amongst these standards referenced are two Type-C standards that provide guidance for industrial robot applications and a presumption of conformity to many of the EHSR when adopting the measures specified.

• BS EN ISO 10218-1:2011 Robots and robotic devices. Safety requirements for industrial robots. Robots. – specifies measures to be taken for the design of robots themselves.
• BS EN ISO 10218-2:2011 Robots and robotic devices. Safety requirements for industrial robots. Robot systems and integration. – specifies measures to be taken for system designers integrating robots or robotic devices into machinery.

These standards do not subtract from or remove the necessity for the implementation of other protective measures or standards that may be applicable to the overall process or other equipment used within a robot cell or integrated manufacturing system.

Application based selection

If we were to take an example of a system application, a robot intended for manipulating a device into a set position, the device could be anything from a scanner to a staple gun. The parts to be processed are manually loaded and unloaded by an operator. Once loaded, the operator initiates the machine to carry out its process function.

In this example the robot selected is a Cobot 6 axis arm allowing an operator access to the process area to quickly load and unload the parts and press a local stop/start button to initiate the robot sequence. The Cobot provides a safety integrated function whereby contact with the operator results in the robot carrying out a safe stop function.

The question that needs to be posed is whether a Cobot (complete with safe stop function on contact) is suitable for this application or if alternative means of safety would be more suited.

The fundamentals of machinery risk reduction follow the hierarchy of control principal:

Note that a safe stop function would not be applied, or react, until contact has been made, meaning that the person at risk has already entered the hazardous zone. Therefore, the safeguard has not brought the hazard to a safe state before the operator can come into contact. It does in fact wait for the worst-case scenario (contact) before initiating the safeguard.

Where interactions between robot and operator are required (collaboration) this would be acceptable. However, if there were no requirement for collaboration or for an operator to be in the hazardous area during operation, then the solution is not as safe as it might first appear to be.

Some robotic solutions are designed with interlocked guarding that ensure the hazards are brought to a safe state before the operator can come into contact with them. The word to emphasise here is ‘before’. This gives the opportunity to recognise where a safety function may have failed and react accordingly by preventing access into the guarded area and/or initiating an Emergency Stop to prevent a hazardous situation leading to an injury.

Summary

It is up to the manufacturer and/or employer to ensure that the method implemented provides the least risk of causing injury.

Collaborative robots provide exceptional capability and are ‘safe’ when implemented correctly in the right circumstances and environment, however we must be sure that selection of this technology provides the safest means of ensuring the operators safety. If there is no requirement for an operator to be in the hazardous area during operation, then further consideration should be given to using a Cobot as the means of providing safety.