Machine & Operator Safety
New standards help make the most of shared workspaces
October 17, 2013 by Ian Brough
Last month, we discussed the new robot and robot systems safety standards ANSI/RIA15.06-2012, and the draft of CSA’s Z434-13. One of the changes in these new standards is the inclusion of definitions for shared workspaces. This is where a person and a robot can perform tasks at the same time within the safeguarded space. This is referred to as collaboration or a collaborative robot. Examples of these new robots include health care or personal robots used to help people with limited mobility, or service robots that can perform such duties as serving food and drinks. Typically, these are smaller robots with power and force limitations.
For ease of understanding, the term “safety stop” has been replaced by “protective stop.” This new term does not change the technical requirements. For example, a protective stop allows you to use alternate safeguarding strategies to stop all hazardous motion. New strategies include reducing risk by slowing the hazard to the point where the person can get out of the way easily. Definitions are also provided for safety-rated monitored speed and safety-rated reduced speed. It is also possible to allow the reduction of force or torque that would in turn reduce risk by eliminating the severity of the injury.
Another new term is “safety-rated monitored stop,” which applies to a robot drive system that has built-in safety to ensure speed and/or torque is limited to a safe value. With this capability, new robot controllers also have the ability of “safety-rated soft axis and space limiting,” and are safety rated as such, meaning that the robot controller software and hardware have a safety-rated ability to limit the range of motion. Hard stops, therefore, are no longer mandatory on new robots and controllers that have this ability.
The new standard defines four types of collaborative work — safety-rated monitored stop, hand guiding, speed and separation monitoring, and power and force limiting. Requirements for each are defined within the standards and include new safety-rated functions — speed, separation and force limiting. Since these are both hardware- and software-based systems, validating all parts of the safety function is also a requirement.
The term “inherently safe” is commonly used to describe this new generation of collaborative robots. The inclusion of safety-rated technology with the robot and its controller is leading to new ways of using robots, and the belief is that the use of robots in manufacturing is only a small part of where they can be used. The expectations are that this will significantly increase the number and type of robots being sold.
The new North American robot standards are an adoption of the ISO 10218-1 and -2 robot standards used by other ISO member countries, which ensures a truly global standard. Definitions of collaborative working and workspaces and the technology behind it, therefore, are from multiple sources and are still being tweaked.
Ian Brough is a Certified Safety Applications Specialist with SICK Inc.
This column originally appeared in the October 2013 issue of Manufacturing AUTOMATION.