Chapter 3.9
We have summarized the most vital information about safety concepts for your robot application below. Learn how to prevent access to hazards, limit robot motion, and ensure safe human-robot interaction. Discover the significance of safety fencing, advanced detection systems, and the importance of planning collaboration workspaces.
This infographic illustrates how to think critically about safety distances for industrial robots. Learn why guard fencing matters, how accidents occur, and when fences might not be the only solution. Discover the key considerations to keep people safe around robots.
Robots are incredibly versatile, offering economical automation solutions. However, they can also be quite dangerous.
Large, high-speed robots, may cause very serious injury by crushing and impact. Therefore, robot safety has been standardised internationally in (EN) ISO 10218-1 and -2 and for the USA in the almost identical ANSI/RIA R15.06. Additionally, a standard for mobile robots has been published with ANSI/RIA R15.08.
Robot safety is built on three elements:
The third element, making physical contact safe, is a relatively new concept, often referred to as collaborative robot operation. It means a specially designed robot system and an operator work within the same workspace or overlapping workspaces. First, the collaboration workspace and the desired human and robot interaction must be planned. Then, the risks are identified, and appropriate safety measures are implemented.
The most advanced safety measure is the use of a collaborative robot, sometimes referred to as a “cobot”.
A collaborative robot operates at limited force and speed. Humans encountering a moving collaborative robot will not be injured, although they may feel some pain. Years of extensive testing have resulted in a list of force, speed, and energy limits that humans can endure when subjected to physical contact with machine elements (see ISO TS 15066). Collaborative robots moving within these limits may be considered safe for human-robot interaction. However, that does not mean such applications are automatically safe. The entire context of the robot and the tool handled by the robot (the end effector) must be considered carefully.
Example:
In the graphics, a human operator and a robot share the collaborative workspace.
Safety measures:
In the graphics to the right, a human operator and a robot share the light-grey collaborative workspace.
Safety Fencing:
Robot safety largely depends on closed "cells" with fencing and access doors. But in many applications monitoring systems are additionally needed or may even replace the robot "cage".
Advanced detection systems:
Beware of persons remaining inside the hazard zone behind the detection devices. If that is possible, additional safety measures may be needed.
Fencing may be used to create a “protected space”, but it must not normally be used to define the “limited space”.
Robots colliding with fences at high speed or with significant force can cause deformation, even in robust fencing, posing potential safety hazards. Additionally, fences may allow individuals to stick their fingers through the openings, increasing the risk of injury.
To mitigate these issues, a minimum clearance of 120 to 200 mm must be maintained between the limited space and the outer edge of the fence. Read more about calculating and determining the proper height and distance of guard fencing in chapter 3.2 “Selecting machine guards”.
Therefore, relying solely on so-called “robot-safe” fencing is insufficient. Instead, implement appropriate limiting devices to ensure safety, such as:
Fences are meant to keep people out, not the robot in.
Many people ask for “robot-safe” fencing or point to test results of fence manufacturers showing impact resistance of 2000 joules or more.
The question itself reveals a misconception about robot safety. Robot safety standards require that robot motion be limited by means other than fencing or other safeguards.
A robot‘s motion range depends on its size. Often this “maximum space” is much bigger than needed for the operation at hand. Since system designers want to use as little floor space as possible, the robot is programmed to keep to a much smaller “limited space”. Then fences, light curtains and range scanners are used to define a “protected space” around the limited space that persons must not enter.
However, a safety distance is practically always needed between the limited space and the protected space. Why? Because the robot needs time to slow down and come to a standstill when a person entering the protected space is detected (by a light-barrier, scanner, camera, or door switch).
