“Robot safety is an issue that transcends the requirements of specific industry sectors or applications,” said Darren Whittall, technical manager at Fanuc UK. “In addition to regulatory requirements, there’s also a moral obligation to ensure that the workforce is properly protected. If overlooked, robot-related accidents can have substantial financial and reputation implications, too.”
Unlike more predictable automated operations, robots can produce powerful and rapid movements through a large operational space, and the path of a robot and/or its arm is difficult for a human to accurately predict.
Most robot-related accidents occur during non-routine operating conditions; for example, when an operator temporarily enters the robot’s working envelope to complete programming, maintenance, testing, setup or adjustment tasks.
Until recently, the only acceptable way to make a robot safe was to banish humans from the robot working area using physical guarding solutions. However, the development of software-enabled safety technology has changed this.
Software-enabled safety is now becoming accepted practice. Dual Check Safety (DCS) Position & Speed Check software, for example, is a package of software-based safety options integrated into Fanuc’s R30iA and R30iB robot controllers, ensuring safe monitoring of robot position and speed.
It allows safety zones to be quickly and easily designed, and removes the need for hardware such as limit switches and zone switches.
“Having less hardware means that safety can be integrated more cost-effectively,” said Whittall. “Traditionally, it has been necessary to bolt a number of sensors onto a robot to determine where the robot and its arm are positioned within the cell at any time. This can cost several thousand pounds depending on the application and the number of sensors needed. With a software-based solution, these sensors are not required, reducing hardware costs, not to mention the physical time it takes to install the sensors.”
He estimates that it’s possible to achieve a 50% cost reduction for a small, single robot system with multiple safety devices, just in terms of the hardware savings vs a software-based safety solution.
DCS Position Check features ensure that the robot stays inside designated safe areas, and the robot can be locked out of areas where it may cause a hazard.
Position Check can identify multiple areas of the robot, including any attached end effectors. The safe zones can be modelled within the software using geometric shapes of up to eight vertical lines each. These areas can be adapted – enabled and disabled to change the areas that the robot is not allowed to enter – depending on the task it’s undertaking and the changing conditions of a defined area. The use of these adaptive zones allows for a more compact cell layout and enables humans and robots to safely share a common space in a controlled way.
The DCS Speed Check functionality makes it possible to define the maximum robot speed. Speed can also be changed in reaction to a defined event, in addition to ensuring that the robot holds a position when necessary.
“Often, there are rotary fixtures within a cell that mustn’t move while the operator is undertaking a loading procedure,” said Darren Whittall.
Fanuc’s DCS offering also includes the optional Safety PMC (programmable machine control). An addition to the standard PMC, it allows the robot to control the entire cell, including the safety functionality, negating the need for additional dedicated safety hardware, such as a safety PLC.
There are many features available within Fanuc’s DCS Position & Speed Check to ensure worker safety in robot applications. In addition to achieving this in the most cost-effective way, it also has the potential to enhance productivity by allowing humans and robots to inhabit the same space in a controlled and safe manner.
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