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Robots combine with safety features to speed production

29 November 2015

When implementing a robot cell one of the major considerations must be the safety of operators working in the area of the cell who also occasionally need to enter it.

Using Dual Check Safety and a series of area scanners to safely monitor robot motion area and speed, this robot is able to operate with no safety fences surrounding it
Using Dual Check Safety and a series of area scanners to safely monitor robot motion area and speed, this robot is able to operate with no safety fences surrounding it

Modern robots are almost silent in operation and very fast. More important, therefore, that manufacturers can enjoy the productivity gains that robots undoubtedly bring to their operations, while being assured of high levels of operator safety.

One approach is to deploy Fanuc’s Dual Check Safety (DCS) technology, which works in conjunction with a safety scanner and safety camera. The system ensures that robots slow down as people approach the robot cell and come to a complete standstill when any part of the operator's body moves into the cell itself.

Take a typical food packaging application involving a Fanuc LR Mate 200iD robot picking produce from different tubs and pots to create mixed retail trays. Traditionally the cell is guarded on two sides and on the remaining two sides, safety scanning technologies from Rockwell Automation - an Allen-Bradley GuardMaster SC300 hand detection safety sensor and a SafeZone safety laser scanner – are deployed.

The SafeZone safety laser scanner is set up on the cell to create two one-metre wide corridors to approach the cell. When a person enters the corridor to, say, feed in produce or to remove a filled tray, the robot slows its operational speed, as Fanuc regional sales manager, John Rainer explains:

“If someone accidentally gets closer to the robot than they should, you don’t necessarily want it to stop automatically. Slowing down might be a more appropriate response: it helps to optimise productivity, but at the same time eliminates sudden stoppages at high speeds which could lead to vacuum gripped parts being dropped due to the high inertia.”

Only when a person places a part of their body - a hand, say - through the SC300 safety sensor, will the robot stop. This vision-based protective device uses image processing technology to detect the intrusion of objects through its detection window. The sensor is continuously looking for a reflected pattern from special reflective tape around the cell entry window. When an object of a certain resolution blocks the device’s view of the pattern, the safety function is activated.

These two devices work in conjunction with Fanuc’s DCS software-based safety options, which safely monitor the robot’s position and speed, allowing safety zones to be quickly and easily designed. DCS Position Check ensures that the robot stays inside designated safe areas with adaptive zones that allow for more compact cell layouts and which allow robots and humans to share a common space in a controlled way.

The DCS Speed Check functionality makes it possible to define the maximum speed that the robot can travel during normal operation, and the speed to which it must slow in reaction to a defined event – in this case a person entering the approach corridor. It also ensures that the robot holds a position when necessary – in this case, when a hand enters the robot cell. John Rainer concludes:

“Because the robot is only slowing down when an operator approaches, rather than stopping immediately, straight away there is a productivity gain. Further, since DCS Speed Check can hold the robot at standstill when an object enters the cell, rather than the safety system enforcing a hard shut down, the cell can be up and running again much more quickly. The result is an assured level of safety along with optimised productivity.”

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