Torrance cited a number of examples of how the two goals can be met by making design changes on a basic robot work cell. In one case, for instance, an operator might load parts in a robot cell and then exit the cell, passing through a light curtain to hit a start button to begin the robot cycle before walking in another direction to perform a different task.
But with a technique known as Presence Sensing Device Initiation (PSDI), the light curtain itself is used to automatically energize the robot when it senses the operator leaving the cell. This keeps the operator safe while also eliminating the unnecessary steps, thus meeting Lean principles of waste elimination, Torrance explained.
In another example, a “safe vision system” using overhead-mounted cameras might be used in conjunction with software to create 3D zones of any shape around the robot, Torrance said. A person moving into a warning zone surrounding the robot work area could trigger an alarm and cause the robot to slow down, for example, while an intrusion into a detection zone closer to the robot work area could be programmed to shut down the robot.
Again, this solution meets the goals of keeping workers safe, while also eliminating the need for mechanical safety fencing, guard switches and other equipment around the cell, saving both floor space and cost, Torrance said.
Pilz Automation Safety L.P.