May 2023 Volume 5

AUTOMATION

operation, purge robot, and move to a known safe position should be a part of the control package. All evil begins when an untrained operator picks up the teach pendant. A better method is to use controls on the HMI run time screen to bring up functions that cover the condition. For example - have a function that allows the operator to halt production which causes the robot to move to its safe position and discard any billet in hand. Another powerful feature is to teach a “move safe” routine such that the robot will retract along a known path andmove to its home (safe) position via one touch of a button. This programming takes longer, but it avoids accidentally jogging the robot into dies, the press, etc. Controlling Access Many of our customers request that physical access to the automation be controlled by locking door safety switches. This approach prevents an operator from pulling open a safety door when a robot is in harm’s way, like inside the press. Also, unexpected door openings generate an immediate servo off condition which is hard on the equipment. By setting up the controls to require the operator to “request access”, the robot will finish its motion and move to a known position before the door unlocks and allows the operator access. Another decision is required regarding granting access to cell control screens. Many times, the screens are designed for specific tasks and

do not need to be shared. Using passwords or better yet ID badges, the cell controls can be designed to limit access to the responsible party. For example, the ability to move the robot to a maintenance position is only available to the maintenance technicians. Robot Safety Zones One of the very powerful features built into new robots is their ability to create programmable zones. For instance, take a 6-axis robot whose envelope is essentially a sphere with a hollow center. Using this safety rated software, the programmer can create a zone which can be a box which encapsulates the volume of space the robot will move in for normal operation. Multiple zones can be created. The robot is modeled as well as the robot EOAT with and without part. The software checks to make sure the robot and EOAT does not leave the zone (or enter it depending on programming). This software monitors outside signals (safety rated) and can dynamically allow the robot entry into various zones based upon the current state of the cell. The software monitors position and speed. So even if you have an inexperienced operator trying to jog a robot out of harm’s way, he will not be able to cross a zone boundary. FANUC Robotics call this feature Dual Check Safety (DCS). DCS uses dual processors to monitor and compare feedback from the encoders.

DSC zones in a trim press application.

FIA MAGAZINE | MAY 2023 46