Page 24 - MetalForming November 2022
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  sure to select the right solution for the job, Wenzel warns.
“One aspect of cobots that people might overlook when trying to auto- mate a press,” he says: “Cobots are great because you do not need to guard the cobot itself, but don’t forget that you still need to guard the press. On many press controls, if you put a light curtain around the point of operation and then pass through the light with the automation, the machine will drop out of automatic mode. This requires that an operator hit a ‘prior action’ but- ton to arm the system.
“Such a setup will not work with an automated system,” Wenzel continues. “In these instances, the robot will need to be inside of a guard protecting both the automation and the press. So, if the robot must be inside of the guard anyway, it often is more productive to run a faster industrial robot than the slower moving cobot.”
Robot Mode
Some newer press controls have a “robot mode” setting for automatic sin- gle-stroke mode—created specifically for automated press tending. “If the press is stopped at top, you can pene- trate the light curtain, then leave,” Wen- zel explains, “and the press will remain in automatic mode. In these cases, a cobot would be fine. But because many controls do not have this feature, stam- pers should investigate how their press control will react when automation passes through the guarding.”
One press control with this newer robot mode: Link Systems’ OmniLink 5100. “The Type 3-Robot Mode in the Link controls,” explains James Barrett, president of Link Systems, “is an auto- matic single-stroke setting that allows a robot, transfer system or other automation device to not only pass through a light curtain (configured to be muted in the upstroke) on the upstroke in the process of starting the transfer, but to also finish the transfer with the press stopped at the top of the stroke, where the light curtain may no longer be muted, provided that the automatic single-stroke run signal is
still low—without disarming the mode. If the light curtain remains interrupted when the ‘go’ signal is received, not only will the press not stroke, but auto- matic single-stroke is disarmed, and an operator must press the prior action button and hit the palm buttons to re- arm the mode after the light curtain is cleared and all other running condi- tions have been satisfied.
“This most often is used in heavily automated operations,” Barrett adds, “often in a line of presses with robotic transfers between or within the presses. For instance, we see this with large or ungainly appliance or automotive parts that might be roll- or blank-fed into the first press in a line and then under- go further operations on additional presses and/or other machines, where the best way to transfer the parts among machines is with special manip- ulators. Another typical application: a transfer system that must reach in past a light curtain used for operator pro- tection during setup or troubleshooting
operations, when the nature of the die or process results in the press having to stop at top to complete the transfer. This Robot Mode of control can elimi- nate the need for complex logic and/or interlocks to disable the curtains during automatic operation.
“We have a long history of working with complex automation,” Barrett con- cludes, “including integrations with transfer systems that let our control signal a transfer system that the press has been requested to run, letting the transfer move from a parked to ready position, and then allowing it to signal the control to actually initiate the stroke. We also have functions that allow us to work effectively in concert with safety PLCs that coordinate an entire line for fully automatic job changeover as well as line operation. While some of these functions can be accomplished using external equipment, that can increase the cost and complexity of the final solution while greatly reducing diag- nostic clarity.” MF
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