Today is...
Monday, July 22, 2019
Welcome to Control.com, the global online
community of automation professionals.
Featured Video...
Featured Video
Watch an animation of a conveyor stacking operation demonstrating the use of a move on a gear command.
Our Advertisers
Help keep our servers running...
Patronize our advertisers!
Visit our Post Archive
Anti-Repeat and Anti-Tie Down Press Control
Adding anti-repeat and anti-tie down control to old mechanical stamping press without angle feedback.

I have a very old mechanical stamping press here that was only used for die tryout for the longest time, and now they want to use it for minor production jobs. In order to bring it up to code though, it must have anti-repeat and anti-tie down capabilities.

I have a 2 button palm station and both must be active to actuate the dual safety valves. But as of now, you can hold the buttons down and cycle in continuous as there is no angle feedback of any kind.

I was hoping someone might have a suggestion on a cheaper alternative to completely updating everything to achieve this though. If I have to have a cam switch or resolver/encoder setup, it will take some engineering as there is no location for either currently. Would limit switches be viable for location to force stops at top dead center for anti-repeat? Timers for anti-tie down?

I know what's required as far as operations and dual channel safety. I just don't know what's allowable in components used to achieve it.

By Robert Scott on 24 October, 2018 - 6:27 pm

As I understand it, anti tie-down means two handed operation will not operate a second cycle if only one of the controls is released and pressed again and the other control remains pressed the whole time. Anti-repeat means that when both controls are held, the cycle should not start a second time. One way to implement both is to process both controls through a timer that turns the activation of the control into a "one-shot" that goes inactive shortly after it is activated, even if the control remains pressed. Then simply require the simultaneous presence of both "one-shot" outputs to start a cycle.

If you also need the two-handed control to abort the cycle if either control is lifted during the cycle, use the raw control states. If the "AND" of both controls goes false, perform the cycle abort.