Press control

[Guest Len W.]

Has anyone out there had experience with using redundant PLC's to control industrial presses? By redundant, I mean a second unit to serve as a watchdog for the actions of the first in order to comply with ANSI design safety specs.

[Guest Guest]

There are a few vendors that make this type of system. We have a few made by Link Systems. They are not actually PLC's, they are control reliable (redundant) processors that have the logic programmed and protected by the vendor. You can not edit this logic. They have built in brake monitoring and control reliable run button control. The link system has proven to be reliable. I have no experience with the others. I had an AB integrater quote a system for an 800 ton press, they seem to be the more expensive. The other that I am aware of is Honeywell's Wintriss Systems. Check out their web sites, they all have literature for download.

[silva.foxx 0]

What do you want to know? I think you use Status bits of the duty PLC to trigger the redundant PLC using a network link.

[silva.foxx 0]

The redundant PLCs inputs/outputs and programme would be the same so both recieving the same input and output images. The redundant PLC will inhibit its outputs until a fault status bit of the duty PLC is sensed. What do you think? I am intereseted in learning more on redundancy - look what you've started now.

[Camel 1]

We have 10 presses. Can you give some specifics? It has been my experience that the feed system is extremely hard to control but the press itself is easy.

[Guest rammin48]

I have done several redundant plc setups and it is not very hard. There are limitations My experience is primarily using slc500. The limitations is the data that needs to be transfered between plc. They share hardware through remote I/o and scanner modules so I/O is not a problem. I have done one using GE 9030 and the Maxon software.

[Guest Len Wilson]

I have considered using a "networked" set of dual PLC's as a self-checking system. In my opinion, this would be a reasonable way of providing safe redundancy. Other features that provide a measure of safety are dual clutch output/inputs that we already use. However, what I'm struggling with is trying to meet ANSI recommendations for punch press control. Ansi B11.1.e.1-4 states that "dual" microprocessor logic systems should be provided identical (though electrically isolated) input information related to clutch /brake function. 5. Each logic system has to monitor the other. If I interpret this correctly, it means that I have to bring a separate set of of mode (single, inch, cont), initiation (palm switch) switch inputs and cam inputs to each processor rather than relying upon a network to transfer the information back and forth. Of course, this means either adding cam switches or hopefully having enough contacts on the press to do this without purchasing a new cam box. It would be like wiring a punch press twice. Do the new "purchased" press control systems require that?

[Guest Ed]

ANSI B111 spec states that if a PLC controls / monitors a press system (clutch brake and cams) that the system has to be redundant in design. I've used Allen Bradley's clutch / brake controllers on all of the systems that I've ever worked on. Whether its the SLC500 Modular chassis, 1746, Micro and now even Flexlogix clutch brake.