Programming for a Punch Press

[ataslaki]

Hello all,

Similar to a previous post here, I have an obsolete SYSMAC (Omron) PLC from the late 80's on a brake and clucth operated punch press (25 TON).

I have vast experience in programming PLCs, but haven't done any programs for punch presses. As part of preventive maintenance I'm being proactive and would like to replace this obsolete PLC with a current one (either AB or Mitsu).

For a punch press which basically operates up and down, with anti-tie-down push bottons, stop-on-top, single cycle, etc. it's a fairly easy job to program.

My question is where should I look for any regulatory issues regarding punch presses.

Has anyone programmed a punch press before? Any guidelines?

Thanks

 

[jonesy29847]

Well you can start with ANSI B11.1, B11.19, NFPA 79, 70E, CFR1910..... There are a lot of standards out there. I would advise that you contact a firm familiar with Press retrofits. I think AB has a clutch/brake monitor already done, let them assume liability.

The monitoring circuits are critical.

Good luck.

 

[mc5w]

To meet OSHA regulations you need to use a dual channel PLC that has 2 CPUs checking each other, dual channel power supplies and so forth. It also has to certified for use with hazardous machines.

There are a number of possible PLC failure modes:

1. CPU bets into an endless loop or a deadlock a.k.a. dreadlock a.k.a. wedged.

2. There is a way for any power supply regulator to break so as to supply excess voltage. When that happens all of the outputs will jam on.

There is a company in Nashvill, Tennessee named Link Electric & Safety Control that has a PLC based punch press controller that meets all OSHA requirements for failsafes and so forth. This also has a small built-in programmable limit switch for driving press feeders, parts ejectors, and so forth.

There are probably some other companies that also do this. You do not want to do this on your own unless you are a super expert. Even then you are reinventing the wheel and you probably are better off to buy an off the shelf controller.

Mike Cole, mc5w at earthlink dot net

 

[OldPfart]

I have never heard of having to use hot standby PLCs on a punch press. That is ridiculous really. And I thought our regulations in Ozz were tough.

I normally use a standard Omron CS1 PLC with a rack mounted IEC type 4 safety relay on board. It monitors 2 input circuits, dual contactors etc etc and is normally more than adequate. This is for crane usage (BMU).

Why change PLC? Mitsu PLCs and software are really pretty basic and not very friendly. AB are OK but their software is not that good and VERY EXPENSIVE!!!! The reports I see around the web sites about RSLogix locking out other brands of software from communicating, and even other AB software locking AB software, really makes me wonder. I do use them when required but not by choice.

Omron CX-Programmer software programs every PLC in the range and is inexpensive. Not like many others. The latest version, V5, has FB and STL if you require it. The CJ1 PLC is AWESOME, right through from a basic CPU with 160 I/O to many thousands. Even the bottom end processor allows as many Device Net I/O blocks as the high end processor, just rack mounted I/O is limited. 64 bit and floating point maths too! 64 bit I/O cards and only about the size of a cigarette packet - no rack, just mount to DIN rail.

If you require hot standby, and the existing PLC is a C200H or C200HS, you can obtain a CS1 hot standby PLC, or standard PLC, and re-use the C200H I/O cards. They will fit in the new rack without modification.

 

[ataslaki]

I am getting petrified reading some of the postings, not for the change, but for what we have today in our punch presses. Doesn't matter that it's an old OMRON (very reliable by the way), but for being a single CPU PLC with absolutely no safety relays!

Of course, as I'm planning to replace the PLC, simply because it's outdated and I'm afraid it will just stop working one day, I do certainly want to think safety FIRST and put a better system together.

I do have an electrical consultant (an Engineer) for proper wiring, etc., but I'm the programmer of the PCLs, and now you've opened my eyes and I need to look further into this before proceeding.

Thanks all. Any more suggestions are still welcome.

 

[dazmac]

I have done several punch (blanking, continuous feed) presses in the UK - using only one PLC, but as a must a double circuit safety relay. Had several inspections from regulatory bodies, never any questions - mos tof these presses were converted from relay logic, there was much more danger there of relay latching than with PLC's and transistor outputs

 

[darrenjm]

you didnt say what area you are in...this depends on the codes for it..If you are in canada i wouldnt mess with it..codes here require double redundant processors as has been said..if you live in the states.."step away from the project" With the law suits down there i wouldnt touch one with a 10' barge pole..There is quite a few resorses as well as people who are experiansed with this type of control..make freinds and use a sub contractor if you have to..

Bottom line..check local codes..(as well as your insurance provider!)