What would you do?

Ok guys,I know there are a lot of very experienced people here and I would like to know what you think would be the best way to accomplish a project one of the ME's put to me today. I told him to give me a day or two to try to give him a game plan. Let me give you as much information as I can: We have an assembly line that has 3 different SLC 5/04 and 3 PV600's. It has one plc that controls traffic, pallet stops releases, and downstreams. When it was built I believe that everything was manual assembly and palm buttons used to trigger the pallet release. Then as time went by they added an automatic test station with its own plc,panelview and pallet stop and release. Then as more time went on a vision station was added with its own panelview, pallet stop and release. We have also added more cameras to the vision system, and a pick and place so no one has to unload the line now. This line has been modified a lot. It is greasy and dirty, wire and cable labels are faded, tie-wraps abound just trying to hold everything up out of the way, we are talking total nightmare. It is about 24 feet long. We have cabinets with plcs on both ends, one is about 6 inches off the floor underneath an operators feet. That is why I networked them so I don't have to be under the operator! Now for the project this fella wants my input on...he wants to clean it up! One plc controlling it all. Reroute all the cables, make everything nice and neat. My problem is that if I put a new cabinet at one end, none of my cables will reach from the other end. The machine runs 7 days a week and has for 2 years, so time is limited. What would be the best way to integrate all 3 plcs? Or does it sound like we are borrowing trouble? It would be nice to go out to the line and hook up to one plc and be able to make changes on any station. Plus some of our maintenance folks get a little confused on how to hook up and pick the correct node. This would eliminate that problem. What do you guys think, should I leave well enough alone or jump on this as a great improvement opportunity?
Thanks,

Lori

LStewart said:

he wants to clean it up! One plc controlling it all.

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Why? Will there be some return on the investment of time, energy, and materials?

With a line running 7 days a week I'd leave it until there is a real reason. Like a retool for a new or updated product. There will be downtime on big changes and I'd be surprised if management would accept it.

I would definitely go for it, but pre-plan as MUCH as possible before touching a thing! Can you reuse the existing enclosures as junction boxes? Buy a replacement inner panel and install terminal strip(s) for all the connections. then just run multi-conductor cable and/or hard pipe back to the new cabinet.

Programming is another issue. Are you confident that you can write a new program from scratch to duplicate what the separate processors are currently doing?...

Here's one thought as a backup plan...

Make a copy of all 3 existing programs. In the copy, remap the I/O to reflect the new locations. Then, set aside 3 blocks of internal memory points (bits, words, etc.) for each program. Also, assign each a 'block' of subroutines (assuming you're using more than 1 in each). For example, lets assume each program used subroutines 2 thru 10. In you 'assignment list', assign subroutines 12 thru 20 for program 1, subroutine 22 thru 30 for program 2, and subroutines 22 thru 30 for program 3. Now, remap all the internal points to use the new points and subroutines allocated for that program.

At this point, you will still have 3 programs that DO work, but they don't share any memory locations. You can now safely put all 3 programs in the new processor. In LAD 2, put 3 uncondition JSR instructions pointing to subroutines 12, 22, and 32 (the 3 old 'main' subroutines).

Yes, it would be a lot of work, but it will CYA if your 'from scratch' program doesn't work. It will also buy you time if the rewiring part of the job eats into your debugging time... :nodi:



-Eric

Have you done an I/O count to see if all the I/O will fit into a single racks worth of modules?

On the hardware side, one thing you may be able to do is go ControlNet between the existing racks. Remove the SLC processors in the two 'remote' racks and replace them with 1747-ACN15 adapters. Then put a 1746-SCN card in the rack with the remaining plc. No rewiring from cabinet to cabinet required. Use Eric's plan with the program layout and remap the I/O as needed from the SCN card. This will (may?) have a higher up-front cost in parts but will save you quite a bit of install time when the machine is down.

This all assumes that a single SLC will be able to handle the increased processor load. You may be looking at CompactLogix for the processoer, which wouldn't be real bad either.

This is certainly do-able. But as jstolaruk said, make sure you know what this gets you before you jump in and do it. Doing projects for the fun and learning isn't all bad but go in with your eyes open about the cost/benefit.
Keith

I have converted multiple racks of relays and miles of wire in a single plc and also multiple plc controlled machines.

Which is better? Depends on personal preferences. I do not like PC control, and also am not a big fan of ControLogix or any distributed control.

Many machines that I have dealt with wind up with two cabinets with a PLC in one and a remote rack in the other. I am very fond of this in large applications. On some machines, I have used several "micros", each with its own zone to control. A few years down the road, many of these machines are disassembled, and pieces scattered about, often as operating units with what the particular zone did originally.

I would probably do a long term phase out and upgrade. Doing one section at a time, each with it's own plc. Normally doing the upgrade during a shutdown or holiday. It may take a year or two or three to complete.

Old graesey wiring and who knows what else are often better off left alone, as they become flaky when messing with them. HOWEVER, trying to troubleshoot the mess can be even worse, not counting downtime. If the hired help turns to you to guess what is wrong, make it easy on yourself.

If you have the option, pick a PLC that you like. If you do it in sections, try to make them all the same. If using a rack, standardize on cards if possible. I like 16 point input cards, either 120vac or 24vdc "positive"logic. I use 8 point relay output cards when possible.

If I have the choice on a really large machine, then it is one or two racks of GE Fanuc 9030's. I did use a 9030 with less then 10 total I/O one time, becuase the company wanted to hook the PLC up to the mainframe. Processor cost around $3400 for what a $250 micro could have done, without the ethernet connection.

On really small machines, I prefer the GE Fanuc micros, or the Entertron SmartPak series. both have good FREE tech support available.

On a midsize machine, i would lookto GE for their new 64 point micro or Entertron to their SK1600 or Elite 20000 series.

IF you are comfortable with the AB units, and have the budget, run with them. I would get the cabinets built up and tested in advance, maybe even a wiring harness made up too.

All in all, planning, planning, planning!

best regards.....casey

Thanks for your replies. I don't know why they want to do this. It runs, and we don't have a WHOLE lot of trouble out of it. It just looks like ****! I know we are trying to get new contracts and I think a lot of it is aesthetics to impress potential business.

Eric, what you came up with is what I had been thinking about. I also have 3 panelviews that will have to be reprogrammed to accomodate the changes. But I don't want to use any of the enclosures they all are too small to contain everything. I would have to go to a larger one.
We have the the 8 point input boxes that have the color-coded conductors, and we could reuse these. I think Turck makes the boxes that have a molded connector that can be connected to an extention to reach the distance from one end of the line to the other. Matter of fact with the exception of maybe a couple of switches and the vision I/O I think all of the switches are plugged into these. I know one thing for sure, its going to be one hell of a job if they decide to do it. I would like to see it done, but I really don't see them doing it when they get the price on what this is going to cost in just labor. I know my "coordinator" got a really wierd panicky look on his face today when he heard about this. The more I think about it, I am getting the same look.
Thank Ya'll
Lori

LStewart said:

But I don't want to use any of the enclosures they all are too small to contain everything. I would have to go to a larger one.

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I would definitely add a NEW enclosure for the new PLC. I was only thinking to reuse the old enclosures as junction boxes. They will only contain terminal strips, so they're plenty large for that.

The multiport connectors are a nice addition, but I wouldn't use long extension cables to connect them back to the new enclosure. I'd prefer to see them go to a local J-box that is piped back to the new enclosure to protect the wiring.



-Eric

Well I want to thank you for the input. The "powers that BE" have decided that we will just add duct work and tidy up that way for the time being. The engineer had no idea just how much work and money this would involve. He just had to be enlightened!! Have a nice day!
Thanks,
Lori

I would replace all the SLC 5/04s with one RX3i.
Yep, that's what I would do.

Two words:

Device Net.

Alaric said:

Two words:

Device Net.

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Actually its one word if you are refering to the "open low-level network that provides connections between simple industrial devices."

Or three words, if you are referring to what one would catch falling vices in.

RussB said:

I would replace all the SLC 5/04s with one RX3i.
Yep, that's what I would do.

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Russ hs some words of wisdom there. I still live in the dark ages, when the 9030 reigned supreme, well, at least in some neighbor hoods. I do a lot of 9030's becuase most of the time, the customer has two or three old machines sitting out back, and that is the parts depot.

Most of the time, I don't even remember the RX3/RX7 series. Sort of isolated here in the middle of nowhere from a good GE Distributor, or any distributor for that matter.

Now in central Michigan, there is a GREAT GE Distributor!

It's a shame Illinois was annexed by Chicago...

regards.....casey