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Old April 30th, 2014, 11:09 AM   #1
BTunnicliff
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Tension Control in Compact Logix

Hello All,

I am fairly new to programming ladder logic in general and I am looking for a little nudge in the right direction. To give a quick background I have an ME background and just started writing PLC programming for this new company so I have experience with only writing code for one small slitter/rewinder (Thin plastic sheeting).

To give a quick rundown of the project I am working on. The system I am currently working on is a 1769-L33ER AB compact logix controller. I am using the most current version of Studio 5000. The system I am working with is a turret winder that is running thin plastic sheeting, .5 -5 mil. This has a top and bottom turret that will be running at the same time.

My responsibilities: The main speed of the machine will be determined upstream of my program from the main nip drive. I will be able to see this speed but I will not be controlling it. So the rewind portion of this machine has a dancer roller for trimming speed to the rewind shaft. This is supposed to help maintain my tension for my material.

My Questions: On my first slitter/rewinder that I programmed I only controlled the tension with the pressure of the dancer roller, and all the speed matching was done outside of the PLC. (Explained to me buy our electrical guru here: Main nip speed voltage is trimmed by the dancer position which then gives the rewind spindle speed that it should be running. As the roll grows the spindle must slow down to maintain constant line speed.)

So now I want to be able to do this all in the PLC because there are times that I need to give the rewind spindle a different signal than the dancer position. I.E. During turret cutover the empty spindle must be run at line speed which will be different from an empty core, 3.5" OD, to a full roll of 24" OD.

I have looked a lot on this forum for tension control theory and learned a lot, but I am just getting stuck on how to write the actual logic. If anybody has any sample code they don't mind sharing with me it might be able to help me over this hump.

I know this is very long winded, but if anybody can help it would be much appreciated. Please if I am not clear on my description of the system ask me for clarification.

-Brian
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Old April 30th, 2014, 11:23 AM   #2
JRW
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how are you calculating diameter?
or how do you plan to?
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Old April 30th, 2014, 11:27 AM   #3
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I was either going to use the speed of the main nip and the RPM of the rewind spindle to calculate the diameter with math. OR I will be using the the layon roller positioning to know the diameter of the growing roll. I have concerns with both so I am not sure which is best practice. I tried to pitch the ultrasonic sensor to my boss but they did not go for it.
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Old April 30th, 2014, 11:33 AM   #4
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Here is a common block diagram- I don't work with AB products so I cant help with the code- I'm sure others will chime in
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File Type: jpg winder bd.jpg (53.5 KB, 254 views)
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Old April 30th, 2014, 11:36 AM   #5
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Winder Calculation- one of several ways to do it
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File Type: jpg winder dia calc.jpg (36.0 KB, 248 views)
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Old April 30th, 2014, 11:39 AM   #6
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You will definitely need some decent filter blocks
The position controller in post 4 is really a PI controller. Just use a +-10% trim
The diameter calculation does most of the control

Maybe this will give you some ideas
Good luck

Last edited by JRW; April 30th, 2014 at 11:41 AM.
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Old April 30th, 2014, 11:46 AM   #7
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I spoke with somebody who wrote code for an existing winder and it sounded like that's why they use the layon roller position for the diameter rather then calculating it. But then sometimes we run film with the layon roller out of the way and we won't know anything about the diameter.
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Old April 30th, 2014, 11:55 AM   #8
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JRW thank you for some good ideas.
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Old April 30th, 2014, 01:59 PM   #9
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Does anybody having any specific code setup with PID loops for tension control?
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Old April 30th, 2014, 08:29 PM   #10
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Quote:
Originally Posted by BTunnicliff View Post
Does anybody having any specific code setup with PID loops for tension control?
I would suggest you post what you have done so far for people in here to help and give many suggestions. If you are looking for someone to send their whole winding tension control program I don't think you are going to get the response you are looking for.
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Old May 1st, 2014, 11:23 AM   #11
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Thanks for the advice. Unfortunately I am running out of time and I think this is a little too far over my head for a second project. I am going to let my electrical guy wire up the drives and tension outside of the PLC like he normally does. I will then use a relay to control the signal to switch from the dancer signal controlling the rewind spindle that has material on it, to the PLC telling the empty spindle to run at line speed during the cutover process. This will then switch back to dancer control after the cutover.

Anybody see any major issue with the concept?
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Old May 1st, 2014, 11:33 AM   #12
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What brand of drives are you using?
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Old May 1st, 2014, 11:43 AM   #13
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These are Allen Bradley 5HP Power Flex AC Drives
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Old May 2nd, 2014, 10:44 AM   #14
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www ab com/linked/drives/drvappsw/files/AppModl_Center_Winder/9329-RM002B-EN-E.pdf

literature rockwellautomation com/idc/groups/literature/documents/rm/9329-rm003_-en-e.pdf
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Old May 4th, 2014, 10:06 AM   #15
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You should look into your power flex, it has it's own trim PID for a winder application, real simple to set up. Parameters 130-139. They explain it in the manual "apppendix F".
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