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kcor

multiple motor control with ab plc

22 posts in this topic

Have a application that I hope that someone on this site may have already have some experience with and could give me some advice, since I am not exactly sure the best way to go about it at the moment. will try to describe what I am looking at trying to posssibly do. Have a roll of fabric that is about 3 feet wide that will be feeding through a chamber with a combination of multiple motors and rollers. As the fabric feeds through the chamber, steam is injected into the chamber. This will cause the fabric to also shrink as it goes through the chamber. Before the fabric is fed through the chamber, it is sprayed with a finish material. At the moment, it appears that it will be a total of 4 motors used, that will be evenly spaced apart in order to allow the fabric to be in the steam chamber for a certain amount of time ( all of that has not been determined yet) Here is where I am confused. What would be the best type of motor that anyone who has ever done anything similar to this would be the best to use, a ac inverter, or servo, or dc motor. Also, any advice on how to use the master motor that is running, and then how to use that speed to determine what speed the other motors should run at in order to maintain the desired feeding of the fabric, which will shrink about 8-10 percent as it goes through the chamber. It appears to me that the first motor would have to run at a certain speed, and then due to fact that fabric shrinks, the other motors may have to run at a different speed. What I have thought about is 4 seperate AC Drive motors, and using a micrologix 1200 or a slc 500 plc, use a operator screen to set the speed that you want to run the master motor by using a analog output. Then also set the speed of each of the other motors using analog outputs for the plc as well. Any advice on how to use the operator screen and set the speed of the master motor, and then the other motors speed be automatically adjusted would be greatly appreciated. At the moment, the only way I can think of doing it, is to set the speed for each individual motor seperately. Hope I have been able to explain it clear enough. I will attach a quick sketch I made for reference as well. Thanks alot feed_motors.pdf

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I do something similar to your application. I form & weld a continuous seamed metal tube using 8 AC motors driven by GV3000 motor drives. I don't have a PLC on this machine (and wish I did), so I use an old master speed controller (aka big potentiometer) that governs the maximum speed of all the drives. Then there are small potentiometers at each drive to fine tune the final speed. You can read about it here. If I had a PLC, I would use one analog output as the master max speed control and still keep the small potentiometers at the drives. Then all the motors will speed up & slow down together and in tension, but small speed changes can be made on-the-fly. The roll diameter varies so much and we use a handheld tach during setup, so potentiometers within reach of each measuring point work nicely for me. Will you have an encoder that reads the speed of the fabric at each motor? If you do, then you might be able to use indiviual analog outputs to each drive and set the speed from the HMI. Let us know what you choose & how it works.

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The encoder by far would help allot....You can use the encoder feedback as your Process Variable signal back to the PLC...Now here's is where you can go crazy!!! The PV values can be used to program 3 PID loops...PV value = the encoders (Feedback), the CV - COntrol Variable = the VFD's (AC drives) and then SP - Setpoint entered through the HMI..... One of the Loops can be the master of the other 2 slave loops...Lots of examples online...just a suggestion.. Edited by jimdi4

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Thanks alot for all of the advice. This is something that is still in the beginning stage at the moment. As soon as I find out more info will post on here for advice. Did have a Allen Bradley Drives Salesman in this morning, who was showing me the advantages of using control logix. Pretty pricey way to do it, but seems like a very good package for motion control. Right now, I am going to look at putting some quick controls on a prototype that we will be building. Looking at using a powerflex drive and having a total of 4 drives for 4 motors, then set the speed independant on each drive to get the desired feeding of the fabric. Then use a master type pot to adjust the speed on all of the drives. In other words, when I adjust the pot, all of the drives will change the same amount. Do not have any drives yet, but looking at the ab powerflex, the local ab rep is good to work with. Any advice on how to connect the 4 drives together and then use some type of display such as a redlion or something similar to show the speed that each motor is running. thanks

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Am I missing something here normally I would be pulling a fabric through a chamber supported on freewheeling rollers and the tension being controlled from a braked let off why would you need 4 drives also if you do need 4 drives I would not assume that the shrinkage would be the same at all speeds of the master because the heat history of the fabric would be different. Don't know about AB drives but Telemecanique can have remote displays connected easily to the drives through standard ethernet patch cable would then go with previous suggestion of pot below each display

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I work in the carpet industry, and we use something in our dying process that sounds similar to what you are describing. Ours however sets the dye in the carpet. In this four loop box, how much material do you plan to run thru. Our steamers are set up with drive rollers at the top of the box, about 20 foot down, we have a trim roller, which works off a pivot, some paces use load cell. If using the pivot type trim roller, a potentiometer or inclinometer is attached to the pivot point to send an analog signal indicating position. This also provides a tension control The first roller is set as the master drive, this speed signal is sent to all the drives as the master reference, the analog position sensor is either scaled in the PLC to add or subtract from the master reference, or the logic can be done in the drive thru PI control or signal trim if the drive is capable. It is however better to go thru the PLC if you want to display speed of each drive on some sort of HMI. I hope I have explained this in a way that it is easy enough to understand. If the description is not good enough you can probably go to KUSTERS or TUFTCO website to maybe view an example of what I am trying to explain.

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thanks actually, the plan is to have a total of 12 rollers across the top, and 12 across the bottom. there will be a total of 4 motors that control the top 12 rollers, ( 3 rollers per motor ) at the exit end of the chamber is a edge guide motor system that will be pull the fabric and on the extra of the chamber will be another edge guide system that will be pulling the fabric from the main roll and assisting at feeding it through the steam chamber. The edge guide motor on the exit end of the steam chamber will be master motor. It will run at a certain speed, such as 3 yards per minute. Then the 4 motors in the steam chamber as well as the other edge guide motor will be set up as slave motors to maitain the speed of the fabric through the steam chamber. the fabric will be sprayed with dye as it enters the steam chamber, and the spray nozzles will then have to spray the dye to match the speed that the fabric is being pulled through the steam chamber. the fabric actually shrinks from about 8-12 percent as it travels through the steam chamber, so the use of all of the motors and rollers is to ensure that there are no wrinkles or stretching of the material or it will ruin the fabric as the dye is set with the steam. have not done any type of projects where one motor is set as a master and the others are slaved to it, and due to the way the company I work for has downsized and changed, no longer have the extra cash flow to possibly try something, now you have to order what you know will work and make it work. as you know, sometimes that is easier said than done, at least for some of us. but i have found from using this site that there is always someone who has more experience at something you may be trying to do, so any advice would be greatly appreciated. one thing that I was wondering about was using ab ultra 3000 servo motors and a slc 505 and connect the motors through a ethernet or devicenet type network and in the plc use the ethernet message type commands and pull in the speed that the master is running and then use that to control the speed the slaves are running. This is something that is all new to me, trying to read up on as much as possible, but if anyone would be willing to share some advice or possibly a sample would be appreciated. thanks

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Lots of different ways you could do what you want. The main thing I see you need to figure out is how precise your controls need to be. As others have stated speed is going to have an effect on shrinkage. This being said the easiest method would be a Mater Pot with each drive having its own trim pot. PLC not needed Downside to easiest is now setup is open to interpetation...IE good operator good run, bad operator bad... well you get the picture. Little up the ladder on complexity... Use a PLC with analog outputs to control the drives. Each drive is driven by an analog input from the PLC that tells it what speed to run... Downside Open Loop control. as load varies you will have to trim each of the following drives. Upside is now you can create recipies and based on what speed your master drive is set to run the others get there speed comand based on it. Futher up....Closed loop drive control( some form of feedback) What ever formula you come up with you can use that with your feedback to keep system stable. Downside Feedback device has to be purchased and intergrated into system. You have to come up with a formula to control the system. Upside this will be your most precise method. At the end of the day. How accurate do you need to be and how good will your operators be at controling the system. Once you have that figured out the hardware side should be easy. FYI... AB drives are good...but in my experience I can get other brand drives that do the same job cheaper.

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You would regret doing this for a long time. The programming and poor performance would be a never-ending headache. If the system warrants the use of servo motors, don't try to cut corners. Use ControlLogix and the appropriate drives (Ultra 3K, Kinetix). As Clay B has said, if you want to minimise wastage, set-up time, and inconsistencies in the end product, then you should aim for a closed-loop system. The feedback most likely should be web tension. The master for the line should be the section with the highest inertia - i.e. the least responsive to changes in commanded speed. Other sections would then be able to follow easily. Most likely AC drives and standard motors are adequate for the job, but sensorless vector mode may not be - get the motors with encoders installed. I would again recommend ControlLogix and use the function block editor for the line control. CLX with Powerflex drives on ethernet would make a neat, powerful package. Regardless of what drives/motors you use, the most important initial step in the design is to size them correctly for the application. Don't guess - if you are unsure, get your drives supplier to do the analysis.

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Edited by comeng

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thanks to everyone. Man, this site is great. To be honest, I have done quite a few projects the last couple of years using the micrologix 1200. Have done a couple of servo projects using a baldor drive that was set up with move profiles in the drive, and then I used the plc to turn on the correct output to move to the desired position. I have no experience with controllogix, some with the slc500. Have a meeting tomorrow with my local ab rep, who is very good and they are going to have a ab control guy with them. I spoke with him over the phone and he was talking about either using the slc500 as I described earlier, or going with controllogix and the ultra servo. The way he described the controllogix and the ultra seems like the way to go. Will hopefully learn a little more tommorw. The only bad thing is that we have rslogixs 500, so it would mean buying the software and trying to become familiar with it. Also, a lot of the mechanics is still in the planning stages, but the way it usually happens, is they have a plan for the mechanics and then expect the controls to be ready in a couple of days. Thats why I am glad there are folks on this site who are willing to always give advice. One thing I was thinking about doing for a quick demo, was ordering some powerflex70 drives and somehow connect them so that one is a master and the others are the slave. Downloaded the manual this afternoon, plan on reading it tonight. As far as other drives etc., it has to be AB. Every piece of equipment in the country it will be goin in, is AB, so everything will be AB

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Use one Motor (Exit Motor) as speed master (Reference) Setup all other motors as tension control (Not speed control) Powerflex. Install motor with all wheels and pulleys connected, Preform a Auto Tune so drive loads all inertia compensations into drive. Then you only need to set tension required to tension motors Send speed required to Speed master motor Motor start signal to all drives at same time Delay flux off to drives (2 minutes) so good responce in jog control

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I would make the first roll the master and gear the rest to the master with a torque or tension override. The down stream motors should rotate slower than the first ( master ). If the motor is torque control only then it will spin like crazy when there is no load ( no material ).

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I've seen some GE 3000 series drives that would do what is being described. Master reference and torque arm for fine tune without a PLC.

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thanks but everything will be allen bradley. Even if for some reason, I wanted to use something else, the new director of our company said everything from now on will be allen bradley, so allen bradley it is. Have no problem with that, actually is now my favorite. Now have another question that I hope someone might be able to answer. Now the new boss has come in to a meeting today and said that he wants me to build the controls to control six motors for a prototype chamber that I have been talking about in this post, and now the whole thing has changed. Will now need to take the first motor driving the fabric as it enters the chamber and use this as a master and use feedback from a encoder that shows what this motor is turning to then send a analog signal out to the other motors to make them run the same speed as the master. Wants us to use the new micrologix 1100, feed a encoder from the master with the encoder mounted on the shaft of the roller to show the actual rpm of the shaft and then use this to control the analog out to the other 5 drives. The only thing that I know for certain at this moment in the project is that the motor for the master will be geared to turn a drive roller that is 2 inch in diameter. What would be the best way to take the encoder input which will be a 360 pulse per revolution and use that number to tell how many yards per minute of fabric is being fed. Any advice would be appreciated. thanks

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I think you need to pause and think about the mechanics here, firstly the fabric must be coming in roll form therefore will have to sit in some sort of let off device which may or may not be driven if it is not driven (or braked) then somewhere along the route something must be pulling either a nip between a drive and idler roller or the windup of the material. If you have neither a nip nor a windup then you are only driving the fabric via the friction of the rollers to the fabric when I have tried this before I have found the drives have to run faster than you would calculate the line speed simply to produce the frictional effect Unless the first drive roller you are talking about is a nip roller how do you know the fabric is travelling at the same speed as the roller You need to establish what is ultimately controlling the line speed and use this as your master

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With the tension control you also would need to set speed limits based off the Master. This stops the drives from running away if the no load ever happened. But now you are not going that way. If you can communicate to the drives using ethernet, you could: Encode connected to drive. Drive calulating encoder speed This speed reference sent to other drives via Ethernet Encoders don't need to be connected to PLC, only to the Drives

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Thanks to everyone for your advice. Here is what we have got to make happen. There is a master motor that I will call a nip roller motor that is going to be the master to the first motor entering the chamber. I considered installing a powerflex drive on this and use the analog output from the drive to tell me the speed the motor was running, but boss says no, this is what he wants done. 1. Nip roller motor be master - encoder installed on 2 inch diameter roller being used to feed fabric - use encoder to determine speed this motor is turning. 2. This be the master for the 1st motor entering the chamber. The first motor entering the chamber will have encoder installed on one of the 2 inch diameter rollers that it will be feeding as well to tell the exact speed it is running 3. The other motors in the chamber will be slaved to the first motor entering the chamber. They will each need to also capable of being fine adjusted from a panelview micro display. I downloaded a file from the ab knowledge base on how to use the hsc to determine rate. It works as it should. I used a cordless drill with a hand held tack on the head of the drill to compare what it said and the plc said was the speed, and it was the same. Where I am confused at, is how to capture the speed. The routine that I got from the knowledgebase will show the rate, but once the motor stops, as expected, the rate will go to zero. I have attached a couple of files that I have been working with as time allows. In the plc program in lad 4 is the routine that i got from the knowledgebase, it is based on setting up a STI If someone could assit me with how I can capture the value in the HSC and know what the speed was running before the motor stopped, It would be greatly appreciated. I must be making this more complicated that it should be, but have just went brain dead on how to save that value. I thought about moving the value in the L9 to another L location, but when the HSC goes to zero, when the motor stops, just can not figure out a good way to capture that value to use as reference. I also attached the panelview program, but the only screen I am using is screen 1. Any advice would be greatly appreciate. I hope i have been able to explain this where it makes sense. Thanks SPEED_YPM_TRY2.RSS speed_rpm_try2.PVA

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