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Old 05-18-2018, 10:19 AM   #1
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Default VFD speed control from external sources

Please check the video https://youtu.be/hzpv3vIBX3Q (trim winder), we stuck at, how we can control (increase & dicrease) speed depending upon the speed at which trim is being generated by other machine (bopp slitter).??? Thanks in advance...
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Old 05-18-2018, 11:13 AM   #2
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Selectable switch using 6 presets, pot so it's variable or get fancy and mount a arm with a pot and have the winder automatically adjust speed to keep the arm in the same position.
Any vfd sales guy would probably be willing to pay you a visit to assist
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Old 05-18-2018, 11:32 AM   #3
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Any specific pot ? (I am non electronic and electrical person), here in Dubai, it's very hard to find VFD technical person who can help us. Most companies are just interested in selling off VFD and that's it...
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Old 05-18-2018, 11:36 AM   #4
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Any specific pot ? (I am non electronic and electrical person), here in Dubai, it's very hard to find VFD technical person who can help us. Most companies are just interested in selling off VFD and that's it...
Look in the manual it's normally a 10k ohm 3 wire
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Old 05-18-2018, 11:37 AM   #5
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I find it hard to believe that a auto winder wouldn't already come with speed controls built into to it.
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Old 05-18-2018, 11:53 AM   #6
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I am making it myself for the company I am working for. It's a new development. We don't have trim winder.
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Old 05-18-2018, 12:04 PM   #7
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Default Trim input

Depending on the VFD some have a second analog input called trim input. We use Parker/Eurotherm 590 drives. We use either a dancer arm with a pot or a sonic sensor for trim windup control.

If you try to just use a pot it don't run too stable, the other option is put a 1 k pot from the dancer arm in series to the main speed pots output. This way the trim pot only has 10% control.
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Old 05-18-2018, 12:24 PM   #8
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From what I saw on the video you have a moving tension arm. You need to have it actuate a trim pot to control the speed of your windup roller.
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Old 05-18-2018, 12:51 PM   #9
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Could any one suggest which pot will help me to achieve that http://pankaj.com
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Old 05-18-2018, 01:11 PM   #10
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I would think that if you are trying to replicate the machine in the video, you would need to look at what you are using to control the motor and use the pot they suggest.
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Old 05-18-2018, 02:10 PM   #11
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Working machine with VFD is ready. Only 2 issue are left to iron out. https://youtu.be/DhWyiyuAAdk 1. How to sync speed with pot, speed of which depends upon the trim (small plastic thread the man is holding) , in above reply users suggested pot with arm, that's the right solution, but still while searching net could not locate the right combination of pot and arm ..... Any help would be great...
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Old 05-18-2018, 03:41 PM   #12
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Default Standard pot

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Working machine with VFD is ready. Only 2 issue are left to iron out. https://youtu.be/DhWyiyuAAdk 1. How to sync speed with pot, speed of which depends upon the trim (small plastic thread the man is holding) , in above reply users suggested pot with arm, that's the right solution, but still while searching net could not locate the right combination of pot and arm ..... Any help would be great...
It has to be made, they don't just sell arms.
As mentioned in my other post use a 1 k pot as trim in series with wiper on main speed pot.
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Old 05-18-2018, 04:44 PM   #13
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AS I said earlier if you are using a VFD you need to see what it wants for full on and full of. Then you need to mount it where your dancer arm can be coupled to it with a small toothed belt and pulleys. It will take some trial and error to find the right combo, but that is how we do it.
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Old 05-18-2018, 06:17 PM   #14
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If you were adept at VFD programming, you could set up the VFD in Sensorless Vector Control, Torque Mode and have the VFD maintain a constant torque on the take-up roll so that as the roll diameter changes or the other machine output changes, the drive just always keeps the same tension on that take up roll regardless of the necessary speed, meaning speed will automatically adjust to whatever it takes to maintain torque.
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Old 05-18-2018, 07:05 PM   #15
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Can you set the Torque low enough to not break the film if other machine stops?
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Old 05-18-2018, 09:34 PM   #16
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Torque control will usually work unless the spindle is running really fast and the material is easy to break.

If you really need speed control based on roll diameter, both Hyde-Park and others make VERY accurate analog distance transmitters. I have used these on plastic film and paper unwind and rewind equipment.
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Old 05-19-2018, 05:46 AM   #17
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That's possibly the smallest trim winder I've ever seen.

You have two opportunities. Your dancer arm appears to go through a bushing to the interior of the gearcase. You can put a little gear on the end of that shaft and mount a rotary pot to either directly control or trim the VFD speed. That's typically how this is accomplished.

I also notice that the trim goes through a bridle ring. You could spring mount the bridle ring and put a linear encoder on it for either direct or trim VFD control.

There are a variety of ultrasonic and proximity type non-contact wind control schemes out there. I've never run across one that didn't require constant attention, so I can't recommend them.

I've only dealt with tissues, crepes, and spools of high-dollar computer contacts in terms of reeling and dereeling, so I've never had the guts to try straight torque control for this type of wind application. I've only ever done it with dancer arm control. I'm not so sure I'd be willing to try straight torque control to wind magazine paper trim.
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Old 05-19-2018, 05:51 AM   #18
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I'll happily modify one for completely automatic speed and tension control and send it back to you in exchange for an exclusive mid-atlantic US sales territory. I think I could sell the hell of of these little things.

Edit: crap, I just realized that you linked to a random video of a completed trim winder and you're just copying it. Nevermind.
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Old 05-19-2018, 05:53 AM   #19
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Can you set the Torque low enough to not break the film if other machine stops?
In my experience, not a snowball's chance in hell. The faster the speed, the longer your dancer arm/slack tower travel has to be also to allow for stopping and starting.
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Old 05-19-2018, 06:52 AM   #20
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Can you set the Torque low enough to not break the film if other machine stops?
Usually but it can often reaction rate (loop tuning) big time. Two choices to alleviate this. First program the unwinder or use inertia (free wheeling) so that the "stop" has a reasonable deceleration rate. Second option is a spring loaded idler that pulls a "loop" of material under normal operation but will spring back and offer some extra slack when needed. These can even be done with gravity (weights) which is particularly easy with horizontally oriented films or very heavy films like rubber tire plies.

When it comes to high reaction rates, two things are important. First inertia is the enemy. Trim weight down as much as possible and avoid excessive gearing but even more important is diameter of equipment. That's why servo motors even old DC systems tend to be very long and thin instead of NEMA short and fat. Second loop tuning is critical. If you can do it you are really better off with an engineered system...someone skilled in electromechanical design calculates the speeds, inertia, torqued, acceleration, and calculates loop parameters. This side of things has gotten so routine that some servo companies have software to do it.

One final item is that you can do other things to help yourself. If you expect the winder to do everything there are limits to what it cn do. If you can help it out by slowing down the unwinder it really helps a lot. Ultimately if you do speed control either by pulling the film and the unwinding spool just floats I've seen some of the simplest tension regulators like using a motor that is basically "underpowered" with a NEMA design D design (a tension motor) that just holds tension on the film and consistently spools everything with no VFDs involved at all. Some large paper machines like on calendars use two VFDs too. At the start the winder uses speed control and the unwinder uses tension control to maintain tension since at very high speeds the winder has very little control. At the halfway point they switch and the unwinder uses speed control while the winder uses tension control. You can do both but be aware that having two loops controlling the same thing can cause headaches with loop interactions...the safest approach is either/or. Either way this version gives the best compromise in terms of both speed and tension control. It's a little strange thinking things backwards until you realize it's a push-pull system.


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