Unwinder Coater Rewinder

Hello Folks,

This is the design idea of a hydrogel coater that I am working on.
Unwind>>Coat hydrogel>>Rewind

Spces:
300mm wide web.
6000mm machine length - can be upto 7000mm.
400mm dia max roll
40 kilos max roll weight
Hydrogel is very sticky and must be laminated both sides with siliconised liners (as shown)

There is plenty of good advise available on the forum and I wanted to share my plans so that your experience adds value to my project and help me in clearing my doubts

1. Unwind VFD in speed mode as line speed (max 10m/min min 1m/min) is process critical.
2. Rewind VFD in Speed mode(? or Torque mode?) with torque limits and taper tension option.
3. Ultrasonic diameter sensor to monitor UW and RW roll diameters and thereby control line speeds.

Queries:
aa)How to drive the Chill roll? the nip of the chill roll and the LDPE is important as that would push-out air and give a neat apperance with no bubbles. This will affect the tension zone as well?
bb) Should I incorporate a load cell? I was hoping that the idler at 6'O clock position of chill roll is a good location as it gives max wrap.
cc) Encoder position at exit of chill bed will serve well?
dd) Should the mesh roll and LDPE roll work on just pneumatic dancers and EM brakes? Will this suffice?

I am more into ladder logic of pneumatic and pick-and-place applications why was confused with so many varied options out there.

Omron claim to have ready made package for this application but the sales engineer who visited me was unsure of the mods that I needed - attached is their datasheet showing the application on page 13.

Thanks so much to all for taking your time out - I appreciate it.

aa) I would say the chill roll in your diagram is the master roll, which should go at a constant line speed. All other rolls would trim to control tension.

cc) I don't see an encoder? I don't really understand the question.

dd) I have not used a dancer with a brake before. Normally I would use a dancer with a driven roll. If I use a brake, I would use a loadcell to sense the tension.

Chill Roll Master, speed mode.

Payoffs and Takeups in diameter compensated torque control with either load cell or dancer trim, but if your diameter measurements/calculations are good enough, you wouldn't even need an outer loop to trim them.

Profit.

Thanks much Gents!, Gomez_ and rdrast!

@Gomez_
The encoder will be at the end of the chill bed.

@rdrast
noted with thanks

Any particular brand(s)/Model numbers of VFD you would recommend which will have adequate capability to handle the task in hand?

Once again, many thanks.

Are you using a PLC for this, or wanting to do it all from the VFDs?

If you can handle a common DC bus, you will save power.

Yep, but a simple PLC and HMI to monitor basic IOs, Temps and such - the math part I was hoping to keep within the VFD.

"If you can handle a common DC bus, you will save power." Could not understand this - pray elaborate.

Xsailor said:

Yep, but a simple PLC and HMI to monitor basic IOs, Temps and such - the math part I was hoping to keep within the VFD.

"If you can handle a common DC bus, you will save power." Could not understand this - pray elaborate.

Click to expand...

Although "Smart Drives" are everywhere today, I keep all of my drives as stupid as they can be. I can change from speed mode, to torque mode, to speed + torque (or current) limit, but do all of my reference calculations in the PLC. That way, when a drive needs to be replaced, it is much simpler to configure, especially when changing model or brand.

The above is only for standard applications, precision motion control/servo control is a different beast.

That is a logical and safe approach, in my view as well. However, I have no competence to take it to that level, at least not yet (wish I had!).
I have downloaded and read a lot of literature and user manuals of drive makers but nowhere could I see specific and clear-cut instructions for change from speed mode, to torque mode, to speed + torque (or current) limit.
Not even AD, whom I consider very good with writing easy-to-use manuals.

Any pointers please, rdrast? A few links would make my day

Where were you considering installing the load cell? I've dealt with load cells and dancer rolls for tension control, but never both together. In my experience, dancer rolls will get the job done, but load cells offer a much more precise control.

Cooling roll is your master.

From a web handling perspective, I will take a well built dancer over a loadcell. If you are tapering tension, you would then need an I to P to reduce the dancer pressure/tension.

If you are planning to use speed control (vs torque) you will need some form of feedback device (dancer /loadcell).

I typically only use a diameter sensor for my initial diameter (when the roll is first loaded into the machine). You will get a more useful and reliable diameter by calculating while running.

Xsailor said:

"If you can handle a common DC bus, you will save power." Could not understand this - pray elaborate.

Click to expand...

If you have more than one drive, you can link the DC bus externally between multiple drives. When one is braking the regen is used by the other drive(s), thus saving energy.

What are you using to control the NIP pressure? Is that a critical parameter?

also, are you going to use web guides?

Dravik said:

What are you using to control the NIP pressure? Is that a critical parameter?

Click to expand...

I would just use air pressure on pneumatic cylinders, then you can increase if it starts to slip... I would also put a brake system on any unwind product, this will keep the tension on the web so you do get runaways or slack

Install a pot on the dancer unwind and write a PID to keep the dancer in the middle for the VFD's

It also does not have much contact on the chill roller

I have made several rewinders and just used simple Minarik controlers that worked great

Is that your dip pan in the front? you may need a lower idle roller to give your product more time in the gel