Web ​Handling And Converting

Because if you did, you would see two violations of "The Ten Command- ments of Web Machine Design" [1,2].  Command- ment #1 clearly states to minimize roller count.  (The corollary is to minimize web span length between critical processes.)  Commandment #3 clearly states to avoid slippage as must surely happen on those lightly wrapped rollers.
Aside from the cover, you will find the largest section of the book devoted to tribology and traction for those needing to go beyond band-brake, Knox Sweeney and the much much easier and free Air Lubrication Calculator by AbbottApp.  There is also a section on wrinkle models for those who need more than what you find in the freeWrinkle Predictor by AbbottApp.  Curiously, there are absolutely no references in the entire book aside from the author’s CV.  For those wishing to find the missing sources we have the free Roisum Library by AbbottApp. This book is available from the Converting Technical Institute, Tokyo.

1. Roisum, David R.  The 10 Commandments of Web Machine Design.  3rd Int'l Conf. on Web Handling, Oklahoma State Univ., June 18-21, 1995.
2. Roisum, David R.  The Mechanics of Rollers (Book).  TAPPI PRESS, 1996.

In this summary clip in a series we offer a checklist of questions to answer before spending money or  selecting the mode even if your already have one. 
Web201.42e Center-Surface Winder – Why Not?
https://www.youtube.com/watch?v=NXaFhlYac9s
***201.42e – Center-Surface Winder – Why Not?
05 Slides Duration 03.13 v 15.08.04

201.42e.01 – Title Slide
Welcome to Web-Handling.  My name is Dave Roisum.  In this clip we will give many reasons why you might NOT want a center-surface winder.

201.42e.02 - Checklist
We introduced this series with reasons why you might want this complicated winder.  The checklist here clarifies all of the necessities to make this investment pay back

1. Are your defects tightness sensitive?
2. Will extending the range of tightness uniquely help you with your particular defects?  In other words, you have run out of range with the tension and nip knobs and they can’t be extended further as easily and cheaply as adding a new knob.
3. Does the extension of this tightness work at the diameter range of your defects?  As we explained in an earlier clip the center-surface winder benefits are largely confined to the core area except with the super-loose gap mode which may suffer from too much looseness are roll diameter builds and more air is entrained.
4. Does the cost of the defects that could be recovered with this knob clearly meet payback on capital requirements of your company.
5. Do your engineering and maintenance and operating personal all understand what to do with this knob.
   
   

201.42e.03 – Other Considerations
We add a few closing thoughts.

1. The law of diminishing returns indicates that adding a fourth knob, center-surface winding torque differential, on top of the already existing tension, nip and speed, will be expected to have a relatively small effect.
2. Adding a motor on the moving element, whether roll or roller, will inevitably increase the mechanical friction of the nip.  This will increase its nip variability and decrease the ability to achieve light nip loads.  As we have indicated on many occasions, the nip should be a gold-plated knob and hanging more equipment on to it is not helpful in this regard.

201.42e.04 – What if You Have One You Don’t Need
Just because you have something doesn’t mean you should use it.  If the knob does not satisfy all of the requirements we listed earlier, then the knob should not be used.  I offer two subcases here.

If the knob is never needed, disconnect the motor.
If the knob is needed for some cases, run that motor at a no load motor torque setting so as to not inadvertently change winding tightness.

201.42e.05 – Questions?
Thank you so very much for watching this module in my plant practical video clips.  If you have questions, you may want to replay this clip series.  If the material still doesn’t make sense then perhaps my web or winding school might help give you the required background.

The title pretty much covers the territory and so does Jerry Brown.  In his remarkable website on guiding you will see a variety of studies on different guide types.  Scroll down to the 4th section and you will see animated simulations of how moving roller(s) will move or bend a web into a new path and the resulting web stresses and path errors.  Absolutely nowhere in the literature or the internet will you find a nicer collection of guide tech.  Jerry sets a very high bar for anyone claiming web-handling expertise or how to teach the tech.

P.S.: Don’t click on this picture as it is not a live link.  Go to his remarkable website and you will get many more in 5D (X, Y, Z, time and color).

All modes of the center-surface winder are rife with misunderstandings and that includes the gap mode.  First, is this mode used as a gap winder for wrinkle tolerance or is it used because a nip isn’t needed or can’t be tolerated?  Similar settings, but entirely different goals. One is a gap winder the other is a simple center wind and another still is the super-loose mode described in the last clip.  Second, what do you do with the driven now unnipped roller?  You can’t (or at least probably shouldn’t) merely disconnect the drive.  Find out why and what you should be doing.


Web201.42d Center-Surface Winder – Gap Mode
https://www.youtube.com/watch?v=WerXJJUqkVQ
***201.42d – Center-Surface Winder – Gap Mode
05 Slides Duration 04.56 v 15.08.03
201.42d.01 – Title Slide

Welcome to Web-Handling.  My name is Dave Roisum.  In this clip, we clarify two uses of the gap mode and how each would have a different torque strategy for the roller just upstream of the windup.

201.42d.02 – The Traditional Gap Mode
The purpose of a gap winder was covered in in great detail Web101.  In short, it is to provide the most wrinkle resistant winding mode by using several tricks and tools.  Of course, we have to give up the tightening benefits of a nip and may quite possibly be speed limited on wide smooth products such as most film grades.
However, in that class we often did not have time to explain what to do with a center-surface winder when it is put into gap mode as opposed to a pure gap winder.  In other words, what do we do with the motor attached to the roller.  You can’t, or at least shouldn’t, merely turn it off.

201.42d.03 – No Load Motor Torque
Recall from the drive section of Web101 the concept of no load motor torque.  It is the torque required on the motor so that no tension change is seen on the web going over that point.  The value of the torque the sum of motor and roller drag and other sources of friction, but most especially of the gearbox that is used as a speed reducer for the motor.  All good drive engineers should know how to find out the amount of torque that is required to match web speed versus machine speed, but with no web present, and program that curve into the drive.  That curve may need to be retuned occasionally, especially as the gearbox breaks in.  When you take the nip off, that torque is what should be applied to the motor.  If done correctly, the tension read by the load cells upstream would be very close to the tension going into the winding roll.  If there were no torque applied to that roller, the large drag would cause a very large tension rise meaning that the roll was wound at a much higher, but unknown level of tension.  To this we also add inertia compensation as was discussed in the web and winding schools.

201.42d.04 – The Super Loose Mode
In the two day web handling class we showed how the TNT’s can be adjusted so that the wound roll could be made anywhere in a range of tight to loose.  In the two day Winding class of Web101 we described how the center-surface winder motor torque split can be adjusted so that the wound roll could be made anywhere in a range of extra tight to extra loose.  In the last clip introduced thesuper loose mode, even more loose than a surface or centerwinder can obtain.  However, we didn’t explain how to run the motor.

In this and all other modes, the winding roll motor is in load cell tension control.  In this mode the roller motor will be run in torque, or better yet, tension difference mode.  The distinction here is merely the properly display units as the motor cares not what you call its effort, so you might as well use proper web units of tension.  The motor will be run at increasing levels of tension difference until the wound roll is loose enough or the web entering it is too loose.  The confusing thing about this mode is that any changes in the upstream load cell tension settings will directly affect web and winding tightness in that span.  This mode, however useful it may be, violates a best principle drive design guideline of not putting a motor, or any other large source of torque, between the load cell and the motor it talks too.

201.42d.05 – Questions?
Thank you so very much for watching this module in my plant practical video clips.  If you have questions, you may want to replay this clip series.  If the material still doesn’t make sense then perhaps my web or winding school might help give you the required background.  Of course, I always welcome comments, suggestions and questions and try to respond within one day to each and every one.

Our newest AbbottApp does several essential things that have rarely been done before in web-handling.  It considers more than one insult at a time as a web goes through a web machine.  Then if your tension control is not perfect AND your roller alignment is not perfect, both at the same time: no problem.  We can figure out how these and other stressors combine to increase the risk of web damage.  Do you run thick materials?  Well then you have two additional troubles to consider:  curl and bend radius.  No problem, just enter in curl radius and roller diameter and BINGO, you see just how bad things can get in a hurry with thick webs.  The next new and essential thing this app does is shows you how you are using up your total ‘error budget.’  We use a very clever visual display trick to do this.  It is called bar charts.  Yes, I know this is the joke of management presentations, but take a look and you will see how this is the very best way to present engineering information for this case.  Finally, we do something almost never done in the web-industries even though all engineers were taught that this (or something even more advanced) is necessary for safety.  That is safety factors.  Check out Combined Stresses Going Over Rollers as a beta app and see just how easy it is to run because it requires no special knowledge.  For those wishing a deeper dive just email me for a copy of my paper that explains how and why we must all do this.


A few admin notes for my followers.  This blog interrupts the recent vlog sequence and is a bit early because I am totally booked next week being five days on stage at the AIMCAL Converting Connect event.  Also note that my Web Handling school was sold out a month ago so that we may offer another this fall or you can also get the same trademarked Web101 material as video-on-demand or as in-plant courses.  The advanced winding course, on the other hand, still has a few openings.
Finally some notes.  The RSS feed for this blog has changed due to the new AIMCAL Website facelift, so update your browser appropriately.  Also, I am now on Twitter so you can follow me at @DavidRoisum, where I will tweet new blog posts as well as other short industry events related to web-handling.  Also, please subscribe to my AllWebHandling channel on YouTube if you want to get the vlog posts as they are rendered which is usually many months prior to showing on this blog.    The Web201 app by AbbottApp helps you search these nearly 200 short clips if you have trouble finding stuff using the google or youtube search engine, as you likely will because they are total crap for this purpose.  (See my paper titled Dead Trees and Web Handling for why this is so).  I am also on Linkedin where I host a discussion under the AllWebHandling group.  Sign in and get connected.  For those of you who like a daily dose of unusual photography, be my friend on Facebook (David R Roisum).  Some of the best of my 50,000 curated photos are on Flickr (drroisum).  I also have created a half dozen coffee-table books on Shutterfly that I have made for friends and relatives.  Or, you can just do it the old fashioned way, email me at DrRoisum@aol.com or check out my Website Roisum.com.

As described in previous posts, the center-surface winder is potentially the most capable in terms of the range of tightness it can create.  It is easy to understand how adding more knobs, center-surface wind torque differential in this case, might make a roll tighter than a pure centerwind.  However, it is not physically possible to make the roll looser unless you play a special little-known trick with one of the motors.  Find out how to obtain super loose if you would need it.
Web201.42c Center-Surface Winder – More Looseness
​
https://www.youtube.com/watch?v=Ssra6SaRUa0

***201.42c – Center-Surface Winder – More Looseness

04 Slides Duration xx.xx v 15.xx.xx

201.42c.01 – Title Slide

Welcome to Web-Handling.  My name is Dave Roisum.  In this third clip we describe how the center-surface winder can be ‘tricked’ into running super loose, possibly even lower that a pure centerwind might, which is the entire point of this usage.

201.42c.02 – CS Winder – More Looseness

A couple of tricks are needed to get super loose.  First, the center-surface winder must be put into gap mode.  Second, the center-wind motor is put into tension control as is normal.  Third, the surface-wind motor is put into torque control instead of torque differencecontrol.  In other words, this surface wind motor is running a setpoint positive torque regardless of what the center wind motor is doing.  This drops the tension from the span upstream of the surface wind motor to something less on the span entering the windup.

201.42c.03 – CS Winder - How

So, how is it that we might get looser than a pure centerwinder?  It might be because while we are cheating tension lower than might be safe in general, we are doing so only on just one very short span and crossing our fingers that we can get away with it.  It also might be that the inevitable and possibly notable tension rise coming from a number of upstream idler roller bearings can be set back down just prior to winding.

201.42c.04 – Questions?

Thank you so very much for watching this module in my plant practical video clips.  Stay tuned for the next clip where we describe motor control on this most complicated winder.