Maxcess International -Fife, MAGPOWR, and Tidland present Converting Blog

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Filed under: General Business Topics --- khevenor @ 01:12 PM

I've spent the better part of the last few months traveling around to all the industry meetings and conferences, and I must admit that I was a bit concerned that I would start hearing the same information over and over again. But I've been pleasantly surprised. From events offered by Packaging Strategies to AIMCAL to RadTech and others, I've found that the converting and packaging industries are so dynamic that professionals must take advantage of all these educational opportunities to remain competitive and knowledgeable. So whether you are seeking insight in a particular area of technology or simply a better understanding of the business of converting and packaging, industry events remain the place to be.
As CMM approaches, I feel confident that the comprehensive conference program together with a wide variety of exhibitors and this year's new Technology Centers (which will feature running equipment on the show floor producing live jobs in a true integrated production environment) will equip attendees with the information and skills needed to succeed in the market. Since acquiring CMM about a year and a half ago, we've worked really hard to re-focus the event and restore it to its strong position of many years ago. Working closely with most of the key publications and associations in the converting market, we have put the industry's most important event back on track and are excited about the overwhelmingly positive feedback we have received.
Having said that, I know that there is always room for improvement, and I invite you to contact me with any suggestions you have. I'm sure I'll see you all at CMM in Chicago in June!
- Keith Hevenor
Editorial/Conference Director
CMM International

Filed under: Winding, Unwinding, Roll Defects --- Tim Walker @ 12:35 PM

Someone wrote me this week to get a sanity check on when center-surface winding makes sense.

Definition: Center winders drive a roll from the core or center. Surface winders drive a roll a nipping roller in contact with the roll's outer surface. Center-surface winders do both, driving the roll from a combination of center and surface driving.

The inquiring party makes several good points / questions:

> Center-surface winding makes some sense for very slippery (low web side A to side B coefficient of friction) webs.

Yes, this is to avoid how much torque needs to be transmitted through the roll.

> The bottom line on wound roll tightness is the wound-on-tension and the profiling of the WOT versus the roll diameter (a.k.a. WOT and taper tension).

FYI, WOT is the tension of each layer as it is added to the winding roll) and is a function of applied center torque and winding nip load.

> A center winder with nip pressure control can achieve a large enough range of WOT to wind most everything.

Yes, I agree again. The paper industry (and other LARGE roll winders) use surface winders since torque is independent of roll diameter. Center winders can be limited if the core to final roll ratio is too high (a.k.a. the buildup ratio).

> Why do people 'need' the extra complication and cost of a center-surface winder?

I think of most center-surface winders as surface winders with center assist. Surface winders can have trouble getting the initial layers near a core tight enough and the center assist can help with this. If you want to wind an ultra-soft roll, say a nonwoven or tissue product, your surface winding can only go as soft as the nip load required to turn the core, core shaft, and bearings. If you have a center assist, you can go to lower nip loads and softer rolls.

> What does the addition of the last 'T' knob (in TNT) give you besides more variables to mess-up?

Yes, may people that buy surf-center winders never figure out what to do with them.

There has been some interesting work out of Oklahoma State's WHRC how different nip rollers change the tension induced from the nip roller, but it's still all about modeling a roll from a given WOT vs. diameter. I think there is work yet to be done on how WOT from tension and WOT from nip may magnify or de-magnify crossweb roll variations from crossweb caliper and roll diameter variations, but I haven't seen any good work to point anyone in the right direction.

Conclusion: Use winding technology appropriate to your application. Don't get more knobs if you don't need them.

-tjw

Filed under: Guiding, Spreading, Wrinkling --- Tim Walker @ 11:58 AM

I got an email from a fellow web handler recently saying they were visiting a plant and had just spent the better part of an hour removing spiral-wound tape from many idler rollers on a thin film laminator that were used to prevent wrinkles.

This web handler knew the theory that spiral tape has no spreading effect, but wanted to know how to battle the strong local opinion that the tape spirals were required to prevent wrinkles.

My reply:

What can I say about helically wrapped tape on rollers? I’m not a fan and yes, Ron Swanson of 3M proved (and presented a paper at IWEB in 1997) that there is NO SPREADING from spiral tape.

So why is it popular? It there something more happening than the pleasing and mesmerizing optical illusion? I think ridged rollers, either ridges formed by the gap between spiral tape bands or the ridges of one tape banded stepped on top of another, can have a wrinkle disturbing or wrinkle dispersing benefit. If the unwrapped roller is prone to wrinkles from the combination of traction, misalignment, diameter variations, baggy web in long spans, or other wrinkle sources, then the spiral tape can help by turning a tendency to form one big creasing wrinkle into several smaller non-creasing wrinkles.

Do I like spiral tape or recommend it? No, but it may seem like the easiest way forward.

My preferred plan of attack is the same as the person who sent this question.
1. Remove the tape and see what's up.
2. Diagnose where the wrinkles are forming, starting with the first, most upstream wrinkle.
3. Look for the tale-tell signs of shear wrinkles caused by poor alignment (diagonal troughs and walking wrinkles).
4. Measure and maintain alignment.
5. If wrinkles persist in a few locations (rarely do all rollers have wrinkles), try using masking or similar tape to create a concave roller with a percent diameter variations appropriate to the web strain.
6. If concave rollers don't work, feel free to try your favorite spiral tape pattern.
7. If you want to eliminate all tape on rollers, which is a great idea for contamination-sensitive products and for an operator-independent process, there is more hard work ahead, but it can be done. This harder way forward includes work towards optimized traction (wrap, tension, and traction coefficient), optimized span lengths, reducing bagginess, and tactical use of concave rollers.

The best argument against tape is contamination. If tape is left on a roller long enough, eventually you see small pieces missing. Where did they go? Off to you customer and won’t they be happy!?

tjw

For an update on this story, check the comment below:

Filed under: General Business Topics --- Tim Walker @ 10:40 AM

I got a phone call today regarding my post of March 2006 on calculating wound roll inertia. The called asked if there might be an error in my calculation, since he was working it out and couldn't get the same answer I had. It ended up that we both had some math errors. My calcs were right, but in the post I had left out multiplying by width as part of the inertia calc (now corrected). The caller rang back and said they are used a gravity term with the wrong units. In the end, we both got it right.

It was nice to have some live input from what can otherwise by a low interaction experience, blogging, that is. In blogging, you post and....nothing. Where's the immediate gratification. There isn't any. It's like writing a book. If you write email, you get replies. If you write a magazine column, at least a check comes in the mail and you see your writing in the magazine when it comes in the mail. But blogging, is hard to feel the reward, especially when I'm just writing about what I've been thinking lately. It's much more fun when this blogging thing is more a dialogue and less a monologue.

So my request to you convertingblog.com readers is PLEASE send me some questions.