No. Profile variation is one of the biggest challenges in the collective web manufacturing and converting industries – and it is one of the biggest causes of waste, delay and customer complaint. Bagginess, wrinkling and winding defects are just a very small sampling of the troubles caused by profile. Finally, it is one of the biggest causes of confusion. So, while I have used the word ‘profile’ nearly a hundred times in the quarter-century I’ve been writing this column, there still is more to say, or at least remind.

Defining profile

First, a definition. Profile is a variation of something across the width of the web, where the ‘something’ could be anything. The most common usage is for quality measurement, such as thickness. Profile is a wonderfully versatile term because we don’t need to be specific to begin with. We could just say that the customer is complaining about end rolls; thus, we have a ‘smile-shaped’ complaint profile. However, to do much more than complain or lament, we must be more specific about the complaint and the cause. With effort, we might come to find that the ends have a relatively higher thickness that is causing edge bagginess when wound.

So, for the example above, what thickness range might be cause for complaint? The range for most webs and customers is something like this: 1% variation > few problems, 10% variation > few (salable) products. Of course, there are exceptions. Foil needs to be better because flaws show so visibly. However, blown film (think garbage bags) can get away with a bit more, for reasons such as expectations tend to be less and the product is heavily oscillated in manufacturing.

Sources of confusion

Herein lies two of the many sources of confusion. The first is that such a tiny level of thickness variation may well be below the threshold of control or even measurement. That leads many astray to think that the web is as good as can be and, thus, is good enough. However, the wound roll may not agree, simply because it usually is by far the fussiest customer for level profile. That leads many astray in a second way because they think that because the winder ‘made’ the problem, the winder can unmake it by some magical set of TNT curves. That often is naïve.

Rather, it often is the winder telling the user that the material that was made is unwindable (without economically unacceptable levels of waste, delay and customer complaint) given any winder make, model, vintage, style and TNT settings. Yes, this is a generalization, but with no other information that probably is the safest mindset to begin with.

A few last words

So now, a few last words about these last words. While in the great majority of cases level is better, that is not always the case. I will give three examples of exceptions. The first is that ‘football-shaped’ wound rolls (frown-shaped thickness profile) are slightly less prone to entraining air (and the resulting defects) because the air can escape more easily out the edges. The second is the opposite shape: A wound roll with belled (high) edges can act like a concave spreader and thus minimize wrinkling that initiates on the roll. Finally, an irregular profile (think lanes) – and especially if also irregular in the MD (mottled) – can help hold the roll together better, something like the treads on a car tire.

However, before these level-is-best exceptions tempt someone into complacency, let me warn that those unlevel profile games can be safely played only if first mastering level to the couple/few percent described above. Then the edges (center or irregular middle) are made almost immeasurably thicker. Because we usually can’t measure it, we infer it by how the wound roll looks and behaves, no different than what we do if we want dead level.

(not) The End (of this story).   

David R. Roisum, Ph.D.
920-312-8466; drroisum@aol.com
ARC Member, ARC TV Presenter,
R2R Presenter, Converting School Educator