Nip Induced Defects of Wound Rolls, 1994 Finishing and Converting Conference Proceedings

D. R. Roisum

The most serious wound roll defects are caused by nips. These nip induces defects include: bursts, corrugations, crepe wrinkles, tears, and many more. These defects are insidious because they are often hidden until unwound by the customer. They are exacerbating because process settings may have little effect in reducing their severity. Finally, nip induced defects are reaching epidemic proportions as paper grades become thinner and slipperier, and as roll sizes increase in width and diameter.

This paper describes the underlying nip mechanics which are common to all of these defects, and the difference in interlayer slippage motions which made them appear unique. These mechanics will then lead us to the factors which are most important in determining the frequency and severity of these problems. As we will see, the most important parameters including paper characteristics, roll size and winder/unwind machine configuration are determined long before the paper is even made.