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Blogmaster: Dr. David Roisum

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Crown Correction

Posted by David Roisum on January 10, 2012

My venerable Mechanics of Rollers book has a couple of omissions that I have long regretted.  They are both, fortunately, nicely published in Metso’s Up and Running web page.  The newest edition on Tips for Maintaining Rubber Covered Rollers has more than advertised by the title.  It also includes a crown correction calculation.  Given measured nip widths at the ends versus the center of the nip one can calculate a new or corrected crown.  Of course, you can also quite simply calculate theoretical crowns from beam bending equations as well.  One application for this crown correction calculation is if you are not able to calculate the theoretical deflection because, for example, you don’t know shell thickness, nip load or how to run a calculator.  Another is if somehow the crown didn’t end up giving a uniform nip.  The other equation given in the article is more limited and is empirical, but still may be useful if you want to calculate nip width given certain rubber cover parameters.

Posted in: Design, Maintenance, Nips, Rollers
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Dr. David Roisum

Dr. Roisum is a well-known authority in the area of web handling and converting. He has authored seven books, including Winding, Rollers and Web-Handling and has coauthored or edited several others. He was a technical editor for Converting Magazine with a monthly column entitled "Web Works." An accomplished professional speaker and instructor, Roisum has been praised for his skill at translating highly technical information into a common sense practical reference. Dave has been honored by TAPPI with their Finishing & Converting Division Award, Thomas W. Busch Prize and Finest Faculty awards and is a TAPPI Fellow. Dave received his Ph.D. from the Web Handling Research Center where he later became an Industrial Advisory Board member.

Dave has worked for the Beloit Corporation as a designer of winding machinery and later as a manager of research, and for Kimberly-Clark as a converting expert serving all business units. He is now a principal of Finishing Technologies Inc., providing consulting services to more than 300 clients who convert or manufacture: paper, film, foil, nonwovens, textiles and many other materials. He has accumulated much practical experience working in nearly 1,000 plants over the course of more than three decades.