Air Entrainment During Steady-State Web Winding

[+] Author and Article Information
M. B. Keshavan, J. A. Wickert

Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213-3890

J. Appl. Mech 64(4), 916-922 (Dec 01, 1997) (7 pages) doi:10.1115/1.2788999 History: Received November 04, 1996; Revised April 07, 1997; Online October 25, 2007


As a web is wound at speed onto a roll, a thin layer of air becomes entrapped between it and the incoming web stream. The resulting spiral-shaped air bearing separates adjacent web layers and can extend many wraps into the roll. The air entrained during the winding process increases the propensity for lateral interlayer slippage and damage to the edges of the web. In the present paper, an in situ technique is developed for measuring the thickness of the entrained air film during winding, and parameter studies quantify the effects of such winding variables as tension, width, transport speed, and surface roughness. With a view towards evaluating different transport designs and operating conditions, three measures of air entrainment are discussed: (i) the cumulative thickness of all air layers, (ii) the thickness of the outermost air layer at the nip, and (iii) the rate at which air bleeds from the roll once it comes to rest. Measured values of the first two metrics are compared with those predicted by a derived two-dimensional reduced-order model for steady-state winding. The analysis treats the two bounding configurations of symmetric and asymmetric stacking of web layers by specifying appropriate cross-web pressure profiles.

Copyright © 1997 by The American Society of Mechanical Engineers
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