Lateral dynamics simulation of webs having cross-machine direction variation

Abstract

Webs often include sectional variation in caliper or modulus of elasticity as a result of undesirable manufacturing variation or by intentional design. These variations influence wrinkle formation and tracking control in multi-span web handling systems. This paper shares the results of finite element simulations of the lateral dynamics of webs having variation in thickness and modulus in cross-machine direction. Span length and machine-direction bulk strain were varied and the effects on lateral steering and wrinkle formation were simulated for a variety of inhomogeneous webs.

Key variables affecting the lateral steering include the CMD location of the thick section and its width, the stiffness of the thick section, the z-direction bias of the thick section relative to the roller surface, the average strain in the composite web and the span length/width ratio. The web shifted in most cases toward the half of the web having the thick section, though not all. The combination of a web with a thick, stiff section having a width 1/10-1/6 that of the base web, coincident with the web edge, in long spans with low strain generated the largest lateral shift. Wrinkles were generated for some conditions where the thick section was located on or near web centerline.