Wound-on-tension of Winders with Nip Rollers
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Roll-to-roll (R2R) manufacturing is widely used to create products from traditional web materials such as plastic webs, metal foils, to the recent printed and flexible electronics. Winding or rewinding is a critical component in any R2R manufacturing. Webs may witness damage and defects due to inappropriate residual stresses in the wound rolls, which cause economic losses. Preventing those defects requires an accurate prediction of wound roll stresses. The Wound-On-Tension (WOT) is the tension in the outermost lap of a winding roll. It is the most influential input which determines the wound roll stresses. The WOT is dependent of winder types, material properties of web, winding parameters, and geometry of the winder. In this study, an explicit finite element code Abaqus/Explicit is used to develop a model which account for all those aspects. Winder types of pure center winder, center winder with nip, surface winder, and hybrid (torque differential) winder were studied. The WOT is found to be governed by the contact mechanics, specifically the slip/stick behavior, between web and nip and web layers themselves in the nip contact zone. The explicit Abaqus model developed successfully deals with this problem. Web material properties are known to be state dependent on stresses and have a significant impact on the WOT. This is first time accommodated by implementing a user-defined subroutine VUMAT in Abaqus. New test methods were developed for material properties that are critical to the WOT but difficult to measure. Experimental verification of the WOT was conducted and good agreement was found. A parametric model was developed by Abaqus Python scripting, which facilitates use of the model to predict WOT by analysts in research and industry.
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