<p>Nonuniform web tension in roll-to-roll processes can lead to nonuniform performance of printed devices within a given web. To enable monitoring and understanding of this phenomenon, we develop and cross-validate two methods to measure the average web tension and its linear variation across the width of the web. The first method is a non-contact resonance method using the lowest symmetric and anti-symmetric frequencies of a tensioned web to predict average web tension and its linear variation. The second method is a gentle contact stiffness mapping method which obtains average tension and its linear variation by nonlinear regression of measurements of local contact stiffness along the width of the web. Both methods are based on first principles mechanics models of a tensioned plate and work for any web regardless of its physical properties, web path, and web tension. In addition, they are appropriate for both in air and <i>in vacuo </i>roll-to-roll systems. Cross-validation measurements on a stational test stand show the two methods agree within 5%. To demonstrate real world performance, we tested the non-contact resonance method in two spans of a moving commercial roll-to-roll system with three different web speeds and obtain up to 35.58% cross-span tension variation in that system. The average tensions can vary in different spans because of the frictions between web and rollers. We obtain up to 28.33% variation of average tensions between the two tested spans.</p>

Resonance and Contact Stiffness Based Nonuniform Web Tension Monitoring in Roll-to-Roll Processes

Paper Proceedings: https://asmedigitalcollection.asme.org/IDETC-CIE/IDETC-CIE2021/volume/85369

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