Optimizing nipped roller systems

Abstract

Nipped rollers are central to many web converting processes - printing, coating, embossing, calendaring, and winding. Uniform products require uniform load and pressure from the nipping process. Uneven nipping not only creates product variations, but can lead to high levels of waste from web shifting, wrinkling, wound roll defects.

Imperfections are inherent in nipping - from variations in roller diameters, product thickness, and roller deflection. For most nipped process, many variations are hidden by the compliance of a rubber roller covering. However, any nipped roller system has competing design factors. Hard rubber coverings last longer, but are less compliant. Smaller diameters create higher pressure, but will have more bending and deflection under uneven loading. Is there an answer or guideline to rubber roller mechanics besides "What did you use before?"

This paper reviews the process of balancing rubber covering and roller design based on one simple goal: ensure roller bending deflections are less than rubber roller compliance. The models for rubber covering and roller deflection will be combined to give a clear view of this goal and provide design guidelines to ensure it is achieved. In addition, the paper will review methods to assess nipped process uniformity and remedies to create more uniform nipped processes.