Practical application of idler roller performance measurements and models

Abstract

Idler rollers are present in abundance on most web processing lines. Their simple design, a rotating cylinder driven by the web-to-roller traction, lead most to go unmonitored until degrading performance results in product defects. Idler roller performance is a balance of traction versus opposing forces of drag and inertia. Idler rollers appropriately designed for their specific application will prevent scratching, minimize web tension losses, and ensure good tracking. Past authors have presented simple measurements and models to evaluate bearing drag of an idler roller assembly, but have not presented the complete analysis needed to determine the risk associated with poor idler roller performance.

This paper presents a complete guide based on previously published models and measurement methods to evaluate idler roller performance. Step-by-step instructions show how to use the Spin Down measurements plus bearing drag, roller inertia, and traction models to determine any roller's risk of slipping. A new term is introduced, the Traction Safety Factor, to assess and compare the risk of idler rollers slipping and to identify irregular performance. Beyond the recommended measurements and models, this paper will also review lessons learned in applying this protocol to a coating web line with over 300 idler rollers.