New Methods for the Analysis of the Paper Web Performance on the Press

摘要

Web breaks, register errors, wrinkling and instability of the paper web are the major runnability problems on the printing press. These disturbances are caused by interactions between the paper web and the press. Over the past decades many studies have been carried out without any break hrough in the evaluation of the most important factors that affect these disturbances. In this study, a new portable tension-profile Measuring unit has been used in several printing presses. This system is able to measure the cross-directional web tension profile, with a high frequency, on both printed and unprinted webs. Together with the CCD-camera-based high-speed web-width and online register measurements, this provides a powerful tool for the analysis of paper web performance. In addition to the measurements, physical modelling makes it possible to gain a better understanding of web dynamics. The beha iour of the paper web cannot be satisfactorily explained by traditional laboratory tests, especially if the paper is being printed. In this study, the finite element method was applied to study the tension profile of the paper web as well as the interactions between the paper and the printing press. Measurements were made on several printing presses. The interactions between the paper web and the press were studied by measurements and by finite element modelling. Physical models were evaluated with respect to data measured on the presses. Based on this analysis, different factors that affect runnability are outlined and guidelines are proposed for actions to improve runnability.