Evaluating the impact of non-uniform paper properties on web lateral instability on printing presses

Lateral instability of the paper web during printing may lead to several quality issues such as print misregistration, wrinkles, tracking issues, etc. The problem often leads to paper rejects and claims from printers. There is limited information available to paper producers on paper wandering during printing. The problems may come from the equipment, lateral control or could be even the paper web itself. An empirical study was completed with numerous paper producers to evaluate the impact of non-uniform paper properties, both cross and machine direction, on web lateral instability on printing presses. The key component of the study was to quantify web instability. To do so, portable positioning edge sensors were used during printing runs, as well as on lab equipment, to quantify the amplitude and frequency of any lateral movement.Concurrently, apparatus such as TapioTM and one-of-a-kind paper roll testing equipment were used to measure paper properties and assess their variability. Lateral displacement and paper non-uniformity and variability were then correlated. In many cases, lateral instability of the paper on printing equipment was related to the non-uniformity of the cross-direction tension profile of the paper. Other contributors to lateral instability were the periodic variability of basis weight and fiber orientation in the machine direction. In this article, case studies of mills that have worked on reducing properties non-uniformity will be presented as well as the impact it had on web lateral stability