Details:
Summary:
Piling problems can occur in many lithographic printing applications. It involves the build up of material on the blanket surface which leads to unacceptable print quality. The aim of this work program has been to understand the performance of a heat set web offset press with respect to piling to allow subsequent optimization. Earlier work [1] reported on the effect of process consumables on the degree of piling measured using profilometry. The measurement of piling using profilometry was focused on selected areas within the image. These were areas that there was a transition from image to non image area where a step feature could be measured. There were a minimum of forty eight measurements carried out for each trial. These were then converted into a step height in microns. The piling was quantified using manual assessment of the blanket surface. This was carried out by a single press operator in all forty eight trials that were completed. The assessment covered the whole blanket surface and included assessment for image, non-image and downstream piling. The piling was quantified on all four units using this method. The results from the manual assessment are presented for the impact of each of the variable assessed, namely paper, blankets, ink, and fountain solution. The results show that these can have a significant impact on the level of piling. This paper then focuses on comparing the piling measured by these two techniques. One is an analytical method that is much localized in its operation while the manual assessment provides an overview of the whole blanket surface. These comparisons show that there can be significant differences dependent on the measurement method used. These differences are discussed in detail with respect to the actual application and explanations are provided as to the best technique with which to quantify the level of piling on the blanket surface.