Web Defect Inspection in the Printing Press - Research Under the Finnish Technology Programme, 1996 International Printing & Graphic Arts Conference Proceedings

Pertti Moilanen and Ulf Lindqvist

VTT Information Technology

The Finnish technology programme for the graphic arts industry (GAT) was carried through in the years 1992-1995. The activities focused on the following principal areas: integration of prepress processes, infrastructure for the graphic arts branch, automation, and ecology of printed communication. Altogether 9 research projects with specific goals and 38 product development projects were carried out by Finnish companies and research institutes. A number of new products were designed for a higher degree of process automation, and are now available to the printers. This paper outlines the most important results of related research under this programme. One of the research projects concentrated on web handling in the printing press, mainly on web defects. Web breaks characteristically start from a weak area in the paper. These weak areas are very rare, compared with the whole area of a paper roll. The purpose of this work was to study the interactions between web defects, special paper strength properties and the runnability on a printing press. A rotogravure press was equipped with an automatic web inspection device and over 2,300 rolls were inspected during a five-month period. Data was collected on the reasons for web breaks. The tensile stiffness profiles and the fracture toughness of the paper were measured in the laboratory. This paper outlines the relationship between the size and the number of holes in the web and the different types of web breaks. Also those special elastic properties of paper which predict good runnability were measured. The tolerances of critical web defects can be found with the help of real data from the printing press.