Influence Of Paperboard Production On Web Movement And Register Quality In Printing Process

Register quality is often influenced by challenging web runnability. For fiber-based materials like paperboard it can be originated in the boardmaking process and tried to be compensated by web guiding and register control systems in printing process. Within an interdisciplinary research cooperation with different participants along the value chain of paperhoard packaging production, the influence of different paperhoard production conditions and register control strategies on web movement and register quality in a production scale gravure printing machine was performed in this study. Based on different boardmaking conditions, 13 different paperboard qualities were produced and each printed with 3 different register control strategies. The resulting register quality in cross direction (CD) and machine direction (MD) were measured as well as web movement, web tension and web moisture with several sensors along the printing machine. To assign the root causes of paperboard-induced web movement to boardmaking conditions, mechanical properties like tensile stiffness index in MD and CD and tensile stiffness orientation of the paperboard material have been measured and compared with data on web movement in the printing press. Further, web edge data were analyzed in frequency domain, to assign characteristic frequency components to their different mechanical root causes in boardmaking and printing process. It was found that CD position on tambour is the most influential board side parameter on lateral web movement and register quality. The lateral web shift differs significantly for middle and edge reels. Main reason for misregister in this study was attributed to board side slow lateral web movements with increasing amplitudes along the printing press. A register control strategy with an increasing gain per printing unit was most effective to improve register quality for this runnability behavior.