Web tension profile and printing press runnability

An on-line web tension measuring device has been installed on a rotogravure press in a Finnish printing plant. The device provides both web direction and cross web direction measurement of unwinding paper rolls. The tension provides of over 5,500 rolls of LWC and SC paper were measured. The effects of web tension variability on press runnability and waste were documented. For good runnability and low wastage on the press, roll tension variability within a roll and from roll to roll should be within certain margins. The study also related tension profile development in the paper mill to the press room performance. It was found that the tension profiles on the printing press were inherited from the paper mill, either from the paper machine or the supercalenders. While the printing plant can accommodate certain roll to roll variability by sorting the rolls and running them in sequence, the problem of tension uniformity must be fixed in the paper mill. The means of control on the paper machine or on supercalenders are discussed.