Effect of Supercalendering on the Web Tension Profile, 1997 Finishing and Converting Conference Proceedings

Markku Parola, Timo Kaljunen, Hannu Linna - VTT Information Technology <>

Web tension profile measurements were carried out in three paper mills. The reel stand of a rotogravure press was equipped with a new web tension profile measuring system by which over 5,000 rolls were studied. The tension profile measured in the printing press corresponds to the profile measured on the winder and it differs from the tension on the paper machine. The supercalender dominated the formation of the tension profile because of the plastic deformation of the paper web. Further on the tension profile is affected by the differences in the stress relaxation and the creep inside the parent reel. According to this study the changes in the tension of supercalendered paper can best be estimated by the changes in the tensile stiffness of the paper and in the reel hardness. It is possible to adjust the tension profile on the supercalender by profiling the steam showers, the nip pressure and the temperature. As these adjustments also affect the other paper properties, their relationship should be included in the control system. Variations in the web tension profile have been found to affect the amount of web breaks and paper waste produced in the printing press.