Modeling thickness and roughness reduction of paper in calendering

A new viscoelastic-plastic material model is proposed to describe paper compression in the thickness direction. This model is implemented to predict the reduction in caliper and roughness of paper in the hard-nip calendering process as a function of paper properties and calendering parameters such as line load, speed, and roll radii. Using an optimization procedure, the model parameters are calculated from the calendering data for three commercial newsprint samples. The average relative errors for the calculated thickness and roughness of newsprint samples are < 3% and < 9%, respectively. The model parameters determined at a given calendering speed are used to estimate paper caliper versus line load at a different speeds with a good accuracy. The proposed approach may be used as a tool for quantitative analysis of changes in the calendering process or for extending pilot calendering data to commercial conditions.