Calendering and Model for CD Control, 2001 Engineering / Finishing & Converting Conference Proceedings

D. W. Kawka, R. H. Crotogino, W. J. M. Douglas--A dynamic model of the calendering process was developed by appropriate combination of the model of transient local calender roll deformation with the calendering equation used to estimate, at a specific CD position, in-nip strain from permanent strain.

Use of the model shows that paper response to a control action is highly sensitive to local nip load and to temperature and moisture content of the paper. After validation with published measurements on an industrial calender, the effectiveness of this model for minimizing thickness nonuniformity in the CD dimension through implementation of model predictive control of calendering was demonstrated. For a multi-roll calender stack of industrial specifications this demonstration showed an impressive reduction in CD control response time through use of multi-step control action. This model opens the prospect of a significant industrial innovation through the introduction of model predictive control to the difficult problem of CD control of calendering.