Modern calendering technology for board and packaging paper

Board calendering technology is currently undergoing radical changes. Yankee cylinders can no longer be used due to the demand for higher productivity and higher speeds. They have been replaced by machine calenders and soft calenders, both of which give the board the necessary surface smoothness according to the physical principle of "gradient calendering". Up to now the replacement of Yankee cylinders has been carried out successfully in board machines which use fresh pulp. Board manufacturers who almost exclusively use DIP are, however; still sceptical whether Yankee cylinders can be replaced by machine calenders or soft calenders without a loss of too much stiffness. Nowadays, a multi-zone Nipcorect roll is used to achieve a better CD caliper-profile for base board. Calendering of coated board is done with soft calenders having a special, very soft cover. Higher demands are made on the printability of linerboard since corrugated board is increasingly used to carry advertising. This requires good smoothness for close contact between the ink carrier and the linerboard as well as homogenous compression/densification of the linerboard so as to ensure a uniform ink absorption. Soft calenders have a clear advantage over machine calenders in this case and thus are increasingly used for linerboard machines.