Calender Barring

Calender barring is a self-excited vibration that typically occurs at frequencies of 75 Hz and above. Much work was done in this field 10 to 20 years ago; yielding a number of computer programs that attempted to model the vibration, and recommended offsets that would eliminate the barring. These models assume that the roll is a rigid mass -that there is no flexibility in the roll and each end of the roll follows the motion of the other end exactly. Subsequent work has shown that the rolls do flex and that one end of a roll does not necessarily move in phase with the other end.

A fresh look has been taken into the fundamentals of calender barring using theory that has been developed for self-excited vibration in fields such as machine tool dynamics. This presentation shows a new model developed for calender barring. The dynamics of the calender stack is shown without the caliper variations of the paper present, and with the caliper variations acting as the self-excited vibration force. The presentation goes on to outline a procedure to understand and eliminate calender barring.