Dynamic Behavior of Steel Core in the Unwinding Process, 1992 Finishing and Converting Conference Proceedings

This paper presents an investigation into the dynamic behavior of steel core in the unwinding process. The objective of this study is to develop guidelines for choosing the size of core given a set of press operating parameters. Based on these results the proper core size can be chosen to avoid resonant vibrations of the roll for a given width and press operating speed.

Steel cores of standard dimensioning were tested to measure their natural frequency, damping, and stiffness. The tests were performed with varying amounts of paper attached and using different chuck pressures. In doing so, the interaction between the core and the paper was investigated as well as the influence of the chucks. The tests were correlated to an analytical model which used the finite element method of analysis. The finite element model was then extended to perform parametric studies using various core and paper dimensions.

The choice criteria was based upon avoidance of resonance. A rotation of the core at or near its resonant frequency will almost certainly cause failure of the paper. The rotational speed of the core increases as paper is removed at a constant press run speed. It is therefore most desirable that the rotational frequency be no more than 75 percent to 80 percent of the roll natural frequency. Finally, tables arc presented which specify the maximum roll width for 7.6 cm (3 in.) and 15.2 cm (6 in.) steel core.