Presentations

Presentations prove to be very effective in increasing the understanding of the different negative effects of vibration and its solutions. The main purpose of these presentations is not so much to advertise our company as to give you and your staff a more in-depth description of the subjects covered.

Basis Weight Variability

The paper and accompanying presentation, titled The Struggle for Paper Uniformity, outline the machine direction basis weight variability at a specific paper mill. Problems that resulted from the MD basis weight variation and the steps taken to solve the problems are shared. The clearly identified problems were register variations and cockling. Other problems that would be associated with variations but not clearly identified were paper runnability on the machine, on the winder and in the pressroom. The problem solving process included spectral analysis, operating deflection shape analysis, modal analysis and finite element analysis. The presentation shows an animation of the headbox vibration, the key problem area.

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 that each end of the roll follows the motion of the other end exactly. Subsequent work has shown that 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 are 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.

Oxbow Effect and Surface Temperature Profiles of Calender Rolls

Calender rolls distort on the ends where the paper is not acting as a heat sink. This can cause soft edges and cracks on the reel due to ends that have expanded more than the rest of the roll. Alternatively, the rolls can have hard edges when the ends of the rolls have been over-insulated and are of smaller diameter.

This presentation will go through the calculation procedure using finite element analysis of the shape of the calender roll in use. It gives examples of the calculated temperature and distortion profile. It discusses the methods that can be used to reduce the amount of deformation. The discussion concludes with the measurement of a temperature profile through a calender stack.

Mill Application of Finite Element Analysis to Solve the Problem of the Oxbow Effect

The finite element technique is applied to a calender roll to predict its temperature profile and deformed shape. This is used to design the required insulation at the end of the calender roll to prevent undue distortion. The design procedure is outlined, and the results of the procedure noted.

Winder Vibration related to Set Throwouts

Winder vibration can often be a production bottleneck or lead to a set being thrown out of the pocket of a winder.  Measurements to find the vibration while winding a complete set are used to determine the vibration characteristics of a winder.   This can be used to determine if the set or a winder roll is the predominate cause of vibration.

Paper Machine Speed Increase

Paper machine speed increases can affect the vibration of the machine leading to problems in paper quality or in excessive vibration, shortening the life of the machine. This presentation shows the effect that speed increases can have on paper quality and on the machine. It also covers the techniques used for predicting vibration when the machine speed is increased. Of particular concern is preventing unwanted resonances, to ensure that there will be no surprises at the higher operating speeds.