Papermaking Results Using HyperScan a Full Sheet Imaging System, 1998 Process & Product Quality Conference Proceedings
Recent results with Accu-Ray HyperScan tm), a full sheet unaging system for papermaking, indicate how imaging the entire sheet can lead to improvements in paper uniformity and in paper machine operation. In this paper, visibility provided by full sheet imaging is used to optimize the operation of fabric cleaning showers.
Previously, such optimization has focused on the ckaning aspects of operation. Resultant basis weight patterns unpressed on the sheet by the operation of the showers have neither been evident nor considered in the optimization.
Now, such patterns can be identified in the images provided by the full sheet imaging system. These images show characteristic zigzag patterns of basis weight variations in the sheet, with peak-to-peak variations on the order of 1% of target weight, a level comparable to remaining cross direction variations provided by machines under good cross-machine control. The zigzag patterns identify accumulations of fiber/basis weight at recently cleaned wire locations, and reductions of fiber/basis weight at recently cleaned felt locations. Wavelet techniques are employed to enhance the patterns and quantify the sheet uniformity. Significantly, the level of variations can be affected by changes in the operational settings of the showers. These parameters can be altered to minimize product variability while maintaining proper cleaning action. Thus the utilization of full sheet imaging can lead to reduced paper variations and improved paper machine operation.