New Edge Tracking and Control Technology Increases the Sheet Trim Width

摘要

Being able to accurately and continuously track the sheet edge on the paper machine, winder and supercalender is important for maximizing the overall paper trim width, as well as paper quality. By using the latest high-speed line scan camera technology, it is now possible at very high speed and accuracy, measure the sheet edge at all of these important locations. The methods up until now have been limited to mechanical systems and various optical & inductive methods that have had insufficient accuracy and speed to allow better, as well as faster control of the sheet edge position. It has been now documented with this new edge tracking system, called the VisiEdge that mills are able to achieve better cross direction (CD) control of all of the profiling variables such as basis weight, moisture and caliper. This is particularly important with narrow zoned dilution headboxes that demand precise CD basis weight mapping, that can only be achieved with fast and highly accurate overall sheet width measurement. Similarly on winders and supercalenders it is known that by better tracking the sheet edge it is possible to reduce the trim and thus increase production. Several successful installations are now operating in Scandinavia and this paper goes over these results. A winder application at the UPM-Kymmene, Jaemsaenkoski mill is discussed in detail where they were able to increase the overall trim width by from 1% to 4%, providing a less than one month payback. This new means of tracking and controlling the sheet edge has now been proven on all types of paper machines, ranging from slower board machines to the worlds fastest machines producing LWC, SC and newsprint.