Optimizing quality and runnability of printing papers and board

Manufacturers of paper and board for printing, both uncoated and coated grades, are facing increasing competitive pressures. There is a critical need to optimize quality while keeping production costs as low as possible. Runnability in the mill and at the printers without web breaks is also a goal. To achieve these requirements in the proper balance for each grade, new technologies are being developed and implemented. Continuous and very precise monitoring and control of sheet variables during production improves uniformity and machine efficiency, quickens startups and grade changes, improves print quality and reduces the number of web breaks in the mill and at the printers. In the forming section, a newly developed on-line sensor now can continuously monitor basis weight as soon as stock is on the wire. For fastest control at the headbox, full-width weight profile information is updated every second, and for process improvement studies, updated at 600 Hertz. To optimize forming, pressing and drying, as well as size press, coater and finishing operations, traversing sensors can now provide resolution of 2 mm width while moving across the sheet at speeds up to 600 mm per second. Precise coat weight measurement is available even when both sides are treated simultaneously as with metering size presses and coaters. To eliminate print mottle caused by binder migration, coater drying is being modeled in real time to control the gel point location. Surface smoothness quality for printability is being monitored on-line with specially developed sensors. Advanced finishing technology for calenders of all types precisely controls smoothness and gloss on each side of the sheet. On-line web imaging systems detect and immediately inform of any surface imperfection. The objective is `Zero Defect' printing grade production at the lowest possible cost.