Cross Machine Caliper Profile Control on High Speed Coated Packaging Lines
Cross-machine caliper control demands real-time induction calender profiling to maintain stiffness and prevent high-speed converting line jams.
Headbox Slice Control
Distribution Mechanism
Regulation of the narrow aperture through which the fibre suspension is discharged onto the forming wire determines the initial weight distribution of the paper web. Headbox slice control uses a series of adjustable actuators or mechanical screws to vary the height of the opening across the full width of the machine. This system ensures that the volume of pulp delivered is consistent, preventing thick or thin spots in the final sheet.
Flow Regulation
Actuators respond to data from downstream sensors that measure the basis weight of the moving paper. Effective headbox slice control manages the jet-to-wire speed ratio, which influences the orientation of the fibres and the strength of the paper. Small adjustments to the slice lip can correct localized deviations in the cross-machine profile within seconds.
Modern computerized systems integrate these movements with moisture sensors for a comprehensive quality check.
Weight Uniformity
Precision in this area is required for the production of grades that must meet tight weight specifications, such as lightweight packaging or high-end publication papers. If the headbox slice control fails to maintain a level profile, the resulting paper may exhibit poor winding characteristics or uneven ink absorption. Advanced hydraulic systems now allow for even finer adjustments by injecting dilution water at specific points instead of just moving the mechanical lip.
This technology reduces the mechanical stress on the headbox components while improving the smoothness of the finished sheet.