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.
Rod Coater Metering
Coating Regulation
An industrial application system controls the amount of coating formulation applied to a paperboard web using a grooved or smooth rod. Through rod coater metering, the excess coating liquid is scraped off the sheet as it passes over the rotating rod, leaving a precise weight of coating on the paperboard. This technique is used for high coat weight applications where a smooth and uniform surface is required for premium printing.
The system’s application is limited by the viscosity and solids content of the coating slurry.
Volumetric Control
The rod has spirally wound wire or machined grooves on its surface to create small open channels. When the paperboard passes over the rod, the coating liquid flows through these channels, determining the thickness of the applied layer. By changing to a rod with different groove depths, operators adjust the applied coat weight to match the grade specification.
This method provides highly uniform coating distribution even when the base sheet has varying density or roughness. The continuous rotation of the rod prevents dried coating buildup and reduces blade lines.
Mechanical Wear
Frictional wear of the metering rod alters the groove depth over time, gradually reducing the applied coat weight during a production run. Monitoring this wear is necessary to ensure consistent printability. Regular rod replacement maintains the coating thickness within the required tolerance band.