Flexographic Anilox Cell Metering Dynamics under High Shear Rate Regimes
Anilox metering under high shear rate regimes depends on ink rheology and blade deflection balance to prevent hydrodynamic lift and coat weight drift.
Wet Laydown Density
Initial Concentration
Concentration of ink or coating material immediately after it is transferred to the substrate defines the potential for final coverage and colour saturation. The wet laydown density determines how much solid material remains on the surface after the liquid carriers have evaporated or been absorbed. It is the primary measurement for assessing the efficiency of the application before the drying process begins.
Absorption Control
On porous materials like uncoated paper, the liquid part of the laydown starts to penetrate the fibres immediately. This movement can pull pigments into the sheet, reducing the intensity of the colour on the surface. Managing the initial density involves balancing the solids content and the viscosity to keep the coating where it is needed.
If the laydown is too heavy, the excess moisture can weaken the web and cause it to break. The use of pre-coatings or sizing agents helps to keep the wet film on the surface of the board.
Thermal Demand
Volume of the wet layer dictates the energy needed in the ovens to reach a stable dry state. A thick laydown requires more heat or longer dwell times, which can limit the speed of the press. Monitoring the initial state allows for better control of the final finish and ensures that the barrier properties of the coating are fully developed.