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.
Carreau Yasuda Model
Rheological Equation
Non-Newtonian fluid equations characterize the shear-dependent viscosity of polymer solutions and pigmented paper coating formulations. Five empirical parameters allow precise curve fitting across low and high deformation regimes. The carreau yasuda model expresses effective viscosity as a continuous function of shear rate while incorporating zero-shear and infinite-shear asymptotic limits.
Coater operators use these values to predict liquid resistance under high speed metering blades where shear rates exceed one million reciprocal seconds. Structural yield stresses and thixotropic breakdown limit the applicability of the mathematical function.
Coating Shear
Viscous forces in blade coater nip zones govern wet film thickness and fluid penetration into raw paperboard stock. High velocity blade metering creates extreme deformation rates that force polymer molecules and mineral pigments into aligned flow patterns. The carreau yasuda model quantifies the transition width between Newtonian plateaus and power-law thinning regions through a dimensionless curvature parameter.
Hydrodynamic forces calculated from this curve determine metering blade pressure settings. Improper fitting of the intermediate shear region causes unexpected coating weight variation across the web width.
Viscosity Transition
Mathematical stability degrades when fitting parameters against limited experimental data points. Rheometers operating at modest shear rates cannot capture the high shear viscosity plateau without extrapolation errors.