Pressure and shear flow singularities: Fluid splitting and printing nip hydrodynamics

Abstract

Numerical simulation of the fluid flow in the gravure printing nip, based on a discontinuous Galerkin (DG) algorithm, is used to study the fluid-splitting process, the transition between point and lamella splitting. We study the pressure and shear singularities at the contact point of printing cylinder and substrate as a function of the variable microscopic residual gap and variations of the printing fluid quantities introduced to the nip. As the hydrodynamic boundary value problem is ill-defined by the nip singularity, we enhance the simulation using renormalization group and algebraic scaling techniques in order to obtain a numerically stable and physically meaningful prediction. Our simulations are compared to analytical results from lubrication theory, and to experimental observations on a gravure press.

Numerical investigation and optimization of doctor blading in the gravure printing process

“…For optimal operation and print quality, the skilled printer also has to consider further criteria beyond air removal and color correction when adjusting the doctor blade angle. Depending on the kind of printed product, the printing nip can be educated for a spreading or coalescence of the deposited ink drops on the substrate, and rastered or closed ink layers can be created, see 9 .…”