Simulation of liquid transfer between separating walls for modeling micro-gravure-offset printing

A numerical study of the liquid transfer processes that occur during micro-gravure-offset printing is carried out. Specifically, liquid transfer between two parallel separating plates and between a trapezoidal cavity and an upward moving plate are simulated, as models of the printing of ink from the offset pad onto the substrate and the picking up of ink from the gravure plate by the offset pad, respectively. During the liquid transfer between two parallel plates, the stretching, breaking and recoil of the liquid are illustrated, and the generation of a satellite droplet is observed. The influences of the separation velocity, liquid viscosity, surface tension, gravity force, and contact angles on the liquid transfer are estimated. For the transfer of liquid from the cavity to the upward moving plate, the findings indicate that the process can be divided into three stages: (1) a whole stretching stage; (2) a central stretching, breakup and recoil stage; and (3) an equilibrium stage. The final width of transferred liquid is closely related to the contact angle at the upper plate, while the cut height is mainly affected by the contact angle at the cavity side wall. The effects of the initial distance and cavity shape are also discussed. (C) 2008 Elsevier Inc. All rights reserved.