Computer Simulation for the Cavitation Changes at the Exit of Offset Printing Nip

Abstract

ABSTRACT Offset paper printing is a promising roll-to-roll technique for color printed materials. Although it is no doubt that understanding ink transfer mechanism in offset printing process is necessary to achieve high printing quality, investing the relationship between inks and substrates at the nip is difficult ex-perimentally due to high printing speed. In this paper, rheological behavior and splitting point of the ink at the nip is studied using package software Ployflow and Flow 3D based on Navier-Stokes equation. Polydimethylsiloxane (PDMS) ink and IGT printability tester were used for an model ink and experiment to compare with that of simulation data, respectively. As a result, higher viscosity at state flow and pres-sure increased ink transfer due to higher possibility of presence of cavitation at the nip and increase in covering area ratio. These results have shown good agreements with experimental data compared by measuring density of print through. keyword : offset printing, paper, PDMS, cavitation, simulation