Study of fluid-structure-contact interactions for ink transfer modelling in a contact-based printing system

Abstract Fluid–structure–contact interaction (FSCI) phenomena have been studied in recent years for only a limited range of applications, such as the interaction of air with multiple parachute canopies and blood flow through heart valves. Ink transfer in contact-based printing systems, such as flexographic printers, is a significant example of such phenomena and can be adequately understood only when investigated as an FSCI problem. This paper aims to pioneer the study of ink transfer between interacting rollers by proposing a methodology applicable to a wide range of FSCI scenarios. The methodology includes prescribing a small gap where the structures establish physical contact and applying an auxiliary fluid in the gap with a viscosity high enough to prohibit its movement, thereby practically replicating the real closed contact. A Lagrangian conformal mesh approach is employed to maximise accuracy while maintaining reasonable computational cost. Simulations were conducted on a scenario involving substantial deformation of a roller surface and its penetration into the microcavities of the other roller, where the ink initially resides. The results demonstrate different phases of ink transfer between surfaces: pre-contact, contact development, isolation, contact opening, and surface separation, during which ink breakup occurs. The pressure was observed to rise significantly during the penetration phase, reaching a peak value of approximately 1 × 106 Pa. The ink transfer rate was calculated to be 27%, consistent with the relatively lower band of reported industrial ranges. The ink transfer rate was calculated to be 27%, consistent with the relatively lower band of reported industrial ranges. These findings provide insights into understanding and controlling ink transfer between rollers, which can help maximise cell evacuation rates by altering the engraved texture shapes on the rollers. The proposed methodology is also applicable to other contact-based printing systems and broader applications involving FSCIs.