The effect of process condition of the ink-jet printing process on the molten metallic droplet formation through the analysis of fluid propagation direction

Abstract

This study investigated the droplet formation mechanism using simulation analysis under various process conditions of ink-jet printing. Experimentally, the droplet shapes were cataloged in four types with the dwell time of the mono-polar waveform, and used to verify the reliability of the numerical model by finding consistency with the simulated modes of droplet formation. Conventional droplet formation depiction using pressure variation has not been comprehensive; as such, fluid propagating velocity was used to discuss the droplet formation mechanism in this study. Through the analysis of the fluid propagation velocity, a sufficient outward momentum of the fluid at the nozzle and a pulling force to pinch off the liquid thread were found to be essential for generating a single droplet. An insufficient pulling force would lead to undesired droplet shapes. A bipolar waveform can be used to enhance the outward momentum and the pulling force of the fluid, and the improvements in droplet formation were revealed in both the simulation and experiment. Results demonstrate that the analysis from the velocity variation is a useful and essential method when evaluating the droplet formation mechanism.