Numerical investigation of the influence of companion drops on drop-on-demand ink jetting

In this study we characterized and investigated the specific phenomenon of “companion drops” in the drop-on-demand (DOD) ink jetting process. A series of simulations based on a piezoelectric DOD printhead system is presented, adapting the volume-of-fluid (VOF) interface-capturing method to track the boundary evolution and model the interfacial physics. The results illustrate the causality between the generation of companion drops and droplet deviation behavior, as well as their close correlations with ink jetting straightness and printing accuracy. The characteristics of companion drops are summarized and compared with those of satellite drops. Also, a theoretical mechanism for the generation of companion drops is presented, and their effects and behaviors are analyzed and discussed. Finally, the effects of critical factors on the generation of companion drops are investigated and characterized based on variations in the printable pressure range. Recommendations are given for the suppression of companion drops and for the improvement of printing accuracy.