Satellite-free droplet formation in material jetting via rheology-driven waveform modelling approach

Stable, satellite-free droplet ejection is essential for high-resolution material jetting (also known as 3D inkjet printing). Existing “printability windows” often fail to predict satellite formation accurately, as they neglect non-Newtonian fluid behaviour and waveform dynamics. This study presents a fast-track, experiment-driven approach to identify single-droplet waveform parameters, namely pulse width and driving voltage, from rheological data of polymer inks across different jetting temperatures, eliminating tedious drop-watching trials. Three UV-curable acrylate inks are systematically characterized for complex viscosity, viscoelasticity, relaxation time, dynamic surface tension, oscillation and damping behaviour, and density at five temperatures using a high-frequency squeeze-flow rheometer and bubble tensiometer. Cross, Hua & Rosen, Maxwell, Arrhenius, and Eötvös models are applied to extrapolate these properties to the inkjet regime (∼10$^5$ s$^{−1}$ shear rate, <1 ms surface age). A correlation between droplet velocity and driving voltage, dependent on material properties, is established. Satellite formation is governed almost exclusively by droplet velocity, with distinct regimes: <3 m/s (no satellite), 3–3.8 m/s (one satellite). ... mehrA general equation quantifying the relationship between droplet velocity and driving voltage enables predictive waveform design from rheological data. The methodology, validated with two UV-curable inkjet inks, accelerates the search for a satellite-free single droplet waveform.