Direct-to-shape printing demands a high drop placement accuracy, such that the drop placement is still acceptable at larger throw distances (> 1 mm). In this study, the influence of the nozzle shape on the drop placement accuracy has been investigated. Experiments were conducted employing a series of prototype Xaar 126 printheads fitted with a silicon nozzle plate, with various nozzle taper angles. The results presented in this study show that a larger nozzle taper angle improves the drop placement accuracy; that is, when the printhead is operated at a drive voltage required to have a drop velocity of 6 m/s. The required drive voltage is reduced due to the increased nozzle efficiency associated with a larger nozzle taper angle. A lower drive voltage is likely to be the underlying reason for a smaller drop-to-drop velocity variation, which in turn results in an improved drop placement accuracy. An even better drop placement accuracy is obtained when the drive voltage is increased to give a larger than typical drop velocity (of upto 10.3 m/s), but this also causes the formation of satellite drops reducing the overal print quality.
Renzo Trip, Nick Jackson, Felix Steinchen, Volker Till, Werner Zapka, "Direct-to-shape: Increasing the throw distance" in Proc. IS&T Printing for Fabrication: Int'l Conf. on Digital Printing Technologies (NIP34), 2018, pp 215 - 220, https://doi.org/10.2352/ISSN.2169-4451.2018.34.215