Large drop volumes from Xaar printhead

WO 2014/023981 A1
Droplet deposition apparatus and method for depositing droplets of fluid
Xaar Technology Limited

The Xaar face shooter architecture with through flow ink circulation has been very successfully commercialised in the 1001 printhead. This patent application discusses some improvements, in particular using a different shaped nozzle to allow larger drops to be generated on the same nozzle pitch.

Feb-14In the Xaar design the piezo walls 3 move to reduce the channel volume 2 to create pressure waves to generate drops. The ink is continuously circulated through the channels, as shown by the arrows, at a rate around an order of magnitude greater than the flow through the nozzles at maximum drop frequency. Attempts to elongate the nozzle in the flow direction were found to allow more efficient removal of debris from the vicinity of the orifice. In addition the effciency of drop ejection increased due to the acoustic wave being present at the orifice for longer.

However, the directional accuracy of drops deteriorated in the direction of the elongation when the nozzle was made elliptical. Experiments showed that the benefits of elongation could be retained just by elongating the inlet side. If the outlet (orifice) was circular, or up to an aspect ratio of 1.2, then the directionality of drops was similar in all directions.

Feb-14bBy increasing the nozzle area through elongation then the drop volume ejected increased as shown in the table on the left. Larger drop volumes are desirable for some applications, such as printing of ceramic tiles, one of the main applications for the 1001 printhead.