In order to support increased viscosities and particle sizes without decreasing reliability and print consistency, head architectures have had to change significantly.
In contrast with earlier “end-shooter” nozzle designs, consisting of rows of tubes with a single nozzle opening at the end of each tube, TOSHIBA TEC’s CF range of heads use a “side-shooter” design, in which the nozzle openings are part way along a side wall of the ink channels. This design allows ink or other fluids to be circulated constantly through all channels, even when the nozzles aren’t firing.
Through-channel ink recirculation prevents particle sedimentation, allowing even the larger particles to be jetted successfully. Any temporary nozzle blockages auto-recover without the need to halt the printing process for a cleaning cycle.
Absence of sedimentation around nozzles ensures that ink droplets are ejected “cleanly”, without unwanted deflection angles. Air bubbles, which would otherwise tend to accumulate around nozzle openings, are swept away, ensuring uninterrupted jetting.
The recirculation process also allows ink to be passed through a conditioning unit, where optimum ink temperatures and consequent viscosity levels can be maintained accurately, resulting in consistent droplet form and volume.
The increased printing reliability and consistency of side-shooter heads makes them preferable to end-shooters in industrial inkjet printers, especially for single-pass applications. Their reliability reduces substrate wastage and press down-time.