Aerodynamic effects in ink-jet printing on a moving web

The airflow between the fast-moving substrate and stationary print heads in a web print press may cause print quality issues in high-speed, roll-to-roll printing applications. We have studied the interactions between ink drops and the airflow in the gap between the printhead and substrate, by using an experimental flow channel and high-speed imaging. The results show: 1) the gap airflow is well approximated by a standard Couette flow profile; 2) the effect of gap airflow on the flight paths of main drops and satellites is negligible; and 3) the interaction between the gap airflow and the wakes from the printed ink drops should be investigated as the primary source of aerodynamically- related print quality issues. ©2012 Society for Imaging Science and Technology.

Evidence of print gap airflow affecting web printing quality

The current study extends our earlier investigation on the real-time dynamics of print gap airflow around a single jetted drop over a moving substrate. In the present work, simulated web press printing was performed using a stationary grey-scale commercial inkjet print head to print full-width block of solid colour images onto a paper substrate with extended print gaps. The resultant printed images exhibit patterns or 'wood-graining' effects which become more prevalent as the relevant Reynolds number (Re) increases. The high-resolution scans of the printed images revealed that the patterns are created by oscillation and coalescence of neighboring printed tracks across the web. The phenomenon could be a result of drop stream perturbations caused by unsteady print gap airflow of the type similar to that observed in the previous study. ©2013; Society for Imaging Science and Technology.