An experimental study was performed to understand the atomization process in the specialized printing method which consists of the high frequency oscillating motion of a needle and a micro air jet. Highly viscous liquids, such as glycerin and acrylic paint were successfully printed with this printing method within the line width of 1 mm. High-speed imaging technique was used to observe the evolution and mechanical perturbation of a liquid meniscus which is coated on the oscillating needle. Various parameters which affect print patterns were identified to understand and control the atomization process occurring at the oscillating needle. For time-controlled atomization or printing, a pulse air jet system was implemented to print liquids only when it is demanded, and it was shown that the period of atomization can be controlled by the air jet on-and-off. The inertial coating process was studied to explain the dynamic meniscus profile, compared with static meniscus. Kinematic analysis of the needle motion was performed, which shows that the needle motion is a sinusoidal one undergoing inertial coating. Liquid sheet breakup mechanism in the presence of the air stream was also studied in conjunction with the principle of the air- blast atomizer. Performing as a printing device or a droplet generator, the reciprocating needle printing method studied here can be applied to printing or coating processes which utilize high viscosity media.
展开▼
