Inproceedings,

Evaluation and Reduction of Elevated Height Printing Defects

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Digital Fabrication and Digital Printing: NIP30 Technical Program and Proceedings, page 38–43. (2014)

Abstract

Ink jet printing at elevated heights is known to initiate unsteady laminar flows which lead to imaging defects often referred to as wood-grain or fogging. An investigation of the unsteady flow development was c onducted using both experimental and numerical simulation tec hniques. High speed imaging revealed that the interaction be tween the air flow induced from droplet drag and the couette flow entrained from the substrate motion develops large eddies which roll along the droplet stream and lead to unsteady flows causi ng wood-grain defects. ANSYS CFX computational fluid dynamics (CFD) simulations are presented to support the experim ental results and to provide a higher degree of understanding of the flow dynamics. Several techniques are revealed which illu strate how wood-grain defects can be improved. These techniques strive to enable ink jet technologies to be used in a wider range of applications with large height variations or which requi re jetting at elevated heights to prevent contact with print heads. In addition to unsteady flow de fects, two other phenomenons related to elevated height printing were included in this study: (1) excessive nozzle plate wetting and (2) excessive drag on droplets ejected into a still flow field.

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  • @gdmcbain
    5 years ago (last updated 5 years ago)
    Not sure that I believe the steady state no-printing flow predicted by ANSYS-CFX in figure 14.
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