Abstract
Capillary-driven ink infiltration through a porous powder bed in three-dimensional (3D) binder jet printing (inkjet printing onto a powder bed) controls the printing resolution and as-printed “green” strength of the resulting object. However, a full understanding of the factors controlling the kinetics of the infiltration remains incomplete. Here, high-resolution in situ synchrotron radiography provides time-resolved imaging of the penetration of an aqueous solution of eythylene glycol through a porous alumina powder bed, used as a model system. A static drop-on-demand inkjet printer was used to dispense liquid droplets onto a powder surface. The subsequent migration of the liquid front and its interactions with powder particles were tracked using fast synchrotron X-radiography in the Diamond Synchrotron, with phase-contrast imaging at a frame rate of 500 Hz. Image processing and analysis reveal that both the time-dependent increment in the wetting area and the propagation of the “interface leading edge” exhibit heterogeneous behavior in both temporal and spatial domains. However, mean infiltration kinetics are shown to be consistent with existing infiltration models based on the Washburn equation modified to account for the spreading of the liquid drop on the powder surface and using a modified term for the bed porosity.
Highlights
In the last 2 decades, the field of additive manufacturing has witnessed rapid advancement in various sectors, encompassing prototype modeling, for structural, aerospace, defense, and healthcare applications.[1−6] Layer-by-layer manufacturing of individual sections or slices, derived from a three-dimensional (3D) computer-aided design (CAD) model of the object to be fabricated, is a generic feature for all of the current variants of additive manufacturing.[7−9] One such method, 3D binder jet printing, uses inkjet printing to selectively deposit drops of an adhesive or binder ink onto a leveled powder bed
We have demonstrated that high-resolution, time-resolved X-radiography can be used to acquire real-time data of the penetration of fluids into a powder bed
Ray imaging to carry out a time-resolved study of capillarydriven ink infiltration of powdered materials mimicking the processes that occur during 3D binder jet printing
Summary
In the last 2 decades, the field of additive manufacturing has witnessed rapid advancement in various sectors, encompassing prototype modeling, for structural, aerospace, defense, and healthcare applications.[1−6] Layer-by-layer manufacturing of individual sections or slices, derived from a three-dimensional (3D) computer-aided design (CAD) model of the object to be fabricated, is a generic feature for all of the current variants of additive manufacturing.[7−9] One such method, 3D binder jet printing, uses inkjet printing to selectively deposit drops of an adhesive or binder ink onto a leveled powder bed. To ensure adequate binding between adjacent droplets and to define the spatial resolution attainable by this method, it is necessary to understand and predict the kinetics of the penetration of the liquid through the powder. Multiphase flow in porous media is a significant research area in hydrology, oil recovery, and geosciences, where a number of in situ and ex situ experimental investigations have studied the flow patterns and liquid interface evolution through solid porous media.[18−20] compared to 3D binder jet printing, similar length scales of droplets and powder particles may lead to different underlying mechanisms from prior studies in geosciences and hydrology
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