(328a) Characterization of Polymeric Powders through Capillary Flow for Additive-Manufacturing Techniques

Binder jetting is an additive-manufacturing (AM) method that deposits a liquid binding agent onto a powder surface in a layer-by-layer fashion to form a solid part from a computer-aided-design (CAD) file. Powders that are utilized in AM include polymers, sands, and metals [1]. The production of parts requires input materials to have quantifiably repeatable characteristics and properties, which then requires standardized methods of characterization for powders [2]. In this investigation, we use a non-invasive frugal imaging technique to characterize fluid flow in a packed powder bed to investigate fluid-powder interactions at elevated temperatures. Laser-diffraction particle size and sieve analysis are used for size and shape analyses, as well as scanning electron microscopy (SEM) to investigate the surface topography. The results of this study demonstrate how particle size, size distribution, particle shape, surface roughness, and surface chemistry affect the packing density and therefore the binder-jetting process. The frugal technique that is presented in this study, which can be conducted only with a camera, an oven, and a commercially available microfluidic cell, offers a more affordable option to Washburn capillary rise method. As shown in figure, the trends from the preliminary experiments with the novel technique and the Washburn capillary rise method overlaps, which indicates that the novel technique is promising.

This study investigates the interactions of the polymer powders with fluids at the fundamental level. Results will aid in the understanding of other AM methods (e.g., cold spraying, drop on demand (DOD), selective laser sintering (SLS), electron beam melting (EBM)), which use polymer powders. Since this study uses a frugal technique, which requires only a mobile phone and a flow cell to analyze the fluid-powder interactions, characterization of the properties of any polymer powder is readily available to all industries [3].

References

[1] Prashanth Konda Gokuldoss, Sri Kolla, and Ju ̈rgen Eckert. Additive manufacturing processes: Selective laser melting, electron beam melting and binder jetting – selection guidelines. Materials, 10(6):672, 2017.

[2] Yun Bai, Grady Wagner, and Christopher B Williams. Effect of particle size distribution on powder packing and sintering in binder jetting additive manufacturing of metals. Journal of Manufacturing Science and Engineering, 139(8), 2017.

[3] Katrina J. Donovan. Microfluidic Investigations of Capillary Flow and Surface Phenomena in Porous Polymeric Media for 3D Printing. PhD thesis, Oregon State University, Corvallis OR, 2019.