Improved surface finish in 3D printing using bimodal powder distribution

The use of bimodal powders has been shown to offer the possibility of dramatically improved surface finish in 3D printing. This work focused on individual lines, the primitive building block of 3D printed parts. It was observed that the fine component of bimodal ceramic powders, while uniformly distributed in the original powderbed, was preferentially found at the surface of the printed line, while the interior of the line was denuded of fines. Microscopic examination and approximate quantitative analysis supports the assertion that essentially all the fines have moved to the surface of the line. The mechanism for this rearrangement is not known, but is speculated to be related to the relative difficulty of wetting fine powders. The parameter space in which this phenomenon can be observed was examined in a preliminary manner.