Digital metal printing by in-flight melting of individual microparticles

Abstract

Additive manufacturing (AM) of metal components has the potential to impact an immense range of applications and industries, but each metal AM process has key capabilities and limitations that will define its ultimate industrial uses. Most commonly, 3D metal parts are fabricated layer-by-layer by the deposition and selective binding or melting of metal powders. However, this does not easily allow for multimaterial printing or printing directly onto existing objects, and achieving fine surface finishes is challenging. By contrast, current methods to directly print metal parts are low resolution (e.g., directed energy deposition), or cannot achieve bulk metal properties (e.g., ink-based methods). In this thesis, a novel high resolution direct metal printing method is presented, wherein individual metal microparticles are electro-hydrodynamically ejected on-demand from a water meniscus and subsequently laser-melted in-flight before landing and solidifying on a substrate. The processing window for this method in terms of feasible materials and particle sizes is explored, and results from particle-printing experiments performed with solder and platinum particles ranging from 30-150 [mu]m in diameter are presented. Analysis of the relevant fluids and heat transfer phenomena is presented alongside the experimental results, revealing the in-flight melting and droplet deposition regimes that may be accessed with this process. Metallurgical characterization of printed droplets is discussed, and 2D patterns are printed to demonstrate how digital printing of molten metal particles may enable the production of complex, high-quality features and components.