S. Vader, Z. Vader, I.H. Karampelas, E.P. Furlani
University at Buffalo, SUNY,
Keywords: magnetohydrodynamics, drop-on-demand printing, DOD printing, printing molten metal droplets, 3D printing of molten metal, additive manufacturing, induction heating
Summary:At present, most metal 3D printing applications involve deposited metal powder sintering or melting under the influence of an external energy source such as a laser (e.g. Selective Laser Sintering (SLS)  and Direct Metal Sintering (DMLS)  or an electron beam (e.g. Electron Beam Melting (EBM) ) to form solid objects. One of the potential disadvantages of such methods could be the increased energy cost of powderizing the metal in advance of the 3D printing process. Drop-on-demand (DOD) inkjet printing is a mature technology for commercial and consumer image reproduction. However, it currently has entered a third wave of technology development which includes the application of inkjet printing principles in additive manufacturing. We propose a novel method of DOD 3D printing that involves the formation of solid objects via molten metal droplet coalescence. We call this process MagnetoJet Printing (MJP). The MJP method consists of the use of heating to pre-melt a solid metal structure (e.g. commodity metal wire) to form a reservoir of liquid metal that feeds a nozzle chamber. Once the chamber is filled, a pulsed magnetic field is applied that permeates the chamber and induces a magnetohydrodynamic (MHD)-based pressure pulse within the metal that causes it to be ejected out of the nozzle. Consequently, the ejected metal forms into a droplet due to surface tension and has a drop velocity in the range of several meters per second, the magnitude of which depends on the applied pressure. The droplet is projected onto a substrate where it cools to form a solid mass. 3D solid structures may be formed through dropwise solidification [4, 5]. With our current work, we present a prototype printing system and sample printed structures. We discuss the underlying physics governing the 3D printing process and introduce a combination of computational electromagnetic and thermofluidic CFD models for evaluating device performance in the areas of droplet generation, fluid ejection, droplet impact and subsequent molten material solidification using various metals.