Additive Manufacturing With Metallic Wire Using an Coaxial-Fed Microwave Plasma Jet

The first additive manufacturing process at atmospheric pressure using a coaxial microwave (MW) plasma jet at 2.45 GHz is presented in this article. The wire is transported coaxially through the hollowed electrode, directly into the hottest area of the plasma at the tip of the electrode. The topology of the jet is presented along with a detailed description of the process. The jet is combined with a standard 3-D printing kinematic for a triaxial nozzle manipulation. A custom wire feeder prototype is constructed using a stepper motor. For the experiments, a test stand is built, including the programming of a custom software to control the MW amplifier, the gas flow controllers, the
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movements, and the wire feeder. Investigations with a high-speed camera reveal the cause of sparks originating from the formation of a molten metal sphere at the tip of the wire. A process is developed to compensate this effect. In addition, an image processing software is programed to observe the metal sphere and optimize the drop creation. Modifications on computer-aided manufacturing (CAM) data are automatically generated to create the 3-D models. Experiments with single dot are presented on different metallic substrates as well as a print of a melting track on a steel substrate. An analysis of the printed dots using micrograph imaging is also presented.