Melting behavior and forming control of bypass-coupled variable polarity plasma arc additive manufacturing

This study presents a new bypass-coupled variable polarity plasma arc additive manufacturing process for aluminum alloys. It can independently control the main current and bypass current as well as the polarity to achieve independent control of the melting of the deposition layer and the melting of the wire, and at the same time, the variable polarity can clean up the oxide film on the surface of the aluminum alloy to achieve high-efficiency arc additive manufacturing of aluminum alloys. The experimental results show that the droplet transition is different for different wire heights. Complete bridging transfer yields high forming quality in a wide deposition parameters range. Furthermore, changes in the bypass current polarity induce periodic variations in the magnetic field within the coupled arc region, which influences the arc behavior and droplet transfer during the additive manufacturing process. The study delves into the impact of main and bypass EN/EP currents on the deposition layer. The influence of the main EN current on the deposition layer width is twice that of the bypass current. Precise control over forming morphology is realized through the regulation of main EN currents. This study demonstrates the potential of this process to achieve lower heat input and forming control while improving deposition efficiency.