Mechanism and technology evaluation of a novel alternating-arc-based directed energy deposition method through polarity-switching self-adaptive shunt

Directed Energy Deposition-Arc (DED-Arc) are dedicated to large parts manufacturing. To satisfy the thermal force and mass requirements while utilizing the physical characteristics of the arc electrode, a mechanism and technology for alternating-arc-based additive manufacturing is proposed through a polarity-switching self-adaptive shunt (PSSAS). Experimental results show that on the two parallel branches, the current can only alternately flow through the welding wire or the substrate. The arc burns alternately between the combination of “welding wire - tungsten electrode” and “tungsten electrode - substrate”, forming an electronegative arc with the wire as the anode and an electropositive arc with the substrate as the cathode. The decoupling control of thermal force and mass transfer can be achieved by EN arc (tungsten electrode negative, wire positive) to control the melting of the wires and size and temperature of droplets, EP arc (tungsten electrode positive, substrate negative) to control the cathode cleaning and molten pool temperature. When the deposition velocity is 5.7 mm/s and the wire height is 8 mm, the molten drops exhibit a frequency of one pulse per drop, which will produce well weld quality with minimal defects and spatter. The dilution of the deposited layer reaches 0.05 and the width-to-depth ratio is 17.47 with these parameters. The proposed method reduces the heat input to the base metal and improves the heat input to the wire compared with conventional processes, resulting in better melting efficiency. Thus, PSSAS provides a new theory for high-precision and high-efficiency additive manufacturing.