Comparison of two controlled short arc variants for WAAM of mild steel parts

A wide selection of electronically controlled process variants (PV) is available for gas metal arc welding. Wire arc additive manufacturing (WAAM) typically uses controlled short arc variants because they provide low heat input and stable deposition characteristics. The control methods, such as specific current waveform or wire retraction, vary between manufacturers. The geometry and material properties of WAAM-parts are contingent on the welding process and, consequently, the underlying algorithms of controlled short arc variant. Currently the knowledge regarding the advantages and disadvantages of controlled short arc variants is limited to specific applications. The aim of this research is to provide a more fundamental approach for the selection of PV for WAAM applications. Six walls out of mild steel, each approximately 5 mm wide, are additively manufactured using three different torch angles and two different PV. By utilizing current and voltage measurements in conjunction with high-speed imaging, the characteristics of the controlled short arc variants are investigated. For PV1, the lowest thickness variation is 0.22 mm at a torch angle of 0°. For PV2, the lowest thickness variation is 0.28 mm at a forward torch angle of 10°. The range between shortest and longest arc times, which is dominated by outliers, is smallest for PV1 at 0° with 1.92 ms and for PV2 at 10° with 2.34 ms. Surface errors such as uneven layer height and instances of material overflow correlate with the delta. This finding is corroborated by observations of melt pool behavior from high-speed recordings.