Enhanced curve-fitting model of the bead section profile and the corresponding overlapping model for twin-electrode gas tungsten arc–based additive manufacturing

Twin-electrode gas tungsten arc–based additive manufacturing (GTA-AM) is a developing wire and arc additive manufacturing (WAAM) method. The bead geometries of twin-electrode GTA-AM are various compared with that of traditional single arc-based WAAM methods. Three widely used curve models (i.e. parabola, cosine, and circular arc) cannot predict its bead section profile well, which leads to poor process stability and geometry accuracy. To overcome this problem, the geometric characteristics of the twin-electrode GTA-AM bead section profile were researched firstly. An enhanced fitting-curve model, namely the power-function-curve model was presented to fit the bead section profiles. Its exponential parameter determined the plumpness of the fitting curve, which was ignored in traditional models. For the multibead overlapping issue, the operating condition of the tangent overlapping model (TOM) was extended to the proposed power-function-curve-shaped bead section profile. The deducing procedure of the optimal overlapping coefficient was elucidated. The results of verification experiments proved that the proposed curve-fitting model and overlapping model can accurately predict the bead overlapping behavior and the maximum error is less than 6%. These models are critical in the process planning of twin-electrode GTA-AM.