Abstract: Multi-bead overlapping process of wire and arc additive manufacturing (WAAM) based on the cold metal transfer (CMT) is studied systematically. By using 2319 aluminum wire as the filling material, experiments are carried out with the constant wire-feed rate and various travel speeds. The cross section's morphology of the obtained single beads are separately fitted by the three selected models, including the parabola model, arc model and cosine model. The experimental results showed that both the parabola and arc functions could accurately represent the bead profile. Based on parabola model, the single-layer multi-pass overlapping model is then established. The theoretical optimal overlapping width is calculated to be 0.715 times that of the layer width. To verify the accuracy of this model, single-layer two-bead samples are produced with different overlapping rates, including the traditional flat-topped overlapping rate 0.6. The experimental results showed that the model proposed is more in line with the manufacturing process of WAAM based on the CMT. When the overlapping rate is determined, the smaller the single-layer height is, the better would the formed surface profile be, which is propitious for the subsequent multi-layer multi-bead parts fabricating. Based on the optimized overlapping parameters, the multi-layer multi-bead part was fabricated with good surface appearance. And the mechanical properties in three directions are analyzed as well.

Key words: CMT (cold metal transfer), additive manufacturing, overlapping model, multi-layer multi-bead