Overlapping model of beads and curve fitting of bead section for rapid manufacturing by robotic MAG welding process

As a deposition technology, robotic metal active gas (MAG) welding has shown new promises for rapid prototyping (RP) of metallic parts. During the process of forming metal parts with the robotic MAG welding technology, the sectional geometry of single-pass bead and the overlap of the adjacent beads have critical effects on the dimensional accuracy and quality of metal parts. In this work, Canny edge detection of the robotic MAG beads was carried out and the data were smoothed with a Gaussian filter and fitted with Gaussian function, logistic function, parabola function and sine function, respectively. In addition, a mathematical model of bead section was developed to analyze the bead geometry. Based on ''surfacing of equivalent area'' method, the concept of overlapping coefficient and optimum-overlapping coefficient was put forward, and calculated model of overlapping was analyzed. Optimal overlapping coefficient was calculated to be 63.66% under experimental condition. The conclusion is that the edge detection of bead section with Canny operator is continuous and distinct, and as compared with Gaussian function, logistic function and parabola function, sine function has higher accuracy to fit the measured data, and ''surfacing of equivalent area'' method shows to be rational and feasible by the experiments.