This paper investigates the influence of the main process parameters on the geometry of the bead deposited during WAAM using MIG welding technology. A campaign of experimental tests was conducted using a design of experiments approach. The campaign was conducted under a wide range of processing conditions up to a deposition rate of 22 kg/h. Geometrical characterization of the weld bead was performed by optical microscopy and 3D reconstruction techniques. The key geometrical features of the beads and suitable processing windows were identified. The experimental measurements of the cross-sectional profile of the weld bead were compared with common approximation models. A new model based on a circular approximation was proposed. The results demonstrated that the circular approximation showed better agreement with the experimentally measured profiles than the commonly adopted parabolic approximation. This commonly adopted model was fully unable to describe the weld bead profile under medium–large deposition rates. Under these conditions, the parabolic approximation predicted taller and larger weld bead profiles as compared to the experimental measurements. On the other hand, the circular profile showed much better agreement with the experimental profiles within the entire experimental window. A semi-empirical model capable of predicting the bead cross section given the deposition parameters was developed. The model showed good reliability and agreement with the experimental measurement. Consequently, this model would represent a compelling tool to select the process parameters to achieve more precise geometries during WAAM processes.
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