Geometric modeling of overlapped WAAM beads by Hermite curves

Purpose – In Wire Arc Additive Manufacturing, the size and shape of the deposited material are affected by heat input, material deposition rate, orientation with respect to gravity, substrate conformation and the sequence of beads. The paper aims to investigate the geometric behavior of adjacent overlapping beads and proposes a model to predict the shape assumed in case of multiple beads deposition according to the succession of accumulation. Design/methodology/approach – Geometric curves such as parabolas, circular arcs, cosines and ellipses have been proposed in the literature to represent the resulting cross-section bead profiles, even though multiple beads deposition scenarios have been scarcely explored and, in most cases, restricted to simplified situations, such as planar substrates. Therefore, a generic geometric model for the bead profile based on a closed curve composed of two Hermite spans is proposed. Findings – The algorithm reliability was tested on circular specimens realized with a Fronius TPS 320i welding generator and on a set of documented cases from the literature. The results demonstrate that the Hermite curve-based model and the proposed algorithm can accurately reproduce various bead profiles in multi-bead and multi-layer deposition sequences. Originality/value – Thanks to the positioning of its control points, the Hermite curve exhibits the necessary variability in bead height, width, shape and contact angles with the substrate, offering greater flexibility in geometric approximation compared to existing models. As a further contribution, the devised algorithm enables the prediction of the shape of complex combinations of deposition according to process parameters.