Physics-based model for dot geometry prediction in dot-by-dot wire arc additive manufacturing

Dot-by-dot is an emerging Wire and Arc Additive Manufacturing (WAAM) technology, allowing for the precise deposition of tiny spheres of molten material, to form slender bars that could be used to manufacture complex lattice structures. Dots’ geometry plays a key role in determining both the welding torch optimal toolpath and the mechanical properties of the final product. In this paper an analytical physics-based geometrical model is presented, capable of predicting the geometric characteristics of dot-by-dot additively manufactured bars from the properties of the feedstock material, the welding process parameters and interpass temperature. The proposed model is based on heat transfer and mass conservation and can be applied to different scenarios and materials, being more general with respect to experimental-regressive approaches. A preliminary experimental validation on ER70S-6 steel bars was performed on different case studies, showing fair accuracy in predicting bars diameter and height.