Machinability of wire and arc additive manufactured components

Abstract

Wire and Arc Additive Manufacturing (WAAM) aims to be a cost-effective and material-efficient process to produce medium and large-scale metal parts. Nevertheless, post-processing is still required due to the low quality of the as-deposited surface. With the objective to divulge the complex interaction between the welding and machining phenomena, which determines the final surface quality, this paper focuses on the machinability of WAAM parts through a comprehensive investigation on the key parameters of both additive and subtractive processes. The effect of the WAAM parameters on the as-deposited part characteristics (i.e., hardness, flatness deviation, wall thickness, and initial surface waviness) and machining process has been analyzed. Consequently, the first of its kind, a non-linear function that can predict the effect of welding and milling parameters on the final surface roughness, is presented. The complex interaction between the local (e.g., surface irregularities and hardness) and global (e.g., wall thickness) effects of welding heat input and the resulting impact on the machining stability is analyzed. For example, slow welding speed results in a soft and irregular surface that is not easy to machine. Still, at the same time, the slow speed increases the wall width that provides the essential damping to reduce the chatter during machining. The obtained results help understand the interactions between the WAAM and milling processes and further determine the optimal machining allowances and optimal process conditions.