Orthogonal Cutting of Wire and Arc Additive Manufactured Parts

Abstract

Wire and Arc Additive Manufacturing (WAAM) is increasingly being used to produce complex and non-traditional geometries that other technologies are not able to create. Finishing operations, as machining, are often required to accomplish the components functionality. However, recent studies suggest that several machining issues arise due to the lack of geometrical tolerances and complex shapes of the manufactured parts, like chattering effects, appropriate work holding selection and component alignment. This work aimed to evaluate if the established scientific knowledge for machining homogeneous and isotropic materials remains valid for machining WAAM parts. Two different variants of WAAM were analysed, namely, conventional MIG/MAG and hot forging (HF-WAAM). The cutting operations were carried out varying the undeformed chip thickness (UCT) and the cutting speed, using a tool rake angle of 25°. A systematic comparison was conducted between the existing theoretical principles and the obtained practical results of the orthogonal cutting process, where material properties (hardness, grain size, yield strength) and important machining outcomes (cutting forces, specific cutting energy, friction, shear stress, chip formation and surface roughness) are addressed. Additionally, high-speed camera records were used to evaluate the generated shear angle and chip formation process during the experimental tests. The machinability indicators shown that, through the appropriate cutting parameters, machining forces and energy consumption can be reduced up to 12%, when machining the mechanical improved HF-WAAM material, without compromising the surface quality requirements.