An image-processing approach for polishing metal additive manufactured components to improve the dimensional accuracy and surface integrity

Metal additive manufacturing (MAM) process has gained enormous popularity in the past few decades due to its capability to fabricate the components in near-net-shape with minimal material wastage. Owing to its flexibility to produce complex/intricate shapes, the process has found several applications in the aerospace, automobile and biomedical industries. However, wide industrial acceptance of the MAM components is lagging because of their poor dimensional accuracy and surface integrity which limits the functionality and achievable tolerances when compared to the subtractive manufacturing methods. Thus, a post-processing strategy is needed to enhance the dimensional accuracy and surface integrity of the additive manufactured components. Manual inspection of various features, especially corner profiles, can be expensive, time-consuming and inaccurate. Ti6Al4V alloy has wide applications in aerospace, biomedical and marine industries due to its superior properties like strength-to-weight ratio, biocompatibility and fatigue resistance. This article presents an image-processing approach for improving the corner accuracy and surface integrity of selective laser-melted (SLM) Ti6Al4V components using wire electric discharge polishing (WEDP). Subsequently, fourteen components with different corner profiles, namely acute (theta = 30 degrees), orthogonal (theta = 90 degrees) and obtuse (theta = 120 degrees), were fabricated by varying laser power, hatch distance and scan speed. Minimum polishing depth has been evaluated by capturing the raw images of MAM components, and the corner profiles are extracted using an image-processing approach. A significant improvement in dimensional accuracy of 80.7%, 77.3% and 85.4% was obtained for orthogonal, acute and obtuse profiles respectively after WEDP. Moreover, the surface roughness (S-z) reduction from similar to 61.86 to similar to 8.41 mu m was achieved along with removing micro-pits and voids, waviness and balling defects from the surface. EDS analysis showed that only a negligible amount of Zn (0.57 wt. %) and Cu (0.8 wt. %) is present over the finished surface. Based on the above findings, WEDP showed excellent capabilities in conjunction with an image-processing approach to enhance the dimensional accuracy and surface integrity of metal additive manufactured components.