Finishing of metal additive manufactured parts by abrasive fluidized bed machining

A characteristic of metal additive manufactured (AM) components fabricated by Laser Powder Bed Fusion process (L-PBF) is the texture of the surface, primarily originated by melting and solidification of the powder material. This mechanism leads to an average surface roughness of 8-25 μm, depending on the material properties and process parameters. In some applications, AM parts require a surface smoothing process to meet part specifications. Conventional finishing processes may not be appropriate to finish the complex geometries that are typical of AM products, such as deep cavities and intricate through holes. Abrasive fluidized bed (AFB) machining is a recent finishing process developed at the University of Rome Tor Vergata that employs an abrasive fluidized bed to improve surface finish by material erosion. This work aims to explore the capability of the AFB method as finishing method for AM products. Thus, a specimen with curved surfaces and internal holes was designed and several copies were produced by L-PBF process. The samples were then subjected to the AFB surface finishing treatment. The influence of the operational parameters on the finishing performance was investigated. The achievable surface roughness and the deviations of the part geometry induced by the finishing process were identified by dimensional and surface inspection. From the inspection results, it was possible to assess the effectiveness of the process and to identify capabilities, limitations and possible improvements.