Magnetically driven internal finishing of AISI 316L stainless steel tubes generated by laser powder bed fusion

Internal surfaces generated by additive manufacturing (AM) are finding their wide applications in aerospace, automobile, and medical industries. Nevertheless, the poor surface quality resulting from the intrinsic melting and solidification process of laser powder bed fusion (L-PBF) is still a common issue for the full functionality of the fabricated components. Though conventional abrasive-based and chemical-based finishing methods have been recently deployed to improve the surface finish of the AM-ed internal surfaces, they may have limitations and unresolved issues such as low material removal rate, uneven removal and chemical hazards. In this study, magnetically driven internal finishing (MDIF) with magnetic polishing tools is developed to finish the AISI 316L stainless steel tube printed by selective laser melting (SLM), one of the most typical L-PBF processes. Results demonstrate that the surface roughness in single-point polishing and section-polishing experiments can be reduced from the as-printed level of 11.599 μm Ra to 0.385 and 0.808 μm Ra, respectively, within tens of minutes of polishing time. Benchmarking experiments with conventional magnetic abrasive finishing (MAF) shows that the MDIF outperforms MAF in terms of both the final surface finish and efficiency. Besides, a material removal model based on the Abbott-Firestone curve is developed to predict the material removal in mass for the SLM-ed workpiece and the average predicting errors are only 7.9% and 13.4% in the single-point polishing experiment and section-polishing experiment, respectively. This paper provides an efficient alternative to the existing surface finishing methods addressing the poor surface finish of L-PBF internal surfaces. © 2022 The Society of Manufacturing Engineers.