Effect of Tumbling on Surface Finish and Wettability of Additively Manufactured 316L Stainless Steel Alloy

Additive manufacturing inherently produces surface roughness due to its layer‑by‑layer fabrication, with roughness severity influenced by part geometry. This study evaluates how variations in the tumbling process affect the surface roughness, wettability, and geometric accuracy of stainless steel 316L components produced via Bound Metal Deposition (BMD). Two tumbling media shapes (spherical vs. triangular prism) and tumbling durations (2 and 4 hours) were used as control variables. Surface characterisation was performed using laser confocal microscopy, scanning electron microscopy, and contact angle measurements. The efficacy of tumbling was compared and discussed in relation to that of the as-printed specimen. Results showed that spherical ceramic media produced the greatest surface refinement, reducing area roughness S_a from 12.94 µm to 1.50 µm after 4 hours through plastic deformation and valley compaction. Triangular prism media yielded moderate improvements via abrasive cutting, with diminishing returns over time. Wettability increased significantly following tumbling, particularly with spherical media, which reduced the contact angle from 91.84° (hydrophobic) to 31.40° (hydrophilic). SEM analysis confirmed smoother surfaces and reduced layer‑line visibility with spherical media, while triangular prism media introduced surface scratches and more aggressive material removal. The findings demonstrate that tumbling media geometry and duration critically influence post‑processing outcomes for additively manufactured stainless steel 316L. Spherical media are recommended for applications requiring high geometric fidelity, smooth surfaces, and enhanced hydrophilicity, whereas triangular prism media are suitable for rapid but less precise surface improvement.