Electrochemical mechanical polishing of internal holes created by selective laser melting

Selective laser melting (SLM) is a rapidly developing technique in additive manufacturing (AM) that has attracted considerable interests in industry owing to its tremendous advantages. However, the inferior surface quality of SLM components, specifically the partially melted powder attached on the surface, restricts the functionality of the as-printed part and requires further processes to polish their surface. In particular, polishing an internal hole created by SLM becomes more challenging because of poor visibility of the internal surface and consequent complicated manipulation. This study proposed a novel electrochemical mechanical polishing (ECMP) process for SLM internal holes to eliminate the partially melted powders and improve surface quality. This ECMP process could reduce the topographical fluctuation of the internal surface by eliminating the partially melted powders, thus reducing the surface roughness (Sa) values of the straight hole from 14.151 to 3.880 μm. During the electrochemical dissolution, the mechanical effect could minimize surface fluctuation and discharge gas bubbles and electrolytic products, facilitating the continuous polishing process and realizing an even and flat surface. This proposed ECMP process could also sufficiently polish the curving internal hole with eliminating the partially melted powders, which exhibited a rather smooth surface with significantly reduced Sa values from 15.522 to 9.095 μm.