Confined Electrochemical Finishing of Additive-Manufactured Internal Holes with Coaxial Electrolyte Flushing

Adhered powders and undesirable surface quality represent significant challenges for additive manufacturing (AM) technology. AM internal surface finishing is more difficult owing to the poor visibility of internal geometries and the inconvenient manipulation to machine tools. This paper proposed a confined electrochemical finishing process with a coaxial electrolyte flushing manner to remove the AM internal surface asperity. The insulation was conducted in the non-machining area of cathode to cease its electrochemical reaction which consumed the electric charge to generate gas bubbles, and the electrochemical dissolution could be confined within the AM internal hole. More intensive electrochemical dissolution was performed to the AM surface asperity and thus higher material removal and better surface finishing enhancement could be achieved. The coaxial electrolyte flushing manner created a uniform and efficient flow field to facilitate the discharge of electrolytic products. This technique could eliminate the partially melted powders adhered to the AM internal surface and reduce their Ra from 15.620 μ m to 3.494 μ m and Rz from 78.402 μ m to 19.272 μ m. The AM internal hole with a high aspect ratio of 10 could be well handled by this process to eliminate the adhered powders from its internal surface.