Intentionally-induced dynamic gas film enhances the precision of electrochemical micromachining

Electrochemical machining (ECM) suffers from high process complexity including the design of tool shape, tool insulation, and electrolyte flow, which are inevitable to achieve precision ECM by reducing stray machining. In this study, a novel gas-assisted electrochemical micromachining (GA-ECM) method which employs a gas shielding tool electrode is proposed to solve the problems. A pulsating dynamic gaseous film is intentionally induced surrounding the cathodic tool through the rise of potential to insulate the tool side surface and evoke a local electrolyte flow at the machining gap for flushing, thus enhancing the ECM precision. The principle of the proposed method was verified by both simulation and experiments, and the machining characteristics were investigated considering the current-voltage curve and fluid flow. Further, the machining gap was directly observed by video imaging to reveal the real-time bubbly fluid flow. Experimental results show that the self-induced gas film can not only suppress stray machining by insulation effect but also give rise to a local flushing flow field due to the hydrodynamic behavior of gas evolution. Precise microstructures with a low surface roughness Ra 53.6 nm were successfully fabricated by GA-ECM. In comparison to conventional ECM, the micromachining precision and obtained surface roughness by GA-ECM is improved by 2.6 times and 51.8 times respectively. The study demonstrates the feasibility of GA-ECM as an effective method for efficient micromachining with simplified process procedures and provides insights for optimizing the ECM process.