Research on conductive-material-filled electrodes for sidewall insulation performance in micro electrochemical machining

In micro electrochemical machining (ECM) processes, stray corrosion causes undesired metal dissolution and the deterioration of shape accuracy. Adopting a sidewall-insulated electrode is an effective approach to suppressing stray corrosion. Most sidewall-insulated electrodes are made of metal substrate and non-metallic thin films. Nevertheless, the thin-film insulating materials attached to a metal substrate are susceptible to damage in an electrolytic environment. This study presents a novel concept of the conductive-material-filled electrode for better sidewall-insulation performance. The micro-scale quartz tube serves as the insulating substrate. Commercially available conductive fillers including metal wire, molten metals, and silver powder are filled inside the working cathode of the quartz tube. Consequently, the metal-wire-filled electrode, molten-metal-filled electrode, and nano-powder-filled electrode are designed and fabricated. From the verification results of electrode toughness, material removal rate, and surface topography, the metal-wire-filled electrode and molten-metal-filled electrode exhibit the same performance as a traditional metal-based electrode and much better durability. By contrast, the nano-powder-filled electrode is unable to withstand long-term ECM processes because of the loss of cured powder particles. In ECM experiments, microstructures with steep sidewalls (taper angle <9.7°) were machined using the metal-wire-filled electrode and molten-metal-filled electrode, which could replace the traditional electrode, achieving a longer service life and superior sidewall-insulation performance.