Plasma-assisted electrochemical machining of microtools and microstructures

A novel hybrid electrochemical machining (ECM) approach combining a pulsed cathodic plasma and an electrochemical machining process, namely, plasma-assisted electrochemical machining (PA-ECM), is proposed in this study to strengthen the capacity of ECM, which entails both high efficiency and precision. The plasma characteristics, material removal behavior, surface topography and machining precision of PA-ECM for microtool fabrication are experimentally investigated under various conditions. The results show that PA-ECM can be realized under optimized electrical potentials with a vapor gaseous skin and electrolytic plasma layer formed around the cathode tool, of which the kinetic and thermal energies can enhance both the kinetics of the electrochemical reaction and mass transport during the ECM process. Through the design of the pulse voltage waveform, the formation and transportation of gaseous bubbles and plasmas can be well controlled. It has been shown that PA-ECM is effective and efficient for improving both the material removal rate and form accuracy in machining microtools. In the presence of plasma, a microrod tool with a high aspect ratio of 55:1 is successfully machined by PA-ECM in 5 s from its original diameter of 200 μm to approximately 18 μm, which seems to be the highest machining rate achieved so far. Additionally, in comparison to traditional ECM under the same conditions, PA-ECM provides a noticeable improvement in the microrod tool straightness error from 66.8 μm to 14.6 μm owing to the side surface insulation effect of the gaseous skin. The resulting surface roughness Ra is drastically reduced from 1096 nm to 46 nm, demonstrating that PA-ECM provides an innovative way to considerably improve the ECM efficiency without compromising the surface finish. Furthermore, the PA-ECM of microholes and microstructures are exhibited with improved precision, demonstrating the capacity of PA-ECM for micromachining.