Three-electrode pulse power supply for micro ECM

The pulse power supply (PPS) is one of the key systems for micro electrochemical machining (micro ECM). The passive film thickening process is analyzed to describe the gas inhibition and dissolution promotion (GIDP) mechanism. A three-electrode PPS with inter-pulse outputs (IPO) is developed for micro ECM, which is able to add acid on the workpiece-liquid interface using the complete depolarization current imported into the electrolytic cell from the auxiliary electrode during the machining inter-pulse. Machining tests on micro array holes and grooves show that the material removal rate (MRR) is increased to 6.62×10^-4 mm³/s by the three-electrode PPS from 3.21×10^-4 mm³/s with a two-electrode PPS with a neutral NaNO₃ electrolyte. Thus, the machining efficiency is effectively improved with good machining locality in blunt electrolyte and a neutral solution with less environmental pollution. The system also gives high quality surface morphology after ECM in an acidic electrolyte, with the surface roughness, R_a, improved from 0.52 μm to 0.28 μm. The experiments verify the feasibility of the three-electrode PPS with IPO for micro ECM.