Electrochemical drill-grinding (ECDG) is a compound machining technology, which combines Electrochemical machining (ECM) with mechanical drill-grinding process. On this basis, a new method of machining small holes which called ultrasonic-assisted electrochemical drill-grinding (UAECDG) is proposed. First, the principle of UAECDG is analyzed through analysis of UAECDG process and electrochemical passivation behavior of materials. Second, the simulation of electrochemical drill-grinding process was studied to illustrate the effect of ball-end electrode on reducing the hole taper and improving the machining accuracy. Afterwards, several groups of experiments are conducted to analyze the influence of electrical parameters, ultrasonic amplitude and matching degree between electrolysis and mechanical grinding on the machining quality of small holes. Finally, small holes with diameter of 1.1 ± 0.01 mm, surface roughness of 0.31 μm and taper of less than 0.6 degree were machined by UAECDG, which revealed UAECDG is a promising compound machining technology to fabricate small holes with high quality and high efficiency.

Fabrication of the injection nozzle micro-hole on the aero engine is a difficult problem in today’s manufacturing industry. In addition to the size requirements, the nozzle micro-hole also requires no burr, no taper and no heat-affected zone. To solve the above problem, an ultra-short voltage pulse and a high-speed rotating helical electrode were used in electrochemical drilling (ECD) process. Firstly, a theoretical model of ECD with ultra-short voltage pulse was established to investigate the effects of many predominant parameters on machining accuracy, and the effect of rotating helical electrode on the gap flow field was analyzed. Secondly, sets of experiments were carried out to investigate the effects of many key parameters on machining accuracy and efficiency. Finally, the optimized parameters were applied to machine micro holes on 500 μm thickness of GH4169 plate, and micro-holes with the diameter of 186 μm with no taper were machined at the feed rate of 1.2 μm/s. It is proved that the proposed ECD process for fabricating micro-holes with no taper has a huge potential and broad application prospects.