Electrochemical drilling of small holes by regulating in real-time the electrolyte flowrate in multiple channels

Electrochemical drilling (ECD) provides an alternative technique for drilling multiple small holes in difficult-to-machine materials in numerous industrial applications such as for aeroengines. The value and fluctuation of electrolyte flowrate can seriously affect the machining stability and hole quality in ECD. In particular, when drilling multiple holes, the distribution and fluctuations of the electrolyte flowrate in each channel could influence the uniformity of the electrolyte flowrate among multiple tube electrodes, thereby affecting the machining stability and the maximum feed rate. Thus, an eight-channel flow control system was developed to measure and regulate in real time the electrolyte flowrate supplied into each individual tube electrode. This paper proposes ECD of small holes with real-time flowrate control to improve the uniformity of electrolyte flowrate in each tube electrode and reduce the fluctuations in the electrolyte flowrate. In single-hole drilling, when the electrolyte flowrate was regulated in real time, the hole quality and machining stability were considerably better than without regulation. This is because the electrolyte flowrate remains basically constant, which stabilizes the flow field. Moreover, by considering the hole profile, it was found that an electrolyte flowrate of 200.0 mL/min can be acceptable for ECD of small holes. When the eight-channel flow control system was used in multiple-hole drilling, the uniformity of the electrolyte flowrate in each tube electrode was obviously improved, which led to a more stable process. Additionally, the maximum feed rate can attain 2.40 mm/min in multiple-hole drilling. Based on these findings, a matrix (5 × 32) of multiple small holes was successfully fabricated with a satisfactory diameter consistency, as the machining stability and machining efficiency had been enhanced.