Gas Bubble Evolution during ECM Process can be suppressed by Pulse Parameters: High Speed Videographic Observations during Early Stages of Bubble Evolution

Abstract

The precision in electrochemical machining (ECM) is adversely affected by the generation of gas bubbles due to the inherent electrochemical reactions occurring at the cathode (tool) and anode (workpiece) surface. These gas bubbles are known to cause variations in electrolyte conductivity and lead to uneven dissolution and limit the achievable flatness and surface finish. The demands for precision ECM make it important to investigate the bubble evolution phenomenon. In the prior state of the art, this has been done by means of transparent electrodes and high-speed video observations. The current work involves high-speed video experiments with a specific intention to observe gas bubbles during the early stages of evolution and attempts to address two main research questions: (i) Is it possible to suppress gas bubble evolution in ECM using pulse parameters? (ii) Is it possible to do ECM without gas bubbles? The results reveal that shorter pulse-on times and longer pulse-off times reduce the growth of the concentration boundary layer, thereby suppressing bubble generation. Furthermore, by combining the aforementioned electrical pulse settings with an appropriate flow rate, there is no significant detection of gas bubbles in the experiments conducted here, as can be concluded from the fact that the interelectrode gap (IEG) remains transparent. The industrial applicability-oriented analysis focused on evaluating the final IEG and did not reveal any significant difference due to shorter flow lengths. It is further suggested that by employing high flow rates in combination with shorter pulse-on times, the pulse-off time can be further shortened to raise duty cycles so as to facilitate economic machining without the influence of gas bubbles.