Electrochemical discharge machining of microchannels in glass using a non-Newtonian fluid electrolyte

The gas film plays a key role in electrochemical discharge machining (ECDM). However, the impact force of the electrochemical discharge affects the gas film and hence can lower the machining performance. To improve the stability of the gas film, a novel ECDM approach based on a non-Newtonian fluid electrolyte, i.e. the mixture of Polyacrylamide and KOH is proposed in this study. The experimental results show that, compared to the traditional Newtonian fluid KOH electrolyte, the non-Newtonian fluid electrolyte can significantly weaken the effect of the impact force on the gas film, and thus the gas film was more stable. The theoretical model and experimental results both show that stable electrochemical discharge and a lower critical voltage can be achieved with a non-Newtonian fluid electrolyte condition for its’ gas film is thinner and more stable than with the KOH electrolyte. With the non-Newtonian fluid electrolyte, the heat-affected zone and entrance overcut of the microchannels were both smaller than with the KOH electrolyte. In this study, a complex microchannel with a depth of 100 µm and a spacing of 30 µm was successfully fabricated. This is the smallest spacing reported so far in the literature for a microchannel fabricated in glass using ECDM. Moreover, a smoother machining surface with Ra 0.45 µm was obtained with the non-Newtonian fluid electrolyte. It can be concluded that using the non-Newtonian fluid electrolyte is a simple and effective way to enhance the stability of gas film and thus, improve the micromachining performance of ECDM.