A mathematical model to predict overcut during electrochemical discharge machining

Overcut is a major reason for the dimensional deviations, especially during high aspect ratio micromachining in electrochemical discharge machining (ECDM). Since electrolyte concentration plays a vital role in material removal, by understanding the effect of electrolyte concentration on the machined feature, it is possible to reduce the overcut associated with the ECDM process. This reduction in overcut was used in the study to drill high aspect ratio microholes in glass. The effect of concentration on the overcut is explained with an analytical model. The model considers the thermal effects on material removal for ECDM assuming a high-temperature chemical etching mechanism for the material removal. It describes the effect of electrolyte concentration as well as machining time on material removal. Results reveal that at the microscale, tool diameter has minimal effect on overcut for a given machining voltage. Microholes with aspect ratios as high as 12 were produced in glass in this study.