Formation of macro-sized through-holes in glass using notch-shaped tubular electrodes in electrochemical discharge machining

Abstract

Formation of macro-sized (>3 mm) through-holes in a 1.1 mm glass substrate by using a novel tubular electrode having notches in electrochemical discharge machining (ECDM) is reported. Solid tool electrodes were initially used to create through-holes; however, the glass breakage was observed when the tool was traveled beyond 200 μm. Tubular electrodes having notches were used to resolve the glass-breakage issue. These novel tubular electrodes with vertical notches with varying numbers (2, 4, 8, 12) were formed using the wire-electro-discharge machining. The gas film formation and the discharge features were characterized by the current-time graphs obtained with the oscilloscope. More intense discharges were noticed in the tubular electrodes. Due to vertical notches in the tubular electrode, the electrolyte could reach easily even at depths more than 600 μm that has reduced the chances of glass breakage. Macro-sized through-holes were successfully obtained with tubular electrodes with 8 and 12 notches with vertical travel of 1000 μm. The opening size of through-holes was lower in the case of tubular electrodes having 8 notches than other tool electrodes, and thus, its usage is recommended in making macro-sized through-holes. A prototype demonstrating the fluid flow in the microfluidic plate is presented to show the potential applications.