Experimental investigation of micro-machining of borosilicate glass using an ultrasonic assisted rotary electrochemical discharge machining (UA-RECDM) process

Electrochemical discharge machining is an advanced micro-machining process for machining of conductive as well as non-conductive hard and brittle materials, e.g. glass, ceramics, silicon wafer, etc. The present work explores the machining of glass using an in-house developed novel ultrasonic assisted rotary electrochemical discharge machining setup. The setup has specialized features, such as using ultrasonic vibrations to tool the electrode and incorporating rotary motion for manipulating the workpiece. Experiments were conducted using a one factor at a time approach by varying the tool feed rate, the amplitude of the vibrations and the rotation of the workpiece as process parameters. The quality of the machining output was evaluated by observing two key parameters: the overcut and the circularity of the hole. It was observed that as the workpiece rotation speed increased from 40 rpm to 60 rpm, the overcut in the machined samples decreased from 181.378 mu m to 163.564 mu m. The rotary motion of the workpiece caused a seeping action of the electrolyte in the hydrodynamic regime, leading to the formation of a thin gas film and the stabilization of the discharging process. The morphology of the machined hole exhibits better circularity, low heat-affected zones, minimum micro-cracks and smooth edges at its periphery due to stable discharge formation.