Accuracy and quality of micro-holes in vibration assisted micro-electro-discharge drilling of Inconel 718

Abstract

Achieving micro-features on superalloy like Inconel 718, with dimensionally high accuracy, has never been easy using a conventional machining technique. Micro-electro-discharge drilling (mEDD) has emerged as one of the key machining technique for fabrication of micro-holes in such superalloys. Although the process has the proven potentials, quality and accuracy of micro-holes deteriorate due to high tool wear and process become unproductive due to the impasse of debris and unsteady machining conditions, especially for high aspect ratio hole drilling. To overcome such issues, anticipating a better performance, a low-frequency vibration assisted mEDD is proposed for machining of Inconel 718. Performance measures, such as material removal rate (MRR), electrode wear ratio (EWR), overcut, and taper angle are analyzed as results of the mEDD operation performed by choosing gap-voltage, capacitance, electrode rotation speed (ERS), and vibrational frequency (VF) as control factors. The Box–Behnken design was used to plan the experiments. The effect of low-frequency vibration on accuracy and surface quality of fabricated micro-holes was also discussed and compared with those achieved by without vibration assistance to the process. An enhancement in the performance of low-frequency vibration assisted mEDD due to improved flushing, debris evacuation, and stable machining conditions is noticed.