EDM of high aspect ratio micro-holes on Ti-6Al-4V alloy by synchronizing energy interactions

Abstract

ABSTRACT Electrical discharge machining (EDM) of high aspect ratio (AR) micro-holes on materials like Ti-6Al-4 V alloy is challenging. The ineffective removal of the machining by-products from and replenishment of fresh dielectric medium in the inter-electrode gap (IEG) limit the penetration depth. The approaches suggested in existing literature either complicate the EDM process or increase the operational costs. Moreover, the effectiveness of energy interactions in the IEG affecting the process performance has not been adequately investigated. This research attempts to synchronize effects of energy interactions between the tool electrode, dielectric, and work material in the IEG by controlling the input discharge energy through current and pulse-on-duration, and dissipated energy through pulse-off-duration and lift settings. Experimental indicators like tool penetration rate, machining time, debris morphology, gas-bubble dynamics, and discharge waveforms are employed to expound the non-linear dynamic behavior of the process. Accordingly, the machining of high AR micro-holes is defined into four zones: usual micro-EDM, transition, high-AR EDM, and critical zones. The maximum depth (10 mm) and AR (17.4) ever reported during the micro-EDM of Ti-6Al-4 V alloy was achieved without employing any additional assistance. Thereby, the capabilities of the conventional die-sinking EDM process are improved for machining high AR micro-holes on Ti-6Al-4 V alloy.