An ultrasonic vibration device for micro electro-discharge machining

Abstract

Micro-machining technologies have enjoyed a recent resurgence due to massive demands in many engineering, production and manufacturing sectors. Micro Electric Discharge Machining (μ-EDM) is one of the most popular techniques available to produce microscopic features and components for various industries. Micro electro-discharge machining (μ-EDM) uses electro-thermal energy from repetitive sparks generated between the tool and workpiece to remove material from the latter. This technique can ensure better machining performance in terms of reduced Heat Affected Zones and surface finishing. It also comes with inherent disadvantages such as high machining time, low material removal rate (MRR) and unstable machining. One of the bottlenecks of μ-EDM is the phenomenon of short circuits due to the physical contact between the tool and debris (formed during the erosion of the workpiece). To overcome these factors, vigorous flushing of dielectric fluid is performed. Adequate flushing of the debris can be achieved by applying low amplitude high-frequency vibration to the workpiece. The vibration aids in carrying away the debris accumulated in the spark-gap region. In this research, a novel design of an ultrasonic vibration fixture has been proposed. This fixture will facilitate vibration of the workpiece that is required to improve machining performance. Further enhancement of the design leads to better machining performance. System Identification helps to determine the nature of the system and model the input-output response. The oscillation of the system can be easily characterized and validated using System Identification. This study, however, shows that the application of vibration does not yield beneficial results for the μ-EDM for all the parametric conditions. The results of this study suggest that vibration-assisted μ-EDM becomes less effective as the discharge energy is increased (primarily by increasing the capacitor value of the RC pulse generator). Similarly, the reduction of the occurrence of the short circuit was profound when the low discharge energy level with low voltage and low capacitor setting of the RC Pulse generator was used. The overall scale of the overcut with various discharge energy and μ-EDM speed varied from 1μm/s to 11μm/s for the conventional μ-EDM process. At a low capacitor value (10 pF), ultrasonic vibration reduces tool wear by ~31%. As a result of using the ultrasonic vibration device, the average increase in MRR of ~ 46% was achieved across all voltage levels.