Development of ultrasonic pulsation wire electrical discharge turning device for micro/nano medical part manufacturing

Abstract

Micro/Nano manufacturing has re-engineered the medical devices technology to component miniaturization. Despite of numerous technical challenges, tremendous development of micro/nano medical devices continue to grow. Wire electrical discharge turning (WEDT) is a hybrid process that combines two mechanics of cutting i.e. wire electrical discharge and workpiece rotation. Its ‘free of cutting force” property made it one of the desirable techniques for manufacturing intricate micro/nano cylindrical components. Despite its capability for fabricating micro/nano-size components, the main concern was its unstable spark discharge energy that resulted in poor machined surface quality. Unlike a normal wire-EDM process, the rotating workpiece alters the mechanic of material removal process causing unstable energy density and high pulse intensity. In order to solve the discrepancy, one of the possible techniques is to incorporate an ultrasonic pulsation frequency which has been proven to increase the machined surface quality on similar die sink EDM erosion process. Hence, based on the proven concept, this paper proposes a novel strategy to control the spark discharge energy by incorporating the ultrasonic pulsation in the WEDT process with the aim to enhance the machined surface quality. In the paper, the development of an ultrasonic pulsation rotary wire electrical discharge machining device for micro/nano medical part manufacturing aiming to improve the surface integrity of machined parts, i.e. surface roughness and sub-surface damage are presented. Experimental trials on machining titanium alloy were conducted to evaluate the capability of the proposed rotary ultrasonic device in fabricating micro/nano size part. From experimental results, it was found that the new rotary ultrasonic device was capable of machining complex micro/nano geometric features. In addition, the improvement on large L/D machining ratio under single pass ultrasonic cutting condition was also achieved.