ارتقای سرعت ماشین‌کاری تخلیه الکتریکی (EDM) با محرک دیسک هیبریدی مغناطیسی/پیزوالکتریک

ABSTRACT Improvement of EDM Machining Speed by Using Magnetic/Piezoelectric Hybrid Drive Actuator

Electrical discharge machining (EDM) is a nonconventional material removal processes based on the thermo-electric energy created between an electrically conductive workpiece and an electrode submerged in a machining fluid. EDM has several advantages such as the capability of machining of all conductive materials, regardless of their hardness, and the ability to deal with complex shapes[1]. However, the machining speed and accuracy of conventional EDM are limited by probability and efficiency of the electrical discharges. To obtain a stable electrical discharge, the electrode needs to be speedily re-positioned in order to maintain a suitable distance from the workpiece, and the debris around the electrode due to EDM has to be removed immediately.

To improve the positioning response and the positioning accuracy, a combination of a conventional electrical discharge machine and a wide-bandwidth, high precision, multi-degree- of-freedom local actuator is required. As the local actuators, a piezoelectric actuator[2], a voice coil motor[3], and a magnetic bearing[4] have been used to improve the positioning response of the electrode.

Moreover, to immediately remove the debris around the electrode, in the conventional EDM, the cylindrical electrode is usually rotated or jumped. The fresh machining fluid can be introduced into the machined hole and the debris can be removed. However, in the rectangular hole machining or 3D surface machining, the electrode cannot be rotated, and adhesion of the workpiece and electrode due to the improper flow of the debris is a problem. To increase the flushing effect during the EDM, an ultrasonic vibration has been superposed on the normal electrode movement[5]. Furthermore, to flush out debris from the machined hole, a vibration-assisted machining also has been introduced to micro-EDM using piezoelectric[6]

In this paper, the developed 3-DOF controlled, highspeed, high-precision, local actuator is attached to an electrical discharge machine to experimentally confirm the increase in the machining speed. Then, the relationships between the machining speed, the amplitude and the frequency of the electrode vibration are discussed.