MEMS-Based Micro-Electro-Discharge Machining (M EDM) by Electrostatic Actuation of Machining Electrodes on the Workpiece

摘要

This paper reports a micro-electro-discharge machining technique that is enabled by electrostatic microactuators. The 18-$muhbox{m}$-thick movable copper electrodes that serve as machining tools are microfabricated directly on the surfaces of the workpiece and operated in dielectric machining fluid. A dc voltage of 80–140 V applied between the electrode and the workpiece through a resistance–capacitance pulse generation circuit is leveraged to electrostatically pull in the electrodes toward the workpiece, inducing a breakdown and spark discharge. The discharge lowers the gap voltage and releases the electrode, which is pulled in again as the capacitor is recharged through the resistor. This pull-in and discharge cycle is self-sustained to perform the removal of the workpiece material. The electrode's displacement of $sim!! 30 muhbox{m}$ is measured at the machining/actuation voltage of 100 V. Micromachining of stainless steel is implemented using the planar electrode with $1.6 times 1.03hbox{-mm}^{2}$ area, achieving the removal depth of 20 $muhbox{m}$. The double-layer electrodes that have electroplated microstructures with high-contrast patterns on the backside of the electrodes are developed to demonstrate custom micromachining. A dynamic characteristic of the built-in capacitance of the devices, which is used to form the pulse generation circuit, as well as their mechanical response during the machining process, is theoretically analyzed with the experimental results.$hfill$ [2008-0299]