Micro-electro-discharge machining by MEMS actuators with planar electrodes microfabricated on the work surfaces

This paper reports a MEMS-based micro-electro-discharge machining technique that is enabled by the actuation of micromachined planar electrodes defined on the surfaces of the workpiece. The 18-mum-thick copper electrodes suspended with the anchors are formed on a stainless-steel wafer/workpiece. A DC voltage of 80-140 V is applied between the electrode and the workpiece through a resistance-capacitance circuit that controls the pulse energy and timing of spark discharges. The suspended electrode is electrostatically actuated towards the wafer, resulting in a breakdown, or spark discharge. This instantly lowers the gap voltage, releasing the electrode, and the capacitor is charged up through the resistor. Sequential pulses are produced through the self-regulated discharging-charging cycle. Micromachining of the stainless-steel wafer is demonstrated using an electrode with the area of 1.6times1.03 mm², achieving removal depth of 20 mum with 100 V that provides the electrode´s displacement of ~30 mum. The pulse formation is also implemented using only the parasitic/built-in capacitance between the electrode and the workpiece. A dynamic characteristic of the built-in capacitance is experimentally analyzed.