Servo scanning 3D micro EDM for array micro cavities using on-machine fabricated tool electrodes

Abstract

Array micro cavities are useful in many fields including in micro molds, optical devices, biochips and so on. Array servo scanning micro electro discharge machining (EDM), using array micro electrodes with simple cross-sectional shape, has the advantage of machining complex 3D micro cavities in batches. In this paper, the machining errors caused by offline-fabricated array micro electrodes are analyzed in particular, and then a machining process of array servo scanning micro EDM is proposed by using on-machine fabricated array micro electrodes. The array micro electrodes are fabricated on-machine by combined procedures including wire electro discharge grinding, array reverse copying and electrode end trimming. Nine-array tool electrodes with Φ80 µm diameter and 600 µm length are obtained. Furthermore, the proposed process is verified by several machining experiments for achieving nine-array hexagonal micro cavities with top side length of 300 µm, bottom side length of 150 µm, and depth of 112 µm or 120 µm. In the experiments, a chip hump accumulates on the electrode tips like the built-up edge in mechanical machining under the conditions of brass workpieces, copper electrodes and the dielectric of deionized water. The accumulated hump can be avoided by replacing the water dielectric by an oil dielectric.

A review of the techniques for the mold manufacturing of micro/nanostructures for precision glass molding

“…An electrode with a micro-tip array was generated by creating a pyramid microtip array on the electrode surface using a microdiamond grinding wheel [68]. Tong et al analyzed the processing errors that resulted from the offline-fabricated micro-electrode arrays, and then proposed an array servo-scanning µEDM process with on-machine fabricated micro-electrode arrays [69]. In µEDM, the minimum machinable size determines the extreme scale of the machined microstructure and is defined as the material removal per pulse discharge.…”

Analysis of micro-rods machined using reverse micro-EDM

“…However, in this process, erosion rate is not as fast as conventional EDM due to the small pulse energy involved during the machining process. From the last decade, one of the variants of µEDM which is known as reverse µEDM (R-µEDM) has been gaining popularity for the fabrication of single-as well as multiple-tipped micro-rod of various shapes with high aspect ratio [10][11][12][13][14][15][16]. Multiple-tipped micro-rods have a plenty of applications in industries such as drilling of micro-holes in probe card for testing semiconductor device and perforated shadow mask with various shapes which are used in CRT monitors.…”

“…Micro-tool electrodes with 3 × 3 array are fabricated through combined actions of WEDG, R-µEDM and electrodes' end trimming. Further, the same method is used to machine 3 × 3 array of hexagonal micro-cavities where hump of debris is accumulated at the electrodes' tip that are removed using oil dielectric [13].…”