Fabrication of microelectrode with large aspect ratio and precision machining of micro-hole array by micro-EDM

Micro electrical discharge machining (micro-EDM) exhibits good processing capability to miniature structures such as micro-holes, micro-dimples, micro-channels and so on. In present study, the precision micro-EDM of micro-hole array with diameter less than 50 mu m was explored. A novel active supplying wire-electro discharge grinding (AS-WEDG) device was developed aiming to reduce the wire fluctuation at grinding location and improve the aspect ratio of microelectrode. With the developed AS-WEDG device, the microelectrode of 40.3 mu m in average diameter and 49.6 in aspect ratio was successfully fabricated. For RC-type pulse generator, the effects of open-circuit voltage and capacitance on machining quality of single micro-hole were concerned. By analyzing the wear characteristics of microelectrode, the constant length compensation strategy was adopted during the micro-hole array machining process. Meanwhile, in order to eliminate the adverse effect of cumulative compensation errors, the periodic adjustments of axial position of microelectrode were involved based on the CCD vision system. According to the requirement of inkjet nozzle, array of 256 (2 x 128) micro-holes with average diameter of 46.13 mu m was machined on a 50 mu m thick stainless steel. The diameter consistency of micro-hole array was assured by showing standard deviation of 0.44 mu m and 0.68 mu m at entrance and exit side, respectively. In addition, the static printing test verified the good working performance of as-machined micro-hole array by generating uniform droplet velocities.