Development of a CNC micro-EDM machine

Micro-EDM has been a key technology for micro-machining because of the high precision and good surface quality that it can achieve. However, a number of issues remain to be solved before micro-EDM can become a reliable process with repeatable results. The purpose of this paper is to develop two key techniques for a CNC micro-EDM machine. Firstly, to achieve the motion control requirements of high precision, high sensitivity and hard real-time, an open architecture CNC system is developed with submicro-meter resolution of a 3-axis linear motor stage. The proposed CNC system is featured with open architecture, modularity, DSP-based control and Linux-based software. Secondly, to deal with the difficulties in micro electrodes on-line fabrication and compensation, a machine vision system is developed with a resolution of 1.61μm and a magnification is 113∼729. The contour of micro electrodes can be extracted by means of the Canny edge detector. Through the system calibration, the micro electrodes dimension can be measured on-line. All programs are developed under the Linux operating system, such as an NC code interpreter based on Lex and YACC, a database based on MySQL, a GUI based on Qt, an image capturing program base on V4L2 API, and an image processing program based on OpenCV. Experimental results demonstrate that the developed micro-EDM machine has the potential of manufacturing not only micro-shafts and micro-holes but also complex three-dimensional micro-cavities.