Study on tool wear in micro EDM

The excessive tool wear always has a great influence on the machining accuracy in micro electrical discharge machining (micro EDM). According to the image processing on the image of tool electrodes, the contour information of the worn tools is obtained, and then the tool wear, especially the tool shape change in micro EDM is studied in this paper. Firstly, the Canny edge detection method is used to extract the outline image of the tool, the scatter points of outline image are curve fitted, and the mathematical description of the tool outline is presented. And then though the mathematical analysis of the fitting function, the tool shape change and tool wear law of micro EDM are analyzed. Finally, according to the curvature changes of fitting curves, the end wear, corner wear and side wear of cylindrical electrode in micro EDM drilling and micro EDM milling, respectively, are divided reasonably based on the analysis, and the amount of each kind of wear is quantitatively estimated.