Geometry prediction of EDM-drilled holes and tool electrode shapes of micro-EDM process using simulation

EDM is an efficient machining process for the fabrication of a micro-metal hole with various advantages resulting from its characteristics of non-contact and thermal process. However, this process has a serious problem caused by the tool wear, which significantly deteriorates the machining accuracy. In this paper, a geometric simulation model of EDM drilling process with cylindrical tool is proposed to predict the geometries of tool and drilled hole. The geometries of tool and workpiece are represented by two-dimensional matrix. For accurate prediction of their geometries, the tool motion, the sparking gap width, the spark frequency, the crater made by a single spark, and the tool wear ratio are considered as simulation parameters. To verify the simulation model the prediction results are compared with the actual experimental ones. Consequently, it is shown that the geometry prediction results match the experimental ones well within the error of 13%. Developed model can be used in offline compensation of tool wear in the fabrication of a blind hole. For the purpose of this, a compensation scheme based on the developed model is introduced, it is then demonstrated that the scheme is successfully applied to an actual micro-hole machining.