Evaluation of scale effect of micro electrical discharge machining system

Abstract

Micro electrical discharge machining (EDM) is generally regarded as the application of conventional EDM in micro scale. The energy transfer characteristic and material removal mechanism of micro EDM are differ from that of macro EDM due to the miniaturization of tool electrode and discharge energy. The unexpected machining performance can be attributed to the so-called scale effect. In this study, the similarity theory was used to quantitatively evaluate the scale effect and the effectiveness of this evaluation method was established. In this method, greater similarity precision means more significant scale effect. Tool electrode diameter, capacitance, and open circuit voltage were adopted as factors in orthogonal experiment to explore the scale effect caused by the miniaturization of tool electrode and discharge energy. The single factor scale effect and system scale effect of EDM are evaluated based on orthogonal experiment. Scale effect with different degree is presented in terms of material removal rate (MRR), relative tool wear ratio (RTWR), and overcut (OC). The machining type is transferred from macro EDM to micro EDM as a result of the decrease of machining parameters. A positive scale effect is produced and open circuit voltage is the most important factor for the scale effect of EDM.