Fundamental research with respect to thermal phenomena of micro EDM

Abstract

Material removal in electrical discharge machining, EDM is by thermal erosion. Therefore, information on thermal phenomena of the process is required for further analyses of the process. Currently, demands on micro components increase the applications of EDM for micro machining significantly. This leads to the development of EDM with comparatively lower discharge energy than that of conventional EDM. In this work, for convenience the conventional and newly developed EDM is called macro and micro EDM, respectively. Although there is no difference in principle and mechanism of material removal between both processes, the micro EDM is capable of producing micro components with higher accuracy beyond the capability of macro EDM. However, unlike macro EDM, researches on the micro EDM thermal phenomena are limited due to the small spatiotemporal scale of the process, which makes both observation and analysis of the gap phenomena significantly difficult. Therefore, in this work thermal phenomena of micro EDM were obtained including energy distribution ratios, plasma diameter, power density and removal mechanism. These parameters were compared with those of macro EDM, and their influence on micro and macro EDM efficiencies were discussed. In this work, the efficiencies are represented by ratio of removal with respect to molten area volume or removal efficiency, Re and ratio of energy consumed for material removal with respect to energy distributed into workpiece or energy efficiency, Ee. Both Re and Ee of micro EDM were greater than those of macro EDM because the power density at micro EDM workpiece was found significantly higher than that of macro EDM. These results also explain differences in their performances such as the formation of white layer and residual stress. At the end of this work, to show the importance of the obtained results, an example application that describes deformation of micro fin machined by micro EDM due to thermal stress was discusse