Wire-Electrical Discharge Machining of Low Conductive Materials

Electrical discharge machining (EDM) has its main application in tool and die making. The process is based on the erosion phenomenon of electrical gas discharges between two electrodes. Due to this EDM is not affected by mechanical material properties like hardness and strength but properties such as electrical and thermal conductivity, density, melting point and specific enthalpies become important. Today, the limiting value of electrical conductivity for EDM is approximately 0,01 S/cm. This hinders the application of EDM for the processing of the most non-metallic materials. This paper presents experimental and theoretical investigations on the machining low conductive materials by Wire-EDM. The changes of the process caused by the low conductivity are analysed for several workpiece materials. Based on this experimental work, a control circuit is presented, which select the machine settings in dependency of the workpiece resistance in order to get constant working results.