Machining characteristics of insulated Si3N4 ceramics by electrical discharge method - Use of powder-mixed machining fluid

To clarify the electrical discharge machining (EDM) mechanism of insulated ceramics with an assisting electrode method, the waveforms and displacement curve of tool electrode were investigated during electrical discharge proc ess, with emphasis on the following factors: (1) The effects of EDM conditi ons on machining rate, wear of electrode, surface roughness and stability o f discharge. (2) The variation of discharge stability corresponding to the machining process. From the obtained results, it appeared that an electrica l conductive layer was created on the machined surface by the generation of both long pulse and concentration discharge pulses. The surface roughness decreased with increasing the ratio of these abnormal pulses. To decrease t he generation of abnormal pulses, machining was carried out in carbon-powde r-mixed machining fluid. As a result, the surface roughness was markedly im proved according to on increase of the normal discharge ratio and discharge dispersion phenomena.