Hybrid EDM and Grinding Hard Materials Using a Metal Matrix Composite Electrode

Electrical discharge machining (EDM) has been shown to be a versatile method for machining difficult-to-work materials including heated-treated steels, tungsten carbides and various conductive ceramics. However, low machining efficiency is one of the main EDM disadvantages. The topic of how to reduce machining time and maintains reasonable accuracy has always been of research interest. The main object of the present work was to develop an electrical discharge machining and grinding (EDMG) methodology to remove the re-solidified layer through the grinding induced by a metal matrix composite electrode prior to the re-solidified layer solidification. A metal matrix composite (Cu/SiC_p) electrode, with an electroless pretreatment of Cu coating on SiC_p to enhance bonding status between Cu and SiC_p, with a rotating device was made and employed to study the EDMG technology. Machinabilities of mold material, HPM50 mold steel and P20 WC/Co, were investigated by the combined technologies of EDMG. The machined surfaces of these materials were examined by scanning electron microscopy (SEM) and their surface roughness measured by a profile meter. From the experimental results, it was found that higher material removal rate and lower surface roughness can be achieved when suitable electrode rotating speed, SiC_p size and working current are chosen. In addition, the surface roughness of both materials could be improved as compared with that following the EDM process.