Preliminary study of material removal in electrical-discharge machining of SiC/Al

Metal matrix composite (MMC) materials have increasingly widened their use due to thr merits of possessing high specific strength and modulus of elasticity while carrying good deformability and conductivity comparable to metals. In addition to it's use structural and functional components for high-performance applications, such as aerospace vehicles and racing automobiles, MMC also has potential for molds. Especially for the large and mid-size molds in precision manufacturing, where handling is difficult due to the heavy weight, MMC can improve the productivity by saving the cost of loading, positioning and stocking. MMC is difficult to machine due to serious tool wear caused by the hard reinforcement. To exploit the potential industrial applications and investigate proper manufacturing processes, the machinability of electrical discharge machining (EDM) of MMC needs to be studied for reliable and economical production. The fundamental analysis starts from the material removal of MMC by a single spark. This paper presents the correlation between the major machining parameters, electrical current and on-time, and the crater size produced by a single spark for the representative material SiC/Al. The experimental results not only show the predicted proportionality based on heat conduction model, but are also compared with common steels regarding the material removal rate. Though the crater size of SiC/Al is larger than steel, the SiC particles can interfere the discharges. For effective EDM, large electrial current and short on-time are recommended. Based on the obtained knowledge, one can proceed to the study of machinability of MMC by EDM for optimal production cycle.