Electric discharge machining of Al-SiC metal matrix composites using rotary tube electrode

The machining characteristics of SiC/6025 Al composite using rotary electro-discharge machining (EDM) with a tube electrode were investigated in this study. Brass was used as the electrode material to EDM SiC/6025 Al composites. Three observed values: material removal rate (MRR), electrode wear rate (EWR) and surface roughness (SR) are adopted to evaluate the machinability. Peak current, polarity, volume fraction of SiC reinforced particles, pulse duration, hole diameter of the tube electrode, and speed of electrode rotation were used as the input variables to assess the machinability. Peak currents of EDM drilling were confirmed to have positive effects on the MRR, EWR and SR. The MRR, EWR and SR were more with positive polarity of the electrode than at negative. Increase in volume percentage of SiC resulted in decrease in MRR and increase in EWR. The pulse duration had an inverse effect with MRR, EWR and SR. The decrease in the hole diameter and increase in speed of the rotating tube electrode resulted in increase in MRR and decrease in EWR and SR. In comparison, the electrode hole diameter and rotational speed have major effect on MRR, EWR and SR. The optimum machining parameter for maximum MRR, minimum EWR and better surface roughness were found out using genetic algorithm. (C) 2004 Elsevier B.V. All rights reserved.