Burr Minimization in Step Drilling of Al - Fly Ash/Gr Hybrid Composites by Taguchi Method

摘要

Metal Matrix Composites (MMCs) have emerged as a potential material especially for automotive and aerospace industries. In view of the growing engineering applications of these composites, the machining parameters have to be optimized in order to attain good surface quality, reduced tool wear and cutting forces. In this paper, the influences of the feed and step drill's geometries such as step angle and step size on the exit burr height have been investigated for burr minimization in drilling of MMCs. Experimental study was conducted for Al-15wt.% fly ash composites and Al-15wt.% fly ash/1.5wt.% graphite hybrid composites which are fabricated through stir casting method. Optimum drilling parameters were identified for burr minimization by the application of Taguchi method, analysis of variance (ANOVA) and the results were validated by confirmation test. Results revealed that feed and step drill's geometries step angle and step size were the most influential factors on the formation of burr. Dynamometer was employed to measure the thrust that was being applied to the work piece when it was drilled. The inclusion of graphite as supplementary reinforcement in Al/fly ash reinforced composite reduces the thrust force and exit burr height considerably.