LAUSR

Composite materials are difficult to process under conventional machining techniques. When machined using such unconventional machining methods as the electric discharge process, the result is low machining efficiency due to the presence of reinforced particles. We sought to improve the machining characteristics of AA7050 hybrid composites by adding Al2O3 particles to the dielectric medium. Experiments were carried out using varying powder concentration, current, pulse on time, and weight percentage of composites and material removal rate (MRR), tool wear ratio, and surface roughness were recorded. Composites of different weight percentage were manufactured thru stir casting. SiCp and Al2O3p (mesh size 5 µm) were selected as reinforcing particles. Composites machined in powder mixed electric discharge machining (PMEDM) exhibit better MRR owing to the bridging effect. The modified plasma channel enhances surface quality because of the homogenous dispersal of discharge energy throughout the machined surface. Surface topography was analyzed with scanning electron microscopy. The specimen machined with EDM showed a re-melted layer and globules which were absent under PMEDM machining owing to which surface quality improves. The machining parameters were optimized using the TOPSIS technique and the specimen machined in PMEDM with parametric values 15 A current and 30 µs pulse on time offered the best machining characteristics.