ELECTRIC DISCHARGE HOLE GRINDING IN METAL MATRIX COMPOSITES

Abstract

Metal matrix composites (MMCs) are playing a very important role in industrial growth because of their superior properties such as high toughness, high specific strength, high temperature resistance, high stiffness etc. The superior properties of these materials cause the difficulty in their machining. In order to achieve an economic machining of hybrid MMC (HMMC), non conventional machining is the best alternative. This report explains the machining of hybrid MMC with three processes namely Electric discharge cutting (EDC), Electric discharge drilling (EDD) and Electric discharge hole grinding (EDHG). Electric discharge cutting (EDC) process is one of the recently developed processes for the enrichment of capabilities of discharge machining. Experimental studies have been conducted on hybrid metal matrix composite (HMMC) with input parameters as current, pulse on-time and flushing pressure, keeping other parameters constant. Material removal rate of developed EDC process has been evaluated through standard test procedures. It has been found that the EDC based process is quick as compared to the conventional cutting processes. Electric discharge drilling has been carried out on an Al based hybrid MMC. The objective of this work is to study the effect of input variables (i.e. current, duty factor, tool speed and flushing pressure) on the material removal rate (MRR), tool wear rate (TWR) and surface roughness (SR). Design of experiments has been employed using response surface methodology (RSM) and through holes have been drilled by using the rotary tool electrode. The experimental results show that the input parameters have significant effect on MRR. TWR and SR. Electric discharge Hole Grinding (EDI-IG) is a combination of Electric discharge machining and mechanical grinding. A16063/SiC/Al203/Gr HMMC was used as a workpiece material and through holes were drilled by using rotary copper tool electrode followed by EDHG. The objective of this study was to investigate the effect of EDl-lG operation on the surface roughness of the hole with input parameters as current, duty factor, tool speed and flushing pressure. From the experimental results. it was found that the process is very effective to produce a finished hole. The grinding action of the process is clearly visible in scanning electron microscopic (SEM) image.