The dominance of the spark eroding process in complex ceramic components has promoted a significant growth analysis in the ceramic composites domain in modern manufacturing industries. The latest developments in ceramic components are concentrated on both the enhancement of the mechanical properties and the machinability of complex 3D parts while using spark EDM. The current (I), pulse on time (T on ), pulse off time (T off ) and dielectric flushing pressure (DP) are considered sparking parameters for the machining of a Si 3 N 4 -TiN ceramic composite. These composites find their application in high-temperature environments viz. metal forming, extrusion dies, turbine blade and non-ferrous molten metal handling components. Taguchi's orthogonal array (OA), L 18 , has been used to design the experiments. The optimal machining inputs are determined by the grey relational grade (GRG), which is attained from the grey relation analysis (GRA) for various response characteristics, such as the material removal rate (MRR), tool wear rate (TWR), circularity (CIR), cylindricity (CYL) and perpendicularity (PER). The significant parameters are identified via an analysis of variance (ANOVA).Finally, the optimised process parameters resulting in a higher MRR, lower TWR, lower form tolerance, and decreased orientation tolerance are verified through a confirmation test demonstrating that sparking process responses can be effectively improved. Downloaded by [New York University] at 21:49 02 August 2015 2

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Intermetallic/ceramic composites with multiple responses are based on L18 orthogonal array with gray relational analysis (GRA). This paper presents a new approach for the optimization of drilling parameters on drilling MoSi 2– SiC composites. Optimal machining parameters can then be determined by the gray relational grade as the performance index. In this study, the sparking parameters namely current (I), pulse on time (t on ), pulse off time (t off ), spark gap and dielectric flushing pressure (P) are optimized with considerations of multiple performance characteristics including multi responses such as material removal rate (MRR), electrode wear rate (EWR), circularity (CIR), cylindricity (CYL), perpendicularity (PER). A gray relational grade obtained from the GRA is used to solve the electrical discharge machining (EDM) process with the multiple performance characteristics. Based on the gray relational grade, optimum levels of parameters have been identified and significant contribution of parameters is determined by ANOVA. Confirmation test is conducted to validate the test result. Experimental results have shown that the responses in EDM drilling process can be improved effectively through the new approach.

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