Optimization of EDM process in machining micro holes for improvement of hole quality

Electrical discharge machining (EDM) or micro EDM found successful for production of micro holes on ceramics, hard metal and alloys. In the present study, experimental investigation and parametric optimization are carried out on EDM process for producing micro holes of diameter 500 mu m on stainless steel (grade 304).Current (I), gap voltage (V) and pulse on time (T-on) are considered as process parameters and are optimized for improving hole quality [i.e., overcut (OC) and taper angle (theta)]. Statistical regression models are developed for predicting OC and theta and effects of parameters are studied using surface plots. The optimal parameters are obtained for single as well as multiple performance characteristics. The traditional Taguchi analysis is used for optimization of each objective individually. This work presents the application of Taguchi optimization for simultaneous minimization of over cut (OC) and taper angle (theta) for improvement of hole quality in drilling micro holes. The optimal level of factors based on analysis of means (ANOM) with highest signal to noise (S/N) ratio is found as (i.e., I1 - V3 - T(on)2). This corresponds to parametric combination being 10 A, 50 V and 150 mu s for I, V and T-on respectively that produce improved hole quality with minimum overcut and taper angle. The obtained result is compared with desirability analysis and found that it is closer.