The optimization of micro EDM milling of Ti–6Al–4V using a grey Taguchi method and its improvement by electrode coating

Abstract

Micro electrical discharge machining (micro EDM) is a proven technology for the manufacturing of miniaturized parts and components. This study uses the Taguchi method with an L9 orthogonal array, a signal-to-noise (S/N) ratio, and an analysis of variance (ANOVA) to determine the performance characteristics for micro EDM milling operations. The micro EDM milling parameters (pulse duration, pulse off, discharge current, and working period) are optimized using multiple performance characteristics (electrode wear rate (EWR), material removal rate (MRR), and overcut). Grey relational Taguchi analysis is used to optimize the process parameters for micro EDM ofTi–6Al–4V alloy, using tungsten carbide (WC) tool electrodes. The results demonstrate that using a grey-based Taguchi analysis, the EWR decreases from 1.694 × 10−5 to 1.671 × 10−5 mm3/min, the MRR increases from 6.44 × 10−4 to 7.23 × 10−4 mm3/min, and the overcut decreases from 0.092 × 10−1 to 0.088 × 10−1 mm. There is also a comparative study of the performance of WC, WC-coated Ag (high electrical and thermal properties), WC-coated TiN, and ZrN electrodes (excellent electrical insulation, high melting points, and superior hardness) used for micro EDM milling. A confirmation run shows that the WC electrode-coated Ag thin film yields the highest EWR, MRR, and overcut values. The WC electrodes that are coated with TiN thin film give the lowest EWR and overcut value, which would improve the micro EDM stability and enhance microscale component machining quality.