Experimental study on drilling micro-hole through micro-EDM and optimization of multiple performance characteristics

Abstract

Drilling of micro-hole with fine edges and smooth internal surfaces finds numerous applications in manufacturing industries; holes drilled in injection nozzles, drug delivery orifices and spinneret holes are some of examples. This work carries out an experimental investigation and parametric optimization on micro-hole drilling using micro-electrical discharge machining (µ-EDM) process. The machining experiments are conducted employing Taguchi L16 orthogonal array for evaluating machining time (t) average overcut (AOV), taper angle (TA), entry overcut (EnOV), exit overcut (ExOV) and material removal rate (MRR) as process performances, while voltage (V), capacitance (pF) and feed rate (µm/s) are considered as process parameters. The influence of process parameters on the responses is studied at different cutting conditions. The drilled micro-holes profile is studied in terms of burrs, craters, spots on the edges and internal surfaces using micrographs obtained with optical and scanning electron microscopes. The ANOVA result reveals that capacitance is the most significant parameter for t, AOV, TA, MRR, EnOV and ExOV. For simultaneous optimization of three performance measures (i.e., t, AOV and TA), an overall evaluation criterion has been evaluated and optimum cutting conditions such as voltage: 80 V, capacitance: 100 pF and feed rate: 15 µm/s are obtained. The expected outcome obtained at the optimum condition is improved by 10.57% (36.934 to 40.839) over the grand average of performance. The confirmation experimental result at optimum cutting condition (i.e., 39.378) is comparable with the expected result (i.e., 40.839).