Experimental investigation on machining of multiple micro-square holes

Miniature components with multiple holes are commonly observed in many precision elements like micro filters, aerostatic bearings, turbine blades, etc. Micro-Electro Discharge Machining (µ-EDM) is a popular micromachining technique, which includes melting and vaporizing electrode materials to produce the required miniaturized features on various components. This paper focused on multiple micro-square holes machining on the copper sheet using the tailor-made copper multi-tool electrode. Three micro-square holes are machined at a time with different machining parameters such as voltage, frequency, current, and varying pitch of the multi-tool electrode. The responses of the machined geometrical features are estimated, including material removal rate (MRR), side gap (SG), taper angle (TA), and tool wear rate (TWR). Experimental runs are designed based on four factors varied in three levels using the box-behnken method. The ideal set of µ-EDM parameters to maximize MRR while simultaneously minimizing TWR, SG, and TA is identified with a Technique for Order of Preference by Similarity to the Ideal Solution (TOPSIS). The obtained optimum combination of machining parameters are voltage: 40 V, current: 3 A, frequency: 6 kHz, pitch: 1.4 mm, and the corresponding output responses are MRR: 813.48 µg/min, TWR: 82.03 µg/min, SG: 65.49 µm, and TA: 1.18°. Further, the heat-affected zone (HAZ), microstructure, and microhardness around the machined holes are analyzed, and the obtained results are discussed in the paper.