Multi-objective optimisation of Nd:YAG laser micro-drilling of zirconia using Taguchi method with desirability function analysis

Abstract

In this paper, a multi-objective optimisation technique, based on Taguchi method and desirability function analysis, has been proposed and adopted in search of an optimal parametric combination to yield favourable hole geometry, during Nd:YAG laser micro drilling of zirconia. Taguchi L25 orthogonal array, for a four-factor five-level design, is used for plan of experiments. Lamp current, pulse frequency, pulse width and assist air pressure are considered as input parameters. Hole taper and HAZ width, which greatly influence the quality and feature characteristics of a drilled hole, are the responses considered. Desirability function analysis is employed to convert the multiple quality characteristics into a single performance measure called, composite desirability index. Application of this approach greatly simplified the complicated multi-objective optimisation problems. Optimal micro-drilling parameters are then determined by the Taguchi method using composite desirability index as the single performance index. Furthermore, analysis of variance (ANOVA) is carried out to determine the significance of parameters on the overall output feature. The optimal result obtained has been verified with the help of additional confirmatory experiments. The outcome of these experiments indicates the application feasibility of the proposed optimisation technique for continuous improvement in Nd:YAG laser micro drilling product quality.