Determination of optimum parameters with multi-performance characteristics in laser drilling-A grey relational analysis approach

Laser drilling is increasingly becoming the method of choice for precision drilling for variety of components. However, a number of defects such as spatter, recast, heat-affected zone (HAZ), and taper limit the application. Elimination of these defects is the subject of intense research. This paper presents a grey relational optimization approach for the determination of the optimum process parameters which minimize the HAZ and hole circularity and maximize material removal rate in a Pulsed Nd:YAG laser micro-drilling in high carbon steel within existing resources. The input process parameters considered are pulse width, number of pulses, assist gas (oxygen) flow rate, and its supply pressure. A higher resolution-based L-25 orthogonal array has been used for conducting the experiments. The designed experimental results are used in grey relational analysis and the weights of the quality characteristics are determined optimizing the parameters. On the basis of optimization results, it has been found that the optimal parameter level gives a small HAZ, fine hole, and maximum material removal rate. Subsequently, the results are also verified and found appropriate by running confirmation tests.