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In this paper, the firefly algorithm is employed with the RSM (response surface methodology) to investigate the electro chemical discharge machining (ECDM) process in terms of effects of the process parameters on the output quality characteristics, as well as, to set the optimal process parameters for achieving the better product quality. Firefly algorithm is a powerful nature inspired metaheuristic algorithm that can solve complex optimisation problems, both, single objective and multi-objective optimisation problems. It is noticed that firefly algorithm can find the optimal solution, efficiently, within very less timescale. It is also very effective in predicting the parametric trends of responses. The results obtained by using firefly algorithm for parametric optimisation of ECDM are compared with those derived by the past researchers, which prove the applicability and effectiveness of this algorithm in enhancing the performance of the ECDM process.

In the present research work, experimental investigation and process optimisation of transmission laser welding of dissimilar plastics are carried out using response surface methodology (RSM) and flower pollination algorithm (FPA) integrated approach. RSM is used to plan the experiments and to develop the parametric models of the process responses, namely weld strength and weld width. Flower pollination algorithm, a novel nature-inspired meta-heuristic algorithm, is applied to search for the combinations of optimal process parameters that satisfy single objective as well as multiple objectives using the developed RSM models. Parametric analyses are also done using the trend predicted by FPA. This algorithm is found to be capable of predicting accurate trends of the parametric effects. The superiority of FPA in process optimisation and prediction of parametric trends is due to the fact that FPA can locate the global optima and no parameters are held constant during the optimisation process and also during the trend prediction.

In the present work, laser transmission welding process is investigated and optimised using firefly algorithm, a population-based metaheuristic and bio-inspired algorithm. Laser power, welding speed, stand-off distance and clamp pressure are the laser transmission welding process parameters which control the output qualities like lap-shear strength and weld-seam width of the welded part. To select the optimal setting of process parameters, single-objective and multi-objective optimisations are performed using firefly algorithm, in which the objective functions are developed using response surface method. Results obtained by using firefly algorithm are found to be superior to those obtained using conventional optimisation technique. Firefly algorithm also found to be superior to particle swarm optimisation algorithm, differential evolutionary algorithm, and shuffled frog leaping algorithm in terms of convergence rate. It is found that firefly algorithm is an excellent optimisation tool with respect to fast convergence and locating global optima. It is also very efficient in predicting trends of multi-dependent responses.

In laser beam micromachining process, the quality of the drilled hole is of great importance. The quality of the microdrilled hole mainly depends on appropriate selection of process parameters. Predefined diameter of hole with minimum taper is of today's demand. The composite used for microdrilling operation is alumina–aluminium (Al2O3–Al) interpenetrating phase composite (IPC), which is widely used in aircraft and space stations. Until date, no experimental study has been done to obtain microdrilled hole of desired diameter. In the present paper three hole qualities such as hole diameter at entry, at exit and hole taper have been optimized individually as well as simultaneously using a central composite design (CCD) based on response surface methodology (RSM) during pulsed Nd:YAG laser microdrilling operation on alumina–aluminium IPC sheet of 1.14mm thickness. The analysis of variance (ANOVA) test has also been done to identify the process parameters that contributed the most to get desired hole quality.

Laser micro-drilling is potent enough to replace the mechanical removal methods in many industrial applications especially for machining of difficult-to-cut materials like ceramics and composites. In the present study, laser micro-drilling of alumina has been investigated experimentally. Nd:YAG laser of wavelength of 1.06 µm is used to investigate process parameters such as lamp current, pulse frequency, air pressure and pulse width. Response surface methodology is adapted to perform experimental design and also to develop the mathematical relationships relating input and output process parameters. Since the responses are conflicting in nature, it is difficult to obtain a single combination of cutting parameters satisfying both the objectives in any one solution. Therefore, it is essential to explore the optimisation landscape to generate the set of dominant solutions. Further, this study adapted non-dominated sorting genetic algorithm II (NSGA II) to optimise the responses such that a set of mutually dominant solutions are found.

In this research work, an experimental investigation has been carried out on underwater laser microchanneling on polymethyl methacrylate, using a pulsed Nd:YAG laser system. The underwater laser processing has been used to minimize the heat-affected zone, microcracking and burr formation around the microchannel. The process parameters that have been taken into consideration are lamp current, pulse frequency, pulse width and cutting speed. The microchannel characteristics that have been taken into account as responses are microchannel width, microchannel depth, burr width and burr height. Response surface methodology has been used to develop the mathematical relationships between the process parameters and microchannel characteristics. The adequacies of the models have been tested using analysis of variance. The interaction effects of process parameters on the microchannel characteristics have been analyzed and discussed. In addition to that, single-objective and multiobjective optimization of the process parameters have been performed to obtain desired values of microchannel characteristics.

In the present research, a three-dimensional transient numerical model is developed to simulate the laser transmission welding of circular contours. Polycarbonate, a thermoplastic material, is considered as work material for developing and validating the model. The welding simulation is performed, to compute the temperature distribution and shape and size of the molten pool, using the commercial finite element software ANSYS ® . The results numerical analysis is further used for investigating the parametric effect on temperature field and weld bead profile. The results obtained revealthat laser power has a positive effect on all the responses investigated; whereas, welding speed has a negative effect. For constant line energy, higher temperature is obtained at a combination of high power with high welding speed.

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.

In the present research, laser micro–drilling of alumina has been investigated experimentally. The laser used is Nd:YAG, having a wavelength of 1.06 µm. The process parameters investigated are: lamp current, pulse frequency, air pressure and pulse width. The quality of micro–holes is evaluated by measuring the hole taper and HAZ width. Response surface methodology is adopted to perform the experimental design and also to develop the mathematical relationships relating the input process parameters and output qualities. The adequacy of the models is tested by statistical measures. Finally, the developed mathematical models are used for sensitivity analysis to identify the critical parameters and their tendencies.