Bappa Acherjee

Optimization of Nd:YAG Laser Parameters for Microdrilling of Alumina with Multiquality Characteristics via Grey–Taguchi Method

In laser microdrilling, the formation of taper and the dimension of the heat-affected zone (HAZ) are important attributes that greatly influence the quality of a drilled hole. In this article, an experimental investigation into Nd:YAG laser microdrilling of alumina is carried out to produce desired high-quality microdrill. Four independently controllable process variables viz. lamp current, pulse frequency, air pressure, and pulse width are considered as input parameters, while hole taper and HAZ width are considered the output parameters. The Taguchi method combined with the grey relational analysis is used as a statistical design of experiment technique to set the optimal process parameters. The objective is set to minimize both quality characteristics, simultaneously. Grey relational analysis is applied to convert the multiple quality characteristics to a single performance characteristic, called grey relational grade. Optimal process parameters are then determined by the Taguchi method using grey relational grade as the quality index. Both of the quality characteristics of drilled holes are improved markedly at the optimal process condition, as verified by an additional confirmation test. This indicates the application feasibility of the grey-based Taguchi technique for continuous improvement of laser microdrilling quality in the manufacturing industry.

Application of artificial neural network for predicting weld quality in laser transmission welding of thermoplastics

The present work establishes a correlation between the laser transmission welding parameters and output variables though a nonlinear model, developed by applying artificial neural network (ANN). The process parameters of the model include laser power, welding speed, stand-off distance and clamping pressure; whereas, the output parameters of the model include lap-shear strength and weld-seam width. Experimental data is used to train and test the network. The present neural network model is used to predict the experimental outcome as a function of input parameters within a specified range. Linear regression analyses are performed to compute the correlation coefficients, to measure the relationship between the actual and predicted output values, for checking the adequacy of the ANN model. Further, a sensitivity analysis is performed to determine the parametric influence on the model outputs. Finally, a comparison is made between the ANN and multiple regression models for predicting laser transmission weld quality. The same data set, which are used to develop the ANN model, are also used to develop the multiple regression models. The simulation data obtained from the neural network confirms the feasibility of this model in terms of applicability and shows better agreement with the experimental data, compared to those from the regression models.

Selection of Process Parameters for Optimizing the Weld Strength in Laser Transmission Welding of Acrylics

In this paper, an experimental investigation into laser transmission welding of acrylics is carried out. The Taguchi method of parameter design is used as a statistical design of experiment technique to set the optimal process parameters. Experiments are designed and conducted by using Taguchis L16 orthogonal array. Maximization of weld strength is selected as the quality target. The signal-to-noise ratio and the analysis of variance are used to find the optimum levels within the window of parameters selected and to identify the order of importance of the process parameters. With the frame of this work the effects of process parameters on weld strength is also discussed. Finally, a confirmation test is conducted, which verifies that optimal laser transmission welding parameters can be determined effectively so as to improve weld strength through the Taguchi method.

Optimal process design for laser transmission welding of acrylics using desirability function analysis and overlay contour plots

In this paper, an attempt is made to set the optimal laser transmission welding parameters to attain a desired weld seam with maximum joint strength. The earlier developed mathematical models are used to optimise the welding process. Design-expert software is used to optimise the process parameters, taking into account two proposed optimisation criteria. Numerical and graphical optimisation techniques are applied. The result of numerical optimisation predicts two pareto-optimal solution sets according to the planned optimisation criteria; whereas, graphical optimisation result produces overlay contour plots, which allow quick visual inspection of the area of desirable response values.

Nd:YAG Laser Microdrilling of SiC-30BN Nanocomposite: Experimental Study and Process Optimization

Nd:YAG laser microdrilling of SiC30BN nanocomposite material is studied here. Taguchi based grey relational analysis is used to simultaneously determine the optimum setting for minimum hole taper and HAZ width. Grey relation analysis is adopted for combining multiple quality characteristics into one integrated numerical value called Grey relational grade. A L27 orthogonal array has been used for conducting experiments. Lamp current, pulse frequency, pulse width, assist gas pressure and focal distance are considered as input process parameters whereas hole taper and HAZ width are considered as machining responses. It is observed that the quality characteristics of drilled micro holes are improved markedly at the optimized parameter settings as compared to quality levels achieved for initial machine parameter settings.

Finite element simulation of laser transmission thermoplastic welding of circular contour using a moving heat source

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.

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

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.

Integrating Taguchi Method with Desirability Function Analysis to Optimize the Laser Transmission Welding Process

This paper presents a hybrid approach based on Taguchi method and desirability function analysis to optimize the laser transmission welding process. The Taguchi L25 orthogonal array, for a four factor five level design, is used for the study. The welding parameters, namely: laser power, welding speed, stand‐off distance and clamp pressure are optimized with considerations of multiple quality characteristics including weld strength and weld width. The multiple quality characteristics are then combined into a dimensionless measure of performance called composite desirability function to simplify the optimization procedure. Subsequently, analysis of variance (ANOVA) is performed to determine the significance of parameters and to identify the optimum levels of parameters based on the composite desirability function. The confirmation experiment at the optimal levels shows that the targeted multiple quality characteristics can be significantly improved to achieve more desirable levels.

Laser Arc Hybrid Welding

The laser arc hybrid welding process utilizes synergic effects of laser welding and arc welding in a common weld pool. This hybridization effect leads to a number of process benefits over laser welding and arc welding, such as higher welding speed, deeper penetration, increased productivity, excellent gap-bridging capability, better process stability, higher process efficiency, etc. This article provides comprehensive knowledge about the laser arc hybrid welding process. The introduction presents an overview of laser arc hybrid welding, which includes operation principle, historical developments, process requirements, advantages, and limitations of this process. The subsequent sections elaborate different variants of the laser arc hybrid welding process. Thereafter, it furnishes a detailed discussion on control parameters that govern the performance of the laser arc hybrid welding process. It is followed by a description about improvements of performance characteristics and weld qualities achieved by using the hybrid welding process, which is evidenced by sufficient research findings. The succeeding section presents a number of examples of industrial applications of laser arc hybrid welding. The final part of the article provides the concluding remarks.

Quality improvement of electrochemical discharge machining process using firefly algorithm: a case study

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.