Arunanshu S. Kuar

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.

Effects of Process Parameters on Hole Circularity and Taper in Pulsed Nd:YAG Laser Microdrilling of Tin-Al2O3 Composites

This study investigates the effect of five parameters on circularity and taper of drilled holes in pulsed Nd:YAG laser microdrilling process. The effect of various process parameters like lamp current, pulse frequency, pulse width, air pressure, and focal length of Nd:YAG laser microdrilling on hole circularity at entry, exit, and taper has been investigated through response surface methodology (RSM)–based experimental study. The significant parameters have been selected based on the analysis of variance (ANOVA). The parametric combination for optimal hole circularity and hole taper has also been evaluated. In micromanufacturing, circularity of a drilled hole at entry, exit, and taper are important attributes which greatly influence the quality of a drilled hole. The drilling operation has been carried out on titanium nitride-alumina (TiN-Al2O3) composite, an important electroconductive ceramic suitable for wear and heating applications.

An experimental investigation on Nd:YAG laser microchanneling on polymethyl methacrylate submerged in water:

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.

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.

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.

Sensitivity Analysis of Submerged Laser Beam Cutting on Inconel 625 Superalloy

This chapter presents laser beam micro-cutting along with sensitivity analysis of process parameters related to the submerged laser micro-cutting of Inconel 625 superalloy. Initially, a discussion of different kinds of laser beam cutting and its application are mentioned here. Then, one of the main difficulties pertaining to laser macro/micro-cutting has been discussed here along with the remedies suggested in terms of modification in laser cutting techniques, i.e. underwater laser cutting. Sensitivity analysis of controllable process variables, such as lamp current, pulse frequency, pulse width, cutting speed, height of water column on machining criteria in terms of heat -affected zone (HAZ) width during laser beam cutting of Inconel 625 superalloy at submerged condition has been performed. The central composite design (CCD) technique based on response surface methodology (RSM) is adopted to carry out the experiments to achieve optimum responses with a reduced number of experiments. Mathematical model is developed and further used to conduct sensitivity analysis. It has been found that HAZ width is sensitive to pulse frequency, pulse width and height of water column in their positive values whereas it is negatively sensitive to lamp current in the chosen design space. HAZ width is noted to be least sensitive to cutting speed.

Experimental Investigations into Underwater Laser Transmission Micro-channeling on PMMA

Laser beam micro-channeling process has an immense potential for the fabrication of microfluidic devices which are instrumental for various biomedical applications such as electrophoresis, chromatography, blood protein analysis, DNA studies, micro-total analysis systems, etc. In the current study, an attempt has been made to fabricate micro-channels in a thick polymethyl methacrylate (PMMA) plate having 11.328 mm thickness at partially submerged condition by utilizing laser transmission micro-machining technology. An Nd:YAG laser source has been employed with a wavelength of 1064 nm. The working power is used for which the micro-channel fabrication varies between 9 and 11 W, pulse frequency varies between 25 and 45 kHz, pulse width varies between 90 and 98% of the duty cycle, and cutting speed ranges from 1.00 to 2.00 mm/sec. The effects of parameters on heat-affected zone (HAZ) width during laser transmission micro-channeling have been investigated. Totally, 31 experiments have been designed and performed with the aid of central composite design technique based on response surface methodology (RSM). Finally, optimization of the aforesaid process parameters has been performed in order to achieve minimum dimension of HAZ width within the predefined design space, for utilizing in various microfluidic applications.