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Laser transmission welding (LTW) is widely recognized as an effective joining method for thermoplastic polymers. Excellent mechanical, physical and thermal properties of polypropylene makes it suitable for many application in aerospace, automotive manufacturing and laboratory accessories; however, joining of semi-crystalline and amorphous polymers is very difficult due to their poor compatibility or different crystal structure. To overcome this problem, white ink is applied at the interface of weld to increase the solubility and retain the laser heat input. As white ink is an opaque, containing copolymer resins which helps to enhance the bonding strength. Here, acrylic (amorphous) and polypropylene copolymer (PPCP) (semi-crystalline) each of 4 mm thickness have been joined by low power diode laser. Experimental analysis of the effect of process parameters such as laser power, scanning speed and pulse frequency on the weld zone has been studied. Greater weld strength is achieved at low scan speed. A novel multi objective snap drift cuckoo search (SDCS) optimization technique has been implemented for betterment of weld strength and weld width. A scanning electron microscope (SEM) has been used to observe the welded zone morphology. It is observed that weld strength is primarily dependent on mechanical interlocking between the two layers of polymers. [ABSTRACT FROM AUTHOR]

Laser based micro-channeling is emerging as the most widely used process for fabrication of polymer based micro-fluidic devices. Nd:YAG lasers are one of the most favoured laser system by industries involved in laser based material processing. However, they have not been fully explored for micro-level processing. In this research work, Nd:YAG laser has been utilized in fabrication of micro-channels on PMMA in underwater condition. The input parameters have been chosen as lamp current, scanning speed, pulse frequency and pulse width. Depth, burr height and burr width of the micro-channel have been taken as output quality characteristics. Taguchi methodology in combination with grey relational analysis has been employed to determine the optimal parametric condition for satisfying multiple objectives at same time. Underwater laser processing has resulted in minimization of undesirable effects of laser processing like heat affected zone and redeposition around the micro-channels resulting in cleaner and finer structure than open air processing. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, an experimental investigation on diode laser transmission welding of dissimilar thermoplastics between PMMA (polymethyl methacrylate) and ABS (acrylonitrile butadiene styrene) has been carried out. The effect of the laser welding parameters such as laser power, welding speed, stand-off distance and clamp pressure on weld strength and weld width is investigated using response surface methodology (RSM). Planned experiments and subsequent analyses are carried out to develop the mathematical models to establish the correlation between the process parameters and the responses. The adequacy of the developed models is tested using the sequential F-test, lack-of-fit test and the analysis-of-variance (ANOVA) technique. A numerical multi-objective simultaneous optimization technique, in which the RSM is incorporated, is used to find the optimum solutions, according to the desired optimization criteria. In addition to that, a graphical optimization technique is, also implemented which allow identifying a region in the graphic where optimal conditions lay on. [Copyright &y& Elsevier]

Abstract: In this paper, simultaneous laser transmission welding process is systematically investigated via process modeling, using an FEM and RSM combined approach. The objective of the present research is to study the effects of process parameters on the temperature field and weld bead dimensions. The thermal field is simulated by solving a three dimensional transient heat diffusion equation with temperature dependent material properties using the ANSYS® multi-physics. Response surface methodology is then applied for developing mathematical models based on simulation results. The second order equations developed by RSM can predict the values of the responses with significant accuracy. The effect of parameters and their interactions on the responses are studied using the developed response surface models. The mathematical models are further used in search of the optimal process window for obtaining an acceptable weld. The graphical optimization results into a couple of overlay contours plots, which allow quick visual inspection of the area of feasible response values in the factor space to choose the favorable welding parameter combination. [Copyright &y& Elsevier]