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Owing to the growing applications in medical equipment, the marine sector and automotive industries, laser transmission welding (LTW) is gaining increasing importance. LTW of two transparent acrylic thermoplastic materials, each of 4 mm thickness, was demonstrated using a diode laserpumped solid-state Nd:YVO4 pulsed laser. The effect of process parameters such as laser power, pulse frequency and scanning speed have been investigated and a multi-objective optimization based on desirability function technique was used for the betterment of the results. A validation test has been performed which shows that the predicted results are compatible with actual value. Scanning speed was found to be the process parameter that mostly affects the weld strength. A scanning electron microscope (SEM) was used to study the morphology of the weld zone. It was observed from SEM micrographs that the heating zone in the weld area often generates bubbles and ablation which enhance the joining strength. [ABSTRACT FROM AUTHOR]

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]

In the present day situation higher efficiency, better beam quality, reliability and ease of beam delivery through optical fiber have given diode pump fiber laser a potential to perform in a better way than the traditionally used CO2 or Nd:YAG laser in sheet metal cutting operation. Change in focal distance in the downward direction from the top surface in a controlled manner, eliminates the problem of proper focusability which leads to the formation of uniform melt pool throughout the machining period and results in formation of kerf with high aspect ratio. Investigation of the influence of cutting angle and constant z-height movement with other process parameters like cutting speed, pulse frequency, duty cycle and average power related to the kerf deviation and surface roughness of the 1 mm thick 316L stainless steel sheet has been done. Evaluation of the parametric dependent factors of the cut quality has been made by the implementation of response surface methodology (RSM) with the help of design of experiments (DOE). The optimum parametric settings relating to different machining conditions have also been evaluated. [ABSTRACT FROM AUTHOR]

The current research elaborates an experimental study on poly (methyl methacrylate) (PMMA), to produce microchannels using the laser transmission cutting technique, utilizing a nanosecond pulsed Nd:YAG laser system. The cutting operation was carried out in partially submerged condition. The prime objective during the machining operation was to minimize the heat affected zone (HAZ) and kerf width. Lamp current, pulse frequency, pulse width and cutting speed were the process parameters under consideration during the experimentation. The developed microchannels characteristics such as HAZ and kerf width were subsequently measured and analysed. Response surface methodology (RSM) technique was applied to develop the mathematical relationships between the input process parameters and output responses. Model adequacy was tested using the method of analysis of variance (ANOVA). The optimal combinations of process parameter settings were obtained through single and multi-objective optimizations methods. [ABSTRACT FROM AUTHOR]

Laser beam cutting of Inconel 625 superalloy with a Nd:YAG laser in a submerged condition has been studied here. The effect of the underwater laser beam cutting parameters such as lamp current, pulse frequency, pulse width, cutting speed, height of water column on Kerf width and depth of cut are investigated using response surface methodology (RSM). The developed mathematical models are tested by analysis of variance (ANOVA) method to check their adequacy. The central composite design (CCD) technique based on RSM is employed here to carry out the experiments to achieve optimum responses with a reduced number of experiments. From the ANOVA analysis it is found that pulse frequency is the most dominant factor. Height of water column has great impact on quality characteristics of the cut zone. [ABSTRACT FROM AUTHOR]

Nd:YAG lasers are widely used in metal cutting industries; however, they have not yet been fully exploited in creating micro-features on samples because of high heat affected zone (HAZ) and uncontrolled material removal. In this work a Nd:YAG laser has been utilized in creating microchannels on polymethylmethacrylate (PMMA) in submerged water condition. Taguchi methodology with L-16 orthogonal array design has been chosen for performing the experiments. Lamp current, scanning speed, pulse frequency and pulse width has been selected as input process parameters. Width and depth of the microchannels have been taken as output quality characteristics. Analysis of variance has been performed for each quality characteristics to check the compatibility of this methodology. Each quality characteristics has been optimized using Taguchi's technique. Multiple quality characteristics have been optimized using grey based Taguchi technique. Grey based Taguchi technique provides efficient and effective way to optimize the process based on grey relational grades. Underwater laser processing resulted in lowering heat affected zone (HAZ) and debris formation therefore producing clean structures than air. Experiments showed that the process can be readily used in micromachining facilities to create micro-features on materials. [ABSTRACT FROM AUTHOR]