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Micro-electro-discharge drilling (μ EDD) is a type of non-traditional machining process used for drilling micro-holes of desired dimensions with a high aspect ratio. But, there are no such research works that could have explained the desired accurate circular shape of micro-holes. The need for a more advanced hybrid machining process to improve the overall efficiency in terms of mainly desired circular shape and radial overcut is evolved. In this research work, an electromagnetic field force-assisted micro-EDM process has been carried out on Inconel 800 with a copper tool of 450 μ m. Experimental results showed that measured metal removal rate and tool wear rate decreased for ascending values of magnetic flux density, peak current and gap voltage, whereas circularity increases linearly with an increase in magnetic flux density and also the effects of magnetic field on circularity of micro-holes on Inconel 800 are more predominant than other parameters. [ABSTRACT FROM AUTHOR]

Laser marking is the process to mark an image by utilizing laser thermal energy used primarily for product identifications and traceability. It is versatile and well known process employed by the manufacturers to mark various materials. The mark produced by a fibre laser beam produces one of the fine marking components and it is well accepted form of marking used nowadays. The research paper revealed that laser beam marking quality is the function of various input controlling factors like laser spot size, transverse feed, scan rate, laser power which had a significant impact on quality attributes. The paper focuses on the creation of better quality equilateral triangular-shaped laser inscribed image on grade 304 stainless steel surface in a shortest possible time. The process variables involved in the present study includes pulse rate, duty cycle, laser power, and scan rate which were varied one at a time for obtaining better marking quality characteristics like high mark quality, closer to target mark angle and less deviation of marked area. The observed results revealed that pulse rate of 50 kHz, laser power of 12.5 W, scan rate of 35 mm/s and duty cycle of 99% provides better marking quality. [ABSTRACT FROM AUTHOR]

The operation of laser marking occurs due to oxidation on the metallic surface at a high temperature, which finds applications in many organisations due to its cleanness and high handling speed with the negligible human association. The generated marked objects are permanent in nature, generally utilised for product identity. From the perspective of laser marking, the general requirement of laser marking is mark clarity or marking quality with minimal effect on the workpiece surface. The paper deals with producing good-quality laser-marked surface by the utilisation of process parameters such as transverse feed, average laser power and scanning speed, which seem to have a significant effect on the surface of designed materials for the development of laser marking qualities. The diode-pumped pulsed fibre laser was utilised for the purpose of marking on the surface in a single pass within the minimum possible time. Experimental studies revealed that decrease in transverse feed from 8 μm to 2 μm/laser stroke had a projection towards the increase in mark intensity which could be reached up to 0.95 on the application of the lower value of transverse feed, i.e., 2 μm/laser stroke upon using a proper set of process parameters.. [ABSTRACT FROM AUTHOR]

Laser spiral microgrooving is a new technology for the micromachining of advanced engineering materials like Al2O3, ZrO2, Al2TiO5, AlN, etc. Due to better accuracy, nowadays the micromachining of aluminium is widely used in various industries. This paper details the study of laser spiral microgrooving process on cylindrical shaped pure aluminium. In this study average power, pulse frequency and workpiece rotational speed are considered as the process variables. The mathematical formulations of laser spiral microgrooving process which correlate the different process parameters and spacing between two consecutive microgrooves have been developed. The geometrical dimensions of the microgroove like groove width and groove depth are measured by using an optical microscope. Microscopic images of microgrooves using high resolution optical microscope are also studied to examine the effect of several process variables on the spiral microgroove dimensions. [ABSTRACT FROM AUTHOR]

This research work explores the feasibility of drilling micro-holes on Ti6Al4V by applying a sequential electro-micro-machining process. A novel sequential combination of micro-electrochemical discharge machining (μ ECDM) and micro-electro-chemical machining (μ ECM) is applied for drilling micro-hole in titanium alloy (Ti6Al4V). The machining of titanium alloy by a μ ECDM process is a challenging task and not reported yet. Therefore, the feasibility of machining of Ti6Al4V by μ ECDM using various combinations of electrolytes has been studied. The best-suited electrolyte for drilling by μ ECDM was selected by analyzing the hole depth, radial overcut, hole taper angle and the minimum time required to drill through holes in a 400 μ m thick sheet of titanium alloy. The μ ECDM process produces micro-holes rapidly but it consists of recast layer, micro-cracks, and heat affected zone, etc. The surface characteristics of a μ ECDMed hole were improved by applying μ ECM process subsequent to the μ ECDM process. The sequential combination of μ ECDM shaping and μ ECM finishing results in improved dimensional accuracy, machining depth, taper angle, and surface quality of the hole produced by sequential micro-machining process. [ABSTRACT FROM AUTHOR]

Byline: B. Doloi, D. Dhupal, B. Bhattacharyya Pulsed Nd:YAG laser beam is widely applied in micro-machining with different micro-scale geometries on engineering materials such as ceramics, composites, and diamond. The present research papers deals with the Response Surface Methodology (RSM) based mathematical modelling and analysis on machining characteristics of pulsed Nd:YAG laser during micro-grooving operation on flat surface of aluminium titanate. An attempt has been made to optimise laser parametric setting for achieving accurate taper angles of micro-grooves. Based on the modelling and parametric optimisation analysis, the optimal laser process parametric setting has been obtained as air pressure of 0.9 kg/cm[sup.2], lamp current of 20.4 amp, pulse frequency of 2.8 kHz, pulse width of 2.7% of duty cycle and cutting speed 10 mm/s for achieving the optimum taper angle of 11.1[degrees].

Byline: B.R. Sarkar, B. Doloi, B. Bhattacharyya Electrochemical Discharge Machining (ECDM) process has great potential to machine electrically non-conducting engineering ceramics and can be applied for micro-machining operation. This research paper includes the experimental investigation to study the range of the parametric setting for micro-machining operation as well as the effect of various process parameters such as applied voltage, electrolyte concentration and inter-electrode gap on Material Removal Rate (MRR), Radial Over-Cut (ROC) and Heat Affected Zone (HAZ) thickness during micro-drilling of non-conducting engineering ceramic materials such as Aluminium Oxide and Zirconium Oxide. The experiments have been performed using electrolyte of KOH and NaOH salt solution. In this paper, an experimental investigation has been made to find out the optimum value of ECDM process parametric conditions for higher MRR, lower overcut and also lower HAZ thickness during micro-drilling on ceramics. The quality of the hole during micro-drilling greatly depends on the applied voltage and electrolyte concentration.

Byline: A.S. Kuar, B. Doloi, B. Bhattacharyya A laser beam has great ability to machine very hard conductive as well as non-conductive materials such as high speed steel, ceramics, and diamonds, etc. The present paper includes the parametric analysis on performance of CNC pulsed Nd:YAG laser cutting operation on silicon nitride ceramics. The present experimental investigations reveal that the saw cutting operation on silicon nitride can be successfully performed with a better surface finish after proper setting of the machining parameters. The cut quality of the job surface has been presented and analysed through microscopic views. Better quality of the cutting edge can be achieved during the Nd:YAG laser cutting operation when the lamp current, cutting speed and pulse frequency are set at moderate values.

Wire electrochemical machining(WECM)is a recently introduced fabrication processwhich is yet to be fully investigated. Preliminary studies have shown that it offers superior feasibility and capability concerning the fabrication of various microfeatures. More extensive investigations are needed to discover any associated problems with the process and to extend its applicability and efficiency by determining its limitations in order to make this process a successful fabrication technique not only in microdomains but also for macro fabrications as well. Here we begin with a detailed overview of the fundamental and technological aspects of the WECM process. We then discuss its mass transfer strategies and kinematics, which are equally important as associated operating parameters, as well as the apparatus, materials, and machining conditions, challenges, and applications. Finally, we note recent advances to guide upcoming research attempts and future investigations aimed at making this anodic dissolution process proficient and established. [ABSTRACT FROM AUTHOR]

Developing tools for ultrasonic machining processes is one of the most challenging tasks, because the shape of the machined surface of the workpiece is a replica of the tool surface. In this research, using reverse engineering (RE), the tool has been designed and fabricated for the ultrasonic machining (USM) process. Zirconia is a very hard and brittle bio-ceramic material and is highly biocompatible. Nowadays, zirconia material is used for producing the acetabular cup for hip joint. In this research work, an attempt has been made to apply the RE for developing the CAD model of a USM tool from the existing hemispherical shape cavity on a zirconia workpiece. Experimental analysis has been undertaken for generating the hemispherical shape cavity on zirconia bio-ceramics with the help of these developed tools. Through a number of graphical plots, comparisons of diametrical deviation and circularity error have been made using RE and without RE. Comparisons have also been made for justifying the accuracy of the tool development by RE with respect to the initial existing hemispherical shape cavity and developed tool for USM. [ABSTRACT FROM AUTHOR]

An attempt has been made to apply the Taguchi parameter design method and multi-response optimization using desirability analysis for optimizing the cutting conditions (cutting speed, feed rate and depth of cut) on machining forces while finish turning of AISI 4340 steel using developed yttria based zirconia toughened alumina inserts. These zirconia toughened alumina inserts were prepared through wet chemical co-precipitation route followed by powder metallurgy process. The L9 (4) orthogonal array of the Taguchi experiment is selected for three major parameters, and based on the mean response and signal-to-noise ratio of measured machining forces, the optimal cutting condition arrived for feed force is A1, B1 and C3 (cutting speed: 150 m/min, depth of cut: 0.5 mm and feed rate: 0.28 mm/rev) and for thrust and cutting forces is A3, B1 and C1 (cutting speed: 350 m/min, depth of cut: 0.5 mm and feed rate: 0.18 mm/rev) considering the smaller-the-better approach. Multi-response optimization using desirability function has been applied to minimize each response, that is, machining forces, simultaneously by setting a goal of highest cutting speed and feed rate criteria. From this study, it can be concluded that the optimum parameters can be set at cutting speed of 350 m/min, depth of cut of 0.5 mm and feed rate of 0.25 mm/rev for minimizing the forces with 78% desirability level. [ABSTRACT FROM AUTHOR]

The essence of the “ratio data” in cellular manufacturing system has rarely been correctly emphasized since past few decades of research and study. This article is an attempt to deal with cell formation problem which exploits machine utilization percentage and eliminates the “fuzziness” on the subject of ratio data. In the course of this study, a distinctive technique is adopted based on multi-criteria decision technique with significant modifications which is experimented on test data and compared with published methodology. To verify the grouping result, a novel performance measure is proposed and elaborated analytically to establish its superiority and robustness over the earlier efficiency measures published in the past literature of cellular manufacturing system. The novelty of this research remains in eradicating ambiguities on the subject of “ratio data,” imposing appropriate rules while generating the test problems, catering a unique multi-criteria decision technique–based approach and a novel performance measure for the aforesaid problem. [ABSTRACT FROM AUTHOR]

Zirconia (ZrO2) is a highly biocompatible ceramic material providing fracture strength properties that allow application as dental implants in biomedical engineering. In this present research, experimental analysis has been made for generating stepped hole on zirconia bioceramics with desired quality using ultrasonic machining (USM) process. Four independent controllable input process parameters are abrasive grain diameter, power rating, concentration of abrasive slurry, and tool feed rate. Material removal rate (MRR), overcut of larger diameter (OLD) hole, and overcut of smaller diameter (OSD) hole of stepped hole are considered as the responses. Response surface methodology (RSM) is used for modeling the performance of USM process. Multiobjective optimization has been performed to maximize the MRR and minimize the OLD hole and OSD hole of stepped holes. All the responses are improved at the optimal parametric condition and verified by confirmation test. The present research opens up the application feasibility of USM process for stepped hole generation on bioceramics and its utilization in biomedical field. [ABSTRACT FROM AUTHOR]

Laser micro-turning process is one of the latest and emerging technologies in the field of laser materials processing of engineering materials. The present paper deals with experimental investigation on Nd:YAG laser micro-turning operation of cylindrical shaped Al2O3 ceramic to explore the effect various significant process parameters such as laser beam average power, workpiece rotating speed, axial feed rate, pulse frequency and assist air pressure. Experiments were conducted considering the response surface methodology (RSM) based design of experiments (DoE). Mathematical models were developed for the responses; namely, surface roughness (Ra) and depth deviation. The validity and correctness of the developed mathematical models is carried out through analysis of variance (ANOVA) test. The target surface roughness and machining depth are as 6.0 and 100.0 μm, respectively. To achieve these target criteria, optimum parametric combination is found through RSM. [ABSTRACT FROM AUTHOR]

Experimental studies of fibre laser microchanneling on polymethyl methacrylate (PMMA) sheets at atmospheric conditions intend to find out the effect of various process parameters on the response criteria: depth and width of the microchannels and the widths of the heat affected zone (HAZ). A basic experimental study has been reported for the microfabrication of PMMA microchannels to utilize them for various microfluidic applications. The significance of the current research work is not only confined to facilitate the fibre laser system for microfluidic applications, but also to improve the aspect ratios (microchannel depth/width) of the fabricated microchannels as well as to identify significant reduction of HAZ from the microchanneling zones. The various process parameters: scan speed; average power; pulse frequency and number of passes with different ranges, were considered to achieve the aforementioned response criteria. The range of the process parameters includes scan speed of 10 to 300 mm/s, pulse frequency of 50 to 90 kHz, average power of 5.0 to 15.0 W and number of passes of 1 to 5; while pulse width was held constant at 90% of the cycle time. The experimental research work also includes the physical phenomena behind the fibre laser microchanneling of PMMA as well as the intricate analyses and explanations of each process parameter on the outcome of the microchannel geometries. [ABSTRACT FROM AUTHOR]

Microgrooves are one of the basic microfeatures fabricated on different microproducts, used to integrate micro systems in various fields. Service life and product functioning of microproducts are directly influenced by shape, size, and surface quality of microgrooves fabricated on it. Hence, these are the important criteria to be considered while fabricating microgrooves on micro devices. This article presents the experimental study into fabrication of microgrooves on stainless steel by electrochemical micromachining. The influence of electrochemical micromachining process parameters like applied voltage, pulse frequency, duty ratio, electrolyte concentration, and microtool scanning speed on machining accuracy, that is, width overcut, length overcut and depth overcut, material removal rate, linearity of microgroove, depth profile, and surface finish were investigated during microgroove generation. From the experimental results, optimal parameters obtained were applied voltage of 2.6 V, pulse frequency of 8 MHz, 30% duty ratio, electrolyte concentration of 0.15 M H2SO4, and microtool scanning speed of 93.75 μm/s for machining of accurate microgroove, with best surface finish. Finally, microfeatures like “C”-shaped microgroove of rectangular cross section and multiple microgrooves as required in micro thermal devices have been machined with optimal parametric settings. This study will be useful for machining of need-based microgrooves on microproducts like micro actuators, micro pumps, micro coolers, and micromixers. [ABSTRACT FROM AUTHOR]

Travelling wire electrochemical discharge machining (TW-ECDM) has great potential for machining advanced non-conducting materials such as zirconia, alumina, silicon nitride, diamond glass, rubies and composites such as FRP etc. Composite materials possess higher strength, stiffness, and fatigue limits which enable structural design more flexible than with conventional metals. Over recent years precision machining of composite materials has gained in importance. The presented research paper includes a description of an indigenously developed TW-ECDM set-up for performing experiments on composite materials such as fibre reinforced plastic. This paper also presents analyses of machining parameters such as material removal rate and radial overcut for different input parameters such as pulse on time, frequency of power supply, applied voltage, concentration of electrolyte and wire feed rate. Taguchi method-based optimization analysis was also done for achieving minimum radial overcut and maximum material removal rate during the cuttings of grooves on Hylam based fibre reinforced composites. Multiple regression models were also established for both material removal rate and radial overcut by considering the more important process parameters for cutting grooves on Hylam based fibre reinforced composites. Finally, a back propagation neural network was applied for predicting the responses and those predictions are compared with the experimental results. [ABSTRACT FROM AUTHOR]

Abstract: One of the emerging laser material processing technologies to process cylindrical shaped materials is the laser micro-turning process. This process is used to machine micro-turned groove or surface on the difficult-to-process materials for a specific length of turn along its axis. The present experimental study investigates the laser micro-turning operation of a cylindrical shaped aluminum oxide (Al2O3) ceramic to explore the effect of successive spot overlap and circumferential overlap on the surface roughness (Ra) criterion. Moreover, depth of machining has also been studied by varying various process parameters such as pulse frequency, workpiece rotating speed and laser beam average power. Various amounts of spot overlap have been accomplished by different combined settings of related parameters i.e. workpiece rotating speed and pulse frequency. In contrast, various circumferential overlap between successive rotational scan widths have been achieved by varying the rotational speed and also axial feed rate of the workpiece. Surface roughness (Ra) and machined depth have been measured as output response for machining at various parametric combinations. Analyses have been made through different plots of surface roughness (Ra) and machined depth to study the influence of these overlaps and different process parameters. The experimental results revealed that surface roughness decreases with the increase of both the overlap factors. It is observed from the results that with the increase in circumferential overlap, roughness of the machined surface decreases for each workpiece rotating speed setting. Further, wide spot crater is achieved at a higher value of average power. Minimum surface roughness is achieved as 5.25µm at average power 10W, pulse frequency 3000Hz, workpiece rotating speed 400rpm and Y feed rate 0.3mm/s. The achieved machined depth is high at a low speed of rotation and pulse frequency settings. With the increase of average power of laser beam, the machined depth is found to increase linearly. The maximum micro-turning depth is achieved as 0.146mm at parametric combination of average power of 10W, pulse frequency of 3000Hz, workpiece rotating speed of 400rpm and Y feed rate of 0.3mm/s. [Copyright &y& Elsevier]

This paper presents a new approach for sidewall insulation of microtool by dip coating using liquid solution made of polymer and resin dissolved in isopropyl alcohol and use of acetone for opening the front end of the microtool. This method can also be used to remove the previously applied coat completely so that the microtool can be reinsulated again for the reuse. To investigate the effectiveness of insulating film, in-situ fabricated tungsten microtool of 104 µm diameter was insulated with 4.5-µm thick film by proposed method. Microfeatures like microhole and microgroove were machined by electrochemical micromachining (EMM) using uninsulated microtool and insulated microtool on stainless steel. The machining accuracy of the microfeatures machined were compared in terms of overcut and taper angle generated on microfeatures. In this way, 33.78% reduction in radial overcut of microhole and 58.64% reduction in width overcut of microgroove were observed. Taper angle was reduced from 40.57° to 18.00° and 58.39° to 25.20° for microhole and microgroove, respectively. The influence of sidewall insulation on shape accuracy, machining rate, and surface roughness of machined microfeatures was also investigated. [ABSTRACT FROM AUTHOR]