Showing papers in "International Journal of Precision Technology in 2017"

Optimisation strategies in ultrasonic vibration assisted electrical discharge machining: a review

Abstract: In this paper, an attempt has been made to review the literature on strategies formulated and tested in ultrasonic vibration assisted electrical discharge machining (USEDM). The strategies for optimisation of EDM performance include flushing, dimensional accuracy, cavitation, surface morphology, polluted gases and chemical effects etc have been highlighted. The major performance controllable parameters in EDM process have also been discussed in this study. The main emphasis is given on classification of USEDM process on the basis of mode of ultrasonic vibration (UV) action imparted to EDM system, which includes a tool, work piece and the dielectric medium. The ultimate purpose of this study is to generalise the variable relationships of various proposed strategies, which may be applied in industries to improve the performance of USEDM. At the end of this study, some limitations of implementing ultrasonic vibration in EDM have been discussed.

Analysis on electrochemical discharge machining during micro-channel cutting on glass

Abstract: Modern industrial field of micro-machining has an attractive attention to increase the machinability of electrically non-conducting materials. Electrochemical discharge micro-machining process has the ability to machine high strength non-conducting brittle materials like glass. This paper shows a development of second-order correlation between the various machining criteria and different process parameters such as applied voltage, electrolyte concentration and inter-electrode gap (IEG). The analysis of variance (ANOVA) has been performed to find out the adequacy of the developed models. The research paper includes the effects of various process parameters on material removal rate (MRR), overcut (OC), heat affected zone (HAZ) and machining depth (MD) during micro-channel generation on glass. This paper also represents the single as well as multi-objective optimised results to determine the suitable parametric combination for maximum MRR and machining depth and minimum overcut and HAZ area using response surface methodology (RSM) and genetic algorithm (GA).

Development of high speed closed loop operation for single notch flexure-based nanopositioning system

Abstract: Nanotechnology is widely adapted in many industries for various applications such as manufacture of computer disks, semiconductor devices, medicine, biotechnology and so on. To manufacture such systems, nanopositioning stages are extremely critical as they deliver accuracies up to a few nanometres required in such ultra precise process. Nanopositioning stages are widely used as positioning systems in nanotechnology applications such as lithography, high-end microscopes, testing equipments, etc. The proposed work is aimed to design, fabrication and implementation of closed loop three directional flexure-based nanopositioning stage with improved positioning accuracies. The main challenge for designing a nanopositioning system is to minimise the non-linearities, cross-talk and hysteresis to achieve nanometric motions and to provide high bandwidth for scanning operation through closed loop operation. The static and dynamic testing results of nanopositioning stage shows that system can be used for high speed scanning applications.

A thermo temporal model of pulsed laser ablation of copper coated thin films on a polyimide substrate

Abstract: A heat transfer model of nanosecond laser irradiation on a copper thin film coated on a polyimide substrate is developed and studied to understand the thermal influence on thin films during the laser ablation. Temperature distribution inside the target is calculated using heat conduction equation considering hydrodynamic boundary conditions. Effect of plasma shielding on the ablation process due to inverse bremsstrahlung is considered in the model. The study clearly shows that the shielding effect of plasma decreases the laser energy reaching the target surface and therefore reduces the depth of micro crater formed by a single pulse. A comparative study has been made for depth achieved for micro-craters fabricated on copper thin films in air using a Q-switched Nd3+:YAG laser with 6 ns pulse duration for various laser intensities. The simulation results are compared with experimental data for the laser ablation depth which is measured using 3D optical non-contact profilometer.

Micro hole fabrication on quartz using ultrasonic micromachining process

Abstract: Ultrasonic micromachining (USMM) has immense potential for micro-machining on quartz which is used in different field of applications such as optics, metrology and micro electro mechanical system (MEMS) etc. In this paper the influences of process parameters such as power rating, abrasive slurry concentration and tool feed rate on material removal rate (MRR), overcut and taper angle of the micro hole on quartz by USMM have been investigated. Stainless steel of grade 304 has been selected as the micro-tool material for ultrasonic micro drilling on quartz. The higher value of MRR of 0.4235 mm/min has been obtained at power rating of 400 W, abrasive slurry concentration of 40% and tool feed rate of 1.2 mm/min. The lower value of overcut of 55 µm and taper angle of 0.600 of micro hole have been obtained at abrasive slurry concentration of 20%, power rating of 300 W and tool feed rate of 1 mm/min.

Multi-performance optimisation of micro electro-discharge machining during deep micro-slots fabrication using foil tool electrode

Abstract: This study attempts to investigate and optimise the effects of process parameters like voltage, sensitivity, duty factor and capacitance on performance characteristics such as material removal rate (MRR), tool wear rate (TWR), width expansion, length expansion and depth of slot during fabrication of deep and long micro-slots on brass work material by micro electro-discharge machining (micro-EDM). Copper foil is used as tool electrode of thickness 240 μm and width of 8 mm shaped by wire-cut electro-discharge machining. The randomised experiments were performed twice and mean response is considered for analysis to achieve accuracy in the results. Single-optimal parametric setting conditions obtained from the grey relational analysis (GRA) and confirmatory test results showed an improved machining performance of the process. Capacitance is observed to be the most influencing parameter followed by duty factor, sensitivity and voltage. Also, the feasibility of copper foil as a tool electrode is analysed and found high machining rate with more accurate micro-feature geometry.

Influence of wire electrochemical machining parameters during fabrication of micro features

Abstract: Fabrication of various complex 3D micro features has become a prime issue where modern fabricators are facing problems due to the limitations of different manufacturing processes employed. Hence, this paper aims to develop a suitable wire electrochemical machining (WECM) setup for fabricating micro slits on stainless steel (SS 304) sheet and to investigate the influence of WECM process parameters such as frequency and voltage on slit width by implementing combined flushing strategies like wire vibrations with piezo electric transducer (PZT) and axial electrolyte flow that has been found to be very effective. To further minimise the width of the micro slit; experiments have been conducted with in-situ fabricated tungsten (W) wire of 23.98 μm and 31.74 μm diameter. The experimental results have been represented graphically where the minimum slit width is 50.03 μm. Moreover, complex microfeatures have been fabricated by varying the voltage values at 6 V and 7 V.

Machining guidelines for fabricating microgrooves of varied cross-sections by electrochemical micromachining

Abstract: Increased surface area at the cross section of varied cross-sectional microgroove improves the product performance; hence, complex microgrooves of different cross sections are machined on various micro-products. Fabrication of straight microgroove on metallic surfaces is simple, whereas machining of varied cross-sectional microgroove on metallic surfaces becomes the challenging task from the aspects like fabrication of complex shaped microtool and suitable microgroove manufacturing process. Very few methods are capable to machine such complex shaped microgrooves. This chapter explores the potential of machining varied cross-sectional microgrooves on metallic surfaces by electrochemical micromachining. Important process parameters such as applied voltage, duty ratio and machining time have been controlled along the depth while machining the microgrooves. Influences of these parameters on width have been investigated, and results have been applied to devise the machining guidelines to fabricate varied cross-sectional microgrooves. The guidelines for machining straight, reverse tapered, barrel-shaped, double stepped, spherical based and microgroove with internal pocket have been developed. Finally, fabrications of these microgrooves have been demonstrated successfully by following developed guidelines. The developed guidelines can be applied for machining complex microgrooves for micro-coolers, micro-reactors and micro-mixers that need definite shape and size for their working.

Comparison of machining performance of hole-sinking micro-EDM without and with ultrasonic vibration on titanium alloy

Abstract: Titanium alloys are highly demanding in aerospace industries due to its high strength-to-weight ratio and high hot hardness, and termed as difficult-to-machine materials. Creating microholes of high accuracy in these materials is challenging task for manufacturing industries. Conventional twist drills are generally failed in the micromachining of Titanium alloys due to the low thermal conductivity of these alloys. In consideration of all these problems, authors used self-developed hole-sinking micro-EDM (HS-MEDM) setup without and with the assistance of ultrasonic vibration (UV) to create microholes in Titanium alloy (Ti-6Al-4V) workpiece. Comparative study regarding machining performance in terms of material removal rate (MRR), tool wear rate (TWR), hole taper (Ta) and overcut (OC) at different gap current, pulse on-time and pulse off-time has been reported without and with assistance of UV. It was found that HS-MEDM with UV is more advantageous in producing microholes with higher MRR, lower TWR, Ta and OC, and smoother surface.

Effect of electrolyte temperature on Faradaic effect in electrochemical microdrilling

Abstract: Electrochemical micromachining (ECµM) is an emerging non-conventional manufacturing technology suitable for the fabrication of micro-sized components on a wide range of electrically conductive materials. This study emphasises on the effects of electrolyte temperature on the Faradaic effect during electrochemical microdrilling on nickel plates by a cylindrical microtool made of tungsten. A short cylindrical microtool of 43 µm in diameter near to the tool tip and 53 µm mean diameter was selected, and allowed to machine on nickel plate. During machining, only the electrolyte temperature was varied keeping all the other parameters constant. The shape and size of the fabricated microholes, machining time, actual material removal rate, non-Faradaic non-transient effect and the number of short circuits are considered as response factors. Experimental results confirm that the material removal rate and machining time, respectively, increases and decreases with an increase in the electrolyte temperature. It is also observed that both the side gap ratio and the taper angle increase with the electrolyte temperature.