Free abrasive wire saw machining of ceramics

Currently, many kinds of ceramics are used in advanced industrial fields due to their superior mechanical properties, such as thermal, wear, corrosion resistance, and lightweight features. Wire saw machining ceramic (Al₂O₃) was investigated by ultrasonic vibration in this study. Taguchi approach is a powerful design tool for high-quality systems. Material removal rate, wafer surface roughness, steel wire wear, kerf width, and flatness during machining ceramic were selected as quality character factors to optimize the machining parameters (swinging angle, concentration, mixed grain and direction of ultrasonic vibration) to get the larger-the-better (material removal rate) and the smaller-the-better (wafer surface roughness, steel wire wear, kerf width and flatness) machining characteristics by Taguchi method. The results indicated that wire swinging produces a higher material removal rate and good wafer surface roughness. Ultrasonic vibration improved material removal rate, without affecting the flatness under different machining conditions. Experimental results show that the optimal wire saw machining parameters based on grey relational analysis can be determined effectively and material removal rate increases from 2.972 to 3.324 mm²/min, wafer surface roughness decreases from 0.37 to 0.34 μm, steel wire wear decreases from 0.78 to 0.77 μm, kerf width decreases from 0.352 to 0.350 mm, and flatness decreases from 7.51 to 7.22 μm are observed.     

Effect of electrode material in wire electro discharge machining characteristics of Ti50Ni50−xCux shape memory alloy

TiNiCu alloy belongs to new class of shape memory alloy (SMA), which exhibits superior properties like shape memory effect, super elasticity and reversible martensitic transformation phase and thus find broad applications in actuators, micro tools and stents in biomedical components. Even though, SMA demonstrates outstanding property profile, traditional machining of SMAs is fairly complex and hence non-traditional machining like wire electric discharge machining (WEDM) has been performed. Hence, there is a need to investigate the WEDM performance characteristics of shape memory alloys due to excellent property profile and potential applications. In the present investigation, various machining characteristics like material removal rate (MRR), surface roughness, surface topography and metallographic changes have been studied and the influence of wire material on TiNiCu alloy machining characteristics has also been evaluated through ANOVA. Ti₅₀Ni_50−xCu_{x=10, 20} was prepared by vacuum arc melting process. The proposed alloy as-cast material exhibits austenite property (B2 phase) and having higher hardness when compared to TiNi alloy. The investigation on WEDM of Ti₅₀Ni_50−xCu_x alloy reveals that the machining parameters such as servo voltage, pulse on time and pulse off time are the most significant parameters affecting MRR as well as surface roughness using both brass and zinc coated brass wires. However, machining with zinc coated brass wire yields reduced surface roughness and better MRR and also produces less surface defects on the machined surface of Ti₅₀Ni_50−xCu_x alloys.     

RESPONSE SURFACE ANALYSIS OF SLICING OF SILICON INGOTS WITH FOCUS ON PHOTOVOLTAIC APPLICATION

Polycrystalline silicon wafers are widely used in Photovoltaic (PV) industry as a base material for the solar cells. The existing silicon ingot slicing methods typically provide minimum wafer thickness of 300–350 μm and a surface finish of 3–5 μm R_a while incurring considerable kerf loss of 35–40%. Consequently, efficient dicing methods need to be developed, and in the quest for developing new processes for silicon ingot slicing, the wire-EDM (electric discharge machining) is emerging as a potential process. Slicing of a 3′′ square silicon ingot into wafers of 500 μm in thickness has been performed to study the process capability. This article analyzes the effect of processing parameters on the cutting process. The objective of the experimental study is improvement in slicing speed, minimization of kerf loss and surface roughness. A central composite design-based response surface methodology (RSM) has been used to study the slicing of polycrystalline silicon ingot via wire-EDM. A zinc-coated brass wire, 100 μm in diameter, has been used as an electrode in the slicing experiments. It has been observed that the optimal selection of the process parameters results in an increase of 40–50% in the slicing rate along with a 20% reduction in the kerf loss as compared to the conventional methods. The machined surfaces on the sliced wafer were free of micro-cracks and wire material contamination, thereby making it useful for electronic applications.     

Some studies into wire electro-discharge machining of alumina particulate-reinforced aluminum matrix composites

Non-traditional process like wire electro-discharge machining is found to show a promise for machining metal matrix composites. However, the machining information for the difficult-to-machine particle-reinforced material is inadequate. This paper is focused on experimental investigation to examine the effect of electrical as well as non-electrical machining parameters on performance in wire electro-discharge machining of metal matrix composites (Al/Al₂O₃p). Taguchi orthogonal array was used to study the effect of combination of reinforcement, current, pulse on-time, off-time, servo reference voltage, maximum feed speed, wire speed, flushing pressure and wire tension on cutting speed, surface finish, and kerf width. Reinforcement percentage, current, and on-time was found to have significant effect on cutting rate, surface finish, and kerf width. The optimum machining parameter combinations were obtained for surface finish, cutting speed, and kerf width separately. Wire breakages were found to pose limitations on the cutting speed in machining of these materials. Wire shifting was found to deteriorate the machined surfaces.     

复合运丝型电火花线切割加工参数分析与研究

提出了一种新型电火花线切割机床,即电极丝作往复直线运动的同时还绕自身轴线高速旋转的复合运丝型线切割机床。介绍了该类机床与其他线切割机床加工的基本工艺指标。通过与高速走丝电火花线切割机床比较实验,分析了脉冲宽度、脉冲间隔、脉冲峰值电流等电参数对加工工艺指标的影响,实验表明这种独特的复合运丝方式在降低表面粗糙度、提高加工精度等方面较传统运丝方式具有较大的优越性,且机床结构较为简单,对于各种工艺参数和电参数具有更加广泛的适用性,具有进一步研究和推广价值。     

Modeling and experimental study on breakdown voltage (BV) in low speed wire electrical discharge machining (LS-WEDM) of Ti-6Al-4V

In this study, the breakdown voltage behavior in low speed wire electrical discharge machining (LS-WEDM) of Ti-6Al-4V (TC4) in the deionized water is investigated. Firstly, the electric field distortion caused by impurity particles including TC4 or brass metal and bubbles is investigated. And then the breakdown voltage model of TC4 machined by LS-WEDM is established and the experimental verification result indicates that the model predicting results conforms to the actual processing and could be well follow experimental results. Second, the influence of breakdown voltage on surface roughness and kerf width has been revealed, it can be found that the kerf width decreases, and the surface roughness increases as breakdown voltage increased. Besides, the voids become bigger and the surface cracks become deeper and wider with the breakdown voltage increased based on analysis of experiment results but for microcracks distributed on spherical or irregular attachments are not influenced by breakdown voltage due to their randomness. Meanwhile, the transparent bubbles of diameter of 400 nm can be observed near the droplet on the machined surface and its major composing element is oxygen. Finally, internal voids can be found in the joint of deterioration layer and the substrate which will make the combination of deterioration layer and the substrate not strong and easy to fall off.     

Parametric optimization for surface roughness, kerf and MRR in wire electrical discharge machining (WEDM) using Taguchi design of experiment

This paper reports the effect and optimization of eight control factors on material removal rate (MRR), surface roughness and kerf in wire electrical discharge machining (WEDM) process for tool steel D2. The experimentation is performed under different cutting conditions of wire feed velocity, dielectric pressure, pulse on-time, pulse off-time, open voltage, wire tension and servo voltage by varying the material thickness. Taguchi’s L18 orthogonal array is employed for experimental design. Analysis of variance (ANOVA) and signal-tonoise (S/N) ratio are used as statistical analyses to identify the significant control factors and to achieve optimum levels respectively. Additionally, linear regression and additive models are developed for surface roughness, kerf and material removal rate (MRR). Results of the confirmatory experiments are found to be in good agreement with those predicted. It has been found that pulse on-time is the most significant factor affecting the surface roughness, kerf and material removal rate.     

Modeling of wire electro-discharge machining of TiC/Fe in situ metal matrix composite using normalized RBFN with enhanced k-means clustering technique

In the present work, wire electro-discharge machinability of 5 vol% TiC/Fe in situ metal matrix composite (MMC) has been studied. Four input process parameters such as pulse on-time, pulse off-time, wire feed-rate, and average gap voltage have been considered, while cutting speed and kerf width have been considered as the measure of performance of the process. The presence of nonconductive TiC particles and formation of Fe₂O₃ during machining make the process very much unstable and stochastic. Thus, modeling the process either by an analytical or numerical method becomes extremely difficult. In the present study, modeling of wire electro-discharge machining process by normalized radial basis function network (NRBFN) with enhanced k-means clustering technique has been done. In order to measure the effectiveness of this approach, the process has also been modeled by NRBFN with traditional k-means technique, and a comparison has been made between the two models. It is seen that both the models can predict the cutting speed and kerf width successfully, but NRBFN with enhanced k-means clustering technique yields better results than NRBFN with traditional k-means technique. Both the models have been used to carry out the parametric study and, finally, have been compared with the experimental results.     

Optimization of wire electrical discharge machining (WEDM) process parameters using Taguchi method

Wire electrical discharge machining (WEDM) is extensively used in machining of conductive materials when precision is of prime importance. Rough cutting operation in WEDM is treated as a challenging one because improvement of more than one machining performance measures viz. metal removal rate (MRR), surface finish (SF) and cutting width (kerf) are sought to obtain a precision work. Using Taguchi’s parameter design, significant machining parameters affecting the performance measures are identified as discharge current, pulse duration, pulse frequency, wire speed, wire tension, and dielectric flow. It has been observed that a combination of factors for optimization of each performance measure is different. In this study, the relationship between control factors and responses like MRR, SF and kerf are established by means of nonlinear regression analysis, resulting in a valid mathematical model. Finally, genetic algorithm, a popular evolutionary approach, is employed to optimize the wire electrical discharge machining process with multiple objectives. The study demonstrates that the WEDM process parameters can be adjusted to achieve better metal removal rate, surface finish and cutting width simultaneously.     

Experimental investigation and prediction of optimum process parameters of micro-wire-cut EDM of 2205 DSS

Micro-wire-cut electrode discharge machining (EDM) is an emerging manufacturing process in the field of micro-manufacturing to fabricate the complex profiles of micro-components. It is a complex process involving various process parameters such as pulse on time, pulse off time, wire speed, wire tension and current. In addition to micro-fabrication, this process can also be extended in the field of tool design and developments such as dies, moulds, precision manufacturing, contour cutting, etc., where complex shapes need to be generated with high-grade dimensional accuracy and surface finish. In this research work, an attempt is made to investigate the effect of process parameters on the output variables such as material removal rate (MRR), surface finish and the cutting width (kerf) of wire-cut EDM for duplex stainless steel (DSS). Scanning electron microscopy (SEM) has been used to capture the images of the kerf width, and the measurements are taken with the help of the welding expert system and software. An optimization technique (Taguchi method) has been employed to identify the optimum parameters of the micro-wire-cut EDM process for cutting 2205 grade duplex stainless steel. The effect of each control parameter on the performance measure is studied individually using the plots of signal to noise ratio.     

Effect of process parameters on the cutting quality in lasox cutting of mild steel

Samples of mild steel have been cut on a CO₂ laser machine using the principle of laser assisted oxygen cutting (LASOX). The combined effects of input process parameters (cutting speed, gas pressure, laser power and stand off distance) on cut quality (heat affected zone (HAZ) width, kerf width and surface roughness) have been studied. Regression analysis has been used to develop models that describe the effect of the independent process parameters on cut quality. Using the developed model, we attempted to optimize the input parameters that would improve the cut quality (minimization of HAZ width, kerf width and surface roughness), increase the productivity and minimize the total operation cost. We found from the study that the gas pressure and cutting speed had pronounced effect on cut quality. Low gas pressure produces lower HAZ width, lower kerf width and good surface finish whereas increase in speed results in higher HAZ width, lower kerf width and good surface finish.     

Application of Taguchi-grey multi responses optimization on process parameters in electro erosion

Convention Taguchi method deals with only single response optimization problems. Since the electrical discharge machining process involved with many response parameters, Taguchi method alone cannot help to obtain optimal process parameters in such process. In the present work, an endeavor has been made to derive optimal combination of electrical process parameters in electro erosion process using grey relational analysis with Taguchi method. This multi response optimization of the electrical discharge machining process has been conducted with AISI 202 stainless steel with different tool electrodes such as copper, brass and tungsten carbide. Gap voltage, discharge current and duty factor have been used as electrical excitation parameters with different process levels. Taguchi L₂₇ orthogonal table has been assigned for conducting experiments with the consideration of interactions among the input electrical process parameters. Material removal rate, electrode wear rate and surface roughness have been selected as response parameters. From the experimental results, it has been found that the electrical conductivity of the tool electrode has the most influencing nature on the machining characteristics in EDM process. The optimal combination of the input process parameters has been obtained using Taguchi-grey relational analysis.     

Studies on Recharging of Abrasives in Abrasive Water Jet Machining

The objective of this work is to find the effect of the recharging of local garnet abrasives (origin: southern India) while cutting aluminium using abrasive water jet machining. The influence of the specially formulated optimised abrasive test sample, pressure, traverse rate, and abrasive flowrate, on the American Foundrymen’s Society fineness number, depth of cut, top and bottom kerf width, kerf taper, and surface roughness are studied. The performance of the test sample has been compared with that of commercial grade abrasive with mesh size 80. Additionally, recharging studies are carried out after screening out particles of less than 90 μm. These tests help to determine the optimum recharging required.     

Performance Evaluation of a Hard Composite Solid Lubricant Coating When Dry Machining of High-carbon Steel

A novel hard composite solid lubricant coating combining TiN and MoS_x has been developed using pulsed DC closed-field unbalanced magnetron sputtering (CFUBMS). The tribological and mechanical properties together with their interdependencies with the coating microstructures have been assessed and reported elsewhere. This article evaluates the machining performance and correlates the underlying tribological aspects of different TiN-MoS_x coating architectures (deposited at titanium (Ti) cathode currents of 1, 3.5, and 5 A) when dry turning AISI 1080 high-carbon steel. A comparative performance study clearly established the supremacy of the composite coating (deposited at 3.5 A Ti cathode current with ～12 wt% of MoS_x) with a hard TiN underlayer over monolayer TiN, MoS_x, and other related coating architectures in terms of cutting force, tool wear, and workpiece surface roughness. The superlubricity behavior of the said composite coated tool resulted in a reduction of cutting force (by up to ～45% compared to the uncoated tool) and exhibited a tool life of 8 min, which was eight times and more than two times longer than that of the uncoated and conventional hard TiN coated counterparts, respectively. The workpiece surface roughness, R_a, also decreased by 13 to 21% when machined with the TiN-MoS_x coated tool in comparison to the uncoated cemented carbide.     

绿色加工中刀具磨损对表面粗糙度影响的研究

在切削镍基高温合金材料过程中,由于不稳定因素造成已加工表面粗糙度很难控制,尤其是刀具磨损直接影响着表面粗糙度。通过对冷风油雾、冷风和常温油雾等不同冷却切削条件下刀具磨损和工件表面粗糙度微观形貌的实验,研究了高速切削镍基高温合金材料时,在不同冷却切削条件下刀具磨损对工件表面粗糙度的影响,揭示了用冷风高速切削提高表面加工质量的规律。     

Application of Taguchi,ANFIS and grey relational analysis for studying,modeling and optimization of wire EDM process while using gaseous media

In the dry wire electrical discharge machining (WEDM) process, the liquid dielectric is replaced with gaseous medium to enhance the machining environment safety. Also, this modification improves the surface quality of machined specimen but decreases the material removal rate of the process. In the present work, experimental study of dry WEDM process has been performed while machining of Al/SiC metal matrix composite. At first, a series of exploratory experiments has been conducted to identify appropriate gas and wire material based on their cutting velocity. After selection of the best gas and best wire, they were used for later stage of experiments. At the next stage, experiment were designed and conducted based on L₂₇ Taguchi's orthogonal array to study the effect of pulse on time, pulse off time, gap voltage, discharge current, wire tension and wire feed on cutting velocity (CV) and surface roughness (SR). Analysis of variances (ANOVA) has been performed to identify significant factors. In order to correlate relationship between process inputs and responses, adaptive neuro-fuzzy inference system has been utilized. At the end, a grey relational analysis has been used to maximize CV and minimize SR simultaneously. Results indicated that oxygen gas and brass wire guarantee superior cutting velocity. Also according to ANOVA, pulse on time and current were found to have significant effect on CV and SR.     

The skin-effect in ferromagnetic electrodes for wire-EDM

In wire electrical discharge machining (wire-EDM) material is removed by the thermal energy of an electric spark that has been initiated between two electrodes (the wire and the workpiece), submerged in demineralised water. The use of high frequency current pulses for sparking leads to excellent machining performance, in terms of the work piece roughness, the material integrity of the cut and the material removal rate. To reach the highest frequencies, the wire-EDM generator mostly consists of a voltage source with an as low as possible internal inductance. The working current delivered to the spark and, hence, the material removal rate of the process depends on the total impedance of the electrical circuit. In this article the importance of the wire’s impedance will be shown. Due to the skin-effect, this impedance depends on the frequency of the current signal, especially for ferromagnetic wires, such as steel wire. Coatings will prove to be primordial to prevent the machining speed from dropping significantly.     

The Effect of Cutting Parameters on Workpiece Surface Roughness in Wire EDM

In this study, the variation of workpiece surface roughness with varying pulse duration, open circuit voltage, wire speed and dielectric fluid pressure was experimentally investigated in Wire Electrical Discharge Machining (WEDM). Brass wire with 0.25 mm diameter and SAE 4140 steel with 10 mm thickness were used as tool and workpiece materials in the experiments, respectively. It is found experimentally that the increasing pulse duration, open circuit voltage and wire speed, increase the surface roughness whereas the increasing dielectric fluid pressure decreases the surface roughness. The variation of workpiece surface roughness with machining parameters is modelled by using a power function. The level of importance of the machining parameters on the workpiece surface roughness is determined by using analysis of variance (ANOVA).     

Application of Taguchi design for quality characterization of abrasive water jet machining of TRIP sheet steels

In the present paper, the influence of sheet thickness, nozzle diameter, standoff distance, and traverse speed during abrasive water jet machining (AWJM) of transformation-induced plasticity (TRIP) sheet steels on surface quality characteristics (kerf geometry and surface roughness) was investigated. The experiments were designed using Taguchi methodology and carried out by AWJ Machining TRIP 700 CR-FH and TRIP 800 HR-FH steel sheets. As response variables, mean kerf width and average surface roughness were selected. The experimental results were analyzed using analysis of means and analysis of variance methods in order to correlate the AWJM process parameters the response variables. In addition, regression models were obtained using the experimental results and validated with six independent experiments. The reported results indicate that the proposed methodology can satisfactorily analyze the surface roughness and the mean kerf in AWJM; moreover, it can be considered as valuable tools for process planning in workshop.     

A new approach to surface roughness and roundness improvement in wire electrical discharge turning based on statistical analyses

In this paper, the effects and the optimization of machining parameters on surface roughness and roundness in the turning wire electrical discharge machining (TWEDM) process are investigated. In the TWEDM process, a new machining parameter, such as rotational speed, is introduced, which changes the normal machining conditions in conventional wire electrical discharge machining (WEDM). By the Taguchi method, a complete realization of the process parameters and their effects were achieved. The Taguchi method has not been used in TWEDM by other researchers. The surface roughness and roundness were measured to verify the process. In addition, the open-circuit voltage, pulse-off time, open arc voltage, and the inter-electrode gap size, which are replaced by power, time-off, voltage, and servo, respectively, and also wire tension, wire speed, and rotational speed were chosen for evaluation by the Taguchi method. An L₁₈ (2¹?×?3⁷) Taguchi standard orthogonal array was chosen for the design of experiments. The level of importance of the machining parameters on the surface roughness and roundness was determined by using analysis of variance (ANOVA). The optimum machining parameters combination was obtained by using the analysis of signal-to-noise (S/N) ratios. The variation of surface roughness and roundness with machining parameters was mathematically modeled by using the regression analysis method. Finally, experimentation was carried out to identify the effectiveness of the proposed method. The presented model is also verified by a set of verification tests.