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The complex and stochastic nature of the electro-discharge machining (EDM) process has frustrated numerous attempts of physical modeling. In this paper two supervised neural networks, namely back propagation (BP), and radial basis function (RBF) have been used for modeling the process. The networks have three inputs of current (I), voltage (V) and period of pulses (T) as the independent process variables, and two outputs of material removal rate (MRR) and surface roughness (Ra) as performance characteristics. Experimental data, employed for training the networks and capabilities of the models in predicting the machining behavior have been verified. For comparison, quadratic regression model is also applied to estimate the outputs. The outputs obtained from neural and regression models are compared with experimental results, and the amounts of relative errors have been calculated. Based on these verification errors, it is shown that the radial basis function of neural network is superior in this particular case, and has the average errors of 8.11% and 5.73% in predicting MRR and Ra, respectively. Further analysis of machining process under different input conditions has been investigated and comparison results of modeling with theoretical considerations shows a good agreement, which also proves the feasibility and effectiveness of the adopted approach.

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Measuring topography and flatness of nontransparent rough surfaces using a laser interferometer topography measuring (Zygo) machine is impossible. Due to high accuracy and short measuring time, capacitor probe is a good candidate for measuring topography and flatness of a rough surface. Measuring by a capacitor probe is an average area measuring method and it is suitable for measurment of machinment processes such as ion or blast figure correction, computer control polishing (CCP) and magnetorheological finishing (MRF) methods. The idea of a rough surface which directly can be used for corrective figuring is generated by measuring flatness and waviness of it through a capacitive probe. Among the area averaging methods, the surface capacitance method can be used to elaborate the idea of corrective figuring of a rough surface. Measuring flatness of a rough surface whose roughness (Ra) is in the range of out of flatness is another technical property of the presented method.

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Measuring topography and flatness of nontransparent rough surfaces using a laser interferometer topography measuring (Zygo) machine is impossible. Due to high accuracy and short measuring time, capacitor probe is a good candidate for measuring topography and flatness of a rough surface. Measuring by a capacitor probe is an average area measuring method and it is suitable for measurment of machinment processes such as ion or blast figure correction, computer control polishing (CCP) and magnetorheological finishing (MRF) methods. The idea of a rough surface which directly can be used for corrective figuring is generated by measuring flatness and waviness of it through a capacitive probe. Among the area averaging methods, the surface capacitance method can be used to elaborate the idea of corrective figuring of a rough surface. Measuring flatness of a rough surface whose roughness (Ra) is in the range of out of flatness is another technical property of the presented method. Keywords: Surface Metrology, Capacitance Measurement, Figure Correcting, Precision Machining.

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Due to outstanding properties of γ–TiAl intermetallic such as high resistance against fatigue, oxidation, corrosion, creep, dynamic vibration, high working temperature and also its application in aerospace and automotive industry, turbojet engines and blade manufacturing; in this paper, electrical discharge machining (EDM) of γ–TiAl intermetallic by means of three kinds of tool electrodes including copper, graphite and aluminum is investigated, to compare the output characteristics of the machining process such as material removal rate, tool wear ratio, surface roughness and topography and EDS elemental analysis of machined surfaces. The results indicate that major elements in chemical composition of γ–TiAl machined surfaces are including titanium, aluminum, carbon and oxygen. The variation of tool material has not significant effect on formation of different chemical compounds and phases or in other words surface modification of machined surface. While it mainly affects other aspects of output characteristics such as material removal rate, tool wear ratio and surface roughness.

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γ–TiAl intermetallic has outstanding properties such as high resistance against fatigue, oxidation, corrosion, creep, dynamic vibration and high working temperature. These intermetallics are applied in aerospace and automotive industry, turbojet engines and blade manufacturing. In this paper, powder mixed electrical discharge machining (PMEDM) of γ–TiAl intermetallic by means of different kinds of powders including Al, SiC, Gr, Cr and Fe is investigated to compare the output characteristics of the process such as surface roughness, tool wear rate, material removal rate and surface topography with each other. This is an experimental investigation, by means of die sinking EDM machine and a special tank for machining. The results indicate that, aluminum powder as the most appropriate kind of powder in the optimum particle concentration of 2 g/l, improves the surface roughness about 32% comparing with conventional EDM, decreases the tool wear rate about 19%, but decreases the material removal rate about 7.5% and also the Al powder leads to improving the machined surface topography and decreasing the surface defects and micro cracks.

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We present a micro/nano-machining process to introduce nanostructured poly-silicon layer on the gate region of the pH-sensitive field effect transistors. Decoration of the gate of the field effect transistors by nanostructures plays an important role to improve the sensitivity of the pH-sensitive FETs. Electron beam lithography was exploited to realize the poly-Si nanopillars on the gate surface. Comparison between different micro and nanostructures demonstrates the potential of nanopillars to be utilized on the gate of this device rather than micro-conical structures (different size and shapes) and vertically carbon nanotubes. A high sensitivity of 500 mV/pH has been achieved, through the incorporation of silicon based nanopillars.

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In this research the Magnetic Abrasive Finishing capabilities in AISI 4140 steel polishing was studied. Surface roughness was considered as a function of the tool rotational speed, working gap, abrasive material and abrasives particle mesh size. To conduct the tests, a specific magnetic tool was designed to polish the flat steel surfaces by a milling machine. Experiments were arranged based on Taguchi method and using abrasive material consisting of Aluminum Oxide or Silicon Carbide with paraffin oil and Carbonyl Iron powders with different mesh sizes. After surface roughness measurement of samples, the effect of each parameter on the surface quality was inspected by ANOVA method. Results showed that in Magnetic Abrasive Finishing of mentioned steel, the parameters of working gap, tool rotational speed and the abrasive material type are of the most importance as ordered. Finally, a roughness predictor function was introduced by regression method.

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In this study the interaction of material and ultrasonic vibration of workpiece at different pulse on times (Ti) and discharge currents (I) in the electrical discharge machining (EDM) has been studied. The materials of machined samples were AISI H13 tool steel and FW4 weld steel. The results show that ultrasonic vibration of workpiece, independent of workpiece material increase material removal rate (MRR) and reduce tool wear ratio (TWR) and surface roughness. Also the results indicate that the effect of ultrasonic vibration on the material removal rate increase of FW4weld steel is higher than AISI H13 tool steel, and the reduction of tool wear ratio of FW4 weld steel is more than AISI H13 tool steel.

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In this paper an innovative vibration rotary tool was designed and manufactured. Vibration turning tool is a compound of turning rotary tool and ultrasonic assistant turning. In this tool, an ultrasonic wave generator with power equal to 20 KHz transducer that has a rotational motion during the process was used. For tool vibration, a stainless horn with resonance frequency equal to 20618 Hz, were designed and manufactured. Round insert with 10 millimeter diameter were used. One of the most important key points in this setup is that the simultaneous rotation and vibration has to be achieved. For rotational motion a motor power and a rack and pinion were used. Also a structure with ability to mount on turning machine were designed and manufactured. Cutting force and surface roughness for each experiment were measured and compared with data collected from conventional rotary tool on 7075 aluminum material. Results shows that ultrasonic vibration cause decreasing in cutting tools and surface roughness, tremendously.

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One of the fundamental problems of Electrical Discharge Machining (EDM) process is tool electrode wear. In this study, ultra fine grains (UFG) structure of pure copper was used to improve performance and also increase the electrical wear resistance of tool electrode. Equal Channel Angular Pressing (ECAP) was used to reduce the crystal size of pure copper. Samples were processed through ECAP die up to 8 passes, and then used as electrode in EDM process. The effect of electrodes grain size, discharge current, and machining time on the metal removal of the work piece and electrical wear of the electrodes were investigated. In addition, the microstructure, and electrical conductivity of copper tool electrodes were examined. By applying the ECAP on pure copper a fine, approximately 50-200 nm grain size, microstructure was obtained after 8 passes. The results show that for finer crystalline structure of copper electrodes, electrical wear decreases but material removal rate is somehow constant.

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This paper studies the effects of soluble cutting fluid-based CuO Nanofluid on machining force and surface roughness in turning of hardened AISI 4340 tool steel. These influences, Moreover, are compared with the outputs of similar tests through dry and soluble cutting fluid. The obtained results showed 1% volume fraction of CuO Nanoparticles added to soluble oil as cutting fluid was considerably reduced machining force and surface roughness in comparison to soluble cutting oil and dry. The investigations indicated that CuO Nanofluid reduced surface roughness and machining force by 49% and 24% respectively. Moreover, the results illustrated that the lowest surface roughness obtained in cutting speed 250 m/min, feed rate 0.1 mm/rev and cutting nanofluid.

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In this paper, dry electro-discharge machining (Dry EDM), one of the newest machining processes which differs mainly from conventional EDM in using gaseous dielectric along with tool electrode rotation, has been studied. Gap voltage, discharge current, pulse-on-time, pulse-off time, dielectric gas pressure, and electrode rotational speed have been considered as effective input parameters. Response surface methodology (RSM) has been used to optimize the machining performance with respect to material removal rate (MRR). Base on the results and analysis of running experiments, it can be concluded that MRR increases by increasing gap voltage, discharge current, the ratio of pulse-on time over pulse-off time, input gas pressure, and electrode rotational speed. There also exists an optimum amount of pulse-on time determined according to the machining circumstances. Also the material removal rate in dry EDM has been improved compared with that in conventional EDM in identical conditions. Keywords: Dry electro-discharge machining (Dry EDM), Gaseous dielectric, Response surface methodology (RSM) Keywords: Dry electro-discharge machining (Dry EDM), Gaseous dielectric, Response surface methodology (RSM) Keywords: Dry electro-discharge machining (Dry EDM), Gaseous dielectric, Response surface methodology (RSM)

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Hybrid layered manufacturing is one of the key methods among rapid manufacturing techniques in which a layer of molten metal is deposited on the substrate and desired geometry is completed by stacking the layers. Inexpensiveness, high rates of deposition and great applicability are some of the characteristics of hybrid layered manufacturing. Welding and face milling are the two steps of the process. In welding phase, metal is built up by weld lines to cover a given surface and in milling phase weld beads are truncated to achieve a flat and integrated layer. The focus in this article is to optimize two contradictory objectives, namely reduction in machining volume and increase in deposition rate. Thus, the first task is to formulate the bead model considering the metal build-up effect. Then, the situation needed for achieving quasi-flat layers in welding phase is studied and the unified model is extracted. Moreover, GA is used to find optimum values for the proposed model based on heat and process constraints. Finally the model is verified and conclusions are drawn. This article presents a new criterion by defining the heat constraint for the multi-objective function. Results show that for the 0.8 mm wire ER70S6, optimum values are 8.6 m/min for wire speed and 0.6 m/min for torch speed that yield a deposition rate of 4224 mm3/min without violating heat constraint.

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The main problems in machining of thin-walled parts made of high-strength aluminum alloys are distortion and dimensional instability, which lead to an increase in distorted part scraps and production costs. This article attempts to investigate the correlation between machining-induced and quench-induced residual stresses and the distortion of thin-walled parts made of AL7075 alloy. The experiments are carried out in two steps. In the first step, the effects of polymer and uphill quenching methods in comparison with water quenching in the reduction of residual stresses are investigated on an experimental basis. By conducting the machining tests, the effect of residual stress on distortion is investigated. In the second step, several experiments are carried out under different machining conditions. To study the effect of mechanical and thermal loads on the residual stresses and distortion, the machining force and temperature of cutting area are measured. Finally, the correlation between the machining-induced residual stress and distortion is studied by measurement of stress on some parts. The results indicate that both machining and quench-induced residual stresses are effective in distortion of thin walled parts.

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Electrolyte type, due to the nature of its constituent ions, affects the reaction rate, the uniformity of the electric field and formation of the external layer on the workpiece surface in the machining area during the electrochemical machining process, as well as it causes to create different dissolution behaviors of the workpiece. Therefore in this study the effect of sodium chloride, sodium nitrate, potassium chloride and hydrochloric acid electrolytes with different currents on the electrochemical machining characteristics of stainless steel 304, including material removal rate, side gap and surface roughness, has been investigated. The results showed that the formation of passive layer during the machining with sodium nitrate electrolyte reduces the material removal rate and side gap compared with sodium chloride and potassium chloride electrolytes. According to the experimental results the surface roughness in the sodium chloride and potassium chloride electrolytes is decreased by increasing the machining current, but increases in the sodium nitrate electrolyte. Also the material removal rate slight increase and side gap increase at sodium chloride, sodium nitrate and potassium chloride when combined with hydrochloric acid. On the other hand, the surface roughness reduces in the combined sodium chloride and potassium chloride electrolytes, but increases in the combined sodium nitrate electrolyte.

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Widespread use in the machining procedures in producing industrial pieces, optimization of this procedure is one of most subjects that attract researchers interest. Finite element analysis based techniques are available to simulate cutting processes. Success and reliability of numerical models are heavily dependent upon work material flow stress models in function of strain, strain rate and temperatures. One of the most accurate and most useful equations are presented, the fundamental equation Johnson-Cook is. The basic equations for modeling the behavior of each material, is needed to determine the equation coefficients.The model parameters are determined by fitting the data from both quasi-static compression tests at law strain rates and machining tests at high strain rates. After getting result from the equation, its accuracy being checked either in compression tests or in machining tests by simulation with Abaqus software and its results are compared with the results of machining tests. Studies show the correctness of the equation in determining the dynamic behavior of 5083 alloy is established. Therefore, this equation can be used for modeling the behavior of the selected alloy in other shaping processes, and can be used its results.

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This paper experimentally investigated the effects of electrical discharge machining processes parameters on fatigue resistance of 16MnCr5 alloy steel. 16MnCr5 alloy steels have good wear resistance. For this purpose, pulse current and pulse time have been considered as variables in the process. The selected EDM parameters were pulsed current (8, 16 and 32A) and pulse time (25, 100 and 400µs). Tests were conducted in full factorial mode and the R. R. Moore fatigue test machine was used to determine the fatigue life of components. The results show that by increasing the spark current and pulse duration 16MnCr5 alloy steel fatigue life is reduced. Respectively, the greatest resistance to fatigue achieved at current of 8A and pulse time of 25 microseconds and lowest resistance to fatigue achieved at pulse current of 32A and pulse time of 400 microseconds. Resistance to fatigue crack depends on cracks density on the surface of the workpiece and heat-affected zone, where the density of cracks increase resistance to fatigue will be reduced. Also in the specimens that have low resistance to fatigue, fatigue cracks are initiated from multiple points of the cross-section. It seems the reason for this phenomenon is the high surface roughness in the samples. EDM machining with high energy sparks can decrease the fatigue strength of 16MnCr5 by as much as factors of 3-5.

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A hexapod machine tool with a parallel structure has six degrees of freedom. This machine has a high dexterity unlike traditional machine tools. The hexapod can be used in machining free form surfaces. Free form surfaces are widely used in today industries. These surfaces are much encountered in auto, aerospace and mold design industries. Therefore machining of these surfaces has attracted the attention of researchers. In this field much research has been done in five axis machine tools. In this paper machining free form surfaces with hexapod machine tool has been investigated. The main topic of this paper is the feasibility of using hexapod as a machine tool table and machining with it. First, the interpolation of free form surfaces for parallel structure machines is explained. Then NURBS curves and surfaces are described and its formulation in matrix form is explained. Then extracting information of free form surfaces with NURBS formulation is explained. Subsequently, some explanation about preparation of machining is given. Finally two free form surfaces designed in Catia and have been machined with the developed hexapod machine tool.

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Due to the rapid growth of manufacturing industry and increased competition among companies, the need to produce parts with free-form surfaces with lower cost and higher accuracy is felt. Nowadays beside all of the great benefits of 5-axis CNC machines the use of 3-axis CNC machines are more common in industry because of the high capital investment, high operating and maintenance cost, the low dynamic stability and their complex programming in 5-axis machining. Therefore it is preferred using 3-axis machines in industry where it’s possible. Since the inability of machining some complex parts by 3-axis machines, the 3+2-axis machining technology has been proposed. In this paper, a new method has been used to determine the tool appropriate orientation for 3+2-axis machining. In the proposed method, visible and invisible points of the surface and the shortest tool length are calculated for the workpiece and finally performed surface partitioning. The minimum number of tool orientation result from this methods reducing overall machining time and the boundaries between machining partitions to improves the surface quality. A 3+2-axis machining of an impeller perform and evaluate the efficiency and surface accuracy by the use of a coordinate measuring machine.

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One of the most important machining processes in the field of orthopedic surgeries and biomedical engineering is the drilling process. Applying excessive forces on the bone tissue, it can be caused cracking and damage bone tissue during the drilling process. In this paper, it is produced an improved analytical model based on early work done by Bono and Ni, Chandrasekharan, and Lee to predict the thrust force in the bone drilling process. In this model, the cutting action at the drill point is divided into three regions: the primary cutting lips, outer portion of the chisel edge (the secondary cutting edges), and inner portion of the chisel edge (the indentation zone). All three regions have been investigated for the cutting process by the analytical model. In order validating the model, some experiments performed on the fresh bovine bone. Feed rate and rotational speed are adapted as the effective parameter in the drilling process, The statistical model to obtain the mathematical model and provide interaction diagrams of input variables experiments, to response surface methodology and experimental investigation of bone drilling have been offered. Comparing the analytical model and experimental results show good agreement. From both analytical model and experiments, it is can conclude that with decreasing feed rate and increasing rotational speed, thrust force on the bone tissue decreases.