Electrical Discharge Machining Characteristics Research Articles

Multi-Response Optimization of Electrical Process Parameters on Machining Characteristics in Electrical Discharge Machining Using Taguchi-Data Envelopment Analysis-Based Ranking Methodology

Since electrical process parameters are determining the machining characteristics of electrical discharge machining (EDM), it is important to find the optimum values of those parameters and contribution of each parameter. As the process involves more than one response parameter, it is needed to implement the multi-response optimization methodology. AISI 202 stainless steel was selected as work piece material, whereas copper, brass, and tungsten carbide were selected as tool materials. The experiments were conducted with different levels of input factors such as gap voltage, discharge current, and duty factor based on L9 orthogonal table. The purpose of this study is to investigate the contribution of electrical process parameters on machining characteristics and optimal combination of those parameters using Taguchi-data envelopment analysis-based ranking method. From the results, it is revealed that electrical parameters have significant role in EDM process and the optimal values have been found using proposed multi-response methodology.

A study on improving machining characteristics of electrical discharge machining with modified transistor pulse generator

The efficacy of pulse generator in electrical discharge machining is characterised by material removal rate and surface roughness. Due to its low frequency operation, RC relaxation pulse generator could produce lower material removal rate and lower surface roughness than transistor pulse train generator. Since transistor pulse generator could produce larger crater volume throughout the process, it could made higher surface roughness with higher material removal rate. By producing smaller crater volume during finishing stage, surface finish can be improved. The main objective of this study is to improve surface finish by enhancing the process mechanism in thermal erosion process. In the present study, a modified form of the transistor pulse generator approach has been developed. The effects of the pulse generators on the machining characteristics has been experimentally evaluated using Taguchi L9 orthogonal table and analysed in the EDM process. Gap voltage, discharge current and duty factor has been chosen as input variables to evaluate the material removal rate. From the results, it is proved that the modified transistor pulse train generator could produce higher surface finish than existing transistor pulse generator with considerable amount.

Electrical Discharge Machining of Ceramic/Carbon Nanostructure Composites

The miniaturization of mechanical components with complex shapes is a great challenge in emerging applications. Silicon nitride (Si3N4) ceramics are excellent candidates for such applications due to their outstanding mechanical, thermal, and tribological properties. However, they are difficult to machine using normal mechanical machining methods. If the material were electrically conductive, electrical discharge machining (EDM) could be applied to produce precise and complex shapes. In this paper, in order to investigate the effects of electrical conductivity on the EDM characteristics, several carbon nanostructure composite materials are fabricated and EDMed using the assisting electrode method proposed by the current authors. The performance of the process is evaluated as a function of the carbon nanostructure content and type. The former is separately selected to be close to the electrical percolation threshold (0.9 vol.% and 5.3 vol.% for carbon nanotube (CNT) and graphene Nano platelet (GNP) composites, respectively), and well above that limit (5.3 vol.% and 20.6 vol.%), where electrical conductivities on the order of 10 and 100 S·m-1 are attained for CNTs and GNPs-based nanocomposites, respectively. In addition, bare Si3N4 specimens are also tested. Material removal rate, electrode wear ratio, and surface roughness of the machined pieces are analyzed for all testing conditions.

Experimental Investigations into EDM Behaviors of Single Crystal Silicon Carbide

The present study aims to investigate the fundamental electrical discharge machining (EDM) characteristics of silicon carbide (SiC) single crystal material. The EDM machining performances of SiC are experimentally studied and compared to that of steel. Die-sinking EDM of SiC by utilizing copper foil electrodes was proposed and investigated. It was found that EDM characteristics of SiC have a big difference from those of steel. The EDM speed of SiC is higher and the tool wear ratio is lower compared to that of steel material, although SiC has a higher thermal conductivity and melting point. Thermal crack caused by the thermal shock of electrical discharges was found as another main factor contributing to the removal of the material in EDM of SiC material. Also it is concluded that the new foil EDM method for slicing SiC ingot has potential for slicing SiC wafers in the future.

Effect of workpiece material on the machine-ability and surface integrity in EDM process

This paper represents results of an experimental, comparative investigation of the effect of different parameters on evaluation of electrical discharge machining characteristics of newly developed powder metallurgy tool steel in forging industry, ASP30 and widely used hot-work tool steel, AISI H13. The studied process characteristics comprise the material removal rate, tool wear ration and texture features of surface layer including arithmetic surface roughness and white layer of the machined workpiece after the EDM process. The experiments carried out under a full factorial procedure and the considered EDM input parameters included pulse on-time and pulse current. Experimental results reveal that overall the material removal rate and tool wear ratio of the EDM process of H13 tool steel is more than that of ASP30 tool steel. Also, the results show that the surface texture features of ASP30 is better than that of H13 after EDM process.

A Novel Method of Electrical Discharge Machining in Gas Gap State Control

According to the characteristics of electrical discharge machining in gas, a reference voltage adjustment module was joined into the traditional reference voltage comparison gap state control system, to constitute a closed-loop gap state control system. The proposed gap state control method is expected to improve machining efficiency and machining accuracy of electrical discharge machining (EDM) in gas and improve the automaticity of electric discharge machine tool in gas. Meanwhile, it also has certain reference value for the traditional electrical discharge machining gap state control.

Influence of discharge energy on machining characteristics in EDM

The machining characteristics of electrical discharge machining (EDM) directly depend on the discharge energy which is transformed into thermal energy in the discharge zone. The generated heat leads to high temperature, resulting in local melting and evaporation of workpiece material. However, the high temperature also impacts various physical and chemical properties of the tool and workpiece. This is why extensive knowledge of development and transformation of electrical energy into heat is of key importance in EDM. Based on the previous investigations, analytical dependence was established between the discharge energy parameters and the heat source characteristics in this paper. In addition, the thermal properties of the discharged energy were experimentally investigated and their influence on material removal rate, gap distance, surface roughness and recast layer was established. The experiments were conducted using copper electrode while varying discharge current and pulse duration. Analysis and experimental research conducted in this paper allow efficient selection of relevant parameters of discharge energy for the selection of most favorable EDM machining conditions.

Determination of optimal parameters with multi response characteristics of EDM by response surface methodology, grey relational analysis and principal component analysis

This paper proposes a new combination of response surface methodology (RSM), grey relational analysis (GRA) and principal component analysis (PCA) modelling and optimisation method are used for the determination of the optimum process parameters that maximises material removal rate without compromising the surface quality in an AISI D2 tool steel. The input parameters of electrical discharge machining (EDM) considered for this analysis are pulse current ( Ip ), pulse duration ( Ton ), duty cycle ( Tau ) and discharge voltage ( V ). The effects of these parameters have been optimised by conducting by optimising multi response analysis. The designed experimental results are used in GRA, and the weights of the responses are determined by PCA. Based on optimisation results, using the RSM the interactive effects of the machining parameters on the responses were evaluated. It is found that the grey relational grade (GRG) was dominantly influenced by Ip and their interactions with the other parameters. This method is simple with easy operatability, the assessment outcome provides a scientific reference to obtain useful information about how to control the modelling parameter to ensure high productivity without compromising the quality of the EDM surfaces. The results have also been verified by running confirmation tests.

Ultrasonic assisted EDM: Effect of the workpiece vibration in the machining characteristics of FW4 Welded Metal

This paper presents the results of experimental studies carried out to conduct a comprehensive investigation on the influence of ultrasonic vibration of workpiece on the characteristics of Electrical Discharge Machining (EDM) process of FW4Welding Metal in comparison with the conventional EDM process. The studied process characteristics included the material removal rate (MRR), tool wear ratio (TWR), and surface roughness (R a and R max) of the workpiece after the EDM and ultrasonic assisted EDM (US-EDM) processes. The experiments performed under the designed full factorial procedure and the considered EDM input parameters included pulse on-time and pulse current. The experimental results show that in short pulse on-times, material removal rate in the USEDM process is approximately quadruple than that of the EDM process. On the contrary, in the long pulse on-times, ultrasonic vibration of workpiece leads to the reduction in the MRR. On the other hand, in short pulse on-times, the TWR in the US-EDM process is lower than that of in the EDM process, and this condition reverses with increase in the pulse on-time. Furthermore, the surface roughness of the workpiece machined by EDM process is slightly lower than that of applied to the US-EDM process.

Machining Characteristics of EDM Using Gas Media

The aim of this study is to construct a diverse process of electrical discharge machining (EDM) in gas media, and then the new developed machining approach was used to investigate the effects of machining parameters on machining characteristics. Firstly, the feasibility of the EDM in gas media was established with consecutive electrical sparks generated within the machining gap. Moreover, the main machining parameters such as peak current, pulse duration, machining polarity, and gas media supply conditions like air compressed pressure were varied to evaluate the effects on machining characteristics of SKD 61 mold steel in the developed EDM process. The surface morphology of machined surface was observed by a scanning electronic microscope (SEM) to determine the influences of EDM discharge energy on surface integrities. From the result shown in experiments, the material removal rate (MRR) increased with peak current, pulse duration, and air pressure. In addition, the electrode wear rate (EWR) went up with peak current at first, and then attained a peak value with extending the pulse duration and the air pressure, but the EWR declined with further increasing of the pulse duration and the air pressure. Furthermore, the integrities of the machined surface revealed dramatically rough features when the peak current was set at high value. While the pulse duration was further extending, the surface integrities of the machined surface exhibited a smoothened trend obtained by EDM in gas media. Consequently, the developed technique of EDM in gas media possesses the potential of promoting machining performance, reducing environment impact, and extending the EDM applications.

Research on Electrical Discharge Machining Characteristics and Mode of Providing Power of Germanium Crystal

Unilateral conductibility and superficial electrochemical properties represented in n-type germanium crystal electrical discharge machining(EDM) are researched in a bid to reveal the special characteristics of this material during EDM process.It is discovered that the n-type germanium crystal EDM cannot be sustained,and this is due to electrolysis emergence on the contact surface of providing power and consequently forming non-conducting insoluble oxide blocking the gap between the contact surfaces.In order to prevent electrolysis from occurring,a method to apply carbon paste coating on the contact surface is designed.On the other hand,for the purpose of removing non-conducting insoluble oxide on the contact surface,the method of electrode servo power providing is designed.Then the two power providing methods are compared.Results show that the former is able to improve the power providing condition of n-type germanium crystal for a certain period of time but can't achieve the long-term stability,while the latter can assure the steady lower inter-electrode resistance and the persistent effect of power providing.Through the wire-cut EDM(WEDM) experiment,special phenomena of semiconductor material in electrical discharge machining are preliminarily revealed,which include inter-electrode current climbing up,thermal stress erosion being dominant in the discharge erosion and polarity effect required to be analyzed in depth.

Analysis of the machining characteristics of EDM as functions of the mobilities of electrons and ions

Electrical discharge machining (EDM) is a process that can be used effectively to machine conductive metals regardless of their hardness. In the EDM process, material removal occurs because of the thermal energy of the plasma channel between the electrode and the workpiece. During EDM, the electrode as well as the workpiece is abraded by the thermal energy. Tool wear adversely affects the machining accuracy and increases tooling costs. Many previous studies have focused on mitigating the problems of tool wear by investigating various EDM parameters. In this study, the tool wear problem was investigated on the basis of the mobilities of electrons and ions in the plasma channel. The material removal volumes of both the electrode and the workpiece were compared as functions of the gap voltage. The material removal difference according to the capacitance was also investigated. The tool wear ratio was calculated under different EDM condition and an EDM conditions for reducing the tool wear ratio was suggested.

ウェットブラスト加工したワイヤ工具電極の表面性状が超硬材料の放電加工特性に及ぼす影響

High-speed cutting techniques in electric discharge machining are expected to contribute to cost cutting and energy reduction in these machining processes. It has been revealed that the surface shape of the wire tool electrode influences the wire electric discharge machining characteristics. It has also been hypothesized that a rough wire has many concentrated electric fields that lead to the shorter electrical discharge delay time. However, there are not enough experimental results to demonstrate the effect of the surface shape of the wire tool electrode on improving the processing speed. It is also expected that a simple and effective processing method will increase and control the roughness of a wire tool electrode. In this study, we proposed the wet blasting method as a new surface roughness treatment technique, and investigated the processing ability of this method under various conditions. Moreover, we examined the electric discharge machining characteristics of cemented carbide using a wire tool electrode roughened by a suitable wet blasting treatment.

Modeling and Optimization of Process Parameters in Micro Wire EDM by Genetic Algorithm

The present work is aimed at optimizing the parameters of micro Wire Electric Discharge Machining (µ-WEDM) process by considering the simultaneous effects of input parameters viz: gap voltage, capacitance and feed rate. Experiments were planned and conducted using DoE techniques. ANOVA was performed to find out the significance of each factor. Regression models were developed for the experimental results of surface roughness and overcut of the micro slots produced on aluminium. Then Genetic Algorithm (GA) was employed to determine the values of optimal process parameters for the desired output value of micro wire electric discharge machining characteristics.

Multi-response optimization of EDM with Al–Cu–Si–TiC P/M composite electrode

The present study investigates the relationship of process parameters in electro-discharge of CK45 steel with novel tool electrode material such as Al–Cu–Si–TiC composite produced using powder metallurgy (P/M) technique. The central composite second-order rotatable design had been utilized to plan the experiments, and response surface methodology (RSM) was employed for developing experimental models. Analysis on machining characteristics of electrical discharge machining (EDM) die sinking was made based on the developed models. In this study, titanium carbide percent (TiC%), peak current, dielectric flushing pressure, and pulse on-time are considered as input process parameters. The process performances such as material removal rate (MRR) and tool wear rate (TWR) were evaluated. Analysis of variance test had also been carried out to check the adequacy of the developed regression models. Al–Cu–Si–TiC P/M electrodes are found to be more sensitive to peak current and pulse on-time than conventional electrodes. The observed optimal process parameter settings based on composite desirability are TiC percent of 18%, peak current of 6 A, flushing pressure of 1.2 MPa, and pulse on-time of 182 μs for achieving maximum MRR and minimum TWR; finally, the results were experimentally verified. A good agreement is observed between the results based on the RSM model and the actual experimental observations. The error between experimental and predicted values at the optimal combination of parameter settings for MRR and TWR lie within 7.2% and 4.74%, respectively.

Study on the characteristics of electrical discharge machining using dielectric with surfactant

This research mainly explores the influence of surfactant on the characteristics of electrical discharge machining (EDM) process on mold steel (SKD61). In this study, particle agglomeration is reduced after surfactant molecules cover the surface of debris and carbon dregs in kerosene solution. Debris is evenly dispersed in dielectric to improve the effects of carbon accumulation and dreg discharge, and reduce the unstable concentrated discharge. The EDM parameters, such as peak current, pulse duration, open voltage and gap voltage are studied in this paper. The experimental results show that after the addition of Span 20 (30 g/L) to dielectric, the conductivity of dielectric is increased. The machining efficiency is thus increased due to a shorter relay time of electrical discharge. When proper working parameters are chosen, the material removal rate is improved by as high as 40–80%. Although the improvement of surface roughness is not obvious, the surface roughness is not deteriorated since the material removal rate is great.

Machining characteristics of magnetic force-assisted EDM

The gap conditions of electrical discharge machining (EDM) would significantly affect the stability of machining progress. Thus, the machining performance would be improved by expelling debris from the machining gap fast and easily. In this investigation, magnetic force was added to a conventional EDM machine to form a novel process of magnetic force-assisted EDM. The beneficial effects of this process were evaluated. The main machining parameters such as peak current and pulse duration were chosen to determine the effects on the machining characteristics in terms of material removal rate (MRR), electrode wear rate (EWR), and surface roughness. The surface integrity was also explored by a scanning electron microscope (SEM) to evaluate the effects of the magnetic force-assisted EDM. As the experimental results suggested that the magnetic force-assisted EDM facilitated the process stability. Moreover, a pertinent EDM process with high efficiency and high quality of machined surface could be accomplished to satisfy modern industrial applications.

E11 導電性セラミックスの放電加工特性に関する基礎的研究(OS-8 放電加工(2))

This study deals with electrical discharge machining (EDM) characteristics of electrically conductive fine ceramics developed recently. Ceramics have been applied in various fields because of their many excellent mechanical, electrical and thermal properties. However, the machining into three dimensional shapes is difficult by conventional mechanical machining methods. In order to make it possible tomachine by EDM, many types of electrically conductive ceramics have been recently introduced into the market. However, EDM characteristics of such new ceramics have not yet made clear sufficiently. In this report, EDM characteristics such as removal rate, electrode wear and surface roughness of TiB_2 used as a metal mold material for lens and parts of electronic device are experimentally discussed. As a result, the electrode wear rate can be much reduced when the polarity of copper electrode is positive and the pulse duration is set to 100μs or more. Also, high speed EDM is possible when the polarity of graphite electrode is negative.

Electrical discharge machining of carbon nanomaterials in air: machining characteristics and the advanced field emission applications

A reliable and precise machining process, electrical discharge machining (EDM), was investigated in depth as a novel method for the engineering of carbon nanomaterials. The machining characteristics of EDM applied to carbon nanomaterials ‘in air’ were systematically examined using scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), energy-dispersive x-ray spectroscopy (EDS), x-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The EDM process turned out to ‘melt’ carbon nanomaterials with the thermal energy generated by electrical discharge, which makes both the materially and geometrically unrestricted machining of nanomaterials possible. Since the EDM process conducted in air requires neither direct contact nor chemical agents, it protects the carbon nanomaterial workpieces against physical damage and unnecessary contamination. From this EDM method, several advanced field emission applications including ‘top-down’ patterning and the creative lateral comb-type triode device were derived, while our previously reported study on emission uniformity enhancement by the EDM method was also referenced. The EDM method has great potential as a clean, effective and practical way to utilize carbon nanomaterials for various uses.

Influence of current impulse on machining characteristics in EDM

Electrical discharge machining (EDM) is a machining process transforming electric energy into thermal energy to remove materials. The current impulse is a very important factor for machining characteristics of EDM. A series of experiments were performed to investigate the influence of current impulse on machining characteristics. The features of current impulse have initial current, current rising slope and impulse pattern. The used patterns of current impulse included rectangular current impulse, trapezoidal current impulse and the 1st order current impulse. The machining characteristics are associated with relative wear ratio (RWR) and material removal rate (MRR). Experimental showed that using trapezoidal current impulse with small initial current or little current rising slope reduced relative wear ratio and material removal rate as well. However, larger relative wear ratio was obtained for workpiece of tungsten carbide when current rising slope was too little. Using the 1st order current impulse with 20 μs current rising time can improve relative wear ratio about 30 % while remain material removal rate the same as rectangular current impulse for tungsten carbide.