Sinking Electrical Discharge Machining Research Articles

Design of experiments integrated with neural networks for optimization and predictive modelling of electrode wear of novel Ti-6Al-4V-SiCp composites during die sinking electric discharge machining

Die Sink Electric Discharge Machining is a widely used manufacturing process for shaping hard and electrically conductive materials. This study investigates the effects of various electrode materials such as, Ti-6Al-4V-SiCp, Brass and Copper on the machining performance of AISI 316 l Stainless Steel workpieces using EDM. The methodology involved optimizing parameters such as Electrode Material, Discharge Current, Gap Voltage, Spark Gap, Pulse-on Time, and Pulse-off Time. From the extensive experimantation it was observed that the combination of Ti-6Al-4V-SiCp electrode material, 8Amp Discharge Current, 90 V Gap Voltage, 75 μm Spark Gap, 100 μs Pulse-on Time and 15 μs Pulse-off Time has resulted in lowest electrode eear rate, higher machining time, and low electrode surface roughness ratio. Ti-6Al-4V-SiCp electrodes possess higher hardness and electrical conductivity compared to Brass and Copper Electrodes leading to higher wear resistance against repeated thermal shocks during electric discharge machining operation. Feed Forward Artificial Neural Network is successfully applied to predict the output characteristics of the experimentation with high accuracy of 98.3% (Electrode Wear Rate), 94.6% (Machining Time) and 93.8% (Electrode Surface Roughness Ratio). Further, microstructure analysis concludes that lowest wear is observed in Ti-6Al-4V-SiCp electrodes compared to Brass and Copper electrodes.

Experimentation on HCHCr steel using vegetable oil as dielectric in EDM

With simplicity and accuracy, conductive hard materials may be machined using the non-traditional material removal technique known as electrical discharge machining (EDM). In the present research endeavour, the influence of using vegetable oil (fresh vegetable oil (FVO), Used Vegetable Oil (UVO) and Mixed Vegetable Oil (MVO)) as an eco-friendly dielectric fluid during die sinking EDM of HCHCr steel has been investigated. Effects of several input variables, including current, pulse width, gap voltage, duty cycle, and using copper and copper chromium electrodes have been examined by employing the Taguchi L18 mixed orthogonal array (OA) technique, to assess the response in terms of Material Removal Rate (MRR), Tool Wear Rate (TWR), and Surface Roughness (SR).

Validation of different tungsten carbide-cobalt grades as tool electrode material for sinking EDM

In sinking electrical discharge machining (EDM), tool electrode wear is crucial for an economical production. The tool electrode wear affects the process efficiency and determines the number of required tool electrodes for a specific machining process. Therefore, the relative tool wear, describing the relation of removed material volume between tool and workpiece electrode, needs to be minimised. The tool wear characteristics in sinking EDM depend strongly on EDM processing parameters and the applied electrode materials. Especially in micro-EDM, a significant increase of relative tool wear is representative. Because of its thermophysical properties tungsten carbide-cobalt (WC-Co) is a suitable material for the application as sinking EDM tool electrode. The economical production of WC-Co form electrodes for EDM sinking is enabled by recent advancements in precision milling of hard materials.Due to non-existent research on which composition of WC-Co is most advantageous for the application as sinking EDM tool electrode material, previous investigations have been intensified to describe correlations between material properties, EDM processing parameters and EDM processing results concerning material removal rate and relative tool wear. Therefore, various WC-Co grades with differing grain size and cobalt content were analysed in sinking EDM experimental studies. It was observed that the factor grain size showed an ambiguous effect concerning the process results. An increasing cobalt content led to a reduction of relative tool wear, which can be explained by the microstructure of the cobalt binder phase with its higher electrical conductivity. The WC-Co grades with beneficial EDM processing results have been further investigated in EDM parameter studies with differing tool electrode geometries. The experimental results concerning relative tool wear, with a minimum of 3 % for macro- and 5 % for micro-sized geometries, proved the suitability of specific WC-Co compositions as tool electrode material for sinking EDM.

Size and speed of ejected particles from different cemented carbide grades machined with sinking EDM

The application of cemented carbides is desired in several fields due to their superb mechanical properties. The downside of the large strength and wear resistance occurs upon machining, which, especially for conventional machining, is expensive or even impossible. Hence, Electrical Discharge Machining (EDM) is used since it works independently from the mechanical properties of the workpiece. However, the ED-machining of cemented carbides is also characterised by low productivity and high tool wear when it is compared to the machining of steel. This paper investigates the material removal phenomenon of different cemented carbide grades by means of a high speed video camera. In order to allow observation, the single discharges are conducted in air. A large number of experiments with different energy levels is analysed by an algorithm to identify the particle size, particle speed and the ejection angle. The results can be used to identify the dominant material removal mechanism. This should in the future be used to create a machining technology which is dedicated to the specific cemented carbide grade.

Experimental investigations and multi criteria optimization during machining of A356/WC MMCs using EDM

In the current paper, the authors are intended to manufacture the aluminum based metal matrix composite (MMC) employing the stir casting process. Further, the fabricated composite sample is investigated for machining characteristics during the die sink electrical discharge machining process (EDM). EDM is most commonly employed to satisfy the special needs of industry such as developing deep holes and complex contours from high strength materials such as composites, alloys, smart materials, and functionally graded materials. In the current study A356 and 4%, tungsten carbide (WC) powder are considered as matrix and strengthening materials respectively to fabricate the MMCs. During the machining activity, the input factors like discharge current (Ip), Voltage (Vg), Pulse On-Time (Ton), and flushing pressure (P) are optimized for achieving optimum surface roughness (SR), Tool Wear Rate (TWR) and Material Removal Rate (MRR). To estimate the ideal set of process factors grey regression analysis (GRA) is used. From the results, it was observed that the GRA is found to perform better than the RSM.

Discharge energy based optimisation of sinking EDM of cemented carbides

The Electrical Discharge Machining (EDM) of cemented carbides is anticipated to enhance in order to allow more efficient machining. However, it is important that an optimisation does not deteriorate the surface integrity of the cemented carbide workpiece, since they are particularly sensitive to tensile stresses as they are caused by EDM. In order to allow for a safe optimisation, the surface integrity of every machining step has been examined before the optimisation regarding surface roughness, recast layer, heat affected zone and crack length. The same parameters have been examined for the optimised machining steps and the resulting workpiece. It was found that machining can be shortened without a significant detrimental effect.

White Layer Thickness Variation in Die Sinking EDM

Surfaces that were machined by Electrical Discharge Machining (EDM) inevitably exhibit a thin layer of resolidified material, commonly called “white layer”. It is usually regarded as disadvantage of ED machining as it induces tensile residual stresses to the parent material and therefore facilitates the formation of cracks. It therefore was subject to a number of scientific investigations that often dealt with its (non-)crystalline structure or the stress induction. Some research groups have also focused on the thickness of the white layer. However, the variation of its thickness has not yet been investigated comprehensively and therefore constitutes the focus of this work. Experiments were conducted on a conventional sinking EDM machine. A heat-treatable steel was used as a workpiece material and graphite was used for the tool electrode. The influence of the discharge duration te as well as the discharge current ie on the white layer formation were investigated. Results show that significant thickness variations occur on every ED machined surface and that increasing discharge energy leads to an increase of both, white layer thickness as well as its variation.

Experimental and thermal investigation on die-sinking EDM using FEM and multi-objective optimization using WOA-CS

This article proposes a numerical and experimental analysis of the effect of a die sinking electrical discharge machine (EDM) on a Nimonic C-263 workpiece with a copper-tungsten (Cu-w) electrode tool. Primarily, the finite element method (FEM) is employed to establish a two-dimensional (2-D) axisymmetric thermal model that utilizes several significant characteristics such as Gaussian heat distribution; distribution quantity of heat through the dielectric fluid, workpiece and tool; pulse on time (TON) and flushing efficacy. The model predicts the distribution profile of temperature on the workpiece during the process of die sinking EDM and obtains the material removal rate (MRR) from the temperature isotherm. An experimental analysis is performed to assess the accuracy of the results obtained from the numerical analysis, and the theoretically calculated MRR (T-MRR) is compared with the experimentally obtained MRR (E-MRR) for the effect of input process arguments such as gap voltage (VG), peak current (I), and TON. In addition, a quadratic polynomial regression model is proposed for output responses and the accuracy is checked by means of variance analysis. However, selecting the optimal combination of input process arguments is quite challenging and essential to being able to enhance the performance of the machining process. Thus, a multi-objective optimization using hybrid whale optimization with the cuckoo search algorithm (named as WOA-CS) is also proposed to find an enhanced machining performance with higher MRR values, a lower tool wear rate (TWR), and a lower surface roughness (SR). Finally, validation of these obtained optimal values is carried out with respect to the experimental results in order to prove the significance of the proposed WOA-CS algorithm in terms of relative error.

Tolerance-Based Optimization of Sinking Electrical Discharge Machining for Industrial Seal Slot Manufacture

Abstract Seal plates for turbine vanes significantly reduce gap losses and thus play a major role in increasing the efficiency of turbines. The industrial production of seal slots, which position the seal plates in the turbine vanes, is driven by the need for high productivity in combination with a reliable processing of necessary geometrical and surface integrity features. A machining technology that is able to machine hard-to-cut materials such as nickel-based alloys is electrical discharge machining. Due to its electrothermal working principle, it is able to machine materials independently from their mechanical properties even at high aspect ratios. Achievable removal and wear rates as well as the resulting surface properties strongly depend on the discharge energy. Furthermore, the discharge energy affects the working gap sizes and therefore flushing efficiencies when machining high aspect ratio cavities. This relationship is investigated taking into account various contemporary generator technologies and graphite grades from both published literature and own experimental investigations. Their effect on machining performance focusing on productivity, recast layer thickness, and crack formation is quantified. Based on these data, a novel empirical model for tolerance-based optimization is developed. The model is used to perform an optimization on an existing serial production, and implementation has been proven successful.

Experimental Study During Electrical Discharge Machining of Reinforced Carbon Fiber Plastic Material

Abstract: The proper selection of machining conditions and machining parameter is an important aspect, before going to machine a carbon-fiber composite material by Die sinking electrical discharge machining (EDM). Because these conditions will determine such important characteristics as; Material removal rate (MRR), Electrode wears rate (EWR), and Surface roughness (R). The purpose of this work is to determine the optimal values of machining parameters of electrical discharge machine, while machining carbon-fiber-composite with copper electrode. The work has been based on the affect of four design factors: pulse current(Ip) supplied by power supply system of electrical discharge machine (EDM), pulse-on-time(TON), gap voltage(Vg) and duty cycle () on such characteristic like material removal rate (MRR), electrode wear rate(EWR), and surface roughness(Ra) on work-piece surface. This work has been done by means of the technique of design of experiment (DOE), which provides us to perform the above-mentioned analysis with small number of experiments. In this work, a L9 orthogonal array is used to design the experiment. The adequate selection of machining parameters is very important in manufacturing system, because these parameters determine the surface quality and dimensional accuracy of the manufactured part. The optimal setting of the parameters are determined through experiments planned, conducted and analyzed using the Taguchi method. It is found that material removal rate (MRR) reduces substantially, within the region of experimentation, if the parameters are set at their lowest values, while the parameters set at their highest values increases electrode wear rate (EWR). Keywords: EDM, Material removal rate, Surface roughness, Tool wear rate,

Thermal Modelling and Multi Decision Making Optimization of EDM of Non Conductive SiC-CNT Ceramic Composite Used for Li-ion Battery and Sensor

In this research work the thermal modeling of a nonconductive Silicon carbide Ceramic matrix composite (CMC) machined by Die Sinking Electric Discharge Machining (EDM) has been done. Though SiC is a non-conductive material but the presence of CNT makes it a conductive material which can be machined with EDM. The modeling procedure carried out by considering some realistic approach like Gaussian heat Flux, Specific Discharge Energy, Variable Latent heat etc. For this analysis a 2D continuum has been designed as work domain. By simulating the work domain model by a Finite Element Analysis (FEA) Software (COMSOL), material removal rate (MRR) has been estimated with variable thermal properties. Parametric analysis of effect of Variable Specific heat on MRR by considering different current, Voltage and Pulse-On time has been performed. The effect of different input parameters (peak current and Pulse-on time) on Crater geometry has been done. A new concept of Specific discharge energy has been introduced during modelling to make it a more realistic model which can also be used as electrode support for electrochemical energy devices as Polymer Electrolyte Membrane Fuel Cells on Li-ion battery. Desirability analysis has been done to get an optimize set of input parameters for I= 3A, V=30V, Ton= 75 µs for machining ceramic matrix composite by EDM. The optimized MRR at this setting is 7.25 mm3/min whereas PFE is 87%. The experimental analysis has been also performed to strengthen the thermal and mathematical modelling.

Influence of low-frequency vibration in Die Sinking EDM: a review

Electric discharge machining (EDM) is a thermal-based machining process where material removal in the form of melting and vaporization occurs due to repeated electrical sparks between electrode and workpiece. EDM process finds wide applications in the manufacturing, automobile, aerospace, and biomedical industries due to its remarkable feature of producing complex geometrical shapes like molds, tools, and dies. Irrespective of materials hardness. In this review, the paper author has given details about a new advancement made in the EDM process, which is low-frequency vibration-assisted Die Sinking EDM. There is also a brief introduction of vibration setups that can be used to generate low-frequency vibration. There is also some discussion about various optimization techniques (e.g., TOPSIS, MOORA, GRA) used to optimize the process parameters that are current, frequency, pulse on time, and pulse off time to get better response parameters ( MRR, TWR, and SR). Besides, there is extensive discussion about the effect of current, pulse on time, pulse off time and frequency on MRR, SR, and TWR. In the end, some discussion on the effect of low-frequency vibration on surface topography is also discussed.

Electrical discharge surface texturing for enhanced pool boiling heat transfer

This research pertains to pool boiling heat transfer characteristics of Aluminum 6061 alloy surfaces that were textured using sink electrical discharge machining (EDM). Prior related work elsewhere utilized EDM as an essential means to roughen a surface or fabricate geometric features such as microchannels and micropillars to investigate boiling. As opposed to this, the present work systematically examined the effect of EDM process parameters viz., the discharge current and the discharge duration to enhance/benchmark boiling performance in the natural convection and nucleate boiling regimes, and comprehend underlying mechanisms. A process-related factor that limits boiling was found to be the growth of a superficial layer on the machined surface, the formation of which is facilitated by the hydrocarbon dielectric fluid used in EDM. This notwithstanding, the highest heat transfer coefficient obtained in this work was roughly five times as that of a reference polished surface. The Data Dependent Systems methodology was adopted to mathematically extract characteristic crater geometry from EDM-textured surface profiles, which highlighted the significance of parameters that are physically relevant such as the crater diameter and the crater volume in correlating boiling performance.

Experimental investigation for sustainable electric discharge machining with Pongamia and Jatropha as dielectric medium

ABSTRACT This research work is a feasibility analysis for the newly developed dielectric based on non-edible vegetable oil, Pongamia (Pongamia pinnata) and Jatropha (Jatropha curcas) for electrical discharge machining (EDM). The traditional EDM uses kerosene as a dielectric with poor safety and unfriendly environmental consequences. In addition to eliminating the risks from kerosene to operator and atmosphere, bio-dielectric can also enhance the machining performance of traditional sinking EDM. As input parameters peak current, gap voltage, and pulse on time were selected and one variable at a time (OVAT) strategy was used to design experimental plans to investigate the application of the newly proposed bio-dielectric. In addition, the mechanism of material removal with Pongamia and Jatropha bio-dielectric is also discussed in detail. The results obtained have shown that the performance of the proposed Pongamia and Jatropha is better than commercially available kerosene oil for MRR, lower EWR and SR, and machined specimens with better surface integrity. It is proposed that dielectric based on Pongamia and Jatropha oil may be used as a hydrocarbon-based dielectric alternative to improve the sustainability of the EDM process.

Investigating the influence of electrical discharge machining process parameter on fatigue strength during machining of titanium grade-2

High strength, excellent corrosion resistance, and low density are the main properties that make titanium attractive for a variety of applications such as the production of airframes, engine components, steam turbine blades, superconductors, missiles, etc. Machining of titanium alloy by conventional machines causes the problems such as chipping and premature tool failure, deflections of the work-piece, increases the temperature at the tool-work piece interface, etc. Hence under such circumstances, nonconventional Die sink Electrical Discharge Machining (EDM) process can be alternative to overcome such problems. The primary aim of this paper is to investigate the effects of process parameters (factors) on material removal rate (MRR) in the EDM process. The process parameters considered for this investigation are current (C), voltage (V), pulse on time (Ton), and pulse off time (Toff) for EDM machining of titanium (grade-2) alloy with copper as an electrode material. The experiments were designed with the Taguchi method, orthogonal array L9. The maximum MRR obtained was 0.073 mm3/min with the voltage of 40 V, current of 8A, pulse on at 60 µs, and pulse off at 9 µs respectively. While the secondary aim of this research is to investigate the effect of process parameters on fatigue strength of titanium (grade-2) alloy. During fatigue test it was observed, fatigue strength decreases with an increase in current and pulse on time.

Evaluating Influences of Input Parameters on Surface Roughness in Sinking EDM Cylindrical Shaped Parts

The input parameters in the process of sinking Electrical Discharge Machining (EDM) are the essential enabling factors that need to be determined. In the present work, the influences of the EDM input parameters containing pulse on time (Ton), pulse off time (Toff), discharge current (IP), Server voltage (SV), work-piece diameter (dw) on the surface roughness (SR) in sinking EDM cylindrical shaped part of 9CrSi material were investigated. Taguchi technique and analysis of variance (ANOVA) have been used to identify the weight of EDM factors on SR. The results show that the impact level of Ton, Toff, IP, SP, and dware 65.55%, 8.66%, 19.17%, 3.14%, and 0.76%, respectively. By analyzing the experimental results, optimum input parameters with the Tonof 6 ms, Toffof 30 ms, IP of 9A, SP of 3V, and dwof 10mm have been determined, that allow getting the best surface roughness.

Micro Electrical Discharge Machining of Micro-Hole

Advancements in micro-fabrication are characterized by a progressive miniaturization leading towards higher integration. The fabrication of particular size micro hole in difficile to machine engineering materials is one of the most challenging tasks in manufacturing industry. Since micro holes are prepared in the end product therefore the rejection of product due to poor hole quality is not acceptable in modern manufacturing industries. Micro electrical discharge machining has become one of the most promising methods for creating micro features or micro components of any electrical conducting engineering materials in spite of its hardness. The material extraction mechanism in micro electrical discharge machining is due to plasma creation, heat deportation, superheating of both the electrodes and expulsion of material is in the form of debris particles by dielectric fluid during pulse-off time. The micro feature such as micro hole created by micro electrical discharge machining process is useful in industries ranging from automobile to biomedical. In order to improve process efficiency researchers across the globe worked on micro electrical discharge machining Setup development, micro electrical discharge machining of different materials and shapes in general and hole making in particular, and also analyzes different factor that affect process performance. Present paper summarizes research work carried out related to experimentation, modeling and optimization of sinking and drilling micro electrical discharge machining of different materials.

The Effect of Discharge Current and Pulse-On Time on Biocompatible Zr-based BMG Sinking-EDM

Abstract The machinability information of Zr-based bulk metallic glasses (BMGs) are recently limited but essential to provide technological recommendation for the fabrication of the medical devices due to the material’s metastable nature. This study aims to investigate the material removal rate (MRR) and surface roughness under different current and pulse-on time of newly developed Ni- and Cu-free Zr-based BMG using sinking-electrical discharge machining (EDM). By using weightloss calculation, surface roughness test and scanning electron microscopy (SEM) observation on the workpiece after machining, both MRR and surface roughness were obtained to be increased up to 0.594 mm3/min and 5.50 μm, respectively, when the higher current was applied. On the other hand, the longer pulse-on time shifted the Ra into the higher value but lower the MRR value to only 0.183 mm3/min at 150 μs. Contrary, the surface hardness value was enhanced by both higher current and pulse-on time applied during machining indicating different level of structural change after high-temperature spark exposure on the BMG surface. These phenomena are strongly related to the surface evaporation which characterize the formation of crater and recast layer in various thicknesses and morphologies as well as the crystallization under the different discharge energy and exposure time.

Application of additive manufactured tungsten carbide-cobalt electrodes with interior flushing channels in S-EDM

Application fields of electrical discharge machining (EDM) are limited due to given process conditions. Manufacturing of parts with high aspect ratios and the application of multi-axis machining are limited due to process instabilities caused by removed particles. A promising approach to improve EDM process conditions, especially in sinking EDM (S-EDM), is the utilization of flushing channels in the tool electrode. However, with increasing complexity of the tool electrode geometry and the local integration of these flushing channels, conventional tool electrode manufacturing by cutting is limited. In contrast to that, the machining process selective laser melting (SLM) does not have such limitations. The appropriate integration of flushing channels, even for complex electrode geometries, improves process conditions during EDM in a variety of applications. This leads to a higher material removal rate and reduced tool wear compared to machining without flushing. Additionally, the number of required tool electrodes can be reduced, as SLM enables an efficient integration and miniaturization of all features in a single electrode. Because of its wear resistance and stability, tungsten carbide is an ideal tool electrode material, which is commonly applied in drilling EDM. After identifying suitable process parameters for roughing EDM with additively manufactured tungsten carbide cobalt tool electrodes, different forms of flushing channels were analysed in order to establish a fast process with minimum tool electrode wear. The results concerning material removal rate and the relative tool wear could be improved by applying internal flushing, though the tool wear stayed at a worse level compared to conventional tool electrode materials.

Experimental investigation on the effects of aqueous solution in electric discharge machining

The aqueous solution of organic compound plays a crucial role as a dielectric medium in Die sink electrical discharge machining process. Two-phase of the dielectric medium, deionised water and aqueous solution of deionised water and glycerin, used in EDM. It eliminates hazards problem. The machining efficiency increases with the concentration of an organic compound in the aqueous solution at long pulse and discharges current compared to the deionised water. The working dielectric medium consists of deionised water and an aqueous solution of deionised water and glycerin. A constant gap voltage used to prove a constant spark gap in the dielectric medium. The drawback rough surface and relative high wear rate are considered at high discharge current in a straight polarity working condition. A regression equation and mathematical modelling used to optimise the process parameters in the investigation. This also reveals the dielectric medium with high viscosity has better machining performance that low viscosity medium.