Die-sinking Electrical Discharge Machining Research Articles

Limits of Die-Sinking EDM for micro Structuring in W300 Steel with pure Copper Electrodes

Electrical discharge machining (EDM) is capable of almost force-free 2D and 3D machining of any kind of conductive material. The micro die-sinking EDM process described in this paper uses electrodes with features in the micrometer scale as a working tool. The ability to machine micro features is desirable for many applications, which range from miniaturization to functionalization of large surfaces. To achieve the desired workpiecès final shape, the working gap and the tool wear behavior must be known and minimized or compensated if possible. For an overall understanding, the interaction between process parameters, such as pulse and pause duration, as well as discharge current with resulting gap sizes, wear formation and work piece shape must be displayed. Besides the optimization of the micro-EDM process itself, the entire process chain must be discussed, including the shaping of the electrodes. This paper provides knowledge on micro structuring copper electrodes using wire-EDM. It also includes information about their subsequent use in micro die-sinking EDM when machining large areas with high aspect ratio micro structures in W300 steel of Böhler Edelstahl. On electrodes, micro ribs with heights of 350 µm, widths of 70 µm and pitch distances of 320 µm could be reached. For micro die-sinking, a relative frontal length wear as low as 19% was determined. The limits of minimum structure sizes in W300 have been investigated, and rib widths down to 31 µm, as well as pillar edge lengths down to 80 µm, have been achieved. Surface quality and changes of the chemical surface compounds of W300 were analyzed using scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDX). Deposit of copper material from the electrode was identified and a proliferation of carbon was detected on the workpiece.

Investigation on non-invasive process monitoring of Die Sinking EDM using Acoustic Emission signals

Die sinking electrical discharge machining is used extensively to produce very complex geometries on difficult-to-machine materials for aerospace, automotive, mold and die applications. The quality of the component produced mainly depends on the quality and intensity of spark generated between the tool and the workpiece. The present research work focused on using the acoustic emission signals to characterize the spark activity in the EDM process under different machining conditions. Experiments were conducted by varying the machining conditions and using three tool electrode materials namely graphite, copper and copper tungsten. The acoustic emission signal features were extracted from the data collected from different experimental conditions and are related to the various parameters including current, voltage, pulse on-time, surface roughness parameters (Ra and Rq) of the workpiece and material removal rate (MRR). The effect of tool material on the AE phenomenon was also investigated. The process conditions were found to have to have a good correlation with the acoustic emission signals features. Multiple linear regression models were built to predict the surface roughness (Ra) of the workpiece and MRR using only the current and pulse on-time as predictor variables. The prediction accuracy of the models improved by the addition of AE signal features to the predictor variable set. The results obtained indicate a suitability of employing acoustic emission signals for monitoring the spark activity, MRR and surface finish of the workpiece in the EDM process. Based on this, a reliable monitoring and diagnosis tool for EDM can be developed using the AE sensor and provides an opportunity to implement the industry 4.0 initiatives effectively.

Electrical Discharge Drilling of Al-Sic Composite Using Air Assisted Rotary Tubular Electrode

Hybrid machining process (HMP) is an integration of two or more machining process. HMP is used to machine hard materials that cannot be machined effectively by the individual machining process. This work focus on developing a hybrid process using both liquid and gas as dielectrics to study its effect on tool wears rate (TWR) and material removal rate (MRR). The compressed air passing through a rotary tubular electrode removed and flushed out the debris from the inter-electrodes gap and hence it improves the flushing efficiency and stability of the process. In this study, the selected workpiece material was Al-15% SiCp MMC. Silicon carbide is selected as filler material in MMC. Experiments have been carried out following the Taguchi design of experiments. The influence of various machining parameters on MRR, TWR, and optimization of process parameter has been performed. Under the same machining condition, high MRR and low TWR obtained when hybrid EDM machining was done as compared to conventional EDM machining. Experimental findings suggested that supply of compressed air through rotary tubular electrode in die sinking electrical discharge machining have a positive influence on MRR and TWR.

Modelling and Optimization of Al–SiC MMC through EDM Process Using Copper and Brass Electrodes

Extensive investigation done on machinability of aluminium/10% silicon carbide metal matrix composite (Al/SiC MMC) with copper and brass electrodes in die-sinking electrical discharge machining (EDM) is reported in the present study. Experiments are performed as per the Box-Behnken design of RSM to study the two performance characteristics i.e. electrode wear ratio (EWR) and material removal rate (MRR) with the five input machining parameters like, low voltage current, high voltage current, pulse off time, pulse on time and flushing pressure. Quadratic regression models are developed for the individual responses and multi-objective particle swarm optimisation (MOPSO) algorithm is employed to find the optimal process parameter settings. Finally, a novel MOPSO algorithm has been suggested for simultaneous optimisation of multiple responses which presents valuable information for governing the machining parameters to enhance accuracy of the electrical discharge machined parts and a confirmation test is performed at the optimized parameter setting for copper and brass electrodes respectively to validate the result. The scanning electron microscope (SEM) also used to investigate the surface characteristics of the machined surface.

A Block Divided EDM Process for Diffuser Shaped Film Cooling Holes

Diffuser shaped film cooling holes are more and more used on the hot side blade of advanced aeroengines or gas turbines. The machining of diffuser holes is a key problem for its complicated shapes and Ni base superalloy. Currently die-sinking electrical discharge machining (EDM) is still considered to be an available process for the machining of diffuser holes. However, the tool electrode shape changes after each process due to electrode wear in EDM, therefore traditional die-sinking EDM process can not meet the requirements of shape precision and machining efficiency for film cooling holes. In this study, a novel EDM process named block divided EDM is proposed. In this process, the space of the complex shape of the hole is divided into several blocks. A slender rod electrode with simple cross-section is employed to form the blocks, each of which can be processed by feeding once. When the tip shape of the electrode changes due to electrode wear, it can be repaired efficiently because of the simple electrode shape. In order to analyze the machining error caused by electrode wear under different machining parameters, a geometry simulation model of the block division EDM process is established. In this simulation model, the shapes of electrode and workpiece are represented by three-dimensional matrix. The electrode motion, the spark gap, and the electrode wear ratio are taken into account. Finally, confirmatory experiments are carried out. It is shown that laidback fan-shaped holes, one type of diffuser shaped film cooling holes can be efficiently formed by the proposed process.

Investigation of process parameters optimization in die-sinking and wire cut EDM to improve process performance using taguchi technique

Electrical discharge machining (EDM) is a well-established machining option for manufacturing geometrically complex or hard material parts that are extremely difficult-to-machine by conventional machining processes. The non-contact machining technique has been continuously evolving from a mere tool and dies making process to a micro-scale application machining alternative attracting a significant amount of research interests. This involves optimization of the process parameters by relating these with the performance measures maximizing the MRR, while minimizing the TWR and yielding the desired SR .The monitoring and control of the EDM process will be carried out by the identification and regulation of adverse arcing occurring during the sparking process.Wire electro discharge machining (WEDM) is a modification of electro discharge machining (EDM) which has been widely used for long time for cutting punches and dies, shaped pockets and other machine parts of electrically conducting work materials. Technology of the WEDM process is based on the conventional EDM sparking phenomenon, utilizing the widely accepted non contact technique of material removal with a difference that spark is generated at the wire and work piece gap. Evolution of WEDM made drastic changes in the area of precision machining with highest degree of dimensional accuracy and surface finish. The present objective is to optimize the process parameters to enhance the performance parameters. The orthogonal array of experiments formed on the basis of relevant Taguchi technique will be conducted based on different electrode materials and work piece materials. The objective of these experiments to give relation between process and performance parameters for different machinability conditions and to improve the efficiency of the process.

Optimization of Electrical Discharge Turning Process using Taguchi-Grey Relational Approach

Electrical discharge turning (EDT) is a unique form of electrical discharge machining (EDM) process, which is being especially developed to generate cylindrical forms and helical profiles on difficult to machine materials at both macro and micro levels. Generally, wire-cut electrical discharge machining is used for turning because it is not concerned with electrode tooling cost. The process variant die-sinking electrical discharge machining can also be effectively used to generate free-form cylindrical geometries on hard to cut materials. In EDT process a precise spindle is incorporated with conventional die-sinking EDM machine to rotate the workpiece. Axially symmetric parts can be manufactured by feeding the shaped conductive strip of copper into the rotating workpiece. Thus, a mirror image of the tool is formed on the circumference of the workpiece. In this way, cylindrical workpiece can be made with small tools. This study presents an experimental investigation of electrical discharge turning of titanium Ti-6Al-4V alloy. The objective was to investigate the influence of machining parameters including peak current, pulse-on time, gap voltage, spindle speed and flushing pressure on performance characteristics at reverse polarity. Taguchi-grey relational approach based on multi objective optimization has been used to optimize material removal and surface roughness simultaneously.

Study on the machining of Al–SiC functionally graded metal matrix composite using die-sinking EDM

ABSTRACTFunctionally graded aluminum matrix composites (FGAMCs) are new materials with excellent capabilities for design and development of complex engineering works. In this work, FGAMCs are machined using electrical discharge machining (EDM) with the process input parameters such as pulse current, pulse on time, and zone position in brake disk. Design of experiments is used for the experimental planning with full factorial method. The selected input process parameters are optimized using gray relational analysis to minimize the electrode wear ratio, overcut, power consumption, and surface roughness. The influential studies of input process parameters on the output responses are also conducted. The optimal EDM parameter setting for achieving better output parameters is pulse current at 5 A, pulse on time at 50 µs and 45 mm zone position distance in the brake disk. The pulse current (39.40%) contributed the maximum in minimizing the output responses. Further, the surface morphology is also analyzed on the material to observe the crater formation and the erosion mechanism.

Experimental investigation of the effects of tool initial surface roughness on the electrical discharge machining (EDM) performance

Electrical discharge machining (EDM) has become an essential process in the modernized manufacturing, as it has been applied in diverse applications such as die cavities manufacturing for automotive components, connecting rods, and different intricate shapes. The proper choice of EDM machining conditions is one of the most critical aspects to consider in the die-sinking electrical discharge machining, as they have great influence on machining performance. Among the parameters and conditions that may affect the machining characteristics, the electrode’s initial surface roughness has not been considered in previous researches. In this study for the first time, the effects of the tool initial surface roughness on the EDM performance are investigated. Experiments are conducted on a die-sinking EDM machine with several different tool initial surface roughness values and EDM parameters to find out the effects on the EDMed workpiece surface roughness, tool wear rate (TWR), material removal rate (MRR), and the tool surface roughness after machining. The results show that TWR increases and MRR decreases by increase in tool surface roughness during finish, semi-rough, and rough EDM processes. In addition, workpiece surface roughness after EDM machining slightly depends on initial tool surface roughness, while the tool surface roughness after machining depends greatly on EDM machining parameters.

Study of the EDM performance to produce a stable process and surface modification

In this work, the effect of pulse current and pulse duration in die-sinking electrical discharge machining (EDM) on the machining characteristics of Ti-6Al-4V alloy is studied. The EDM characteristics, including the electrode wear ratio (EWR), the material removal rate (MRR), and the surface roughness (SR), are used to measure the effect of machining. An increase in the intensity of the pulse current from 2.5 to 5 A produces a slow increase in EWR, MRR, and SR. An increase in the intensity of the pulse current from 5 to 7 A produces a rapid increase in EWR, MRR, and SR. Control charts are basic and powerful tools for controlling statistical processes and are widely used to monitor manufacturing processes and ensure good EDM quality. EWR, MRR, and SR are normal distributions, and the regression curves for the data are straight lines. All of the data points vary randomly around the centerline, which follows the Shewhart criteria and shows that the EDM process and product performance are under control and stable over time. After EDM, the surface exhibits an irregular fused structure, with pinholes, micro voids, globule debris, and many damaged surfaces. Oxygen plasma etching and surface modification after EDM reduce these surface defects, so finer and flatter surfaces can be achieved. Moreover, fatigue life can be enhanced.

An integrated study of surface roughness in EDM process using regression analysis and GSO algorithm

The aim of this study is to develop an integrated study of surface roughness (Ra) in the die-sinking electrical discharge machining (EDM) process of Ti-6AL-4V titanium alloy with positive polarity of copper-tungsten (Cu-W) electrode. Regression analysis and glowworm swarm optimization (GSO) algorithm were considered for modelling and optimization process. Pulse on time (A), pulse off time (B), peak current (C) and servo voltage (D) were selected as the machining parameters with various levels. The experiments have been conducted based on the two levels of full factorial design with an added center point design of experiments (DOE). Moreover, mathematical models with linear and 2 factor interaction (2FI) effects of the parameters chosen were developed. The validity test of the fit and the adequacy of the developed mathematical models have been carried out by using analysis of variance (ANOVA) and F-test. The statistical analysis showed that the 2FI model outperformed with the most minimal value of Ra compared to the linear model and experimental result.

A Study of Dimensional Accuracy on Die Sinking Electrical Discharge Machining of Ti-6AL-4V

Objectives: In this work, an investigation of dimensional accuracy (DA) on the die sinking electrical discharge machining (EDM) of Ti-6AL-4V titanium alloy with positive polarity of copper-tungsten (Cu-W) electrode has been carried out. Methods/Analysis: Pulse on time (ON), pulse off time OFF), peak current (IP) and servo voltage (SV) were selected as the cutting parameters. The experiments have been conducted upon the two levels of full factorial design with added four center points Design of Experiments (DOE). A mathematical model is developed to associate the effects of these four cutting parameters with DA of the work piece. Multiple linear regression modelling technique was performed in the mathematical modelling process. Furthermore, Analysis of Variance (ANOVA) technique was performed to determine the significance of the cutting parameters. Findings: Based on the results, ON, IP and SV were found to be the significant cutting parameters contributes to the DA. This finding also indicates the model developed is observed to be in good simultaneous with the experimental results.

Statistical Approach to Optimize the Process Parameters of HAZ of Tool Steel EN X32CrMoV12-28 after Die-Sinking EDM with SF-Cu Electrode

The paper describes the results of the experimental research of the heat affected zone (HAZ) of an eroded surface after die-sinking electrical discharge machining (EDM). The research was carried out on chrome-molybdenum-vanadium alloyed tool steel EN X32CrMoV12-28 (W.-Nr. 1.2365) after die-sinking EDM with a SF-Cu electrode. The aim of the experimental measurements was to contribute to the database of knowledge that characterizes the significant impact of the main technological and process parameters on the eroded surface properties during die-sinking EDM. The quality of the eroded surface was assessed from the viewpoint of surface roughness, microhardness variation, and the total HAZ depth of the thin sub-surface layer adjacent to the eroded surface. On the basis of measurement results, mathematical models were established by statistical methods. These models can be applied for computer simulation and prediction of the resultant quality of the machined surface after die-sinking EDM. The results achieved by simulation were compared with the results of experimental measurements and high correlation indexes between the predicted and real values were achieved. Suggested mathematical models can be also applied for the determination of the optimal combination of significant technological parameters in order to minimize microhardness and total HAZ depth variations of tool steel EN X32CrMoV12-28 after die-sinking EDM with a SF-Cu electrode.

Modeling and optimization of electrical discharge machining process using RSM: A review

In today’s world the manufactured product not only requires high precision and quality, but also should be produced in minimum time. Thus it is required to achieve the desired output by regulating the process parameter as per the requirement. This has been given rise to a situation which requires the knowledge of optimum values of various input parameters to maximize or minimize a particular output. The RSM (Response Surface Methodology) is one of the efficient Method of modeling at such situation. The main focus is optimization aspects of various parameters of the Electrical Discharge Machining (EDM) processes using RSM & hence only such research works are included in this work. Where RSM is used to optimize the EDM process; that were published in last 10 year since 2006. The Die Sinking EDM, WEDM, PMEDM, Micro-Machining, and various hybrid and modified versions of these processes. The review work on such a large scale was not attempted earlier by considering these processes at a time, and hence, this review work may become the ready information at on a place and useful for the subsequent researchers to decide their direction of research.

Review on modelling and optimization of electrical discharge machining process using modern Techniques

In recent years, the industrial product not only requires high precision and quality, but also should be produced in minimum time to sustain in the highly competitive market. Thus, it is required to achieve the desired output by regulating the process parameter as per the requirement. The input parameters plays important role in determining the surface quality and also the Material removal rate. Amongst the various machining processes Electrical Discharge Machining (EDM) is one of the most attractive alternatives for the industry due to its attractive attribute of not non-contact of tool and workpiece that leads to very little or no force exert in the tool and work piece. In the current study the thorough literature review of various modern machining processes is presented. The main focus is kept on the optimization aspects of various parameters of the EDM processes and hence only such research works are included in this work in which the use of advanced optimization techniques was involved. The review period considered is from the year 2006 to 2015. This review study has been classified according to different process as Die Sinking EDM, WEDM, PMEDM, Micro-Machining, and various hybrids and modified versions. The review work on such a large scale was not attempted earlier by considering many processes at a time, and hence, this review work may become the ready information at one place and it may be very useful for the subsequent researchers to decide their direction of research.

Prediction of the heat-affected zone of tool steel EN X37CrMoV5-1 after die-sinking electrical discharge machining

This article describes the results of the experimental research on the heat-affected zone of the subsurface layers of eroded surface on medium-alloyed samples of steel EN X37CrMoV5-1 (W.-Nr. 1.2343) which occurs in die-sinking electrical discharge machining with Cu electrode. It assesses the direct effect and consequences of the heat-affected zone on the final quality of the machined surface. The aim of the experiments was to contribute to the knowledge database defining the influence of the main technological parameters of electrical discharge machining on the microhardness changes and the total depth of the heat-affected zone of the subsurface layers of experimental samples. The results of the experimental measurement were transformed into the mathematical models allowing simulation and prediction of the final quality of the machined surface after die-sinking electrical discharge machining tool steels with Cu electrode. The purpose of the mathematical models is to determine the optimal combination of process parameters and thereby achieve the desired quality of the products produced by this advanced technology.

Turning by electrical discharge machining: A review

Turning by electrical discharge machining is an emerging area of research. Generally, wire-cut electrical discharge machining is used for turning because it is not concerned with electrode tooling cost. The process variant die-sinking electrical discharge machining can also be effectively used to generate free-form cylindrical geometries on difficult-to-cut materials with complex shapes at both macro and micro levels. The machining performance of electric discharge machine is defined and influenced by its process parameters, which significantly affects production rate and the quality of machined component. Thus, it is very important to select machining parameters and their levels cautiously in order to improve the outcome of the process. In this article, the authors have reviewed the research work carried out in the area of electrical discharge turning in the last decade for the improvement of material removal rate, surface integrity and roundness. In this review, various techniques reported by electrical discharge machining researchers on turning have been categorised in different electrical discharge machining variants. The article also discussed the future direction of research work in the same area.

Surface quality analysis of die steels in powder-mixed electrical discharge machining using titan powder in fine machining

Improving the quality of surface molds after electrical discharge machining is still being considered by many researchers. Powder-mixed dielectric in electrical discharge machining showed that it is one of the processing methods with high efficiency. This article reports on the results of surface quality of mold steels after powder-mixed electrical discharge machining using titanium powder in fine machining. The process parameters such as electrode material, workpiece material, electrode polarity, pulse on-time, pulse off-time, current, and titanium powder concentration were considered in the research. These materials are most commonly used with die-sinking electrical discharge machining in the manufacture of molds and has been selected as the subject of research: workpiece materials were SKD61, SKT4, and SKD11 mold steels, and electrode materials were copper and graphite. Taguchi’s method is used to design experiments. The influence of the parameters on surface roughness was evaluated through the average value and ratio ( S/ N). Results showed that the parameters such as electrical current, electrode material, pulse on-time, electrode polarity, and interaction between the electrode materials with concentration powder mostly influence surface roughness and surface roughness at optimal parameters SRopt = 1.73 ± 0.39 µm. Analysis of the surface layer after powder-mixed electrical discharge machining using titanium powder in optimal conditions has shown that the white layer with more uniform thickness and increased hardness (≈861.0 HV), and amount and size of microscopic cracks, is reduced. This significantly leads to the increase in the quality of the surface layer.

Optimal set-up and surface finish characteristics in electrical discharge machining on Ti-5Al-2.5Sn using graphite

In electrical discharge machining (EDM) process which is an advance and non-conventional technique, the selection of machining parameters for achieving high machining performance is an important; however, very problematic task. In the current manuscript it was aimed to ascertain optimal machining set-up of EDM process related with fine surface finish. The die-sinking EDM was carried out using the both polarities (positive and negative) of graphite electrode. The microstructure of the workpiece surface was investigated by scanning electronic microscopy. The negative polarity produces, on average, nearly double surface roughness than that with positive polarity. The surface microstructure is deteriorated as the discharge energy level increases for both polarities.

Comparisons of single pulse discharge crater geometries in EDM and EAM

Electrical discharge machining (EDM) and emerging electro-arc machining (EAM) are machining processes sharing a similar material erosion mechanism. However, the input parameters and the output responses of them exhibit significant differences. To gain a deeper understanding of these differences, a study was performed adopting single pulse discharges and machining parameters covering EDM and EAM. A full factorial experiment including 50 trials with consideration of the polarity, the discharge current, and the pulse duration, was designed and carried out. For more detailed research and for the sake of comparison, the trials were divided into die-sinking EDM, short pulse EAM, normal EAM, and low current EAM. While the crater geometries including the heat affected zone diameter, the crater depth, the white layer thickness, the removal volume, and the removal ratio, were acquired as results and analyzed. The heat affected zone diameter under both polarities grew with increasing the discharge current and longer the pulse duration. The crater geometry of EDM and EAM was similar when positive polarity was adopted. The crater under negative polarity became shallower as the discharge current decreased and as the pulse duration increased: this led to a significant difference between EDM and EAM. Furthermore, the removal volume and the removal ratio exhibited similar trends. The shallow craters of negative polarity with little removal volume were likely to appear in the normal EAM and low current EAM trials. The characteristics of EAM are such that the high discharge current and the long pulse duration together result in a large material removal rate (MRR) while the long pulse duration alone results in a low electrode wear ratio (EWR). However, the removal ratio of EAM is lower than that of EDM.