Address for Correspondence 1 Department of Mechanical and Automobile Engineering, ITM University, Sector 23 A Gurgaon ,

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1 Review Article A REVIEW ON EMERGING AREAS OF INTEREST IN ELECTRICAL DISCHARGE MACHINING Bhaskar Chandra 1, Prof. Hari Singh 2, Mr. Jatinder Garg 3 Address for Correspondence 1 Department of Mechanical and Automobile Engineering, ITM University, Sector 23 A Gurgaon , Haryana,India 2 Department of Mechanical Engineering, NIT Kurukshetra, Haryana,India 3 Department of Mechanical Engineering,NIT Kurukshetra, Haryana,India ABSTRACT Electric discharge machining (EDM), sometimes colloquially also referred to as spark machining, spark eroding, burning, die sinking or wire erosion, is a manufacturing process whereby a desired shape is obtained using electrical discharges (sparks). Material is removed from the work piece by a series of rapidly recurring current discharges between two electrodes, separated by a dielectric liquid and subject to an electric voltage. One of the electrodes is called the tool-electrode, or simply the tool or electrode, while the other is called the work piece-electrode, or work piece Electrical discharge machining is a machining method primarily used for hard metals or those that would be very difficult to machine with traditional techniques. EDM typically works with materials that are electrically conductive, although methods for machining insulating ceramics with EDM have also been proposed. EDM can cut intricate contours or cavities in pre-hardened steel without the need for heat treatment to soften and re-harden them. This method can be used with any other metal or metal alloy such as titanium, hastelloy, kovar, and inconel. Also, applications of this process to shape polycrystalline diamond tools have been reported 1. INTRODUCTION Electrical discharge machining (EDM) is a non traditional concept of machining which has been widely used to produce dies and moulds. It is also used for finishing parts for aerospace and automotive industry and surgical components. Anand Pandey and Shankar Singh [1] explained about the principle of EDM, EDM equipment, EDM process parameters and various types of EDM like Die sinking EDM, Wire EDM, Hybrid EDM,etc. Shruti Mehta, Avadhoot Rajurkar and Jignesh [2] described about the research trends in Die sinking EDM of conductive ceramics. They explained that with the doping of ceramics with conductive elements it is possible to machine ceramics on EDM. K.H. Ho, S.T. Newman, S. Rahimifard and R.D. Allen[3-4] have found that Wire electrical discharge (WEDM) machining is a well established non conventional machining process capable of machining and micromachining of intricate parts but it has relatively low machining speed, as compared to other nontraditional machining process such as laser cutting process. So to meet the challenges of present manufacturing world lot of improvement is going on WEDM functioning. Norliana Mohd Abbas, Darius G Solomon and Md. Fuad Bahari[5] found that EDM has brought many improvements in machining process in recent years. The capability of machining intricate parts and hard material has made as one of the most popular machining processes. They have described Wire EDM, Dry machining, ultrasonic vibration EDM, Role of powder additives in EDM and modeling of EDM process with Artificial neural network (ANN) Fig. 1 Electrical discharge machining 2. MICRO EDM The micro-electro discharge machine (EDM) as the ability to manufacture parts, drill Micro holes and making grooves from 5micro m to 1mm in size. Micro-electro discharge machining has the ability to machine conductive material irrespective of their mechanical hardness [7]. It can also process materials such as Silicon and ferrite which have high specific resistance and have the problem of cracking when processed by ordinary EDM process. According to CIRP committee of Physical and Chemical processes, the term micromachining defines the processes that manufacturer products in the range of 1 to 999 µm. Machining of material can be done without applying pressure on the material,

2 including high precision machining on 3-D curved surfaces, inclined surfaces, and very thin sheet materials which are difficult to drill. High aspect ratio machining can be done using the process. In an ordinary perforating process, Micro-EDM can easily perforate a hole to a depth equivalent to ten times the bore diameter. The high precision and high quality machining can be done while keeping the surface roughness between 0.1micro m to 0.8micro m based on different settings of voltage and capacitance. Katz and Tibbles [7] purposed a micro EDM model with numerical simulation and experimental validation. The model has predicted reasonable values for current density, crater area, power dissipation and the rate of channel growth Fig. 2 Micro EDM A micro electro discharge machining (EDM) equipment is developed. It includes granite basement which can decrease distributed capacitance, precise servo mechanism, precise high speed rotary spindle, wire electro-discharge grinding device, a RC-pulse generator used by micro EDM, machining states detecting system and machining process control system. The CNC interpolation for the 3 axes linkage movement can be realized easily on this equipment. Therefore, micro shaft, micro hole, and 3D microstructure can be machined easily by this equipment. Machining experiments show that the micro shaft with the diameter as small as 5µm and the micro hole with minimum size of 25µm could be obtained steadily, and the maximum aspect ratios of micro shaft and micro hole are over 25 and 10 respectively. Micro- EDM[8] is capable of machining not only micro holes and micro-shafts as small as 5µm in diameter but also complex three dimensional cavities. Masuzawa[9-12] et al. also made several successful attempts producing micro parts such as micro- pins, micro- nozzles and microcavities using micro- EDM. It is as an alternative method for producing photo- masks [13] used in the integrated circuit(ic) industry.at last, a complicated 3D microstructure is machined by this equipment and micro-edm technology. In conventional EDM, electrical discharges generated at the gap between the tool (electrode) and workpiece, while both are immersed in a liquid dielectric, remove workpiece material. Micro EDM works on the same principle. Because micro EDM is a noncontact process, there s no machining force to cause deformation of either the electrode or the workpiece. Given that material is removed by electroerosion and not by mechanical contact, micro EDM can be used to machine any electrically conductive material regardless of its hardness and strength. Micro EDM, for example, can easily process material as hard as quenched steel and carbide, as well as some silicon and ferrite materials, which are known for their high specific resistance. In an ordinary drilling process, micro EDM can easily produce a hole to a depth equivalent to five times the bore diameter. When the bore diameter is more than 50 µm, a depth 10 times the hole diameter can be drilled. Commercially available micro EDM systems can generate a 5-µm hole. Industry uses micro EDM to produce parts like super-fine nozzles (such as the fuel injection nozzles for diesel engines), and to make high-precision masks used in microelectronic manufacturing processes. Work done here at the Center for Nontraditional Manufacturing Research may soon expand the primary uses for micro EDM technology from fine-hole machining to micromold making and the production of micro 3-D parts for micro machines.micro machine is the generic term for very small machines built on a millimeter-to-sub millimeter scale. These devices may be robots for working spaces too constricted for people to enter, capsules inserted into the human body for medical treatments, micro motors, micro sensors, or other machines. Trial production of many micro machines has been carried out using large scale integration (LSI) technology, but it s necessary to machine micro 3-D forms to make the use of micro machines

3 practical. As potential applications for micro machines have grown in number, the perceived need for a means of making the delicate parts used in them has increased. In general, because of poor machining control in the Z axis, fabrication techniques such as etching, deposition, lithography, and laser processing aren t suitable for machining 3-D shapes. It s possible to machine a metal micro part with a 3- D shape by employing traditional manufacturing methods like milling, but the size of the machined part will be limited by the mechanical strength of the part and the tools used. The precision of a shape produced by micro EDM is determined by the shape of the electrode, its traveling locus, and the electro-discharge gap. Further, the gap between the electrode and the material to be processed can be held at the submicron level. Under ideal conditions, by minimizing the electrical discharge energy, it s possible to set the roughness of the machined surface at 0.1 µm Rmax. Consequently, micro EDM can produce very accurate shapes with very small burrs much smaller than those produced by drilling and energy-beam processing. These parts do not need aftertreatment processing such as deburring. Maintaining accuracy during the manufacturing process has presented the greatest challenge to micro-machining with EDM. As an electrode wears, its profile changes, and the component being produced no longer conforms to the desired dimension or shape. To compensate for this wear, manufacturers have used many electrodes of different sizes. Unfortunately, preparing electrodes for the generation of complex micro 3-D shapes requires costly, timeconsuming, and difficult design and fabrication procedures. Because material is eroded from the workpiece, as well as from electrodes of simple or complex shape, 3-D micro shapes cannot be machined correctly using electrodes with rounded edges. Therefore, simple electrodes also need correction if they are to generate accurate 3-D micro shapes using micro EDM. If the shape of the electrode tip is unchanged in other words, if the wear affects only the length of a simple electrode EDM machining resembles conventional machining methods (e.g., milling), and 3-D micro shapes can be accurately generated. 3. HYBRID WIRE EDM Hybrid machining process in EDM make use of the combined advantages and to reduce some negative effects the combined process produce better performance as compared to individual process machining. In EDM process the electrical energy is converted to thermal energy, the combined effect of powder suspension and ultrasonic motion of tool or work piece [1] Many Wire EDM users have expressed the need for "faster cutting speeds, higher accuracy and improved quality". Traditionally, Wire EDM cutting speeds cannot exceed 500mm 2 /min, a feature which all EDM manufacturers are striving to improve. With this in mind, Sodick set out to develop a way to dramatically improve wire cutting speed, examining unconventional methods in the process. The introduction of the "Hybrid Wire EDM" reveals an innovative new product that combines the "ultra-high precision machining" of Wire EDM with the "high-speed machining" of waterjet cutting. In order to facilitate the development of this machine a partnership has been made with the world's largest waterjet manufacturer, "Flow International Corporation", whose corporate office is in Seattle, USA. Rough cutting speed (1 st cut) by waterjet is dramatically 20 times faster than wire-cutting. Initial hole cutting and disposal of core are performed ready for automated operation. The combined Hybrid machine can be installed at small sites. This "Hybrid Wire EDM" can be applied to any 3 different requirements, such as waterjet cutting only, wire cutting only or combined machining with waterjet and wire-cutting. Fig.3 The World s First! Wire EDM and Waterjet are combined into a single "Hybrid Wire EDM"

4 Environmentally-safe graphite cutting does not diffuse particles. Rough cutting speed (1st cut) by waterjet is dramatically 20 times faster than wire-cutting. An abrasive waterjet, ie, one which uses abrasives in the water fluid, is most commonly used. The "Hybrid Wire EDM" also uses abrasives. However, the unique feature for the "Hybrid Wire EDM" is its "ultra high speed cutting". Graphite material, which is traditionally cut by Wire EDM, can be cut up to 20 times faster than Wire EDM for the 1st rough cut which is 10,000mm2/min for 50mm thick). The standard material for mold and die is D2(52 HRC) which can be cut at 1,400mm 2 /min (94mm/min for 15mm thick).initial hole cutting and disposal of core for press mold are performed ready for automated operation. The initial hole cutting, which until now was impossible on Wire EDM and used to be carried out on a separate machine, can be performed on the "Hybrid Wire EDM". Furthermore, the core, produced during transfer-press manufacturing, drops naturally. This also helps achieve automated operation. In short, once a hardened steel plate is set on a "Hybrid Wire EDM", all the machining from initial hole cutting, core handling and finishing is performed automatically without operator intervention. Depending on the requirements, either waterjet cutting, wire cutting or combined cutting can be selected.- Ultra-high-speed cutting by waterjet only, even for insulated materials. Fig4 Products of Hybrid EDM Ultra-high-precision and thick material can be cut by a Wire EDM. Ultra-high-speed cutting by waterjet and finished by a Wire EDM method enable various machining for all kinds of purposes. Small Floor Space for a Hybrid Wire EDM- Traditionally, two separate machines used to be required for waterjet cutting and wire cutting which took up valuable floor space. The Hybrid Wire EDM eliminates this problem with just one small footprint. Environmentallyfriendly machine, since graphite cutting does not become air- born. Both waterjet cutting and wire cutting use water fluid in the Hybrid Wire EDM, thus ensuring graphite chips do not become airborne. 4. SURFACE MODIFICATION METHOD BY EDM AND ITS APPLICATION TO CUTTING TOOLS Surface modification method by Electrical Discharge Machining (EDM) to create a hard ceramic layer on the workpiece. When a kind of metallic material that makes hard carbide is used as an electrode of EDM, hard ceramic layer can be deposited in a certain condition in the process of EDM. In this paper, characteristics of the layer and the application of this method to cutting tools are discussed. First, the principle of this surface modification method is shown. Secondly, the characteristics of the layer are studied in detail. Through the discuss of wear characteristics of the electrode and formation characteristics of the layer, it can be found that there are some distinct differences between the traditional EDM technology and this new EDM surface modification method. Thirdly, the microhardness test of the layer at the different distance from the base metal is carried out. It shows that there is a hard area also under the surface of base metal. At last, as an application of EDM surface modification method, cutting test of cutting tools is done, and it confirms that the life of the cutting tool by EDM surface modification is much longer than that of without layer. 5. POWDER MIXED ELECTRIC DIS- CHARGE MACHINING (PMEDM) Fine abrasive powder is mixed into the dielectric fluid. The hybrid material removal process is called powder mixed EDM (PMEDM) where it works steadily at low pulse energy and it significantly affects the performance of EDM process. Powder Mixed Electric Discharge Machining (PMEDM) has different mechanism from conventional EDM, which can improve the surface roughness and surface quality distinctly

5 and to obtain nearly mirror surface effects. It is a useful finish machining method and is researched and applied by many countries. However there is little research on rough machining of PMEDM. Experiments show that PMEDM machining makes discharge breakdown easier, enlarges the discharge gaps and widens discharge passage, and at last forms even distributed and "large and shadow" shaped etched cavities. Because of much loss of discharge energy in the discharge gaps and reduction of ejecting force on the melted material, the machining efficiency gets lower and the surface roughness gets small in PMEDM machining in comparison with conventional EDM machining. This paper performs experimental research on the machining efficiency and surface roughness of PMEDM in rough machining. The machining efficiency of PMEDM can be highly increased by selecting proper discharge parameters (increasing peak current, reducing pulse width) with approximate surface roughness in comparison with conventional EDM machining. Although PMEDM can improve machining efficiency in rough efficiency, but a series of problems like electrode wear, efficiently separation of machined scraps from the powder mixed working fluid, should be solved before PMEDM machining is really applied in rough machining. Experiments result shows that powder mixed EDM machining can obviously improve machining efficiency at the same surface roughness by selecting proper discharging parameters, and can provide reference accordingly for the application of PMEDM machining technology in rough. Yuan Gang Wang, Fu Ling Zhao[14] found that effects of additive powders on the machining mechanism of powder mixed EDM were researched. The whole discharging process was discussed based on theory of plasma and dielectric. Experiments, oscillograms and energy spectrum analysis gotten in experiments were performed in order to examine the changes of discharge between EDM and powder mixed EDM. Dong Guo Wang [15] found that the particles dispersed in gap can increase the discharge stability and reduce discharge energy density in powder mixed EDM, which effectively improve the surface quality of machined workpieces. Concentration and distribution of particles computed by finite element methods in working conditions were simulated and corresponding experiments were done. The activities of particles in the discharge process were analyzed by experiments and theories. The results show particles have group effect in the gap and that the effect closely associates with particles concentration. H. K. Kansal, Sehijpal and Pradeep Kumar [17] described the optimization of EDM process when silicon is suspended into dielectric fluid of EDM. They studied about parameters- powder concentration, peal current, pulse duration, duty cycle and voltage where voltage is kept constant. They found that powder concentration has 84 % impact in these parameters whereas peak current has 8.8 % impact, pulse duration has 4.2 % and duty cycle has 2.95% impact in machining with Taguchi utility concept. 6. DRY ELECTRIC DISCHARGE MACHINING Dry Electric Discharge machining (dry EDM) is a modification of the oil EDM process in which the liquid dielectric is replaced by a gaseous dielectric. High velocity gas flowing through the tool electrode into the inter-electrode gap substitutes the liquid dielectric. The flow of high velocity gas into the gap facilitates removal of debris and prevents excessive heating of the tool and work piece at the discharge spots. Providing rotation or planetary motion to the tool has been found to be essential for maintaining the stability of the dry EDM process. Tubular tools are used and as the tool rotates, high velocity gas is supplied through it into the discharge gap. Gas in the gap plays the role of the dielectric medium required for electric discharge. Also, continuous flow of fresh gas into the gap forces debris particles away from the gap. Tool rotation during machining not only facilitates flushing but also improves the process stability by reducing arcing between the electrodes. Dry EDM is an environment-friendly EDM technique because of the absence of mineral oil-based liquid dielectric. Environmentally harmful oil-based dielectric wastes are not produced in dry EDM. Also, the process does not pose a health hazard since toxic fumes are not generated during machining. Additionally, absence of mineral oil-based dielectrics drastically reduces fire hazards during the process. Ke Yu Shue, Yao Yang Tsai and Yo

6 Ming Chang[18] found that Dry Electrical discharge machining (Dry EDM), using gas as dielectric, has been developed to solve problems against environment. It has both advantages of high material removal ratio (MRR) and low relative electrode wear ratio (REWR). 7. POWER SUPPLY IN EDM Their efficiency and their power factor of conventional independent electrical discharge machining (EDM) pulse power supplies with the current-limiting-resistor circuit is so low that they do not meet the need of advanced EDM technologies. The design of highly efficient EDM pulse power supply based on switching circuit pulse width modulation current closedloop principle has been initiated. It is composed of such three stages as a single-phase active power factor correction preregulator, a fullbridge phase shift resonant converter based on machining current closed-loop control and a pulse generator based on machining sequence control. Therefore, the efficiency of the new system is considerably increased to about 70%, its weight and size is decreased much. Its power factor is a great deal increased to about Experiment results have demonstrated that the highly efficient EDM pulse power supply is capable of low electrode wear, high speed, stable machining. 8. ROLE OF SURFACTANT IN EDM Surfactants are compounds that lower the surface tension of a liquid, allowing easier spreading, and lowering of the interfacial tension between two liquids, or between a liquid and a solid. Surfactants may act as: detergents, wetting agents, emulsifiers, foaming agents, and dispersants. In a process for electrical discharge machining which comprises passing a spark generated by pulsed application of an electrode at a relatively high voltage to a work piece through a spark gap flooded by a dielectric fluid wherein the process generates in said fluid a dispersion of negatively charged particles from metal droplets melted off the work piece and/or electrode wear fragments, the improvement which comprises at least partially coagulating said dispersed particles with an oil-soluble cationic organic surfactant addition to a dielectric fluid composition consisting essentially of a predominant portion of an inert base fluid selected from the group consisting of hydrocarbon, oxygenated hydrocarbon, silicone oils and mixtures thereof. In a process for electrical discharge machining which comprises passing a spark generated by pulsed application of an electrode at a relatively high voltage to a work piece through a spark gap flooded by a dielectric fluid wherein there accumulates as a dispersion in said fluid finely divided, negatively charged particles, the improvement which comprises employing as said dielectric fluid a composition consisting essentially of a predominant portion of an inert base fluid selected from the group consisting of hydrocarbon, oxygenated hydrocarbon, silicone oils and mixtures thereof, said inert base fluid having an initial boiling point of at least 370 F, a flash point of at least 140 F, a kinematic viscosity of 30 to 40 SUS at 100 F and an electrical conductivity below that of dionized water, together with an effective amount of at least 500 ppm sufficient to reduce substantially the negative charge on said dispersed particles of an oil-soluble cationic organic Electrical discharge machining (EDM) is a method for drilling, cutting or shaping electrically conductive stock by means of the controlled removal of material from the surface through melting or vaporization by highfrequency electrical sparks. The spark discharge is produced by controlled pulsing of direct current between the work piece and the tool or electrode. The end of the electrode and the work piece are separated by a narrow spark gap and are flooded by a dielectric fluid. The dielectric fluid in a gap is partially ionized under the pulsed application of a relatively high voltage, thus enabling a spark discharge to pass between the tool and the work piece. Each spark produces enough heat to melt or vaporize a small quantity of the work piece, leaving a tiny pit or crater in the surface of the work. EDM is often used when the work material is of high hardness, high tensile strength or poor mach inability and the product to be formed is of complex or irregular shape or fragile structure. The dielectric fluid serves as a spark conductor and coolant, and as a flushing medium for removal of the small particles of material separated from the work piece. In practice, the dielectric fluid is recycled, being collected from the apparatus, filtered and then returned to the

7 apparatus. Dielectric fluids have generally been selected for their high dielectric strength, i.e., low conductivity. Satisfactory fluids should have controlled dielectric properties so as to provide a sizable charge flowing from the electrode to the work piece, should be of a light color so that the work piece can be observed through the oil, should be able to carry detritus to the filter for filtration, and should be oxidative and thermally stable for long periods of time. It is found that in some instances finely divided material accumulates in the dielectric fluid, thereby causing darkening of the dielectric fluid, which darkening is disadvantageous in EDM operations. The dispersed, finely divided particles accumulating in the fluid appear to originate from two sources, namely, solidified metal droplets melted off the work piece and electrode wear fragments created by the electric arc. The accumulation of dispersed particles appears to be greater with the newer EDM electrodes, particularly silver tungsten and copper-tungsten electrodes. The accumulation of dispersed particles is also aggravated in the smaller EDM machines, whose filtration systems are incapable of removing particles smaller than about 5 microns in size; since particles smaller than 1 micron are often formed in EDM machining. In the absence of adequate filtration, these dispersed particles circulate with the fluid and darken it as their concentration builds up. Accumulation of finely divided particles dispersed in the dielectric fluid is reduced, whereby the color-darkening of the fluid is minimized, so that the EDM process can be carried out more efficiently. Other advantages of the improved process which are attributed to the presence of the oil-soluble cationic surfactant are as follows: a) Improved detergency in the spark zone to prevent electrically conductive deposits from collecting there; b) Faster machining, smoother surface finish, and longer electrode life due to the increased electrical conductivity of the dielectric fluid. 9. PARAMETER OPTIMIZATION OF EDM There are many optimization techniques which are developed and used for getting the optimum values of various parameters of EDM process to get best results for machining of various materials like Taguchi techniques, Response surface methodology, Artificial intelligence(ai), Genetic Algorithm( GA) and Fuzzy Logic Qing Gao and Qin[19] have developed parameter optimization model by Artificial Neural Network ( ANN) and Genetic Algorithm( GA) and reported its effectiveness in improving MRR. Yih Fong Tzeng and Fu chen [20] applied the multiobjective technique by Taguchi and fuzzy based approach to determine the accuracy and efficiency of the parameters while machine. Mohd. Amir, Lajis and A.K.M. Narul [21] explained about the implementation of Taguchi method on EDM process of Tungsten carbide using graphite as electrode and kerosene as dielectric. They studied about the effects of voltage, peak current, pulse duration and interval time on MRR, EWR and SR. They found that EWR decrease with peak current and interval time. But MRR increase with increase in pulse duration and slightly with increase in peak current. Surface roughness increase with voltage but decrease slightly with increase with peak current Mohan Kumar Pradhan and Chandan Kumar Biswas[22] explained the modeling of machining parameters for MRR in EDM using RSM approach. They used AISI D2 tool steel as work piece and copper as electrode in their experimental work. They studied about three parameters- pulse on time, pulse off time and pulse current on MRR of EDM process. They found that MRR tends to increase with increase in peak current for any value of pulse on time. Max. MRR is obtained for high peak current - 30A and high pulse on time-200 microseconds. with increase in Toff, MRR decreases because of undesirable heat loss which does not contribute to MRR. S.S Mahapatra and Amar Patnaik[23] did the optimization of WEDM process parameters for D2 tool steel as work piece material and zinc coated copper wire as electrode using Genetic algorithm. Different control parameters used in experimentsdischarge current, pulse duration, pulse frequency, wire speed, wire tension, dielectric flow rate on MRR and surface finish. Their studies were based upon maximization of MRR and minimization of surface roughness. 10. CONCLUSION It is clear that Electrical Discharge Machining is widely used non conventional machining process

8 for intricate parts and hard materials. The measurement in EDM process is very important so more focus is on surface finish., PMEDM process provides good surface finish and better material removal rate. So lot of work is going on in this direction. The review on emerging trends of interest in EDM on Dry EDM machining, Powder Mixed EDM, Hybrid EDM, Micro EDM, Power Supply in EDM and Optimization of process parameters of EDM is presented. For each and every method introduced and employed in EDM process, the objectives are to improve the material removal rate, surface finish and to develop new techniques for new materials. REFERENCES- 1. Pandey and Shankar; Current research trends in variants in EDM, International Journal of Engineering Science and Technology, Volume 3, Issue 1, 2010,Pages Shruti Mehta,Avadhoot rajurkar and Jignesh chauhan ; Current research trends in variants in EDM, International Journal of Engineering Science and Technology, Volume 3, Issue 1, 2010,Pages K.H. Ho, S.T. Newman, S. Rahimifard; State of the art electrical discharge machining( EDM), Publication: International Journal of Machine Tools and Manufacture, Volume 43, June 2003, Pages K.H. Ho, S.T. Newman, S. Rahimifard, R.D. Allen ; State of the art wire electrical discharge machining( EDM), Publication: International Journal of Machine Tools and Manufacture, Volume 44, April 2004, Pages Norliana Mohd Abbas, Darius G Solomon and Md. Fuad Bahari ; A review on current research trends in electrical discharge machining(edm), Publication: International Journal of Machine Tools and Manufacture, Volume 47, November 2007, Pages Gunawan S Prihandana, Muslim Mahardika, Mohammad Hamdi, Kimiyuki Mitsui ; The Current Methods for Improving Electrical Discharge Machining(EDM), Publication: Recent Patents on Mechanical Engineering, Volume 2, 2009, Pages Z Katz, C. J. Tibbles; Analysis of micro scale EDM process, Publication: International Journal of Advanced Manufacturing Technology, 2005, Pages K.P. Raurkar, Z.Y. Yu; 3D micro- EDM using CAD/CAM, Publication: Ann. CIRP 49(1), 2000, Pages T. Masuzawa ; State of the art of micromachining, Publication: Ann. CIRP 49(2), 2000, Pages T. Masuzawa,M. Fujino,K. Kobayashi ; Wire electrical discharge grinding for micromachining, Publication: Ann. CIRP 34(1), 1985, Pages T. Masuzawa, C.L. Kuo, M. Fujino ; A combined electrical machining process for micro nozzle fabrication, Publication: Ann. CIRP 43(1), 1994, Pages Z.Y. Yu,T. Masuzawa, M. Fujino ; Micro- EDM for three dimensional cavities development for uniform wear method, Publication: Ann. CIRP 47(1), 1998, Pages S.H. Yeo, G.G. Yap; A feasibility study on the micro electro discharge machining State of the art electrical discharge machining for photomask fabrication, Publication: Advanced manufacturing, Volume 18(1), 2001, Pages F.L. Zhao, Z.Z. Lu, H Wang, Z Q Qian, G.G. Yap; Research on effecting mechanism of particles in powder mixed EDM, Publication: Journal of Dalian University of Technology, Volume 45, 2005, Pages Yuan Gang Wang, Fu Ling Zhao, Yu Liu Behaviors of Suspended Powder in Powder Mixed EDM, Publication: Key Engineering Materials, Volume-Advances in Machining & Manufacturing Technology IX (2008), Pages Dong Guo Wang Simulation of Particles Movement in Powder Mixed EDM, Publication: Advanced materials research Volume -Manufacturing Science and Engineering I, 2010, Pages H K Kansal, Sehijpal and Pradeep kumar; Performance parameters optimization (multicharacteristic) of powder mixed electric discharge machining ( PMEDM) through Taguchi approach and utility concept, Publication: International journal of engineering and manufacturer science, Ke Yu Shue, Yao Yang Tsai, Yo Ming Chang An Investigation of Attachment on Electrode Surface in dry edm, Publication: Advanced materials research Volume - Manufacturing Science and Engineering I, 2010, Pages Qing Gao et. Al, Parameter Optimization Model in Electrical Dischage Machining Process, Publication: Journal of Zhejiang University Science Volume -9, 2008, Pages

9 20. Yih Fong and Fu chen chen Multiobjective optimization of high speed EDM process using taguchi fuzzy based approach, Publication: Materials and DesignAdvanced materials research Volume -28, 2007, Pages Mohd. Amir lajis,mohd. Radzi and A.K.M. Narul Amm; Implementation of taguchi method on EDM process of tungsten carbide, Publication: Europeon Journal of scientific research, Volume 26, 2009, Pages Mohan kumar pradhan and Chandan kumar biswas; Modeling of machining parameters for MRR in EDM using RSM, Publication: Applied Mathematical modeling, Volume 33, 2009, Pages S S Mahapatra and Amar patnaik; Optimization of WEDM process parameters using genetic algorithm, Publication: Applied Mathematical modelling, Dec 2006.