A STATE OF ART IN DEVELOPMENT OF WIRE ELECTRODES FOR HIGH PERFORMANCE WIRE CUT EDM

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1 A STATE OF ART IN DEVELOPMENT OF WIRE ELECTRODES FOR HIGH PERFORMANCE WIRE CUT EDM Anish Kumar 1, a*, Vinod Kumar 2, b, Jatinder Kumar 3,c 1 Department of Mechanical Engineering, M.M.University Mullana-Ambala (Haryana), India 2 Department of Mechanical Engineering, Thapar University, Patiala (Punjab), India 3 Department of Mechanical Engineering, National Institute of Technology, Kurukshetra (Haryana), India a anish_kaushik@rediffmail.com, b vsingla5@yahoo.com, c jatin.tiet@gmail.com ABSTRACT Wire Electrical Discharge Machining (WEDM) is one of the widely recognized and used nontraditional machining processes in the industry today. Advancements in the process mechanism and control have been rapidly taking place in this process. WEDM can machine harder, high strength, corrosive and wear resistant, and difficult to machine newer materials. Additionally, WEDM can machine intricate shapes which cannot be achieved using the traditional machining processes such as turning, milling, and grinding. Applications of WEDM process include extrusion dies, fuel injector nozzles, aircraft engine turbine blades and machining of difficult-to-machine materials like tool steel, titanium and cemented carbides. Wire-cut EDM has experienced explosive growth and sophistication of equipment, and in the demands made on the basic tool of the process i.e. wire. In this paper, we describe technologies from the widely used brass wire electrodes to the latest coated wire electrodes which have been developed and helped the users demand and need maximum productivity and throughput, increased accuracy, and predictable performance. Higher angles of taper, thicker workpieces, automatic wire threading, and long periods of unattended operation, make choosing the optimum wire a much more critical factor in achieving a successful operation. Keywords: Brass wire electrodes; conductivity; tensile strength; elongation; coated wire; Abrasive assisted wire 1. Introduction Electronics technologies provide not only information processing and communications devices, but also household electric appliances and automobile devices. Manufacturing these devices and appliances requires sophisticated production technologies, for example, precision metallic mold technology for manufacturing IC lead frames. Wire electro discharge machining is one precision manufacturing technology which makes it possible to machine hard materials accurately, for example super hardening metallic molds and ceramics. Fig.1 shows a model wire electro discharge machining WEDM system. WEDM is a technology based on the discharge phenomenon. Conductive metal wires (diameter from 0.05mm to 0.35mm) are used in three-dimensional machining after programming the required shape, in a process similar to that using a coping saw. This method provides wires continuously and it is not necessary to take consumption into consideration which offers the advantage of automatic operation of the cutting machine. 2. History of development of wire electrodes The Russian Razarenko couple designed the first electro discharge machining in Ten years later, a numerically controllable wire discharge machine was developed, and in 1969 a machine for mass production was developed. Most controllers of wire discharge machines have been improved with computer numerical control equipment. As wire for electro discharge machining, pure copper wire was used in the early 1970s, but there was a problem in accuracy and strength. In the second half of the 1970s, instead of pure copper wire, brass wire was started to be used. In 1980 copper wire electrodes coated with Zn, and in the next year brass wire electrodes coated with Zn were developed and utilized). Brass wire electrodes with added aluminum or chromium) were also developed. In 1990 and afterwards, a brass wire electrode coated with Zn for high-precision cutting, and a coated Cu-50mass%Zn for high-speed cutting were developed). After that Zn coated wire electrodes for high-speed cutting, and core materials of stainless wire coated with Cu were developed and utilized). In Hitachi Cable, we developed and utilized mainly brass wire which offered higher cutting speed by increased Zn concentration as described later and wire electrodes made of brass with added titanium and aluminum for Punjab Technical University, Jalandhar-Kapurthala Highway, Kapurthala, Punjab (INDIA) 70

2 improved heat resistance when cutting thick materials [2, 3, 4] 3. WEDM process WEDM is a widely accepted non-tradition material removal process fig.2. The material removal mechanism of WEDM is the same as that of electrical discharge machining. It has been widely accepted that the metal removal mechanism in EDM is predominantly a thermal effect in nature [5]. The basic principle behind EDM process is a series of electric sparks between the work piece and wire electrode. The electrical discharging process generates a tremendous amount of heat causing melting or even evaporation in the local surface layers on both wire-electrode and work piece sides. The heat also causes vaporization of the dielectric fluid and induces high-pressure waves, which wash out the molten and/or vaporized metal into pieces from the work piece. Continuously injected dielectric fluid then carries the droplets of metal away. WEDM is considered as a unique adaptation of the conventional EDM process. However, WEDM utilizes a continuously traveling wire electrode made of thin copper, brass or tungsten material, which is capable of achieving very small corner radii. It is desirable that the wire electrode and work piece both be electrically conductive. Fig 1: Mechanism of Wire in (WEDM Process) 4.0 Properties required for wire electrodes 4.1 Action of wire electrode in electro discharge machining The distance between the wire electrode and work piece approaches 5 to 50m in the dielectric fluid, electrons with a high current density flow from the wire electrode at the applied voltage, and an arc electric discharge occurs. Then heat due to the electric discharge and Joule heat from the conductor are generated. These heats flow in the length direction of the wire electrodes and on the side of the dielectric fluid, the wire electrode is cooled. In that case, gas is produced by rapid evaporation in the dielectric fluid, and the wire electrode and the work piece melt and vaporizes, and is dispersed as waste powder. In this model, the wire electrode must be able to easily undergo electric discharge and also have high heat resistance and good heat spreading ability [6]. 4.2 Properties required for wire electrodes Properties required for wire electrodes, as shown in Fig. 3. The most important properties are: a. Electric discharge performance b. Heat resistance c. Low calorification d. Heat release. Electric discharge performance needs stable discharge for a high-precision machining face, and high-energy discharge for high-speed cutting. Heat resistance is needed to withstand high temperature at pulse arc discharge. Low calorification is needed to control Joule heat at electric discharge. Heat release is needed to release the heat of arc discharge and Joule heat rapidly. Naturally, cost performance and workability for quick delivery are also necessary. Automatic threading also requires easy drawing for mass productivity. Fig.4 summarizes the relation between the development problem for high performance wire electrodes described above, and its concrete achievement method. Fig.2: Model for WEDM Process[15] Punjab Technical University, Jalandhar-Kapurthala Highway, Kapurthala, Punjab (INDIA) 71

3 Fig. 5(a) Crystal structure of α phase (b) Crystal structure of β phase[1] Fig.3: Properties required for wire electrodes[1] 4.3 Structure and feature of wire electrodes Wire electrodes Generally, the Cu-Zn binary phase diagram shows [7] α single phase alloy, consisting of F.C.C as shown in Fig. 5(a), which is machined easily up to 35mass%, but over 40mass% it is a two phase alloy of α phase and β phase. β phase makes it difficult to cold-draw into a fine straight wire by preventing cold machining [8]. This β phase consists of ordered body-centered cubic crystals shown in Fig.5 (b), which are difficult to work at room temperature. But for wire electrodes, it is useful to raise Zn concentration, so that a drawing technology by devising a machining method in the two phase area of α phase and β phase. Fig. 6 shows metallurgical structure of single wire electrodes with a diameter of 0.2mm in the direction of drawing. This figure shows the β phase in the case of a high Zn concentration. Fig. 4: Items for development of wire electrodes[1] Fig.6 (a) 35mass% Zn (b) 40% mass Zn (c) 43% mass Zn[1] 4.4 Properties of WEDM wires The following section describes the key physical properties of EDM wires and how they relate to real world cutting: Conductivity It is often expressed as a percentage of IACS, which is a comparison to the conductivity of pure annealed Copper wire [9]. Conductivity is an important property of an EDM wire, since it determines how readily the power supply energy is transferred over the distance from the power feed contact to the actual point of cutting. This distance can be considerable, especially if the job is being cut with open guides to clear a workpiece obstruction. Low wire conductivity will result in a voltage drop and associated energy loss over the distance from the power feed to the cutting point. This is not insignificant when one considers that the peak current of most modern power supplies often exceeds 100 amps. Tensile Strength Indicates the ability of the wire to withstand the wire tension imposed upon the wire during cutting, in order to make a vertically straight cut. Since all commonly used wire EDMs are imported, tensile strength is most commonly specified in the metric units of N/mm 2. EDM wires are considered hard at tensile strengths of 900 N/mm 2 or above. EDM wires are considered half hard at tensile strengths at or about 490 N/mm 2. EDM wires are considered soft at tensile strengths at or below 440 N/mm 2 [9]. Hard wires are commonly used for most work, while half hard and soft wires are primarily used for taper cuts where the taper angle is greater than 5 0, since a hard wire will resist bending at the guide pivot and will result in inaccurate taper cutting. Half hard and soft wires are often unsuitable for automatic threading Punjab Technical University, Jalandhar-Kapurthala Highway, Kapurthala, Punjab (INDIA) 72

4 unless the machine is specifically design to work with these wires. Elongation Describes how much the wire gives or plastically deforms just before it breaks. Elongation is measured in % of the gauge length used in a given test. It could also be stated that elongation relates to how brittle the wire is. Usually, hard wires have elongation that is considerably lower than half hard wires. Elongation is an important property, since EDM wire operates in a hostile environment in which it is under high tension and being attacked by thousands of sparks which are eating at its crosssection. A brittle wire might snap at the first overload condition, while a more ductile wire is more likely to accept a temporary overload by giving a little and continuing to cut. Melting Point is not normally specified for a given wire, but is obviously important since EDM is a spark erosion process, and preferably that wire electrode should be somewhat resistant to being melted too quickly by all those sparks. Straightness is another important property of EDM wire that is seldom specified but is critically important to successful auto threading. Flushability is normally not specified for a given wire, but is an important property that relates to how well a wire will actually cut. This property is related to the sublimation temperature of the wire s alloy components that is more in the realm of metallurgy than tool making. Let s just say that the better the flushablity, the faster the wire will cut. Cleanliness is a property that is not specified for EDM wires. Wire can be dirty, due to contamination by residual metal powder left over from the drawing process, drawing lubricant, or paraffin added to the wire by some manufacturers prior to spooling. Dirty wire can ruin your day, resulting in clogged guides and power feeds or slipping belts or rollers. 4.5 Types of wires Before we proceed, a brief discussion on the manufacturing process for EDM wire is in order. Typically, Brass wires start out as a continuously cast 20mm diameter rod. This rod is either cold rolled or cold drawn until it is approximately either a 6mm round or hex cross-section. The wire is then annealed and drawn through a series of dies until it is approximately 0.9mm diameter[6]. In this state, it is commonly called re-draw wire. The re-draw wire is subsequently drawn through another series of diamond dies until it is the final size. At final size, the wire is resistively annealed or thermally tempered in an inert atmosphere, cleaned, and then spooled. Plain wires EDM wire business plain merely means that the wire consists of a single homogeneous component and does not have a coated or composite construction. The plain wire further classified into following categories. Copper Wire was the original EDM wire. At the time it was thought that since Copper wire had high electrical conductivity, it would make the ideal EDM wire. Unfortunately, Copper wire has both low tensile strength and low flushability. This soon became apparent with the development of the 2nd generation pulse type power supplies and Copper wire was soon supplanted by Brass wires. It should be noted that Copper wires are still used occasionally for applications in which Zinc (contained in brass wires or coated wires) is considered an unacceptable contaminant. Brass Wire: was the successor to Copper wire and is still the most commonly used wire today. Brass, which is an alloy of Copper and Zinc, delivers a powerful combination of low cost, reasonable conductivity, high tensile strength, and improved flushability. (If a small amount of Zinc added to Copper wire drastically reduces the conductivity. Hard Brass wire typically has conductivity only 20% of Copper wire.) Brass wire is most commonly available in the following alloys: European: Cu63%Zn37% Asian: Cu65%Zn35% Fig. 6: Brass Wire Since it is the Zinc that gives Brass Wire its improved flushability, some manufacturers now offer a high zinc brass which is Cu60%Zn40%.This increase in Zinc content can increase cutting speed up to 5% in some optimized applications, however, many users who are content to use standard settings may not see a cutting speed increase. It should also be noted that in certain circumstances, a significant Brass deposit can remain on the workpiece after the cut, which can prove to be quite difficult to remove. Unfortunately, it is not practical to cold draw wire with Zinc content in excess of 40%[7]. This fact led to the development of coated wires. Aluminum Brass Wire: The addition of a small percentage of Aluminum to a Brass wire creates a specialty alloy wire. These alloy additions improve the tensile properties of the wire allowing the tensile strength to be brought up to as high as 1,200 N/mm 2 without adversely affecting elongation[8]. Some users claim that these wires are less susceptible to breakage than other types of plain Brass wire. Usage of this type of wire has fallen off to the point that one Punjab Technical University, Jalandhar-Kapurthala Highway, Kapurthala, Punjab (INDIA) 73

5 major manufacturer has announced plans to discontinue it. Fig.7: Aluminum Brass Wire Molybdenum Wire is used in limited applications which require very high tensile strength to provide a reasonable load carrying capacity in small diameter wires. Moly has both a high melting point and high tensile strength. It is often used for small diameter EDM wires; [8]. Moly Wire has both low electrical conductivity and very low flushability. In addition, Moly Wire is very abrasive to power feeds and wire guides, and is often difficult to auto thread. Finally, Moly wire is very expensive. Tungsten Wire has even greater tensile strength and a higher melting point than Moly wire. Tungsten Wire is often an economical alternative to Moly Wire in diameters and smaller[8]. Coated Wires Coated wires are produced by plating or hot-dipping re-draw wire (.9mm) and subsequently drawing it to final size. This is a difficult process, since the plated surface Zinc has to survive the final drawing process and still present a uniform coating to the cut. Currently, no EDM wires are manufactured by a process in which the coating is deposited at finish wire size. Zinc Coated Brass This wire consists of a thin (approximately 5 micron) zinc coating over a core which is one of the standard EDM brass alloys. This wire offers a significant increase in cutting speed over plain brass wires, without any sacrifice in any of the other critical properties. Zinc Coated Brass wires produce exceptional surface finishes when cutting Tungsten Carbide and are often utilized for cutting PCD and graphite. These wires are also utilized in those circumstances in which brass wires produce unacceptable brass plating on the workpiece. Fig. 8: Zinc Coated Brass Zinc Coated Copper EDM Wire This was another early attempt to combine the conductivity of a Copper core with the flushability of Zinc. This wire was used only on early vintage Charmilles machines. It has no current application, since when the sparks penetrate the thin Zinc coating; the cutting rate slows to the tortoise pace of pure Copper wire. X-Type Wire This was the first diffusion annealed wire and is commonly known as SWX, BroncoCut-X, BetaCut- X, X-Kut, and other brand names. The wire consists of a Beta Brass coating over a pure Copper core. X- Type wire was originally developed for Charmilles machines. It has the advantage of the combination of the high conductivity of Copper and a tenacious Zinc rich coating. Its disadvantages are a tensile strength equivalent to half hard Brass combined with poor straightness and high cost relative to Brass wires. It produces significant productivity gains in aerospace alloys such as Inconel and Titanium. Fig. 9: X-Type Wire D-Type Wire This was the second diffusion annealed wire and is commonly known as CobraCut-D, D-Kut, and other brand names. The wire consists of a Beta Brass coating over a Copper core alloyed with 20% Zinc. D-Type wire was originally developed for Agie machines. It has the advantage of the combination of improved conductivity of the 80:20 Copper core, a tenacious Zinc rich coating, and relatively high tensile strength (800 N/mm 2 ). Its disadvantage is its high cost. This wire produces significant productivity gains in virtually all materials and on many different machines. Fig. 10: D-Type Wire Gamma Brass Type Wire This wire features a Brass Core and a Gamma phase Brass outer layer and is commonly known as Z-Kut, Topaz, Gamma-Z, DeltaCut, and other trade names. It is similar to Zinc coated Brass wire, except that the pure Zinc coating is replaced by a Gamma phase Brass coating. It is available with both hard and half hard Brass cores. Its performance is typically 10 to 25% faster than pure Zinc coated wires[8]. Note, Gamma Brass type wires are available with a variety of Brass core compositions. Punjab Technical University, Jalandhar-Kapurthala Highway, Kapurthala, Punjab (INDIA) 74

6 Fig. 11: Gamma Brass Wire Gamma X Type Wire This wire features a Copper Core, a Beta phase Brass intermediate layer, and a Gamma phase Brass outer layer, and is commonly known as Gamma-X. The Beta phase layer is retained because it serves as a backup to the thin Gamma phase layer, in case the discharges break through it. It can be used in the same range of applications as traditional X-Type wires, but offers enhanced performance of approximately 10%. It has the same limitations on both tensile strength and threading as traditional X- Type wires, due to its pure Copper core. Its performance is exceptional on aerospace alloys, especially under good flush conditions. Composite Wires Composite wires combine traditional EDM wire alloys with non-edm materials to create EDM wires with unique properties for specialty applications. Steel Core Wire Steel Core wires utilize a steel core and are commonly know as Compeed, MicroCut, MacroCut, or other trade names. This wire type consists of a steel core, which offers exceptional tensile strength and ductility, a copper intermediate layer to provide conductivity, and a Beta phase Brass outer layer. This type of wire offers exceptional resistance to breakage for tall workpieces, interrupted cuts, or poor flushing conditions, while providing excellent performance. Its primary limitations are high cost, straightness issues, auto-threadability, and possible damage to scrap choppers due to the steel core. Fig. 14: Composite Wire (Steel Core) Fig. 12: Gamma X Type Wire Gamma D Type Wire This wire features an 80:20 Copper Core, a Beta phase Brass intermediate layer, and a Gamma phase Brass outer layer, and is commonly known as Gamma-D or Versacut-H. It can be thought of as a traditional D-Type wire with an additional layer of Gamma phase Brass. It can be used in the same range of applications as traditional D-Type wires, but offers enhanced performance of up to 10%. Abrasive assisted Wire Machining speed and surface integrity continue to be issues of focus in current wire EDM research. In this light, the proof-of-concept of a hybrid wire EDM process that utilizes a wire embedded with electrically non-conducting abrasives has been presented. Material removal in this novel process was realized through electrical erosion that is augmented by two-body abrasion. This is shown to bring about a significant improvement in the removal rate and generate surfaces with minimal recast material, in comparison to an equivalent wire EDM process [10]. Fig. 15: Abrasive Assisted Wire Fig. 13: Gamma D Type Wire Punjab Technical University, Jalandhar-Kapurthala Highway, Kapurthala, Punjab (INDIA) 75

7 5.0 Some review on the Wire breakage, wear and vibration in WEDM The occurrence of wire breakage during WEDM is one of the most undesirable machining characteristics greatly affecting the machining accuracy and performance together with the quality of the part produced. Many attempts have made to develop an adaptive control system providing an online identification of any abnormal machining condition and a control strategy preventing the wire from breaking without compromising the various WEDM performance measures. This section reports research from a collection of published work involving the adaptive control of wire breakage, wire lag and wire vibration [4].Kinoshita et al. [11] analyzed the various types of wire breaking. To prevent the wire breaking they developed a control system by means of monitoring the pulse frequency. Once a sudden rise of pulse frequency was detected, the pulse generator and servo system were turned off instantaneously to prevent the wire rupture. However the machining efficiency was much reduced by such control strategy but the efficiency was good up to work-piece thickness. Rajurkar and Wang [12] experimentally investigated the material removal rate for varying machining parameters. The experimental findings are used in a developed thermal model to analyze the wire rupture (breakage) phenomena. The probable causes leading to wire rupture are failure under excessive thermal load, failure through short circuiting and wire vibration, the most important among these being the thermal load. Tosun and Cogun [13] investigated the effect of cutting parameters on wire electrode wear, material removal rate and mean surface roughness in WEDM on steel with brass wire using regression analysis technique. It was observed that, the WWR increases with the increase in pulse duration and open circuit voltage. It gets decreased with increase in wire speed due to the reducing number of craters per unit length of wire. The minimum value of WWR was observed at open circuit voltage of, pulse duration of, wire speed of and dielectric flushing pressure equal to 1.2. A very low value of experimental error was observed indicating the high accuracy in results. Puri and Bhattacharya [14] investigated the variation of the geometrical inaccuracy caused by cutting speed and wire lag with various machine control parameters on die steel on WEDM using Taguchi method. It was observed that, for the minimum geometrical inaccuracy, the difference between the offset values for the rough cut and the trim cut should be as high as possible. The average cutting speed is affected by pulse-on time, pulse-off time and pulse-peak current for rough cutting; and pulse-on time and constant cutting speed during trim cutting. The surface roughness is influenced by pulse-peak voltage during rough cutting and pulse-on time, pulse-peak voltage, servo spark gap set voltage, dielectric flow rate, wire offset and constant cutting speed during trim cutting. The factors for geometrical inaccuracy for wire lag are pulse-on time, pulse-off time and pulse-peak current during rough cutting; and pulse-peak voltage, wire tension, wire offset, servo spark gap set voltage and constant cutting speed during trim cutting. Puri and Bhattacharyya [15] investigated the effect of wire vibration in WEDM. It was reported that, the magnitude and direction of various forces acting along or upon the wire are not always constant, leading to wire vibration. The maximum amplitude of the vibration depends upon the ratio of (H- Height of the job, L- Span of the wire between guides). It was found that the higher the thickness of the workpiece, the larger will be the maximum amplitude of the vibration for a given span of the wire guides and amplitude ( ). Sanchez et al. [21] discussed the influence of work thickness, corner radius and number of trim cuts on the accuracy of WEDM corner cutting. tool steel work material and brass wire were used. It was found that wire lag is responsible for the back-wheel effect in corner cutting and deviation was larger in case of the test-piece with smaller corner radius. It is not possible to achieve an optimum fit along the whole corner (both at and at the exit). There was a reduction in dimensional error upto in case of corners between and.the main factors contributing to the geometrical inaccuracy of the WEDMed part are the various process forces acting on the wire causing it to depart for the programmed path. These forces include the mechanical forces produced by the pressure from the gas bubbles formed by the plasma of the erosion mechanism, axial forces applied to straighten the wire, the hydraulic forces induced by the flushing, the electrostatic forces acting on the wire and the electrodynamic forces inherent to the spark generation [16, 17]. As a result, the static deflection in the form of a lag effect of the wire is critically studied in order to produce an accurate cutting tool path. Several authors [18, 14, 19] performed a parametric study on the geometrical inaccuracy of the part caused by the wire lag and attempted to model WEDM process mathematically. Whereas Beltrami and Dauw [20] monitored and controlled the wire position online by means of an optical sensor with a control algorithm enabling virtually any contour to be cut at a relatively high cutting speed. A number of geometric tool motion compensation methods, which increase the machining gap and prevent gauging or wire breakages when cutting areas with high curvatures such as corners with small radii have also been developed [21,22]. Lin et al. [23] developed a control strategy based on the fuzzy logic to improve the machining accuracy and concentrated sparking at corner parts without affecting the cutting feed rates. Punjab Technical University, Jalandhar-Kapurthala Highway, Kapurthala, Punjab (INDIA) 76

8 6.0 Problems in Wire EDM during Corner Cutting In the case of corner cutting, the geometrical inaccuracy is mainly caused by the following: 1. The wire deflection phenomenon: in fact, the forces acting upon the wire pull it backwards causing it tobend. A tensile force is applied to the wire in order to compensate this effect, but it is not possible to completely avoid the wire deflection without breaking the wire. 2. The change of the direction of the wire s motion. This causes a change of the wire deflection that results from the external loads exerted on the wire. The forces due to the material removal process and to the flushing system also change their direction and magnitude, and the equilibrium of the cutting process is disturbed. 3. The intensification of the electric field in the neighborhood of the corner crest. This causes the instability of the material removal rate. 4. The increase of material removal rate close to the corner crest due to the temperature rising up that is caused, not only by the above-mentioned intensification, but also because the generated heat is difficult to dissipate in the corner s section. 7.0 Conclusions Plain brass was an advance over copper wires. Composite wires have replaced zinc-coated as the wire of choice for workpieces. The Composite wires have a plain carbon steel core that is surrounded by a layer of pure copper and coated on the outside with zinc-enriched brass. Wires with greater tensile strength can be made, but they face diminishing benefits in terms of increased resistance to breakage, and greater tensile strength is usually obtained at the expense of fracture toughness. For tall work pieces copper clad steel wires are used. The zinc-enriched outer coating of brass improves flushability; its thickness determines how long it will last in the cut. Diffusion annealed wires offer resistance to breakage. Alpha phase, beta phase and gamma phase coatings have significant improvement over plain wires. These high performance wires significantly increase wire EDM productivity but are associated with certain limitations such as high cost, flaking, straightness and possible damage to scrap chopper and may not be used on all the wire EDM machines. 8. Acknowledgement The authors would like to thanks the support of Thapar University, Patiala, M.M.University Mullana- Ambala in Mechanical Engineering Department, India. REFERENCES 1. Aoyama, Seigi (2001), Development of High Performance Wire Electrode for Wire Electric Discharge Machining, Journal of Japan Society of Electrical Machining Engineers, (35), No Kimura, T. and Aoyama, S. (1998), Katagijutsu Seminar, (34), Ichikawa, M. (1995), Kinzoku Puresu, May, N. Sato, T. Takano, K. Akasaka, M. Saito, S. Inoue and K. Ishibashi,1985, Furukawadenkou Jihou, (75), Ho, K.H., Newman, S. T, Rahimifard, R. D. Allen,(2004), State of the art in wire electrical discharge machining, International Journal of Machine Tools & Manufacture, (44), pp Aoyama, S., Tamura, K., Sato, T., Kimura, T., Sawahata K. and Nagai, T. (1991), Hitachi Cable Review, (18), Hansen M. and Anderko, K. (1958), Constitution of Binary Alloys, Second Edition, McGraw-Hill, New York, 650, (1958). 8. Roger, Kern. (2007), EDM Wire Primer, EDM Today, Jan-Feb, pp United States Patent No Kinoshita, N. Fukui, M., Gamo, G. (1982), Control of wire EDM preventing from breaking, Annals CIRP, Vol.31, pp Rajurkar, K. P. and Wang, W. M (1991), On line monitor and control for wire breakage in WEDM, Annals CIRP,40 (1),pp Tosun, N., Cogun, C., Inan, A. (2003), The effect of cutting parameters on work piece surface roughness in wire EDM, Machining Science and Technology, Vol.7, No.2, pp Puri, A.B, Bhattacharyya,B.(2003), An analysis and optimization of the geometrical inaccuracy due to wire lag phenomenon in WEDM, International Journal of Machine Tools and Manufacture,(43), pp Puri, A.B, Bhattacharyya,B.,(2003a), Modelling and analysis of the wire-tool vibration in wire-cut EDM, Journal of Materials Processing Technology, Vol.141, pp Dauw, D.F.,Beltrami, I. (1994), High-precision wire-edm by online wire positioning control, Annals CIRP 43 (1)), pp Kinsohita,N., Fukui, M., Kimura, Y.,(1984), Study on Wire- EDM: in process measurement of mechanical behavior of electrode wire, Ann. CIRP 33 (1),pp Luo, Y.F. (1999), Rupture failure and mechanical strength of the electrode wire used in wire EDM, Journal of Material Process Technology, 94 (2 3), pp Punjab Technical University, Jalandhar-Kapurthala Highway, Kapurthala, Punjab (INDIA) 77

9 18. Huang, J.T., Liao, Y.S. (1997), A Study of Finish Cutting Operation Number and Machining Parameters Setting in Wire Electrical Discharge Machining, Proceedings of International Conference on Precision Machining (ICPE 97), Taipei, Taiwan. 19. Beltrami, I., Dauw, D., (1996), A simplified post process for wire cut EDM, Journal of Material Process Technology, 58 (4), pp Wang, B.,Ravani,(2003), Computer aided contouring operation for travelling wire electric discharge machining (EDM), Computer-Aided Design, 35 (10), pp Dekeyser, W.L. Snoeys, R., (1989), Geometric Accuracy of Wire EDM, Proceedings of the Ninth International Symposium for Electro-Machining (ISM-9), Nagoyo, Japan,. 22. Lin, C.T., Chung, I.F., Huang, S.Y. (2001), Improvement of machining accuracy by fuzzy logic at corner parts of wire- EDM, Fuzzy Sets System, 122 (3), pp Punjab Technical University, Jalandhar-Kapurthala Highway, Kapurthala, Punjab (INDIA) 78