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  1. 1. Prof. Vijay D.Patel, Dr. Rajeev V. Vaghmare / International Journal of Engineering Researchand Applications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.805-816805 | P a g eA Review of recent work in wire electrical discharge machining(WEDM)Prof. Vijay D.Patel*, Dr. Rajeev V. Vaghmare***(Assistsant Professor in Mechatronics at U.V.Patel collage of engginering ,Mehsana, Gujarat)**(Principal,SABAR institute of technology for GIRLS, Majra,Gujarat)AbstractWire electrical discharge machining(WEDM) is a specialized thermal machiningprocess capable of accurately machining partswith varying hardness or complex shapes, whichhave sharp edges that are very difficult to bemachined by the main stream machiningprocesses. This practical technology of theWEDM process is based on the conventionalEDM sparking phenomenon utilizing the widelyaccepted non-contact technique of materialremoval. Since the introduction of the process,WEDM has evolved from a simple means ofmaking tools and dies to the best alternative ofproducing micro-scale parts with the highestdegree of dimensional accuracy and surfacefinish quality.This paper reviews the vast array ofresearch work carried out from the EDMprocess to the development of the WEDM. Itreports on the WEDM research involving theoptimization of the process parameterssurveying the influence of the various factorsaffecting the machining performance andproductivity. The paper also highlights theadaptive monitoring and control of the processinvestigating the feasibility of the differentcontrol strategies of obtaining the optimalmachining conditions. A wide range of WEDMindustrial applications are reported togetherwith the development of the hybrid machiningprocesses. The final part of the paper discussesthese developments and outlines the possibletrends for future WEDM research.Keywords: Wire electrical discharge machining(WEDM);Process optimization; Cutting rate;Material removal rate; Surface finish Electricdischarge machining (EDM), Metal removal rate(MRR), Surface roughness (SR)I. INTRODUCTIONWire electrical discharge machining(WEDM) is a widely accepted non-traditionalmaterial removal process used to manufacturecomponents with intricate shapes and profiles. It isconsidered as a unique adaptation of theconventional EDM process, which uses an electrodeto initialize the sparking process. However, WEDMutilizes a continuously travelling wire electrodemade of thin copper, brass or tungsten of diameter0.05–0.3 mm, which is capable of achieving verysmall Corner radii. The wire is kept in tension usinga mechanical tensioning device reducing thetendency of producing inaccurate parts. During theWEDM process, the material is eroded ahead of thewire and there is no direct contact between the workpiece and the wire, eliminating the mechanicalstresses during machining. In addition, the WEDMprocess is able to machine exotic and high strengthand temperature resistive (HSTR) materials andeliminate the geometrical changes occurring in themachining of heat-treated steels.WEDM was first introduced to themanufacturing industry in the late 1960s. Thedevelopment of the process was the result of seekinga technique to replace the machined electrode usedin EDM. In 1974, D.H. Dule-bohn applied theoptical-line follower system to automatically controlthe shape of the component to be machined by theWEDM process [1]. By 1975, its popularity wasrapidly increasing, as the process and its capabilitieswere better understood by the industry [2]. It wasonly towards the end of the 1970s, when computernumerical control (CNC) system was initiated intoWEDM that brought about a major evolution of themachining process. As a result, the broadcapabilities of the WEDM process were extensivelyexploited for any through-hole machining owing tothe wire, which has to pass through the part to bemachined. The common applications of WEDMinclude the fabrication of the stamping and extrusiontools and dies, fixtures and gauges, prototypes,aircraft and medical parts, and grinding wheel formtools.This paper provides a review on the variousacademic research areas involving the WEDMprocess, and is the sister paper to a review by Hoand Newman [3] on die-sinking EDM. It firstpresents the process overview based on the widelyaccepted principle of thermal conduction andhighlights some of its applications. The main sectionof the paper focuses on the major WEDM researchactivities, which include the WEDM processoptimization together with the WEDM processmonitoring and control. The final part of the paperdiscusses these topics and suggests the futureWEDM research direction.2. WEDMThis section provides the basic principle ofthe WEDM process and the variations of the process
  2. 2. Prof. Vijay D.Patel, Dr. Rajeev V. Vaghmare / International Journal of Engineering Researchand Applications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.805-816806 | P a g ecombining other material removal techniques.2.1. ProcessThe material removal mechanism ofWEDM is very similar to the conventional EDMprocess involving the erosion effect produced by theelectrical discharges (sparks). In WEDM, materialis eroded from the work-piece by a series of discretesparks occurring between the work piece and thewire separated by a stream of dielectric fluid, whichis continuously fed to the machining zone [4].However, today’s WEDM process is commonlyconducted on work pieces that are totallysubmerged in a tank filled with dielectric fluid.Such a submerged method of WEDM promotestemperature stabilization and efficient flushingespecially in cases where the work piece hasvarying thickness. The WEDM process makes useof electrical energy generating a channel of plasmabetween the cathode and anode [5], and turns it intothermal energy [6] at a temperature in the range of8000–12,000 vC [7] or as high as 20,000 vC [8]initializing a substantial amount of heating andmelting of material on the surface of each pole.When the pulsating direct current power supplyoccurring between 20,000 and 30,000 Hz [9] isturned off, the plasma channel breaks down. Thiscauses a sudden reduction in the temperatureallowing the circulating dielectric fluid to implorethe plasma channel and flush the molten particlesfrom the pole surfaces in the form of microscopicdebris.While the material removal mechanisms ofEDM and WEDM are similar, their functionalcharacteristics are not identical. WEDM uses a thinwire continuously feeding through the work pieceby a microprocessor, which enable parts of complexshapes to be machined with exceptional highaccuracy. A varying degree of taper ranging from15vfor a 100 mm thick to 30vfor a 400 mm thickworkpiece can also be obtained on the cut surface.The microprocessor also constantly main-tains thegap between the wire and the work piece, whichvaries from 0.025 to 0.05 mm [2]. WEDMeliminates the need for elaborate pre-shapedelectrodes, which are commonly required in EDMto perform the roughing and finishing operations. Inthe case of WEDM, the wire has to make severalmachining passes along the profile to be machinedto attain the required dimensional accuracy andsurface finish (SR) quality. Kunieda and Furudate[10] tested the feasibility of con-ducting dryWEDM to improve the accuracy of the fin-ishingoperations, which was conducted in a gasatmosphere without using dielectric fluid. Thetypical WEDM cutting rates (CRs) are 300mm2/min for a 50 mm thick D2 tool steel and 750mm2/min for a 150 mm thick aluminium [11], andSR quality is as fine as 0.04–0.25 lRa. In addition,WEDM uses deionised water instead of hydrocarbonoil as the dielectric fluid and contains it within thesparking zone. The deionised water is not suitablefor conventional EDM as it causes rapid electrodewear, but its low viscosity and rapid cooling ratemake it ideal for WEDM [12].3. Main areas of researchThe authors have organized the variousWEDM research into two major areas namelyWEDM process optimization together with WEDMprocess monitoring and control.3.1. Process OptimizationToday, the most effective machiningstrategy is determined by identifying the differentfactors affecting the WEDM process and seeking thedifferent ways of obtaining the optimal machiningcondition and performance. This section provides astudy on the numerous machining strategiesinvolving the design of the process parameter andthe modeling of the process.3.1.1. Process parameters designThe settings for the various processparameters required in the WEDM process play acrucial role in producing an optimal machiningperformance. This section shows some of theanalytical and statistical methods used to study theeffects of the parameters on the typical WEDMperformance measures such as CR, MRR and SR. affecting the performancemeasures.WEDM is a complex machining processcontrolled by a large number of process parameterssuch as the pulse duration, discharge frequency anddischarge current intensity. Any slight variations inthe process parameters can affect the machiningperformance measures such as surface roughnessand CR, which are two of the most significantaspects of the WEDM operation [44]. Suziki andKishi [45] studied the reduction of discharge energyto yield a better surface roughness, while Luo [46]discovered the additional need for a high-energyefficiency to maintain a high machining rate withoutdamaging the wire. Several authors [47] have alsostudied the evolution of the wire tool performanceaffecting the machining accuracy, costs andperformance measures.The selection of appropriate machiningconditions for the WEDM process is based on theanalysis relating the various process parameters todifferent performance measures namely the CR,MRR and SR. Traditionally; this was carried out byrelying heavily on the operator’s experience orconservative technological data provided by theWEDM equipment manufacturers, which producedinconsistent machining performance. Levy andMaggi [48] demonstrated that the parameter settings
  3. 3. Prof. Vijay D.Patel, Dr. Rajeev V. Vaghmare / International Journal of Engineering Researchand Applications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.805-816807 | P a g egiven by the manufacturers are only applicable forthe common steel grades. The settings formachining new materials such as advancedceramics and MMCs have to be further optimizedexperimentally. Effects of the process parameters on thecutting rate. Many different types of problem-solving quality tools have been used to investigatethe significant factors and its inter-relationshipswith the other variables in obtaining an optimalWEDM CR. Konda et al. [49] classified the variouspotential factors affecting the WEDM performancemeasures into five major categories namely thedifferent properties of the work piece material anddielectric fluid, machine characteristics, adjustablemachining parameters, and component geometry. Inaddition, they applied the design of experiments(DOE) technique to study and optimize the possibleeffects of variables during process design anddevelopment, and validated the experimental resultsusing noise-to-signal (S/N) ratio analysis. Tarng etal. [50] employed a neural network system with theapplication of a simulated annealing algorithm forsolving the multi-response optimization problem. Itwas found that the machining parameters such asthe pulse on/off duration, peak current, open circuitvolt-age, servo reference voltage, electricalcapacitance and table speed are the criticalparameters for the estimation of the CR and SR.Huang et al. [51] argued that several publishedworks [50,52,53] are concerned mostly with theoptimization of parameters for the roughing cuttingoperations and proposed a practical strategy ofprocess planning from roughing to finishingoperations. The experimental results showed thatthe pulse on-time and the distance between the wireperiphery and the work piece surface affect the CRand SR significantly. The effects of the dischargeenergy on the CR and SR of a MMC have also beeninvestigated [54].3.1.2. Process modelingIn addition, the modeling of the WEDMprocess by means of mathematical techniques hasalso been applied to effectively relate the largenumber of process variables to the differentperformance of the process. Speeding and Wang[62] developed the modeling techniques using theresponse surface methodology and artificial neuralnetwork technology to predict the processperformance such as CR, SR and surface wavinesswithin a reasonable large range of input factorlevels. Liu and Esterling [63] proposed a solidmodeling method, which can precisely represent thegeometry cut by the WEDM process, whereas Hsueet al. [64] developed a model to estimate the MRRduring geo-metrical cutting by considering wiredeflection with transformed exponential trajectoryof the wire centre. Spur and Scho¨nbeck [65]designed a theoretical model studying the influenceof the workpiece material and the pulse-typeproperties on the WEDM of a work-piece with ananodic polarity. Han et al. [66] developed asimulation system, which accurately reproduces thedischarge phenomena of WEDM. The system alsoapplies an adaptive control, which automaticallygenerates an optimal machining condition for highprecision WEDM.3.2. Process monitoring and controlThe application of the adaptive controlsystems to the WEDM is vital for the monitoringand control of the process. This section investigatesthe advanced monitoring and control systemsincluding the fuzzy, the wire breakage and the self-tuning adaptive control systems used in the WEDMprocess.3.2.1. Fuzzy control systemThe proportional controllers havetraditionally been used in the servo feed controlsystem to monitor and evaluate the gap conditionduring the WEDM process. However, theperformance of the controllers was limited by themachining conditions, which considerably vary withthe parameters settings. Kinoshita et al. [67]investigated the effects of wire feed rate, wirewinding speed, wire tension and electricalparameters on the gap conditions during WEDM. Asa result, many conventional control algorithms basedon explicit mathematical and statistical models havebeen developed for EDM or WEDM operations [68–72]. Several authors [73,74] have also developed apulse discrimination sys-tem providing a means ofanalyzing and monitoring the pulse trains under thevarious WEDM conditions quantitatively. Althoughthese types of control systems can be applied to awide range of machining conditions, it cannotrespond to the gap condition when there is anunexpected disturbance [75].In recent years, the fuzzy control system has beenapplied to WEDM process to achieve optimum andhighly efficient machining. Several authors claimedthat the fuzzy logic control system implements acontrol strategy, which captures the expert’sknowledge or operator’s experience in maintainingthe desired machining operation [76]. In addition,the fuzzy logic controller does not require anycomprehensive mathematical models adapting to thedynamic behavior of the WEDM operation [77].Several authors [75,78] proposed the sparkingfrequency monitoring and adaptive control systemsbased on the fuzzy logic control and the adjustingstrategies, which can be applied to a wide range ofmachining conditions. Liao and Woo [79] alsodesigned a fuzzy controller with an online pulsemonitoring system isolating the discharging noiseand discriminating the ignition delay time of each
  4. 4. Prof. Vijay D.Patel, Dr. Rajeev V. Vaghmare / International Journal of Engineering Researchand Applications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.805-816808 | P a g epulse. EDM pulses can be classified into open,spark, arc, off or short, which are dependent on theignition delay time, and have a direct influence onthe MRR, SR, electrode wear and accuracy of thepart [80,81].3.2.2. Wire inaccuracy adaptive control systemsThe occurrence of wire breakage duringWEDM is one of the most undesirable machiningcharacteristics greatly affecting the machiningaccuracy and performance together with the qualityof the part produced. Many attempts have made todevelop an adaptive control system providing anonline identification of any abnormal machiningcondition and a control strategy preventing the wirefrom breaking without compromising the variousWEDM performance measures. This section reportsresearch from a collection of published workinvolving the adaptive control of wire breakage,wire lag and wire vibration. Wire breakage. A wide variety of thecontrol strategies preventing the wire from breakingare built on the knowledge of the characteristics ofwire break-age. Kinoshita et al. [82] observed therapid rise in pulse frequency of the gap voltage,which continues for about 5–40 ms before the wirebreaks. They developed a monitoring and controlsystem that switches off the pulse generator andservo system preventing the wire from breaking butit affects the machining efficiency. Several authors[83,84] also suggested that the concentration ofelectrical discharges at a certain point of the wire,which causes an increase in the localizedtemperature resulting in the breakage of the wire.However, the adaptive control system concentratingon the detection of the sparking location and thereduction of the discharge energy was developedwithout making any considerations to the MRR.The breakage of the wire has also been linked to therise in the number of short-circuit pulses lasting formore than 30 ms until the wire broke [85].Other authors [86] argued that the wire breakage iscorrelated to the sudden increase in sparkingfrequency. It was also found that their proposedmonitoring and control system based on the onlineanalysis of the sparking frequency and the real-timeregulation of the pulse off-time affects the MRR.Liao et al. [87] remedied the problem by relating theMRR to the machining parameters and using a newcomputer-aided pulse discrimination system basedon the pulse train analysis to improve the machiningspeed. Whereas Yan and Liao [88,89] applied aself-learning fuzzy control strategy not only tocontrol the sparking frequency but also to maintaina high MRR by adjusting in real time the off timepulse under a constant feed-rate machiningcondition.The breaking of the wire is also due to theexcessive thermal load producing unwarranted heaton the wire electrode. Most of the thermal energygenerated during the WEDM process is transferredto the wire while the rest is lost to the flushing fluidor radiation [86]. How-ever, when the instantaneousenergy rate exceeds a certain limit depending on thethermal properties of the wire material, the wire willbreak. Several authors [90–92] investigated theinfluence of the various machining parameters onthe thermal load of the wire and developed a thermalmodel simulating the WEDM process. In addition tothe sparking characteristics or the temperaturedistribution, the mechanical strength of the wire alsohas a significant effect on the occurrence of the wirebreakage. Luo [93] claimed that the wire materialyielding and fracture contribute to the wirebreakage, whilst an increase in temperatureaggravates the failure process. Wire lag and wire vibration. The mainfactors contributing to the geometrical inaccuracy ofthe WEDMed part are the various process forcesacting on the wire causing it to depart for theprogrammed path. These forces include themechanical forces produced by the pressure from thegas bubbles formed by the plasma of the erosionmechanism, axial forces applied to straighten thewire, the hydraulic forces induced by the flushing,the electro-static forces acting on the wire and theelectro-dynamic forces inherent to the sparkgeneration [94,95].As a result, the static deflection in the formof a lag effect of the wire is critically studied inorder to pro-duce an accurate cutting tool path.Several authors [93,96,97] performed a parametricstudy on the geo-metrical inaccuracy of the partcaused by the wire lag and attempted to modelWEDM process mathematically. Whereas Beltramiand Dauw [98] monitored and controlled the wireposition online by means of an optical sensor with acontrol algorithm enabling virtually any contour tobe cut at a relatively high cutting speed. A numberof geometric tool motion compensation methods,which increase the machining gap and preventgauging or wire breakages when cutting areas withhigh curvatures such as corners with small radii havealso been developed [99,100]. Lin et al. [101]developed a control strategy based on the fuzzylogic to improve the machining accuracy andconcentrated sparking at corner parts withoutaffecting the cutting feed rates.In addition, the dynamic behavior of thewire during WEDM is also restrained to avoidcutting inaccuracies. There are a few discussions onthe design and development of a monitoring andcontrol system for compensating the behavior of thewire vibration [86,102]. Dauw et al. [103] also
  5. 5. Prof. Vijay D.Patel, Dr. Rajeev V. Vaghmare / International Journal of Engineering Researchand Applications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.805-816809 | P a g ereported that the vibration of the wire can besubstantially reduced when the wire and the wireguides are completely submerged in the workingtank filled with deionised water. Several authors[104] derived a mathematical model analysing thetransient response of the wire vibration based on theforce acting on the tool wire in a single dischargeprocess. A number of authors [105,106] reviewedthe research and development of the variousadvanced monitoring and control systems used inEDM and WEDM processes.In addition, the dynamic behavior of thewire during WEDM is also restrained to avoidcutting inaccuracies. There are a few discussions onthe design and development of a monitoring andcontrol system for compensating the behavior of thewire vibration [86,102]. Dauw et al. [103] alsoreported that the vibration of the wire can besubstantially reduced when the wire and the wireguides are completely submerged in the workingtank filled with deionised water. Several authors[104] derived a mathematical model analysing thetransient response of the wire vibration based on theforce acting on the tool wire in a single dischargeprocess. A number of authors [105,106] reviewedthe research and development of the variousadvanced monitoring and control systems used inEDM and WEDM processes.3.2.3. Self-tuning adaptive control systemsIn recent years, the WEDM research anddevelopment has explored control strategiesadjusting to the variation in the power densityrequired in machining a workpiece with varyingthickness. Several authors [82,85] found out that achange in the workpiece thickness duringmachining leads to an increase in the wire thermaldensity and an eventual breaking of the wire.Rajurkar et al. [107,108] proposed an adaptivecontrol system with a multiple input model thatmonitors and controls the sparking frequencyaccording to the online identified workpiece height.Other authors [72] developed a system that involvesan explicit mathematical model requiring a numberof experiments and statistical techniques. Yan et al.[109] used the neural networks to estimate theworkpiece height and the fuzzy control logic tosuppress the wire breakage when a workpiece withvariable height is machined.The application of a knowledge-basedcontrol system to control the adverse WEDMconditions has also been experimented. Snoeys etal. [110] proposed a knowledge-based system,which comprises of three modules, namely workpreparation, process control and operator assistanceor fault diagnosis, enabling the monitoring andcontrol of the WEDM process. The workpreparation module determines the optimalmachining parameter settings, while the operatorassistance and fault diagnostics databases advise theoperators and diagnose the machining errors. Thus,the capabilities of these modules increase theamount of autonomy given to the WEDM machine.Huang and Liao [111] have also indicated theimportance of the operator assist-ance and faultdiagnostics systems for the WEDM pro-cess. Theyproposed a prototype artificial neural network-basedexpert system for the maintenance schedule and faultdiagnosis of the WEDM. Dekeyser et al. [112]developed a thermal model integrated with an expertsystem for predicting and controlling the thermaloverload experienced on the wire. Although themodel increases the level of machine autonomy, itrequires a large amount of computation, which slowsdown the processing speed and undermines theonline control performance.4. Discussion and future research directionsThe authors have classified the wide rangeof published works relating to the WEDM processinto three major areas, namely optimizing theprocess variables, monitoring and control theprocess, and WEDM developments. This sectiondiscusses the classified WEDM research areas andthe possible future research directions, illustrated inFig. 1.4.1. Optimizing the process variablesThe optimization of the WEDM processoften proves to be a difficult task owing to the manyregulating machining variables. A single parameterchange will influence the process in a complex way[52]. Thus, the various factors affecting the processhas to be understood in order to determine the trendsof the process variation, as discussed in Section4.1.1. The selection of the best combination of theprocess parameters for an optimal machiningperformance involves analytical and statisticalmethods. However, it is very complicated to relatethe input process parameter with the outputperformance measures and derive an optimal resultusing a simulated algorithm. The CR, MRR and SRare usually opted as the measures of the processperformance. Nevertheless, these methods providean effective means of identifying the variablesaffecting the machining performance.In addition, the modeling of the process isalso an effective way of solving the tedious problemof relating the process parameters to theperformance measures. As mentioned in Section4.1.2, several attempts have been carried out tomodel the process investigating into the influence ofthe machining parameters on WEDM performanceand identifying the optimal machining conditionfrom the infinite number of combinations. As aresult, it provides an accurate dimensional inspectionand verification of the process yielding a betterstability and higher productivity for the WEDM
  6. 6. Prof. Vijay D.Patel, Dr. Rajeev V. Vaghmare / International Journal of Engineering Researchand Applications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.805-816810 | P a g eprocess. However, the complex and random natureof the erosion process in WEDM requires theapplication of deterministic as well as stochastictechniques [61]. Therefore, the optimization of theWEDM process will remain a key research areamatching the numerous process parameters with theperformance measures.Fig. 1. Classification of major WEDM researchareas (corresponding section numbers are inbrackets).4.2. Monitoring and control the processOver the years, the monitoring and controlsystems have made an important contribution inminimizing the effect of disturbances on theWEDM performance. The multi-parametermachining settings have made it difficult to clearlyunderstand and obtain the optimal machiningconditions. It requires a control algorithm that isoften based on explicit mathematical and statisticalmodels to cope with the machining process.However, the application of the fuzzy control logichas brought about a drastic change to theconventional way of monitoring and controlling theWEDM process. The fuzzy control logic is able toconsider several machining variables, weigh thesignificant factors affecting the process and makechanges to the machining conditions withoutapplying the detailed mathematical model, asmentioned in Section 4.2.1. In addition, thefeasibility of applying the expert system capable ofgiving advice and solving problems has also beenexplored [110]. Such a system would greatly appealto the shop floor operational needs demandingunattended WEDM operation.The risk of the wire breakage and the bending of thewire have also limited the efficiency and accuracyof the WEDM process. The occurrence of the wirebreakage directly reduces the already lowmachining speed affecting the overall productivityof the machining process. Although, the controlstrategies reported in Section 4.2.2 are designed tosolve the problems of wire break-age, it solely relieson the indication of the possible Occurrence andgenerates inadequate results investigating the rootcause of the wire breakage phenomenon. Thesestrategies may therefore be deemed to be a set-backwhen machining a workpiece with variable heightsrequiring a drastic change in the machiningconditions.In addition, the wire vibration behavior andstatic deflection easily influence the geometricaccuracy of the part produced. The typical solutionsto these problems are often very conservative innature by increasing the machining gap or reducingthe discharge energy, which is regarded to be a maindrawback for the WEDM process efficiency. Fig. 2shows the huge amount of research workconcentrating on the improvement of the inaccuracycaused by the wire through the application of anadaptive control system. Jennes and Snoey [113]believed that the traditional research purpose wasnot to improve machining efficiency, but to preventfrom wire rupture during the machining process.Hence, one possible new WEDM challenge andfuture work area will be steered towards attaininghigher machining efficiency by acquiring a higherCR and MRR with a low wire consumption andfrequency of wire breakage.Fig. 2. Distribution of the collection WEDMresearch publications.4.3DevelopmentsThe WEDM process is a suitablemachining option in meeting the demands of today’smodern applications. It has been commonly used inthe automotive, aerospace, mould, tool and diemaking industries. WEDM applications can also befound in the medical, optical, dental, jewelleryindustries, and in the automotive and aerospaceR&D areas [114]. Its large pool of applications, asshown in Fig. 2, is largely owed to the machiningtechnique, which is not restricted by the hardness,strength or toughness of the workpiece material. Asmentioned in Section 3, the WEDM of the HSTR,modern composite and advanced ceramic materials,which is showing a growing tend in manyengineering applications, has also been
  7. 7. Prof. Vijay D.Patel, Dr. Rajeev V. Vaghmare / International Journal of Engineering Researchand Applications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.805-816811 | P a g eexperimented. It has replaced the conventionalmeans of machining ceramics, namely theultrasonic machining and laser beam machining,which are not only costly to machine but damagethe surface integrity of the ceramic component.However, with the introduction of over 20 non-traditional machining processes in the past 50 yearsand the rapid growth in the development of harder,tougher and stronger workpiece materials [115], theWEDM process inevitably has to be constantlyrejuvenated in order to compete and satisfy thefuture crucial machining requirements.In addition, the WEDM process has soughtthe benefits of combining with other materialremoval methods to further expand its applicationsand improve the machining characteristics. Theauthors have classified the WEDM machine into thevarious physical characteristics, which clearlydistinguishes the different types of machine featuresaffecting the performance measures, machiningcapacity and auxiliary facilities, as shown in Fig. 3.One of the most practical and precision HMParrangements is the WEDG process used mainly toproduce small size and complicated shape thin rod,which can be easily bent or broken by the lateralforce when using conventional grinding process.The precision of the CNC system is also partlyresponsible for the accuracy of the WEDG [116].Therefore, the HMP processes, in particular theWEDG process, will continue to receive intenseresearch attention especially in the growing field ofmicro-electronics circuitry manufacturing.There is also a major push toward anunattended WEDM operation attaining a machiningperformance level that can be only achieved by askilled operator. Such a goal has been partlyfulfilled through the application of the CNC tocontrol the machining strategies, to prevent the wirebreakage and to automate the self-threadingsystems. An environmentally friendly and high-capacity dielectric regeneration system, whichautonomously maintains the quality of the dielectriccirculating within the WEDM machine, has alsobeen experimented [117]. However, dueconsideration still has to be given to improve theWEDM performance and enhance the level ofautomation for future integration of the EDM andWEDM processes within the CIM environment[118]. It would then be able to reasonably meet theshortage of highly skilled EDM/ WEDM operatorsand achieve a more cost efficient and cost effectivemachining operation.5. ConclusionWEDM is a well-established non-conventional material removal process capable ofmeeting the diverse machining requirements posedby the demanding metal cutting industries. It hasbeen commonly applied for the machining andmicro-machining of parts with intricate shapes andvarying hardness requiring high profile accuracy andtight dimensional tolerances. However the maindisadvantage of the process is the relatively lowmachining speed, as compared to the other non-traditional machining processes such as the laser-cutting process, largely due to its thermal machiningtechnique. In addition, the development of newerand more exotic materials has challenged theviability of the WEDM process in the futuremanufacturing environment. Hence, continuousimprovement needs to be made to the currentWEDM traits in order to extend the machiningcapability and increase the machining productivityand efficiency.The ultimate goal of the WEDM process isto achieve an accurate and efficiency machiningoperation without compromising the machiningperformance. This is mainly carried out byunderstanding the inter-relationship between thevarious factors affecting the process and identifyingthe optimal machining condition from the infinitenumber of combinations. The adaptive monitoringand control systems have also been extensivelyimplemented to tame the transient WEDM behaviorwithout the risk of wire breakages. Moreover,several monitoring and control algorithms based onthe explicit mathematical models, expert’sknowledge or intelligent systems have been reportedto reduce the inaccuracy caused by the vibrationbehavior and static deflection of the wire. With thecontinuous trend towards unattended machiningoperation and automation, the WEDM process has tobe constantly improved to maintain as a competitiveand economical machining operation in the moderntool-room manufacturing arena. Though the authorsbelieve that the WEDM process due to its ability toefficiently machine parts with difficult-to-machinematerials and geometries has it own application areaunmatched by other manufacturing processes.
  8. 8. Prof. Vijay D.Patel, Dr. Rajeev V. Vaghmare / International Journal of Engineering Researchand Applications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.805-816812 | P a g eFig. 3. Classification of wire-cutting EDM machine.References[1] E.C. Jameson, Description anddevelopment of electrical dis-chargemachining (EDM), Electrical DischargeMachining, Society of ManufacturingEngineers, Dearbern, Michigan, 2001, pp.16.[2] G.F. Benedict, Electrical dischargemachining (EDM), Non-TraditionalManufacturing Processes, Marcel Dekker,Inc, New York & Basel, 1987, pp. 231–232.[3] K.H. Ho, S.T. Newman, State of the artelectrical discharge machining (EDM),Int. J. Mach. Tools Manuf. 43 (13) (2003)1287–1300.[4] A.B. Puri, B. Bhattacharyya, An analysisand optimization of the geometricalinaccuracy due to wire lag phenomenon inWEDM, Int. J. Mach. Tools Manuf. 43 (2)(2003) 151–159.[5] E.I. Shobert, What happens in EDM, in:E.C. Jameson (Ed.), Electrical DischargeMachining: Tooling, Methods and Appli-cations, Society of ManufacturingEngineers, Dearbern, Michi-gan, 1983, pp.3–4.[6] H.C. Tsai, B.H. Yan, F.Y. Huang, EDMperformance of Cr/ Cu-based compositeelectrodes, Int. J. Mach. Tools Manuf. 43(3) (2003) 245–252.[7] G. Boothroyd, A.K. Winston, Non-conventional machining processes,Fundamentals of Machining, MarcelDekker, Inc, 1989, pp. 491.[8] J.A. McGeough, Electrodischargemachining, Advanced Meth-ods ofMachining, Chapman & Hall, London,1988, pp. 130.[9] S.F. Krar, A.F. Check, Electrical dischargemachining, Tech-nology of MachineTools, Glencoe/McGraw-Hill, New York,1997, pp. 800.[10] M. Kunieda, C. Furudate, High precisionfinish cutting by dry WEDM, Ann. CIRP50 (1) (2001) 121–124.[11] S. Kalpajian, S.R. Schmid, Materialremoval processes: abras-ive, chemical,electrical and high-energy beam,Manufacturing Processes for EngineeringMaterials, Prentice Hall, New Jersey,2003, pp. 544.[12] E.A. Huntress, Electrical dischargemachining, Am. Machinist 122 (8) (1978)83–98.[13] T. Masuzawa, H.K. Tonshoff, Three-dimensional micromachin-ing bymachining tools, Ann. CIRP 46 (2) (1997)621–628.[14] T. Masuzawa, M. Fujino, K. Kobayashi,T. Suzuski, N. Kinoshita, Wire electro-discharge grinding for micro-machin-ing,Ann. CIRP 34 (1) (1985) 431–434.[15] T. Masuzawa, C.L. Kuo, M. Fujino, Acombined electrical machining process formicronozzle fabrication, Ann. CIRP 43(1994) 189–192.[16] T. Masuzawa, J. Tsukamoto, M. Fujino,Drilling of deep microholes by EDM,Ann. CIRP 38 (1) (1989) 195–198.[17] H.H. Langen, T. Masuzawa, M. Fujino,Modular method for microparts machining
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