Analysis of the influence of EDM parameters on surface quality, MRR and EW of WC–Co

(BQ) The adequate selection of manufacturing conditions is one of the most important aspects to take into consideration in the die-sinking electrical discharge machining (EDM) of conductive ceramics, as these conditions are the ones that are to determine such important characteristics as: surface roughness, electrode wear (EW) and material removal rate, among others. In this work, a study was carried out on the influence of the factors of intensity (I), pulse time (ti) and duty cycle (η) over the listed technological characteristics. The ceramicused in this study was a cemented carbide or hard metal such as 94WC–6Co.
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Analysis of the influence of EDM parameters on surface quality, MRR and EW of WC–CoJournal of Materials Processing Technology 153–154 (2004) 1026–1032Analysis of the influence of EDM parameters on surfacequality, MRR and EW of WC–CoI. Puertas∗ , C.J. Luis, L. ÁlvarezDepartment of Mechanical Engineering (Manufacturing Engineering Section), Public University of Navarre (Spain),Campus de Arrosad´a s/n, Postal Code 31006 Pamplona, Navarre, SpainıAbstractThe adequate selection of manufacturing conditions is one of the most important aspects to take into consideration in the die-sinkingelectrical discharge machining (EDM) of conductive ceramics, as these conditions are the ones that are to determine such importantcharacteristics as: surface roughness, electrode wear (EW) and material removal rate, among others. In this work, a study was carried outon the influence of the factors of intensity (I), pulse time (ti ) and duty cycle (η) over the listed technological characteristics. The ceramicused in this study was a cemented carbide or hard metal such as 94WC–6Co. Approximately 50% of all carbide production is used formachining applications but cemented carbides are also being increasingly used for non-machining applications, such as: mining, oil and gasdrilling, metal forming and forestry tools. Accordingly, mathematical models will be obtained using the technique of design of experiments(DOE) to select the optimal machining conditions for finishing stages. This will be done only using a small number of experiments.© 2004 Elsevier B.V. All rights reserved.Keywords: EDM; Surface roughness; DOE1. IntroductionElectrical discharge machining (EDM) is a non-traditionalmanufacturing process based on removing material from apart by means of a series of repeated electrical discharges(created by electric pulse generators at short intervals) between a tool, called electrode, and the part being machinedin the presence of a dielectric fluid [1]. At the presenttime, EDM is a widespread technique used in industry forhigh-precision machining of all types of conductive materials such as: metals, metallic alloys, graphite, or even someceramic materials, of whatsoever hardness.In spite of their exceptional mechanical and chemicalproperties, ceramic materials have only achieved partial acceptance in the field of industrial applications, due to thedifficulties of processing and the high cost associated withtheir manufacture. Over the past few years, the advances inthe field of EDM made the application of this technologyavailable for the manufacture of conductive ceramic materials. In line with current knowledge, the main inconvenience when applying the EDM technology to the treatmentof ceramic materials is the electrical conductivity of these∗ Corresponding author.E-mail address: inaki.puerta@unavarra.es (I. Puertas).0924-0136/$ – see front matter © 2004 Elsevier B.V. All rights reserved.doi:10.1016/j.jmatprotec.2004.04.346materials. The threshold of electrical resistivity for thesematerials is considered to be between 100 and 300 cm[2,3].In this work, a study focused on the die-sinking EDMof a ceramic material such as cobalt-bonded tungsten carbide (WC–Co), whose field of applications is in constantgrowth, was carried out. Consequently, an analysis on theinfluence of intensity, pulse time and duty cycle over technological variables such as: surface roughness, electrodewear (EW) and material removal rate was performed. Thiswas done using the technique of design of experiments(DOE) and techniques such as multiple linear regressionanalysis. The combined use of these techniques has allowed us to create both first and second-order models,which make it possible to explain the variability associatedwith each of the technological variables studied in thiswork.2. ExperimentalIn this section, there will be a brief description of theequipment used to carry out the EDM experiments, alongwith the ceramic material used and its dimensions. Also, thedesign factors used in this work will be outlined.I. Puertas et al. / Journal of Materials Processing Technology 153–154 (2004) 1026–1032Fig. 1. Die-sinking EDM machine used.2.1. Equipment used in the experimentsThe equipment used in order to carry out the EDM oftungsten carbide was a die-sinking EDM machine of typeONA DATIC D-2030-S. Fig. 1 shows a photograph of thisequipment.The EDM machine was equipped with a magnetic gripin order to hold the parts in place, but, due to the kindof material in question, a mechanical grip was finally usedinstead. In Fig. 2, a photograph illustrating the whole fixturesystem employed in the experiments is shown. In addition,in the same figure, the type of flushing used for the EDMexperiments in order to assure an adequate removal of thedebris from the work gap is shown. In this case, due to itssimplicity and the shallow machining carried out in theseexperiments, jet ...