Electrode wear and material removal rate during EDM of aluminum and mild steel using copper and brass electrodes

(BQ) In the present study an analysis has been done toevaluate the electrode wear along the cross-section of anelectrode compared to the same along its length duringEDM of aluminum and mild steel using copper and brasselectrodes.
Nội dung trích xuất từ tài liệu:
Electrode wear and material removal rate during EDM of aluminum and mild steel using copper and brass electrodesInt J Adv Manuf Technol (2008) 39:482–487DOI 10.1007/s00170-007-1241-3ORIGINAL ARTICLEElectrode wear and material removal rate during EDMof aluminum and mild steel using copperand brass electrodesA. A. KhanReceived: 19 June 2007 / Revised: 12 September 2007 / Accepted: 12 September 2007 / Published online: 5 October 2007# Springer-Verlag London Limited 2007Abstract In the present study an analysis has been done toevaluate the electrode wear along the cross-section of anelectrode compared to the same along its length duringEDM of aluminum and mild steel using copper and brasselectrodes. In an overall performance comparison of copperand brass electrodes, we found that electrode wear increaseswith an increase in both current and voltage, but wear alongthe cross-section of the electrode is more compared to thesame along its length. This is due to easier heat transferalong the length compared to the same along the crosssection of the electrode. It was also found that the wearratio increases with an increase in current. That means,though a higher current causes more removal of workmaterial and the electrode, comparatively more material isremoved from the electrode. The highest wear ratio wasfound during machining of steel using a brass electrode.The low thermal conductivity of brass electrodes causesless heat loss, and its low melting point results in fastmelting of the electrode material. At the same time, lowthermal conductivity of steel results in poor heat absorption,and its high melting temperature causes poor removal ofwork material. These factors result in the highest wear ratioduring machining of steel using a brass electrode. Thehighest material removal rate was observed during machining of aluminum using brass electrodes. Comparatively lowthermal conductivity of brass as an electrode material doesnot allow the absorption of much heat energy, and most ofthe heat is utilized in the removal of material fromA. A. Khan (*)Department of Manufacturing and Materials Engineering,International Islamic University Malaysia,P.O. Box 10, 50728 Kuala Lumpur, Malaysiae-mail: aakhan0912@yahoo.comaluminum workpiece at a low melting point. But duringmachining of steel using copper electrodes, a comparativelysmaller quantity of heat is absorbed by the work materialdue to its low thermal conductivity. As a result materialremoval rate becomes very low.Keywords EDM . Electrode wear . Wear ratio .Material removal rateNomenclatureEDM Electrical discharge machiningEWElectrode wearWRWear ratioIpPeak currentVgGap voltageMRR Material removal rateRaSurface roughnesstIPulse on timetoPulse off timeηDuty cycleKThermal conductivityTmMelting temperature1 IntroductionDifferent non-traditional machining techniques are increasingly employed in manufacturing of complex machinecomponents. Among the non-traditional methods of machining processes, electrical discharge machining (EDM)has drawn a great deal of researchers’ attention because ofits broad industrial applications [1]. EDM is widely used inmachining high strength steel, tungsten carbide andInt J Adv Manuf Technol (2008) 39:482–487483Table 1 Major properties of electrode materialsElectrodematerialsThermalconductivity(W/m-°K)Meltingpoint (°C)Electricalresistivity(ohm-cm)Specificheatcapacity(J/g-°C)CopperBrass3911591,0839901.694.70.3850.38Table 2 Chemical composition of the work materialsWorkmaterialsChemical compositionAluminumAl: 99.9%, Cu:0.05%, Fe:0.4%, Mg:0.05%,Mn:0.05%, Si:0.25%, Zn:0.05%C: 0.14%–0.2%, Fe: 98.81–99.26%, Mn: 0.6%–0.9%,P: 0.04%, S: 0.05%Mild steelhardened steel [2]. In this process material is removed bycontrolled erosion through a series of electric sparksbetween the tool (electrode) and the workpiece [3]. Thethermal energy of the sparks leads to intense heatconditions on the workpiece causing melting and vaporizing of workpiece material [4]. Due to the high temperatureof the sparks, not only work material is melted andvaporized, but the electrode material is also melted andvaporized, which is known as electrode wear (EW). TheEW process is quite similar to the material removalmechanism as the electrode and the workpiece areconsidered as a set of electrodes in EDM [5]. Due to thiswear, electrodes lose their dimensions resulting in inaccuracy of the cavities formed [6]. During EDM, the mainoutput parameters are the material removal rate (MRR),wear ratio (WR), EW, and job surface finish Ra [7, 8]. It isdesirable to obtain the maximum MRR with minimal EW.Common electrode materials are graphite, brass, copper andcopper-tungsten alloys [9, 10]. Efforts have been done tominimize EW. A metal matrix composite (ZrB2-Cu) wasdeveloped adding different amount of Cu to get an ...