A Study of Hole Drilling on Stainless Steel AISI 431 by EDM Using ...

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insulating materials regardless <strong>of</strong> material hardness, (Muttamara et al, 2009&2010). However,the important type <strong>of</strong> defect from hole drilling during EDM process is hole taper and holeaccuracy (Ali et al.2009). Therefore, in order to improve hole quality, Sharma et al.(2002) andBilgi et al.(2007) investigated optimum values <strong>of</strong> the process parameters experimentally suchas voltage, feed rate, pulse on time, duty cycle, and the length <strong>of</strong> un–insulate tool.Figure 1: Characteristic <strong>of</strong> taper on EDMIn the EDM sparking hole drilling process, the viscous resistance in the narrow dischargegap causes difficulty in the removal <strong>of</strong> debris and bubbles from the working area, abnormaldischarges are occurred and resulting in extensive electrode wear (Yu et al. 2009). Moreover,the debris moved by pressure flow <strong>of</strong> dielectric fluid make taper on the workpiece. The holetaper <strong>of</strong> workpiece from EDM process, which as shows in Figure 1, can be calculated byequation (1). tan(1)WhereD is hole entrances,d is hole exits, andL is hole length.This research focuses on influence <strong>of</strong> machining variables affecting material removal rate(MRR), electrode wear rate (EWR), and taper on martensitic stainless steel AISI 431.2 Experimental ProcedureThe experiments were carried out on 35 mm <strong>of</strong> hole depth <strong>of</strong> martensitic stainless steelAISI 431with ZNC-EDM model JM325DZ manufactured by Joemars company, as shown inFigure2(a). The EDM was carried out on meso-scale machining with a brass tube electrode as472 Pichai Janmanee, and Apiwat Muttamara
outside diameter <strong>of</strong> 1 mm, inner hole diameter <strong>of</strong> 0.3 mm for flushing by dielectric fluid toremove wear debris and heat ventilation size as shown in Figure 2(b). Principle <strong>of</strong> tubeelectrode drilling is shown in Figure 2(c). The experiments were carried out in the de-ionised,because <strong>of</strong> the advantage <strong>of</strong> material removal rate (Diver et al. 2004). The chemicalcompositions and essential physical properties are shown in Table 1 and Table 2, respectively.Table 3 shows the physical properties <strong>of</strong> an electrode. The experiment conditions arecontained in Table 4.(a) EDM super drill model JM325DZ(b) Brass (Cu-Zn40) tube electrode(c) ZNC-EDM drilling processFigure 2: Experimental EDM .*Corresponding author (A. Muttamara). Tel/Fax: +66-2-5643001 Ext.3189. E-mail addresses:mapiwat@engr.tu.ac.th. 2011. International Transaction Journal <strong>of</strong> Engineering,Management, & Applied Sciences & Technologies. Volume 2 No.4. ISSN 2228-9860.eISSN 1906-9642. Online Available at http://TuEngr.com/V02/471-481.pdf473
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A Study of Hole Drilling on Stainless Steel AISI 431 by EDM Using ...

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