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

Figure 5(d) shows the phenomena <strong>of</strong> EDM drilling on shallow and deep holes (Yu et al. 2009).3.4 Analysis <strong>of</strong> Duty Factor and On­TimeThe duty factor, which means the ratio between pulse duration and pulse cycle time exertsan important role on the performance <strong>of</strong> EDM as shown in Figure6 (a). In this experiment, weconsideration <strong>of</strong> each parameters by varying duty factor 10, 15, 20, 35, 45, 60, 75, 90 %, ontime 10, 30, 50, 90 μs, and fixing parameters <strong>of</strong> current at 9 A, servo rate at 2 mm/sec, and waterpressure at 40 kg/cm 2 , respectively. As can be seen in Figure6 (b-c), the results were found thatthe each on-time was suitable for only a specific duty factor. MRR increases with increasing <strong>of</strong>duty factor <strong>of</strong> each on-time. However, increasing <strong>of</strong> duty factor leads to decreasing <strong>of</strong> EWR andtaper. Moreover, if increasing <strong>of</strong> on-time less than 30 µs, it still affects to MRR increases. At 75% <strong>of</strong> duty factor for on-time 30 and 50 µs, they give same values <strong>of</strong> MRR. However, theseparameters results in low EWR and taper.(a) Effect <strong>of</strong> servo rate with MRR(b) Effect <strong>of</strong> servo rate with EWR(c) Effect <strong>of</strong> servo rate with taper(d) Edge wear influence to high servo rateFigure 5: Variations <strong>of</strong> servo rate with meso-hole results.*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.pdf477