Effect of Polarity Variation in Maglev EDM Using Nitrogen-Rich Powder-Mixed Dielectric

Electrode polarity in electro-discharge machining (EDM) is vital in distributing discharge energy to the workpiece and the tool. Currently, powder-mixed dielectric application in EDM is an emerging field to improve machining efficiency and achieve better surface quality and surface modification. The current investigation implements straight and reverse polarity for machining titanium grade-5 alloy using urea-mixed deionized water dielectric in Maglev EDM. The machining operation has been performed on a titanium grade-5 alloy workpiece (15 mm × 15 mm × 3 mm) using a cylindrical mild steel tool (ø = 3.3 mm). The parametric conditions for the investigation were discharge voltage (20 V) and discharge current (160 mA) for both straight and reverse polarity. The dielectric fluid is prepared using urea mixed with deionized water at a concentration of 75 g/l. During straight polarity, an average MRR of 148.5 µg/min and average TWR of 30.5 µg/min were achieved by using the powder-mixed dielectric. In reverse polarity condition, an average MRR of 69.5 µg/min and TWR of 97.5 µg/min were achieved using the same dielectric concentration. Maximum erosion was observed at the anode for both polarity conditions. Additionally, the surface characteristics of the machined workpiece have been examined using SEM micrographs and EDX reports.