Influence of open voltage and servo voltage during Wire-EDM of silicon carbides

• Published in: Procedia CIRP Vol. 95; pp. 285 - 289
• Main Authors: Singh, Meinam Annebushan, Joshi, Kamlesh, Hanzel, Ondrej, Singh, Ramesh, Sajgalik, Pavol, Marla, Deepak
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 2020
• Subjects: kerf width; servo voltage; SiC; surface characteristics; WEDM; servo voltage; kerf width; SiC; surface characteristics; WEDM
• ISSN: 2212-8271; 2212-8271
• DOI: 10.1016/j.procir.2020.02.305

The high cost of silicon carbide and its associated difficulties in machining due to high hardness have long been a major hindrance towards successful applications in various industries, ranging from marine to aerospace sectors. This imparts a need to identify a suitable machining process that can machine silicon carbides with ease and at the same time generate complicated profiles. Therefore, the present work is an effort to identify the possibility of machining silicon carbides with wire electrical discharge machining process. In the current work, the silicon carbides being fabricated by rapid hot-pressing technique led to in-situ graphene formation. This graphene particles, in turn, aid the electrical discharge machining process by imparting a higher electron transfer rate through the workpiece. The influence of open voltage and servo voltage on the overall machinability were thoroughly investigated with machining rate, kerf width and surface roughness as the output characteristics. The variation in the intensity of discharge energy with open voltages had a direct influence on the formation of discharge crater which in turn, affected the overall output characteristics. This led to a gradual increase in the machining rate and the associated surface roughness with an increase in the open voltage. On the other hand, the increase in the servo voltage from 25 V to 39 V led to an initial increase in the machining rate which again decreases when the servo voltage further increases to 51 V. This variation in the machining rate was mainly due to the varying concentration of discharge, open and arcing pulses with varying servo voltage, with arcing pulses more dominant in lower servo voltage and open pulses in larger servo voltage. A minimum kerf width in the range of 170 µm was obtained in the present study with a wire tool of diameter 150 µm when the servo voltage was maintained at 25 V. Further, the kerf width was observed to increase with an increase in the servo voltage throughout the considered range. This is mainly due to the higher discharge concentration in the transverse direction as compared to the machining direction with an increase in the servo voltages. Moreover, a rougher machined surface with high debris concentration was observed when machined with lower servo voltages for all the considered open voltages. This behavior is mainly attributed by the high arcing phenomenon and ineffective removal of the eroded debris across the small inter-electrode gap by the dielectric fluid.