Influence of Gap Air Flushing on Plasma Channel and Crater Geometry in Single Blasting Erosion Arc Discharge

Abstract

Blasting erosion arc machining (BEAM) is a promising method for machining difficult-to-cut materials. In BEAM, high pressure inner flushing is implemented to increase machining efficiency in terms of material removal. However, effects of flushing on plasma arc evolution and material removal mechanism in BEAM are still unknown. In this research, air was blown to a single arc discharge as an alternative to water based dielectric in BEAM process. Using an ultra-fast four channel ICCD camera, influence of cross directional air jet on plasma channel development and crater formation was studied. Observation showed that plasma arc channel is obviously disturbed in presence of high speed air flushing. In other word, arc plasma column moves along the air flushing direction. Consequently, crater geometry and electrode wear will highly be influenced by air flushing in the gap. High speed air flushing increases molten metal flushed away from molten pool compare to the stationary air medium condition. This indicates that there is a decrease in recast layer on machined surface and as a result, volume of removed material will increase. Moreover, using high speed air flushing in single arc discharge decreases tool electrode wear volume significantly. Finally, based on the experimental results and theoretical analysis, high speed air flushing proves aerodynamic arc disturbing phenomenon during single arc discharge which is a potential evident to hydrodynamic arc breaking mechanism in BEAM.