A novel method to reduce dross in laser beam cutting of Ti-6Al-4 V alloy sheet

Abstract

Abstract During the laser cutting of Ti-6Al-4 V sheets, different dross heights are obtained for different thicknesses of the sheet. The maximum value of normalized dross height (= dross height per unit thickness of laser cut sheet), calculated from reported data, was 0.155. In the present investigation, the maximum normalized dross height, obtained by use of an additional nozzle (secondary gas-flow nozzle) and by parametric optimization through Teaching–Learning-based algorithm, was 0.053. The present study shows that the conventional set-up for laser beam cutting of Ti-6Al-4 V alloy, i.e., cutting with co-axial assist gas flow, may not be able to reduce the dross height completely. However, it was observed that the use of a secondary gas-flow nozzle, in tandem with the co-axial nozzle, i.e., a modified set-up, was able to reduce the dross height due to the shearing action of the argon jet flow directed at the dross. The thrust force of the argon jet acting on the dross has been estimated in the present study using analytical equations and was found to be 76.17 gf. When the longitudinal profile of cut surface was mapped using a laser displacement sensor, it was observed that the roughness of the cut surface obtained using the modified set-up was found to be less (i.e., approximately half) as compared to that obtained in case of the conventional set-up. In addition to the dross height, straightness of the cut sample (kerf wall convexity) was also taken into account for optimization.