Helical drilling of three-dimensional conical converging-diverging nozzle in steel using ultrashort laser pulses
Abstract
Three-dimensional conical converging-diverging nozzle typically a de Laval nozzle can be used for micropropulsion of microsatellites. The profile control, surface roughness and symmetry of the nozzle are key parameters to determine its performance. In this paper, we focus on the fabrication of a three-dimensional conical converging-diverging nozzle using helical drilling optics and ultrashort laser pulses. The helical optics makes it possible to dynamically control the profile of a hole by adapting the helical path during drilling process. An opening angle up to 18.6° on the converging part and 6.6° on the diverging part are achievable in 1 mm thick stainless steel by means of classic helical drilling. By introducing a dynamic helical process, the opening angle of converging part with straight profile can be extended to more than 90°. Moreover, the employment of an ultrashort pulsed laser has contributed to a high quality surface on the hole-wall having an average roughness less than 0.4 µm.
