The influence patterns of nozzle design and technological parameters of gas-assisted laser cutting on the stagnant pressure of assisting gas
Abstract
The paper proposes and implements a methodology for experimental measuring of the dimensions of the action zone and the amount of pressure, which ensures the removal of the liquid phase during gas laser cutting and is created by the flow of the assist gas on the surface of the part. During the research, based on a serial LTS-PRO-6000-1530-LD machine of Aramis company, serial one-channel and two-channel nozzles of Thermacut company with an outlet diameter of 1.5 mm were installed in the optical head of the machine. In the experiments, air with the gauge pressure at the nozzle inlet of 0.5 MPa and 1 MPa was used as the assist gas. The regularities of the influence of the nozzle design, the gap between the nozzle and the part, and the gauge pressure at the nozzle inlet on changes in the diameter of the supersonic jet of the assist gas and the amount of pressure it creates exerting the surface of the part under technological conditions of gas laser cutting have been established. The obtained array of experimental data has shown that the traditional approach to the use of the existing range of serial nozzles makes it problematic to effectively design gas laser cutting processes with maximum productivity and reproducibility of the cut quality. This is related to complex phenomena in the supersonic jet, which determine the high sensitivity of the pressure value on the part's surface to changes in the nozzle geometry and process technological parameters. As a result, there is no understanding of what kind of pressure is created by the jet of the assist gas in the cutting zone under certain technological parameters of the process. The methodology proposed in this paper makes it relatively easy to create "passports" for the nozzles that each machine is equipped with. Thus, it becomes possible to take into account the real value of the assisting pressure field in the cutting zone when designing a specific technological process. As a result, productive high-quality cutting is more reliably ensured on a given technological installation and the level of process reproducibility is improved. Experimental verification has demonstrated a fairly good correlation between the local stagnant pressure of the assist gas jet and the maximum laser cutting speed and the cut quality
Keywords
gas laser cutting; assist gas; nozzle; supersonic jet; fiber optic laser
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