Melt dynamics in remote laser material processing

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Remote Fusion Cutting (RFC) or Front Pressure Cutting has high potential for various industrial applications compared to conventional gas-assisted cutting processes due to its resource efficiency and its more flexible feasibility in industry. Stable process layout, however, is crucial to make use of this potential. Currently, the process behaves often instable regarding changes of parameters and the process understanding needed to explain or resolve this behavior is lacking.Therefore, in the proposed project the process understanding necessary for stable process layout will be developed. In order to understand the process comprehensively, not only the process of RFC, but also the borders of its process window, i. e. the transitions to the welding regime will be investigated. In the first step, the analysis algorithms necessary for the experiments and the already developed simulation model will be adapted to the process, improved and verified. Then, the process will be examined experimentally and simulatively to analyze and understand the mechanisms of material removal. More specifically, topology, shape and size of the interaction zone will be investigated videgraphically and simulatively and it will be clarified how these characteristics influence melt flow and material removal in RFC. Furthermore, it will be analyzed, primarily simulatively, how evaporation and the associated vapor pressure influence melt flow and how surface tension, vapor pressure and hydrodynamic pressure behave in RFC and in the transitions to welding. Since RFC reacts to changes of track geometries way more sensitively than welding and this often leads to loss of cut, it will be investigated videographically and simulatively how the track geometry influences the shape of the interaction zone, the melt flow and the material removal. Additionally, it will be investigated how and how much the laser power influences the maximum feed rate and the quality of the cut edges.Due to the verified fluiddynamic process model used in the project, in case of differences between experiment and simulation in certain areas of the process, the cause of the differences can be limited to an error in the implemented model or to false material properties. Therefore, by comparisons with experiments and iterative changes of the model process understanding can be built. This process understanding will be used to investigate possibilities to control and stabilize the process, e. g. by modulation of the laser power or modifications of the intensity distributions using phase masks. This knowledge will be condensed in user rules to contribute to the industrial applicability of RFC.