Process-oriented characterization of temperature field and ablation changes during laser chemical processing

• Applicants: Professor Dr.-Ing. Andreas Fischer; Dr.-Ing. Tim Radel, since 10/2021
• Subject Area: Joining and Separation Technology
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 451385285

Laser Chemical Machining (LCM), a further development of the electrochemical process, is based on laser-induced anodic material dissolution at the interface between the workpiece surface and electrolyte. It is characterized by its flexibility and variety, its gentle and residue-free removal, as well as its low thermal load on the workpiece. Compared to other micro manufacturing processes, e.g. micro milling, it achieves a higher removal quality with regard to shape accuracy at acute edge angles and small edge radii. However, the removal rate is lower with LCM than with comparable processes, especially because disturbance effects such as electrolytic boiling greatly limit the laser chemical process window and the associated removal rate. Up to now, surface temperature and removal geometry could not be measured during production using conventional measuring methods. For this reason, it is currently not possible to detect any departure from the process window during production, nor is it possible to model the process to predict the optimum process and machining parameters or to adapt it to other materials.The aim of this project is to increase the process understanding of laser chemical machining and to model the LCM process so that a higher removal rate can be achieved while increas-ing the removal quality. In order to reduce the formation of boiling bubbles and removal dis-turbances during laser chemical machining, a variation of the electrolyte viscosity and a tem-poral modulation of the laser radiation is considered. Since currently only a simplified temper-ature model exists, which does not consider viscosity and modulation, an extension of the model toward these parameters is intended. In addition, the boiling bubbles and the material removal are explicitly modelled for the first time, whereby the influence of viscosity and mod-ulation is also taken into account. The formulation of the temperature, bubble and removal models will be carried out with the help of process-oriented measurements of the workpiece surface temperature, the bubbles and the workpiece geometry during the machining in the removal zone. Due to the complexity of laser chemical processing with regard to fluid-, ther-mo- and chemodynamic mechanisms, a suitable process-oriented measurement technique is essential for the process understanding and validation of the models. For this reason, fluores-cence-based measurement methods adapted to the near-process application in the LCM pro-cess will be developed in this project and validated for near-process measurement during la-ser chemical removal. Based on the metrologically supported modelling of the LCM process and the resulting increased understanding of the process, the process window can finally be adapted to other materials and a precise prediction of the removal quality and removal rate achievable depending on the process parameters can be made.

• DFG Programme: Research Grants
• Ehemaliger Antragsteller: Professor Dr.-Ing. Frank Vollertsen, until 10/2021