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: from 2021 to 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 451385285

• Final Report Year: 2025

Final Report Abstract

The findings from the investigations on near-process characterization of laser-chemical machining can be summarized as follows:  The indirect fluorescence-based measurement technique for detecting the workpiece surface was successfully implemented in-situ using a pulsed laser source. It was able to capture the topography of laser-chemically generated structures inside the etching cell and under flowing fluid conditions, despite the presence of moving air bubbles. However, systematic measurement deviations occurred at the edges of the removed cavities, requiring a revision of the signal model.  Using the same optical path for geometry measurement, it was validated that the temperature of the flowing electrolyte solution can be accurately measured via fluorescence lifetime within the LCM environment, with a random error of 1°C and a systematic error of 1.4°C. - The spatial frequency of the generated cavity corresponds to the spatial frequency of the laser power modulation up to a maximum threshold frequency. The removal depth remains constant once the set laser power frequency exceeds this threshold. Laser chemical machining with modulated laser power at a frequency below the threshold enables the generation of complex 3D surface structures, whose characteristics can be modified by adjusting the frequency and phase angle. These structures can have an anisotropic wetting behavior. - Increasing the electrolyte viscosity reduces the laser-chemical process window and, consequently, the upper limits of the material removal rates. At high electrolyte viscosities, a semicircular cavity geometry was identified, indicating a shielding effect caused by gas bubbles.

Publications

• Influence of electrolyte concentration on laser chemical machining. Proceedings of the 12th Laser Applications Forum (LAF’22), Bremen, 23.-24.11.2022.In: Strahltechnik Band 76, eds. T. Seefeld, T. Radel, T. Mattulat, BIAS Verlag Bremen, S. 32-35, 2022
  M. Simons & T. Radel
  
• Laser chemical machining with additive-increased electrolyte viscosity. Proceedings of the 23rd International Symposium on Laser Precision Microfabrication (LPM 2022), Dresden, 7.-10.6.2022
  M. Simons & T. Radel
  
• Near-process indirect surface characterization of laser-chemically produced removal contours. EPJ Web of Conferences, 266, 10011.
  Mikulewitsch, Merlin; Stöbener, Dirk & Fischer, Andreas
  
• Prozessnahe indirekte Oberflächencharakterisierung von laserchemisch gefertigten Abtragskonturen. tm - Technisches Messen, 89(s1), 37-42.
  Mikulewitsch, Merlin; Stöbener, Dirk & Fischer, Andreas
  
• Fluorescence-based measurements of material removal and process temperature during laser chemical machining. 23th International Conference & Exhibition of the European Society for Precision Engineering and Nanotechnology (euspen), Copenhagen, Denmark, 12.-16.6.2023, pp. 389-390
  D. Stöbener, M. Mikulewitsch & A. Fischer
  
• P30 - Near-process Indirect Surface Geometry and Temperature Measurement for Laser Chemical Machining (LCM). Poster, 338-339. AMA Service GmbH, Von-Münchhausen-Str. 49, 31515 Wunstorf, Germany.
  Mikulewitsch, M.; Bouraoui, Y.; Radel, T.; Stöbener, D. & Fischer, A.
  
• Laser power modulation between disturbed and undisturbed material removal regime in laser chemical processing. The International Journal of Advanced Manufacturing Technology, 135(7-8), 3983-3989.
  Lu, Yang; Bouraoui, Yasmine; Niehaves, Claudia; Fischer, Andreas & Radel, Tim
  
• Material removal in laser chemical processing with modulated laser power. Journal of Laser Applications, 36(1).
  Bouraoui, Yasmine; Rathmann, Lewin; Niehaves, Claudia; Mikulewitsch, Merlin; Fischer, Andreas & Radel, Tim
  
• Complex 3D surface structuring by means of laser chemical machining with modulated laser power. Journal of Laser Applications, 37(1).
  Bouraoui, Yasmine; Rathmann, Lewin; Lu, Yang; Niehaves, Claudia; Fischer, Andreas & Radel, Tim
  
• Fluorescence-Based Measurement of Workpiece Geometry and Temperature in Laser Chemical Machining. Nanomanufacturing and Metrology, 8(1).
  Niehaves, Claudia; Tausendfreund, Andreas; Bouraoui, Yasmine; Lu, Yang; Radel, Tim & Fischer, Andreas