Analyzing the Electromagnetic Radiations Emitted during a Laser-based Surface Pre-Treatment Process for Aluminium using Diode Sensors as an Approach for High-Resolution Online Monitoring

To obtain a good adhesive bonding quality between aluminum parts it is necessary to remove contaminations and to define the chemical composition and topographic status of the corresponding surfaces. Hence, a surface pre-treatment is needed which simultaneously guarantees environmental concerns, industrial safety, efficiency, and reproducibility of surface quality. For this purpose, nano-second-pulsed laser processing is suitable, especially concerning the integration of the surface pre-treatment process in the main processing line of the body shop. To fulfill the technical require-ments and to minimize the production of scrap parts, an online monitoring and control system of the pre-treatment process is essential. In this study, electromagnetic radiations, which are generated by the laser-based pre-treatment process, are detected online using photodiodes. The recorded signals are examined in terms of the correlation between their dynamics, the resulting surface state (quality of the pre-treatment) and the executed process/system parameters. Conventional offline methods for analyzing the chemical composition and topography of surfaces are applied to validate the results. It was found that the obtained information can be used to define a process window and enable the de-velopment of a proper process monitoring and control system for the laser-based pre-treatment pro-cess for industrial use.