In LAMpAS, a high-power ps laser source has been developed. The goal parameters were agreed by the LAMpAS partners. In order to achieve this goal, TRUMPF has developed an industrial multipass amplifier based on the thin-disk technology. A demonstrator laser was designed and manufactured, tested in a laboratory setup and delivered for integration into an industrial material processing machine. In a laboratory setup, over 2 kW of output power were achieved with sufficient beam quality of M² < 1.6. For delivery, the power of the laser source was decreased to 1 kW.
An interference-based optic in combination with a polygon scanner was for the first time ever constructed, which addressed several challenges regarding the needed spatial period and feature size, spot size, scan field as well as material throughput. After the evaluation of different designs, a unique Polygon-DLIP module with a very innovative approach has been developed. Due to the high laser power used, a spatial cooling unit had to be implemented. Much effort was focused in the reduction of system size and weight for addressing the specifications of machine and its location.
For having a perfect evaluation of the structuring process in real-time, two in-line monitoring concepts were engineered. The sub-modules were based on a high speed MWIR sensor as well as a the Fast-Fourier Transform system. The operation of the MWIR sensor unit was demonstrated with a ps pulsed laser treatment of stainless steel samples. By means of the infrared camera it was possible to detect in-line instabilities affecting the surface quality of the treated areas. In the same way, the feasibility of the FFT system was evaluated, showing a possible classification of different surface conditions. Other tests were performed for other pulse durations, demonstrating the possibility of further commercialization of the system for other laser-based manufacturing processes.
To understand the interaction of materials with the laser radiation, simulation models were developed and thus supporting the process development. The models permitted to calculate the ablation depth as well as temperature distributions, which was validated with experimental results. Both software-tools are based on analytical equations and allow short calculation times and good scalability. The most imported material properties affecting the structuring process are heat conductivity, density and heat capacity. With regard to geometry, the thickness and size of the sheet metal must be considered. Finally, a first process test on the system at LASEA with calculated parameters was successfully performed. The experimental findings of the final experiments with preheating were incorporated. In addition, a considerable acceleration of the simulation made it possible to simulate the final processing size on a normal PC.
All developed components were integrated into a system, obtaining a viable solution for functional texturing of large surfaces at high throughput, taking full advantage of the increase in average power provided by ultra-short pulses laser sources. This has required a close cooperation with the rest of the partners in the definition of the specifications and interfaces as well as the installation and evaluation of the different sub-elements/modules. All sub-systems demonstrated to operate correctly, allowing for the first time to process metallic parts using a new concept based on DLIP-polygon processing. All partners are strongly committed to finalize and commercialize the DLIP-Polygon LAMpAS system, due to the outstanding capabilities that it offers for large area surface functionalization.
Finally, different characterization methods have been developed for evaluating target surface properties to be incorporated into different products. For instance, additional testing methodology has been developed to study the performance of the anti-fingerprint, easy to clean and decoration properties. Furthermore, a methodology to evaluate anti-bacterial properties has been also conceived. The process-related requirements have been defined, taking into account not only the processing time, but also the quality requirements and connectivity to the production lines. Accordingly, samples produced during the project have been tested using the defined procedures, providing a reliable evaluation of the status of the technology as a basis for future developments.
