On Friday, April 17, 2020 at 12:00, Marko Pogačar defended his doctoral dissertation entitled:
Adaptive laser surface treatment for absolute position marks on steel measuring rod
Mentor: izr. prof. dr. Matija Jezeršek
comentor: prof. dr. Janez Možina
In this work we were focused on research and development of absolute position marks on steel measuring rod which can be used for in-axis positioning measurements where durability and high precision are needed. High speed laser power regulation was made for repeatable laser-based micro-inscription. Two different regimes for laser surface treatment were compared: a surface heating and a deep penetration heating. The first regime is the same as conductive heating and the second is similar to the process of keyhole welding. The experimental results show that both processes can be effectively stabilized by means of controlling the width and depth of the microstructure transformation cross-section, as they are able to compensate for external disturbances, such as higher roughness, and the gradual accumulation of heat. We demonstrated a method to increase the accuracy of location of magnetic micro-inscription by using an innovative pre-position signs which were made and detected by the same laser source. The impact of shrinkage due-to microstructure transformation was evaluated and taken into account. In this way we were able to compensate the thermal expansion and guarantee the absolute location of position marks under the accuracy of 10 µm.