Prezentation on the LiM 2017 conference

04.08.2017

The Laser in Manufacturing (LiM) 2017 conference took place in Munich, Germany from June 26 to June 29 2017. Our researchers Martin Kučera and Denys Moskal participate in the conference and presented contributions. Martin Kučera: Time-Resolved Temperature Measurement during Laser Marking of Stainless Steel. Denys Moskal: Scanning strategy of high speed shifted laser surface texturing.

Abstract:
Time-Resolved Temperature Measurement during Laser Marking of Stainless Steels
M. Kučeraa, J. Martana,
a New Technologies Research Centre (NTC), University of West Bohemia, Univerzitni 8, 306 14 Pilsen, Czech Republic

Laser marking is a well-established technology in industry; however there are still issues where the marking process itself needs to be investigated. The surface microstructure and the phase composition can be changed by the laser treatment. For this reason we present a study of temperatures reached by different parameters of laser marking and their correlation with resulted microstructure and phase composition. The marking was done using nanosecond pulsed fibre laser with variable pulse duration (from 9 to 200 ns), repetition frequency and pulse energy. Similar marking was obtained by different parameters but different phase composition and it correlates well with maximum temperatures reached in the laser spot, which varied from less than 1100°C to more than 1800°C. From the results it can be concluded that combination of longer pulse duration and higher repetition rate are the most suitable parameters for achieving the stainless steel marking without surface melting.

Keywords: time resolved temperature measurement; laser; marking; stainless steel

Abstract:
Scanning strategy of high speed shifted laser surface texturing
D. Moskala, J. Martana, M. Kučeraa
a New Technologies Research Centre (NTC), University of West Bohemia, Univerzitni 8, 306 14 Pilsen, Czech Republic

Laser Surface Texturing (LST) is one of the perspective ways for creating of functional surfaces: low frictional, hydrophobic or hydrophilic, photonic structures, thermal spray substrates and so on. There are several methods for laser surface texturing of large areas, but they have some physical limitations, such as heat accumulation, plasma shielding and achieving high precision at fast laser beam scanning speed. In this paper a new method called shifted Laser Surface Texturing (sLST) is presented. This sLST method is able to overcome mentioned physical limitations. The sLST method is based on formation of large array of microobjects by collecting them from short/ultrashort laser pulses, which are distant in time and processing plane. It is achieved by application of a series of laser scanning of linear raster which contains a lot of single pulses. Each single pulse in one raster belongs to different object from the textured area. The linear raster is shifted by small distance between each repetition. The high precision of the shape and position of every textured object (<2 μm) is achieved by control of laser spots position electronically by using of constant repetition frequency of laser pulse generation.
In this way the mirrors movement has no control of object position directly, but supply only continuous movement of the laser spot position. The method of sLST has great potential for polygonal, resonant or hybrid scanning system, where laser beam scanning speed reached up to 1000 m/s and high precision of microobjects formation becomes difficult task. In this paper there is described the principle of the method along with its applications on functional surfaces. In discussion there are presented physical and technical parameters of high speed sLST in comparison with classical texturing methods.

Keywords: Laser surface texturing, scanning strategy, high speed, functional surfaces