Presentation on the International Symposium LPM 2018
The 19th International Symposium Laser Precision Microfabricationin 2018 - took place in Edinburgh from June 25 to June 28 2018. Our researcher Denys Moskal participated in the symposium and presented contribution: Shifted laser surface texturing (sLST) in burst regime.
Shifted laser surface texturing (sLST) in burst regimeD. Moskal, J. Martan, M. Kucera
University of West Bohemia,
Univerzitni str., 8/2732, 301 00 Plzen, Czech Republic
Corresponding author: firstname.lastname@example.org
Laser scanning speed and high precision are two opposite parameters for effective laser surface texturing (LST) [1, 2]. Application of burst mode helps to increase the processing effectivity and speed, but precision control of laser pulses arriving becomes difficult task for micro-texturing. In this work, one possible solution for this dilemma is presented: scanning strategy named shifted laser surface texturing (sLST) in burst regime [1, 3, 4]. This burst sLST represents an alternative method, where inertia of galvanoscan mirrors becomes useful factor at higher speeds. Physical principles of laser bursts interaction with material surface and resulting subsurface thermal-stress fields were discussed. Heat accumulation was calculated from semi-planar model of temperature distribution from laser spots in line of the burst [5, 6]. Residual subsurface temperature and pressure was called positive heat accumulation in the case of minimal output roughness of laser scanned surfaces. Experimental application of burst sLST was performed by picosecond laser with two different galvanoscan systems. Results were evaluated by shape analysis of objects detected on contrast images of laser processed stainless steel surfaces. Deviation in sLST precision was determined from larger and smaller diameter of detected microobjects on surface with LabIR coating  (Figure 1). Depth map of laser textured surface was compared with goal profile and positive heat accumulation distribution. Principal limitations of burst sLST and future possibilities for increasing scanning speed were discussed.
(c)Figure 1: Application of sLST in burst regime: (a) Detection of processed surface objects and shape analysis with high emissivity LabIR painting. (b) Depth map of stainless steel surface after 20 times sLST in burst mode and (c) corresponding heat accumulation in central point of the textured objects.
References D. Moskal, M. Kučera, E. Smazalová, S. Houdková, and R. Kromer Application of shifted laser surface texturing, in METAL 2015 - 24th International Conference on Metallurgy and Materials, Conference Proceedings, 2015.
 Š. Houdková, P. Šperka, M. Repka, J. Martan, and D. Moskal (2017) Shifted laser surface texturing for bearings applications, J. Phys. Conf. Ser., vol. 843, no. 1, 2017.
 D. Moskal, J. Martan, and M. Kučera (2017) Scanning strategy of high speed shifted laser surface texturing, no. August, 2017.
 T. Kramer, Y. Zhang, S. Remund, B. Jaeggi, and A. Michalowski (2017) Increasing the Specific Removal Rate for Ultra Short Pulsed Laser-Micromachining by Using Pulse Bursts, vol. 12, no. 2, pp. 107–114, 2017.
 R. Weber et al. (2014) Heat accumulation during pulsed laser materials processing, Opt. Express, vol. 22, no. 9, pp. 11312–11324, 2014.
 D. Moskal, J. Martan, Š. Houdkova, and R. Kromer Laser surface cleaning of AM1 superalloy, in 9th International Conference on Photonic Technologies - LANE 2016, submitted, 2016.
 LabIR. [Online]. Available: http://paints.labir.eu/paint/thermographic-paint-for-standard-applications.