Now showing 1 - 10 of 11
  • Publication
    Investigation of Surface Structure in the Laser Marking Process as a Function of Speed and Raster Step
    In this research, an experiment was conducted to change the technological properties of the surface by laser marking. The influence of the speed v of 50 mm/s, 75 mm/s and 100 mm/s and the raster step Δx from 20 µm to 80 µm at a constant average power P = 19.2 W and pulse duration τ = 4 ns was investigated. These parameters during the laser marking of AISI 304L steel have a significant change in microhardness and surface roughness. High hardness was found to be achieved at higher powers and small pitch. Analysis of the results showed that as the raster step increases, the roughness of the marked sample decreases. The effect of linear energy density and overlap factor on the process was also investigated. The microhardness of the machined surfaces increases with an increase in the linear energy density and the overlap coefficient, in the first case the dependence is almost linear, and in the second - nonlinear. Varying the marking speed and raster pitch in laser surface texturing of AISI 304L steel has a significant effect on the surface hardness and roughness, changing HV from 260 HV to 766.5 HV and Ra from 1.75 µm to 4.3 µm, respectively, which are the subject of the present analysis. research.
  • Publication
    Investigation of the Change in Roughness and Microhardness during Laser Surface Texturing of Copper Samples by Changing the Process Parameters
    (2023)
    Risham Singh
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    Emil Yankov
    ;
    Nikolay Angelov
    The aim of this research is to achieve a high-quality and long-lasting laser marking of ammunition, which is of interest to the defense industry. The study is about the effects of speed, raster pitch and power on the roughness and microhardness of the marked areas of copper samples. The experiments were carried out with a fiber laser and a copper bromide laser—modern lasers widely used in industrial production. Laser power, scan speed and raster step were varied to determine their effects on the resulting microhardness and surface roughness. The lasers operate in different wavelength ranges, with the optical laser operating at 1064 nm in the near-infrared region and the copper bromide laser at 511 nm and 578 nm in the visible region, allowing the influence of wavelengths on the process to be investigated. The roughness and microhardness velocity dependence for three powers and two pulse durations for the fiber laser were obtained from the experimental data. The dependence of roughness and microhardness on the raster step for both types of lasers was also demonstrated.
  • Publication
    RESEARCHING THE PROCESS OF LASER STRUCTURING OF THE SURFACE OF ALUMINUM
    (2023-06-13)
    Kevins Bulavskis
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    Emil Yankov
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    ;
    In this scientific study, the ability to modify the surface using nanosecond 1064 nm fiber laser by controlling the speed and scanning line step in the marking process was demonstrated. An experimental matrix for laser marking was developed, consisting of 8 columns for marking line step and 5 rows for marking speed. The laser marked surfaces were measured using a laser scanning microscope and compared with the surface as supplied. From the obtained deviations of roughness Ra, Rz and Rq as a function of marking speed and marking line step, graphical dependencies were constructed for comparative analysis. The modified roughness is also compared with the roughness as supplied. Within this research the effect of laser treatment on the hydrophilicity/hydrophobicity of the surface was studied as well. Plots of dependences of the contact angle CA, the marking line step Δx and the overlap coefficient Ksoc are plotted.
  • Publication
    ANALYSING THE INFLUENCE OF TECHNOLOGICAL PARAMETERS ON THE PROCESS OF LASER MARKING OF SURFACE OF ANODISED ALUMINIUM SAMPLES
    (2023)
    Ļubova Denisova
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    ;
    Emil Yankov
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    The requirements for marking in terms of contrast and durability are constantly increasing. In order to meet all these challenges, it is necessary to carry out research leading to the optimisation and increase in efficiency of the technological process of laser marking. In the case of aluminium, the contrast and durability of the marking depend on the values of the laser marking parameters. In order to determine the optimal laser marking method, experimental studies have been carried out, controlling the power, speed, frequency, pulse duration and line raster step for a specific anodised aluminium. The studies carried out were analysed and subsequently optimized to obtain a contrast marking. A Rofin PowerLine F 20 Varia fiber laser system and aluminium alloy 1050 with anodised surface were used for the research. The surface changes after the laser treatment were analysed using a laser scanning microscope and contrast determination method. The dependence of contrast and roughness on speed, power, frequency and raster step was analysed. Comparative plots of contrast and roughness variations versus laser marking technological parameters were constructed.
  • Publication
    Modification of Aluminum 1050 and 2219 Alloys Using CuBr Nanosecond Laser for Hydrophobic and Hydrophilic Properties
    This study investigates the use of a CuBr vapor nanosecond laser with a 510 nm/578.2 nm wavelength for the surface treatment of 1050 aluminum and 2219 aluminum alloys. Laser-induced periodic surface structuring was used to optimize processing parameters to achieve hydrophobic and hydrophilic properties on the surface. The wetting properties were measured and the roughness results (Ra, Rz, Rq) evaluated. Prior to and after laser treatment, surface wetting and roughness changes were investigated. The wetting study showed that the maximum contact angle between a droplet of deionized water and the treated surface can be reached between more than 140 degrees and less than 10 degrees, which, respectively, is a superhydrophobic and superhydrophilic surface. Compared with the untreated surface, wetting increased by more than 2 times and decreased by more than 8 times. Overall, experiments show the dependence of wetting properties on laser input parameters such as scan speed and scan line distance with different delivered energy amounts. This study demonstrates the possibility of laser parameter optimizations which do not require auxiliary gases and additional processing of the resulting surfaces to obtain different wetting properties on the surface. The findings described in this article suggest that the CuBr laser surface treatment method is a promising method for industrial applications where surfaces with special wetting and roughness properties are required, for example, the laser marking of the serial number of parts used in wet environments such as aerospace, shipbuilding, and defense industries.
  • Publication
    Effect of Laser Marking Speed, Power and Pitch on Hardness and Roughness of Aisi 304l
    In this study, an experiment was conducted to change the technological properties of the surface by infra-red laser marking. The influence of power, speed and raster step was investigated. These parameters during laser marking of AISI 304L steel have a significant change on the microhardness and surface roughness. It was found that high stiffness is achieved at higher powers and small pitch. An analysis of the results showed that as the raster step increases, the roughness of the marked sample decreases. The influence of linear energy density and overlap factor on the process was also investigated. The microhardness of the treated surfaces increases with an increase in the linear energy density and the overlap coefficient, and in the first case the dependence is almost linear, and in the second - non-linear.
  • Publication
    INVESTIGATION OF THE INFLUENCE OF TECHNOLOGICAL PARAMETERS OF LASER MARKING ON THE DEGREE OF CONTRAST
    (2023)
    Petar Tsvyatkov
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    Emil Yankov
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    ; ;
    In modern production, each finished product entering the market is identified by a special marking. Each mark must meet requirements such as good coding, easy to see, easy to read by certain readers, stable over time, etc. In the present casting, laser marking of the C75 steel was carried out with a fiber laser with an average power of P = 30 W and a wavelength of λ = 1064 nm. For semi-contrast marking, marking speeds from 100 mm/s to 700 mm/s, average power from 10 to 30 W, raster pitch from 20 µm to 60 µm, scanning frequency from 20 kHz to 150 kHz were investigated as constant parameters are the pulse duration τ =100 ns, number of repetitions N = 1 and defocus Δ f = 0 mm. The influence of the changing parameters on the contrast was established, and experimental dependences were constructed. The achieved research results show that to obtain a high contrast mark, the average power should be above 20 W, the scanning speed up to 300 mm/s, the scanning frequency up to 50 kHz and the raster pitch up to 40 µm.
  • Publication
    INVESTIGATION OF SURFACE ROUGHNESS OF CARBON STEEL MACHINED PARTS AFTER NANOSECOND FIBER LASER MARKING
    (2023)
    Petar Tsvyatkov
    ;
    Emil Yankov
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    ; ;
    Laser marking with a nanosecond fiber laser is one of the most common ways to permanently mark various engineering materials. The roughness of the machined surface and its observation is essential to evaluate the impact on the contrast of the marking as well. Experimental studies of the roughness obtained as a result of the laser marking, were inspected using a 3D measuring laser microscope OLYMPUS LEXT OLS5100. Analysis of the graphical dependence of the roughness function on the four process parameters: laser power, frequency, speed of marking and step.
  • Publication
    COLOR MARKING OF STAINLESS STEEL AND TITANIUM WITH THE LASER OXIDATION METHOD
    (2023)
    Petar Tsvyatkov
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    Emil Yankov
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    ; ;
    Marking of metal products is essential in many industrial processes. It is mandatory for the finished products according to regulations of the European and world legislation. Traditional marking usually creates contrasting symbols that can easily be erased and forged.In recent years, a new method for product identification has appeared - color marking. One of the advantages of this method is that it is difficult to counterfeit. This article aims to present the progress of color marking technology on two types of materials. Three groups of factors have been analyzed: the laser source; the technological process; material properties. Their role in obtaining a specific color marking on Ti and AISI 304 is shown. The results are presented in tables. Each color can be repeated only with strict observance of the three groups of factors.
  • Publication
    Investigation of the Influence of Some Parameters on the Process of Color Laser Marking
    (2023)
    Emil Yankov
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    ; ;
    Nikolay Angelov
    The research and development of laser marking technology offers numerous advantages and applications in a variety of industries, from manufacturing and electronics to healthcare and beyond. In industries such as aerospace and automotive, where components must adhere to strict regulatory standards, laser marking can provide the necessary traceability and compliance. Investing in its research and development improves precision, efficiency and innovation, ultimately contributing to advancements in various sectors and driving economic growth.For this purpose, various surface treatment methods are being studied, including laser marking. As can be seen from our previous studies and those of other authors, laser marking of steel surfaces is a complex process and depends on the complex relationships between a number of technological parameters. In this study, we focus on the influence of four of them (parameters: processing speed, laser pulse frequency, pitch between raster lines during laser processing and energy density). During the experiments, the raster step was varied in the range of 20 µm to 80 µm, the velocity was in the range of 25 mm/s to 125 mm/s, and the density was in the range of 5.82 J/mm2 to 29.12 J/mm2. The experiments were done for three frequencies - 20 kHz, 50 kHz and 100 kHz. All these intervals can be realized in the real production. The change of the four investigated parameters was analyzed in relation to the obtained roughness in the processing zone as a function of these four technological parameters and was compared with the corresponding color coordinates of the obtained color markings in these zones. It has been proven that each specific color is associated with surface structural changes as a result of the interaction between laser radiation with a certain laser energy density and the processed material. The present study is a small contribution to the topic of laser color marking of various materials, enabling the production of new surface properties.