Laser Head Research Articles

Adjustable ring shaping for laser welding applications

AbstractHigh laser welding speed can be achieved by using a ring and central spot laser illumination profile, with an adjustable ratio of the ring energy to the spot enabling optimization of the process. We present a novel and simple diffractive‐based concept to achieve such adjustable shaping for standard fiber lasers. The module is rotation‐adjustable between 100 % energy in the central spot to no energy in the central spot, can work with both single‐mode and multimode lasers, is highly compact (less than 20 mm long) and has the high LDT of passive diffractive components. This concept obviates the need for special ring‐type fiber lasers, enabling simpler design of the welding laser head.

Mechanical System Design and Motion Space Analysis For Transmission Line Insulators Laser Deicing Robot

In the cold winter, it is a routine task to deicing on transmission lines in severe cold climate so as to ensure the safety and stable operation of transmission lines. Compared with the traditional contact deicing method for transmission line insulators, the using of laser for transmission line deicing has the advantages of sound deicing effect, no damage to the lines, clean and efficient energy utilization, et al. As the laser energy gradually decays with the increase of distance, this paper proposes a new method to realize laser deicing of short-range transmission line insulator by using UAV equipped with laser. In responds to the dispersion problem of traditional control, this paper fully integrates U AV control and laser control platform, the double have been integrated into one, in the new control platform, the U AV control and laser control can be realized simultaneously, the kinematics model of the laser has been established and its forward and inverse solutions have been solved and analyzed. Finally, simulation experiments verify the validity of the model. Compared with the traditional mode, this deicing mode not only realizes the control integration, but also it is easy to operate. It is especially suitable for the operation in the transmission line field environment, which greatly enhances the robot operation efficiency. At the same time, the simulation of laser head sweeping space and deicing operation motion planning based on the kinematic model show that the system designed in this paper can realize the suspension insulators deicing without blind area. The implementation and promotion of this study has important theoretical significance and practical application value for the practicability of intelligent operation and transmission lines maintenance management.

Estimating the Accuracy of Mandible Anatomical Models Manufactured Using Material Extrusion Methods

The development of new solutions in craniofacial surgery brings the need to increase the accuracy of 3D printing models. The accuracy of the manufactured models is most often verified using optical coordinate measuring systems. However, so far, no decision has been taken regarding which type of system would allow for a reliable estimation of the geometrical accuracy of the anatomical models. Three types of optical measurement systems (Atos III Triple Scan, articulated arm (MCA-II) with a laser head (MMD × 100), and Benchtop CT160Xi) were used to verify the accuracy of 12 polymer anatomical models of the left side of the mandible. The models were manufactured using fused deposition modeling (FDM), melted and extruded modeling (MEM), and fused filament fabrication (FFF) techniques. The obtained results indicate that the Atos III Triple Scan allows for the most accurate estimation of errors in model manufacturing. Using the FDM technique obtained the best accuracy in models manufactured (0.008 ± 0.118 mm for ABS0-M30 and 0.016 ± 0.178 mm for PC-10 material). A very similar value of the standard deviation of PLA and PET material was observed (about 0.180 mm). The worst results were observed in the MEM technique (0.012 mm ± 0.308 mm). The knowledge regarding the precisely evaluated errors in manufactured models within the mandibular area will help in the controlled preparation of templates regarding the expected accuracy of surgical operations.

Improvement of a laser head by changing the topology of its body parts and the collimator mounting method

Improvement of a laser head by changing the topology of its body parts and the collimator mounting method

Feasibility of Luminophores in Solar-Pumped Laser Heads

Feasibility of Luminophores in Solar-Pumped Laser Heads

Experimental Researches of Turning Hardened 9CrSi Alloy Tool Steel with Laser-Assisted Machining

In this study, in order to verify the influences of various parameters such as laser power, laser spot diameter on the workpiece, laser position, laser head speed, and feed rate on the depth of heat-affected zone (HAZ) after laser heating hardened 9CrSi alloy steel (62 HRC hardness) before turning process, Taguchi experimental method had been applied. The experimental results show that the laser power and laser head speed strongly affect the depth of HAZ comparing with the others of laser source’s parameters. Specifically, the results of the ANOVA for the depth of HAZ revealed that the laser power at static state and laser head speed at dynamic state made the highest contribution of 91.27 and 95,69% to the overall performance, respectively. This study then analyzes the effects of parameters such as laser power, cutting speeds, feed rate, and cutting depth on the depth of HAZ and microhardness of the workpiece after turning hardened 9CrSi alloy tool steel with laser-assisted machining. The analysis of the experimental results shows that if the cutting depth and cutting speed is from and over 0.15 mm, and 71 m/min, respectively, leads to the microstructure and microhardness of the workpiece after machining are significantly unaffected. Finally, the experimental surface responses of surface roughness and cutting force are obtained based on the reasonable zone of input parameters. The ANOVA results also confirmed that laser power made the highest contribution to the surface roughness and the feed rate contribute the major effect to the cutting force of 69.4 and 63.56%, respectively.

Metallurgical characterization of laser hardened, mechanically textured 2.5 Ni-Cr-Mo low alloy steel and optimization using RSM

Surface modification of 2.5 Nickel-Chromium-Molybdenum low alloy steel is carried through laser transformation hardening technique under different laser parameters. A 4 kW high power diode laser with a flat top-hat beam of dimension 10x1mm is employed in this study. In this investigation, substrate surface was roughened with abrasive paper to minimize the specular reflection and to increase the absorption rate of laser beam. Microstructure analysis, corrosion analysis, residual stress distribution and the percentage of austenite retained in the hardened region were done. Response Surface Methodology (RSM), a statistical method used for analyzing input variables (Laser power (LP), scan speed (SS) and focal plane distance (FPP)) that influences the hardening process and response optimization, is employed in this study. Characterization analysis of specimen reveals the presence of lath type martensite microstructure in the hardened region with nearly 2.5 times increase in hardness (700 ± 10HV0.5) is achieved with a combination of 1000 W laser power, 240 mm/min scanning speed and 290 mm laser head distance (optimal solution) obtained from the RSM. By performing residual stress analysis, compressive type residual stress at the laser hardened region's cross-section is confirmed. With the optimum laser parameters, a peak residual stress value of −211 MPa is achieved. Retained austenite percentage analysis and corrosion analysis were carried out at the hardened region of RSM's optimal solution. It is observed that 5.76% of retained austenite is obtained in the hardened region using laser hardening. In corrosion, the hardened track obtained using the optimal solution showed a significant improvement in corrosion resistance than that of the base metal due to microstructural homogenization.

A study of the effects of gamma radiation on optical components used in specially constructed hot cell laser-induced breakdown spectroscopy (LIBS) instruments

Two innovative hot cell Laser-Induced Breakdown Spectroscopy (LIBS) instruments, designed and built by Applied Photonics Limited, are set to be deployed for the purpose of material characterisation in a high radiation environment. One LIBS instrument uses a ‘through-wall’ optical periscope, where the laser and optical spectrograph are located outside of the hot cell. The second instrument uses a remote probe located within the hot cell, containing a compact Nd:YAG (neodymium-doped yttrium aluminium garnet) passively Q-switched laser and plasma light collection optics.The design of both LIBS instruments means that some optical components (e.g. prisms, lenses, fibre optic cables and, in the case of the in-cell remote probe, a Nd:YAG laser head custom-designed and manufactured by Applied Photonics Ltd) will be exposed to high levels of gamma radiation. This entails that these components must be suitably reliable and gamma radiation resistant to last the duration of the planned work. In this article, we report on the results of a limited study on the effect of gamma irradiation (5 kGy, 25 kGy and 50 kGy absorbed dose using a cobalt-60 gamma source) on the optical properties of BK7 (Crown glass) and Ultra-Violet Fused Silica (UVFS) lenses, both with and without high-energy V-coat anti-reflection coating, and UVFS fibre optic cables. The effect of gamma irradiation on the pulsed laser beam energy output of three passively Q-switched Nd:YAG laser heads was also evaluated. The performance of each of the laser heads was tested before and after gamma irradiation by using an energy meter to measure the laser energy output of each of the three laser heads. The optical transmission properties of the components used for plasma light collection and transmission (i.e. lenses, fibre-optics) were tested using a deuterium-halogen lamp in combination with an optical spectrometer. In this limited study, we found that the BK7 lenses were clearly affected by the gamma radiation in that they became light to dark brown in appearance with increasing gamma irradiation whereas the UVFS optics (coated and uncoated) appeared visually, at least, to be unaffected. The optical transmission tests showed that the BK7 lenses became increasingly opaque to UV-VIS wavelengths with increasing gamma irradiation whereas the UVFS lenses and prisms were not so affected. The high-energy V-coat anti-reflection coatings appeared also to be unaffected by the gamma irradiation levels used in this study, at least within the limits of this investigation. However, the UVFS fibre-optic cables did show a reduction in transmission of UV light with increasing gamma irradiation.

Characterization of a chromatic confocal displacement sensor integrated with an optical laser head.

In this paper, the results of experimental characterization of an optical system consisting of a chromatic confocal displacement sensor integrated with an optical laser head are presented. As a result of integration, the part of the optical path of the displacement sensor was combined with the optical path of the laser beam. Consequently, a working distance of 250 mm for the optical system was achieved. The main aim of the characterization was to determine the calibration curve, as well as the application parameters of the system. The methodology for spectral data processing with particular emphasis on the effectiveness of various extraction algorithms is presented. The Lorentzian fitting was considered as the optimal algorithm for the optical system. Consequently, a large measuring range of 10 mm was obtained with perfect linear tendency of the calibration curve. The optical system was characterized by high accuracy equal to ±0.11% of the measuring range, as well as 1 µm resolution. Moreover, the functionality of the system was verified on materials commonly used in laser processing and additive manufacturing. Finally, the system was validated through a comparative measurement with a laser profiler.

Development of a novel high temperature open tribometer with laser-based heating system

Contacts operating under severe conditions such as high temperatures, contact pressures and/or sliding velocities, can occur in many applications and especially in metalworking processes. The extreme thermomechanical loadings withstood by the tooling during such interaction directly govern their lifetime but also the functional properties of the component surface. Understanding the friction and wear mechanisms behind is still an issue and can only be addressed with a relevant experimental set-up. This work presents the development of a new laser-based heating system fitted on an open tribometer with the aim of investigating such severe contact conditions for a AISI1045 carbon steel during sliding against uncoated cemented carbide. A 3D numerical approach is adopted to design the system and predict the temperature distribution, as well as the heating rates, below the laser beam and at the expected contact zone. A phase transformation model based on the simulated thermal kinetics is applied to identify the conditions leading to the potential formation of austenite and to show that a proper combination of laser power and sliding velocity has to be selected to ensure the desired contact conditions. It is shown for example that even at high sliding velocities, a maximum temperature of 600∘C can be reached in the contact zone without exceeding the melting temperature ahead while only a thin layer can be affected by the laser. The experimental set-up is described with the integration of a laser head into the test bench. An experimental campaign is carried out to show the influence of the temperature and sliding conditions on the tribological behavior especially in terms of friction, wear mechanisms and microstructural evolution beneath the contact track.

Quasi-Gaussian Multibeam Solar Laser Station for a Megawatt Solar Furnace

An alternative multirod solar side-pumping concept for the production of multiple quasi-Gaussian beams is proposed. This scheme was based on the One-Megawatt solar furnace in Odeillo, France, which collected and concentrated the solar light into a multilayered pyramidal pumping cavity placed at the focal zone. Each layer was comprised of a square array of four laser heads, each composed of a biconic surface that reflected the solar rays towards a Nd:YAG rod fixed inside a fused silica flow tube. A pyramidal reflector was placed inside the pumping cavity to close it and maximize the harness of solar energy. Compared to the previous multibeam solar laser station design for the same solar furnace, considerable alleviation of thermal lensing effects was achieved with the present approach, allowing the improvement of the laser beam quality factors and, consequently, the possibility of a 32-laser-beam generation, each with a quasi-Gaussian profile. For this case, 9.44 kW total laser power was calculated. Additionally, 20.01 kW total multimode laser power was numerically determined, which corresponds to a 10.93 W/m2 collection efficiency and a 2.0% solar-to-laser power conversion efficiency.

Quasi-Gaussian Multibeam Solar Laser Station for a Megawatt Solar Furnace

An alternative multirod solar side-pumping concept for the production of multiple quasi-Gaussian beams is proposed. This scheme was based on the One-Megawatt solar furnace in Odeillo, France, which collected and concentrated the solar light into a multilayered pyramidal pumping cavity placed at the focal zone. Each layer was comprised of a square array of four laser heads, each composed of a biconic surface that reflected the solar rays towards a Nd:YAG rod fixed inside a fused silica flow tube. A pyramidal reflector was placed inside the pumping cavity to close it and maximize the harness of solar energy. Compared to the previous multibeam solar laser station design for the same solar furnace, considerable alleviation of thermal lensing effects was achieved with the present approach, allowing the improvement of the laser beam quality factors and, consequently, the possibility of a 32-laser-beam generation, each with a quasi-Gaussian profile. For this case, 9.44 kW total laser power was calculated. Additionally, 20.01 kW total multimode laser power was numerically determined, which corresponds to a 10.93 W/m2 collection efficiency and a 2.0% solar-to-laser power conversion efficiency.

Mechanical Properties of White Metal on SCM440 Alloy Steel by Laser Cladding Treatment

The bearing is a machine element that plays an important role in rotating the shaft of a machine while supporting its weight and load. Numerous bearings have been developed to improve durability and life, depending on the functions and operating conditions in which they are desired. White metal is one of method to improve durability that is soft and bonded to the inner surface of the bearing to protect the bearing shaft. Currently, the centrifugal casting process is used as a white metal lamination method, but it involves problems such as long processing times, high defect rates and harmful health effects. In this paper, a laser cladding treatment is applied to bond powdered white metal to SCM440 alloy steel, which is used as bearing material in terms of replacing the risks of a centrifugal process. In order to understand whether laser cladding is a suitable process, this paper compares the mechanical properties of white metal produced on SCM440 alloy steel by centrifugal casting and the laser cladding process. The laser power, powder feed rate and laser head speed factors are varied to understand the mechanical properties and measure the hardness using micro Vickers and conduct field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction and friction testing to understand the mechanical properties and surface characteristics. Based on the results, the hardness values of the cladding (white metal) layer ranged between 24 and 26 HV in both the centrifugal casting and laser cladding methods. However, the hardness of the white metal produced by laser cladding at about a depth of 0.1 mm rose rapidly in the cladding process, forming a heat-affected zone (HAZ) with an average hardness value of 200 HV at a laser power of 1.1 kW, 325 HV at 1.3 kW and 430 HV at 1.5 kW. The surface friction testing results revealed no significant differences in the friction coefficient between the centrifugal casting and laser cladding methods, which allows the assumption that the processing method does not significantly influence the friction coefficient.

Femtosecond System with Pulse Pumping of Seed Laser and Amplifier by Using a Single Power Unit

For several decades development of methods for generating ultrashort pulses has been an independent urgent scientific and technical problem. There is a constant improvement both in the methods of such pulses receiving and in methods of their use. The aim of this work was to investigate the possibility of realizing the coordinated operation of two fundamentally different types of pump lasers for the femtosecond oscillator and amplifier based on one single-lamp laser head and to create on this basis a compact high-power femtosecond system with pulsed pumping and one power unit.The practical implementation of two types of pulsed lasers (nano- and picosecond ones operating, respectively, in Q-switch and modelock regime) on a single laser head with two active elements and one pump lamp is carried out. The required synchronization in time the pump pulse femtosecond amplifier formation and quasi-stationary region of generated pulses in the output radiation of a femtosecond Ti:sapphire is obtained.On this basis a compact, pulse pumped monoblock laser system has been developed that can generate femtosecond pulses with a duration of 50–150 fs with an energy up to 1 mJ and a high enough pulse repetition rate (up to 1 kHz which is determined by the type of laser head and pump unit used). In the developed laser system a compact scheme of a stretcher-compressor with a single common diffraction grating is used.Laser systems of this type characterized by a relatively low cost due to the use of a single power supply unit for simultaneous pumping of the amplifier and oscillator, as well as lower requirements for the quality of optical elements and usage conditions due to the pulse mode of operation, are quite practical and can be used both in scientific research in the field of ultra-high-speed kinetic spectroscopy and nonlinear optics, as well as in numerous technical applications, particular in the precision processing of materials, as optical simulators of the action of heavy charged particles in testing the radiation resistance of integrated circuits and electronic modules.

Focus on lasers, imaging, microscopy, and nanoscience

Focus on lasers, imaging, microscopy, and nanoscience

Monitoring molten pool temperature, grain size and molten pool plasma with integrated area of the spectrum during laser additive manufacturing

A new approach is presented in this paper to link the integrated area of the spectral curve with the molten pool temperature, the grain size and molten pool plasma during laser additive manufacturing. A fiber laser was used to deposit the CoCrMo powder on the Q235 steel substrate. The spectra generated during the additive manufacturing process were collected with an optical spectrometer attached to the laser head. According to the thermal radiation theory and the rapid solidification theory, spectral information was applied to calculate the molten pool temperature and the grain size. The relationship between the molten pool temperature and the integrated area of the spectral curve, as well as the relationship between the grain size and the integrated area of the spectral curve was established, respectively. Meanwhile, the electron temperature and electron density of the molten pool plasma were calculated from two different Cr I spectral lines at 403.292 and 434.429 nm wavelength. The results show that the molten pool temperature and the grain size are closely related to the integrated area of the spectral curve. Furthermore, the electron temperature and electron density also increase with the integrated area of the spectral curve.

Removal mechanism of surface cleaning on TA15 titanium alloy using nanosecond pulsed laser

Nanosecond laser cleaning provides an alternative cleaning method that displays a significantly improved cleaning efficiency without environmental pollution. This paper reports the results of an investigation into the nanosecond pulsed laser cleaning of TA15 titanium alloy oxide film using the laser fluence and the laser head moving speed as variables. The TA15 titanium alloy oxide film changed from original silver gray to silvery white with the increase of laser fluence. However, the material surface transformed from silvery-white into yellowish-brown when the laser energy fluence exceeded 5.97 J/cm2. This phenomenon was attributed to the formation of titanium alloy oxides (Ti6O, TiO2-anatase, γ-TiO2, and TiO) after removing the oxide film using a high laser fluence at atmospheric conditions. The best surface properties were obtained when the laser fluence and the laser head moving speed were set to 3.98 J/cm2 and 5 mm/s, respectively. The oxidation content and roughness were 2.08 wt% and 37 μm, respectively. The removal effect of the oxide film was best when the surface temperature was slightly higher than the boiling point of the oxide film, as shown by numerical calculations and analysis. The main mechanism of laser cleaning was laser ablation.

An analytical model of bead morphology on the inclined substrate in coaxial laser cladding

Abstract Laser cladding has been extensively used to repair and remanufacture large and expensive parts as an emerging surface treatment technology. In order to avoid interference between the laser head and the complex surface of the part during repair, however, the surface to be repaired is often placed obliquely. Since the morphology of the cladding bead will affect the overall surface quality after cladding, an analytical model has been developed to estimate the clad geometry (width and height) on the inclined substrate depending on the process parameters and material properties in this paper. The predicted results are basically consistent with the experimental results, which shows the accuracy of the model. In addition, the influence of process parameters and the tilt angle of the substrate on the width and height of the cladding bead on the inclined substrate has also been studied. The results show that the width is mainly affected by the laser power, and the height is mainly affected by the scanning speed and powder feeding rate. The tilt angle affects both, so it is also the main factor affecting the ratio of width to height. This findings can provide reference for the substrate placement and the selection of process parameters during surface repair of complex parts.

Modeling laser head housing and engineering by analyzing walls rigidity in CAE-systems

The paper considers a possible way to expand the technological capabilities of numerically controlled machines by upgrading and integrating a fiber laser system into their composition. An important task is to facilitate the details of laser head housing while maintaining their stiffness parameters. To achieve the aim of the research, the laser head body was completely redesigned, some structural elements were combined, and all the walls of the body became lighter and more functional. The new design will be much more convenient to use while maintaining the same rigidity. The new laser head housing will make it possible to expand the range of work for numerically controlled machines, which in turn will lead to a reduction in the production time of not only one product, but also the final product as a whole. This approach will reduce the cost of maintaining and maintaining a large number of equipment, since the integration of laser equipment into numerically controlled machines will reduce the number of equipment in the workshops. In addition, marking and manufacturing parts on the same machine will not only significantly automate the processes of further Assembly of the final product by applying QR codes, but also will increase the accuracy of marking and engraving on the product due to a one-step process.

Analysis, topology modification and modeling of the laser head casing taking into account the capabilities of additive equipment

The article considers the issue of improving the design of the laser head casing in order to ensure its compactness and take into account the capabilities of additive equipment that allows making more complex plastic casing parts without violating the collectability and maintainability of the laser head casing. The manufacture of a laser head casing made of plastic makes it possible to reduce its material consumption in comparison with a casing made of aluminum alloy. At the same time, it is proposed to further reduce the material consumption of the plastic casing due to the introduction of special recesses and stiffening ribs into its design. In the CAE-module of the CAD/CAM-system SolidWorks, a comparative analysis of the strength and stiffness of the laser head casing design options, assembled from parts with recesses and stiffeners, as well as without them. The modeling results of the deformation process for the casing variants convincingly showed that it is possible to replace the material of its parts from aluminum alloy to plastic and that reducing the material consumption and changing the design of the casing does not lead to such a loss of its strength and rigidity which causes an unacceptable deviation of the laser beam from the vertical, that is, does not affect the functioning of the laser head.