57 results about "Laser power density" patented technology

The invention discloses a laser cutting method for cutting complex shapes, and particularly relates to the field of laser cutting. A three-dimensional curved surface model of a to-be-cut workpiece is obtained, and a surface normal tensor field is constructed; extracting a driving point set based on the curvature derivative and generating a sliding path network; constructing a laser power density mapping model in combination with the thermal diffusion response model and the thermophysical parameters of the material; thermal feedback images are collected in the cutting process, an energy offset function is constructed, laser focus displacement and the scanning rate are dynamically adjusted through fuzzy control, and closed-loop control over power, paths and thermal feedback is achieved; according to the method, self-adaptive adjustment of laser power distribution, curved surface adaptation of a cutting path and thermal field real-time compensation in the machining process can be achieved under a complex geometric structure, the cutting precision, stability and energy efficiency are effectively improved, and the method is suitable for laser machining application of high-requirement complex structures such as aerospace, mold manufacturing and medical instruments.

The invention relates to the technical field of laser pipe cutting machining, and discloses a laser pipe cutting machine machining optimization method for small pipes. The method comprises the following steps: acquiring three-dimensional point cloud data of a to-be-processed pipe, and extracting a pipe axis direction vector and pipe wall thickness distribution data through geometric topology analysis; a dynamic machining coordinate system is established based on the axis direction vector, and the theoretical projection position of the laser focus in the coordinate system is calculated; material absorption characteristic parameters are matched according to the pipe wall thickness distribution data, and a laser power density gradient adjusting instruction is generated; monitoring the radial run-out amount in the rotating process of the pipe in real time, and generating a laser focus track compensation parameter in combination with a theoretical projection position; and finally, the laser power density gradient adjusting instruction and the focus track compensation parameters are fused to generate a cutting path control signal, and a laser cutting head is driven to complete machining. According to the method, the problems of insufficient precision and unstable quality in the machining process of small pipes are effectively solved, and the machining adaptability is improved.

The invention provides an intelligent cleaning control method and system for an engine piston ring, and the method comprises the steps: building a dynamic cleaning path through obtaining the residue phase change gradient, the laser beam incident angle, the roughness and the oxide layer thickness data of a laser thermodynamic action region on the surface of the piston ring; in the cleaning process, based on oxide layer thickness distribution, a deep learning model is used for generating target scanning frequency offset in real time, and laser power density and focusing depth parameters are further optimized. And by dynamically adjusting laser energy distribution, precise removal of residues is achieved, and meanwhile a piston ring base material is protected. The cleaning precision of the engine piston ring is improved.

The invention provides a flexible high-energy laser sensing film sensor. The flexible high-energy laser sensing film sensor comprises a sensing film and a laser high-reflection film layer on the surface of the sensing film. The sensing film is composed of a flexible substrate, an upper surface transition layer, a lower surface transition layer, an upper surface thermistor layer, a lower surface thermistor layer, an upper surface lead layer, a lower surface lead layer, an upper surface protection layer and a lower surface protection layer. The thin film type double-sided resistor array is used for monitoring the laser irradiation transient thermal effect in real time, the laser detection threshold value is increased in combination with the laser high-reflection film layer, and rapid and accurate measurement of laser irradiation parameters such as laser power density, light spot size and irradiation position can be achieved; the device solves the problem that the existing devices such as a laser power meter and a laser spot analyzer are limited in light sensing diameter and are difficult to be suitable for large-spot-size laser parameter measurement and laser sensing alarm, and has the advantages of flexibility, large area, simple structure, low cost and the like.

The invention belongs to the technical field of laser processing numerical simulation, and discloses a random forest model laser absorption coefficient efficient prediction method based on factor analysis, and a laser absorption coefficient data set comprises four parameters of laser power density, a forming coefficient, conductivity and thermal diffusivity. According to the method, multiple factors influencing the laser absorption coefficient in laser processing are comprehensively considered, the dimensionality of a data set is reduced, the feature correlation between data is low, and a high-quality training set is provided for subsequent training of a random forest model. Multiple Gaussian distribution linear mixing probability distributions are generated through a Gaussian mixture model to describe original data, new samples are generated through random sampling to form an incremental data set, the training effect of the random forest model is improved, and the over-fitting condition is avoided; through factor analysis, features with strong correlation are divided into one group, generation of a weak decision tree is avoided, the accuracy and convergence speed of the model are improved, and an efficient model training mode is realized.

The present application provides a method and system for estimating the on-target laser power density required to burn through protective materials. The method of the present application includes: constructing a tightly coupled model between fluid, structural heat transfer, and laser through several sets of protective material ablation simulation tests; using the tightly coupled model to analyze the factors affecting the laser ablation characteristics of the protective material to obtain the main influencing factors; conducting simulation tests on the main influencing factors under different working conditions to obtain the laser ablation characteristics of the protective material under different main influencing factors, and then establishing a laser ablation database for protective materials; obtaining the ablation rate required to burn through the protective material, and obtaining the on-target laser power density required to burn through the protective material through the protective material laser ablation database and the required ablation rate. The present application can quickly predict the on-target laser power density required to burn through aircraft protective materials under flight conditions, thereby providing technical support for future aircraft thermal protection design.

The invention relates to an iridium radioactive source shell welding method and system, and belongs to the technical field of welding. The iridium radioactive source shell welding method comprises the following steps that a shell is rotated, and the shell and an end cover are preheated through laser; inputting actual thickness size information of the shell and actual thickness size information of the end cover; the laser adjusts the preset laser power density and defocusing amount according to the actual thickness size information and the standard thickness size information of the shell and the end cover; the automatic rotating mechanism adjusts a preset rotating speed according to the actual thickness size information of the shell and the actual thickness size information of the end cover; the assembled shell and end cover are installed on an automatic rotating mechanism; and the shell and the end cover are welded according to the preset laser power density and defocusing amount, and the automatic rotating mechanism drives the shell and the end cover to rotate according to the preset rotating speed until welding is completed. According to the iridium radioactive source shell welding method provided by the embodiment of the invention, the thickness size of each part of the manufactured iridium radioactive source shell is uniform.

The application provides a high-performance composite femtosecond laser processing variable cross-section hole forming precision control method, relates to the technical field of laser processing, and first discretizes a target hole into a plurality of processing layers along a depth direction, and establishes a Cartesian coordinate system; the effective radius of a spot and a projection area of each layer are calculated in combination with hole taper; on this basis, a reference power density decay model is constructed, a laser incidence angle is further introduced, and a mapping model between hole taper, laser incidence angle and laser power density is established. Finally, according to the target hole taper and the target removal efficiency, the laser incidence angle required by each processing layer is inversely solved, and the dynamic regulation and control of the rotary cutting head and the cradle turntable are realized accordingly. The method can realize layer-by-layer closed-loop control of the variable cross-section hole forming precision, effectively compensate for the laser power decay in the depth direction, and improve the precision of laser processing.

The invention relates to a real-time on-line ultrafast laser dielectric film damage threshold testing system, which belongs to the technical field of ultrafast laser, and comprises a forward Brillouin compression system for generating forward Stokes light and compressing and amplifying the forward Stokes light; the forward non-focusing SRS compression system is used for generating asymmetrically amplified and compressed laser to obtain high-energy short-pulse laser; the grating film damage threshold testing system is used for bearing the optical dielectric film, receiving the processed laser, enabling the laser passing through the interior to penetrate through a damage point of the optical dielectric film, and calculating a damage threshold according to the laser power density and the light spot area; the phase interference damage judgment system is used for carrying out real-time on-line damage judgment and quantification, generating interference fringes through two beams of light, quantifying the interference fringes and detecting the damage degree of the optical element thin film on line in real time; the method has the beneficial effects that the energy irradiated on the tested grating film sample is calculated according to the beam splitting ratio, and the grating film damage threshold value is calculated.

The invention discloses a multi-scale calculation method for material failure under laser loading, and relates to the technical field of laser protection. The method comprises the following steps: firstly, respectively describing temperature changes of free electrons and crystal lattices on the surface of a material through a double-temperature model, simulating a transfer process of laser energy, and calculating thermal diffusion and temperature field evolution of the material under laser irradiation; secondly, simulating atomic-level thermal response, microstructure change, stress field distribution and a fracture process of the material under a laser loading condition by utilizing molecular dynamics; and finally, coupling the double-temperature model and molecular dynamics simulation, and analyzing the failure behavior of the material under laser loading by combining macrothermodynamics and microstructure analysis. According to the method, the influence of laser parameters such as different laser power densities, wavelengths and pulse widths on the material performance can be processed, the failure characteristics of the material can be accurately predicted, and compared with an existing single-scale model, the microstructure change of the material under laser irradiation can be more truly reflected.

The invention belongs to the technical field of material surface treatment, and provides a TC4 alloy surface treatment method based on laser shock peening and laser metal deposition, and the method comprises two parts of preparation of a TC4 alloy material test piece and laser shock peening of the formed test piece. According to the surface treatment method for preparing the TC4 alloy material based on selective laser deposition, various properties of the surface of the TC4 alloy are improved in the mode of regulating and controlling the laser power density, the problem that residual stress is generated in the material in the process of preparing the TC4 alloy through laser metal deposition is solved in the mode of laser shock peening, and the quality of the TC4 alloy material is improved. Compared with the prior art, the method has the advantages that various properties of the material surface can be improved, residual tensile stress on the surface of a part can be reduced through plastic deformation generated in the impact process, the deformation resistance of a test piece is improved, and initiation, expansion and cracking of cracks of the part are inhibited.

This invention discloses a method for CO2 continuous laser cutting of CFRP material. The method employs a CO2 continuous laser engraving and cutting system to cut CFRP material. After adjusting the corresponding working parameters, a portion of the CFRP material to be cut is taken as a sample, and a rectangle is obtained through trial cutting. The diameters of the pits generated by the spot laser are measured horizontally and vertically twice, and the average diameter is calculated. Simultaneously, the continuous laser power density is calculated, and the height difference between the four corners and the center of the rectangle is measured to obtain the surface fluctuation value (Fv). Different scanning speeds, number of consecutive processing cycles, and Z-axis scale values ​​are selected, and trial cutting is repeated on the sample. When the measured Fv is at its minimum value, the thermal damage to the material is minimized. The scanning speed, number of consecutive processing cycles, and Z-axis scale value at this minimum value are used as the working parameters for cutting the CFRP material. This invention effectively controls the thermal damage to the CFRP material during processing and improves the processing effect of laser-processed CFRP material.

The invention relates to the technical field of laser control methods, and discloses a laser power density self-adaptive regulation and control method and system based on target features and distances, S1, a pre-calibration stage: calibrating the sizes and forms of light spots of a variable-focus beam expander under different target distances and different target features, establishing a mapping relation graph of the target distance, the target feature and the laser power density; s2, performing power-on self-test, entering a self-test mode after starting, performing detailed calibration on the sizes and forms of light spots of the variable-focus beam expander under different target distances and different target features through a pre-calibration stage, and establishing a mapping relation graph of the target distances, the target features and the laser power density, so that the target distance and the target features can be accurately determined according to the distance and the features of the current target; the mapping relation graph is inquired, the laser output power is adjusted according to the principle that the laser power density reaching the target is basically kept unchanged, and proper laser power output can be achieved under different distances for targets made of different materials.

The invention discloses a device and a method for quickly identifying the surface interference effect of a photoelectric detector, and solves the technical problem that the measured value of laser power density is deviated due to the interference effect on the surface in the practical application of the existing photoelectric detector. The recognition device comprises a laser, a collimator, a diaphragm, an angle adjusting table, a data acquisition card and a display unit, the laser is a wavelength tunable laser; the collimator is arranged close to the laser, and the diaphragm is an aperture diaphragm; the angle adjusting table is used for mounting the photoelectric detector and adjusting an included angle between a light-sensitive surface of the photoelectric detector and an optical axis of emergent light; the input end of the data acquisition card is connected with the output end of the photoelectric detector and acquires a light intensity signal output by the photoelectric detector; one output end of the data acquisition card is connected with the laser and used for outputting an analog voltage signal in a regular shape to tune the output wavelength of the laser, and the other output end of the data acquisition card is connected with the display unit; the display unit receives the light intensity signal and displays the light intensity signal in real time.

The invention belongs to the technical field of laser-assisted machining, and relates to a free-form surface-oriented laser-assisted machining beam adaptive regulation and control device and method, and the method comprises the steps: planning a tool path on a free-form surface to be machined, and calculating a curved surface derived function equation; obtaining a deviation value between the actual position center of the contact area of the cutter and the to-be-machined surface and the design position center of the contact area of the cutter and the to-be-machined surface by utilizing the geometric parameters of the cutter and the curved surface derived function equation; calculating a laser beam deflection angle by using the deviation value; the laser spot size and laser power density distribution are obtained through the actual length of the contact area of the tool and the to-be-machined surface; obtaining a laser beam defocusing distance by using the laser spot size and the laser power density distribution; and enabling the laser to rotate along the deflection angle of the laser beam and linearly move along the defocusing distance of the laser beam so as to realize self-adaptive regulation and control of the laser beam. According to the invention, self-adaptive adjustment of the free-form surface full-aperture laser beam can be realized.

The invention provides an annealing method and an annealing device of a solar cell, which are applied to the solar cell of which the same surface comprises two different sub-regions, and the annealing method comprises the following steps: irradiating a first region and a second region by adopting laser; wherein at least one of the laser parameters for irradiating at least part of the first area and the laser parameters for irradiating at least part of the second area is different, and the laser parameters comprise laser power density and laser irradiation time. According to the method, a selective laser annealing mode is adopted, different laser process parameters are adopted for the two different sub-regions, finally, the two regions form a good passivation effect, and the contact resistance of metal and a silicon layer is improved.

The invention relates to a method for laser welding of components (10), comprising the following steps: providing at least two components (10), the components (10) being coated, the components being made of a high-strength metal; at least three laser spots (12) are produced on at least one surface (14) of at least one component (10), the laser spots (12) each having a core region (16) and a ring region (18), the average laser power density in the core region (16) being higher than the average laser power density in the ring region (18), and the laser spots (12) producing a common melt pool (20) in the component (10). The invention also relates to an assembly of at least two integrally bonded components (10) produced according to the method of this type.

The invention discloses a nanoparticle capturing method and related equipment, and the method comprises the following steps: uniformly covering a hydrogel solution on a sample liquid drop containing target nanoparticles on a glass slide to form a standard observation system; the hydrogel solution is temperature sensitive type hydrogel; determining a local area where the target nanoparticles are located in a standard observation system; starting a laser, controlling the laser to irradiate the local area, and regulating and controlling the laser power density of the laser, so that the temperature of the local area reaches and is maintained at the phase change temperature of the hydrogel solution; and adjusting laser parameters of the laser to generate stable hydrogel at the position of the target nanoparticle. According to the embodiment of the invention, the nano-particles can be captured by utilizing the characteristics of the temperature-sensitive hydrogel and combining a simple photo-thermal device, the influence caused by the limitation of capturing environment conditions or capturing sample properties is reduced, and the method can be widely applied to the technical field of nano-particle capturing.

The application provides a coating material and a laser cladding process for steam turbine blade water erosion resistance, and the mass percentage of each component of the coating material is as follows: C: 0.65-0.80wt%, Cr: 3.00-6.50wt%, Mn: 0.22-0.55wt%, Nb: 0.30-0.80wt%, Mo: 4.00-8.50wt%, Si: 0.1-0.3wt%, W: 5.00-8.00wt%, V: 1.50-2.50wt%, Al: 0.40-0.60wt%, and the balance is Fe and a small amount of impurity elements. The laser power density in the cladding process is 100-150W / mm 2 , argon is used to protect the molten pool, the powder feeding amount is 40-60r / min, and the multi-pass lap rate is 30-50%. The coating material provided by the application has the characteristics of high toughness, not easy to produce pores and excellent water erosion resistance. The cladding layer prepared from the coating material has high water erosion resistance and good comprehensive mechanical properties.

This invention provides a miniaturized high-pulse-energy Raman laser under vortex optical pumping conditions, relating to the field of Raman laser technology, and employing n 2 A square array of vortex phase plates serves as the optical element for generating vortex-pumped lasers. By adjusting parameters such as the topological charge of the array of vortex phase plates and the focal length of the array of short-focal-length lenses, the laser power density in the focal region is reduced. The focal region has n 2 A square array is arranged with ring-shaped light intensity distribution units, ensuring that the laser power density of each unit in the focal region is greater than the Raman laser generation threshold and less than the laser-induced breakdown threshold. Therefore, the total Raman laser energy is n times the Raman laser energy generated by each unit. 2 This technology ultimately enabled the output of high-energy, high-beam-quality Raman lasers, with Raman laser pulse energies reaching hundreds of millijoules or even joules.

The invention provides a far-field laser measuring device, which relates to the technical field of laser parameter measurement and comprises a filter wheel rotating system, a laser power density detection module, a pulse width detection module and an upper computer. The filter wheel rotating system comprises a pulse width detection window and a plurality of laser wavelength detection windows; and the upper computer is used for controlling the filter wheel rotating system to rotate and receiving detection data acquired by the laser power density detection module and the pulse width detection module. The rotating filter wheel rotating system is matched with the laser power density detection module and the pulse width detection module, so that laser power density detection and laser pulse width detection processes are realized. When irradiated by laser, the laser power density detection module captures the laser at the first time, rotates based on the filter wheel rotating system, receives detection data acquired by the laser power density detection module and detection data acquired by the pulse width detection module, and realizes the rapid and accurate measurement process of laser with different wavelengths.

The invention provides a pulse laser induced high-ionization magnetron sputtering and ion energy control method and device, and relates to the technical field of magnetron sputtering coating. The control method comprises the following steps: S1, mounting a target material and a substrate in place in a vacuum chamber, sealing the vacuum chamber, and vacuumizing the vacuum chamber to a vacuum state; s2, argon is introduced into the vacuum chamber, and the working air pressure is controlled to be stabilized at a preset value; turning on an anode power supply to supply power to the target material, and grounding the chamber wall of the vacuum chamber; s3, the surface of the target material is scanned according to a preset path after the pulse laser is controlled to be focused, secondary electron emission is excited, and the ionization rate of sputtering metal atoms in the plasma is increased; plasma density data are synchronously monitored in real time, and the laser power density is dynamically adjusted based on a preset plasma density threshold value; and S4, establishing an electric field, accelerating the positively charged target material ions to move towards the substrate under the action of the electric field, and depositing on the surface of the substrate to form a coating film.

The invention relates to the technical field of alloy materials, in particular to a Cr-Fe functional alloy material for prolonging the service life of a gun barrel and a preparation method thereof.The alloy comprises, by mass, 74%-78% of Cr, 22%-56% of Fe and 0.5%-1.2% of C. The microstructure is mainly composed of a BCC phase (larger than or equal to 85%), and Cr23C6 strengthening phases (3%-8% and 0.2-3.0 microns) are evenly separated out. During preparation, laser remelting is conducted on a pre-plated hard chromium base body under nitrogen protection, the laser power density is 4.95 * 10 < 4 >-9.20 * 10 < 4 > W / cm < 2 >, the scanning speed is 5-80 mm / s, preheating is conducted to 400 DEG C, and gradient cooling is conducted; the integrated visual system regulates and controls parameters in real time, the depth-to-width ratio of a molten pool is guaranteed to be 1: 1.5-1: 2.5, and the Cr / Fe distribution standard deviation is smaller than or equal to 5%. The interface dislocation density of the alloy is larger than or equal to 1 * 10 < 14 > m <-2 >, the high-temperature abrasion mass loss is smaller than or equal to 0.01 g, the abrasion resistance is three times that of original hard chromium, and the service life of a gun barrel is remarkably prolonged.

The invention relates to the technical field of additive manufacturing interface metallurgical bonding strength real-time improvement scheme design, in particular to a multi-material additive manufacturing interface metallurgical bonding strength real-time improvement method and system. The method comprises the following steps: synchronously capturing an interface thermal-mechanical coupling state through a multi-mode sensing system; calculating the solid solubility and the crack sensitivity coefficient based on a thermodynamic model; double-loop intelligent control is triggered, a feedforward module predicts an energy compensation strategy according to a material database and activates nano activated particles to intervene, and a feedback module adopts reinforcement learning to optimize energy parameters; and injecting functionalized nano-powder into the interface and accurately adjusting the laser power density to a critical value. The system comprises a multi-physical field sensing module, a real-time decision center and a microcell energy regulation and control unit. The method has the core advantages that a dynamic black box in the heterogeneous material interface metallurgy process is broken; the in-situ active regulation and control of the material compatibility are realized; precise adaptation of a micron-scale energy field is achieved. And the interface metallurgy quality and the member service reliability are obviously improved.

The present application provides a kind of optical fiber jumper, the optical fiber jumper includes optical fiber connector, light receiver, fixed cap, core, optical fiber coating and adhesive, the light receiver is placed in the optical fiber connector, the fixed cap is connected with the optical fiber connector, the core is inserted into the optical fiber connector and the light receiver, the adhesive is coated between the optical fiber connector and the optical fiber coating.Light receiver is not damaged by not absorbing laser, and the laser beam is uniformly transmitted for a distance therein, since the laser beam is divergent and the refractive index of the light receiver is gradually changed, the laser beam is irradiated to the optical fiber connector with a larger divergence angle, at this time, the laser power density is significantly reduced, so that the laser connector only generates heat, without damage.

The invention relates to the technical field of laser processing, and particularly discloses an aircraft frame beam fillet structure in-situ laser shock peening process method which comprises the following steps: obtaining an unshielded range in the incident direction of a laser beam according to the structural characteristics of a non-detachable frame beam and the spatial position characteristics of a fillet; the orientation relation between the incident direction of the laser beam and the rounded corner structure is established by combining the size characteristics of the non-shielding range and the rounded corner structure, and the optimal orientation of the incident direction of the laser beam is obtained; designing gradient laser power density; and the gradient light spot size is designed, and the optimal light spot size is obtained. Laser shock peening process parameters are designed on the basis of spatial structure characteristics and size structure characteristics of the aircraft frame beam fillet, so that interference of the spatial structure characteristics of the aircraft frame beam to laser beams is avoided, and meanwhile, a peening effect meeting fatigue gain requirements can be achieved on a fillet curved surface; therefore, a preferable implementation process with the best coordination of the fatigue gain effect and the strengthening processing mode is obtained.

The disclosure relates to a laser conditioning method (2) for a nonlinear optical crystal in which the nonlinear optical crystal is irradiated by a laser with a photon energy from Eg / 2 to Eg, where Eg is the band gap of the crystal. Comparative results show that when the 266 nm laser (2), which is much weaker than the 355 nm laser, is used, and provided that the laser power density is only 0.13 GW / cm², the zero probability volume damage threshold is 120% higher than that before conditioning. The laser conditioning for a potassium dihydrogen phosphate (KDP) crystal based on two-photon absorption according to the disclosure has higher conditioning efficiency and greater potential for improving the crystal volume damage threshold than the three-photon absorption laser conditioning.

The application relates to the technical field of industrial control, in particular to an embedded real-time operating system deployment method and system for industrial control. The method comprises the following steps: laser processing control point division is performed on a workpiece to be processed to generate laser control point coordinate data; laser beam testing is performed according to the laser control point coordinate data, and an embedded real-time operation monitoring network is deployed to perform monitoring signal synchronous collection to obtain laser pre-scanning monitoring data; theoretical focal point position adjustment and laser power density processing are performed according to the laser pre-scanning monitoring data, and real-time laser thermal processing operation is performed on the workpiece to be processed to obtain a real-time thermal gradient vector field; and real-time regulation and control of the industrial processing control process is performed according to the real-time thermal gradient vector field to realize industrial processing real-time operation system deployment. The embedded real-time operation system is used to realize real-time operation control of the industrial laser processing process, and the processing precision and efficiency are significantly improved.

The invention relates to the technical field of battery preparation, in particular to a preparation method of a miniature aluminum-air battery, which comprises the following steps: acquiring key parameters in real time; calculating a risk characterization index; abnormal judgment; determining an aluminum powder behavior state and a sintering behavior state, and identifying an activity non-uniform region; judging abnormal conduction to obtain material distribution deviation; conducting type judgment to obtain energy or interface deviation; adjusting laser power density or polarization voltage; and correcting the risk index according to the adjustment timestamp. According to the invention, real-time acquisition and correlation analysis of multi-source parameters are introduced in the whole process of battery preparation, so that whole-process dynamic monitoring and regulation from raw material behavior, forming state to interface reaction process are realized; the problems of low battery efficiency and short service life caused by unstable electrode performance due to non-uniform powder dispersion and inconsistent film thickness are effectively solved.

A method for the laser welding of two conductor pieces includes providing an elongated first conductor piece having a first end section and a first end face, and providing an elongated second conductor piece having a second end section and a second end face. The first end face is arranged adjacent to the second end face. The method further includes generating at least two laser spots on the first end face and / or the second end face. Each of the at least two laser spots has a core region and a ring region. An average laser power density in the core region is higher than an average laser power density in the ring region. The method further includes moving the at least two laser spots. The at least two laser spots generate a common melt pool that extends at least partially over the first end face and the second end face.