Dual-beam compound ring laser directed energy deposition processing head and method

Abstract

The present application relates to the technical fields of laser directed energy deposition (L-DED) additive manufacturing, and particularly relates to a double-beam composite annular laser directed energy deposition processing head and method. A first convex cone lens, a dichroic mirror, a flat convex axicon, a fifth reflecting plane mirror, an integrated mirror group unit, a focusing lens and a plane window mirror are sequentially arranged on the light path of the first incident laser; the second incident laser is incident on the dichroic mirror through a second convex cone lens; the integrated mirror group unit comprises a reflecting prism and four reflecting plane mirrors arranged around the reflecting prism. The double-beam beam combining is realized through the dichroic mirror, the annular transformation of the double-beam is realized through the shared flat convex axicon, and the integration of beam splitting and beam combining is realized through the integrated mirror group unit, so that the double-beam composite of blue light and near-infrared laser is realized under the premise of maintaining the original optical inner center coaxial feeding function of the annular laser processing head, and the structure is compact and the optical adjustment is convenient.

Description

Technical Field

[0001] This invention relates to the field of laser-directed energy deposition (L-DED) additive manufacturing technology, and in particular to a dual-beam composite ring laser-directed energy deposition processing head and method. Background Technology

[0002] Ring laser directed energy deposition is an advanced additive manufacturing technology that uses a hollow ring laser beam as a heat source and is formed by coaxial coupling of laser-powder or laser-wire. Compared with other laser directed energy deposition technologies, ring laser directed energy deposition technology has the following characteristics: (1) The ring-focused spot and the converged powder beam or wire have a high degree of matching and are not constrained by the laser scanning processing direction; (2) The laser energy distribution in the deposition spot area on the surface of the substrate to be processed is uniform, the material is fully heated, and the quality of the cladding deposition layer is good; (3) The utilization rate of the deposited material is high, especially the powder material. By controlling the powder beam, the powder utilization rate can be greatly improved, while reducing environmental pollution; (4) Since the focused laser beam, the powder (or wire bundle), and the protective gas nozzle can be arranged in an axisymmetric manner, the beam of light-gas-powder (or wire bundle) is concentrated, the atmosphere protection effect of the molten pool is good, and the oxidation degree is low.

[0003] For example, a Chinese invention patent discloses a ring-shaped laser metal deposition head device for coaxial monitoring of molten pool morphology and temperature. It can realize ring-shaped focused laser processing with coaxial wire or powder feeding at the center of the laser beam, while simultaneously monitoring the morphology and temperature changes of the molten pool region in real time.

[0004] The existing ring laser processing head devices mainly use a single-band processing laser, typically a near-infrared laser in the 900-1100nm band. For laser additive manufacturing of high-reflectivity materials such as copper and aluminum alloys, near-infrared laser processing presents a series of technological challenges. Copper and aluminum have very low absorption rates in the near-infrared band, with copper's reflectivity reaching approximately 95%. Due to the low laser absorption rate and high thermal conductivity of these materials, coupled with the Gaussian distribution of focused laser energy, problems such as unstable molten pools, severe material burn-off, and numerous internal pore defects in the formed parts are easily encountered during actual processing. To address this issue, in recent years, the industry has begun to experiment with using blue lasers with wavelengths around 450nm or green lasers with wavelengths around 530nm to process high-reflectivity materials. The absorption rates of blue and green lasers on the surface of materials such as copper and its alloys are significantly higher than those of near-infrared lasers. Currently, there are many commercially available high-energy blue lasers with power greater than 1000W, while the application of high-power green lasers in laser-directed energy deposition is still relatively limited. This is mainly because there are few reports on high-energy green lasers with power greater than 1000W and their cost is high. Laser-directed energy deposition technology based on the combination of blue and near-infrared laser beams has been attempted for processing materials such as copper alloys. The basic idea is to combine the high absorption rate of blue lasers with the high energy density of infrared lasers to balance processing efficiency and forming quality.

[0005] However, achieving dual-beam combining of blue and near-infrared lasers within the existing framework of ring laser-guided energy deposition (PED) heads presents challenges in optical system design. The optical systems of existing ring laser heads are primarily designed for processing single-wavelength lasers. Each optical component, such as the collimation-ring unit, beam splitter, reflection and deflection unit, and beam combiner, is coated and optimized for a specific wavelength. Introducing a second laser beam of a different wavelength requires adding additional optical elements and pathways to the existing optical path, while ensuring coaxiality and beam quality after combining the two beams. Currently known PED head devices for combining blue and near-infrared lasers typically employ a central solid Gaussian laser coupled with an outer annular slit powder nozzle or a uniformly distributed array of 3 to 5 powder nozzles. This approach does not utilize the optical path structure of a ring laser, and compared to a ring laser, a solid laser with a Gaussian energy density distribution is inferior in terms of energy distribution uniformity and optical-material coupling matching. Furthermore, for laser-directed energy deposition (EDD) head devices for filament or powder materials, existing solutions employ a central filament or powder feed combined with multiple solid Gaussian laser beams evenly distributed on the outer sides, focusing inwards. This multi-laser-beam approach requires the integration of multiple lasers and multiple optical fiber outputs, placing high demands on the consistency of laser beam quality and the calibration of the optical-mechanical structure of the processing head. Improving the uniformity of energy distribution in the final focused spot from multiple beams is challenging, and achieving coaxial arrangement of the optical paths for sensors monitoring molten pool morphology and temperature is also difficult.

[0006] Therefore, how to achieve the combination of blue light and near-infrared laser beams in a ring laser directional energy deposition head, while maintaining the original coaxial powder or filament feeding function of the ring laser head and its compact structural dimensions, is a technical problem that needs to be solved. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the purpose of this invention is to provide a dual-beam composite ring laser directional energy deposition head and method. The aim is to achieve composite ring focusing of two high-energy lasers of different wavelengths through reasonable optical path design, thereby improving the laser directional energy deposition processing quality of high-reflectivity materials such as copper alloys.

[0008] To achieve the above objectives, the embodiments of the present invention provide the following technical solutions: In a first aspect, embodiments of the present invention provide a dual-beam composite annular laser directional energy deposition processing head: The optical path of the first incident laser is sequentially provided with a first convex conical lens, a dichroic mirror, a plano-convex axial conical mirror, a fifth reflecting plane mirror, an integrated reflecting mirror unit, a focusing lens, and a plane window mirror; The second incident laser is incident on the dichroic mirror through the second convex conical lens and shares the same mirror group as the first incident laser. The mirror group includes a plano-convex axial conical mirror, a fifth reflecting plane mirror, an integrated reflecting mirror group unit, a focusing lens, and a plane window mirror. The optical axes of the two optical paths overlap on the shared mirror group. The dichroic mirror is arranged at an angle to transmit the first incident laser and reflect the second incident laser. The fifth reflecting plane mirror is arranged at an angle, with its reflecting surface facing the plano-convex axial cone mirror and the integrated reflecting mirror unit. The integrated reflector unit includes a reflector prism and four reflector plane mirrors symmetrically arranged around the reflector prism. The reflector surface of the reflector prism faces the reflector plane mirror and the surface of the substrate to be processed. The reflecting prism, focusing lens, and plane window mirror have through holes in their middle positions for the feeding pipeline assembly to pass through.

[0009] Secondly, embodiments of the present invention also provide a dual-beam composite ring laser directional energy deposition processing method: The first incident laser beam is guided into the first convex conical lens and forms a first conical beam; the second incident laser beam is guided into the second convex conical lens and forms a second conical beam. The first conical beam is transmitted through a dichroic mirror, and the second conical beam is reflected by the dichroic mirror and then redirected. The first conical beam transmitted through the dichroic mirror and the second conical beam reflected by the dichroic mirror pass coaxially through a plano-convex axial conical mirror to form the first hollow ring laser beam and the second hollow ring laser beam, respectively. The first and second hollow ring laser beams are reflected by the tilted fifth reflecting plane mirror and then turned, and are incident on the two prismatic reflecting surfaces of the reflecting prism. They are then divided into a front half-ring beam and a rear half-ring beam by the two prismatic reflecting surfaces of the reflecting prism. The first hollow ring laser beam's front and rear half-ring beams are each reflected by two reflecting plane mirrors and return to a reflecting prism. They are combined in the beam-combining area of ​​the two prismatic reflecting surfaces of the reflecting prism to form the first hollow ring beam. The beam-combining area is offset from the beam-splitting area by a certain distance. The second hollow ring laser beam's front and rear half-ring beams are each reflected by two reflecting plane mirrors and return to a reflecting prism. They are combined in the beam-combining area of ​​the two prismatic reflecting surfaces of the reflecting prism to form the second hollow ring beam. The through-hole of the reflecting prism is located in the center of the beam-combining area. The first hollow annular beam and the second hollow annular beam pass coaxially through a focusing lens and a plane window mirror, and converge near the surface of the substrate to be processed to form the first annular focused laser spot and the second annular focused laser spot, respectively. Metal wire or gas-metal powder mixture is fed to the surface of the substrate to be processed, so that the metal wire or gas-metal powder mixture is coaxially coupled with the first annular focused laser spot and / or the second annular focused laser spot to act on the surface of the substrate to be processed.

[0010] One or more technical solutions provided in the embodiments of the present invention have at least the following technical effects or advantages: This invention employs a dichroic mirror to combine two laser beams of different wavelengths at the beginning of the optical path. Thereafter, the two laser beams share the same set of optical mirrors, eliminating the need for a separate complete optical path for the second laser beam. Furthermore, the two laser beams share the same plano-convex axial conical mirror to complete the ring beam transformation, ensuring the coaxiality and beam parameter consistency of the two beams after the ring transformation. The integrated reflector unit combines beam splitting, refraction, and beam combining functions into one unit. The ring beam can be split, redirected, and recombined through the cooperation of one reflecting prism and four reflecting plane mirrors, achieving structural compactness while maintaining optical accuracy. A through-hole is provided between the reflecting prism, focusing lens, and plane window mirror for the feeding pipeline assembly to pass through, maintaining the original coaxial powder or wire feeding function of the ring laser processing head. Other mirror groups do not require openings, minimizing lens processing costs. This invention achieves dual-beam recombination within a ring laser optical path structure through the design of an integrated beam splitting-folding-combining mirror unit and a dual-beam common optical path transmission scheme. This reduces the number of optical components and shortens the optical path length, thereby effectively controlling the overall size of the processing head. The outer envelope size is significantly reduced compared to commercially available products in the same field, resulting in a substantial reduction in overall volume. The total optical path length of the dual beams from the fiber incident point to the surface of the substrate to be processed is also effectively controlled, resulting in a shorter optical path. Compared to existing technologies, without the addition of molten pool image and temperature detection optical path units, the processing head of this invention is smaller in both length and width dimensions than known products in the same field, resulting in a more compact overall structure.

[0011] Advantages of additional aspects of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0012] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. The drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In addition, the dimensions or spacing between the components are exaggerated to show the position of each component, and the schematic diagrams are for illustrative purposes only.

[0013] Figure 1This is a schematic diagram of a dual-beam composite ring laser directional energy deposition processing head and its optical path transmission, provided as an embodiment of the present invention.

[0014] Figure 2 This is a schematic diagram of the integrated beam splitting-folding-combining reflector unit provided in an embodiment of the present invention.

[0015] Figure 3 This is a schematic diagram of the plano-convex axial cone mirror structure provided in an embodiment of the present invention.

[0016] Figure 4 This is a schematic diagram of a convex conical lens structure provided in an embodiment of the present invention.

[0017] In the figure: 1. First incident laser; 2. First convex conical lens; 3. First incident laser reflector; 4. Dichroic mirror; 5. Reflecting prism; 6. First reflecting plane mirror; 7. Second reflecting plane mirror; 8. Third reflecting plane mirror; 9. Fourth reflecting plane mirror; 10. Second incident laser; 11. Second convex conical lens; 12. Plano-convex axial conical mirror; 13. Fifth reflecting plane mirror; 14. Focusing lens; 15. Plane window mirror; 16. Feeding pipeline assembly; 17. Surface of the substrate to be processed; Detailed Implementation To more clearly illustrate the technical solutions of the embodiments in this specification, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are merely some examples or embodiments of this specification. For those skilled in the art, these drawings can be applied to other similar scenarios without creative effort. Unless obvious from the linguistic context or otherwise specified, the same reference numerals in the drawings represent the same structures or operations.

[0018] Generally speaking, the terms "comprising" and "including" only indicate that the steps and elements that have been explicitly identified are included, and these steps and elements do not constitute an exclusive list. The method or apparatus may also include other steps or elements.

[0019] Example 1 Ring laser directed energy deposition (RED) technology faces significant challenges in processing highly reflective materials such as copper and aluminum alloys. These materials exhibit very low absorption rates in the near-infrared band; for example, copper has a reflectivity of approximately 95%, which can easily lead to unstable molten pools, severe material burn-off, and numerous internal porosity defects in the formed parts. Although the absorption rate of blue laser light on the surface of materials such as copper and its alloys is significantly higher than that of near-infrared laser light, achieving dual-beam combination of blue and near-infrared laser light in a ring laser processing head while maintaining coaxial powder or wire feeding at the center of the beam and a compact structural dimension remains an unsolved technical problem in current technology.

[0020] This invention addresses the aforementioned technical problems by proposing a compact solution for a dual-beam composite ring laser directional energy deposition processing head using infrared and blue light. This head enables high-quality ring-focused laser processing of materials such as copper and aluminum alloys with coaxial wire or powder feeding within the optical center. The invention integrates the ring beam splitting, folding, and combining functions into a single integrated reflector unit. Furthermore, the infrared and blue light beams are combined after passing through a dichroic mirror. In particular, sharing a single plano-convex axial cone mirror enables the shaping of two different wavelength laser beams into a ring shape, with the longitudinal distance between their focal points being less than 4 mm. This design results in a compact overall structure, a reduced number of optical lenses, easier optical adjustment, and improved beam quality in the focused area.

[0021] like Figure 1 As shown, the dual-beam composite ring laser directional energy deposition processing head includes: a first convex conical lens 2, a dichroic mirror 4, a plano-convex axial conical mirror 12, a fifth reflecting plane mirror 13, an integrated reflecting mirror unit, a focusing lens 14, and a plane window mirror 15, sequentially arranged along the optical path of the first incident laser 1. The second incident laser 10 is incident on the dichroic mirror 4 through the second convex conical lens 11. The dichroic mirror 4 is tilted to transmit the first incident laser 1 and reflect the second incident laser 10. The fifth reflecting plane mirror 13 is tilted, with its reflecting surface facing the plano-convex axial conical mirror 12 and the integrated reflecting mirror unit. Figure 2 As shown, the integrated reflector unit includes a reflecting prism 5 and four reflecting plane mirrors symmetrically arranged around the reflecting prism 5: a first reflecting plane mirror 6, a second reflecting plane mirror 7, a third reflecting plane mirror 8, and a fourth reflecting plane mirror 9. The reflecting surface of the reflecting prism 5 faces the first reflecting plane mirror 6, the second reflecting plane mirror 7, the third reflecting plane mirror 8, the fourth reflecting plane mirror 9, the fifth reflecting plane mirror 13, and the surface 17 of the substrate to be processed. A through hole is provided at the center of the reflecting prism 5, the focusing lens 14, and the plane window mirror 15 for the feeding pipeline assembly 16 to pass through.

[0022] The dichroic mirror 4 is the core component for achieving two-beam recombination. Also known as a dichroic mirror or beam splitter, the dichroic mirror 4 works based on the thin-film interference effect of light, selectively achieving high transmission or high reflection in specific wavelength bands. In this embodiment, the dichroic mirror 4 is tilted, exhibiting high transmittance for the first incident laser 1 and high reflectivity for the second incident laser 10. This arrangement allows the two laser beams of different wavelengths to be combined after passing through the dichroic mirror 4. Subsequently, the two laser beams share the same optical path, including a plano-convex axial conical mirror 12, a fifth reflecting plane mirror 13, an integrated reflecting mirror unit, a focusing lens 14, and a plane window mirror 15. This shared optical path design reduces the number of optical components, making the overall structure more compact.

[0023] The first convex conical lens 2 works in conjunction with the plano-convex axial conical lens 12, maintaining a certain distance between them, typically 40mm to 200mm. The convex surface of the first convex conical lens 2 faces the incident laser to collimate it, while its other surface is an outwardly convex conical surface. The laser beam, after passing through the convex surface of the first convex conical lens 2, forms a collimated circular beam. After passing through the conical surface of the lens, it forms an inwardly converging conical parallel beam, which then passes through the dichroic mirror 4 and the plano-convex axial conical lens 12, ultimately forming a collimated hollow annular beam. The second convex conical lens 11 works in conjunction with the same plano-convex axial conical lens 12, causing the second incident laser 10 to also form a hollow annular laser beam. The two laser beams share a single plano-convex axial conical lens 12, achieving the transformation into an annular beam. This not only reduces the number of lenses but also ensures the coaxiality of the two laser beams during beam transformation.

[0024] The integrated reflector unit includes a reflecting prism 5 and four reflecting plane mirrors symmetrically arranged around it. A hollow ring laser beam, reflected by the fifth reflecting plane mirror 13, exits vertically upwards and is incident on the beam-splitting region of the two prismatic reflecting surfaces of the reflecting prism 5 at a 90° angle. There, it is split into a front half-ring beam and a rear half-ring beam. The two half-ring beams are then refracted horizontally to the first reflecting plane mirror 6 and the second reflecting plane mirror 7, respectively. After being reflected by the third reflecting plane mirror 8 and the fourth reflecting plane mirror 9, they return to the reflecting prism 5, where they combine into a single hollow ring beam in the beam-combining region of the two prismatic reflecting surfaces. This design integrates beam splitting and beam combining functions into a single reflecting prism 5, ensuring optical accuracy while achieving structural compactness. More importantly, this series of reflections and refractions effectively avoids the feeding pipeline assembly 16, preventing the laser from irradiating it.

[0025] Through holes are provided at the center positions of the reflecting prism 5, focusing lens 14, and plane window mirror 15. The through hole of the reflecting prism 5 is located at the center of the beam-combining region, while the through holes of the focusing lens 14 and plane window mirror 15 are located at the center of the lenses. The feeding pipeline assembly 16 passes through these through holes to reach the vicinity of the substrate surface 17 to be processed. The axis of the feeding pipeline assembly 16 is coaxial with the center of the annular focused laser spot, realizing coaxial powder or filament feeding within the optical center. This coaxial arrangement ensures a high degree of matching between the annular focused laser spot and the converging powder beam or filament, is not constrained by the laser scanning processing direction, results in uniform laser energy distribution in the deposition spot area on the substrate surface 17, sufficient material heating, and good cladding deposition layer quality.

[0026] The dual-beam combination is achieved by using a dichroic mirror 4, the ring transformation of the dual beams is achieved by using a shared plano-convex axial cone mirror 12, and the beam splitting and combining are integrated by using an integrated reflector unit. Thus, while maintaining the original coaxial powder or wire feeding function of the ring laser processing head, the dual-beam combination of blue light and near-infrared laser is realized. The structure is compact and the optical adjustment is convenient.

[0027] In another embodiment, a first incident laser reflector 3 is also provided in the optical path of the first incident laser 1, and the first incident laser reflector 3 is located between the optical paths of the first convex conical lens 2 and the dichroic mirror 4.

[0028] In embodiments where the first incident laser reflector 3 is not required, the first incident laser 1 can directly exit from the first convex conical lens 2 and then enter the dichroic mirror 4. In embodiments where the first incident laser reflector 3 is required, the first incident laser reflector 3 is arranged at an angle, typically 45°, to redirect the beam emitted from the first convex conical lens 2 by 90° before directing it towards the dichroic mirror 4. The reflector allows for flexible adjustment of the optical path according to the overall layout of the processing head, making the structural design of the processing head more flexible.

[0029] The first convex conical lens 2 and the plano-convex axial conical lens 12 constitute the first hollow annular laser beam mirror unit. For example... Figure 4 As shown, the convex surface of the first convex conical lens 2 is either spherical or aspherical, facing the incident laser beam, while its other surface is an outwardly convex conical surface with a cone angle of 110° to 160°. Figure 3 As shown, the cone angle of the outer convex conical surface of the plano-convex axial conical lens 12 is 110° to 160°. In the same embodiment, the cone angles of the two can be the same or slightly different. This conical surface is arranged coaxially with the conical surface of the first convex conical lens 2. It can be understood that the coaxiality here does not refer to the geometric coaxiality of the objects. Since there are cases where the light path is reflected and turns by 90 degrees, the coaxiality here can be understood as the optical axis overlapping. The other optical surface of the plano-convex axial conical lens 12 is a plane. The convex surface of the first convex conical lens 2 is used to collimate the incident laser, and its collimating focal length is 40mm to 200mm. The beam collimated by the convex surface passes through the conical surface again to form an inwardly converging conical parallel beam. This conical parallel beam is then incident on the conical surface of the plano-convex axial conical lens 12, and after exiting the plano-convex axial conical lens 12, it forms a collimated hollow annular beam, in which the inner ring diameter of the hollow annular laser beam is 10mm to 40mm.

[0030] The second convex conical lens 11 and the plano-convex axial conical lens 12 constitute the second hollow annular laser beam mirror unit. The convex surface of the second convex conical lens 11 is spherical or aspherical, facing the incident laser, and its other surface is an outwardly convex conical surface with a cone angle of 110° to 160°. This conical surface is arranged coaxially with the conical surface of the second convex conical lens 11. The collimating focal length of the second convex conical lens 11 is 40mm to 200mm, and the inner ring diameter of the formed hollow annular laser beam is 10mm to 40mm.

[0031] The second hollow annular laser beam mirror unit shares the same plano-convex axial conical mirror 12 with the first hollow annular laser beam mirror unit. After the two laser beams of different wavelengths pass through their respective convex conical lenses, they both complete the transformation from solid beams to annular beams through the same plano-convex axial conical mirror 12. This not only reduces the number of optical elements, but more importantly, it ensures that the two laser beams have good coaxiality after beam transformation, laying a good foundation for subsequent beam combining and focusing.

[0032] like Figure 2 As shown, the normal vectors of the four reflecting plane mirrors in the integrated reflector unit are coplanar, and the normals of any two adjacent reflecting surfaces are perpendicular to each other. The normal line of any reflecting surface of the four reflecting plane mirrors forms a 45° angle with the edge line of the reflecting prism 5, and the edge angle of the reflecting prism 5 is a 90° right angle.

[0033] The edge line at the 90° intersection of the reflecting prism and the two parallel bottom edges are projected onto the reflecting surface of any reflecting plane mirror. The projected lines all fall on this reflecting surface, ensuring that light reaches each reflecting surface after reflection and preventing it from escaping without passing through the reflecting surface. The length of the edge line at the 90° intersection of the reflecting prism is 60 to 200 mm. The reflectivity of the reflecting prism and the four reflecting plane mirrors for the 400-500 nm and 900-1100 nm dual-band wavelengths is not less than 95%. The reflectivity of the left optical surface of the dichroic mirror 4 for the second incident laser is not less than 95%, and the transmittance of the left and right optical surfaces of the dichroic mirror 4 for the first incident laser is not less than 95%.

[0034] The focusing lens 14 consists of one aspherical lens or two separate spherical lenses, with a focal length of 60mm to 300mm and a central aperture diameter of 8mm to 20mm. When using one aspherical lens, one of its transmission surfaces is an even-order aspherical surface, and the other is a spherical, planar, or even-order aspherical surface. When using two separate spherical lenses, it consists of one biconvex lens and one meniscus lens, with the convex surface of the meniscus lens facing the substrate surface 17, and the concave surface of the meniscus lens adjacent to one of the convex surfaces of the biconvex lens. The focusing lens 14 has a transmittance of not less than 95% for both the 400-500nm and 900-1100nm wavelength bands.

[0035] The plane window mirror 15 is composed of one or two plane glass mirrors with a thickness of 2mm to 8mm. The plane window mirror 15 is positioned behind the focusing lens 14 and close to the surface 17 of the substrate to be processed, protecting the internal optical components from contamination by spatter and dust generated during processing.

[0036] The first incident laser 1 is an infrared laser in the 900nm to 1100nm wavelength range or a blue laser in the 400nm to 500nm wavelength range. Correspondingly, the second incident laser 10 is a blue laser in the 400nm to 500nm wavelength range or an infrared laser in the 900nm to 1100nm wavelength range, and their wavelength ranges do not overlap. The numerical aperture of the input optical fiber used for the first and second incident lasers ranges from 0.06 to 0.22, and the core diameter ranges from 50 to 600 μm. After the first and second incident lasers are focused by the focusing lens, the longitudinal distance between their focal points is less than 4 mm.

[0037] One of the two incident laser beams is an infrared laser, and the other is a blue laser. Combining the low cost and high energy density of infrared lasers with the high absorption rate of blue lasers allows for a balance between processing efficiency and forming quality when machining highly reflective materials such as copper and aluminum alloys.

[0038] The feed line assembly 16 has a central circular hole for passing a gas-metal powder mixture to form a powder jet, or for passing a metal wire. The minimum diameter of the central circular hole ranges from 0.6 mm to 2 mm.

[0039] When powder materials are used, compressed gas carries metal powder and is ejected through the central hole of the feeding pipeline assembly 16 to form a powder jet. The powder jet and the annular focused laser spot are coaxially coupled and act on the surface 17 of the substrate to be processed. When wire materials are used, the wire feeding mechanism transports the metal wire to the processing area through the central hole of the feeding pipeline assembly 16.

[0040] Working principle: The optical path transmission process of the first incident laser 1 is as follows: The first incident laser 1 is transmitted to the processing head through the optical fiber connecting the laser. After passing through the spherical (or aspherical) surface of the first convex conical lens 2 from right to left, it forms a collimated circular beam. After passing through the conical surface of the lens, it forms an inwardly converging conical parallel beam. After passing through the reflective surface of the first incident laser reflector arranged at a 45° angle, it turns 90° to the left and is transmitted through the dichroic mirror 4, and then through the plano-convex axial conical mirror 12. The first convex conical lens 2 and the plano-convex axial conical mirror 12 need to have a certain distance. After the laser passes through the plano-convex axial conical mirror 12, it forms a collimated hollow annular beam. Then it is incident on the upper surface of the fifth reflecting plane mirror 13 arranged at a 45° angle, and is reflected 90° upward. It is then vertically incident from bottom to top onto the reflecting edge. After the two prismatic reflective surfaces of mirror 5 form a 90° angle, the light beams are reflected and split into two semi-circular beams. Each beam is then reflected vertically along the horizontal direction to the first reflecting plane mirror 6 and the second reflecting plane mirror 7, respectively. Then, each beam is reflected again along the horizontal direction at a 90° angle to the right and to the third reflecting plane mirror 8 and the fourth reflecting plane mirror 9. After that, each beam is reflected again along the horizontal direction at a 90° angle to the center and to the reflecting prism 5. The two semi-circular beams are combined into a hollow ring beam on the reflecting prism 5. After being reflected by the two prismatic reflective surfaces of mirror 5 forming a 90° angle (the same reflective surfaces as the aforementioned prismatic reflective surfaces, only the contact position of the light has changed), the light beams are incident vertically downwards onto the focusing lens 14 and the plane window mirror 15, and finally converge near the surface of the processed substrate to form a focused ring beam.

[0041] The optical path transmission process of the second incident laser 10 is as follows: The second high-energy laser, incident through the optical fiber, first passes through the second convex conical lens at the entrance port to form a ring-shaped parallel laser beam, which is then reflected vertically downwards through a 45°... ° The beam is reflected and refracted after being tilted by a dichroic mirror. It passes horizontally to the left through a plano-convex axial conical mirror with its conical surface facing right, forming a hollow ring laser beam. After being reflected by a fifth reflecting plane mirror tilted at 45°, it exits vertically upward. It then enters the two prismatic reflecting surfaces of the reflecting prism 5 at a 90° angle, where it is reflected and splits into two semi-ring beams. These beams are refracted vertically along the horizontal direction to the first reflecting plane mirror 6 and the second reflecting plane mirror 7, respectively. Then, they are reflected again at 90° along the horizontal direction and refracted to the right to the third reflecting plane mirror 8 and the fourth reflecting plane mirror 9. Finally, they are reflected again at 90° along the horizontal direction and refracted towards the center to the reflecting prism 5. The two semi-ring beams are combined into a hollow ring beam on the reflecting prism 5, and after being reflected by the two prismatic reflecting surfaces of the reflecting prism 5, they are incident vertically downward to the focusing lens and the plane window mirror, ultimately forming a second ring-shaped focused laser spot that converges towards the center.

[0042] Through the design of this invention, the outer envelope size of the laser processing head can be reduced to 320mm*260mm*190mm or even smaller. The total optical path of the infrared and blue light dual beams from the fiber incident point to the surface of the substrate to be processed can be controlled within 700mm or even smaller. In comparison, for commercially available products in the same field, such as the CoaxPrinter processing head (patent number DE102007018400B4) publicly sold by Precitec GmbH in Germany, the outer envelope size disclosed in its product specification is 483mm*518mm*152mm without including the molten pool image and temperature detection optical path unit. The existing patent mentioned in the background art was previously developed by the applicant, and the outer envelope size of its processing head is not less than 420mm*520mm*150mm.

[0043] Example 2 This embodiment provides a dual-beam composite ring laser directional energy deposition processing method, including: The first incident laser 1 is guided into the first convex conical lens 2, forming a first conical beam. The second incident laser 10 is guided into the second convex conical lens 11, forming a second conical beam. The first conical beam is transmitted through the dichroic mirror 4, and the second conical beam is reflected by the dichroic mirror 4 and then redirected. The first conical beam transmitted through the dichroic mirror 4 and the second conical beam reflected by the dichroic mirror 4 are coaxially passed through the plano-convex axial conical mirror 12, forming a first hollow ring laser beam and a second hollow ring laser beam, respectively.

[0044] The first and second hollow annular laser beams are reflected by the tilted fifth reflecting plane mirror 13 and then directed to the two prismatic reflecting surfaces of the reflecting prism 5. The two prismatic reflecting surfaces of the reflecting prism 5 divide the beams into a front half-annular beam and a rear half-annular beam, respectively.

[0045] The first hollow ring laser beam's front and rear half-ring beams are each reflected by two reflecting plane mirrors and return to reflecting prism 5. They are combined in the beam-combining region of the two prismatic reflecting surfaces of reflecting prism 5 to form the first hollow ring beam. This beam-combining region is offset from the beam-splitting region by a certain distance. Similarly, the second hollow ring laser beam's front and rear half-ring beams are each reflected by two reflecting plane mirrors and return to reflecting prism 5. They are combined in the beam-combining region of the two prismatic reflecting surfaces of reflecting prism 5 to form the second hollow ring beam. The through-hole of the reflecting prism is located at the center of the beam-combining region.

[0046] The first and second hollow annular laser beams coaxially pass through the focusing lens 14 and the plane window mirror 15, converging near the surface 17 of the substrate to be processed to form the first and second annular focused laser spots, respectively. Metal wire or a gas-metal powder mixture is then fed onto the surface 17 of the substrate to be processed, causing the metal wire or gas-metal powder mixture to coaxially couple with the first and / or second annular focused laser spots onto the surface 17 of the substrate to be processed.

[0047] This method offers flexible options for processing different materials or scenarios. The first incident laser 1 or the second incident laser 10 can be activated individually, or both lasers can be activated simultaneously, allowing for flexible selection based on actual processing needs. When processing high-reflectivity materials such as copper and aluminum alloys, both blue and infrared lasers can be activated simultaneously. The high absorption rate of the blue laser enhances the material's absorption of laser energy, while the high energy density of the infrared laser ensures processing efficiency. Furthermore, by utilizing the characteristic that the focal points formed by the first and second incident lasers can have a certain longitudinal deviation, this method can be applied to high-speed laser-directed energy deposition (LDED) processing scenarios. Specifically, the laser with its focal point slightly further away from the substrate preferentially heats the metal powder or wire, while the other laser primarily heats the substrate to stabilize the molten pool. This significantly increases the scanning speed of the processing head, enabling high-speed processing.

[0048] While the specific embodiments of the present invention have been described above, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention. For example, based on the present invention, those skilled in the art can coaxially add a molten pool monitoring optical path unit without creative effort, which is still within the scope of protection of the present invention.

Claims

1. A dual-beam composite ring laser directional energy deposition processing head, characterized in that: The optical path of the first incident laser is sequentially provided with a first convex conical lens, a dichroic mirror, a plano-convex axial conical mirror, a fifth reflecting plane mirror, an integrated reflecting mirror unit, a focusing lens, and a plane window mirror; The second incident laser is incident on the dichroic mirror through the second convex conical lens and shares the same mirror group as the first incident laser optical path, including a plano-convex axial conical mirror, a fifth reflecting plane mirror, an integrated reflecting mirror group unit, a focusing lens, and a plane window mirror, and the optical axes of the two optical paths overlap on the shared mirror group; The dichroic mirrors are arranged at an angle to transmit the first incident laser and reflect the second incident laser. The fifth reflecting plane mirror is arranged at an angle, with its reflecting surface facing the plano-convex axial cone mirror and the integrated reflecting mirror unit. The integrated reflector unit includes a reflector prism and four reflector plane mirrors symmetrically arranged around the reflector prism. The reflector surface of the reflector prism faces the reflector plane mirror and the surface of the substrate to be processed. The reflecting prism, focusing lens, and plane window mirror have through holes in their middle positions for the feeding pipeline assembly to pass through.

2. The dual-beam composite ring laser directional energy deposition head as described in claim 1, characterized in that, A first incident laser reflector is also provided in the optical path of the first incident laser, and the first incident laser reflector is located between the optical paths of the first convex conical lens and the dichroic mirror.

3. The dual-beam composite ring laser directional energy deposition head as described in claim 1, characterized in that, The first convex conical lens and the plano-convex axial conical lens constitute the first hollow annular laser beam mirror unit; the convex conical lens has a spherical or aspherical convex surface facing the incident laser, and the other surface is an outwardly convex conical surface with a cone angle of 110° to 160°; the outwardly convex conical surface of the plano-convex axial conical lens has a cone angle of 110° to 160°, and the conical surface is arranged coaxially with the conical surface of the convex conical lens, and the other optical surface of the plano-convex axial conical lens is a plane.

4. The dual-beam composite ring laser directional energy deposition head as described in claim 1, characterized in that, The second convex conical lens and the plano-convex axial conical lens constitute the second hollow annular laser beam lens unit. The second convex conical lens has a spherical or aspherical convex surface facing the incident laser, and the other side is an outwardly convex conical surface with a cone angle of 110° to 160°. This conical surface is arranged coaxially with the conical surface of the second convex conical lens.

5. The dual-beam composite ring laser directional energy deposition head as described in claim 1, characterized in that, The normal vectors of the four reflecting plane mirrors in the integrated reflector unit are coplanar, and the normals of any two adjacent reflecting plane mirrors are perpendicular to each other. The normal line of any reflecting plane mirror forms a 45° angle with the edge line of the reflecting prism, and the edge angle of the reflecting prism is a 90° right angle.

6. The dual-beam composite ring laser directional energy deposition head as described in claim 1, characterized in that, The focusing lens consists of one aspherical lens or two separate spherical lenses; When an aspherical lens is used, one of the lens's transmission surfaces is an even-order aspherical surface, and the other surface is one of a sphere, a plane, or an even-order aspherical surface. When two separate spherical lenses are used, they consist of a biconvex lens and a meniscus lens. The convex surface of the meniscus lens faces the surface of the substrate to be processed, and the concave surface of the meniscus lens is adjacent to one of the convex surfaces of the biconvex lens.

7. The dual-beam composite ring laser directional energy deposition head as described in claim 1, characterized in that, The plane window mirror is composed of one or two plane glass mirrors.

8. The dual-beam composite ring laser directional energy deposition head as described in claim 1, characterized in that, The first incident laser is an infrared laser in the 900 to 1100 nm band or a blue laser in the 400 to 500 nm band. Correspondingly, the second incident laser is a blue laser in the 400 to 500 nm band or an infrared laser in the 900 to 1100 nm band, and the wavelength ranges of the two do not overlap.

9. The dual-beam composite ring laser directional energy deposition head as described in claim 1, characterized in that, The feeding pipeline assembly has a central hole for passing a gas-metal powder mixture to form a powder jet, or for passing a metal wire.

10. A method for directional energy deposition processing using a dual-beam composite ring laser, characterized in that, Includes the following steps: The first incident laser beam is guided into the first convex conical lens and forms a first conical beam; the second incident laser beam is guided into the second convex conical lens and forms a second conical beam. The first conical beam is transmitted through a dichroic mirror, and the second conical beam is reflected by the dichroic mirror and then redirected. The first conical beam transmitted through the dichroic mirror and the second conical beam reflected by the dichroic mirror pass coaxially through a plano-convex axial conical mirror to form the first hollow ring laser beam and the second hollow ring laser beam, respectively. The first and second hollow ring laser beams are reflected by the tilted fifth reflecting plane mirror and then turned, and are incident on the two prismatic reflecting surfaces of the reflecting prism. They are then divided into a front half-ring beam and a rear half-ring beam by the two prismatic reflecting surfaces of the reflecting prism. The first hollow ring laser beam's front and rear half-ring beams are each reflected by two reflecting plane mirrors and return to a reflecting prism. They are combined in the beam-combining area of ​​the two prismatic reflecting surfaces of the reflecting prism to form the first hollow ring beam. The beam-combining area is offset from the beam-splitting area by a certain distance. The second hollow ring laser beam's front and rear half-ring beams are each reflected by two reflecting plane mirrors and return to a reflecting prism. They are combined in the beam-combining area of ​​the two prismatic reflecting surfaces of the reflecting prism to form the second hollow ring beam. The through-hole of the reflecting prism is located in the center of the beam-combining area. The first hollow annular beam and the second hollow annular beam pass coaxially through a focusing lens and a plane window mirror, and converge near the surface of the substrate to be processed to form the first annular focused laser spot and the second annular focused laser spot, respectively. Metal wire or gas-metal powder mixture is fed to the surface of the substrate to be processed, so that the metal wire or gas-metal powder mixture is coaxially coupled with the first annular focused laser spot and / or the second annular focused laser spot to act on the surface of the substrate to be processed.

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