A laser forging printing optical path system based on hollow optical fiber coupling ultrafast laser and a printing method thereof

Abstract

This invention provides a laser forging printing optical path system and printing method based on hollow fiber coupled ultrafast laser. The system includes: a continuous laser module that outputs continuous laser through a solid fiber; an ultrafast laser module that outputs ultrafast pulsed laser and enters a hollow fiber coupled transmission unit via spatial optical coupling; a hollow fiber coupled transmission unit that uses a hollow fiber to transmit the ultrafast pulsed laser in a sealed manner; a dual laser beam combining unit that combines the continuous laser and the ultrafast pulsed laser into a coaxial composite laser beam; a scanning and focusing unit that focuses the composite laser beam onto the printing powder bed; and a timing coordination control system for controlling the laser output and synchronizing the timing. This invention uses hollow fiber to transmit ultrafast laser, effectively isolating environmental vibration and airflow disturbance, avoiding pulse width broadening caused by nonlinear effects, ensuring the peak power density of impact forging, and realizing integrated high-performance additive manufacturing of laser powder bed melting and ultrafast laser in-situ impact forging.

Description

Technical Field

[0001] This invention belongs to the field of laser additive manufacturing technology, specifically a laser forging printing optical path system and printing method based on hollow fiber coupled ultrafast laser. Background Technology

[0002] Laser forging printing is an innovative high-performance metal additive manufacturing technology that innovatively integrates ultrafast laser shock forging strengthening with traditional laser powder bed fusion 3D printing in situ. The core principle of this technology is as follows: after the laser melts the metal powder layer by layer to complete the printing shape, a pulsed laser immediately generates an ultra-high pressure shock wave to simultaneously forge and strengthen the newly solidified cladding layer. This achieves integrated and simultaneous completion of additive forming and forging strengthening, eliminating the traditional secondary strengthening process after forming. It can obtain low-stress, high-density, and high-performance metal components without subsequent heat treatment or shaping. It retains the advantages of laser additive manufacturing—free forming, high precision, and complex structure forming—while also possessing the characteristics of traditional forging processes—density of grain and excellent mechanical properties—perfectly balancing the forming accuracy and overall service performance of the components.

[0003] The current mainstream approach is to transmit ultrafast lasers via spatial optical paths, using optical components such as mirrors and beam expanders to achieve dual laser coupling. However, this structure still has many technical shortcomings: First, it is highly sensitive to the environment. Ultrafast lasers are transmitted in open air and are easily affected by environmental vibrations, airflow disturbances caused by temperature gradients, and uneven air refractive index, which can cause the laser spot to drift and energy to fluctuate. This can lead to inaccurate forging points and inconsistent strengthening effects during long-term continuous printing.

[0004] Second, optical path calibration is complex. The spatial optical path contains a large number of adjustable optical components. To ensure the coaxiality of the two lasers, experienced technicians need to perform repeated precision adjustments, resulting in a long assembly and adjustment cycle. Furthermore, the equipment is prone to optical path misalignment after transportation or long-term use, leading to high maintenance costs.

[0005] Third, nonlinear effects and pulse width broadening. Ultrafast lasers have extremely high peak power, which can easily induce nonlinear optical phenomena such as the Kerr effect and self-focusing when propagating in air. This leads to pulse time-domain waveform distortion and pulse width broadening, reducing the peak power density of impact forging and weakening the strengthening effect.

[0006] Fourth, the equipment has low integration. Spatial optical paths require a large amount of space for the layout of optical components, which is not conducive to the miniaturization and compact design of the equipment, and also limits the flexibility of the optical path layout.

[0007] Therefore, there is an urgent need to develop a new type of ultrafast laser transmission and beam combining system that is highly stable, has low environmental sensitivity, and is easy to integrate and maintain, in order to promote the industrial mass production of laser forging printing technology. Summary of the Invention

[0008] To address the problems of poor spatial light transmission stability, susceptibility to environmental interference, and complex assembly and adjustment in existing laser forging printing equipment, this invention provides a laser forging printing optical path system and printing method based on hollow fiber coupled ultrafast laser, in order to improve optical path stability, simplify structure, and enhance forming consistency.

[0009] To solve the above-mentioned technical problems, embodiments of the present invention provide the following technical solution: a laser forging printing optical path system based on hollow fiber coupled with ultrafast laser, characterized in that it includes: A continuous laser module is used to output continuous laser light, and the continuous laser module is connected to a dual laser beam combining unit via a solid optical fiber. The ultrafast laser module is used to output ultrafast pulsed laser light, which enters the hollow fiber optic coupling transmission unit via spatial optical coupling. A hollow fiber coupling transmission unit, whose input end is connected to the output end of the ultrafast laser module through a spatial optical coupling optical component, is used to couple the ultrafast pulsed laser into the hollow fiber. A dual laser beam combining unit, with its first input end connected to the output end of the solid optical fiber and its second input end connected to the output end of the hollow optical fiber coupling transmission unit, is used to combine the continuous laser and the ultrafast pulse laser into a coaxial composite laser beam. A scanning and focusing unit is disposed on the output optical path of the dual laser beam combining unit, and is used to focus and scan the coaxial composite laser beam onto the processing area of ​​the printing powder bed; The timing-synchronized control system is electrically connected to the continuous laser module, the ultrafast laser module, and the scanning focusing unit, respectively, and is used to control the laser output to be synchronized with the timing sequence.

[0010] Furthermore, the hollow optical fiber in the hollow optical fiber coupling transmission unit is an anti-resonant hollow optical fiber or a Kagome-type hollow optical fiber; the hollow optical fiber is covered with a sealed gas-filled vibration-damping armor structure, and the sealed gas-filled vibration-damping armor structure is filled with inert gas or is in a vacuum state.

[0011] Furthermore, the spatial optical coupling optical component includes a collimating lens group and a focusing lens group arranged sequentially along the optical path.

[0012] Furthermore, the dual laser beam combining unit is a dichroic mirror or a polarization beam combiner.

[0013] Furthermore, the scanning focusing unit includes a high-speed scanning galvanometer and an F-theta field mirror; after passing through the high-speed scanning galvanometer and the F-theta field mirror, the coaxial composite laser beam forms a focused spot on the surface of the printing toner bed.

[0014] Furthermore, the timing-coordinated control system includes: A laser driver module is used to control the continuous laser module to output continuous laser and the ultrafast laser module to output ultrafast pulsed laser, respectively. The synchronous triggering module is used to trigger the ultrafast laser module to emit pulsed laser to perform in-situ impact forging of the solidified layer during the solidification window period after the continuous laser melting of powder forms a molten pool, according to the preset processing trajectory and timing logic. The scanning trajectory control module is used to control the scanning focusing unit so that the coaxial composite laser beam scans along a preset path.

[0015] The present invention also provides a method for stabilizing the optical path of laser forging printing based on the above system, comprising the following steps: Step S1: The continuous laser module outputs continuous laser light, which is transmitted to the dual laser beam combining unit via solid optical fiber; Step S2: The ultrafast laser module outputs an ultrafast pulsed laser, which is then spatially coupled into the hollow fiber coupling transmission unit and transmitted in a sealed manner within the core of the hollow fiber. Step S3: The ultrafast pulsed laser emitted from the hollow fiber coupled transmission unit is collimated and enters the dual laser beam combining unit, where it is coaxially combined with the continuous laser to form a coaxial composite laser beam. Step S4: The coaxial composite laser beam enters the scanning and focusing unit and is synchronously focused onto the processing area of ​​the printing powder bed; Step S5: Under the control of the timing and coordination control system, the continuous laser melts the powder to form a cladding layer, and the ultrafast pulsed laser performs in-situ impact forging on the cladding layer at the moment of solidification.

[0016] Furthermore, in step S2, the ultrafast pulsed laser enters the hollow fiber coupling transmission unit via spatial optical coupling, specifically by collimating the emitted light through a lens group and then focusing it into the hollow fiber.

[0017] Furthermore, in step S2, the transmission path of the light beam inside the hollow optical fiber is in a vacuum or inert gas protected environment.

[0018] Furthermore, in step S4, the coaxial composite laser beam is focused by a focusing lens group.

[0019] The beneficial effects of the above-described technical solution of the present invention are as follows: (1) The ultrafast laser is confined to the core of the hollow optical fiber for transmission. The armor structure outside the optical fiber provides mechanical vibration reduction and environmental isolation, which fundamentally eliminates the influence of vibration, airflow and temperature drift on optical path directivity and energy stability.

[0020] (2) When ultrafast lasers are transmitted in air fiber cores, the beam is strictly confined and the transmission medium is uniform, which avoids the pulse width distortion and broadening caused by the air nonlinearity of ultrafast high peak lasers in air transmission, ensuring the fidelity transmission of pulse time domain waveform and width, and ensuring the consistency of peak power density and strengthening effect of impact forging.

[0021] (3) The complex spatial reflection and beam expansion optical path is replaced by a flexible hollow optical fiber, which greatly reduces the number of discrete optical components and reduces the difficulty of equipment debugging. Only the input / output ends of the hollow optical fiber need to be aligned once before the dual laser beam is combined. No repeated calibration is required in subsequent use, which significantly improves the industrial reliability and maintainability of the equipment.

[0022] (4) Hollow optical fiber can be bent and wired, which allows the ultrafast laser source to be arranged separately from the processing head, greatly freeing up the internal space of the equipment and making it easier to realize the miniaturization, compactness and flexible collaboration of multiple processing heads in laser forging printing equipment. Attached Figure Description

[0023] Figure 1 This is for the ultrafast laser spatial light transmission optical path in existing laser forging printing equipment.

[0024] Figure 2 This is a schematic diagram of the laser forging printing optical path system of the present invention.

[0025] Figure 3 This is a schematic diagram of the overall structure of the system of the present invention.

[0026] The diagram is labeled as follows: 1-Continuous laser module; 2-Ultrafast laser module; 3-Hollow fiber coupled transmission unit; 4-Dual laser coaxial beam combining unit; 5-Scanning focusing unit; 6-Timing collaborative control system; 7-Printing powder bed. Detailed Implementation

[0027] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0028] Please see Figure 1 This is the ultrafast laser spatial light transmission optical path in existing laser forging printing equipment. The current mainstream solution is to transmit ultrafast laser based on the spatial light path and use optical components such as reflectors and beam expanders to achieve dual laser coupling. However, there are problems such as poor stability of ultrafast laser spatial light transmission, susceptibility to environmental interference, and complex assembly and adjustment.

[0029] This invention abandons the free-space coupled light transmission architecture of discrete reflectors and beam expanders, and uses hollow optical fiber as a flexible transmission carrier for ultrafast lasers. It is combined with an input-output collimation system and a sealed gas-filled vibration-damping armor integrated structure to overcome the drawbacks of traditional free-space optical paths from the two-layer architecture of light transmission medium and optical path configuration.

[0030] Combination Figure 2 , Figure 3 As shown, this embodiment provides a laser forging printing optical path system based on hollow fiber coupled ultrafast laser. The system mainly includes: a continuous laser module 1, an ultrafast laser module 2, a hollow fiber coupled transmission unit 3, a dual laser beam combining unit 4, a scanning and focusing unit 5, a timing-coordinated control system 6, and a printing powder bed 7.

[0031] 1. The specific structure and connection relationships of each module Continuous Laser Module 1: Employs a high-power continuous laser with fiber-coupled output, connected to a large-mode-area solid-core silica fiber. The other end of this solid-core fiber serves as the output, connected to the first input end (e.g., the transmission end of a dichroic mirror) of the dual laser beam combining unit 4. This module is responsible for providing the forming heat source required for laser powder bed melting.

[0032] Ultrafast laser module 2: outputs femtosecond / picosecond pulsed laser (forging laser), which enters the hollow fiber coupling transmission unit 3 via spatial optical coupling.

[0033] Hollow fiber coupling transmission unit 3: Composed of hollow fiber (anti-resonant hollow fiber / Kagome hollow fiber), vacuum packaging structure, and high-precision coupling head, it realizes low-loss and high-stability transmission of ultrafast laser.

[0034] Hollow optical fibers are characterized by low nonlinearity, low dispersion, and high damage threshold when transmitting ultrafast lasers.

[0035] A spatial optical coupling optical component is installed at the front end of the hollow optical fiber, consisting of a collimating lens and a focusing lens arranged sequentially along the optical path. The pulsed laser emitted from the ultrafast laser module 2 is first expanded and collimated into parallel light by the collimating lens, and then precisely focused onto the center of the input end face of the hollow optical fiber by the focusing lens.

[0036] The hollow optical fiber is encased in a metal braided mesh or corrugated tube armor sheath, forming a sealed cavity between the sheath and the fiber. This cavity is either evacuated or filled with high-purity argon gas via a valve. This structure provides mechanical buffering, suppressing the transmission of equipment vibrations to the fiber; furthermore, the vacuum or inert gas environment completely eliminates convective disturbances caused by temperature changes within the fiber and prevents dust that might be ignited by high-power lasers.

[0037] Dual laser beam combining unit 4: dual laser coaxial beam combining is achieved by using a dichroic mirror or polarization beam combiner.

[0038] The dichroic mirror has high transmittance for continuous lasers and high reflectance for ultrafast lasers. The continuous laser output from the solid fiber is transmitted through the dichroic mirror; the ultrafast laser output from the hollow fiber coupling transmission unit 3 is adjusted into parallel light by the rear collimating unit (composed of a collimating lens group) and then shines on the dichroic mirror at an incident angle of 45°. After being reflected, it precisely coincides with the transmitted continuous laser, forming a coaxial composite laser beam.

[0039] The polarization combiner consists of a polarization beam splitter and a half-wave plate. A continuous laser beam, after its polarization state is adjusted by the half-wave plate, is incident on the polarization beam splitter, while an ultrafast laser beam is directly incident on the other incident surface of the polarization beam splitter. The two laser beams are combined at the combining surface inside the polarization beam splitter, resulting in a coaxial composite laser beam. By adjusting the angle of the half-wave plate, the beam combining efficiency can be optimized, minimizing the energy loss of the combined dual laser beams.

[0040] The scanning and focusing unit 5 consists of a high-speed scanning galvanometer and an F-theta field lens. A coaxial composite laser beam is incident on the scanning galvanometer and, under the control of the timing-coordinated control system 6, deflects along a preset two-dimensional scanning path. Then, it is vertically focused onto the surface of the printing toner bed 7 by the F-theta field lens. The F-theta field lens ensures the uniformity of the focused spot across the entire scanning area.

[0041] Timing Coordination Control System 6: Integrates laser driver module, synchronization trigger module and scanning trajectory control module.

[0042] Laser driver module: Connected to the control interfaces of continuous laser module 1 and ultrafast laser module 2 respectively, used to set parameters such as output power and pulse frequency (for ultrafast lasers).

[0043] Scan trajectory control module: connected to the galvanometer drive board of the scanning focusing unit 5, converting the preset code or processing trajectory program into a voltage signal of the galvanometer to control the movement of the light spot.

[0044] Synchronous triggering module: Based on predefined timing logic (e.g., in each layer of printing, the continuous laser is turned on and moves first, forming a complete melt channel; at the end of the melt channel or after a specific delay of solidification of the molten pool, the ultrafast laser module 2 is triggered to emit one or a series of pulses to bombard the newly solidified cladding layer area). Specifically, the synchronous triggering module receives position feedback signals from the scanning galvanometer or calculates the optimal forging triggering timing based on the set scanning speed and path point, and outputs a trigger signal to the ultrafast laser module 2. A typical timing arrangement is: the continuous laser continuously emits light to form a steady-state molten pool; when the scanning galvanometer moves to a certain forging point, the synchronous triggering module triggers the ultrafast laser to emit light before the continuous laser is turned off.

[0045] Printing powder bed 7: A standard laser powder bed melting stage, including a liftable forming substrate, powder supply cylinder, and a scraper powder spreading mechanism.

[0046] 2. System workflow This invention is an integrated processing system for coaxial dual-beam combining of hollow fiber coupled ultrafast laser and solid fiber continuous laser. Through the working logic of independent and stable transmission of the two laser branches, precise beam focusing, and zoned synergistic action, it achieves simultaneous completion of laser cladding forming and in-situ forging strengthening. The detailed working process and corresponding technical effects are as follows: Step 1: Continuous laser light is stably transmitted to the beam combiner via solid-core optical fiber. The high-power continuous laser module 1 outputs a shaped continuous laser beam, relying on mature solid-core quartz optical fiber as the transmission medium to complete long-distance, high-power stable transmission.

[0047] Step 2: Ultrafast laser light is precisely spatially coupled into a hollow optical fiber for stable closed-loop transmission. After the ultrafast laser module 2 emits an ultrafast laser (picosecond / femtosecond), it first enters the hollow fiber coupling and transmission unit 3. The light emitted from the photonic crystal fiber is first collimated and then focused precisely into the hollow fiber through a lens group. The beam is confined in the air core of the fiber for sealed transmission. The entire process is isolated from external air turbulence, airflow disturbances, mechanical vibration, and coupling mismatch and beam drift caused by ambient temperature drift, thus completely avoiding the air nonlinear effects of open space optical paths.

[0048] Technical effects: It solves the core problems of traditional ultrafast lasers, such as high sensitivity to spatial optical path environment, severe spot drift, pulse distortion and pulse width broadening, and achieves full fidelity of beam quality, pulse waveform and energy density during ultrafast laser transmission, providing a stable and high-quality laser source for subsequent precision forging and strengthening.

[0049] Step 3: Collimation and adjustment of the ultrafast laser output from the hollow fiber, and high-precision coaxial beam combining with the continuous laser. The ultrafast laser, after being stably transmitted through the hollow fiber of the hollow fiber coupling transmission unit 3, is output from the output end and enters the back-end collimation unit. Then it is vertically incident on the dual-laser coaxial beam combining unit 4, and completes high-precision coaxial superposition with the continuous laser transmitted to the position by the previous continuous laser module 1, so as to achieve complete overlap of the optical paths of the two beams and zero center offset, thus constructing a coaxial composite laser beam.

[0050] Technical benefits: This technology solves the problems of poor coaxiality, beam offset, and uneven energy distribution in traditional dual-laser beam combining. The coaxial accuracy of the two beams is significantly improved, completely avoiding misalignment of the forming and strengthening areas caused by beam offset, and ensuring that subsequent cladding and forging processes work synchronously on the same processing area. At the same time, it eliminates the need for repeated manual adjustment of the optical path coaxiality, greatly reducing the difficulty of equipment debugging and maintenance costs.

[0051] Step 4: Simultaneously focus coaxial dual laser beams onto the powder bed processing area The composite laser beam, coaxially combined by the dual-laser coaxial beam combining unit 4, is then focused with high precision by the integrated precision focusing lens group built into the processing head. The combined dual laser energy is highly concentrated and precisely vertically focused onto the preset processing trajectory area on the powder bed surface by the scanning focusing unit 5. The focused spot size is stable without drift, and the energy spatial distribution is uniform, which can accurately cover the single-pass cladding processing path.

[0052] Technical effect: It achieves precise focusing of dual beams in sync, in the same position, and at the same focal point, completely avoiding problems such as misalignment, focus drift, and deterioration of beam shape in traditional spatial optical paths.

[0053] Step 5: Dual-beam synergy enables integrated processing of cladding forming and in-situ ultrafast forging strengthening. After the dual laser beams are focused onto the printing powder bed 7, the two lasers play a differentiated and synergistic processing role: the continuous laser acts as the main heat source to melt the metal powder and the substrate, realizing the laser cladding layer-by-layer forming; at the moment the molten pool solidifies, the ultrafast laser simultaneously impacts and forges the cladding layer in situ, and the dual lasers work together to complete the integrated processing of forming and strengthening.

[0054] Technical effects: Through the synergistic effect of continuous laser forming and ultrafast laser in-situ forging, the density and surface hardness of the cladding layer are greatly improved, residual tensile stress is effectively eliminated, crack initiation is suppressed, and the wear resistance, corrosion resistance and fatigue resistance of parts are significantly improved. At the same time, forming accuracy and appearance quality are guaranteed, realizing high-precision and high-performance integrated laser additive manufacturing.

[0055] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A laser forging printing optical path system based on hollow fiber coupled ultrafast laser, characterized in that, include: A continuous laser module (1) is used to output continuous laser light. The continuous laser module (1) is connected to the dual laser beam combining unit (4) through a solid optical fiber. The ultrafast laser module (2) is used to output ultrafast pulsed laser, which enters the hollow fiber coupling transmission unit (3) via spatial optical coupling. The hollow fiber coupling transmission unit (3) has its input end connected to the output end of the ultrafast laser module (2) through a spatial optical coupling optical component, and is used to couple the ultrafast pulse laser into the hollow fiber. The dual laser beam combining unit (4) has its first input end connected to the output end of the solid fiber and its second input end connected to the output end of the hollow fiber coupling transmission unit (3), and is used to combine the continuous laser and the ultrafast pulse laser into a coaxial composite laser beam. The scanning and focusing unit (5) is set on the output optical path of the dual laser beam combining unit (4) and is used to focus and scan the coaxial composite laser beam to the processing area of ​​the printing powder bed (7). The timing coordination control system (6) is electrically connected to the continuous laser module (1), the ultrafast laser module (2) and the scanning focusing unit (5) respectively, and is used to control the laser output to be synchronized with the timing.

2. The laser forging printing optical path system based on hollow fiber coupled ultrafast laser according to claim 1, characterized in that, The hollow optical fiber in the hollow optical fiber coupling transmission unit (3) is an anti-resonant hollow optical fiber or a Kagome-type hollow optical fiber; the hollow optical fiber is covered with a sealed gas-filled vibration damping armor structure, and the sealed gas-filled vibration damping armor structure is filled with inert gas or is in a vacuum state.

3. The laser forging printing optical path system based on hollow fiber coupled ultrafast laser according to claim 1, characterized in that, The spatial optical coupling optical component includes a collimating lens group and a focusing lens group arranged sequentially along the optical path.

4. The laser forging printing optical path system based on hollow fiber coupled ultrafast laser according to claim 1, characterized in that, The dual laser beam combiner (4) is a dichroic mirror or a polarizing beam combiner.

5. The laser forging printing optical path system based on hollow fiber coupled ultrafast laser according to claim 1, characterized in that, The scanning focusing unit (5) includes a high-speed scanning galvanometer and an F-theta field mirror; after the coaxial composite laser beam passes through the high-speed scanning galvanometer and the F-theta field mirror, it forms a focused spot with uniform energy distribution on the surface of the printing powder bed (7).

6. The laser forging printing optical path system based on hollow fiber coupled ultrafast laser according to claim 1, characterized in that, The timing-coordinated control system (6) includes: A laser driving module is used to control the continuous laser module (1) to output continuous laser and to control the ultrafast laser module (2) to output ultrafast pulsed laser. The synchronous triggering module is used to trigger the ultrafast laser module (2) to emit pulsed laser to perform in-situ impact forging of the solidified layer during the solidification window period after the continuous laser melting of powder forms a molten pool, according to the preset processing trajectory and timing logic. The scanning trajectory control module is used to control the scanning focusing unit (5) so that the coaxial composite laser beam scans along a preset path.

7. A printing method based on the laser forging printing optical path system of hollow fiber coupled ultrafast laser as described in any one of claims 1 to 6, characterized in that, Includes the following steps: Step S1: The continuous laser module (1) outputs continuous laser light, which is transmitted to the dual laser beam combining unit (4) via solid fiber. Step S2: The ultrafast pulsed laser is output from the ultrafast laser module (2), and the ultrafast pulsed laser is coupled into the hollow optical fiber of the hollow optical fiber coupling transmission unit (3) via spatial optical coupling, and is transmitted in a sealed manner within the core of the hollow optical fiber. Step S3: The ultrafast pulsed laser emitted from the hollow fiber coupled transmission unit (3) is collimated and enters the dual laser beam combining unit (4), where it is coaxially combined with the continuous laser to form a coaxial composite laser beam; Step S4: The coaxial composite laser beam enters the scanning focusing unit (5) and is synchronously focused onto the processing area of ​​the printing powder bed (7); In the above steps, under the control of the timing and coordination control system (6), the continuous laser melts the powder to form a cladding layer, and the ultrafast pulsed laser performs in-situ impact forging of the cladding layer at the moment of solidification.

8. The printing method of the laser forging printing optical path system according to claim 7, characterized in that, In step S2, the ultrafast pulsed laser enters the hollow optical fiber of the hollow optical fiber coupling transmission unit (3) through spatial optical coupling. Specifically, the ultrafast pulsed laser collimates the outgoing light through a lens group and then focuses it into the hollow optical fiber.

9. The printing method of the laser forging printing optical path system according to claim 8, characterized in that, In step S2, the transmission path of the light beam inside the hollow optical fiber is in a vacuum or inert gas protected environment.

10. The printing method of the laser forging printing optical path system according to claim 7, characterized in that, In step S4, the coaxial composite laser beam is focused by a focusing lens group.

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