A precision laser selective melting system based on high repetition rate pulse train femtosecond laser

Abstract

This invention discloses a precision laser selective melting system based on a high-repetition-rate femtosecond laser pulse train. The system includes a substrate forming unit, a displacement system, a powder spreading system, an environmental control system, a control system, a laser system, a scanning system, and a forming chamber. This invention employs passive mode-locking technology with an ultrashort fiber resonator to generate high-repetition-rate pulses. Through pulse broadening, modulation amplification, and recompression, a high-repetition-rate femtosecond laser output is achieved, which is then focused onto the powder surface by the scanning system. The control system is connected to the displacement system, powder spreading system, laser system, and scanning system to control the entire laser selective melting process. The laser selective melting system of this invention uses an ultrafast laser with a repetition rate exceeding 1 GHz and modulated pulses instead of the continuous-wave laser in existing equipment, balancing high heating rate and energy utilization efficiency, thereby improving efficiency while reducing energy consumption.

Description

Technical Field

[0001] This invention relates to the field of metal additive manufacturing technology, specifically to a precision laser selective melting system based on a high repetition frequency pulse train femtosecond laser. Background Technology

[0002] Selective laser melting (SLM) technology has attracted widespread attention due to its ability to achieve high-precision additive manufacturing of parts with complex geometries and excellent mechanical properties. Traditional SLM systems generally use continuous-wave lasers with a wavelength of 1064 nm for processing; however, this wavelength has low processing efficiency for materials with high reflectivity, high thermal conductivity, and high melting points. Mainstream low-repetition-rate femtosecond lasers possess extremely short pulse durations and extremely high peak power densities, which can induce nonlinear absorption in materials, causing rapid heating, but also easily leading to material ablation, making them unsuitable for SLM. Therefore, there is an urgent need for a laser that can adaptably process materials to solve the problem of low processing efficiency in selective melting. In recent years, high-repetition-rate femtosecond lasers have shown unique advantages in the field of high-efficiency laser subtractive manufacturing, but have not yet been introduced into the field of laser additive manufacturing. Summary of the Invention

[0003] The purpose of this invention is to provide a precision laser selective melting system based on a high-repetition-rate femtosecond laser pulse train, which achieves a balance between efficient heating and uniform forming, thus improving forming quality and efficiency and expanding the range of processable materials. This invention eliminates the need to change lasers of different wavelengths; by simply adjusting the power and modulation pulse, it enables adaptive processing of different materials, improving the energy efficiency of conventional laser selective melting. This invention is suitable for additive manufacturing of high-precision feature structures and thin-walled parts, effectively improving forming quality.

[0004] A precision laser selective melting system based on a high repetition rate pulse train femtosecond laser includes a forming substrate, a displacement system, a powder spreading system, an environmental control system, a laser system, a scanning system, a control system, and a forming chamber. The displacement system, powder spreading system, laser system, and scanning system are all located inside the forming chamber. The displacement system is used to drive the molding substrate to move; The powder spreading system is used to spread a uniform thin layer of powder on the surface of a molded substrate; The environmental control system is used to replace the air in the molding chamber with an inert atmosphere; The laser system is used to output high-repetition-rate pulsed laser light to the scanning system; The scanning system is used to focus a pulsed laser onto the powder on the surface of the molded substrate and control the focused laser spot to perform scanning. The control system connects the displacement system, powder spreading system, laser system, and scanning system to control the entire laser selective melting and forming process.

[0005] The laser system includes a high repetition rate mode-locked seed laser, a stretcher, a modulator, an amplifier, and a compressor connected in sequence. The high repetition rate mode-locked seed laser is used to output a high repetition rate femtosecond laser, the stretcher is used to stretch the pulse of the high repetition rate femtosecond laser, the modulator is used to modulate the pulsed laser, the amplifier is used to amplify the power of the pulsed laser, and the compressor is used to recompress the pulse width of the pulsed laser, thereby outputting a high repetition rate pulse train femtosecond laser.

[0006] Furthermore, the displacement system includes a Z-axis displacement stage and a forming platform. The Z-axis displacement stage can drive the forming platform to move in the vertical direction, and the forming substrate is placed in the groove of the forming platform. After each layer of powder forming is completed, the Z-axis displacement stage drives the forming platform to descend by one layer thickness before the next layer of powder spreading and powder forming is performed.

[0007] Furthermore, the stepping resolution of the Z-axis displacement stage in the forming platform moving system is ≤1μm.

[0008] Furthermore, the powder spreading system includes a powder spreading table, a scraper assembly, and an X-axis displacement stage. The area between the two scrapers is a powder receiving area for storing the powder to be spread. The main scraper is used to evenly spread the powder onto the molding substrate, while the secondary scraper is used to prevent powder overflow. For the next powder spreading operation, the roles of the main and secondary scrapers are reversed, and the X-axis displacement stage drives the scraper assembly to perform linear reciprocating motion on the surface of the molding substrate.

[0009] Furthermore, the scraper assembly includes two scrapers with a fixed spacing, the two scrapers being perpendicular to the X-axis direction.

[0010] Furthermore, the environmental control system includes a vacuum pump and a gas cylinder, a barometer and an oxygen sensor. The vacuum pump is used to extract gas from the molding chamber, the gas cylinder is used to fill the molding chamber with a specific gas, and the barometer and oxygen sensor are used to monitor the gas pressure and oxygen concentration in the molding chamber, respectively. Furthermore, the scanning system includes a reflector, an electric optical shutter, a galvanometer, and a field mirror, used to focus the pulsed laser onto the powder on the surface of the molded substrate and drive the focused laser spot to scan: The pulsed laser output from the laser system first passes through the reflector of the scanning system and then sequentially enters the motorized optical shutter and galvanometer. The galvanometer then controls the laser deflection, and finally the field lens focuses the laser onto the surface of the powder material.

[0011] Furthermore, the electric optical shutter is used to open and close the laser beam at high speed during laser processing, with a closing response time (90% - 10% exposure) ≤ 10ms; The galvanometer controls laser deflection by rotation, with a maximum angular velocity ≥500 rad / s; The field lens is an f-θ lens, used to correct distortion, field curvature, etc., and is responsible for linearly converting the deflection of the laser by the galvanometer into the displacement of the laser focus on the focal plane. The scanning area is ≥50mm×50mm.

[0012] Furthermore, the control system connects to the displacement system, powder spreading system, laser system, and scanning system, thereby controlling the entire laser selective melting process: The control system controls the high repetition rate mode-locked seed laser in the laser system, including starting, stopping, output power control, and pulse modulation, to ensure that the high repetition rate mode-locked seed laser can be adaptively adjusted according to the material during the laser selective melting and forming process. The control system controls the deflection of the galvanometer in the scanning system and controls the shutter to manage the on / off state of the optical path, ensuring that the pulsed laser focus scans according to the program during the forming process. The control system controls the Z-axis displacement stage of the displacement system and the X-axis displacement stage of the powder spreading system to ensure the uniformity and consistency of the powder layer thickness.

[0013] Furthermore, a laser system and a scanning system are installed on the top of the molding chamber, an air inlet and an air outlet are provided on the side wall of the molding chamber, and a molding platform displacement system and a powder spreading system are installed at the bottom of the molding chamber.

[0014] Furthermore, the high repetition rate mode-locked seed laser employs an ultrashort fiber resonator laser, utilizing a semiconductor saturable absorber mirror to achieve passive mode-locking, achieving a repetition rate ≥ 1 GHz, ensuring the laser pulse interval is less than the material's thermal diffusion time. The repetition rate is controlled by adjusting the resonator length L to maintain a repetition rate ≥ 1 GHz. Replacing the continuous-wave laser in existing equipment with an ultrafast laser boasting a repetition rate exceeding 1 GHz and modulated pulses balances high heating rate and energy utilization efficiency, improving work efficiency while reducing energy consumption. At repetition rates above GHz, the pulse interval is less than the material's thermal diffusion time.

[0015] The stretcher is used for pulse stretching of the laser; The modulator modulates the pulses by controlling the input signal of the control system, so that the laser is output in a pulse train mode; The pulse train consists of multiple adjacent pulses, and the frequency of the pulse train is 1 kHz. 100MHz, duty cycle of 0.01%-100%.

[0016] The amplifier is used to amplify the input pulse train laser step by step to >50W; The compressor is used to compress the pulse width of the laser to ≤500 fs; Further, before laser selective melting and forming, the environmental control system evacuates the forming chamber and fills it with inert gas. The control system slices the 3D model and generates scanning paths for each slice. The displacement system lowers the forming platform by a set layer thickness. The powder spreading system moves forward, pushing powder from the powder spreading stage to the forming platform, forming a powder layer of a set thickness on the surface of the forming substrate on the forming platform. After processing begins, the laser system outputs a high-repetition-rate femtosecond laser pulse train to the scanning system. The scanning system scans the powder with a focused laser spot according to a preset path, selectively melting the powder to form a continuous structure. The motorized shutter blocks the laser, the displacement system lowers the forming platform by a layer thickness, and the powder spreading system moves the scraper assembly in the opposite direction to complete a reverse powder spreading operation. The motorized shutter then allows the laser to pass through again and selectively melts the next layer of powder, bonding it with the previous layer. This cycle continues, layer by layer, until the entire printed part is formed.

[0017] Traditional laser selective melting systems generally employ continuous laser processing. Continuous laser energy input offers the advantages of sustained and stable thermal effects but a slow cooling rate. This leads to drawbacks such as a large heat-affected zone, severe molten pool fluctuations, increased spatter, and high residual stress. This invention utilizes a pulsed modulated femtosecond laser with a repetition rate in the GHz range. Compared to existing technologies, the advantages of this invention are: (1) Compared with continuous laser, high repetition rate femtosecond laser has a higher peak power at the same average power, and its extremely short pulse spacing can effectively reduce heat diffusion, resulting in higher heating efficiency, allowing materials to reach the melting point in a shorter time, greatly shortening the single-point laser action time, and thus achieving a higher scanning speed. (2) Compared with low repetition frequency lasers, high repetition frequency lasers have lower single-pulse energy at the same average power, which can avoid the adverse effects of single-pulse direct heating of materials above the boiling point, causing ablation and other energy waste and surface quality deterioration. The short pulse interval of high repetition frequency lasers makes the material heating process more continuous and uniform, which also helps to improve the surface quality and internal structure consistency of the molded parts; (3) After the laser is modulated to output in pulse train mode, the single pulse energy can be changed while maintaining the average power by adjusting the pulse train frequency and duty cycle. This allows the same system to adapt to a variety of materials with different reflectivities, thermal conductivity and melting points, thereby expanding the application range of laser selective melting technology. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the laser selective melting system based on a high repetition rate pulse train femtosecond fiber laser according to an embodiment of the present invention. Figure 2This is a schematic diagram of the laser system according to an embodiment of the present invention; Figure 3 Schematic diagram of the displacement system and powder spreading system according to an embodiment of the present invention; Figure 4 A schematic diagram of the displacement system according to an embodiment of the present invention; Figure 5 Schematic diagram of the molding platform and molding substrate in an embodiment of the present invention; Figure 6 A schematic diagram of the powder spreading system according to an embodiment of the present invention; Figure 7 A schematic diagram of the scraper assembly according to an embodiment of the present invention; Figure 8 A schematic diagram of the structure of a laser selective melting system based on a high repetition rate pulse train femtosecond fiber laser according to an embodiment of the present invention.

[0019] In the diagram: 101-Displacement system; 102-Powder spreading system; 103-Environmental control system; 104-Laser system; 105-Scanning system; 106-Control system; 201-High repetition rate mode-locked seed laser; 202-Stretcher; 203-Modulator; 204-Amplifier; 205-Compressor; 301-Z-axis displacement stage; 302-Forming platform; 303-Forming substrate; 304-Scraper assembly; 305-X-axis displacement stage; 306-Main scraper; 307-Secondary scraper; 308-Powder spreading stage; 801-Reflector; 802-Electric optical shutter; 803-Galvanometer; 804-Field lens. Detailed Implementation

[0020] To enable those skilled in the art to better understand the present invention, the invention will be further described below with reference to the accompanying drawings and specific embodiments. Obviously, the embodiments described below are merely some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] In one embodiment, a precision laser selective melting system based on a high-repetition-rate femtosecond laser pulse train is disclosed for CuCr alloys with high reflectivity and high thermal conductivity. Figure 1 As shown.

[0022] A precision laser selective melting system based on a high repetition rate pulsed femtosecond laser includes a forming substrate 303, a displacement system 101, a powder spreading system 102, an environmental control system 103, a laser system 104, a scanning system 105, a control system 106, and a forming chamber. The displacement system 101 is used to place the forming substrate 303 and move it; the powder spreading system 102 is used to obtain a uniform powder layer on the surface of the forming substrate 303; the environmental control system 103 can replace the air in the forming chamber with an inert atmosphere; the laser system 104 is used to output a high repetition rate pulsed laser to the scanning system 105; the scanning system 105 focuses the high repetition rate pulsed laser and controls the scanning of the focused laser spot; the control system 106 connects the displacement system 101, the powder spreading system 102, the laser system 104, and the scanning system 105, thereby controlling the entire laser selective melting forming process.

[0023] The laser system 104 and the scanning system 105 are located on the top of the inner wall of the molding chamber, the displacement system 101 and the powder spreading system 102 are installed inside the molding chamber, and the side wall of the molding chamber is provided with one air inlet and one air outlet.

[0024] Please see Figures 3-5 The displacement system 101 includes a Z-axis displacement stage 301 and a forming platform 302. The forming platform 302 is connected to the displacement output end of the Z-axis displacement stage 301, and the Z-axis displacement stage 301 can drive the forming platform 302 to move in the vertical direction. The forming substrate 303 is disposed in the groove of the forming platform 302. During operation, after each layer of powder forming is completed on the forming substrate 303, the Z-axis displacement stage 301 drives the forming platform 302 to descend by a preset layer thickness height, and then the next layer of powder spreading and powder forming is performed on the forming substrate 303.

[0025] In one embodiment, the step resolution of the Z-axis displacement stage 301 in the moving system 101 is ≤1μm.

[0026] Please see Figure 6The powder spreading system 102 includes a powder spreading table 308, an X-axis displacement table 305, and a scraper assembly 304. The scraper assembly 304 is located at the displacement output end of the X-axis displacement table 305. The X-axis displacement table 305 drives the scraper assembly 304 to perform linear reciprocating motion on the surface of the molding substrate 303, and to move linearly between the powder spreading table 308 and the molding substrate 303. The scraper assembly 304 includes two scrapers spaced apart, defined as a main scraper 306 and a secondary scraper 307. The two scrapers are perpendicular to the X-axis direction, and the area between the two scrapers is a powder receiving area for storing the powder to be spread. The main scraper 306 is used to evenly spread the powder on the molding substrate 303, and the vertical surface of the secondary scraper 307 forms a sealing barrier structure, which can effectively block the powder and prevent powder overflow. The functions of the main scraper 306 and the secondary scraper 307 are interchanged for the next powder spreading.

[0027] In one embodiment, a stepped structure is provided on the side of the main scraper 306 opposite to the secondary scraper 307. The side of the secondary scraper 307 opposite to the main scraper 306 is in contact with the lower surface of the stepped structure to form a continuous closed interface in both the vertical and horizontal directions. At this time, the vertical surface of the secondary scraper 307 forms a vertical "wall" that directly blocks the path of powder overflowing backward.

[0028] The environmental control system 103 includes a vacuum pump, a gas cylinder, a barometer, and an oxygen sensor. The vacuum pump is used to extract gas from the molding chamber, the gas cylinder is used to fill the molding chamber with a specific gas, and the barometer and oxygen sensor are used to monitor the gas pressure and oxygen concentration in the molding chamber, respectively.

[0029] Please see Figure 2 The laser system 105 includes a high repetition rate mode-locked seed laser 201, a pulse stretcher 202, a modulator 203, an amplifier 204, and a compressor 205 connected in sequence. The pulse stretcher 202 is used to broaden the pulse width of the pulsed laser in the time domain, reducing nonlinear effects during amplification. The modulator 203 modulates the pulses through input signals from the control system 106, so that the laser is output in pulse train mode. The high repetition rate femtosecond laser output by the high repetition rate mode-locked seed laser 201 is first broadened in the time domain by the pulse stretcher 202 to reduce nonlinear effects during amplification, then modulated and amplified by the modulator 203 and amplifier 204 respectively, and finally compressed by the compressor 205 to output a high repetition rate pulse train femtosecond laser.

[0030] In one embodiment, the high repetition rate mode-locked seed laser 201 employs an ultrashort fiber resonant cavity laser and utilizes a semiconductor saturable absorber mirror to achieve passive mode-locking, with a repetition rate ≥1GHz. The modulator 203 modulates the pulses by inputting signals through the control system 106, so that the laser is output in pulse train mode; The amplifier 204 is used to amplify the input pulse train laser step by step to >50W; The compressor 205 is used to compress the pulse width of the laser to ≤500 fs; In one embodiment, the pulse train comprises multiple adjacent pulses, and the frequency of the pulse train is 1 kHz. 100MHz, duty cycle of 0.01%-100%.

[0031] Please see Figure 8 The scanning system 105 is located inside the molding chamber. The scanning system 105 includes a reflector 801, an electric shutter 802, a galvanometer 803, and a field lens 804. It is used to focus a pulsed laser onto the powder on the surface of the molding substrate 303 and drive the focused laser spot to scan. The pulsed laser output by the laser system 104 first enters the electric shutter 802 and the galvanometer 803 in sequence through the reflector 801 of the scanning system. Then, the laser is deflected by the galvanometer 803 and finally focused onto the powder surface by the field lens 804.

[0032] In one embodiment, the motorized optical shutter 802 is used to rapidly open and close the laser beam during laser processing, with a closing response time (90%-10% exposure) ≤ 10ms. The galvanometer 803 controls laser deflection through rotation, with a maximum angular velocity ≥ 500rad / s. The field lens 804 is an f-θ lens used to correct distortion, field curvature, etc., and is responsible for linearly converting the laser deflection by the galvanometer 803 into the displacement of the laser focus on the focal plane. The scanning area is ≥ 50mm × 50mm, where f is the focal length and θ is the field of view, representing the maximum angular range that the optical system can observe. The f-θ lens ensures that the scanning speed of the laser beam on the focal plane is constant, i.e., the scanning distance is proportional to the scanning angle.

[0033] The control system 106 controls the entire laser selective melting process, including: The control system 106 controls the high repetition rate mode-locked seed laser 201 in the laser system 104, including start-up, stop, output power control, and pulse modulation, to ensure that the high repetition rate mode-locked seed laser 201 can be adaptively adjusted according to the material during the laser selective melting and forming process; the control system 106 controls the deflection of the galvanometer 803 in the scanning system 105 and controls the motorized optical shutter 802 to manage the on / off state of the optical path, ensuring that the pulsed laser focus is scanned according to the program during the forming process; the control system 106 controls the Z-axis displacement stage 301 of the displacement system 101 and the X-axis displacement stage 305 of the powder spreading system 102 respectively to ensure the uniformity and consistency of the powder spreading layer thickness.

[0034] In one embodiment, before laser selective melting and forming, the environmental control system 103 evacuates the forming chamber and then fills it with argon gas to reduce the oxygen content of the forming chamber to below 1000 ppm. The control system 106 slices the imported 3D model of the printed part and generates the scanning path for each slice. After the operation starts, the control system 106 controls the Z-axis displacement stage 301 in the displacement system 101 to move the forming substrate 303 in the forming platform 302 downward by 50µm, and then controls the X-axis displacement stage 305 in the powder spreading system 102 to move the scraper assembly 304 to push the powder in the powder receiving area from the powder spreading stage 308 to the forming platform 302, so that a single layer of CuCr alloy powder is spread evenly on the surface of the forming substrate 303 on the forming platform 302.

[0035] The control system 106 controls the mode-locked seed laser 201 of the laser system 104 to start, outputting a pulsed laser with a wavelength of 1064nm and a repetition frequency of 1.2GHz. After it enters a stable mode-locked state, the amplifier 203 is started in stages, setting the pulse train repetition frequency to 15MHz and the average output power to 100W. The pulse width is then compressed to 300fs by the compressor 204. The pulsed laser passes through the reflector 801 and is sequentially incident on the motorized optical shutter 802 and the galvanometer 803. The galvanometer 803 scans at a rate of 600mm / s, and then the laser is focused onto the CuCr alloy powder on the surface of the molded substrate 303 by the field lens 804 with a focal length of 100mm.

[0036] During the forming process, the control system 106, according to a preset program, controls the galvanometer 803 to scan the laser spot along a predetermined path on the CuCr alloy powder, causing selective melting of the powder to form a continuous structure. After each layer of powder is scanned, the control system 106 first controls the motorized shutter 802 to block the laser, and then uses the displacement system 101 to drive the forming platform 302 to descend again by 50µm. The powder spreading system 102 drives the scraper assembly 304 to move in the opposite direction to complete a new round of powder spreading. Subsequently, the control system 106 first controls the motorized shutter 802 to allow the laser to pass through, and then controls the galvanometer 803 to scan the next layer, causing the powder in this layer to melt together with the previous layer. This cycle continues until the entire CuCr alloy part is completely formed.

[0037] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily obtained by those skilled in the art within the scope of the present invention and by conceiving the solution according to the present invention should be included within the scope of protection of the present invention.

Claims

1. A precision laser selective melting system based on a high repetition rate pulse train femtosecond laser, characterized in that, It includes a molding substrate, a displacement system, a powder spreading system, an environmental control system, a laser system, a scanning system, a control system, and a molding chamber. The displacement system, powder spreading system, laser system, and scanning system are all located inside the molding chamber. The displacement system is used to drive the molding substrate to move; The powder spreading system is used to spread a uniform thin layer of powder on the surface of a molded substrate; The environmental control system is used to replace the air in the molding chamber with an inert atmosphere; The laser system is used to output high-repetition-rate pulsed laser light to the scanning system; The scanning system is used to focus a pulsed laser onto the powder on the surface of the molded substrate and control the focused laser spot to perform scanning. The control system connects the displacement system, powder spreading system, laser system, and scanning system to control the entire laser selective melting and forming process. The laser system includes a high repetition rate mode-locked seed laser, a stretcher, a modulator, an amplifier, and a compressor connected in sequence. The high repetition rate mode-locked seed laser is used to output a high repetition rate femtosecond laser, the stretcher is used to stretch the pulse of the high repetition rate femtosecond laser, the modulator is used to modulate the pulsed laser, the amplifier is used to amplify the power of the pulsed laser, and the compressor is used to recompress the pulse width of the pulsed laser, thereby outputting a high repetition rate pulse train femtosecond laser.

2. The precision laser selective melting system based on a high repetition rate pulse train femtosecond laser according to claim 2, characterized in that, The displacement system includes a Z-axis displacement stage, which is used to drive the molding substrate to move up and down. During operation, after each layer of powder molding is completed, the molding substrate is lowered by a preset layer thickness through the Z-axis displacement stage before the next layer of powder is laid and the powder molding is performed.

3. The precision laser selective melting system based on a high repetition rate pulse train femtosecond laser according to claim 3, characterized in that, The displacement system also includes a forming platform, which is set at the displacement output end of the Z-axis displacement stage. The forming platform is provided with a groove, and the forming substrate is set in the groove.

4. A precision laser selective melting system based on a high repetition rate pulse train femtosecond laser according to claim 1, characterized in that, The powder spreading system includes a powder spreading table, a scraper assembly, and an X-axis displacement stage. The scraper assembly is located at the displacement output end of the X-axis displacement stage, which drives the scraper assembly to move between the powder spreading table and the molding substrate to push the powder from the powder spreading table to the molding substrate.

5. A precision laser selective melting system based on a high repetition rate pulse train femtosecond laser according to claim 1, characterized in that, The scraper assembly includes a main scraper and a secondary scraper. The area between the main scraper and the secondary scraper is a powder receiving area for storing the powder to be spread. The main scraper is used to spread the powder evenly on the molding substrate, and the secondary scraper is used to prevent the powder from overflowing. The functions of the main scraper and the secondary scraper are interchanged when spreading powder for the next time.

6. A precision laser selective melting system based on a high repetition rate pulse train femtosecond laser according to claim 1, characterized in that, The environmental control system includes a vacuum pump, a gas cylinder, a barometer, and an oxygen sensor. The vacuum pump is used to extract gas from the molding chamber, the gas cylinder is used to fill the molding chamber with a predetermined amount of gas, the barometer is used to monitor the gas pressure inside the molding chamber, and the oxygen sensor is used to monitor the oxygen concentration inside the molding chamber.

7. A precision laser selective melting system based on a high repetition rate pulse train femtosecond laser according to claim 1, characterized in that, The scanning system includes a reflector, an electric optical shutter, a galvanometer, and a field lens. The pulsed laser output by the laser system first enters the electric optical shutter and the galvanometer sequentially through the reflector of the scanning system, then the laser is deflected by the galvanometer, and finally the laser is focused onto the surface of the powder material by the field lens.

8. A precision laser selective melting system based on a high repetition rate pulse train femtosecond laser according to claim 1, characterized in that, The galvanometer controls the laser deflection by rotation, with a maximum angular velocity ≥ rad / s; the field lens is an f-θ lens, used to linearly convert the galvanometer's deflection of the laser into the displacement of the laser focus on the focal plane.

9. A precision laser selective melting system based on a high repetition rate pulse train femtosecond laser according to claim 1, characterized in that, The high repetition rate mode-locked seed laser uses an ultrashort fiber resonator laser and achieves passive mode-locking using a semiconductor saturable absorber mirror, with a repetition rate ≥ GHz.

10. A precision laser selective melting system based on a high repetition rate pulse train femtosecond laser according to any one of claims 1-9, characterized in that, Before laser selective melting and forming, the environmental control system evacuates the forming chamber and fills it with inert gas. The control system slices the three-dimensional model and generates the scanning path for each slice. The displacement system drives the forming substrate to descend by a set layer thickness. The powder spreading system moves forward, pushing the powder from the powder spreading stage to the molding substrate, forming a powder layer of a set thickness on the surface of the molding substrate; After processing begins, the laser system outputs a high-repetition-rate femtosecond laser pulse train to the scanning system. The scanning system scans the powder with the focused laser spot according to the preset scanning path, causing the powder to selectively melt and form a continuous structure. The laser is then blocked, the displacement system moves the molding substrate down by one layer thickness, and the powder spreading system moves in the opposite direction to complete one reverse powder spreading operation. The laser is then allowed to pass through, and the next layer of powder is selectively melted, allowing it to bond with the previous layer. This process is repeated layer by layer until the entire printed part is formed.

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