LPBF metal 3D printing method and system based on discrete point dynamic regulation and control

Abstract

The invention relates to the technical field of metal 3D printing, and discloses an LPBF metal 3D printing method and system based on discrete point dynamic regulation, and the method comprises the steps: decomposing a slice layer contour range of a 3D model into a dot matrix with set density and uniformly distributed scanning points; setting laser parameters of each scanning point in the dot matrix, wherein the laser parameters comprise power and exposure time; based on a dot matrix, planning a scanning sequence of all scanning points as a scanning path; controlling the laser to scan according to the scanning path, and scanning each scanning point on the scanning path by adopting the corresponding laser parameter; and converting to the next layer of slice of the 3D model, and repeating the steps until the scanning of the whole 3D model is completed. According to the method, a traditional one-dimensional vector line scanning path is converted into a zero-dimensional and programmable dot matrix, each scanning point is independently endowed with scanning power and laser exposure time, inertia-free scanning of any geometric path and complex characteristics is achieved, and the method is suitable for aerospace lightweight dot matrix structures, medical porous implants and other application scenes.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal 3D printing, in particular to a LPBF metal 3D printing method and system based on dynamic regulation of discrete points. BACKGROUND

[0002] As one of the core processes in the field of metal additive manufacturing, laser powder bed fusion (LPBF) technology has been widely used in high-end manufacturing fields such as aerospace engine key components, medical implants, and high-end equipment precision parts, due to its outstanding advantages in high-precision forming and complex geometric structure manufacturing.

[0003] Currently, traditional LPBF metal 3D printing generally adopts vector scanning (continuous scanning) process, and the specific technical process is as follows: first, the three-dimensional model of the target part is converted into a two-dimensional plane by standard commercial software (such as Magics) (this process is called slicing), then imported into the 3D printing device software, and each two-dimensional plane is filled with "vector lines", that is, the two-dimensional plane is converted into a one-dimensional vector line, and the form of the vector line can be various, including but not limited to straight lines, broken lines, curves, and then the vector lines are given process parameters, mainly laser scanning power (P) and laser scanning speed (v). By adjusting the form of the scanning line and the process parameters, the management of the printing quality (thermal stress) and the printing efficiency can be realized, but the flexibility and upper limit of the management are limited. The specific shortcomings are reflected in four aspects: first, the scanning flexibility is low, and the single-pool point cannot be independently controlled. Traditional LPBF adopts vector line scanning mode, and the laser must move along the fixed track, which cannot independently control the single-pool point. Since the scanning path depends on the vector line segment, it is difficult to realize the rearrangement of points in any order, which leads to uneven distribution of heat accumulation and affects the forming quality. Second, the energy control precision is insufficient. The energy input depends on the laser scanning power (P) and the laser scanning speed (v), but the change of the scanning speed (v) will affect the stability of the molten pool, such as incomplete melting caused by high-speed scanning and over-melting caused by low-speed scanning. It is difficult to accurately control the exposure time of each point, which leads to inconsistent local energy input and affects the microstructure uniformity. At the same time, because the vector line scanning is continuous exposure, there is thermal interference between adjacent molten pools, and the temperature field is continuous, which makes it difficult to realize independent modulation. Third, it is difficult to optimize the accumulation of thermal stress. Traditional LPBF adopts fixed scanning strategy (such as interlayer rotation and partition scanning), which can make the thermal stress distribution more uniform to a certain extent, but cannot dynamically adjust the scanning order according to the real-time temperature field / temperature gradient. Because the path is continuous, the heat accumulation is concentrated in certain areas, which easily leads to defects such as warping and cracking. Fourth, the data processing method is limited. The slicing data of traditional LPBF is usually converted into vector line segments (G code), which cannot directly support point array scanning, leading to limited process optimization.

[0004] To improve the above-mentioned defects existing in the traditional vector scanning process, an LPBF metal 3D printing improvement method based on path thermal balance optimization is disclosed in the prior art. The improvement method evaluates the high forming risk area through a temperature field model, and dynamically adjusts the laser parameters (power, speed) and scanning path (vector merging / splitting) to reduce thermal stress. Although this method can improve the warping and collapse defects, it still has the following limitations: first, the path optimization granularity is insufficient, only local path secondary optimization is carried out for the "high forming risk area", and dynamic regulation and control at the point scanning level in the whole area is not realized, which may cause the temperature gradient in the non-high risk area to accumulate, affecting the overall forming precision. Second, the point scanning control is missing, and the vector merging or splitting strategy is based on the traditional vector scanning mode, which cannot realize accurate energy matching point by point. Although the skip scanning can disperse the heat input, it is difficult to cope with the thermal field changes of complex geometric structures. Third, the multi-parameter collaborative optimization is insufficient, and the adjustment of laser power and speed is limited by the fixed optimization function, without considering the three-dimensional parameter space of power-exposure time-point spacing under the point scanning mode, resulting in insufficient energy density control precision and affecting the microstructure uniformity.

[0005] In summary, neither the traditional LPBF vector scanning process nor the improved method based on path thermal balance optimization can meet the manufacturing requirements of high-precision, high-performance LPBF metal 3D printed parts in the current high-end manufacturing field, therefore, it is urgent to propose a more optimal LPBF process scheme to break through the above technical limitations and improve the quality and process stability of the formed parts. SUMMARY

[0006] The present application provides a kind of LPBF metal 3D printing method and system based on discrete point dynamic regulation and control, which converts the traditional one-dimensional vector line scanning path into zero-dimensional and programmable dot matrix, each scanning point is separately endowed with scanning power and laser exposure time, realizes the inertialess scanning of arbitrary geometric path, complex feature, is suitable for aerospace lightweight dot matrix structure, medical porous implant and other high-end application scenarios, fills the technical blank of existing metal 3D printing in precision-efficiency-material collaborative optimization.

[0007] The present application provides a kind of LPBF metal 3D printing method based on discrete point dynamic regulation and control, comprising: S1, the profile range of the slice layer of 3D model is decomposed into dot matrix with set density and uniform distribution of scanning points; S2, set the laser parameters of each scanning point in the dot matrix, each scanning point is subjected to laser scanning according to the laser parameters;Wherein, the laser parameters include power, exposure time; S3, based on dot matrix, the scanning order of all scanning points is planned as scanning path; S4, control the laser to scan according to the scanning path, and each scanning point on the scanning path is scanned by using the corresponding laser parameter thereof; S5, switch to the next slice of the 3D model, and repeat steps S1-S4 until the scanning of the entire 3D model is completed.

[0008] Further, in S1, the spacing of each scanning point in the dot matrix ranges from 15 to 150 μm.

[0009] Further, in S2, the single-point laser exposure parameters are set according to the dot matrix, and specifically: By switching between "high power + long exposure" and "low power + short exposure", the laser energy density window that can make the material form without defects is quickly determined; Within the determined laser energy density window, different parameter combinations of "high power + short exposure" and "low power + long exposure" are adjusted to find laser exposure parameters that meet the forming quality requirements and strength requirements.

[0010] Further, different laser scanning parameters and scanning paths in the dot matrix are selected according to the properties of the alloy for scanning.

[0011] Further, in S3, the dot matrix is divided into multiple partitions, each partition corresponds to a laser, and the scanning order of all scanning points in each partition is set as a partition scanning path, and multiple lasers simultaneously scan according to the corresponding partition scanning paths.

[0012] Further, according to the requirements of TSP (Traveling Salesman Problem) algorithm and heat balance, the scanning paths between the scanning points or the partition scanning paths are planned.

[0013] The application also provides a LPBF metal 3D printing system based on dynamic regulation of discrete points, which is based on the LPBF metal 3D printing method based on dynamic regulation of discrete points as described above, and the system comprises a high-power laser light source, a beam shaping module, a high-speed galvanometer scanning module, a point scanning control module, a powder laying module, an inert gas protection module and an online monitoring module, The online monitoring module monitors the molten pool in real time and feeds back signals to the point scanning control module, the high-power laser light source and the high-speed galvanometer scanning module; The point scanning control module transmits laying instructions to the powder laying module, transmits scanning instructions to the high-speed galvanometer scanning module, and transmits control instructions to the high-power laser light source and the beam shaping module by using the LPBF metal 3D printing method based on dynamic regulation of discrete points; The high-power laser light source is also connected to the light beam shaping module for beam expansion, collimation and dynamic focusing, and the light beam shaping module is connected to the high-speed galvanometer scanning module to realize laser scanning on the laser beam emitted by the molten pool. The powder laying module lays powder on the molten pool, and the inert gas protection module provides an inert atmosphere for the molten pool.

[0014] Further, the high-power laser light source adopts a fiber laser or a disc laser to provide a laser beam required for melting of metal powder. The light beam shaping module comprises an expander, a collimator and a dynamic focusing unit to ensure adjustable laser spot size. The high-speed galvanometer scanning module is composed of an X / Y-axis galvanometer to realize rapid deflection of the laser focal point in the processing plane. The point scanning control module controls the galvanometer through the LPBF metal 3D printing method based on dynamic regulation of discrete points, so that the laser moves according to the set scanning mode along the scanning path or the partition scanning path. The powder laying module comprises a powder supply cylinder and a powder laying scraper / roller to ensure uniform laying of metal powder for each slice. The inert gas protection module maintains a low-oxygen environment for the molten pool to prevent oxidation of the metal. The online monitoring module integrates an infrared thermal imager or a high-speed camera to monitor the molten pool in real time and feedback adjust the laser power or scanning speed.

[0015] The present application has the following advantages: 1. Flexibility of arbitrary path: supports high-precision forming of complex geometric features (such as honeycomb structure, conformal runner), and is not restricted by continuous scanning trajectory.

[0016] 2. Accurate control of heat input: through independent adjustment of point parameters, reduce thermal stress and deformation, and improve mechanical properties of parts.

[0017] 3. Wide material applicability: can adapt to high-reflectivity materials (such as copper alloy), brittle materials (such as tungsten) and other traditional LPBF difficult-to-machine materials.

[0018] 4. High efficiency and low defect: high-speed jumping of the galvanometer combined with pulse modulation to realize high production rate while suppressing pores, spheroidization and other defects. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The present application is a flowchart of the LPBF metal 3D printing method based on dynamic regulation of discrete points.

[0020] Figure 2 The present application is a structural diagram of the LPBF metal 3D printing system based on dynamic regulation of discrete points.

[0021] The objectives, functional characteristics and advantages of the present application will be further illustrated in conjunction with the embodiments with reference to the accompanying drawings. DETAILED DESCRIPTION

[0022] It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.

[0023] The present application introduces a high dynamic point scanning mode, which can continue to convert the traditional one-dimensional vector line scanning path into zero-dimensional and programmable dot matrix, support arbitrary geometric trajectories (including non-continuous jump), and realize inertia-free scanning of complex features. At the same time, the parameter logic is converted from the traditional laser scanning power (P) and laser scanning speed (v) to laser scanning power (P) and laser exposure time (t), each molten pool (scanning point) is individually assigned, wherein the power adjustable range is 15-500W, the step is 1W, the time adjustable range is ≥10μs, the step is ≥5μs, the complete uniform distribution of thermal stress and the independent modulation of temperature field can be realized. It is suitable for aerospace lightweight dot matrix structure, medical porous implant and other high-end application scenarios, and fills the technical gap of existing metal 3D printing in precision-efficiency-material collaborative optimization.

[0024] As shown in Figure 1 The present application provides a LPBF metal 3D printing method based on dynamic regulation of discrete points, which controls the laser focus to scan in discrete point mode through high dynamic galvanometer, breaks through the limitations of traditional LPBF vector line scanning, and the specific steps are as follows: S1, path discretization and dot matrix generation The contour range of the slice layer of the 3D model is divided into a dot matrix with a set density and uniform distribution of scanning points, the range of the distance between each scanning point in the dot matrix is 15-150μm, and each point corresponds to one scanning (melting) action of the laser.

[0025] S2, dynamic power-exposure time collaborative control Set the laser parameters of each scanning point in the dot matrix, and each scanning point performs one scanning of the laser according to the laser parameters; wherein the laser parameters include power and exposure time.

[0026] In one embodiment, single-point laser exposure parameters are set according to the dot matrix, specifically: Through the switching between "high power + long exposure" and "low power + short exposure", a laser energy density window that makes the material preliminarily formed and does not have obvious defects (such as ablation, warping or excessive melting) is quickly determined; Within the determined laser energy density window, further debugging is performed by constantly adjusting different parameter combinations such as "high power + short exposure" and "low power + long exposure" to find exposure parameters that meet the following specific forming quality requirements and strength requirements: ① Forming quality requirements: the forming structure surface is smooth and clear in profile, without obvious spheroidization, porosity or crack defects, and the dimensional accuracy error is controlled within ±0.01%.

[0027] ② Strength requirements: the tensile strength of the forming sample is not lower than the material and process requirements.

[0028] Finally, different laser scanning parameters and scanning paths in the dot matrix are selected according to the properties of the alloy to achieve the effect of independent adjustment of laser parameters (power, exposure time) at each scanning point, for example: High power short dwell (such as 300W, 50μs) is used for deep penetration of high melting point alloys (such as titanium alloy), and low power long dwell (such as 100W, 200μs) is used for fine forming of thin-walled structures. At the same time, pulse modulation technology can be combined to convert continuous laser into high frequency pulse (kHz-MHz), further reducing heat accumulation.

[0029] S3, plan the scanning order of all scanning points as a scanning path based on the dot matrix.

[0030] In one embodiment, multi-laser collaborative optimization can also be performed, that is, the dot matrix is divided into multiple partitions, each partition corresponds to a laser, and the scanning order of all scanning points in each partition is set as the partition scanning path, and multiple lasers scan according to their corresponding partition scanning paths.

[0031] In one embodiment, galvanometer efficiency optimization can also be performed, that is, the shortest path between scanning points is planned as a scanning path or a partition scanning path according to the dot matrix through a TSP (Traveling Salesman Problem) algorithm to reduce galvanometer idle time.

[0032] S4, control the laser to scan according to the scanning path, and use the corresponding laser parameters of each scanning point on the scanning path for scanning.

[0033] S5, switch to the next layer slice of the 3D model and repeat steps S1-S4 until the scanning of the entire 3D model is completed.

[0034] For example, Figure 2As shown, the application also provides a LPBF metal 3D printing system based on dynamic regulation of discrete points, which is based on the LPBF metal 3D printing method based on dynamic regulation of discrete points as described above, and the system comprises a high-power laser light source, a beam shaping module, a high-speed galvanometer scanning module, a point scanning control module, a powder laying module, an inert gas protection module and an online monitoring module.

[0035] (1) High-power laser light source The high-power laser light source is connected to the beam shaping module for beam expansion, collimation and dynamic focusing. The high-power laser light source uses a fiber laser or a disc laser (wavelength is usually 1064 nm or 1070 nm) to provide a high-energy density laser beam required for melting metal powder.

[0036] (2) Beam shaping module The beam shaping module is connected to the high-speed galvanometer scanning module to realize laser scanning of the laser beam emitted by the molten pool. The beam shaping module includes an expansion mirror, a collimation mirror and a dynamic focusing system to ensure that the laser spot size is adjustable (such as 50-200 μm) to adapt to different powder materials and processing requirements.

[0037] (3) High-speed galvanometer scanning module The high-speed galvanometer scanning module is composed of X / Y-axis galvanometers to realize rapid deflection of the laser focal point in the processing plane, and the scanning speed can reach several meters per second.

[0038] (4) Powder laying module The powder laying module lays powder on the molten pool, including a powder supply cylinder and a powder laying scraper / roller to ensure uniform laying of each layer of metal powder (layer thickness is usually 30-200 μm).

[0039] (5) Inert gas protection module The inert gas protection module provides an inert atmosphere for the molten pool to maintain a low-oxygen environment (such as argon or nitrogen) in the processing cabin to prevent metal oxidation.

[0040] (6) Point scanning control module The point scanning control module transmits powder laying instructions to the powder laying module, transmits scanning instructions to the high-speed galvanometer scanning module, and transmits control instructions to the high-power laser light source and the beam shaping module using the LPBF metal 3D printing method based on dynamic regulation of discrete points.

[0041] The point scanning control module controls the galvanometer through a real-time path planning algorithm (arbitrary point scanning or sequential scanning, which is a manually preset path or an algorithm generated path) to make the laser move in a point scanning mode (non-vector scanning) according to the preset path, supporting any complex trajectory.

[0042] (7) Online monitoring module The online monitoring module monitors the molten pool in real time and feeds back signals to the point scanning control module, high-power laser light source and high-speed galvanometer scanning module; the online monitoring module integrates an infrared thermal imager or high-speed camera to monitor the molten pool in real time and feed back to adjust the laser power or scanning speed.

[0043] The feedback adjustment of the online monitoring module is a closed-loop control process, and the specific principle is as follows: ①Signal acquisition: the infrared thermal imager or high-speed camera continuously collects image and temperature data of the molten pool while the laser is processing.

[0044] ②Feature extraction: the processing system analyzes these data in real time and extracts key feature parameters such as the width (W), length (L), area (Area) and maximum temperature (T_max) of the molten pool.

[0045] ③Comparison and judgment: compare the extracted real-time feature values with the ideal target values (or allowable range) under the current process parameters.

[0046] ④Closed-loop feedback control: according to the comparison deviation, the point scanning control module immediately issues adjustment instructions: When the size of the molten pool (such as the width) is too large and the temperature is too high: it is judged that the energy input is excessive, and there is a risk of burning through or splashing. The control module will immediately reduce the laser power and / or increase the scanning speed to reduce the heat input, so that the molten pool returns to the normal state.

[0047] When the size of the molten pool is too small and the temperature is too low: it is judged that the energy input is insufficient, and there is a risk of incomplete fusion or spheroidization. The control module will immediately increase the laser power and / or low scanning speed to increase the heat input to ensure that the powder is completely melted and well combined with the substrate.

[0048] Compared with the traditional continuous laser scanning scheme, the present application has the following significant advantages: 1. Significantly improve the forming precision and adaptability of complex structures Micron-level feature forming capability: through the discrete point scanning strategy, the laser energy can be accurately applied to the micro area (the point spacing can be adjusted to 10 μm level), realizing high-resolution forming, and the minimum feature size reaches ± 15 μm, which is several times higher than that of traditional continuous scanning (± 30 μm).

[0049] Complex geometry inertia-free forming: get rid of the continuous path continuity restriction of continuous scanning, support inertia-free high-fidelity manufacturing of complex features such as overhanging structure, dot lattice, internal flow channel, etc., and the corner precision is improved by more than 60%.

[0050] 2. Accurate control of heat input, and improvement of mechanical properties of parts Micro-area energy independent regulation: power and residence time of each scanning point can be dynamically adjusted to match heat input with local geometry / material properties, improving residual stress uniformity by over 80%.

[0051] Active thermal management: optimize thermal stress accumulation through regional jump scanning (e.g. chessboard, spiral filling), reduce warping deformation, and control flatness error of large-size parts (>200mm) within 0.1mm / m.

[0052] 3. Expand material process window, break through extreme material processing bottleneck High-reflectivity material high densification forming: pulse point scanning mode overcomes laser reflection loss of copper and aluminum alloys, with copper alloy density reaching 99.2% (traditional method <98%) and conductivity close to that of forged parts.

[0053] Brittle material low defect manufacturing: short residence time (<100μs) suppresses thermal cracks in materials such as tungsten and ceramics, with crack rate reduced by 80% and relative density >99%.

[0054] 4. Maximize equipment dynamic performance, improve production efficiency Mirror efficiency release: point-to-point path optimization based on TSP (Traveling Salesman Problem) algorithm, with mirror high-speed jump ratio increased from 40% to 85%, and complex structure printing efficiency improved by 2-3 times.

[0055] Multi-laser collaborative expansion: supports multi-laser head partitioning and parallel point scanning, shortening the manufacturing cycle of large parts (such as aircraft engine casings) by 50%.

[0056] In summary, the key technical points of the present application are: 1. Process flexibility improved by an order of magnitude from one-dimensional vector line scanning to zero-dimensional point scanning. One-dimensional vector line scanning has direction and length, and its process flexibility has a definite upper limit. Zero-dimensional point scanning has no direction and length, and its process flexibility has no upper limit. Its path planning is not dependent on geometric constraints, but only on process quality and efficiency requirements.

[0057] 2. Precise point-by-point energy regulation. The two key parameters of laser scanning power (P) and laser exposure time (t) are dynamically matched with laser model (spot diameter), printing material, and layer thickness to achieve precise point-by-point energy regulation.

[0058] 3. Point scanning path generation logic. Non-continuous point scanning strategies (such as chessboard, spiral, and random point sequence) disperse heat accumulation; point spacing self-adaptive adjustment algorithm (dynamically reduces / enlarges point spacing according to real-time temperature feedback).

[0059] The present application is applied in high-value aerospace parts in the following ways: ①Turbine blade: Precise control of energy input in thin-walled areas (≤0.3mm) of the blade body through point scanning, eliminating local burn-through defects caused by traditional line scanning.

[0060] ②Spacecraft fuel nozzle: Use of point-to-point jump scanning strategy to reduce residual stress in the internal flow channel and avoid crack initiation under high pressure.

[0061] Technical advantage: Meet the requirement of NASM (American Aerospace Material Standard) for internal defect rate ≤0.01%.

[0062] In the personalized customization of medical implants, the application methods include: ①Porous titanium alloy bone scaffold: Adjust the porosity (gradient 50%-90%) through point scanning to match the mechanical properties of the patient's bone and the cell growth requirements.

[0063] ②Dental implant: Based on CBCT data, directly generate point scanning path to realize the biomechanical optimization of root canal thread structure.

[0064] Technical advantage: Surface roughness can be controlled within Ra5-20μm (promote bone integration), and avoid the powder adhesion problem of electron beam melting (EBM).

[0065] In the precise mold conformal cooling water channel, the application methods include: ①Use point scanning + real-time infrared monitoring to print complex spiral cooling channels (diameter φ1mm±0.05mm) inside the mold, and improve the cooling efficiency by 40%.

[0066] ②Through point energy grading control, realize the synchronous achievement of mirror polishing (Ra≤0.8μm) of the inner wall of the water channel and high strength of the outer cavity.

[0067] Technical advantage: Solve the design limitation of curved water channel that cannot be realized by traditional drilling process.

[0068] In the application of metamaterials and functional gradient materials, the application methods include: ①Acoustic metamaterial: Adjust the stiffness of the unit structure (energy density difference ±15%) point by point to realize the shielding of specific frequency band (such as 500-1000Hz) sound waves.

[0069] ②Thermal protection gradient material: Realize the gradual change of micro components from tungsten (melting point 3422℃) to copper (thermal conductivity 401W / mK) in a single printing.

[0070] Technical barrier breakthrough: Traditional LPBF cannot realize sub-millimeter gradient due to material switching delay.

[0071] In the application of micro-nano scale electronic devices, the application methods include: ① RF device heat dissipation substrate: point scanning printing microneedle array (height 50 μm, pitch 10 μm), using surface area multiplication effect to improve heat dissipation performance.

[0072] ② Flexible circuit metal interconnection: low-temperature point scanning silver nanoparticle wire (conductivity ≥80%IACS) on a polyimide substrate.

[0073] Innovation: combined with short pulse (ns level) point scanning to suppress the heat affected zone.

[0074] The application in space in-orbit manufacturing, application mode includes: ① In the microgravity environment, through point scanning + gas flow field cooperative control, solve the problem of metal molten pool drift, print satellite spare parts.

[0075] ② Use point scanning low heat input characteristics, complete aluminum alloy structure repair under the condition of limited power (≤500W) in space station.

[0076] Technical adaptability: compared with traditional LPBF, reduce 60% inert gas consumption.

[0077] It should be noted that in this paper, the term "includes", "contains" or any other variant thereof is intended to cover non-exclusive inclusion, so that the process, device, article or method including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or includes elements inherent to such process, device, article or method. Without more limitations, the element defined by the statement "includes a" does not exclude the existence of other identical elements in the process, device, article or method including the element.

[0078] The above only describes the preferred embodiments of the application, and does not limit the patent scope of the application, any equivalent structure or equivalent process transformation using the content of the application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the application.

Claims

1. A method for LPBF metal 3D printing based on discrete point dynamic control, characterized in that, include: S1. Decompose the outline of the slice layer of the 3D model into a lattice with a set density and uniformly distributed scanning points. S2. Set the laser parameters for each scanning point in the dot matrix, and perform one laser scan for each scanning point according to the laser parameters; wherein, the laser parameters include power and exposure time; S3. Based on the dot matrix, plan the scanning order of all scanning points as the scanning path; S4. Control the laser to scan along the scanning path, and scan each scanning point on the scanning path using its corresponding laser parameters; S5. Switch to the next slice of the 3D model and repeat steps S1 to S4 until the entire 3D model has been scanned.

2. The LPBF metal 3D printing method based on discrete point dynamic control according to claim 1, characterized in that, In S1, the spacing between the scanning points in the dot matrix ranges from 15 to 150 μm.

3. The LPBF metal 3D printing method based on discrete point dynamic control according to claim 1, characterized in that, In step S2, the single-point laser exposure parameters are set according to the dot matrix, specifically: By switching between "high power + long exposure" and "low power + short exposure", the laser energy density window that allows the material to be shaped without defects can be quickly determined; Within the established laser energy density window, different parameter combinations of "high power + short exposure" and "low power + long exposure" are continuously adjusted to find laser exposure parameters that meet the requirements for molding quality and strength.

4. The LPBF metal 3D printing method based on discrete point dynamic control according to claim 3, characterized in that, Different laser scanning parameters and scanning paths within the dot matrix are selected based on the properties of the alloy.

5. The LPBF metal 3D printing method based on discrete point dynamic control according to claim 1, characterized in that, In step S3, the dot matrix is ​​divided into multiple partitions, each partition corresponds to a laser, and the scanning order of all scanning points in each partition is set as the partition scanning path. Multiple lasers scan simultaneously according to their corresponding partition scanning paths.

6. The LPBF metal 3D printing method based on discrete point dynamic control according to claim 5, characterized in that, Based on the requirements of the TSP algorithm and heat balance of the dot matrix, a scanning path or a partitioned scanning path is planned.

7. An LPBF metal 3D printing system based on discrete point dynamic control, characterized in that, The LPBF metal 3D printing method based on discrete point dynamic control according to any one of claims 1 to 6, the system includes a high-power laser source, a beam shaping module, a high-speed galvanometer scanning module, a point scanning control module, a powder delivery module, an inert gas protection module, and an online monitoring module. The online monitoring module monitors the molten pool in real time and sends signals back to the point scanning control module, the high-power laser source, and the high-speed galvanometer scanning module. The point scanning control module transmits powder spreading instructions to the powder spreading module, transmits scanning instructions to the high-speed galvanometer scanning module, and transmits control instructions to the high-power laser source and beam shaping module using the LPBF metal 3D printing method based on discrete point dynamic control. The high-power laser source is also connected to the beam shaping module for beam expansion, collimation and dynamic focusing. The beam shaping module is connected to the high-speed galvanometer scanning module to perform laser scanning on the laser beam emitted from the molten pool. The powder feeding module lays powder in the molten pool, and the inert gas protection module provides an inert atmosphere to the molten pool.

8. The LPBF metal 3D printing system based on discrete point dynamic control according to claim 7, characterized in that, The high-power laser source uses a fiber laser or a disk laser to provide the laser beam required for melting metal powder; The beam shaping module includes a beam expander, a collimator, and a dynamic focusing unit to ensure that the laser spot size is adjustable. The high-speed galvanometer scanning module consists of X / Y axis galvanometers, enabling rapid deflection of the laser focus within the processing plane; The point scanning control module controls the galvanometer using the LPBF metal 3D printing method based on discrete point dynamic adjustment, so that the laser moves according to the set scanning mode along the scanning path or the partitioned scanning path. The powder feeding module includes a powder supply cylinder and a powder spreading scraper / roller to ensure that the metal powder of each slice is evenly spread. The inert gas protection module maintains a low-oxygen environment in the molten pool to prevent metal oxidation; The online monitoring module integrates an infrared thermal imager or a high-speed camera to monitor the molten pool morphology in real time and adjust the laser power or scanning speed accordingly.

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