Laser cladding 3D / 4D printing system and method

Abstract

The invention provides a laser cladding 3D / 4D printing system and method, and the method comprises the following steps: S1, constructing a three-dimensional model of a to-be-printed piece, slicing the three-dimensional model, and generating a two-dimensional interface diagram of each layer of printing; s2, the additive manufacturing material of the current layer is melted through first laser to form a cladding layer; s3, carrying out micro-shaping on the surface of the cladding layer by using second laser, firstly carrying out micro-shaping on rough and hole defect areas on the surface of the cladding layer, and then carrying out point heat source irradiation on the surface of the cladding layer to eliminate residual stress of the cladding layer; and S4, the steps S2-S3 are repeated, the additive manufacturing process of each layer is completed, and a printed piece is obtained. According to the method, ultrafast laser shaping is carried out on the cladding layer in the laser 3D / 4D printing process, so that the problems of residual stress, interface-surface holes, uneven roughness and powder agglomeration and accumulation of the cladding layer of a laser 3D / 4D printing workpiece are solved, and the quality of the laser 3D / 4D printing workpiece is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of laser additive manufacturing, and specifically relates to a laser cladding 3D / 4D printing system and method. Background Art

[0002] Laser 3D / 4D printing (such as selective laser sintering (SLS) and selective laser melting (SLM), as advanced additive manufacturing technologies, has demonstrated unique advantages in industry, medicine, and scientific research. These advantages include: ① High-precision and complex structure manufacturing capabilities. For example, laser beam focusing diameters can reach 20 μm-100 μm, enabling micron-level resolution (for example, metal printing accuracy can reach ± 0.05 mm), making it suitable for manufacturing complex cavities, honeycomb structures, or topology-optimized components that are difficult to process using traditional methods; ② Material diversity, such as support for a variety of materials, including metals (titanium alloys, aluminum alloys, nickel-based high-temperature alloys), ceramics, and polymers (such as nylon PA12). Direct metal forming is a core advantage that distinguishes it from other 3D printing technologies; ③ No molds are required and rapid iteration is required, going directly from digital models to physical parts, eliminating the mold development process and shortening the new product development cycle (for example, the production time of automotive prototypes can be reduced by 70%); ④ High material utilization. Powder bed technology can achieve an unmelted material recovery rate of over 95%, significantly reducing the loss of expensive materials (such as titanium alloys).

[0003] Although laser 3D / 4D printing has many advantages, it also has many obvious defects, such as: ① Residual stress defects. During the laser cladding 3D / 4D printing process, the non-uniform thermal cycle induced by the high-energy laser can lead to thermoelastic stress, phase change stress, warping deformation and interface failure; ② Surface roughness and unevenness defects. Due to the spheroidization effect or step effect and the influence of powder adhesion, the surface of the laser cladding 3D / 4D printed workpiece will appear rough and uneven; ③ Interface-surface hole defects, including keyhole pores formed due to the instability of the molten pool dynamics, unfused holes formed due to insufficient laser energy density, and powder agglomeration and accumulation due to poor powder fluidity. Summary of the Invention

[0004] The purpose of the present invention is to overcome the problems in the prior art of large residual stress in the cladding layer of laser 3D / 4D printed workpieces and holes and roughness on the interface-surface of the cladding layer.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions: A laser cladding 3D / 4D printing method comprises the following steps: S1. Build a 3D model of the part to be printed based on its parameters, slice the 3D model, and generate a 2D interface diagram for each printed layer. S2, using the first laser to melt the additive manufacturing material of the current layer and form a cladding layer; S3. Micro-shaping the surface of the cladding layer using a second laser. First, the surface roughness and hole defect areas of the cladding layer are micro-shaped by adjusting the process parameters of the second laser. Then, the emission power of the second laser is adjusted to irradiate the surface of the cladding layer with a point heat source to eliminate residual stress in the cladding layer. The process parameters for micro-shaping the surface roughness and hole defect areas of the cladding layer by the second laser are adjusted based on the optical information of the cladding layer captured by the holographic camera and the surface roughness and hole defect information of the cladding layer acquired in real time by the stress wave emitted by the pulse generator. S4. Repeat steps S2-S3 to complete the additive manufacturing process for each layer until a printed part is obtained.

[0006] Furthermore, a holographic camera is used to obtain a dynamic hologram of the surface of the cladding layer, which is analyzed by a spectrometer to calculate the arithmetic mean roughness parameters of the surface of the cladding layer. Combined with the stress wave fluctuation signal obtained by the stress wave sensor, a roughness joint evaluation model for dual-modal detection is established to calculate the comprehensive roughness value of the surface of the cladding layer. The surface roughness, hole requirements and corresponding mechanical properties of the cladding layer are judged through the correlation mechanism of detection data and parameter adjustment, as well as the real-time feedback and closed-loop control process to adjust the process parameters of the second laser in real time, thereby completing real-time laser processing correction and ultrafast laser micro-shaping of the defective areas on the surface of the cladding layer.

[0007] Furthermore, in step S3, the emission power of the second laser for performing point heat source irradiation on the surface of the cladding layer is adjusted according to the residual stress information on the surface of the cladding layer obtained in real time by the X-ray stress detection device.

[0008] Furthermore, the X-ray stress detection device includes an X-ray generator, an X-ray detector and an X-ray measurement recorder. The X-ray generator emits X-rays to the surface of the cladding layer, the X-ray detector detects the change information of the X-ray diffraction peak position in the surface area of the cladding layer, and the X-ray measurement recorder measures and records the diffraction angle in real time. The real-time diffraction angle data is converted and processed by an industrial computer to obtain the residual stress information on the surface of the cladding layer.

[0009] Furthermore, steps S2, S3, and S4 are performed in a vacuum heating chamber, and the pressure and temperature inside the vacuum heating chamber are controlled in real time by a vacuum pumping device and a heating device.

[0010] In addition, the present invention also provides a laser cladding 3D / 4D printing system, which is used in the above-mentioned laser cladding 3D / 4D printing method, including an industrial computer, a laser 3D / 4D printing mechanism, an ultrafast laser shaping mechanism, a holographic camera, a pulse generator, a stress wave sensor, a spectrometer, an X-ray stress detection device and a processing platform for carrying printed parts; the laser 3D / 4D printing mechanism emits a first laser to melt the additive manufacturing material to form a cladding layer; the ultrafast laser shaping mechanism emits a second laser to shape the cladding layer; the holographic camera is electrically connected to the spectrometer, and the laser 3D / 4D printing mechanism, ultrafast laser shaping mechanism, pulse generator, stress wave sensor, spectrometer, and X-ray stress detection device are all electrically connected to the industrial computer.

[0011] Furthermore, the ultrafast laser shaping mechanism includes an ultrafast laser, and a first reflector, a half-wave plate, a polarization beam splitter, a spatial light modulator, a 4F optical information processing component, a second reflector and a laser probe arranged in sequence along the laser emission optical path of the ultrafast laser.

[0012] Furthermore, a flip mirror is provided on the optical path between the 4F optical information processing component and the second reflector, so that a branch optical path is generated on the optical path that can be incident on the spectrometer.

[0013] Furthermore, the above-mentioned laser cladding 3D / 4D printing system also includes a vacuum heating chamber, and the laser processing head of the laser 3D / 4D printing mechanism, the laser probe of the ultrafast laser shaping mechanism, the holographic camera, the pulse generator, the stress wave sensor, the X-ray stress detection device and the processing platform are all vacuum-sealed and arranged in the vacuum heating chamber.

[0014] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention performs ultrafast laser shaping on the cladding layer during the laser 3D / 4D printing process to eliminate the residual stress, interface-surface holes, uneven roughness and powder agglomeration and accumulation problems of the cladding layer of the laser 3D / 4D printed workpiece, thereby improving the quality of the laser 3D / 4D printed parts; and in the ultrafast laser shaping process, it is designed to first shape the surface roughness and hole defects of the cladding layer, and then eliminate the residual stress of the cladding layer. In this way, the effect of the ultrafast laser in the shaping process of the surface roughness and hole defects of the cladding layer can be used to improve part of the residual stress, thereby reducing the energy for subsequent residual stress elimination of the cladding layer and reducing production costs.

[0015] (2) The present invention uses a combination of optical information of the cladding layer captured by a holographic camera and the fluctuation signal of the stress wave to perform online in-situ detection of the surface roughness and hole defects of the cladding layer. At the same time, X-rays are used to perform online in-situ detection of the residual stress of the cladding layer. According to the detection results, the cladding layer is locally selectively subjected to ultrafast laser shaping, which not only improves the efficiency and accuracy of the cladding layer shaping, but also can further reduce the production cost.

[0016] The present invention will be described in further detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic structural diagram of the laser cladding 3D / 4D printing system of the present invention; Figure 2 It is a working principle diagram of the laser cladding 3D / 4D printing method of the present invention.

[0018] Explanation of reference numerals: 1, industrial computer; 2, ultrafast laser; 3, first reflector; 4, half-wave plate; 5, polarization beam splitter; 6, spatial light modulator; 7, first lens; 8, first laser reflector; 9, spatial filter; 10, second laser reflector; 11, second lens; 12, flip mirror; 13, third lens; 14, spectrometer; 15, second reflector; 16, laser probe; 17, holographic camera; 18, pulse generator; 19, X-ray generator generator; 20. X-ray detector; 21. X-ray measurement recorder; 22. Laser processing head; 23. Shielding gas inlet mechanism; 24. Optical path scanning mechanism; 25. Printing laser generator; 26. Feeding system; 27. Printed part; 28. Stage; 29. Horizontal rotating stage; 30. Vertical rotating stage; 31. Bottom support platform; 32. Molten pool; 33. Cladding layer; 34. Pressure sensor; 35. Temperature sensor; 36. Vacuuming device; 37. Heating device. DETAILED DESCRIPTION

[0019] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0020] In the description of the present invention, it should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention.

[0021] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "install", "connect" and "connect" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, a conflicting connection or an integral connection. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0022] The terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, features specified as "first" or "second" may explicitly or implicitly include one or more of such features; and in the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0023] like Figure 1 and Figure 2 As shown, an embodiment of the present invention provides a laser cladding 3D / 4D printing method, comprising the following steps: S1. Build a 3D model of the part to be printed based on its parameters, slice the 3D model, and generate a 2D interface diagram for each printed layer. S2, using the first laser to melt the additive manufacturing material of the current layer and form a cladding layer 33; S3, using a second laser to micro-shape the surface of the cladding layer 33. First, by adjusting the process parameters of the second laser, the surface roughness and hole defect areas of the cladding layer 33 are micro-shaped. Then, by adjusting the emission power of the second laser, the surface of the cladding layer 33 is irradiated with a point heat source to eliminate the residual stress of the cladding layer 33. S4. Repeat steps S2-S3 to complete the additive manufacturing process for each layer until a printed part is obtained.

[0024] In this embodiment, ultrafast laser shaping is performed on the cladding layer 33 during the laser 3D / 4D printing process to eliminate the residual stress, interface-surface holes, uneven roughness, and powder agglomeration and accumulation problems of the cladding layer of the laser 3D / 4D printed workpiece, thereby improving the quality of the laser 3D / 4D printed parts; and in the ultrafast laser shaping process, it is designed to first shape the surface roughness and hole defects of the cladding layer 33, and then eliminate the residual stress of the cladding layer 33. In this way, the effect of the ultrafast laser in the shaping process of the surface roughness and hole defects of the cladding layer 33 can be used to improve part of the residual stress, thereby reducing the energy for eliminating the residual stress of the subsequent cladding layer 33 and reducing production costs.

[0025] As a specific embodiment, step S1 specifically includes: obtaining parameters of the part to be printed, such as size, shape, and material; using these parameters to construct a three-dimensional model of the part to be printed using computer-aided design software; and obtaining the plasticity parameters, elasticity parameters, and yield strength parameters of the part to be printed, in order to optimize the ultrafast laser shaping process parameters. The optimized ultrafast laser shaping process parameters are stored in the industrial computer 1 as reference target parameters for the subsequent ultrafast laser shaping process of the cladding layer 33. After the three-dimensional model is constructed, the three-dimensional model is sliced. Slicing is the process of decomposing the three-dimensional model into a series of planar layers. Each slice represents a two-dimensional interface image of a printing operation required for the part on that layer. For each planar layer, the computer software generates an additive manufacturing path based on the parameters of the part to be printed and the characteristics of the material. Each additive manufacturing path specifies the method of laser movement on each layer to achieve the desired shape and structure.

[0026] As a specific implementation method, step S2 specifically includes: the industrial computer 1 sends an instruction to the feeding system 26 to feed the current layer of additive manufacturing material (i.e., a thin layer of powder) into the laser processing head 22, and at the same time, the industrial computer 1 sends a laser instruction to the laser 3D / 4D printing mechanism, which is transmitted to the laser processing head 22 through the optical path scanning mechanism 24 and emits a high-energy first laser to "sinter" the thin layer of powder on the bottom layer and gradually form a cladding layer 33.

[0027] Optimally, while the feeding system 26 is delivering additive manufacturing materials to the laser processing head 22 , an inert gas is simultaneously fed into the laser processing head 22 through the protective gas inlet mechanism 23 to prevent oxidation of thin layers of powder during the laser 3D / 4D printing process.

[0028] In some embodiments, in the above step S3, the process parameters for the second laser to perform micro-shaping on the surface roughness and hole defect areas of the cladding layer 33 can be adjusted according to the optical information of the cladding layer 33 captured by the holographic camera 17 and the surface roughness and hole defect information of the cladding layer 33 obtained in real time by the stress wave emitted by the pulse generator 18.

[0029] Specifically, the holographic camera 17 and the pulse generator 18 are placed near the area of the cladding layer 33 near the molten pool 32 to be detected. The holographic camera 17 captures optical information of the cladding layer 33, and processes the captured optical signal through the spectrometer 14 and transmits it to the industrial computer 1 to obtain a stripe pattern (i.e., a dynamic hologram) on the surface of the cladding layer 33, thereby detecting and analyzing the hole distribution and surface roughness of the cladding layer 33 in real time; at the same time, the pulse generator 18 emits a stress wave to the defective area on the surface of the cladding layer 33. The stress wave enters the detection part and generates a series of changes in refraction and diffuse scattering in the defective area with a certain surface roughness and holes in the cladding layer 33. The changed stress wave fluctuation signal is detected by the stress wave sensor attached to the holographic camera 17. The received fluctuation signal is transmitted to the industrial computer 1, and the detector set inside the industrial computer 1 processes the fluctuation signal. When the industrial computer 1 receives the fluctuation signal of the surface roughness of the cladding layer 33 and the hole defect processed by the detector, as well as the optical signal and dynamic hologram processed by the spectrometer 14, the surface roughness of the cladding layer 33, the hole requirements and the corresponding mechanical properties are judged through the association mechanism of detection data and parameter adjustment and the real-time feedback and closed-loop control process to adjust the micro-shaping process parameters transmitted by the industrial computer 1 to the ultrafast laser shaping mechanism in real time, thereby completing the mathematical mapping of roughness quantification, threshold setting and laser parameter adjustment, realizing the closed loop from detection-adjustment-verification, and finally completing real-time laser processing correction and ultrafast laser micro-shaping of the defective area on the surface of the cladding layer 33.

[0030] By adjusting appropriate ultrafast laser parameters, protruding materials clumped together in the cladding layer 33 can be instantly dispersed and detached. It can also disperse agglomerated particles on the surface of the cladding layer 33, thereby achieving improved surface smoothness at the interface between the cladding layer 33 and the printed part 27. Furthermore, the ultrafast laser can perform a secondary polishing on the rough surface of the cladding layer 33, ultimately achieving a smooth, low-roughness interface without holes in the cladding layer of the laser cladding 3D / 4D printing process. Using an ultrafast laser with adjusted process parameters, micro-shaping is performed on cladding layers 33 with surface roughness greater than a set threshold, and the process continues until the industrial computer 1 detects in real time that the surface roughness of the cladding layer 33 during the laser cladding 3D / 4D printing process is less than the set threshold.

[0031] In an optimized implementation method, in this embodiment, an ultrafast laser with adjusted process parameters is used to perform micro-shaping on the cladding layer 33 whose surface roughness is greater than a set threshold. The introduction of a correlation mechanism between detection data and parameter adjustment includes roughness quantification and threshold setting, as well as mathematical mapping of laser parameter adjustment. The roughness quantification and threshold setting include using a holographic camera 17 to obtain a dynamic hologram of the surface of the cladding layer 33, analyzing the surface stripe pattern through a spectrometer 14, calculating the arithmetic average roughness parameter Ra of the surface of the cladding layer 33, and then combining the fluctuation signal of the stress wave sensor (the reflection / scattering intensity of the stress wave on the rough surface is positively correlated with the roughness) to establish a roughness joint evaluation model for dual-modal detection.

[0032] The average roughness parameter Ra is calculated as follows: ; Where M and N are the number of points on the plane, x j 、y i is the horizontal and vertical coordinates of the position of the point in the plane, It is the average height of all the points on the reference surface.

[0033] The formula for calculating the comprehensive roughness value of the roughness joint evaluation model is as follows: Where, is the weight coefficient, where , is the rate of change of stress wave amplitude.

[0034] In this embodiment, the morphology analysis of the holographic camera 17 and the mechanical property detection of stress waves are combined through the collaborative innovation of dual-modal detection to form an "optical-mechanical" composite detection system. Compared with the single CCD camera or pulse laser solution used in the existing technology, the detection accuracy is improved by at least 40%, and the roughness detection error calculated by this dual-modal detection is <0.05 μm.

[0035] The general industrial standards for the surface roughness of laser cladding 3D / 4D printed parts are the following four levels: ① Ordinary mirror processing level: roughness is 0.4-0.8 μm; ② Clearer mirror processing level: roughness is 0.3-0.4 μm; ③ High-quality mirror processing level: roughness is reduced to 0.05-0.3 μm; ④ Ultra-high standard mirror processing level: roughness is less than 0.05 μm.

[0036] The holographic camera 17 scans the plane of a single cladding layer 33 to obtain the horizontal and vertical coordinate data of all the points in the plane of the single cladding layer 33 and transmits it to the industrial computer 1. The average roughness parameter Ra is calculated using the above formula. Combined with the mechanical properties of stress waves, the comprehensive roughness value of the cladding layer 33 is calculated and processed using the roughness joint evaluation model. This is used as the measured roughness value of the surface of the cladding layer 33. If the measured roughness value exceeds a set threshold (for example, 0.4 μm), the industrial computer 1 sends a command to the ultrafast laser shaping mechanism to perform micro-shaping on the surface of the cladding layer 33. The ultrafast laser shaping mechanism then performs impact scanning on the cladding layer 33 with a femtosecond ultrafast laser.

[0037] Specifically, the laser parameters of the ultrafast laser shaping mechanism are adjusted according to the measured roughness. The mathematical mapping of the laser parameter adjustment includes a power adjustment model and energy density calculation. The power adjustment model includes setting a power adjustment formula based on the linear relationship between the roughness value and the laser energy: ; In the formula is the reference power (such as ), k is the adjustment coefficient (such as 20 W / μm), R is the measured roughness, R th is the threshold value (e.g. 0.4 μm). th When , the power increases linearly with the roughness.

[0038] The energy density calculation is performed using the relationship between the pulse energy and power of the ultrafast laser, specifically:

[0039] In the formula is the pulse width (e.g. 50 fs), f rep For the repetition frequency (such as 100 kHz), by adjusting P and , control the energy density within the range of 5-10 J / cm² (experiments have verified that this range can effectively eliminate roughness without damaging the material).

[0040] Preferably, this embodiment adopts a real-time feedback and closed-loop control process to perform ultrafast laser shaping on the surface roughness and hole defects of the cladding layer 33. Specifically, the real-time feedback and closed-loop control process includes data acquisition, parameter pre-adjustment and real-time correction; wherein, the data acquisition includes: the holographic camera 17 collects the surface morphology of the cladding layer 33 at a certain rate (for example, 1000 fps), the stress wave sensor synchronously obtains the corresponding high-frequency fluctuation signal (such as 1 MHz fluctuation signal), and the industrial computer 1 calculates the comprehensive roughness value in real time; the parameter pre-adjustment includes an LSTM neural network trained based on historical data to predict the optimal laser parameters (such as power and scanning speed) corresponding to the current roughness, for example: when Ra = 0.6 μm, the predicted power is 16 W and the scanning speed is 200 mm / s; when Ra = 0.8 μm, the predicted power is 20 W and the scanning speed is 150 mm / s; the real-time correction includes verifying the roughness change through secondary detection after each shaping, if the residual roughness R res >0.15R th , then start the secondary adjustment, and the adjustment step is 30% of the initial value.

[0041] Furthermore, the aforementioned secondary inspection to verify roughness changes involves detecting surface roughness and void defects in the cladding layer 33 and then performing an ultrafast zoning and shaping process. Specifically, this involves an intelligent defect region segmentation strategy and a combination of spatial grids and dynamic masks. This intelligent defect region segmentation strategy includes partitioning criteria and density clustering based on defect type and density. Defect classification involves analyzing the grayscale distribution of the hologram and the stress wave spectrum to distinguish between roughness regions (dense hologram fringes and significant stress wave dispersion) and void regions (dark hologram spots and significant stress wave attenuation). Density clustering involves clustering defect point clouds using the DBSCAN algorithm (density-based clustering algorithm). Specifically, high-density areas (defect point spacing <50 μm) are classified as "severe defect areas" and are impacted point by point using high-energy lasers (energy density 8-10 J / cm²). Medium-density areas (defect point spacing 50-100 μm) are classified as "general defect areas" and are scanned and shaped using medium-energy (5-8 J / cm²). Low-density areas (defect point spacing >100 μm) are classified as "minor defect areas" and are polished using low-energy (3-5 J / cm²).

[0042] The combination of spatial gridding and dynamic masking includes grid division and dynamic mask generation. Specifically, the grid division involves dividing the surface of the cladding layer 33 into 100×100 μm grid cells, with each cell partitioned based on defect parameters (roughness, number of holes). The dynamic mask generation involves using a spatial light modulator (SLM) to generate a laser mask that matches the defect partitioning. Specifically, a circular mask with a diameter of 1.5 times the hole diameter is generated for the hole area to ensure complete coverage of the defect. A linear scanning mask is generated for the roughness area, with the scanning line spacing being 1 / 2 the roughness wavelength (e.g., 25 μm for a roughness wavelength of 50 μm).

[0043] In this embodiment, a linear mapping formula between roughness and laser power and an energy density calculation model are established through a quantitative parameter adjustment model to achieve precise control of parameters; and a clustering partitioning algorithm based on defect density and type is established through intelligent zoning and dynamic masking. Combined with the SLM mask generation technology, "partition-parameter" shaping is achieved. Compared with the unified parameter processing in the existing technology, the defect elimination efficiency can be improved by at least 60%.

[0044] In other embodiments, in step S3, the emission power of the second laser for point heat source irradiation on the surface of the cladding layer 33 is adjusted according to the residual stress information on the surface of the cladding layer 33 obtained in real time by the X-ray stress detection device.

[0045] Specifically, the X-ray stress detection device includes an X-ray generator 19, an X-ray detector 20, and an X-ray measurement and recording device 21. After the rough, porous defective area of the cladding layer 33 is shaped, the X-ray generator 19 emits X-rays onto the surface of the cladding layer 33. The X-ray detector 20 detects changes in the X-ray diffraction peak position on the surface of the cladding layer 33. The X-ray measurement and recording device 21 measures and records the diffraction angle in real time. The real-time diffraction angle data is converted and processed by the industrial computer 1 to obtain residual stress information on the surface of the cladding layer 33. The residual stress information on the surface of the cladding layer 33 includes the magnitude and distribution of the residual stress on the surface of the cladding layer 33. Based on this residual stress information on the surface of the cladding layer 33, the industrial computer 1 sends parameter adjustment information to the ultrafast laser shaping mechanism. The ultrafast laser shaping mechanism adjusts the ultrafast laser power it emits based on this parameter adjustment information to complete point heat source irradiation of the cladding layer 33 of the printed part with different heat levels. The irradiation of this local point heat source causes slight plastic deformation on the surface of the cladding layer 33, which can not only offset the tensile stress at a certain depth on the surface of the laser 3D / 4D printed part and introduce a residual compressive stress field at the same time, but also effectively improve the mechanical properties of the laser 3D / 4D printed part.

[0046] In an optimized implementation, both the laser printing and cladding layer shaping processes in this embodiment are performed within a sealed vacuum heating chamber, with the pressure and temperature within the vacuum heating chamber controlled in real time by a vacuum pump 36 and a heating device 37. The high vacuum environment of the vacuum heating chamber not only prevents the presence of oxides or other impurities at the interface between cladding layers 33 and within individual cladding layers 33, which could affect the fatigue strength and mechanical properties of the printed part, but the heating device 37 within the high vacuum environment also provides a temperature-raising environment for laser cladding 4D printing, particularly for laser 4D printing of certain shape memory alloys.

[0047] In addition, the embodiment of the present invention also provides a laser cladding 3D / 4D printing system, such as Figure 1 As shown, it specifically includes an industrial computer 1, a laser 3D / 4D printing mechanism, an ultrafast laser shaping mechanism, a holographic camera 17, a pulse generator 18, a stress wave sensor, a spectrometer 14, an X-ray stress detection device and a processing platform for carrying a printed part 27; the laser 3D / 4D printing mechanism emits a first laser to melt the additive manufacturing material to form a cladding layer 33; the ultrafast laser shaping mechanism emits a second laser to shape the cladding layer 33; the holographic camera 17 is electrically connected to the spectrometer 14, and the laser 3D / 4D printing mechanism, the ultrafast laser shaping mechanism, the pulse generator 18, the stress wave sensor, the spectrometer 14, and the X-ray stress detection device are all electrically connected to the industrial computer 1.

[0048] In some embodiments, the laser 3D / 4D printing mechanism includes a laser processing head 22, a printing laser generator 25 and an optical path scanning mechanism 24. The laser processing head 22 contains powder material for additive manufacturing. The laser processing head 22 is located directly above the processing platform. The printing laser generator 25 is electrically connected to the industrial computer 1. The optical path scanning mechanism 24 is located on the emission light path of the printing laser generator 25, and allows the laser emitted by the printing laser generator 25 to be incident on the laser processing head 22.

[0049] Optimally, the laser processing head 22 is connected to a feeding system 26 for adding material to the laser processing head 22 in real time; further optimized, the laser processing head 22 is also connected to a protective gas intake mechanism 23 for introducing an inert protective gas into the laser processing head 22, and the inert protective gas introduced can be but is not limited to argon with a concentration greater than 99.999%; the feeding system 26 and the protective gas intake mechanism 23 are both electrically connected to the industrial computer 1.

[0050] In other embodiments, the ultrafast laser shaping mechanism includes an ultrafast laser 2, and a first reflector 3, a half-wave plate 4, a polarization beam splitter 5, a spatial light modulator 6, a 4F optical information processing assembly, a second reflector 15, and a laser probe 16, which are sequentially arranged along the laser emission optical path of the ultrafast laser 2; the ultrafast laser 2 is electrically connected to the industrial computer 1. The 4F optical information processing assembly includes a first lens 7, a first laser reflector 8, a spatial filter 9, a second laser reflector 10, and a second lens 11, which are sequentially arranged along the laser emission optical path. During operation, the laser emitted by the ultrafast laser 2 is reflected by the first reflector 3 and passes through the half-wave plate 4 and the polarization beam splitter 5 (the angle of the half-wave plate 4 can be rotated to adjust the laser energy), and then enters the spatial light modulator 6. The spatial light modulator 6 is loaded with a hologram and modulates the phase of the light to form a high-speed, short-pulse ultrafast laser beam. The laser beam passes through a 4F optical information processing component. During the processing of this 4F optical information processing component, in order to eliminate the influence of zero-order light on the processing, a spatial filter 9 is placed at the focus of the first lens 7 to block the zero-order light and present the image of the spatial light modulator 6 (the image after Fourier transformation) on the processing plane. The generated ultrafast laser is incident on the laser probe 16 through the second reflector 15 to emit a laser beam that acts on the surface area of the cladding layer 33 on the laser 3D / 4D printed part.

[0051] Specifically, by adjusting the lens spacing in the 4F optical information processing assembly (e.g., first lens F = 500 mm, second lens F = 500 mm), the spot diameter can be continuously adjusted within the range of 20-100 μm. For example, for severe defect areas, a 20 μm spot and a single-point impact with an energy density of 10 J / cm² are used; for general defect areas, a 50 μm spot and a linear scan with an energy density of 6 J / cm² are used.

[0052] In a preferred embodiment, a flip mirror 12 is provided in the optical path between the 4F optical information processing assembly and the second reflector 15, creating a branch optical path that is incident on the spectrometer 14. A third lens 13 is provided between the flip mirror 12 and the spectrometer 14. The flip mirror 12 between the 4F optical information processing assembly and the second reflector 15 is used to direct a portion of the laser light into the spectrometer 14, allowing real-time monitoring of the plasma spectrum during the shaping process and verifying the effectiveness of the zoning treatment (e.g., changes in the intensity of the characteristic spectral lines of the elements in the cladding layer 33 reflect the surface flatness). Optionally, the first lens 7, second lens 11, and third lens 13 can be plano-convex lenses of F500, F500, and F300, respectively.

[0053] In an optional embodiment, the processing platform adopts a five-axis composite linkage processing platform, specifically including a bottom support platform 31, a five-axis linkage rotating platform and a stage 28, wherein the five-axis linkage rotating platform is supported on the bottom support platform 31, and the stage 28 is installed on the five-axis linkage rotating platform; wherein, the five-axis linkage rotating platform uses its horizontal rotating platform 29 and vertical rotating platform 30 to drive the stage 28 to rotate in the horizontal and vertical planes, thereby adjusting the relative position relationship between the print 27 on the stage 28 and the laser processing head 22, the laser probe 16, the holographic camera 17, the pulse generator 18, the stress wave sensor, and the X-ray stress detection device.

[0054] In a preferred embodiment, the laser cladding 3D / 4D printing system of this embodiment further includes a vacuum heating chamber, wherein the laser processing head 22 of the laser 3D / 4D printing mechanism, the laser probe 16 of the ultrafast laser shaping mechanism, the holographic camera 17, the pulse generator 18, the stress wave sensor, the X-ray stress detection device, and the processing platform are all vacuum-sealed and arranged within the vacuum heating chamber. Optionally, a temperature sensor 35 and a pressure sensor 34 are provided within the vacuum heating chamber, and a vacuum pump 36 and a heating device 37 are connected to the vacuum heating chamber. The temperature sensor 35, pressure sensor 34, vacuum pump 36, and heating device 37 are all connected to the industrial computer 1. The temperature sensor 35 and pressure sensor 34 respectively detect the temperature and pressure within the vacuum heating chamber, and based on the detection results, the vacuum pump 36 and heating device 37 control the pressure and temperature within the vacuum heating chamber in real time. The high vacuum environment of the vacuum heating chamber can effectively prevent the presence of oxides or other impurities at the interface between the cladding layers 33 and in a single cladding layer 33, which may affect the fatigue strength and mechanical properties of the printed part. At the same time, the heating device in the high vacuum environment can also provide a 4D printing temperature rise environment for laser cladding 4D printing.

[0055] The above examples are merely illustrative of the present invention and do not limit the scope of protection of the present invention. Any design that is identical or similar to the present invention falls within the scope of protection of the present invention.

Claims

1. A laser cladding 3D / 4D printing method, characterized in that: The steps include: S1. Build a 3D model of the part to be printed based on its parameters, slice the 3D model, and generate a 2D interface diagram for each printed layer. S2, using the first laser to melt the additive manufacturing material of the current layer and form a cladding layer; S3. Micro-shaping the surface of the cladding layer using a second laser. First, the surface roughness and hole defect areas of the cladding layer are micro-shaped by adjusting the process parameters of the second laser. Then, the emission power of the second laser is adjusted to irradiate the surface of the cladding layer with a point heat source to eliminate residual stress in the cladding layer. The process parameters for micro-shaping the surface roughness and hole defect areas of the cladding layer by the second laser are adjusted based on the optical information of the cladding layer captured by the holographic camera and the surface roughness and hole defect information of the cladding layer acquired in real time by the stress wave emitted by the pulse generator. S4. Repeat steps S2-S3 to complete the additive manufacturing process for each layer until a printed part is obtained.

2. The laser cladding 3D / 4D printing method according to claim 1, wherein: A dynamic hologram of the cladding layer surface is obtained using a holographic camera, and the dynamic hologram of the cladding layer surface is analyzed by a spectrometer. The arithmetic mean roughness parameter of the cladding layer surface is calculated. Combined with the stress wave fluctuation signal obtained by the stress wave sensor, a roughness joint evaluation model for dual-modal detection is established, and the comprehensive roughness value of the cladding layer surface is calculated. The surface roughness, hole requirements and corresponding mechanical properties of the cladding layer are judged through the correlation mechanism of detection data and parameter adjustment, as well as the real-time feedback and closed-loop control process to adjust the process parameters of the second laser in real time, completing real-time laser processing correction and ultrafast laser micro-shaping of the defective areas on the surface of the cladding layer.

3. The laser cladding 3D / 4D printing method according to claim 1, wherein: In step S3, the emission power of the second laser for point heat source irradiation on the surface of the cladding layer is adjusted according to the residual stress information on the surface of the cladding layer obtained in real time by the X-ray stress detection device.

4. The laser cladding 3D / 4D printing method according to claim 3, wherein: The X-ray stress detection device includes an X-ray generator, an X-ray detector and an X-ray measurement recorder. The X-ray generator emits X-rays to the surface of the cladding layer, the X-ray detector detects changes in the position of X-ray diffraction peaks in the surface area of the cladding layer, and the X-ray measurement recorder measures and records the diffraction angle in real time. The real-time diffraction angle data is converted and processed by an industrial computer to obtain residual stress information on the surface of the cladding layer.

5. The laser cladding 3D / 4D printing method according to claim 1, wherein: Steps S2, S3, and S4 are all performed in a vacuum heating chamber, and the pressure and temperature inside the vacuum heating chamber are controlled in real time by a vacuum pumping device and a heating device.

6. A laser cladding 3D / 4D printing system, characterized by: Used in the laser cladding 3D / 4D printing method according to any one of claims 1 to 5, comprising an industrial computer, a laser 3D / 4D printing mechanism, an ultrafast laser shaping mechanism, a holographic camera, a pulse generator, a stress wave sensor, a spectrometer, an X-ray stress detection device, and a processing platform for carrying the printed part; The laser 3D / 4D printing mechanism emits a first laser to melt the additive manufacturing material to form a cladding layer; the ultrafast laser shaping mechanism emits a second laser to shape the cladding layer; the holographic camera is electrically connected to the spectrometer, and the laser 3D / 4D printing mechanism, ultrafast laser shaping mechanism, pulse generator, stress wave sensor, spectrometer, and X-ray stress detection device are all electrically connected to the industrial control computer.

7. The laser cladding 3D / 4D printing system according to claim 6, wherein: The ultrafast laser shaping mechanism includes an ultrafast laser, and a first reflector, a half-wave plate, a polarization beam splitter, a spatial light modulator, a 4F optical information processing component, a second reflector and a laser probe arranged in sequence along the laser emission optical path of the ultrafast laser.

8. The laser cladding 3D / 4D printing system according to claim 7, wherein: A flip mirror is provided on the optical path between the 4F optical information processing component and the second reflector, so that a branch optical path is generated on the optical path that can be incident into the spectrometer.

9. The laser cladding 3D / 4D printing system according to claim 6, wherein: It also includes a vacuum heating chamber, in which the laser processing head of the laser 3D / 4D printing mechanism, the laser probe of the ultrafast laser shaping mechanism, the holographic camera, the pulse generator, the stress wave sensor, the X-ray stress detection device and the processing platform are all vacuum-sealed and arranged.

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