Laser metal 3D printing device and closed-loop control system and method thereof

Abstract

The application discloses a kind of laser metal 3D printing devices, it includes a connecting frame, connecting frame top is provided with a support cover, support cover is provided with collimator, parallel cylindrical light beam projected by collimator is projected on optical lens system on support cover, optical lens system includes a light splitting focusing integrated mirror and a ring focusing mirror, light splitting focusing integrated mirror includes a convex focusing mirror in middle and a conical surface reflection beamsplitter.Part of parallel cylindrical light beam is focused by convex focusing mirror and forms circular solid light spot below;Another part is divided into a circle of radial uniform distribution by conical surface reflection beamsplitter and is injected into ring focusing mirror, and forms a circle of ring focusing light spot below;The application can solve the problem of weak energy of single gaussian spot light periphery, improve the energy distribution uniformity, effectively improve the full metallurgical combination between cladding layer edge and base material or layer piece, reduce pore, improve mechanical properties.

Description

Technical Field

[0001] This invention belongs to the field of laser metal additive manufacturing, and more specifically, relates to a laser metal 3D printing device. Background Technology

[0002] Laser metal 3D printing equipment belongs to laser metal additive manufacturing, a new surface modification and forming technology. It is a method that adds cladding material to the surface of a substrate and uses a high-energy-density laser beam to fuse it together with a thin layer on the substrate surface. The result is the formation of a metallurgically bonded cladding layer or a three-dimensional shaped part on the substrate surface.

[0003] Features of laser metal 3D printing: The cladding layer has low dilution but strong adhesion, forming a metallurgical bond with the substrate. This significantly improves the wear resistance, corrosion resistance, heat resistance, oxidation resistance, and electrical properties of the substrate material, achieving surface modification or repair. It meets specific surface performance requirements while saving significant material costs. Laser metal 3D printing produces parts with high shape accuracy and mechanical properties. Compared to traditional surface treatment technologies such as welding, thermal spraying, and electroplating, it offers numerous advantages, including a wide range of applicable material systems, controllable cladding layer dilution rate, metallurgical bonding between the cladding layer and the substrate, minimal substrate thermal deformation, and ease of automation.

[0004] Currently, laser metal 3D printing is mainly applied in three areas: 1. Surface modification of materials, such as gas turbine blades, rolls, and gears. 2. Surface repair of products, such as rotors and molds. 3. Laser additive manufacturing, which uses synchronous powder or filament feeding to perform layer-by-layer laser cladding to obtain parts with three-dimensional structures. Since the 1980s, laser cladding technology has received widespread attention both domestically and internationally and has been applied in many industrial fields.

[0005] The inventors of this case have long been researching the field of laser metal 3D printing. During the application of related products and equipment, they discovered some situations that affect the surface quality and performance of the final metal 3D printed / clad parts, or the short service life of the products and equipment. For example, when performing laser metal 3D printing or cladding, if the arrangement of the laser beam and the powder delivered to the molten pool is unreasonable, and the powder divergence effect cannot guarantee that 100% of the powder is delivered to the molten pool, some powder will fly away from the molten pool area. In addition, the energy of the laser beam is distributed with low energy at both ends and high energy at the center, and the energy at the edge of the beam is insufficient, which cannot fully clad the powder. Multiple factors exacerbate the low powder utilization rate, high surface roughness of the clad layer or the formed part, and even residual powder can seriously pollute the environment and cause health problems to the operators. Furthermore, the metallurgical bonding between the powder melt and the substrate or between layers is insufficient, resulting in poor mechanical properties of the clad layer or the three-dimensional formed part.

[0006] Regarding the problems in the prior art, please refer to an invention patent with publication number CN111378966A, entitled "Ultra-high-speed laser cladding manufacturing method for bimetallic oil sleeves". In the technical solution disclosed in this patent, the annular powder flow surrounding the central Gaussian beam is melted by the central Gaussian beam. Due to the powder flow emission effect, only a portion of the powder is melted by the central Gaussian beam to form a cladding layer. Most of the remaining powder will detach from the molten pool area. Some of it adheres to the surface of the cladding layer due to insufficient energy from the beam, while others are directly removed from the temperature zone by the reaction force between the airflow and the substrate, becoming waste powder. This results in extremely low powder utilization. At the same time, the unmelted powder adheres to the surface of the formed part, causing high roughness. Due to the high energy at the center and low energy at the ends of the Gaussian beam, the powder in the area around the beam spot cannot fully metallurgically bond with the substrate or layer, easily causing porosity and reduced mechanical properties.

[0007] To address the aforementioned technical problems, an outer ring-shaped laser beam cladding aperture can be added to enclose the annular powder flow, thereby solving the problem that the powder in the area surrounding the laser spot cannot fully metallurgically bond with the substrate or the layers of the three-dimensional molded part. Relevant technical solutions can be found in the invention patent with publication number CN 116240540 A, entitled "A Composite Laser Cladding Optical Path", and the invention patent with publication number CN 112159978 A, entitled "A Center-Feeding Cladding Head with Preheating and Tempering Capability".

[0008] Combining the technical solutions disclosed in any of the above invention patents with existing cladding devices can realize the "light-powder-light" cladding principle. However, the optical path system in this technical solution is complex and costly. In particular, the invention patent with publication number CN 112159978A uses up to eight lenses to achieve a single beam. The large number of lens groups results in low effective utilization of laser energy and high cost. The powder channel is directly irradiated and blocked by the beam, further reducing the effective utilization of the beam and increasing energy consumption, which is not conducive to its widespread use. Summary of the Invention

[0009] To address the problems existing in the prior art, this invention aims to provide a laser metal 3D printing device that can improve powder utilization, enable powder to melt fully, reduce powder adhesion effect, increase the mechanical properties of the cladding layer and improve surface roughness, reduce environmental pollution, and reduce the high cost and operator health problems caused by powder waste in metal 3D printing.

[0010] To achieve the above-mentioned technical objectives and effects, the present invention is implemented through the following technical solution:

[0011] A laser metal 3D printing device includes a connecting frame with a support cover on top. The support cover has a collimator for connecting an incident laser beam. The parallel cylindrical beam projected by the collimator is projected onto an optical lens system on the support cover. The optical lens system includes a beam-splitting and focusing integrated mirror located directly below the parallel cylindrical beam beam and an annular focusing mirror located on the reflection path of the beam-splitting and focusing integrated mirror. The beam-splitting and focusing integrated mirror includes a convex lens in the middle and a conical reflective beam splitter integrally formed with the convex lens.

[0012] A portion of the parallel cylindrical beam is focused by the convex lens to form a solid circular spot below; another portion of the parallel cylindrical beam is split into a ring of radially uniform beams by the conical reflector beam splitter and enters the annular lens, where it is focused to form an annular focused spot below; the annular focused spot surrounds the solid circular spot with a gap, the gap containing cladding material.

[0013] Below the connecting frame, there is also a conical air guide hood with both ends extending through it. The bottom end of the conical air guide hood is fixed to the connecting frame, and the tip of the conical air guide hood is away from the connecting frame. An air inlet is provided on the conical air guide hood, and the air inlet is connected to an inert gas source through an air nozzle. The inert gas source enters the conical air guide hood through the air nozzle and is finally ejected from the tip of the conical air guide hood.

[0014] Another objective of this invention is to provide a closed-loop control system for a laser metal 3D printing device, comprising an inert gas flow meter, a powder flow distribution image meter, a spot size distribution image meter, and a data center processor. The data acquired by each of the inert gas flow meter, the powder flow distribution image meter, and the spot size distribution image meter is transmitted to the data center processor. The data center processor is connected to an inert gas flow meter, a spot power controller, and a powder spraying rate controller. The calculated control parameters in the data center processor are transmitted to the inert gas flow meter, the spot power controller, and the powder spraying rate controller. This closed-loop control system can ensure that the powder flow remains between the central solid spot and the peripheral annular spot, and that the energy distribution is more uniform, thus solving the technical problems existing in the prior art.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0016] The laser metal 3D printing device of the present invention effectively solves the problems existing in the prior art by adopting the "light-powder-light" + "annular airflow channel" technical solution, specifically:

[0017] 1. In terms of structure

[0018] The optical lens system of the present invention has a small number of lenses and a simple structure, which makes the system more stable, the manufacturing cost lower, and the device / product easier to promote and use.

[0019] 2. In terms of implementation principle

[0020] In this invention, the central area of ​​the circular solid light spot and the peripheral annular focused light spot envelop the central region of the annular powder. The annular airflow channel further restricts the possibility of the powder being sprayed out of the outer area of ​​the annular light, thereby allowing most of the powder to converge in the area irradiated by the annular light and the solid light, improving the powder utilization rate. At the same time, it allows most of the powder to be fully melted, reducing the powder adhesion effect and improving the surface roughness of the cladding.

[0021] Furthermore, by adding a ring beam around the solid light spot, the problem of weak energy around the Gaussian light is solved, the uniformity of energy distribution is improved, the metallurgical bonding between the edge of the cladding layer and the substrate or between layers of the three-dimensional part is effectively improved, porosity is reduced, and mechanical properties are improved.

[0022] In addition, the added ring light on the periphery can also serve as a preheating and tempering agent, further improving the mechanical properties and forming quality of the cladding layer or three-dimensional formed parts.

[0023] 3. The present invention can also add a closed-loop control system, which can effectively reduce process debugging time and improve laser cladding efficiency, surface quality and mechanical properties through intelligent control.

[0024] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it according to the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Specific embodiments of the present invention are given in detail below with reference to the accompanying drawings. Attached Figure Description

[0025] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings:

[0026] Figure 1 This is a schematic diagram of the structure of the laser metal 3D printing device of the present invention.

[0027] Figure 2 is a cross-sectional view of the laser metal 3D printing device of the present invention; wherein, Figure 2(a) shows the direction of the beam, and Figure 2(b) is a partial enlarged schematic diagram of Figure 2(a), and the arrow pattern in the figure represents the airflow.

[0028] Figure 3 This is a schematic diagram of the connecting frame in the device of the present invention.

[0029] Figure 4 This is a schematic diagram showing the assembly relationship between the connecting frame and the optical lens system in the device of the present invention.

[0030] Figure 5 This is a schematic diagram of the beam-splitting and focusing integrated mirror in the device of the present invention.

[0031] Figure 6 This is a schematic diagram of the structure of the annular focusing lens in the device of the present invention.

[0032] Figure 7 This is a schematic diagram of the protective mirror in the device of the present invention.

[0033] Figure 8 This is a schematic diagram of the assembly relationship of the powder conveying channel in the device of the present invention.

[0034] Figure 9 This is a schematic diagram of the air guide sleeve in the device of the present invention; the arrows in the figure represent airflow.

[0035] Figure 10 is a schematic diagram of the "light-powder-light" effect of the present invention; wherein, Figure 10(a) is a schematic diagram of the orthographic projection of "light-powder-light", and Figure 10(b) is a schematic diagram of the projection relationship of "light-powder-light".

[0036] Figure 11 is a schematic diagram of the closed-loop control system framework of a laser metal 3D printing device according to the present invention; wherein, Figure 11(a) is a schematic diagram of the architecture of the closed-loop control system, and Figure 11(b) shows the positional relationship of each collector.

[0037] Figure 12 This is a schematic flowchart of a closed-loop control method for a laser metal 3D printing device according to the present invention. Detailed Implementation

[0038] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0039] It should be noted that all directional indicators (such as up, down, left, right, front, back, upper end, lower end, top, bottom, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly. Example 1:

[0040] See Figures 1-9As shown, a laser metal 3D printing device includes a connecting frame 1, a support cover 2 above the connecting frame 1, a collimator 3 for connecting an incident laser on the support cover 2, a parallel cylindrical beam projected by the collimator 3 onto an optical lens system on the support cover 2, the optical lens system including a beam splitting and focusing integrated mirror 4 located directly below the parallel cylindrical beam and an annular focusing mirror 5 located on the reflection path of the beam splitting and focusing integrated mirror 4, the beam splitting and focusing integrated mirror 4 including a convex lens focusing mirror 401 located in the middle and a conical reflective beam splitter 402 integrally formed with the convex lens focusing mirror 401;

[0041] A portion of the parallel cylindrical beam is focused by the convex lens 401 to form a solid circular spot 20 below; another portion of the parallel cylindrical beam is split into a ring of radially uniform beams by the conical reflector 402 and enters the annular lens 5, and is focused by the annular lens 5 to form an annular focused spot 10 below; the annular focused spot 10 surrounds the solid circular spot 20 with a gap, as shown in Figure 10(a).

[0042] Furthermore, such as Figure 3 As shown, the connecting frame 1 includes a connecting part 101, the outer ring of the connecting part 101 is a ring focusing lens fixing part 102, the middle of the connecting part 101 is a beam splitting focusing integrated lens fixing part 103, the center of the beam splitting focusing integrated lens fixing part 103 is provided with a direct light path transmission hole 104, and the outer ring of the convex focusing lens fixing part 103 is provided with a reflected light path transmission hole 105.

[0043] The beam-splitting and focusing integrated mirror 4 is fixed on the beam-splitting and focusing integrated mirror fixing part, and the annular focusing mirror 5 is fixed on the annular focusing mirror fixing part 102;

[0044] The projection beam of the circular solid light spot 20 is emitted from the direct light path aperture 104, and the projection beam of the annular focused light spot 10 is emitted from the reflected light path aperture 105.

[0045] Furthermore, the light-transmitting aperture 105 of the reflected light path is provided with a... Figure 7 The protective mirror 6 shown.

[0046] Furthermore, such as Figure 3As shown, the connecting part 101 has a plurality of feeding tube through holes 106, which are located between the direct light path through hole 104 and the reflected light path through hole 105 and are evenly arranged around the direct light path through hole 104; a feeding tube 7 is fixed in the feeding tube through hole 106, and the upper end of the feeding tube 7 is connected to a feeding tube fixing joint 701, which is fixed on the support cover 2; the lower end of the feeding tube 7 is connected to a feeding cavity 8.

[0047] Furthermore, such as Figure 8 As shown, the feeding cavity 8 is fixed below the connecting frame 1 by a connecting part. The feeding cavity 8 is a conical structure with both ends through it. The bottom end of the conical structure is connected to the connecting part, and the tip of the conical structure is away from the connecting part. The projection beam of the circular solid light spot 20 is projected from the tip of the conical structure through the hollow part of the conical structure.

[0048] The feeding cavity 8 has a hollow double-layer structure. The upper end of the cavity wall is closed, which is the bottom end of the conical structure, and the lower end of the cavity wall is open, which is the top end of the conical structure.

[0049] The lower end of the feeding tube 7 is connected to the cavity wall of the feeding chamber 8 through an interface. The cladding material fed through the feeding tube 7 is ejected from the tip of the conical structure. The ejected cladding material 30 surrounds the circular solid light spot 20. Furthermore, the powder conveying channel formed by the feeding chamber 8 and the feeding tube 7 is located between the reflected light path of the annular focusing lens 5 and the direct light path of the convex focusing lens 401. The annular focusing light spot 10 envelops the cladding material 30 ejected from the tip of the conical structure, thus forming a "light-powder-light" structural layout, as shown in Figure 10(b).

[0050] Further, see Figure 9 As shown, a conical air guide shroud 9 with both ends extending through it is also provided below the connecting frame 1. The bottom end of the conical air guide shroud 9 is fixed to the connecting frame 1, and the tip of the conical air guide shroud 9 is away from the connecting frame 1. An air inlet is provided on the conical air guide shroud 9, and the air inlet is connected to an inert gas source through an air nozzle 901. The inert gas source enters the conical air guide shroud 9 through the air nozzle 901 and is finally ejected from the tip of the conical air guide shroud 9. Figure 9 As shown by the arrow pattern, inert gas is delivered into the gas guide shroud 9 through the gas nozzle 901, and then into the molten pool area through the annular inner cavity. The position of the gas guide shroud 9 is between the annular focusing spot 10 and the internal annular powder conveying channel (i.e., the gap).

[0051] The advantages of adopting the "light-powder-light" structural layout are as follows: The central Gaussian solid spot (i.e., the circular solid spot 20) has the energy characteristic of high energy in the central area and weak energy in the periphery. The powder (i.e., the cladding material 30) is transported along the annular cavity to the central Gaussian solid spot. The powder is sprayed into the spot area in a divergent manner. Due to the high energy of the central spot, the powder sprayed into the central area melts quickly to form a cladding layer. However, some powder is sprayed into the edge area of ​​the central solid spot. Due to the weak energy, the powder cannot melt fully, which easily forms pores and powder adheres to the surface of the cladding layer, resulting in reduced mechanical properties and poor surface roughness of the cladding layer. Therefore, annular light (i.e., annular focusing spot 10) is arranged around the powder to wrap the powder again. Through the combined action of the central solid spot and the surrounding annular light, the powder sprayed in the annular cavity is wrapped by two independent light sources inside and outside, which solves the problem of laser cladding defects caused by the weak energy around the central light source, which cannot fully melt the powder. Meanwhile, inert gas is injected into the outer ring light path channel. Through the action of airflow, the dispersed powder is further confined between the two light spots, preventing the dispersed powder from escaping outside the ring light and reducing the powder utilization rate. At the same time, the residual powder remains on the surface of the cladding layer, affecting the roughness, improving the metallurgical bonding between the edge of the cladding layer and the substrate, and improving the connection strength. Example 2:

[0052] Referring to Figures 11(a) and 11(b), this embodiment discloses a closed-loop control system for a laser metal 3D printing device, which includes an inert gas flow acquisition device 100, a powder flow distribution image acquisition device 200, a spot size distribution image acquisition device 300, and a data center processor 400. The data acquired by the inert gas flow acquisition device 100, the powder flow distribution image acquisition device 200, and the spot size distribution image acquisition device 300 are transmitted to the data center processor 400. The data center processor 400 is connected to an inert gas flow meter 500, a spot power controller 600, and a powder spraying rate controller 700. The calculated control parameters in the data center processor 400 are transmitted to the inert gas flow meter 500, the spot power controller 600, and the powder spraying rate controller 700. The control principle of the closed-loop control system in this embodiment is as follows:

[0053] Inert gas flow meter 500: mainly controls the adjustment of inert gas flow rate. It can determine whether the powder can be concentrated inside the annular light spot based on the current flow data collected by the inert gas flow acquisition instrument 100 located below the feeding chamber 8 (whether the powder is concentrated inside the annular light spot is achieved by comparing the powder flow distribution image acquisition instrument 200 and the light spot size distribution image acquisition instrument 300). If the powder does not reach the expected target, the data center processor 400 will respond based on the feedback result and increase the flow rate of the inert gas flow meter 500, so that the sprayed inert gas flow acts on the sprayed powder end, and through the intelligent closed-loop control system, it is eventually concentrated inside the annular light spot.

[0054] Inert gas flow acquisition instrument 100: Real-time monitoring of the flow rate of powder ejected from the feeding chamber 8, and feeding the data back to the data center processor 400. The data center processor 400 analyzes and compares the data to determine the flow rate of the inert gas flow meter 500, thereby achieving closed-loop flow control.

[0055] Powder flow distribution image acquisition device 200 and spot size distribution image acquisition device 300: Powder flow distribution image acquisition device 200 mainly acquires the distribution of powder flow, and spot size distribution image acquisition device 300 mainly acquires the size and position of the spot. Both are transmitted to the data center processor 400 through data comparison to detect whether the powder flow is inside the annular spot. If the powder is not inside the annular spot, the laser beam power is increased by adjusting the spot power controller 600 to increase the energy of the annular spot, thereby covering the powder. Alternatively, the laser power controller 600 can be adjusted to control the laser power, the powder spraying rate controller 700 can be adjusted to control the powder speed to reduce powder dispersion, and the inert gas flow meter 500 can be adjusted to increase the inert gas flow rate. Together, these measures ensure that the sprayed powder is always inside the annular spot, thereby achieving closed-loop control.

[0056] See Figure 12 As shown, the control method of the closed-loop control system in this embodiment includes the following steps:

[0057] 1) Starting device

[0058] These include the activation of the laser emitting mechanism, the activation of the powder feeding mechanism, and the activation of the inert gas mechanism, respectively.

[0059] 2) System self-test

[0060] The closed-loop control system is activated, and the inert gas flow acquisition instrument 100, the powder flow distribution image acquisition instrument 200, and the spot size distribution image acquisition instrument 300 located above the laser cladding zone collect data.

[0061] 4) Data Analysis

[0062] The data center processor 400 analyzes and processes the data collected by each acquisition device and issues control commands according to the system's preset pairing requirements.

[0063] 5) Adaptive adjustment

[0064] The inert gas flow meter 500, the spot power controller 600, and the powder spraying rate controller 700 adaptively adjust according to the control commands sent by the data center processor 400.

[0065] 6) Carry out laser cladding work

[0066] When the adaptive adjustment is performed until the powder flow distribution image acquisition instrument 200 and the spot size distribution image acquisition instrument 300 detect that the relationship between light and powder reaches the system's preset "light-powder-light" cladding layout, laser cladding is carried out.

[0067] When the adaptive adjustment is performed until the powder flow distribution image acquisition instrument 200 and the spot size distribution image acquisition instrument 300 detect that the relationship between light and powder does not reach the system's preset "light-powder-light" cladding layout, step 5 is repeated.

[0068] The control method of this embodiment can always keep the powder sprayed into the molten pool within the annular light spot, preventing the powder from escaping the dual light spot irradiation area and failing to be fully melted, thereby effectively improving powder utilization, energy utilization, surface roughness of the cladding layer, and cladding forming efficiency.

[0069] Compared to having no intelligent control solution:

[0070] Without intelligent control methods, countless experiments are required to verify the powder rate, inert gas flow rate, and power of the laser beam ring beam and the central solid spot. Only by constantly adjusting these parameters can the powder be kept inside the spot. The operation efficiency is extremely low. Due to the large error of manual operation and the lack of a closed-loop control mechanism, the parameters of the cladding process are unstable, and the quality and mechanical properties between the cladding layer or the formed part layer are also unstable.

[0071] Therefore, by adding the control method of this embodiment, the quality, efficiency and mechanical properties of laser cladding forming can be effectively improved.

[0072] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A laser metal 3D printing device, comprising a connecting frame (1), a support cover (2) disposed above the connecting frame (1), a collimator (3) for connecting an incident laser being disposed on the support cover (2), wherein a parallel cylindrical beam projected by the collimator (3) is projected onto an optical lens system on the support cover (2), characterized in that: The optical lens system includes a beam-splitting and focusing integrated mirror (4) located directly below the parallel cylindrical beam and an annular focusing mirror (5) located on the reflection path of the beam-splitting and focusing integrated mirror (4). The beam-splitting and focusing integrated mirror (4) includes a convex lens focusing mirror (401) located in the middle and a conical reflective beam splitter (402) integrally formed with the convex lens focusing mirror (401). The connecting frame (1) includes a connecting part (101), the outer ring of the connecting part (101) is a ring focusing lens fixing part (102), the middle of the connecting part (101) is a beam splitting focusing integrated lens fixing part (103), a direct light path transmission hole (104) is opened at the center of the beam splitting focusing integrated lens fixing part (103), and a reflected light path transmission hole (105) is opened on the outer ring of the beam splitting focusing integrated lens fixing part (103). The beam-splitting and focusing integrated lens (4) is fixed on the beam-splitting and focusing integrated lens fixing part, and the annular focusing lens (5) is fixed on the annular focusing lens fixing part (102); A protective mirror (6) is provided on the light-transmitting hole (105) of the reflected light path; The connecting part (101) is provided with a plurality of feeding pipe through holes (106), which are located between the direct light path through hole (104) and the reflected light path through hole (105) and are evenly arranged around the direct light path through hole (104). A feeding pipe (7) is fixed inside the feeding pipe through hole (106). The upper end of the feeding pipe (7) is connected to a feeding pipe fixing joint (701), which is fixed on the support cover (2). The lower end of the feeding pipe (7) is connected to a feeding cavity (8). The feeding cavity (8) is fixed below the connecting frame (1) by a connecting part. The feeding cavity (8) is a conical structure with both ends through. The bottom end of the conical structure is connected to the connecting part, and the tip of the conical structure is away from the connecting part. The feeding cavity (8) has a hollow double-layer structure. The upper end of the cavity wall is closed and forms the bottom end of the conical structure, while the lower end of the cavity wall is open and forms the top end of the conical structure. The lower end of the feeding pipe (7) is connected to the cavity wall of the feeding cavity (8) through an interface; The powder conveying channel formed by the feeding cavity (8) and the feeding tube (7) is located between the reflected light path of the annular focusing lens (5) and the direct light path of the convex focusing lens (401). Below the connecting frame (1), there is also a conical air guide hood (9) with both ends through. The bottom end of the conical air guide hood (9) is fixed on the connecting frame (1), and the tip of the conical air guide hood (9) is far away from the connecting frame (1). An air inlet is provided on the conical air guide shroud (9), and the air inlet is connected to an inert gas source through an air nozzle (901).

2. The closed-loop control system of the laser metal 3D printing device according to claim 1, characterized in that: It includes an inert gas flow acquisition instrument (100), a powder flow distribution image acquisition instrument (200), a spot size distribution image acquisition instrument (300), and a data center processor (400). The data collected by the inert gas flow acquisition instrument (100), the powder flow distribution image acquisition instrument (200), and the spot size distribution image acquisition instrument (300) are transmitted to the data center processor (400). The data center processor (400) is connected to an inert gas flow meter (500), a spot power controller (600), and a powder spraying rate controller (700). The calculated control parameters in the data center processor (400) are transmitted to the inert gas flow meter (500), the spot power controller (600), and the powder spraying rate controller (700).

3. A control method for a closed-loop control system of a laser metal 3D printing device as described in claim 2, characterized in that, Includes the following steps: 1) Starting device These include the activation of the laser emitting mechanism, the activation of the powder feeding mechanism, and the activation of the inert gas mechanism, respectively. 2) System self-test The closed-loop control system is activated, and the inert gas flow acquisition instrument (100), powder flow distribution image acquisition instrument (200), and spot size distribution image acquisition instrument (300) located above the laser cladding zone collect data. 4) Data Analysis The data center processor (400) analyzes and processes the data collected by each acquisition device and issues control commands according to the system's preset pairing requirements; 5) Adaptive adjustment The inert gas flow meter (500), the spot power controller (600), and the powder spraying rate controller (700) adaptively adjust according to the control instructions sent by the data center processor (400); 6) Carry out laser cladding work When the adaptive adjustment of the powder flow distribution image acquisition instrument (200) and the spot size distribution image acquisition instrument (300) detects that the relationship between light and powder reaches the preset "light-powder-light" cladding layout, laser cladding is performed.

4. The control method according to claim 3, characterized in that: When the adaptive adjustment to the powder flow distribution image acquisition instrument (200) and the spot size distribution image acquisition instrument (300) detects that the relationship between light and powder does not reach the system's preset "light-powder-light" cladding layout, step 5 is repeated.

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