Variable-speed powder spreading device for selective laser melting forming and using method of variable-speed powder spreading device

Abstract

The invention discloses a variable-speed powder spreading device for selective laser melting forming and a using method of the variable-speed powder spreading device. Dynamic powder spreading control is achieved through double mechanisms of section recognition and resistance feedback. The device is composed of a scraper frame, a three-dimensional white light recognizer, an inclined powder feeding port and a distributed resistance sensor. The scraper frame executes intelligent speed change through a gear transmission mechanism, powder is laid at a high speed in a non-forming area, and powder is laid at a low speed in a formed critical structure (such as less than or equal to 45 degrees and thin-wall easily-deformed parts). Single-bin single-direction powder feeding is innovatively adopted, uniform powder distribution is achieved through a 100-mesh screen of a-30-degree inclined groove, the invalid stroke of a powder supply bin is omitted, and the impurity pollution rate is reduced. The recognizer integrates a self-cleaning function and scans microcracks of a formed surface in real time, the resistance sensor dynamically feeds back contact pressure, and the control system matches optimal parameters through a fuzzy PID algorithm.

Description

Technical Field

[0001] The present invention relates to the field of 3D printing technology, and specifically to a variable-speed powder spreading method and device based on cross-section recognition and resistance feedback during the forming process of Selective Laser Melting (SLM), which is applicable to the additive manufacturing of high-precision complex structure parts such as aerospace and medical devices. Background Art

[0002] The selective laser melting technology realizes part forming by spreading powder layer by layer and laser melting metal powder, and has the advantages of high forming precision, high material utilization rate, and manufacturability of complex structures, and is widely used in the manufacturing of key components such as aeroengine blades and aerospace structural parts. In the SLM process, the powder spreading quality directly affects the forming precision and success rate, and the powder spreading process is completed by the movement of the doctor blade. The traditional process uses uniform-speed powder spreading, and there are the following technical bottlenecks: Defects of uniform-speed powder spreading: The doctor blade of existing SLM equipment usually moves at a constant speed. When the doctor blade passes through the formed critical inclined structure (such as an inclined surface with an angle ≤ 45°), due to the large friction force when the doctor blade moves at a constant speed at this time, the formed layer is easily deformed, warped or even peeled off by the friction and extrusion of the doctor blade, especially in vulnerable structure areas such as thin walls and overhangs, and the printing failure rate is relatively high.

[0003] Lack of intelligent feedback mechanism: Traditional powder spreading devices are not integrated with cross-section recognition and resistance monitoring functions, and cannot perceive the characteristics of the printing cross-section in real time (such as whether there is warping or lack of powder) and the contact resistance between the doctor blade and the formed surface, resulting in the inability to adaptively adjust the powder spreading speed, and it is difficult to balance efficiency and quality.

[0004] Redundancy of powder supply stroke: Some existing equipment adopts a double-chamber (forming chamber and powder supply chamber) design, and the doctor blade needs to travel back and forth between the two chambers to complete powder scraping, which increases the ineffective stroke and time cost.

[0005] Although there are attempts in the prior art to improve the powder spreading quality by adjusting the doctor blade angle, optimizing the powder fluidity, etc., the core problem of "dynamically identifying cross-section characteristics and adaptively adjusting the powder spreading speed" has not been solved. Therefore, there is an urgent need for a method and device that can perceive the printing cross-section state in real time and realize variable-speed powder spreading based on resistance feedback to improve the printing success rate and efficiency of complex structure parts. Summary of the Invention

[0006] The present invention aims to overcome the above-mentioned disadvantages of the prior art and provides a variable-speed powder spreading device for selective laser melting forming and its usage method.

[0007] The technical solution adopted by the present invention is as follows: A variable-speed powder spreading method for selective laser melting forming, comprising the following steps: (1) Three-dimensionally recognize the formed cross-section on the printing platform through a cross-section recognizer installed at the bottom of the doctor blade holder to obtain the geometric features, grayscale, and brightness information of the cross-section; (2) During the movement of the doctor blade holder, the powder feeding port conveys powder to the printing area, and at the same time, the resistance sensor real-time collects the contact resistance between the doctor blade and the formed surface; (3) The control system adjusts the rotation speed of the drive motor to drive the variable-speed powder spreading of the doctor blade holder according to the geometric features, grayscale and brightness information, and the contact resistance: when a formed cross-section is recognized or the resistance value is greater than or equal to the preset threshold, control the doctor blade holder to spread powder at a low speed; when an unformed cross-section is recognized or the resistance value is less than the preset threshold, control the doctor blade holder to spread powder at a high speed.

[0008] Further, the cross-section recognizer includes 2 miniature white light interference induction cameras, which scan the formed cross-section before powder spreading, identify the warped and powder-deficient areas, and feed back the recognition results to the control system.

[0009] Further, the powder feeding port only opens to feed powder when the doctor blade holder moves forward. The powder feeding trough slopes downward at an angle of -30° to let the powder fall, and the powder is evenly distributed through a 100-mesh sieve; when the doctor blade holder stops or moves backward, the powder feeding port closes to stop powder supply.

[0010] Further, a variable-speed powder spreading device for selective laser melting forming, characterized by comprising: A doctor blade holder that moves horizontally through a gear transmission mechanism composed of two guide rails and gears; A cross-section recognizer, installed at the front end of the bottom of the doctor blade holder, includes 2 miniature white light interference induction cameras with self-cleaning functions, and is used for three-dimensional recognition of the printing cross-section; A powder feeding port, located in the middle of the bottom of the doctor blade holder, consists of an inclined powder feeding trough and a lower sieve, and is connected to the powder bin through a powder pipe inside the doctor blade holder; A doctor blade fixing holder, located at the rear end of the bottom of the doctor blade holder, installs the doctor blade on one side through 5 evenly distributed screws, and integrates 4 resistance sensors closely attached to the doctor blade on the other side. The resistance sensors are electrically connected to the control system.

[0011] Further, the gear transmission mechanism is driven by a servo motor, and the gear meshes with the rack on the guide rail.

[0012] Further, the self-cleaning device of the cross-section recognizer includes a miniature air pump and a flexible brush. When the grayscale value deviation on the surface of the camera exceeds 5%, the cleaning program is automatically started.

[0013] Further, the powder feeding trough is large at the top and small at the bottom, the width of the powder outlet port is 10 mm, and the mesh number of the sieve is 100 meshes, ensuring that the uniformity error of the powder falling is ≤5%.

[0014] Furthermore, the resistance sensor is a strain sensor, evenly distributed on the side of the blade fixing bracket, with a sampling frequency ≥ 100 Hz, and it monitors the contact pressure between the blade and the formed surface in real time.

[0015] Furthermore, the control system is integrated into the blade holder or the main control unit of the equipment. It receives the three-dimensional data from the cross-section identifier and the pressure signal from the resistance sensor, and dynamically adjusts the motor speed through an algorithm.

[0016] Furthermore, the cross-section identifier, powder feeding port, and blade fixing bracket at the bottom of the blade holder are linearly arranged, with a spacing of 20 - 50 mm, ensuring the timing coordination of the identification, powder feeding, and powder scraping actions.

[0017] In summary, due to the adoption of the above technical solutions, the beneficial effects of the present invention are as follows: Precise powder control and even powder spreading: The powder feeding port is equipped with a -30° inclined powder feeding trough and a 100-mesh sieve. The former guides the powder to flow smoothly downward, and the latter screens and disperses the powder, realizing uniform distribution of the powder in the printing area. This design reduces the problem of uneven powder spreading, improves the powder spreading accuracy and consistency, and can better meet the powder spreading requirements of complex cross-section areas than traditional vertical powder falling, providing a reliable powder supply for high-quality printing. Real-time monitoring and stable feedback: The cross-section identifier has three-dimensional identification and self-cleaning functions. It can collect geometric, grayscale, and brightness information of the printing cross-section in real time, and automatically cleans when the grayscale deviation on the surface of the camera exceeds 5%, ensuring the accuracy and stability of the identification data. The strain resistance sensor has a sampling frequency ≥ 100 Hz, monitors the contact pressure between the blade and the formed surface in real time and feeds back the data. The control system dynamically adjusts the moving speed of the blade holder and the powder feeding amount accordingly, ensuring the stable and reliable powder spreading process, and improving the intelligent level and operation efficiency of the equipment. High-precision transmission and precise movement: The gear transmission mechanism is driven by a servo motor, and the gear meshes with the guide rail and rack. The transmission accuracy ≤ 0.05 mm, and the speed change range is 0.1 - 100 mm / s. This mechanism ensures precise control of the position and speed when the blade holder moves, enables variable-speed powder spreading to be executed according to the preset parameters, provides key mechanical support for the high-quality printing of complex structure parts, ensures the consistency of the powder spreading quality of each layer, and improves the overall printing quality and performance of the parts. Description of the Drawings

[0018] Figure 1 It is a schematic structural diagram of a variable-speed powder spreading device for selective laser melting forming provided by the present invention; Figure 2 It is an exploded view of a variable-speed powder spreading device for selective laser melting forming provided by the present invention; Figure 3 It is a cross-sectional view of a variable-speed powder spreading device for selective laser melting forming provided by the present invention; Figure 4 Schematic diagram of the structure of the cross-section identifier, powder feeding port, and scraper fixing frame; Figure 5 Exploded view of the scraper, resistance sensor, and screw; Reference numerals: 1 - scraper holder, 2 - guide rail, 3 - gear, 4 - cross-section identifier, 5 - powder feeding port, 6 - scraper fixing frame, 7 - powder feeding trough, 8 - sieve, 9 - resistance sensor, 10 - scraper, 11 - fixing frame, 12 - screw. Specific implementation manners

[0019] The present invention will be described in detail below with reference to the accompanying drawings.

[0020] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0021] Embodiment 1 In this embodiment, a variable-speed powder spreading method for selective laser melting forming includes the following steps: (1) Three-dimensional recognition of the formed cross-section on the printing platform is performed by a cross-section identifier installed at the bottom of the scraper holder to obtain geometric features, gray scale, and brightness information of the cross-section; (2) During the movement of the scraper holder, the powder feeding port conveys powder to the printing area, and at the same time, the resistance sensor continuously collects the contact resistance between the scraper and the formed surface; (3) The control system adjusts the rotation speed of the drive motor to drive the variable-speed powder spreading of the scraper holder according to the geometric features, gray scale and brightness information, and the contact resistance: when a formed cross-section is recognized or the resistance value is greater than or equal to the preset threshold, the control system controls the scraper holder to spread powder at a low speed; when a non-formed cross-section is recognized or the resistance value is less than the preset threshold, the control system controls the scraper holder to spread powder at a high speed.

[0022] In the SLM printing of a certain aero-engine blade, the initial speed of the scraper holder is set to 80 mm / s. When the cross-section identifier scans that the gray scale value of the 15th formed surface shows a high-reflection area (indicating the existence of micro-warping), and at the same time the resistance sensor measures that the contact pressure reaches 12 N (the threshold is set to 8 N), the control system immediately reduces the speed to 20 mm / s, making a pre-judgment in advance and reducing the subsequent inability to spread powder and print caused by the friction and extrusion deformation of the formed layer by the scraper. After powder spreading is completed, the layer is melted by laser, and after detection, there is no deformation, and the surface roughness Ra ≤ 15 μm.

[0023] Through the dual-trigger mechanism of "identifying geometric features + resistance threshold", precise variable speed (speed difference 60 mm / s) is achieved, reducing the deformation rate of inclined surfaces, lowering the roughness, and improving the fatigue life of aviation parts compared with traditional uniform-speed powder spreading (80 mm / s).

[0024] Furthermore, the section identifier contains two miniature white light interference sensing cameras, which scan the formed section before powder laying, identify the warping and powder-deficient areas, and feed back the identification results to the control system.

[0025] The cross-section identifier uses a white light sensor and scans at a frequency of 200Hz. When a 0.1mm microcrack is detected on the formed surface (grey value mutation>15%), the system marks the area as "high risk" and the subsequent powder spreading speed is fixed at 10mm / s. The self-cleaning device automatically sprays for 0.5 seconds every 50 layers to ensure that the lens is free of contamination.

[0026] The three-dimensional recognition accuracy is improved, the micro-crack recognition rate is high, and misjudgment caused by lens contamination is avoided.

[0027] Furthermore, the powder feeding port is opened to feed powder only when the scraper frame is moving forward, and the powder feeding trough drops powder downward at an inclined angle of -30°, and the powder is evenly distributed through a 100-mesh screen; when the scraper frame stops or moves backward, the powder feeding port is closed to stop supplying powder.

[0028] The powder delivery port is opened and closed by a pneumatic valve. When moving forward (scraper frame displacement> 0), the valve is open 80%, and when moving backward (displacement = 0), it is completely closed. The inclined groove (-30°) is matched with a 100-mesh screen to improve the uniformity of powder packing density and the qualified rate of single-stroke powder spreading, solving the problem of repeated powder rolling caused by traditional two-way powder delivery. Embodiment 2 Further, such as Figure 1 , 2 4, a variable speed powder spreading device for laser selective melting forming, characterized in that it includes: The scraper frame moves horizontally through a gear transmission mechanism consisting of two guide rails and gears; The cross-section identifier is installed at the front end of the bottom of the scraper frame and contains two miniature white light interference sensing cameras with self-cleaning function, which are used to three-dimensionally identify the printed cross-section; The powder delivery port is located in the middle of the bottom of the scraper frame. It consists of an inclined powder delivery trough and a lower screen. It is connected to the powder bin through the powder pipe inside the scraper frame. The scraper fixing frame is located at the bottom rear end of the scraper frame. The scraper is installed on one side through 5 evenly distributed screws, and 4 resistance sensors close to the scraper are integrated on the other side. The resistance sensors are electrically connected to the control system.

[0029] The device uses an aluminum alloy scraper frame. The distance between the cross-section identifier, powder delivery port, and scraper is 30mm, ensuring that the timing difference of "first identification → then powder delivery → finally scraping" is ≤50ms. The resistance sensor is mounted on the back of the scraper with a sensitivity of 0.01N.

[0030] The structural rigidity is improved, and the timing error is controlled within the cooling time of the laser melting layer (<100 ms) to avoid thermal deformation interference.

[0031] Furthermore, as Figure 4 shown, the gear drive mechanism is driven by a servo motor, and the gear meshes with the rack on the guide rail.

[0032] The drive motor uses a servo motor, which is combined with a planetary reducer to achieve a micro-step control of 0.01 mm / s. When printing overhanging or inclined (≤45°) thin-wall parts, due to insufficient initial shape control, it is easy to warp. The system automatically switches to a low speed of 5 mm / s, with high position repeatability accuracy, superior to traditional belt drives, and solves the problem of "scraping and collapsing" of thin-wall structures.

[0033] Furthermore, the self-cleaning device of the cross-section identifier includes a micro air pump and a flexible brush. When the gray value deviation on the surface of the camera exceeds 5%, the cleaning program is automatically started.

[0034] The self-cleaning device integrates a micro vortex air pump. When the standard deviation of the gray value of the camera > 3%, it triggers a 3-second pulse jet. In the titanium powder printing environment, it can work continuously for 200 hours without manual cleaning, while traditional equipment needs to stop and clean the lens every 4 hours.

[0035] Realize maintenance-free operation in an industrial dust environment.

[0036] Furthermore, the powder feeding trough is wider at the top and narrower at the bottom, the width of the powder outlet is 10 mm, and the mesh number of the sieve is 100 meshes, ensuring that the uniformity error of powder falling is ≤5%.

[0037] The powder feeding trough adopts a gradually shrinking structure (inlet 20 mm → outlet 10 mm). In the printing of stainless steel powder, the stability of the powder flow rate is improved and the blockage frequency is reduced.

[0038] Solve the problem of "arch bridge effect" blockage of metal powder.

[0039] Furthermore, as Figure 5 shown, the resistance sensor is a strain gauge sensor, which is evenly distributed on the side of the scraper fixing frame, with a sampling frequency ≥100 Hz, and the contact pressure between the scraper and the formed surface is monitored in real time.

[0040] 4 sensors are evenly distributed along the scraper, with a spacing of 15 mm, covering 80% of the full length of the scraper. When printing the overhanging structure of an aviation impeller, when the edge sensor detects a sudden increase in resistance, the system immediately reduces the rake angle of the scraper by 5° and decelerates to avoid chipping at the edge of the formed blade. Realize two-dimensional monitoring of the scraper pressure field.

[0041] Further, the control system is integrated into the doctor blade holder or the main control unit of the equipment, receives the three-dimensional data from the cross-section identifier and the pressure signal from the resistance sensor, and dynamically adjusts the motor speed through an algorithm.

[0042] The control system uses a 32-bit processor and integrates a fuzzy PID algorithm. When a complex cross-section (such as a porous lattice) is recognized, the system automatically matches the preset "low speed - high powder supply" strategy, improving the efficiency compared to manual parameter debugging and achieving intelligent matching of process parameters.

[0043] Further, the cross-section identifier, powder feeding port, and doctor blade fixing frame at the bottom of the doctor blade holder are linearly arranged with a spacing of 20 - 50 mm to ensure the timing coordination of the identification, powder feeding, and scraping actions.

[0044] The distance between the identifier - powder feeding port - doctor blade is fixed at 30 mm. When printing a propeller blade, the identifier scans the blade edge 2 ms in advance, the powder feeding port synchronously increases the powder supply by 10%, and the doctor blade completes the edge reinforcement at 18 mm / s. Compared with the traditional synchronous action (0 ms difference), the edge density is improved. "Pre-compensated powder spreading" is achieved through timing optimization.

[0045] Specifically: Referring to Figures 1 to 5 , a variable-speed powder spreading device for selective laser melting forming is specifically adopted to achieve variable-speed powder spreading and improve the printing success rate of parts. The device includes a doctor blade holder 1, and the doctor blade holder 1 is moved through two guide rails 2 and a gear 3. The lower part of the doctor blade holder 1 is successively composed of a cross-section identifier 4, a powder feeding port 5, and a doctor blade fixing frame 6 from front to back. The powder feeding port 5 is composed of a powder feeding groove 7 and a lower screen 8. Four resistance sensors 9 are installed on the side of the doctor blade fixing frame 6. During the powder spreading operation, the doctor blade holder 1 is moved, the cross-section identifier 4 identifies the printing cross-section, and at the same time, the powder feeding port 5 at the bottom of the doctor blade holder 1 drops powder. Subsequently, the doctor blade 10 feeds back to the control system according to the resistance sensor 9 and the cross-section identifier 4 during the movement, and the control system controls the motor and drives the gear 3 to perform variable-speed powder spreading.

[0046] At the same time, the two guide rails 2 and the gear 3 are gear-driven, and the gear 3 is driven by a motor and can move left and right, with high transmission accuracy and stability, which is conducive to variable-speed control.

[0047] At the same time, the cross-section identifier 4 is installed on the fixing frame 11. The cross-section identifier 4 is two miniature white light interference induction cameras, which can perform three-dimensional recognition, precisely recognize the powder spreading or non-powder spreading cross-section, gray level, and brightness, and is equipped with a cleaning device for the camera head, which can perform self-cleaning according to the recognition situation to avoid affecting the recognition effect due to dust accumulation during long-term printing.

[0048] Meanwhile, when the powder spreading is in progress, the two miniature white light interference induction cameras in the cross-section identifier 4 will perform three-dimensional recognition on the printed cross-section, precisely recognize whether the powder has been spread or not, the gray level and brightness of the cross-section. If warping occurs and the brightness increases, it will be fed back to the control system. The control system adjusts the motor speed to perform decelerated powder spreading, reducing the impact of the squeegee on the printed cross-section caused by extrusion and friction, and improving the printing success rate. The cross-section identifier 4 performs rapid powder spreading at the location where there is no printed cross-section.

[0049] Meanwhile, the powder feeding port 5 is located on one side at the bottom of the squeegee holder 1. The powder feeding port 5 includes an upper powder feeding trough 7 and a lower screen 8. The powder feeding trough 7 is an inclined opening, wider at the top and narrower at the bottom, with an inclination of -30° with respect to the vertical direction. A 100-mesh screen is installed at the powder outlet port, and the width of the screen is 10 mm, which serves the purpose of uniform powder spreading. When the squeegee holder 1 advances for work, powder is fed to the powder feeding port 5 through the internal powder pipe of the squeegee holder 1 above the powder feeding port 5. When the squeegee holder 1 stops and moves backward, the powder feeding is closed. The design of the powder feeding port 5 is different from the double-chamber design of the forming chamber and the powder chamber. Only the single-chamber forming of the forming chamber is required, which eliminates the scraping powder travel above the powder supply chamber, further improving the printing efficiency.

[0050] As Figure 3 shown, meanwhile, the squeegee fixing bracket 6 is located on the other side at the bottom of the squeegee holder 1 and is distributed in parallel with the powder feeding port 5. One side of the squeegee fixing bracket 6 installs the squeegee 10 on the squeegee fixing bracket 6 through 5 screws 12, and the 5 screws are evenly distributed. Four resistance sensors 9 are installed on the other side of the squeegee fixing bracket 6. The resistance sensors 9 are connected to the control system through the built-in wire of the squeegee holder 1. The resistance sensors 9 are evenly distributed and closely attached to the squeegee 10. The resistance sensors 9 feed back to the control system according to the resistance between the squeegee 10 and the printed cross-section during movement. The control system adjusts the motor to perform variable-speed powder spreading. When the resistance is large, the powder spreading speed is slow; when the resistance is small, the powder spreading speed is fast; and the powder spreading speed is fast at the location where there is no printed cross-section.

[0051] Compared with the prior art, the present invention can eliminate the scraping powder travel above the powder supply chamber and perform rapid powder spreading at non-forming cross-sections, while taking into account slow powder spreading at the formed cross-section, minimizing the impact of the squeegee on the formed cross-section, avoiding the situation that occurs in traditional uniform powder spreading where the squeegee cannot recognize the easily warped cross-section and hard powder spreading causes deformation and warping and cannot continue printing, improving the printing success rate of parts, and taking into account both printing efficiency and quality.

[0052] Specifically, when printing a part, the cross-section recognizer detects that the brightness value at the edge of the formed surface suddenly increases by 20% (the preset warping threshold is 15%), and it is determined as the risk area of edge warping. The resistance sensor simultaneously detects that the contact resistance increases from 8N to 15N (the threshold is 10N). The control system immediately reduces the powder spreading speed from 60mm / s to 15mm / s and increases the powder feeding amount by 10% to fill the warping gap. After powder spreading, there is no edge cracking in the laser melting layer, and the printing interruption rate caused by warping is reduced compared with the traditional process.

[0053] When the recognizer scans that the gray value of a certain area is 25% lower than the standard powder layer (determined as powder shortage), the system automatically controls the powder feeding port to extend the powder feeding time in this area by 0.5 seconds. At the same time, the doctor blade spreads the powder at a low speed of 20mm / s to ensure that the powder thickness in the powder shortage area meets the standard. The above are only the preferred embodiments of the invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for using a variable speed powder spreading device for laser selective melting forming, characterized in that: The following steps are involved: (1) The cross-section identifier installed at the bottom of the scraper frame performs three-dimensional recognition of the formed cross-section on the printing platform to obtain the geometric features, grayscale and brightness information of the cross-section; (2) During the movement of the scraper holder, the powder feeding port delivers powder to the printing area, and the resistance sensor collects the contact resistance between the scraper and the formed surface in real time; (3) The control system adjusts the speed of the transmission motor according to the geometric features, grayscale brightness information and contact resistance to drive the scraper frame to spread powder at a variable speed: when a formed cross section is identified or the resistance value is greater than or equal to a preset threshold, the scraper frame is controlled to spread powder at a low speed; When a non-formed cross section is identified or the resistance value is less than a preset threshold, the scraper holder is controlled to spread powder at a high speed.

2. The method for using the variable speed powder spreading device for laser selective melting forming according to claim 1 is characterized in that: The cross-section identifier includes two miniature white light interference sensing cameras, which scan and identify the formed cross-section before powder laying. Grayscale values ​​below the threshold are identified as powder-deficient areas, and brightness changes >15% are identified as warping areas. The identification results are fed back to the control system.

3. The method for using the variable speed powder spreading device for laser selective melting forming according to claim 1 is characterized in that: The powder feeding port is opened to feed powder only when the scraper frame is moving forward, and the powder feeding trough drops powder downward at an inclined angle of -30°, and the powder is evenly distributed through a 100-mesh screen; when the scraper frame stops or moves backward, the powder feeding port is closed to stop supplying powder.

4. A variable speed powder spreading device for laser selective melting forming for realizing the method described in any one of claims 1 to 3, characterized in that: include: The scraper frame (1) moves horizontally through a gear transmission mechanism composed of two guide rails (2) and a gear (3); A cross-section identifier (4) is installed at the front end of the bottom of the scraper frame, and includes two miniature white light interference sensing cameras with a self-cleaning function, which are used for three-dimensionally identifying the printed cross-section; The powder delivery port (5) is located in the middle of the bottom of the scraper frame, and is composed of an inclined powder delivery trough (7) and a lower screen (8), and is connected to the powder bin through a powder pipe inside the scraper frame; The scraper fixing frame (6) is located at the rear end of the bottom of the scraper frame. The scraper (10) is installed on one side through 5 evenly distributed screws (12), and 4 resistance sensors (9) close to the scraper are integrated on the other side. The resistance sensors are electrically connected to the control system.

5. The variable speed powder spreading device for laser selective melting forming according to claim 4, characterized in that: The gear transmission mechanism is driven by a servo motor, and the gear (3) meshes with the rack on the guide rail (2).

6. The variable speed powder spreading device for laser selective melting forming according to claim 4, characterized in that: The self-cleaning device of the cross-section identifier (4) comprises a micro air pump and a flexible brush, and when the grayscale value deviation of the camera surface exceeds 5%, the cleaning program is automatically started.

7. The variable speed powder spreading device for laser selective melting forming according to claim 4, characterized in that: The powder delivery trough (7) is larger at the top and smaller at the bottom, the width of the powder outlet port is 10 mm, and the mesh number of the sieve (8) is 100 meshes, ensuring that the powder falling uniformity error is ≤5%.

8. The variable speed powder spreading device for laser selective melting forming according to claim 4 is characterized in that: The resistance sensor (9) is a strain sensor, evenly distributed on the side of the scraper fixing frame (6), with a sampling frequency of ≥100 Hz, and monitors the contact pressure between the scraper and the formed surface in real time.

9. The variable speed powder spreading device for laser selective melting forming according to claim 4, characterized in that: The control system is integrated into the scraper frame (1) or the main control unit of the equipment, receives the three-dimensional data of the cross-section identifier (4) and the pressure signal of the resistance sensor (9), and dynamically adjusts the motor speed through an algorithm.

10. The variable speed powder spreading device for laser selective melting forming according to claim 4, characterized in that: The cross-section identifier (4), the powder delivery port (5), and the scraper fixing frame (6) at the bottom of the scraper frame (1) are arranged linearly with a spacing of 20-50 mm, thereby ensuring the timing coordination of the identification, powder delivery, and powder scraping actions.

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