A variable-speed powder spreading device for selective laser melting forming and its usage method

Abstract

The present invention discloses a variable-speed powder spreading device for selective laser melting forming and its usage method, which realizes dynamic powder spreading control through a dual mechanism of cross-section recognition and resistance feedback. The device consists of a scraper frame, a three-dimensional white light recognizer, an inclined powder feeding port, and distributed resistance sensors. The scraper frame performs intelligent variable speed through a gear transmission mechanism: high-speed powder spreading in the non-forming area, and low-speed powder spreading in the formed critical structures (such as structures with an angle ≤ 45° and thin-walled and easily deformed parts). The innovative use of single-bin and one-way powder feeding realizes uniform powder distribution through a -30° inclined groove and a 100-mesh sieve, cancels the ineffective stroke of the powder supply bin, and reduces the impurity pollution rate. The recognizer integrates a self-cleaning function, scans the micro-cracks on the formed surface in real time, the resistance sensors dynamically feedback the contact pressure, and the control system matches the optimal parameters through a fuzzy PID algorithm.

Description

Technical Field

[0001] The present invention relates to the technical field of 3D printing, and specifically provides a variable-speed powder spreading method and device based on cross-section recognition and resistance feedback during the Selective Laser Melting (SLM) forming process, 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 melting metal powder with a laser, and has advantages such as high forming accuracy, 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 accuracy and success rate, and the powder spreading process is completed by the movement of a doctor blade. The traditional process uses uniform-speed powder spreading, and there are the following technical bottlenecks:

[0003] Defects of uniform-speed powder spreading:

[0004] The doctor blade of existing SLM equipment usually moves at a constant speed. When the doctor blade passes through a formed critical inclined structure (such as an inclined plane 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.

[0005] Lack of intelligent feedback mechanism:

[0006] Traditional powder spreading devices do not integrate 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 making it difficult to balance efficiency and quality.

[0007] Redundancy in powder supply stroke:

[0008] Some existing devices adopt a double-chamber (forming chamber and powder supply chamber) design, and the doctor blade needs to move back and forth between the two chambers to complete powder scraping, increasing the ineffective stroke and time cost.

[0009] Although there are attempts in the prior art to improve the powder spreading quality by adjusting the doctor blade angle and optimizing the powder fluidity, etc., the core problem of "dynamically recognizing 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

[0010] 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.

[0011] The technical solution adopted by the present invention is as follows:

[0012] A variable-speed powder spreading method for selective laser melting forming includes the following steps:

[0013] (1) A three-dimensional recognition of the formed cross-section on the printing platform is carried out by a cross-section recognizer installed at the bottom of the doctor blade holder to obtain the geometric features, gray scale and brightness information of the cross-section;

[0014] (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 continuously collects the contact resistance between the doctor blade and the formed surface;

[0015] (3) The control system adjusts the rotation speed of the driving motor to drive the variable-speed powder spreading of the doctor blade 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 doctor blade holder is controlled 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 doctor blade holder is controlled to spread powder at a high speed.

[0016] Further, the cross-section recognizer includes 2 micro 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.

[0017] Further, the powder feeding port only opens for powder feeding when the doctor blade holder moves forward. The powder feeding trough slopes downward at an angle of -30° to drop powder, 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.

[0018] Further, a variable-speed powder spreading device for selective laser melting forming, characterized by comprising:

[0019] A doctor blade holder that moves horizontally through a gear transmission mechanism composed of two guide rails and gears;

[0020] A cross-section recognizer, installed at the front end of the bottom of the doctor blade holder, includes 2 micro white light interference induction cameras with self-cleaning functions, and is used for three-dimensional recognition of the printing cross-section;

[0021] 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;

[0022] A doctor blade fixing frame, located at the rear end of the bottom of the doctor blade holder, installs a 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.

[0023] Further, the gear transmission mechanism is driven by a servo motor, and the gear meshes with the rack on the guide rail.

[0024] Furthermore, the self-cleaning device of the cross-section identifier includes a micro air pump and a flexible brush. When the deviation of the grayscale value on the surface of the camera exceeds 5%, the cleaning program is automatically started.

[0025] 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 mesh, ensuring that the uniformity error of the powder falling is ≤ 5%.

[0026] Furthermore, the resistance sensor is a strain type sensor, 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.

[0027] Furthermore, the control system is integrated into the scraper frame or the main control unit of the equipment, receives the three-dimensional data of the cross-section identifier and the pressure signal of the resistance sensor, and dynamically adjusts the motor speed through an algorithm.

[0028] Furthermore, the cross-section identifier, the powder feeding port, and the scraper fixing frame at the bottom of the scraper frame are linearly arranged, with a spacing of 20 - 50 mm, ensuring the timing coordination of the identification, powder feeding, and scraping actions.

[0029] In summary, due to the adoption of the above technical solutions, the beneficial effects of the present invention are as follows:

[0030] Precise powder control and uniform 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 fall smoothly, 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.

[0031] Real-time monitoring and stable feedback: The cross-section identifier has three-dimensional identification and self-cleaning functions, 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 type resistance sensor has a sampling frequency ≥ 100 Hz, monitors the contact pressure between the scraper and the formed surface in real time and feeds back the data. The control system dynamically adjusts the moving speed of the scraper frame 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.

[0032] High-precision transmission and precise movement: The gear transmission mechanism is driven by a servo motor, 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 scraper frame 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 consistent powder spreading quality for each layer, and improves the overall printing quality and performance of the parts. Description of the Drawings

[0033] Figure 1 Schematic structural diagram of a variable-speed powder spreading device for selective laser melting forming provided by the present invention;

[0034] Figure 2 Exploded view of a variable-speed powder spreading device for selective laser melting forming provided by the present invention;

[0035] Figure 3 Cross-sectional view of a variable-speed powder spreading device for selective laser melting forming provided by the present invention;

[0036] Figure 4 Schematic structural diagram of a cross-section identifier, powder feeding port, and scraper fixing frame;

[0037] Figure 5 Exploded view of a scraper, resistance sensor, and screw;

[0038] 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 - screen, 9 - resistance sensor, 10 - scraper, 11 - fixing frame, 12 - screw. Detailed implementation manners

[0039] The present invention will be described in detail below with reference to the accompanying drawings.

[0040] In order to make the objectives, technical solutions, and advantages of the present invention clearer and more understandable, 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.

[0041] Embodiment 1

[0042] In this embodiment, a variable-speed powder spreading method for selective laser melting forming includes the following steps:

[0043] (1) The formed cross-section on the printing platform is three-dimensionally recognized by a cross-section identifier installed at the bottom of the scraper holder to obtain the geometric features, grayscale, and brightness information of the cross-section;

[0044] (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;

[0045] (3) The control system adjusts the rotational speed of the drive motor to drive the variable-speed powder spreading of the scraper holder according to the geometric features, grayscale and brightness information, and contact resistance: when a formed cross-section is recognized or the resistance value is greater than or equal to the preset threshold, the scraper holder is controlled 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 scraper holder is controlled to spread powder at a high speed.

[0046] In the SLM printing of an aircraft engine blade, the initial scraper speed was set at 80 mm / s. When the cross-section detector detected a highly reflective grayscale area on the 15th layer (indicating slight warping), and the resistance sensor measured a contact pressure of 12 N (with a threshold of 8 N), the control system immediately reduced the speed to 20 mm / s. This proactive approach reduced the risk of deformation of the formed layer due to scraper friction and compression, which could prevent subsequent powder coating. After powder coating, the laser melted the layer, confirming no deformation and a surface roughness of Ra ≤ 15 μm.

[0047] Through the dual trigger mechanism of "identifying geometric features + resistance threshold", precise speed change (speed difference 60mm / s) is achieved, which reduces the deformation rate of the inclined surface and the roughness compared to traditional uniform powder spreading (80mm / s), thereby improving the fatigue life of aviation parts.

[0048] Furthermore, the cross-section identifier contains two miniature white light interference sensing cameras, which scan the formed cross-section before powder laying, identify the warping and powder-deficient areas, and feed back the identification results to the control system.

[0049] The cross-section recognition system uses a white light sensor and scans at a frequency of 200Hz. If a 0.1mm microcrack (greyscale value change >15%) is detected on the formed surface, the system marks the area as "high risk" and the subsequent powder spreading speed is fixed at 10mm / s. A self-cleaning device automatically sprays air for 0.5 seconds every 50 layers to ensure the lens is contaminated.

[0050] The three-dimensional recognition accuracy is improved, the micro-crack recognition rate is high, and misjudgment caused by lens contamination is avoided.

[0051] 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 inclination 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.

[0052] The powder feed port is opened and closed using a pneumatic valve. During forward movement (scraper displacement > 0), the valve opens 80% and during backward movement (displacement = 0), it closes completely. The inclined trough (-30°) combined with a 100-mesh screen improves powder packing density uniformity, increasing the pass rate of single-pass powder spreading and resolving the problem of repeated powder compaction caused by traditional two-pass powder feeding.

[0053] Example 2

[0054] Further, such as Figure 1 、 2 4, a variable speed powder spreading device for laser selective melting forming, characterized by comprising:

[0055] The scraper frame moves horizontally through a gear transmission mechanism consisting of two guide rails and gears;

[0056] The cross-section identifier is installed at the front end of the scraper frame and contains two miniature white light interference sensing cameras with self-cleaning function, which are used to 3D identify the printed cross-section;

[0057] The powder feeding port is located in the middle of the bottom of the scraper frame. It consists of an inclined powder feeding trough and a lower screen. It is connected to the powder bin through the powder pipe inside the scraper frame.

[0058] 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 the other side is integrated with 4 resistance sensors close to the scraper. The resistance sensors are electrically connected to the control system.

[0059] The device utilizes an aluminum alloy scraper. The distance between the cross-section identifier, powder feed port, and scraper is 30mm, ensuring a time delay of ≤50ms for the process of "identification, powder feed, and scraping." A resistance sensor with a sensitivity of 0.01N is mounted on the back of the scraper.

[0060] The structural rigidity is improved, and the timing error is controlled within the cooling time of the laser melt layer (<100ms) to avoid thermal deformation interference.

[0061] Further, such as Figure 4 As shown, the gear transmission mechanism is driven by a servo motor, and the gear is engaged with the rack on the guide rail.

[0062] The drive motor utilizes a servo motor, coupled with a planetary reducer, to achieve micro-step control of 0.01mm / s. When printing suspended or tilted (≤45°) thin-walled parts, which are prone to warping due to insufficient initial shape control, the system automatically switches to a low speed of 5mm / s. This provides high position repeatability, surpassing traditional belt drives and resolving the problem of "scratching and collapse" in thin-walled structures.

[0063] Furthermore, the self-cleaning device of the cross-section identifier includes a micro air pump and a flexible brush. When the grayscale value deviation of the camera surface exceeds 5%, the cleaning program is automatically started.

[0064] The self-cleaning device integrates a micro-vortex air pump, which triggers a 3-second pulsed air jet when the standard deviation of the camera's grayscale value exceeds 3%. In a titanium powder printing environment, it can operate continuously for 200 hours without manual cleaning, while traditional equipment requires downtime every four hours for mirror cleaning.

[0065] Achieve maintenance-free operation in industrial-grade dust environments.

[0066] Furthermore, the powder feeding trough is larger at the top and smaller at the bottom, the width of the powder outlet port is 10mm, and the mesh size of the screen is 100 mesh, ensuring that the powder falling uniformity error is ≤5%.

[0067] The powder feeding trough adopts a gradually tapered contraction structure (inlet 20mm → outlet 10mm), which improves the stability of powder flow rate and reduces the blockage frequency during the printing of stainless steel powder.

[0068] Solve the problem of "arch effect" blockage of metal powder.

[0069] Furthermore, as Figure 5 shown, the resistance sensor is a strain gauge sensor, evenly distributed on the side of the blade holder, with a sampling frequency ≥ 100Hz, and it monitors the contact pressure between the blade and the formed surface in real time.

[0070] 4 sensors are evenly distributed along the blade, with a spacing of 15mm, covering 80% of the full length of the blade. When printing the suspended structure of an aviation impeller, the edge sensor detects a sudden increase in resistance, and the system immediately reduces the rake angle of the blade by 5° and decelerates to avoid chipping at the edge of the formed blade. Realize two-dimensional monitoring of the blade pressure field.

[0071] Furthermore, the control system is integrated into the blade holder or the main control unit of the equipment, receives the three-dimensional data of the cross-section identifier and the pressure signal of the resistance sensor, and dynamically adjusts the motor speed through an algorithm.

[0072] 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, which improves the efficiency compared to manual parameter debugging. Realize intelligent matching of process parameters.

[0073] Furthermore, the cross-section identifier, powder feeding port, and blade holder at the bottom of the blade holder are linearly arranged, with a spacing of 20 - 50mm, ensuring the timing coordination of the recognition, powder feeding, and scraping actions.

[0074] The distance between the identifier - powder feeding port - blade is fixed at 30mm. When printing a propeller blade, the identifier scans the blade edge 2ms in advance, the powder feeding port synchronously increases the powder supply by 10%, and the blade completes edge reinforcement at 18mm / s. Compared with the traditional synchronous action (0ms difference), the edge density is improved. Achieve "pre-compensated powder spreading" through timing optimization.

[0075] Specifically:

[0076] Refer to Figures 1 to 5, specifically, a variable-speed powder spreading device for selective laser melting forming is 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 moves 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 trough 7 and a lower screen 8. Four resistance sensors 9 are installed on the side of the doctor blade fixing frame 6. During powder spreading work, the doctor blade holder 1 is moved, and the cross-section identifier 4 identifies the printing cross-section. At the same time, powder falls from the powder feeding port 5 at the bottom of the doctor blade holder 1. Subsequently, the doctor blade 10 feeds back to the control system according to the resistance sensors 9 and the cross-section identifier 4 during movement, and the control system controls the motor and drives the gear 3 to perform variable-speed powder spreading.

[0077] At the same time, the two guide rails 2 and the gear 3 are gear-driven. The gear 3 is driven by a motor and can move left and right. The transmission accuracy and stability are high, which is conducive to variable-speed control.

[0078] 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 not, cross-section gray scale, and brightness of the cross-section. At the same time, it has a built-in camera head cleaning device, which can perform self-cleaning according to the recognition situation, avoiding the influence of dust accumulation during long-term printing on the recognition effect.

[0079] At the same time, when the cross-section identifier 4 is spreading powder, 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 the powder spreading or not, cross-section gray scale, and brightness of the cross-section. If warping occurs and the brightness increases, it will be fed back to the control system, and the control system adjusts the motor speed to perform deceleration powder spreading, reducing the influence of the doctor blade on the extrusion and friction of the printed cross-section, and improving the printing success rate. The cross-section identifier 4 performs rapid powder spreading at the place where there is no printed cross-section.

[0080] At the same time, the powder feeding port 5 is located on one side of the bottom of the doctor blade 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 port, larger at the top and smaller at the bottom, with an inclination of -30° to the vertical direction. A 100-mesh screen is installed at the powder outlet port, and the screen width is 10 mm, which serves the purpose of uniform powder spreading. When the doctor blade holder 1 advances, powder is fed to the powder feeding port 5 through the internal powder pipe of the doctor blade holder 1 above the powder feeding port 5. When the doctor blade 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 a single-chamber forming in the forming chamber is required, which subtracts the powder scraping stroke moving above the powder supply chamber, further improving the printing efficiency.

[0081] Such as Figure 3As shown in the figure, at the same time, the scraper fixing frame 6 is located on the other side of the bottom of the scraper frame 1 and is distributed in parallel with the powder feeding port 5. One side of the scraper fixing frame 6 installs the scraper 10 on the scraper fixing frame 6 through 5 screws 12, and the 5 screws are evenly distributed. On the other side of the scraper fixing frame 6, 4 resistance sensors 9 are installed. The resistance sensors 9 are connected to the control system through the built-in wire of the scraper frame 1. The resistance sensors 9 are evenly distributed and closely adhere to the scraper 10. The resistance sensors 9 feed back to the control system according to the resistance between the scraper 10 and the printed 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 place without the printed section.

[0082] Compared with the prior art, the present invention can subtract the powder scraping stroke moving above the powder supply bin and, while quickly spreading powder at the non-formed section, take into account slow powder spreading at the formed section, minimizing the influence of the scraper on the formed section, avoiding the situation that occurs in traditional uniform powder spreading where the scraper cannot identify the easily warped section and hard powder spreading causes deformation and warping and the printing cannot continue, improving the printing success rate of the part, and taking into account both printing efficiency and quality.

[0083] Specifically, when printing a part, when the cross-section identifier detects that the brightness value at the edge of the formed surface suddenly increases by 20% (the preset warping threshold is 15%), it is determined as the edge warping risk area. The resistance sensor synchronously detects that the contact resistance rises from 8N to 15N (threshold 10N), and 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.

[0084] When the identifier scans that the gray value of a certain area is lower than 25% of the standard powder layer (determined as powder shortage), the system automatically controls the powder feeding port to extend the powder feeding time by 0.5 seconds in this area, and at the same time, the scraper spreads 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, and improvements made within the spirit and principle of the present invention shall be included within 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 characteristics, grayscale and brightness information of the cross-section; (2) During the movement of the scraper holder, the powder feed 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 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 is controlled to spread powder at a low speed; When a non-formed section is identified or the resistance value is less than a preset threshold, the scraper holder is controlled to spread powder at high speed; 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.

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

3. A variable speed powder spreading device for laser selective melting forming for implementing the method according to any one of claims 1-2, 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), mounted at the front end of the bottom of the scraper frame, comprises two miniature white light interference sensing cameras with a self-cleaning function, for three-dimensionally identifying printed cross-sections; The powder feeding port (5) is located in the middle of the bottom of the scraper frame, and is composed of an inclined powder feeding 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). The other side is integrated with 4 resistance sensors (9) close to the scraper. The resistance sensors are electrically connected to the control system.

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

5. The variable speed powder spreading device for laser selective melting forming according to claim 3 is characterized in that: The self-cleaning device of the cross-section identifier (4) includes 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.

6. The variable speed powder spreading device for selective laser melting forming according to claim 3, characterized in that: The powder feeding 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 screen (8) is 100 meshes, ensuring that the powder falling uniformity error is ≤5%.

7. The variable speed powder spreading device for selective laser melting according to claim 3, 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.

8. The variable speed powder spreading device for selective laser melting forming according to claim 3, 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.

9. The variable speed powder spreading device for selective laser melting forming according to claim 3, characterized in that: The cross-section identifier (4), powder feeding port (5), and scraper fixing frame (6) at the bottom of the scraper frame (1) are arranged linearly with a spacing of 20-50 mm, ensuring the timing coordination of the identification, powder feeding, and powder scraping actions.

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