Defect identification and intelligent process control additive manufacturing method with double doctor blade automatic switching

Abstract

The present application relates to the technical fields of laser additive manufacturing, in particular to a defect identification and intelligent process control additive manufacturing method with automatic switching of double scrapers, comprising the following steps: using a hard scraper in front and a soft scraper in back to perform layer-by-layer powder laying and sintering from the first layer to the nth layer; for the powder laying process of the ith layer, if the resistance of the hard scraper during powder laying is less than a preset value, the powder laying and sintering of the ith layer are completed through a first process. Through the dynamic switching of the soft and hard scrapers, the surface quality and precision of the printed part can be effectively improved while ensuring the printing speed, thereby improving the yield of the part. Through monitoring the powder laying resistance of the hard scraper, it can sensitively and accurately reflect whether there are protrusions in the current powder laying layer, and timely and effectively realize the dynamic switching of the soft and hard scrapers, so that the protrusions in the powder laying layer are gradually improved, and the quality of the printed product and the stability of the printing process are improved.

Description

Technical Field

[0001] This invention relates to the field of laser additive manufacturing technology, and more specifically to a method for additive manufacturing with automatic switching of dual scrapers for defect identification and intelligent process control. Background Technology

[0002] In powder bed fusion additive manufacturing processes such as selective laser melting (SLM) and electron beam melting (EBM), the squeegee is one of the key components ensuring print quality. Currently, commonly used squeegees are divided into two types: soft squeegees and hard squeegees. Soft squeegees have strong compatibility, making it easier to form parts and can accommodate minor local warping deformations; hard squeegees can ensure higher part forming quality, but are more susceptible to part deformation. Even slight warping deformation can easily cause the squeegee to jam, leading to equipment downtime and scrapped parts.

[0003] Therefore, it is essential to balance the use of hard and soft scrapers to scrape powder from the powder layer. As shown in Patent Document 1, the solution uses both hard and soft scrapers, and scans the top of the powder layer with a grating ruler. Once the grating ruler detects a protrusion on the top of the powder layer, the soft scraper is used to spread powder on the current powder layer. However, this solution is limited by the detection accuracy of the grating ruler. If the protrusion caused by deformation is small, the grating ruler cannot accurately capture it. When the hard scraper passes through, it will aggravate the defect at that point, which may lead to manufacturing stoppage or scrapping of the part.

[0004] Existing technical documents:

[0005] Patent document 1CN212072970U: Device for automatically changing the scraper of a 3D printer. Summary of the Invention

[0006] To address the technical problems existing in powder-spreading printing in the prior art, the first aspect of this invention proposes an additive manufacturing method for defect identification and intelligent process control with automatic switching of dual scrapers, comprising the following steps:

[0007] The powder is spread layer by layer from the first layer to the nth layer using a scraping method with a hard scraper in front and a soft scraper behind, and then sintered into shape.

[0008] During the powder spreading process of the i-th layer, if the resistance of the hard scraper during powder spreading is less than the preset value, the powder spreading and sintering of the i-th layer are completed through the first process.

[0009] During the powder spreading process of the i-th layer, if the resistance of the hard scraper is greater than the preset value at a certain position, then only the soft scraper is used to complete the powder spreading after the current position; after the powder spreading of the i-th layer is completed, the image of the current powder spreading layer is obtained, and according to the defect type shown in the image, the defect improvement process is used to spread powder and sinter the next powder spreading layer. After each powder spreading is completed, the image of the powder spreading layer is obtained until there are no defects in the image. Then, the first process is used to complete the powder spreading and sintering of the next layer.

[0010] In the first process, a hard scraper and a soft scraper are used to scrape powder together, with a powder supply of q, a powder thickness of h, and a laser power of w. The defect improvement process uses a soft scraper to scrape powder, with a powder supply of a*q, a powder thickness of a*h, and a laser power of b*w, where a>=1 and b>=1.

[0011] Preferably, the defect types include a first type, a second type, and a third type, and the defect improvement process includes a second process and a third process;

[0012] The first type is where there are no defective areas in the image of the current powder layer. For the first type, the first process is used to complete the powder layering and sintering of the next layer. The second type is where the defective areas in the image of the current powder layer are smaller than a preset value. For the second type, the powder layering of the (i+1)th layer is completed using the second process. The third type is where the defective areas in the image of the current powder layer are larger than a preset value. For the third type, the powder layering and sintering of the (i+1)th layer is completed using the third process.

[0013] After the powder spreading is completed by the second or third process, an image of the powder spreading layer completed by the second or third process is obtained. If the image belongs to the first type, the next powder spreading layer is powder spreading and sintering using the first process. If the image belongs to the second or third type, the second or third process is continued to be used for the next powder spreading layer to powder spreading and sintering until the obtained powder spreading layer image belongs to the first type.

[0014] In the second process, only a soft scraper is used to scrape the powder, with a powder supply of q, a powder scraping thickness of h, and a laser power of w. In the third process, only a soft scraper is used to scrape the powder, with a powder supply of Q greater than q, a powder scraping thickness of H greater than h, and a laser power of W greater than w.

[0015] Preferably, the hard scraper is configured to detach from the powder-spreading surface when the resistance it experiences is greater than a preset value.

[0016] Preferably, the hard scraper can be driven to move between a first position and a second position along the vertical direction of the powder-spreading surface. When the hard scraper is in the first position, the lower end face of the hard scraper coincides with the powder-spreading surface. When the hard scraper is in the second position, the lower end face of the hard scraper moves upward away from the powder-spreading surface.

[0017] Preferably, when scraping the current powder layer according to the first process, the resistance F of the hard scraper is monitored in real time. When F is greater than the preset pressure value, the hard scraper is immediately switched from the first position to the second position, and the soft scraper continues to complete the scraping of the current powder layer.

[0018] Preferably, the maximum resistance encountered by the hard scraper when scraping powder is defined as Fm, and the preset pressure value is 110% Fm.

[0019] Preferably, the defect type of the current powder layer is related to the number and size of defect regions in the current powder layer image.

[0020] Preferably, if the current powder layer image shows fewer than two defective regions and the area of ​​each defective region is less than 5 mm... 2 This belongs to the second type: if the area of ​​any defective region in the current powder layer image is greater than 5mm. 2 It belongs to the third type.

[0021] Preferably, in the third process, the powder coating thickness is changed by altering the movement of the powder-coating substrate. The powder coating thickness H = 2h, and the powder supply Q and laser power W are adjusted according to the powder coating thickness H.

[0022] Preferably, a pressure sensor is installed between the hard scraper and the scraper holder on which the hard scraper is mounted to detect the resistance encountered by the hard scraper during the powder scraping process.

[0023] Compared with the prior art, the advantages of the present invention are as follows:

[0024] This application utilizes dynamic switching between soft and hard squeegees to effectively improve the surface quality and precision of printed parts while maintaining printing speed, thereby increasing the yield rate. By monitoring the toner scraping resistance of the hard squeegee, it can sensitively and accurately detect whether there are protrusions in the current toner layer and achieve timely and effective dynamic switching between soft and hard squeegees. In addition, dual confirmation through visual inspection and pressure sensors avoids misjudgment of printed surface quality and provides a basis for using different process parameters for toner spreading, gradually improving the protrusions in the toner layer and enhancing the quality of printed products and the stability of the printing process. Attached Figure Description

[0025] The accompanying drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component shown in the various figures may be denoted by the same reference numeral. For clarity, not every component is labeled in each figure. Embodiments of various aspects of the invention will now be described by way of example and with reference to the accompanying drawings, wherein:

[0026] Figure 1This is a flowchart illustrating the additive manufacturing method for defect identification and intelligent process control with automatic switching of dual scrapers as shown in this invention.

[0027] Figure 2 This is a schematic diagram illustrating defects that occur during powder spreading, as shown in an embodiment of the present invention;

[0028] Figure 3 This is a schematic diagram illustrating the improvement of defects according to an embodiment of the present invention;

[0029] Figure 4 This is a schematic diagram illustrating the improved defect as shown in an embodiment of the present invention. Detailed Implementation

[0030] To better understand the technical content of the present invention, specific embodiments are described below in conjunction with the accompanying drawings.

[0031] In selective laser melting of metal powder additive manufacturing, uneven temperature gradients can cause residual stress in the parts, leading to warping deformation. This warping deformation greatly affects the scraping of powder by the hard scraper. Even slight warping deformation can easily cause the scraper to jam, resulting in equipment downtime or scrapping of the parts.

[0032] For warping that occurs during powder spreading, the current common practice is to switch between different scrapers. When there is no warping, a hard scraper is used to scrape the powder, and when warping occurs, a soft scraper is used. However, the timing of the switch is a challenge that needs to be addressed. Knowing when to use a soft scraper and when to use a hard scraper is fundamental to completing powder spreading and creating high-quality parts.

[0033] The current method of detecting protrusions on the powder-coated surface using a grating ruler has limited accuracy. Some tiny protrusions cannot be detected. Furthermore, if a hard scraper is used at this time, it will cause small defects to become larger. Especially after laser sintering, the protrusions solidify, and even if a soft scraper is used on the next layer, it is difficult to reduce the risk of workpiece deformation.

[0034] Therefore, this application aims to propose an additive manufacturing method with automatic switching between dual scrapers for defect identification and intelligent process control. By detecting the resistance of powder spreading with a hard scraper, once the resistance increases to a threshold, the hard scraper is retracted, and only a soft scraper is used for powder spreading. Furthermore, a vision inspection system is used to detect defects in the powder spreading layer. If the defect is small, the previous powder spreading thickness is maintained, and only the soft scraper is used for powder spreading. If the defect is large, the layer is not sintered, but the thickness of the powder spreading layer is increased to cover the defect location until there is no defect area. Then, the hard scraper is used for powder spreading to maintain the continuity of additive manufacturing and the quality of the parts.

[0035] Combination Figure 1As shown, this invention proposes a defect identification and intelligent process control additive manufacturing method with automatic switching between dual scrapers, comprising the following steps:

[0036] The powder is spread layer by layer from the first layer to the nth layer using a scraping method with a hard scraper in front and a soft scraper behind, and then sintered into shape.

[0037] In optional embodiments, the terms "hard" and "soft" in "hard scraper" and "soft scraper" are relative to the powder. Typically, a hard scraper is a hard scraper, such as one made of stainless steel, hard alloy (such as tungsten carbide, titanium carbide, etc.), or ceramic material, while a soft scraper is a soft scraper, such as one made of rubber or other elastomers, or soft metal material.

[0038] In this way, by using a combination of hard and soft scrapers, the hard scraper in front ensures that the powder is compacted, while the soft scraper behind ensures that the smoke and dust residue generated during printing can be swept away, ensuring that the powder is clean and free of impurities, thus improving print quality.

[0039] During the powder spreading process of the i-th layer, if the resistance of the hard scraper during powder spreading is less than the preset value, the powder spreading and sintering of the i-th layer are completed through the first process.

[0040] During the powder spreading process of the i-th layer, if the resistance of the hard scraper is greater than the preset value at a certain position, then only the soft scraper is used to complete the powder spreading after the current position; after the powder spreading of the i-th layer is completed, the image of the current powder spreading layer is obtained, and according to the defect type shown in the image, the defect improvement process is used to spread powder and sinter the next powder spreading layer. After each powder spreading is completed, the image of the powder spreading layer is obtained until there are no defects in the image. Then, the first process is used to complete the powder spreading and sintering of the next layer.

[0041] The first process uses a combination of hard and soft scrapers to scrape powder, with a powder supply of q, a powder thickness of h, and a laser power of w. The defect improvement process uses a soft scraper to scrape powder, with a powder supply of a*q, a powder thickness of a*h, and a laser power of b*w, where a>=1 and b>=1.

[0042] It should be understood that the above-mentioned powder-laying manufacturing method includes two processing states: one is the normal processing state, such as the first process, which can be understood as the preset process; the other is the defect improvement processing state where the powder-laying layer encounters protrusions. In the entire part processing, powder-laying and sintering are usually achieved in the normal processing state, according to the predetermined powder-laying thickness and laser power, using a combination of soft and hard scrapers. Only when the part warps due to residual stress at a certain height layer is the defect improvement processing state used. For powder-laying layers with warped structures, hard scrapers cannot be used; only soft scrapers are used. And depending on the type of defect, it is necessary to increase the powder-laying thickness to cover and transition the warped part.

[0043] Furthermore, in this application, by monitoring the scraping resistance of the hard scraper and the powder layer image, the presence or degree of defects in the powder layer can be monitored from two directions, thus avoiding misjudgment of whether the powder layer contains defects and improving the quality of additive manufacturing.

[0044] Monitoring the resistance of a hard scraper in scraping powder

[0045] Monitoring the resistance of the hard scraper during powder scraping: A pressure sensor can be installed between the hard scraper and the scraper holder to monitor the resistance encountered by the hard scraper during powder scraping.

[0046] In an optional embodiment, the hard scraper is configured to detach from the powder-spreading surface when the resistance it experiences is greater than a preset value.

[0047] In an optional embodiment, when scraping the current powder layer according to the first process, the resistance F of the hard scraper is monitored in real time. When F is greater than the preset pressure value, the hard scraper is immediately switched from the first position to the second position, and the soft scraper continues to complete the scraping of the current powder layer.

[0048] When the hard scraper is in the first position, its lower end face is flush with the current powder-spreading plane, scraping the powder to a predetermined height. When the hard scraper is in the second position, the lower end face of the hard scraper rises relative to the first position, disengaging from the powder-spreading plane to avoid contact with the protrusions on the powder-spreading plane.

[0049] Preferably, the maximum resistance encountered by the hard scraper when scraping powder is defined as Fm, and the preset pressure value is 110% Fm.

[0050] Thus, when the hard scraper scrapes powder along the powder spreading direction, if the resistance experienced by the hard scraper exceeds 10% of the maximum resistance Fm, the hard scraper immediately switches from the first position to the second position, and the soft scraper continues to complete the scraping of the current powder spreading layer.

[0051] Specifically, the hard scraper can be driven to move between a first position and a second position along the vertical direction of the powder-spreading surface. When the hard scraper is in the first position, the lower end face of the hard scraper coincides with the powder-spreading surface. When the hard scraper is in the second position, the lower end face of the hard scraper moves upward away from the powder-spreading surface.

[0052] Classify the defects shown in the powder layer image.

[0053] Furthermore, in order to facilitate the setting of different printing processes for different defect levels, the current powder layer is divided into different types according to the defects shown in the powder layer image. For example, the defect types include Type 1, Type 2 and Type 3, and the defect improvement processes include Type 2 and Type 3.

[0054] First process manufacturing

[0055] In an optional embodiment, the first type is that there are no defective areas in the image of the current powder layer, that is, there are no protrusions in the current powder layer, and the protrusions found by the hard scraper through resistance are covered by subsequent powder spreading. For the first type, the first process is used to complete the powder spreading and sintering of the next layer.

[0056] Specifically, when the powder layer is laid according to the first process, if the resistance encountered when scraping the powder with the hard scraper is within the preset range, it means that there are no protrusions in the current powder layer. Therefore, the current powder layer is sintered according to the normal laser power w, and the next powder layer is laid according to the first process.

[0057] Second process manufacturing

[0058] In an optional embodiment, the second type is that the defect area in the image of the current powder layer is smaller than a preset value, that is, the current powder layer has protrusions, but the number and area of ​​the protrusions are not large. For the second type, the powder layer of the i+1th layer is completed by the second process.

[0059] Specifically, when the powder layer is laid according to the first process, if the resistance encountered by the hard scraper exceeds the preset range, the hard scraper is raised, and only the soft scraper is used to complete the powder laying of the current powder layer. After the powder laying is completed, the image of the current powder layer is obtained through the vision recognition system. If the defect area in the image of the current powder layer is smaller than the preset value, then in the next powder layer, other parameters are kept unchanged, and only the soft scraper is used for powder laying, that is, the original powder supply is kept at q and the powder thickness is kept at h. After the powder laying is completed, the image of the current powder layer is obtained again through the vision recognition system. If the defect disappears, the laser power is kept at w for sintering, and the next layer is laid using the first process. If the defect does not disappear but is still smaller than the preset value, the second process is continued to be used for powder laying and sintering of the next layer until the defect disappears.

[0060] Third process manufacturing

[0061] In an optional embodiment, the third type is that the defect area in the current powder layer image is larger than a preset value, that is, the current powder layer has protrusions, and the number or area of ​​the protrusions is large. For the third type, the powder laying and sintering of the i+1th layer is completed by the third process.

[0062] In the third process, the powder coating thickness is changed by altering the movement of the powder-coated substrate. The powder coating thickness H = 2h, and the powder supply Q and laser power W are adjusted according to the powder coating thickness H.

[0063] Specifically, when spreading powder in the first process, if the resistance encountered by the hard scraper exceeds a preset range, the hard scraper is raised, and only the soft scraper is used to complete the current powder layer. After the scraping is completed, an image of the current powder layer is obtained through a vision recognition system. If the defect area in the image of the current powder layer is larger than a preset value, the thickness of the powder layer is changed in the next powder layer, and the powder supply and laser power are changed accordingly to meet the sintering requirements of the thicker powder layer. The soft scraper is then used to scrape the powder. The thicker powder layer can better cover the protrusions. After the current powder layer is completed, the image of the current powder layer is obtained again through the vision recognition system. If the defect disappears, the laser power is maintained at w for sintering, and the next layer is spread using the first process. If the defect does not disappear but is smaller than the preset value, the second process is used to spread powder and sinter the next layer until the defect disappears.

[0064] In the above embodiments, the second process only uses a soft scraper to scrape powder, with a powder supply of q, a powder thickness of h, and a laser power of w. It can be seen that, compared with the first process, the second process only changes the scraper used for powder scraping, while the powder supply, powder thickness, and laser power remain unchanged. The third process only uses a soft scraper to scrape powder, with a powder supply Q greater than q, a powder thickness H greater than h, and a laser power W greater than w. Compared with the first process, the third process not only changes the scraper used for powder scraping, but also changes the powder supply, powder thickness, and laser power, aiming to use a thicker powder layer to cover and transition the defective parts.

[0065] Furthermore, to verify whether the defect improvement process covers the protrusions in the current powder layer, after each powder layer is completed by the second or third process, an image of the powder layer completed by the second or third process is obtained. If the image belongs to the first type, the next powder layer is powdered and sintered using the first process. If the image belongs to the second or third type, the second or third process is continued to be used for the next powder layer to powder layer and sinter until the obtained powder layer image belongs to the first type.

[0066] Furthermore, in order to quantify the defect type of the powder layer, the defect type of the current powder layer is related to the number and size of defect regions in the current powder layer image.

[0067] In an optional embodiment, if the current powder layer image shows fewer than two defective regions and the area of ​​each defective region is less than 5 mm... 2 This belongs to the second type: if the area of ​​any defective region in the current powder layer image is greater than 5mm. 2 It belongs to the third type.

[0068] In a specific embodiment, when scraping powder onto a certain powder layer, if the resistance encountered by the hard scraper exceeds a preset value, the hard scraper immediately rises, and the powder spreading action for the current layer is completed using only the soft scraper. Then, an image of the current powder layer is acquired using a vision camera, and deformation defects are identified. If there are fewer than two protrusions and the area of ​​each protrusion is ≤5mm², the defect is considered resolved. 2 If the deformation is severe, continue using the soft scraper and observe whether the printing process improves. If the deformation is severe, the area of ​​any protruding part is greater than 5mm². 2 The camera signal is then fed back to the controller, which automatically adjusts the powder layer thickness to twice the original and increases the laser power to achieve a confirmed coverage transition during printing. The camera then visually inspects whether the defects have been improved. Once improved, the normal layer thickness and printing parameters are restored to continue printing.

[0069] Combination Figure 2-4 As shown, the location and area of ​​defects can be accurately identified by the above method. By switching to a soft scraper and / or increasing the powder thickness, the raised areas are covered with powder. At the same time, after each powder application, image recognition is used to confirm whether the raised areas have disappeared, as shown in the red circle in the figure. After applying powder layer by layer, the defects in the powder layer are gradually improved.

[0070] In conjunction with the above embodiments, this application, through the dynamic switching of soft and hard squeegees, can effectively improve the surface quality and precision of printed parts while ensuring printing speed, thereby increasing the yield rate of the parts. By monitoring the toner scraping resistance of the hard squeegee, it can sensitively and accurately reflect whether there are protrusions in the current toner layer and realize timely and effective dynamic switching between soft and hard squeegees. In addition, through dual confirmation by visual inspection and pressure sensors, it avoids misjudgment of the printed surface quality and provides a basis for using different process parameters for toner spreading, so that the protrusions in the toner layer are gradually improved, thereby improving the quality of printed products and the stability of the printing process.

[0071] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. A method for additive manufacturing with automatic switching between dual scrapers for defect identification and intelligent process control, characterized in that, Includes the following steps: The powder is spread layer by layer from the first layer to the nth layer using a scraping method with a hard scraper in front and a soft scraper behind, and then sintered into shape. During the powder spreading process of the i-th layer, if the resistance of the hard scraper during powder spreading is less than the preset value, the powder spreading and sintering of the i-th layer are completed through the first process. During the powder spreading process of the i-th layer, if the resistance of the hard scraper is greater than the preset value at a certain position, then only the soft scraper is used to complete the powder spreading after the current position. After the powder spreading of the i-th layer is completed, the i-th powder spreading layer is not sintered, and the image of the current powder spreading layer is obtained. According to the defect type shown in the image, the next powder spreading layer is powder spread and sintered using either the defect improvement process or the first process. When the defect improvement process is used, the image of the powder spreading layer is obtained after each powder spreading is completed until there are no defects in the image. Then, the first process is used to complete the powder spreading and sintering of the next layer. In the first process, a hard scraper and a soft scraper are used to scrape powder together, with a powder supply of q, a powder thickness of h, and a laser power of w. The defect improvement process uses a soft scraper to scrape powder, with a powder supply of a*q, a powder thickness of a*h, and a laser power of b*w, where a>=1 and b>=1.

2. The additive manufacturing method for defect identification and intelligent process control with automatic switching of dual scrapers according to claim 1, characterized in that, The defect types include a first type, a second type, and a third type, and the defect improvement process includes a second process and a third process; The first type is where there are no defective areas in the current powder layer image. For the first type, the first process is used to complete the powder spreading and sintering of the next layer. The second type is when the defect area in the image of the current powder layer is smaller than the preset value. For the second type, the powder laying and sintering of the (i+1)th layer are completed through the second process. The third type is when the defect area in the image of the current powder layer is larger than the preset value. For the third type, the powder laying and sintering of the (i+1)th layer are completed through the third process. After the powder spreading is completed by the second or third process, an image of the powder spreading layer completed by the second or third process is obtained. If the image belongs to the first type, the next powder spreading layer is powder spreading and sintering using the first process. If the image belongs to the second or third type, the second or third process is continued to be used for the next powder spreading layer to powder spreading and sintering until the obtained powder spreading layer image belongs to the first type. In the second process, only a soft scraper is used to scrape the powder, with a powder supply of q, a powder scraping thickness of h, and a laser power of w. In the third process, only a soft scraper is used to scrape the powder, with a powder supply of Q greater than q, a powder scraping thickness of H greater than h, and a laser power of W greater than w.

3. The additive manufacturing method for defect identification and intelligent process control with automatic switching of dual scrapers according to claim 1, characterized in that, The hard scraper is configured to detach from the powder-spreading surface when the resistance it experiences exceeds a preset value.

4. The additive manufacturing method for defect identification and intelligent process control with automatic switching of dual scrapers according to claim 1, characterized in that, The hard scraper can be driven to move between a first position and a second position along the vertical direction of the powder-spreading surface. When the hard scraper is in the first position, the lower end face of the hard scraper coincides with the powder-spreading surface. When the hard scraper is in the second position, the lower end face of the hard scraper moves upward away from the powder-spreading surface.

5. The additive manufacturing method for defect identification and intelligent process control with automatic switching of dual scrapers according to claim 4, characterized in that, When scraping powder from the current powder layer according to the first process, the resistance F of the hard scraper is monitored in real time. When the resistance F is greater than the preset value, the hard scraper is immediately switched from the first position to the second position, and the soft scraper continues to complete the scraping of the current powder layer.

6. The additive manufacturing method for defect identification and intelligent process control with automatic switching of dual scrapers according to claim 5, characterized in that, The maximum resistance encountered by a hard scraper when scraping powder is defined as Fm, and the preset value is 110% Fm.

7. The additive manufacturing method for defect identification and intelligent process control with automatic switching of dual scrapers according to claim 2, characterized in that, The defect type of the current powder layer is related to the number and size of defect regions in the current powder layer image.

8. The additive manufacturing method for defect identification and intelligent process control with automatic switching of dual scrapers according to claim 7, characterized in that, If the current powder layer image contains fewer than two defective areas and the area of ​​each defective area is less than 5mm... 2 This belongs to the second type: if the area of ​​any defective region in the current powder layer image is greater than 5mm. 2 It belongs to the third type.

9. The additive manufacturing method for defect identification and intelligent process control with automatic switching of dual scrapers according to claim 2, characterized in that, In the third process, the powder coating thickness is changed by altering the movement of the powder-coated substrate. The powder coating thickness H = 2h, and the powder supply Q and laser power W are adjusted according to the powder coating thickness H.

10. The additive manufacturing method for defect identification and intelligent process control with automatic switching of dual scrapers according to claim 1, characterized in that, A pressure sensor is installed between the hard scraper and the scraper holder that houses the hard scraper to detect the resistance encountered by the hard scraper during the powder scraping process.

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