Intelligent monitoring and self-regulation system and method for warping deformation of laser powder bed fusion additive manufacturing

Abstract

The application discloses a kind of laser powder bed fusion additive manufacturing warping deformation intelligent monitoring and self-regulation control system and method thereof, including powder platform, powder laying mechanism, first high-definition camera, second high-definition camera and user terminal remote monitoring module, first high-definition camera is used to shoot block surface image;Second high-definition camera is used to shoot the image of current powder layer;User terminal remote monitoring module judges whether the surface warping degree of each forming block is beyond preset range according to the received block surface image, and controls the printing working condition of corresponding forming block according to the judgment result;User terminal remote monitoring module assesses the powder laying quality of current powder layer according to the received current powder layer image, and determines the powder supply of powder cylinder according to the evaluation result.Therefore, the application can automatically monitor the influence of warping block on the powder laying quality of surrounding blocks, and then adaptively adjust the powder supply, reducing the influence of warping block on the forming quality of surrounding blocks.

Description

TECHNICAL FIELD

[0001] The present application relates to a laser powder bed fusion additive manufacturing warping deformation intelligent monitoring and autonomous regulation system and method thereof, and belongs to the field of laser powder bed fusion additive manufacturing. BACKGROUND

[0002] When exploring the printing process window of new materials by using material high-throughput testing and multi-material integrated printing, many bulk samples with different process parameters are printed on a substrate, which can reduce the experimental period and quickly obtain suitable process parameters. However, bulk samples with unsuitable process parameters will warp, for example, tungsten alloy, which is particularly sensitive to energy input. Excessive energy input will cause serious warping. Warping is a cumulative process, from mild warping to severe warping. Mildly warped bulk samples can reduce the degree of subsequent warping by adjusting the powder laying amount, but severely warped bulk samples will block the powder laying wall movement, not only damaging the powder laying device, but also stopping all bulk sample printing work due to excessive load on the powder laying wall. Bulk samples with suitable process parameters will not warp, but warped bulk samples will also affect the powder laying quality of surrounding bulk samples, which may cause serious damage to the forming quality. Therefore, warped bulk samples not only affect the powder laying quality of surrounding bulk samples, leading to damage to the forming quality, but also directly stop all bulk sample printing work due to severe warping, which not only increases the printing cost, but also affects the accurate acquisition of process parameters.

[0003] Currently, quality monitoring data collected during the printing process cannot establish a correlation between the heat distribution of the formed bulk sample and the cracks and warping caused by heat accumulation. In addition, during the printing process, manual attendance is usually required to observe the printing situation near the printing equipment, and the printing of warped bulk samples is manually stopped. Other bulk samples without warping continue to print. Sometimes the printing task takes too long, and it is difficult for workers to observe the printing quality on site for a long time, or workers will inevitably ignore minor situations during printing, leading to poor forming quality. SUMMARY

[0004] The present application aims to provide a laser powder bed fusion additive manufacturing warping deformation intelligent monitoring and autonomous regulation system and method thereof, which integrates precise identification of warped bulk samples, automatic selective stopping of warped bulk sample printing, real-time detection of powder laying quality and adaptive compensation of powder supply amount, multi-directional data acquisition, and user-side remote monitoring functions. It not only meets the multi-bulk sample printing scenario, but also can be applied to the online monitoring scenario of multiple complex components simultaneously forming, which has important practical significance for improving the intelligent level of forming and the stability of printing.

[0005] To achieve the above technical purposes, the present application will adopt the following technical solutions:

[0006] The application discloses a kind of laser powder bed fusion additive manufacturing warping deformation intelligent monitoring and autonomous regulation and control system, including powder platform, forming cylinder, powder cylinder and powder laying mechanism;It further includes data acquisition device and user terminal remote monitoring module, the data acquisition device includes first, second high-definition camera, wherein:

[0007] The first high-definition camera is built on the powder laying mechanism, is used to shoot the block surface image including all forming blocks layer by layer, and can transmit the block surface image shot to the user terminal remote monitoring module;

[0008] The second high-definition camera is built on the powder laying mechanism, is used to shoot the image of current powder layer that powder laying mechanism is laid on powder platform, and can transmit the current powder layer image shot to the user terminal remote monitoring module;

[0009] The user terminal remote monitoring module judges whether the surface warping degree of each forming block is beyond preset range according to the block surface image fed back by the first high-definition camera, and controls the printing working condition of corresponding forming block according to the judgment result;

[0010] The user terminal remote monitoring module estimates the powder laying quality of current powder layer according to the current powder layer image transmitted by the second high-definition camera, and determines the powder supply volume of powder cylinder according to the evaluation result.

[0011] Preferably, the user terminal remote monitoring module includes block warping identification and shutdown module;The block warping identification and shutdown module includes warping block image processing module and warping block image evaluation module;Wherein:

[0012] The warping block image processing module is used to receive the block surface image fed back by the first high-definition camera and carries out filtering denoising processing to the block surface image received frame by frame, and calculates standard gray value when the deposition layer number of each forming block reaches preset layer number, and calculates the real-time gray value of each forming block in each deposition layer after preset layer number one by one, and uploads the percentage Y of real-time gray value to standard gray value to warping block image evaluation module;Wherein:

[0013] Standard gray value Gray0 calculation formula is as follows:

[0014] Gray0=(0.299R0+0.587G0+0.144B0) / N

[0015] Wherein, R0 is the red component of all pixel points in block surface image;G0 is the green component of all pixel points in block surface image;B0 is the blue component of all pixel points in block surface image;N is the number of forming blocks contained in block surface image;

[0016] Real-time gray value Gray of any shaped block i in the block surface image i The calculation formula is as follows:

[0017] Gray i = 0.299R i + 0.587G i + 0.144B i

[0018] Wherein, R i is the red component of the pixel point included in any shaped block i in the block surface image; G i is the green component of the pixel point included in any shaped block i in the block surface image; B i is the blue component of the pixel point included in any shaped block i in the block surface image;

[0019] The warping block image evaluation module first judges whether the real-time gray value of any shaped block i is greater than the standard gray value. When the real-time gray value of the shaped block i is less than the standard gray value, the shaped block i continues to be printed. Otherwise, the percentage Y i of the real-time gray value of the shaped block i exceeding the standard gray value is calculated by the following formula:

[0020]

[0021] Wherein, Gray0 is the standard gray value, and Gray i is the real-time gray value of any shaped block i.

[0022] The warping block image evaluation module judges the surface warping severity of the corresponding shaped block i according to the calculated percentage Y i , and determines the printing working condition of the shaped block i according to the judgment result.

[0023] Preferably, in the warping block image evaluation module, the judgment standard of the surface warping severity of the shaped block i is that when the percentage is 0% to 25%, it is slight warping; when the percentage is 25% to 50%, it is moderate warping; and when the percentage is 50% to 100%, it is severe warping.

[0024] In the warping block image evaluation module, when the surface warping severity of the shaped block i is slight and moderate warping, the printing continues to be monitored; and when the surface warping severity of the shaped block i is severe warping, the printing is stopped.

[0025] Preferably, the user terminal remote monitoring module comprises a powder laying quality monitoring and powder supply amount self-adaptive compensation module, and the powder laying quality monitoring and powder supply amount self-adaptive compensation module comprises a powder laying image processing module and a powder laying image quality evaluation module, wherein:

[0026] The powder laying image processing module is configured to receive a current powder layer image transmitted by the second high-definition camera, filter and denoise the received current powder layer image, process the filtered and denoised current powder layer image by using a threshold function to obtain a binary gray image, count the number of black pixels in the binary gray image, calculate the total area occupied by the black pixels based on the resolution of the binary gray image, obtain the area S1 of the poor powder laying area in the current powder layer image, and transmit the area S1 to the powder laying image quality evaluation module.

[0027] The powder laying image quality evaluation module is configured to compare whether the area S1 of the poor powder laying area in the current powder layer image exceeds a powder laying quality evaluation set value U, maintain the current powder supply amount unchanged when the judgment result indicates that the area S1 of the poor powder laying area in the current powder layer image does not exceed the powder laying quality evaluation set value U, otherwise, calculate the percentage G of the area S1 of the poor powder laying area in the current powder layer image that exceeds the powder laying quality evaluation set value U, compare the calculated percentage G with a preset value, use 4 times of the powder supply amount when the percentage is between 0% and 30%, use 5 times of the powder supply amount when the percentage is between 30% and 60%, and use 6 times of the powder supply amount when the percentage is between 60% and 100%.

[0028]

[0029] In the formula, d1 is the diameter of the forming cylinder, d2 is the diameter of the powder cylinder, N is the number of the forming blocks, and a and b correspond to the length and width of the forming blocks.

[0030] Preferably, the data acquisition device further comprises a thermal imager.

[0031] The thermal imager is arranged on the powder platform and is configured to acquire the surface heat distribution of each forming block layer by layer and transmit the acquired surface heat distribution of each forming block to the control device.

[0032] The user remote monitoring module generates a heat distribution stereogram in real time according to the received surface heat distribution of each forming block.

[0033] Preferably, the local area network and the wireless WIFI module in the user remote monitoring module are located in the host computer of the printing device, and the user end remote monitoring module acquires the data collected by the first and second cameras and the thermal imager in real time through the local area network.

[0034] Preferably, the first high-definition camera is installed on the powder laying arm near one side of the powder cylinder, and the second high-definition camera is installed on the powder laying arm near one side of the forming cylinder, and the first and second high-definition cameras are symmetrically arranged.

[0035] Preferably, the first and second fixed supports are symmetrically arranged on the powder laying arm, the first high-definition camera is arranged on the first fixed platform, and the first fixed platform is arranged on the first fixed support through the first sliding block; the second high-definition camera is arranged on the second fixed platform, and the second fixed platform is arranged on the second fixed support through the second sliding block.

[0036] The thermal imager is arranged on the powder bed platform through the third fixed support.

[0037] Preferably, the opening and closing switch for controlling the first high-definition camera is further included; the opening and closing switch includes an infrared emission sensor and an infrared receiving device used in cooperation; the infrared receiving device is arranged on the first fixed platform close to the first high-definition camera, and the infrared emission sensor is arranged on the side of the powder bed adjacent to the forming cylinder; when the powder laying mechanism moves from the side of the powder cylinder to the side of the forming cylinder, the infrared receiving device receives the infrared emitted by the infrared emission device on the side of the powder bed, and the first high-definition camera starts the shooting function.

[0038] Another technical purpose of the present application is to provide a laser powder bed fusion additive manufacturing warping deformation intelligent monitoring and autonomous control method, including block warping identification and shutdown control, powder laying quality monitoring and powder supply amount adaptive compensation control; wherein:

[0039] The block warping identification and shutdown control is realized through the following steps:

[0040] Step 101, real-time layer-by-layer acquisition of block surface images containing all formed blocks on the printing substrate;

[0041] Step 102, filtering and denoising processing and block edge strengthening processing are performed on the block surface images collected in step 101;

[0042] Step 103, when the deposition layer number of each formed block reaches the preset layer number, the gray value of the block surface image is calculated based on the processed block surface image in step 102, and the gray value is taken as a standard gray value;

[0043] Step 104, starting from the next deposition layer of the preset layer number, the real-time gray value of each formed block is calculated layer by layer;

[0044] Step 105, whether the real-time gray value of each formed block is greater than the standard gray value is judged, when the judgment result shows that the real-time gray value of the formed block i is less than the standard gray value, the formed block i is continuously printed, otherwise step 106 is entered;

[0045] Step 106, the percentage Y that the real-time gray value of each formed block exceeds the standard gray value is calculated;

[0046] Step 107, based on the percentage Y of the real-time gray value exceeding the standard gray value calculated in step 106, judging the surface warping degree of the corresponding formed block: when the percentage Y is 0%~25%, it is slight warping; when the percentage Y is 25%~50%, it is moderate warping; when the percentage Y is 50%~100%, it is severe warping;

[0047] Step 107, the formed blocks with slight warping and moderate warping continue to be printed and monitored, and the formed blocks with severe warping stop printing;

[0048] The powder laying quality monitoring and powder supply amount self-adaptive compensation regulation are realized through the following steps:

[0049] Step 201, collecting the image of the current powder layer laid by the powder laying mechanism on the powder platform in real time;

[0050] Step 202, performing filtering and noise reduction processing and binarization processing on the image of the current powder layer collected in step 201;

[0051] Step 203, calculating the area S1 of the powder laying quality poor area in the current powder layer image, the powder laying quality evaluation set value U,

[0052]

[0053] In the formula, d1 is the diameter of the forming cylinder, d2 is the diameter of the powder cylinder, N is the number of the formed blocks, a and b correspond to the length and width of the formed blocks; the area S1 of the powder laying quality poor area in the current powder layer image is obtained in the following way: based on the gray-white image of binarization, then counting the number of black pixels in the gray-white image, and calculating the total area occupied by these black pixels based on the resolution of the gray-white image, so as to obtain the area S1 of the powder laying quality poor area in the current powder layer image;

[0054] Step 204, judging whether the area S1 of the powder laying quality poor area in the current powder layer image exceeds the powder laying quality evaluation set value U; when the judgment result shows that the area S1 of the powder laying quality poor area in the current powder layer image is lower than the powder laying quality evaluation set value U, the powder supply amount does not need to be adjusted, otherwise, step 205 is entered;

[0055] Step 205, calculating the percentage G of the area S1 of the powder laying quality poor area in the current powder layer image exceeding the powder laying quality evaluation set value U, and comparing the calculated percentage G with a preset value; when the percentage is 0%~30%, 4 times of the powder supply is adopted; when the percentage is 30%~60%, 5 times of the powder supply is adopted; when the percentage is 60%~100%, 6 times of the powder supply is adopted;

[0056] The percentage G of the area S1 of the powder laying quality poor area in the current powder layer image exceeding the powder laying quality evaluation set value U is calculated by the following formula:

[0057]

[0058] Based on the above technical purposes, compared with the prior art, the present application has the following advantages:

[0059] 1、The laser powder bed fusion additive manufacturing warping deformation intelligent monitoring and self-regulation and control system provided by the present application can solve the problem that in the process of groping for new material process parameters, multiple blocks are printed, the warped blocks cannot be accurately identified, and the subsequent printing of the warped blocks is automatically stopped, and the blocks with good forming quality continue to be printed. The system can quickly identify the blocks with slight surface warping, and on this basis, it can also automatically monitor the influence of the warped blocks on the powder laying quality of the surrounding blocks, and then adaptively adjust the powder supply amount to reduce the influence of the warped blocks on the forming quality of the surrounding blocks.

[0060] 2、The system also adds a user remote monitoring module and a block layer-by-layer heat distribution map acquisition module, multi-directional data acquisition and data cloud platform uploading are performed during printing, researchers do not need to be on duty at the printing site for a long time, non-standard operation of the operating personnel can be reduced, the block surface heat distribution is acquired layer by layer, and a heat accumulation and defect forming model is established, which provides an important reference for process parameter optimization and defect formation mechanism research.

[0061] In general, the system involves functions with strong practicality, especially for the research of new materials and new processes, multiple block printing is often performed, and the installation of the forming quality monitoring system has a smaller range of changes in the internal structure of the printing equipment compared with the existing monitoring technology, so that the system can be easily installed and easily disassembled. BRIEF DESCRIPTION OF DRAWINGS

[0062] Figure 1 The application scenario of the present application is that when multiple blocks are printed, random warping phenomenon occurs.

[0063] Figure 2 The working process of the laser powder bed fusion additive manufacturing warping deformation intelligent monitoring and self-regulation and control system;

[0064] Figure 3 The flowchart for judging the warped blocks;

[0065] Figure 4 The flowchart for judging the powder laying quality;

[0066] Figure 5 The structure schematic diagram of the laser powder bed fusion additive manufacturing warping deformation intelligent monitoring and self-regulation and control device;

[0067] Figure 6 The installation schematic diagram of the warped block identification module and the powder laying quality detection module;

[0068] Figure 7 Schematic diagram of the block body warping module composition

[0069] Figure 8 Schematic diagram of the block body layer-by-layer heat distribution image acquisition module composition

[0070] In the figure: 1, powder cylinder; 2, powder laying arm; 3, flexible scraper; 4, forming cylinder; 5, infrared receiving device; 6, first fixed support; 7, second fixed support; 8, thermal imager; 9, third fixed support; 10, infrared emitting device; 11, powder bed platform; 12, first fixed table; 13, first high-definition camera; 14, first sliding block; 15, second sliding block; 16, second high-definition camera; 17, second fixed table; 18, fill light; 19, first locking bolt; 20, second locking bolt; 21, third fixed table; 22, third sliding block. DETAILED DESCRIPTION

[0071] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. The description of the at least one exemplary embodiment is actually only illustrative, but not as any limitation on the present application and its application or use. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of the present application. Unless otherwise specified, the relative arrangement, expressions and numerical values of the components and steps set forth in these embodiments do not limit the scope of the present application. The technology, methods and devices known to those of ordinary skill in the relevant art can not be discussed in detail, but should be considered as part of the specification when appropriate. In all examples shown and discussed here, any specific value should be interpreted as merely exemplary, rather than as a limitation. Therefore, other examples of the exemplary embodiments can have different values.

[0072] For ease of description, spatial relative terms such as "above," "over," "on the upper surface of," "above," etc., are used here to describe the spatial positional relationship of a device or feature as shown in the figure with other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation besides the orientation of the device as described in the figure. For example, if the device in the figure is inverted, a device described as "above" or "above" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations).

[0073] As shown in the figure Figures 1-8 The workflow of the intelligent monitoring and autonomous control system for warpage deformation in laser powder bed fusion additive manufacturing of the present invention includes the following steps:

[0074] Step S1: Create a multi-block model in the slicing software, assign different process parameters to each block such as laser power, scanning speed, and scanning strategy, and then import the slicing data of the blocks into the printing equipment, such as... Figure 1 As shown.

[0075] Step S2: Install the new substrate and manually level it. Pour metal powder into the powder cylinder, replace the scraper, and adjust the powder spreading device to achieve good powder spreading effect. Then, argon gas is introduced into the sealed forming cavity for gas purging. The contents involved in this step include, for example, Figure 2 The workflow diagram shown is shown below.

[0076] Step S3: After completing the above preparations, the block printing begins. The block warpage identification and shutdown module, the toner spreading quality monitoring and adaptive compensation module, the block layer-by-layer thermal distribution data acquisition module, and the remote monitoring module all begin operation. The workflow of each module is as follows: Figure 2 As shown.

[0077] Step S4: The block warpage recognition and shutdown module begins real-time monitoring of the surface morphology of each block. Four supplementary lights 18 located below the first fixed platform 12 are turned on, making the image captured by the first high-definition camera 13 clearer. If the image recognition program detects a warped block, it combines the block slice model to accurately locate the block's position on the substrate. Then, the program determines whether to continue printing the block based on whether the warpage exceeds a threshold. If it exceeds the threshold, printing of the block stops; if it does not exceed the threshold, printing continues. The warpage recognition system continues to monitor the block, while other well-formed blocks continue printing. The detailed workflow is as follows: Figure 3The first high-definition camera is installed perpendicularly to the powder bed, which can avoid the inaccurate defect identification caused by the installation of the first high-definition camera at a certain inclined angle with the powder bed, resulting in the wrong decision of the program, because the metal luster of the block horizontal section at different angles and different areas in the printing process is inconsistent, which will cause errors in visual dynamic identification. The first high-definition camera is installed on the first fixed support above the powder laying wall through the first fixed table, and the camera can be adjusted to the appropriate height according to the size of the printed block to accurately obtain the surface forming quality of the block. That is, the first fixed table is assembled to the first fixed support through the first sliding block, so as to realize the lifting adjustment of the first high-definition camera.

[0078] When the powder laying wall moves to the left to a certain position, the first high-definition camera starts the camera function to continuously photograph the surface of the block, and in the camera process, the image recognition algorithm is matched to judge whether the surface of each formed block is warped in real time. If the warping degree is serious, the identification program will accurately position the position of the warped block on the substrate in combination with the position of the warped block in the real-time picture of the printing and the slice model of all blocks, and automatically stop the printing work of the warped block, and the other formed blocks continue to print.

[0079] As can be seen, in the present application, the first high-definition camera is mainly used for photographing the images of all formed blocks on the formed substrate. In other words, when the first high-definition camera starts the photographing function, the view field thereof is the formed substrate, and the first high-definition camera can clearly photograph the images of all formed blocks on the formed substrate and transmit the photographed images to the data center of the user terminal remote monitoring module.

[0080] In the present application, the position of the first high-definition camera when starting the camera function is controlled by the on-off switch, which includes an infrared ray emitting sensor and an infrared ray receiving device used in combination. The infrared ray receiving device is arranged on the first fixed table close to the first high-definition camera, and the infrared ray emitting sensor is installed on the side of the powder bed adjacent to the forming cylinder. When the powder laying mechanism moves from one side of the powder cylinder to one side of the forming cylinder, the infrared ray receiving device receives the infrared ray emitted by the infrared ray emitting device on the side of the powder bed, and the first high-definition camera starts the photographing function. The center axis of the installation position of the infrared ray emitting sensor on the side of the powder bed is tangent to the edge of the circular or square forming cylinder. Taking the circular forming cylinder as an example, when the powder laying wall moves to the left to lay powder, the infrared ray receiving device located below the camera platform receives the infrared ray emitted by the infrared ray emitting device on the side of the powder bed, and the camera starts the camera function.

[0081] The user terminal remote monitoring module analyzes the frame-by-frame block surface image captured by the first high-definition camera. Since the flatness and edge profile deformation of different warped blocks are different, the gray value calculated from the collected image will be different, so the degree of block warping can be judged by the gray value. When the block is printed to 20 layers (20 layers is a value based on experience, and in fact, this value can not be selected), the gray value calculated from the collected block surface image after filtering and removing the powder bed background is used as the standard gray value. When the percentage exceeds the standard gray value, the percentage is 0% to 25%, which is slight warping, the percentage is 25% to 50%, which is moderate warping, and the percentage is 50% to 100%, which is severe warping. For blocks with slight and moderate warping, continue to print and monitor, and stop printing for blocks with severe warping.

[0082] In other words, the user terminal remote monitoring module according to the application judges whether the surface warping degree of each formed block exceeds the preset range according to the block surface image fed back by the first high-definition camera, and controls the printing conditions of the corresponding formed block according to the judgment result; including a block warping identification and shutdown module; the block warping identification and shutdown module includes a warped block image processing module and a warped block image evaluation module; wherein:

[0083] The warped block image processing module is used to receive the block surface image fed back by the first high-definition camera and filter and denoise the received block surface image frame by frame. The standard gray value is calculated when the deposition layer number of each formed block reaches the preset layer number. The real-time gray value of each formed block is calculated for each deposition layer after the preset layer number, and the percentage Y of the real-time gray value to the standard gray value is uploaded to the warped block image evaluation module; wherein:

[0084] The standard gray value Gray0 is calculated as follows:

[0085] Gray0=(0.299R0+0.587G0+0.144B0) / N

[0086] Wherein, R0 is the red component of all pixel points in the block surface image; G0 is the green component of all pixel points in the block surface image; B0 is the blue component of all pixel points in the block surface image; N is the number of formed blocks contained in the block surface image;

[0087] The real-time gray value Gray of any formed block i in the block surface image is calculated as follows: i The calculation formula is as follows:

[0088] Gray i =0.299R i+0.587G i +0.144B i

[0089] wherein, R i is the red component of any pixel point included in the surface image of the shaped block i; G i is the green component of any pixel point included in the surface image of the shaped block i; B i is the blue component of any pixel point included in the surface image of the shaped block i;

[0090] The warped block image evaluation module first judges whether the real-time gray value of any shaped block i is greater than the standard gray value. When the real-time gray value of the shaped block i is less than the standard gray value, the shaped block i continues to be printed. Otherwise, the percentage Y i of the real-time gray value of the shaped block i exceeding the standard gray value is calculated by the following formula:

[0091]

[0092] wherein, Gray0 is the standard gray value, Gray i is the real-time gray value of any shaped block i.

[0093] The warped block image evaluation module judges the surface warping severity of the corresponding shaped block i according to the calculated percentage Y i , and determines the printing working condition of the shaped block i according to the judgment result.

[0094] In the warped block image evaluation module, the evaluation standard of the surface warping severity of the shaped block i is that when the percentage is at 0% to 25%, it is slight warping; when the percentage is at 25% to 50%, it is moderate warping; and when the percentage is at 50% to 100%, it is severe warping. In the warped block image evaluation module, when the surface warping severity of the shaped block i is slight and moderate warping, the printing continues to be monitored. When the surface warping severity of the shaped block i is severe warping, the printing is stopped.

[0095] Step S5: The powder laying quality monitoring and self-adaptive compensation module monitors the powder laying quality of the blocks around the warped block in real time, and reduces the influence of the warped block on the powder laying quality of the surrounding blocks by automatically adjusting the powder supply amount. When the warped block is identified in step S4, the four light compensation lamps located below the second fixed table 17 are turned on, which also makes the image captured by the second high-definition camera 16 clearer. The second high-definition camera moves with the powder laying wall 2 from right to left, and the image recognition program in the user terminal remote monitoring module monitors the flatness of the powder bed surface and the powder laying quality of the warped block and its surrounding blocks in real time, and autonomously selects the appropriate powder supply amount according to the powder laying quality to compensate for the powder supply. If the powder laying of the warped block and its surrounding blocks is uniform in subsequent monitoring, the powder supply amount returns to normal. The detailed working process is shown in FIG. 8. Figure 4

[0096] During the imaging process, the second high-definition camera cooperates with the image recognition algorithm to judge the defects left after the scraper scrapes the surface powder of the powder cylinder and the size of the block surface metal exposed area during the powder laying process. If the exposed area is too large, the powder laying compensation program will be started. Generally, 3 times of powder supply is used during printing, that is, the forming cylinder is lowered by 20 pm and the powder cylinder is raised by 60 pm. In order to improve the powder laying quality, the powder supply amount in the powder laying compensation program is set to 4, 5, and 6 times of powder supply. The program will automatically set different powder supply amounts for compensation according to the size of the block surface metal exposed area. If the powder laying quality is improved, the compensation program will gradually reduce the powder supply amount until it returns to the initial 3 times of powder supply, so as to prevent the remaining powder from being too little to complete the overall printing.

[0097] The user terminal remote monitoring module analyzes the frame-by-frame powder laying images captured by the second camera to obtain the uneven powder laying area within the powder laying image range, which includes the block surface exposure after powder laying and the flatness of the powder bed. When the uneven powder laying area is below the set value, the powder supply amount does not need to be adjusted; when the uneven powder laying area is above or equal to the set value, the powder supply amount needs to be adjusted, and the percentage of the uneven powder laying area exceeding the set value is calculated. When the percentage is between 0% and 30%, 4 times of powder supply is used; when the percentage is between 30% and 60%, 5 times of powder supply is used; and when the percentage is between 60% and 100%, 6 times of powder supply is used. Specifically, first, the powder laying image is denoised using a filtering denoising method, and the threshold function is used to process the obtained powder laying image to obtain a binary gray image. Then, the pixels in the image are calculated, and the area of the black pixel region in the image is the uneven powder laying area. The image is binarized to convert it into a gray image containing only black and white colors. The number of black pixels in the image is counted, and the total area occupied by these black pixels is calculated based on the resolution of the image. This area represents the size of the uneven powder laying area in the image.

[0098] ​In other words, in the present application, the user terminal remote monitoring module evaluates the powder laying quality of the current powder layer according to the current powder layer image transmitted by the second high-definition camera, and determines the powder supply amount of the powder cylinder according to the evaluation result.

[0099] The powder laying image processing module is configured to receive the current powder layer image transmitted by the second high-definition camera, filter and denoise the received current powder layer image, process the filtered and denoised current powder layer image by using a threshold function to obtain a binary gray image, count the number of black pixels in the binary gray image, calculate the total area occupied by the black pixels based on the resolution of the binary gray image, obtain the area S1 of the region with poor powder laying quality in the current powder layer image, and transmit the area S1 to the powder laying image quality evaluation module.

[0100] The powder laying image quality evaluation module is configured to compare whether the area S1 of the region with poor powder laying quality in the current powder layer image exceeds a powder laying quality evaluation set value U.

[0101]

[0102] In the formula, d1 is the diameter of the forming cylinder, d2 is the diameter of the powder cylinder, N is the number of the forming blocks, and a and b correspond to the length and width of the forming blocks.

[0103] As can be seen, in the present application, the warping recognition and shutdown module and the powder laying quality monitoring and adaptive compensation module are in a linkage mode, after the former module recognizes a warped block, if the warping degree is too large, the printing work of the warped block is immediately stopped, if the warping degree is relatively small, the block can continue to be printed, because the warping degree can be reduced by subsequent powder laying quality improvement, after the warped block is recognized, the powder laying quality monitoring and adaptive compensation module recognizes the powder laying quality of the blocks around the warped block, starts a powder laying compensation program to increase the powder supply amount until the surfaces of the blocks around the warped block are monitored to be uniform, and the powder supply amount is restored to the initial powder supply amount.

[0104] Step S6: The layer-by-layer heat distribution data acquisition module acquires the heat distribution image of the block surface in real time, the thermal imager 8 starts to work at the beginning of printing, and the heat distribution image of the surface of each block is acquired layer by layer. Different process parameters are different, and the heat distribution is also different. The heat distribution image, the color depth represents the heat level, the darker the color, the more serious the heat accumulation, and the temperature value in the local area with the same color is displayed, and then the background program constructs a three-dimensional heat distribution model of the block according to the collected data, which is beneficial to researchers to study the defect formation mechanism and provide reference for process parameter optimization. The core component is the thermal imager, which is installed above the bracket on the left side of the forming cylinder. The third platform for fixing the thermal imager is adjusted to the appropriate inclination angle by rotating up and down, and the height of the thermal imager can also be adjusted by moving the slider embedded in the third fixed support up and down.

[0105] The image data collected by the warping identification and powder laying quality monitoring and the heat distribution data collected by the thermal imager layer by layer are synchronized to the data processing center, and the user only needs to remotely log in the program to observe the block printing quality and equipment state in real time.

[0106] The local area network and wireless WIFI module in the user remote monitoring module are located in the host computer of the printing equipment. The local area network and wireless WIFI module are used to transmit the large amount of video images, heat distribution data and printing equipment running state acquired in real time to the data processing center, and after analysis and judgment, the key data are transmitted to the mobile terminal such as mobile phone in small batches through wireless WIFI.

[0107] Step S7: The user remote monitoring module starts to work at the beginning of printing, and the images captured by the high-definition camera and the thermal imager are uploaded to the data processing center in real time during the printing process. The researchers can remotely observe the printing process by logging in the user terminal program. If the fault alarm signal appears during the printing process, it will be immediately uploaded to the user terminal program, so that the long-term on-site duty problem can be solved.

[0108] Step S8: After printing, the sample is slowly cooled to room temperature in the forming cabin, and then the sample is taken out for subsequent processing.

[0109] The laser powder bed fusion additive manufacturing warping deformation intelligent monitoring and self-regulating system can monitor the warping block in real time and automatically shut down the block with large warping degree, and the blocks with perfect forming continue to be printed. Through the powder laying self-adaptive compensation program, the influence of the warping block on the surrounding blocks is reduced. The user can remotely monitor the printing process without long-term on-site duty. The block surface heat distribution data acquired layer by layer can provide reference for the next printing parameter adjustment and the study of the defect formation mechanism caused by heat accumulation.

[0110] The application can practically solve the practical problems of bulk printing of various process parameters during new material process development.

[0111] The application will be further described in detail below in combination with examples:

[0112] Example 1

[0113] Taking the process parameters of printing 98wt.% W-1.5wt.% TiC-0.5wt.% Y2O3 bulk by a single laser device as an example.

[0114] Step S1: Establish the bulk model in the slicing software and give each bulk corresponding process parameters, the bulk size is 8mmx8mmx6mm, the laser power interval is 200W-450W, the scanning speed interval is 200mm / s-600mm / s, the powder layer thickness is 25μm, the interlayer rotation is 67°, the chessboard scanning strategy, and then import the slicing data into the printing device.

[0115] Step S2: Install a new substrate and perform manual leveling, pour metal powder into the powder cylinder, replace the new scraper and debug the powder laying device to have good powder laying effect, then introduce argon into the closed forming cavity for gas washing operation until the oxygen content inside the forming cavity is less than 500ppm.

[0116] Step S3: After the above preparation work is completed, the substrate is first scanned for 3 layers, then the bulk printing starts, the warping deformation intelligent monitoring and self-regulating system also starts to run, the bulk warping identification and shutdown module starts to monitor the surface morphology of each bulk in real time, during the printing of multiple bulks, the real-time collected bulk surface images are analyzed, the standard gray value Gray1 of each bulk is calculated as 100, and the real-time gray value Gray2 and the percentage Y are calculated, it is judged whether Gray2 is greater than Gray1, if less, continue to print the bulk, if greater, according to the size of the percentage Y, select to continue printing or stop printing the warped bulk, the powder laying quality monitoring and self-adaptive compensation module starts to monitor the powder laying quality of the bulk around the warped bulk in real time and reduces the influence of the warped bulk on the powder laying quality of the surrounding bulk by automatically adjusting the powder supply amount, the specific process is that the real-time collected powder laying quality images are analyzed, the powder laying quality evaluation value U is calculated as 42.25mm 2 and the real-time uneven powder laying area S1 and the percentage G are calculated, it is judged whether the uneven powder laying area exceeds the set value, if it exceeds, the corresponding powder supply amount is selected according to the exceeding range, if it does not exceed, the initial powder supply amount is maintained, the layer-by-layer heat distribution data acquisition module acquires the bulk surface heat distribution image in real time, and the data collected during the printing process is uploaded to the data processing center in real time.

[0117] Step S4: Check if the network connected by the printing device is stable, and if the user terminal program can view the real-time picture during the printing process. After completing the above steps, the researcher leaves the laboratory to remotely monitor the printing process.

[0118] Step S5: When the printing is completed, the device will send a printing completion instruction to the user terminal. The researcher only needs to wait for the sample to slowly cool to room temperature inside the forming cabin, take out the sample, and then proceed with subsequent processing.

[0119] The laser powder bed fusion additive manufacturing warping deformation intelligent monitoring and autonomous control system runs smoothly in the single laser forming 98wt.% W-1.5wt.% TiC-0.5wt.% Y2O3 block process. Eight blocks are found to have severe warping, two blocks have moderate warping, four blocks have slight warping, and the remaining blocks have no warping. The severely warped blocks are directly stopped for subsequent printing. The moderate and slight warping blocks have reduced warping degree after autonomous control of powder supply, and the warped blocks have reduced impact on surrounding blocks. The heat accumulation distribution map collected layer by layer provides a certain reference for the warping and crack formation mechanism of single laser formed tungsten alloy blocks. Without manual attendance during the entire printing process, the intelligent degree of the additive manufacturing process is significantly improved.

[0120] Example Two

[0121] The double laser following printing device is used to form 98wt.% W-1.5wt.% TiC-0.5wt.% Y2O3 blocks, and the process parameters of this new material are taken as an example.

[0122] Step S1: The researcher informs the enterprise engineer of the printing scheme. The engineer establishes a block model in the slicing software according to the printing scheme and assigns corresponding process parameters to each block. The block size is 10mm x 10mm x 8mm, the laser power range is 100W-250W, the scanning speed range is 200mm / s-400mm / s, the powder layer thickness is 25μm, the interlayer rotation is 67°, and the chessboard scanning strategy is used. Then, the slicing data is imported into the printing device.

[0123] Step S2: Install a new substrate and perform manual leveling. Pour metal powder into the powder cylinder, replace the new scraper and debug the powder laying device to have good powder laying effect. Then, introduce argon into the sealed forming cavity for gas washing operation until the oxygen content inside the forming cavity is less than 500ppm.

[0124] Step S3: After the above preparations are completed, the substrate is first scanned for 3 layers, then bulk printing begins, and the intelligent monitoring and autonomous control system for warping deformation also begins to operate. The bulk warping identification and shutdown module begins to monitor the surface morphology of each bulk in real time. During the printing of multiple bulk bodies, the real-time collected bulk surface images are analyzed, the standard gray value Gray1 of each bulk body is calculated as 120, and the real-time gray value Gray2 and the percentage Y are calculated. Determine whether Gray2 is greater than Gray1. If it is less than, continue printing the bulk body. If it is greater than, according to the size of the percentage Y, select to continue printing or stop printing the warped bulk body. The powder laying quality monitoring and adaptive compensation module begins to monitor the powder laying quality of the bulk body around the warped bulk body and reduces the influence of the warped bulk body on the powder laying quality of the surrounding bulk body by automatically adjusting the powder supply amount. The specific process is to analyze the real-time collected powder laying quality images, calculate the powder laying quality evaluation value U as 72.25 mm 2 and calculate the real-time uneven powder laying area S1 and the percentage G. Determine whether the uneven powder laying area exceeds the set value. If it exceeds, select the corresponding powder supply amount according to the exceeding range. If it does not exceed, maintain the initial powder supply amount. The layer-by-layer heat distribution data acquisition module acquires the bulk surface heat distribution images in real time. The data collected during the printing process is uploaded to the data processing center in real time.

[0125] Step S4: The engineer checks whether the network connected to the printing equipment is stable, and informs the researcher whether the user end program can view the real-time picture during the printing process. After adjustment, the researcher can remotely monitor the printing process. If unexpected situations occur during the printing process, such as the printing equipment detecting insufficient cavity protection gas, the printing equipment will immediately alarm and upload the problem instructions to the user end. After receiving the instructions, the researcher immediately contacts the engineer to handle the problem on site.

[0126] The intelligent monitoring and autonomous control system for warping deformation in laser powder bed fusion additive manufacturing runs smoothly during the double laser forming of 98wt.% W-1.5wt.% TiC-0.5wt.% Y2O3 bulk bodies. Five bulk bodies are found to have severe warping, four bulk bodies have moderate warping, and six bulk bodies have slight warping. The remaining bulk bodies do not have warping phenomenon. The severely warped bulk bodies are directly stopped for subsequent printing. The moderately and slightly warped bulk bodies have reduced warping degree after autonomous control of the powder supply amount. The influence of the warped bulk body on the surrounding bulk body is reduced. The layer-by-layer collected heat accumulation distribution map provides a certain reference for the study of the warping and crack formation mechanism of double laser formed tungsten alloy bulk bodies. Real-time monitoring of the printing process using this system can capture unexpected situations that occur during the printing process in all directions, avoiding the omission of details by manual supervision.

[0127] Step S5: When the printing is completed, the device sends a printing completion instruction to the user end. The researchers only need to wait for the sample to slowly cool to room temperature inside the forming cabin, and then contact the engineer to take out the sample for subsequent processing.

[0128] Those skilled in the art will easily understand that the above description is only the preferred embodiment of the present application, and is not used to limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A laser powder bed fusion additive manufacturing warping deformation intelligent monitoring and autonomous regulation system, comprising a powder platform, a forming cylinder, a powder cylinder and a powder laying mechanism; characterized in that, It also comprises a data acquisition device and a user terminal remote monitoring module, the data acquisition device comprises a first and a second high-definition camera, wherein: The first high-definition camera is installed on the powder laying mechanism and is used to take pictures of the surface of the block including all the forming blocks layer by layer, and can transmit the pictures to the user terminal remote monitoring module; The second high-definition camera is installed on the powder laying mechanism and is used to take pictures of the current powder layer on the powder platform, and can transmit the pictures to the user terminal remote monitoring module; The user terminal remote monitoring module judges whether the surface warping degree of each forming block exceeds the preset range according to the block surface image feedback by the first high-definition camera, and controls the printing conditions of the corresponding forming block according to the judgment result; The user terminal remote monitoring module evaluates the powder laying quality of the current powder layer according to the current powder layer image transmitted by the second high-definition camera, and determines the powder supply amount of the powder cylinder according to the evaluation result; The user terminal remote monitoring module comprises a block warping identification and shutdown module, and the block warping identification and shutdown module comprises a warping block image processing module and a warping block image evaluation module, wherein: The warping block image processing module is used for receiving the block surface image fed back by the first high-definition camera, filtering and denoising the received block surface image frame by frame, calculating the standard gray value when the deposition layers of each formed block reach the preset number of layers, calculating the real-time gray value of each formed block one by one for each deposition layer after the preset number of layers, and calculating the percentage of the real-time gray value in the standard gray value to the warping block image evaluation module; wherein: Standard gray value The calculation formula is as follows: ； wherein, R is a red component of all pixel points in the block surface image; G is a green component of all pixel points in the block surface image; B is a blue component of all pixel points in the block surface image; N is a number of the formed blocks contained in the block surface image; any shaped block in the block surface image real-time gray value The calculation formula is as follows: ； in, For any shaped block in the block surface image The red component of the included pixels; For any shaped block in the block surface image The green component of the included pixels; For any shaped block in the block surface image The blue component of the included pixels; The warped block image evaluation module first judges any formed block. Whether the real-time grayscale value is greater than the standard grayscale value, when the formed block If the real-time grayscale value is less than the standard grayscale value, continue printing the formed block. Conversely, the shaped block is calculated using the following formula. The percentage of real-time grayscale values ​​that exceed the standard grayscale values : ； wherein, is a standard gray value, is a real-time gray value of any shaped block . The warped block image evaluation module evaluates the warped block based on the calculated percentage. Determine the corresponding formed block The severity of surface warping was assessed, and the shaped block was determined based on the assessment results. The printing conditions.

2. The laser powder bed fusion additive manufacturing warping deformation intelligent monitoring and autonomous regulation system according to claim 1, characterized in that, In the warping block image evaluation module, the evaluation standard for the surface warping severity of the shaped block is that when the percentage is 0%~25%, it is slight warping, when the percentage is 25%~50%, it is moderate warping, and when the percentage is 50%~100%, it is severe warping. In the warped block image evaluation module, when the surface warping severity of the shaped block is mild and moderate warping, printing continues and continues to be monitored; when the surface warping severity of the shaped block is severe warping, printing is stopped.

3. The laser powder bed fusion additive manufacturing warping deformation intelligent monitoring and autonomous regulation system according to claim 1, characterized in that, The user terminal remote monitoring module comprises a powder laying quality monitoring and powder supply amount self-adaptive compensation module, and the powder laying quality monitoring and powder supply amount self-adaptive compensation module comprises a powder laying image processing module and a powder laying image quality evaluation module, wherein: The powder laying image processing module is configured to receive a current powder layer image transmitted by the second high-definition camera, filter and denoise the received current powder layer image, process the filtered and denoised current powder layer image by using a threshold function to obtain a binary grayscale image, count the number of black pixels in the binary grayscale image, and calculate the total area occupied by the black pixels based on the resolution of the binary grayscale image, so as to obtain the area of the region with poor powder laying quality in the current powder layer image , and transmit the area to the powder laying image quality evaluation module. The powder spreading image quality assessment module is used to compare the area of ​​poor powder spreading quality in the current powder layer image. Does it exceed the set value for evaluating the quality of powder application? When the judgment result indicates the area of ​​the region with poor powder spreading quality in the current powder layer image. It did not exceed the set value for powder spreading quality evaluation. If the current powder supply remains unchanged, then calculate the area of ​​the region with poor powder spreading quality in the current powder layer image. Exceeding the set value for powder coating quality evaluation percentage and the calculated percentage Compared with preset values, when the percentage is between 0% and 30%, a 4x toner supply is used; when the percentage is between 30% and 60%, a 5x toner supply is used; and when the percentage is between 60% and 100%, a 6x toner supply is used. ； ； ； In the formula: is the diameter of the forming cylinder, is the diameter of the powder cylinder, is the number of the forming blocks, , correspond to the length and width of the forming blocks.

4. The laser powder bed fusion additive manufacturing warping deformation intelligent monitoring and autonomous regulation system according to claim 1, characterized in that, The data acquisition device further comprises a thermal imager; The thermal imager is installed on the powder platform and is used to collect the surface heat distribution of each forming block layer by layer, and can transmit the collected surface heat distribution of each forming block to the control device; The user terminal remote monitoring module generates a heat distribution stereogram in real time according to the received surface heat distribution of each forming block.

5. The laser powder bed fusion additive manufacturing warping deformation intelligent monitoring and autonomous regulation system according to claim 4, characterized in that, The local area network and wireless WIFI module in the user terminal remote monitoring module are located in the host computer of the printing equipment, and the user terminal remote monitoring module obtains the data collected by the first and second cameras and the thermal imager in real time through the local area network.

6. The laser powder bed fusion additive manufacturing warping deformation intelligent monitoring and autonomous regulation system according to claim 5, characterized in that, The first high-definition camera is installed on the powder laying arm near the side of the powder cylinder, and the second high-definition camera is installed on the powder laying arm near the side of the forming cylinder, and the first and second high-definition cameras are symmetrically arranged.

7. The laser powder bed fusion additive manufacturing warping deformation intelligent monitoring and autonomous regulation system according to claim 6, characterized in that, The first and second fixed supports are symmetrically installed on the powder laying arm, the first high-definition camera is installed on the first fixed table, and the first fixed table is telescopically installed on the first fixed support through the first sliding block; the second high-definition camera is installed on the second fixed table, and the second fixed table is telescopically installed on the second fixed support through the second sliding block; The thermal imager is installed on the powder bed platform through the third fixed support.

8. The laser powder bed fusion additive manufacturing warping deformation intelligent monitoring and autonomous regulation system according to claim 7, characterized in that, Also include a control first high-definition camera on-off switch, the on-off switch includes the matching use infrared ray emission sensor and infrared receiving device, the infrared receiving device is close to the first high-definition camera and is arranged on the first fixed table, and the infrared ray emission sensor is installed on the powder bed side adjacent to the forming cylinder, when the powder laying mechanism moves from the side of the powder cylinder to the side of the forming cylinder, the infrared receiving device receives the infrared ray emitted by the infrared ray emission device on the powder bed side, the first high-definition camera starts the shooting function. 9.A method for monitoring and autonomously regulating warping deformation in laser powder bed fusion additive manufacturing, characterized in that, It includes block body warping identification and shutdown control, powder laying quality monitoring and powder supply amount adaptive compensation regulation and control, wherein: The block body warping identification and shutdown control is realized by the following steps: Step 101, real-time layer-by-layer acquisition of block surface image containing all formed blocks on the printing substrate; Step 102, filtering and denoising processing, block edge strengthening processing are performed on the block surface image collected in step 101; Step 103, when the deposition layer number of each formed block reaches the preset layer number, the gray value of the block surface image is calculated based on the processed block surface image in step 102, which is used as the standard gray value; Step 104, starting from the next deposition layer of the preset layer number, the real-time gray value of each formed block is calculated layer by layer; Step 105, judge whether the real-time gray value of each formed block is greater than the standard gray value, when the judgment result shows that the real-time gray value of the formed block i is less than the standard gray value, continue to print the formed block i, otherwise enter step 106; Step 106, calculate the percentage Y of the real-time gray value of each formed block exceeding the standard gray value; Step 107, based on the percentage Y of the real-time gray value exceeding the standard gray value calculated in step 106, judge the surface warping degree of the corresponding formed block: when the percentage Y is 0%~25%, it is slight warping, when the percentage Y is 25%~50%, it is moderate warping, when the percentage Y is 50%~100%, it is severe warping; Step 107, the formed blocks with slight warping and moderate warping continue to print and continue to monitor, and the formed blocks with severe warping stop printing; The powder laying quality monitoring and powder supply amount adaptive compensation regulation and control are realized by the following steps: Step 201, real-time acquisition of the image of the current powder layer laid by the powder laying mechanism on the powder platform; Step 202, filtering and denoising processing, binarization processing are performed on the image of the current powder layer collected in step 201; Step 203, calculate the area of the region with poor powder spreading quality in the current powder layer image respectively , powder spreading quality evaluation set value , ； ； In the formula: is the diameter of the forming cylinder, is the diameter of the powder cylinder, is the number of the forming blocks, , correspond to the length and width of the forming blocks; the area of the region with poor powder laying quality in the current powder layer image The area of the region with poor powder laying quality in the current powder layer image is obtained in the following manner: based on the gray-white image after binarization, then counting the number of black pixels in the gray-white image, and calculating the total area occupied by these black pixels based on the resolution of the gray-white image, that is, the area of the region with poor powder laying quality in the current powder layer image ; Step 204, judging the area of the region with poor powder spreading quality in the current powder layer image whether the area exceeds the powder spreading quality evaluation setting value When the judgment result indicates that the area of the region with poor powder spreading quality in the current powder layer image is lower than the powder spreading quality evaluation setting value , the powder supply amount does not need to be adjusted, otherwise, step 205 is entered. Step 205: Calculate the area of ​​the region with poor powder spreading quality in the current powder layer image. Exceeding the set value for powder coating quality evaluation percentage and the calculated percentage Compared with the preset value, when the percentage is between 0% and 30%, use 4 times the powder supply; when the percentage is between 30% and 60%, use 5 times the powder supply; when the percentage is between 60% and 100%, use 6 times the powder supply. Area of regions in the current powder layer image where the powder lay quality is poor Percentage of the area that exceeds the powder lay quality evaluation set value is calculated by the following equation:​ 。

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