Method for monitoring forming quality of additive manufacturing workpiece

Abstract

The invention relates to a method for monitoring the forming quality of an additive manufacturing workpiece, which is used for solving the technical problem of low accuracy in the existing monitoring mode, and comprises the following steps: printing a workpiece layer by layer; printing operation is paused after a fixed number of layers are printed, and powder existing on the workpiece is removed; a ray emitter and a ray receiver are used for conducting CT scanning on the workpiece; performing image reconstruction on the acquired CT data; and analyzing according to the reconstructed image, and deciding whether to continue printing or stop processing. According to the method, through a CT detection link, an image reconstruction stage and image analysis, internal comprehensive information can be obtained by penetrating through a workpiece, and tiny defects are accurately captured; the CT data is converted into a visual and clear fault and three-dimensional image by means of an algorithm, information such as the shape, the position and the size of the defect is presented, the visualization and the interpretability of the data are improved, human judgment errors are reduced, and the accuracy of monitoring data is integrally improved.

Description

Technical Field

[0001] This invention relates to the field of additive manufacturing technology, and in particular to a method for monitoring the forming quality of additively manufactured workpieces. Background Technology

[0002] With its unique advantages, additive manufacturing technology closely integrates design and manufacturing processes, achieving highly integrated production. It plays an irreplaceable and vital role in key fields such as aerospace and biomedicine, which have stringent requirements for the manufacture of complex components.

[0003] Currently, selective laser melting (SLM) is the mainstream technology in the field of additive manufacturing. It uses a high-energy laser beam to melt metal powder layer by layer, and can successfully process difficult-to-machine materials such as titanium alloys and nickel-based high-temperature alloys. The resulting workpieces have excellent density and mechanical properties that can meet the standards of forgings. However, in terms of monitoring the forming process, existing technologies are mostly based on statistical models to perform qualitative analysis of defects, which makes it difficult to accurately quantify the size and location of defects, and the accuracy of monitoring data is very low. Summary of the Invention

[0004] The purpose of this invention is to provide a method for monitoring the forming quality of additively manufactured workpieces, so as to solve the technical problem of low accuracy in existing monitoring methods.

[0005] The objective of this invention is mainly achieved through the following technical solutions:

[0006] A method for monitoring the forming quality of additively manufactured workpieces includes:

[0007] Step 1: Print the workpiece layer by layer;

[0008] Step 2: After printing a fixed number of layers, pause the printing job and remove any powder from the workpiece;

[0009] Step 3: Perform a CT scan on the workpiece using a radiation emitter and a radiation receiver;

[0010] Step 4: Reconstruct the acquired CT data to generate tomographic images and 3D images of the formed parts of the workpiece.

[0011] Step 5: Analyze the reconstructed image to identify internal defects, calculate dimensional accuracy, and decide whether to continue printing or stop processing.

[0012] Furthermore, in step 3, during the CT scan, the printing cylinder rotates via a rotating platform at the bottom to meet the motion requirements of the CT scan.

[0013] Furthermore, in step 2, the powder present on the workpiece is removed by blowing and / or sucking powder.

[0014] Furthermore, step 1 also includes the step of injecting a protective gas into the stereolithography assembly to prevent the metal powder from oxidizing during the printing process.

[0015] Furthermore, in step 2, the printing job is paused after printing 20-50 layers.

[0016] Furthermore, in step 2, after printing stops, the printing cylinder rises, blowing away the powder above the workpiece and exposing the upper surface of the printed workpiece.

[0017] Furthermore, in step 3, after the blowing and suction mechanism removes the unmelted powder covering the printed workpiece portion, the printing cylinder rotates, and the X-ray emitter and X-ray receiver complete the imaging scan of the printed workpiece portion.

[0018] Furthermore, in step 4, a three-dimensional internal structure model of the printed part of the workpiece is reconstructed based on the two-dimensional projection images of the printed part of the workpiece from different angles.

[0019] Furthermore, in step 5, if a repairable defect is found, return to step 2, adjust subsequent printing parameters to compensate, and continue printing.

[0020] Furthermore, in step 5, if an irreparable defect is found, the printing process is stopped.

[0021] In one or more technical solutions provided in the exemplary embodiments of the present invention, at least one of the following beneficial effects can be achieved.

[0022] (1) In the technical solution of the method for monitoring the forming quality of additive manufacturing workpieces in this invention, during the detection stage, the printing is paused after a fixed number of layers are printed, and a CT scan is performed using a X-ray emitter and receiver. This method can penetrate the workpiece to obtain comprehensive internal information and accurately capture minute defects. Compared with the traditional qualitative judgment that relies on statistical models, it improves the accuracy of the data. In the image reconstruction stage, the CT data is transformed into intuitive and clear tomographic and three-dimensional images with the help of algorithms, so that information such as the shape, location and size of defects can be presented, which improves the visualization and interpretability of the data and reduces human judgment errors. Finally, based on the reconstructed image, defects are analyzed, dimensional accuracy is calculated and decisions are made quickly, which can reflect the changes in workpiece quality during the printing process in a timely manner, avoid misjudgment or omission caused by data lag, and ensure that the monitoring data truly and accurately reflects the current printing status. Thus, it provides reliable support for the adjustment of the printing process and improves the overall accuracy of the monitoring data.

[0023] (2) In the technical solution of the method for monitoring the forming quality of additive manufacturing workpieces in this invention, the precise three-dimensional geometric data obtained by CT scanning provides a framework for constructing a digital model of internal structural components, allowing the thermodynamic calculation model to operate based on the real structure, improving the accuracy of evaluation, and also assisting in locating the approximate location of potential problems. When combined with the residual stress distribution, the geometric feature areas that are prone to deformation or cracking can be identified.

[0024] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from the description and drawings, which are particularly pointed out. Attached Figure Description

[0025] The accompanying drawings illustrate exemplary embodiments of the invention and, together with the description thereof, serve to explain the principles of the invention. These drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification.

[0026] Figure 1 This is a flowchart illustrating the method for monitoring the forming quality of additively manufactured workpieces in an embodiment of the present invention.

[0027] Figure 2 This is a flowchart illustrating step 5 in an embodiment of the present invention;

[0028] Figure 3 This is a schematic diagram of the thermodynamic model calculation process in an embodiment of the present invention;

[0029] Figure 4 This is a schematic diagram of the structure of the device for monitoring the forming of additively manufactured workpieces in an embodiment of the present invention.

[0030] Figure label:

[0031] 1-Stereolithography component, 11-Printing chamber, 12-Base panel, 121-Base panel through hole, 13-Powder spreading scraper, 14-Sintering laser, 2-CT component, 21-Radiation emitter, 22-Radiation receiver, 3-Printing cylinder, 31-Printing cylinder frame, 32-Rotating component, 33-Lifting component, 34-Printing tray. Detailed Implementation

[0032] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0033] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments.

[0034] Example 1

[0035] Embodiment 1 of the present invention provides a method for monitoring the forming quality of additively manufactured workpieces, such as... Figure 1 As shown, the method includes:

[0036] Step 1: Print the workpiece layer by layer;

[0037] Step 2: After printing a fixed number of layers, pause the printing operation, raise the printing cylinder 3, and remove any powder present on the workpiece;

[0038] Step 3: Perform a CT scan on the workpiece using the X-ray emitter 21 and the X-ray receiver 22;

[0039] Step 4: Reconstruct the acquired CT data to generate tomographic images and 3D images of the formed parts of the workpiece.

[0040] Step 5: Analyze the reconstructed image to identify internal defects, calculate dimensional accuracy, and decide whether to continue printing or stop processing.

[0041] In step 1, based on the preset 3D model parameters, the virtual design is gradually transformed into a physical workpiece by stacking materials layer by layer, providing a foundation for subsequent monitoring and finished product formation. The preset parameters include factors such as printing speed, temperature, and material supply. Precise control of these parameters can ensure the stable quality of each layer of printing and reduce defects caused by fluctuations in printing parameters from the source.

[0042] In step 2, by removing the powder present on the workpiece, interference with monitoring is avoided. During the additive manufacturing process, unmelted powder will adhere to the surface of the workpiece. If it is not removed, during CT scanning, this powder will scatter and absorb the X-rays, interfering with the X-ray receiver 22's reception of the signal of the true internal structure of the workpiece, resulting in inaccurate CT data and affecting the accuracy of subsequent image reconstruction and defect identification. After removing the powder, the X-rays can penetrate the workpiece more directly and accurately, and the signal received by the X-ray receiver 22 can more realistically reflect the density distribution and structural characteristics inside the workpiece, thereby improving the accuracy and reliability of CT monitoring.

[0043] In step 3, CT scanning is used to obtain internal information of the workpiece, enabling the monitoring of workpiece quality and timely detection of defects that occur during the printing process, such as pores, cracks, and poor interlayer bonding, providing timely basis for subsequent quality control and decision-making.

[0044] In step 4, the acquired CT data is converted into intuitive tomographic images and three-dimensional images through image reconstruction algorithms. These images can clearly show the various layers and overall structure inside the workpiece, allowing operators to intuitively observe the details inside the workpiece, which is convenient for evaluating and analyzing the quality of the workpiece.

[0045] In step 5, by analyzing the reconstructed images, the type and extent of defects inside the workpiece can be accurately identified. At the same time, the dimensional accuracy of the workpiece can be calculated, and the quality status of the workpiece can be comprehensively evaluated. If the workpiece quality meets the requirements, printing continues to complete the manufacturing of the entire workpiece. If serious defects or dimensional deviations exceed the allowable range, processing is stopped to avoid wasting materials and time. Meanwhile, printing parameters can be adjusted or other remedial measures can be taken to improve production efficiency and product quality. Through CT monitoring, defects in the printing process can be detected and dealt with in a timely manner to avoid the accumulation and expansion of defects, thereby improving the internal quality and overall performance of the additive manufacturing workpiece.

[0046] In summary, during the inspection phase, printing is paused after a fixed number of layers, and a CT scan is performed using X-ray emitter 21 and receiver. This method can penetrate the workpiece to obtain comprehensive internal information and accurately capture minute defects, improving data accuracy compared to traditional qualitative judgments relying on statistical models. In the image reconstruction stage, algorithms are used to transform CT data into intuitive and clear tomographic and 3D images, presenting information such as the shape, location, and size of defects, enhancing data visualization and interpretability, and reducing human judgment errors. Finally, based on the reconstructed images, defects are analyzed, dimensional accuracy is calculated, and rapid decisions are made, which can promptly reflect changes in workpiece quality during printing, avoiding misjudgments or omissions caused by data lag, and ensuring that the monitoring data truly and accurately reflects the current printing status. This provides reliable support for adjusting the printing process, improves the overall accuracy of monitoring data, and solves the technical problems existing in the current technology.

[0047] In one specific embodiment of the present invention, step 1 further includes the step of injecting a protective gas into the stereolithography component 1 to prevent the metal powder from oxidizing during the printing process.

[0048] By injecting protective gas into the stereolithography component 1, oxidation of metal powder can be prevented, ensuring the stability of the printing process, reducing defects, providing a clean environment for CT monitoring, improving monitoring accuracy, and enhancing the quality of printed parts.

[0049] In one specific embodiment of the present invention, in step 2, the powder present on the workpiece is removed by blowing powder and / or sucking powder.

[0050] The powder blowing and suction mechanism can remove powder, allowing the X-rays to penetrate the workpiece more directly and accurately, thereby obtaining more accurate CT data and providing a reliable foundation for subsequent high-quality image reconstruction, thus reducing X-ray scattering and absorption interference.

[0051] In one specific embodiment of the present invention, in step 2, the printing job is paused after printing 20-50 layers.

[0052] During the additive manufacturing process of layer-by-layer material deposition, unmelted powder adheres to the workpiece surface. As the number of printed layers increases, the amount of powder accumulated gradually increases. If the powder is removed only after a large amount has accumulated, it will scatter and absorb X-rays during CT scanning, interfering with the X-ray receiver 22's reception of signals from the actual internal structure of the workpiece. By pausing powder removal after printing 20-50 layers, the amount of powder accumulation is relatively moderate. Timely removal can effectively avoid signal interference caused by excessive powder during subsequent scans, ensuring that the signals received by the X-ray receiver 22 more accurately reflect the density distribution and structural characteristics inside the workpiece, thereby improving the accuracy of CT monitoring.

[0053] In one specific embodiment of the present invention, in step 2, after printing stops, the printing cylinder 3 rises and blows away the powder above the workpiece. The printing cylinder (3 is a platform that carries the printed part and the unmelted powder) rises, and the powder blowing and suction mechanism removes the unmelted powder covering the printed part of the workpiece, so that the upper surface of the printed workpiece is fully exposed, thereby reducing the interference of powder on X-ray imaging. As a result, the noise and blur caused by powder interference are reduced, thereby improving the clarity of the generated tomographic image and three-dimensional image.

[0054] In one specific embodiment of the present invention, in step 3, after the powder blowing and suction mechanism removes the unmelted powder covering the printed workpiece, the printing cylinder 3 rotates, and works with the ray emitter 21 and the ray receiver 22 to complete the imaging scan. The exposed printed workpiece is used as the scanning object and rotates 360° under the rotation of the printing cylinder 3. At the same time, the ray emitters 21 located on both sides emit rays, and the ray receivers 22 receive the rays passing through the printed body, and collect two-dimensional projection images from different angles.

[0055] The printed workpiece rotates 360° under the drive of the printing cylinder 3, so that the ray emitters 21 located on both sides can emit rays from various angles to penetrate the workpiece, and the ray receivers 22 can receive the rays passing through different parts of the printed body, thereby acquiring two-dimensional projection images from different angles. This data acquisition method can obtain complete information about the internal structure of the workpiece, which reduces the occurrence of imaging blind spots, and allows all the details inside the workpiece to be clearly presented, thus improving the accuracy of imaging.

[0056] In one specific embodiment of the present invention, in step 3, during CT scanning, the printing cylinder 3 rotates via a rotating platform at its bottom to meet the motion requirements of CT scanning.

[0057] A rotating platform is set at the bottom of the printing cylinder, which causes the printing cylinder to rotate the workpiece. This allows the X-ray emitter 21 and X-ray receiver 22 to project and collect images of the workpiece from multiple different angles. The workpiece continuously changes its position and angle relative to the X-ray emitter 21 and X-ray receiver 22, thereby obtaining complete projection information. Since the projection data of the workpiece can be obtained from multiple angles, the use of the rotating platform increases the amount of information required for image reconstruction. More projection angles can more accurately describe the density distribution and structural features inside the workpiece, reduce artifacts and noise interference in the image reconstruction process, and improve the clarity, contrast and resolution of the reconstructed image, so that the tiny defects and detailed structures inside the workpiece can be presented more clearly.

[0058] In one specific embodiment of the present invention, in step 4, a three-dimensional internal structure model of the printed part of the workpiece is reconstructed based on the two-dimensional projection images of the printed part of the workpiece from different angles. For example, the internal structure model can be reconstructed by a filtered back projection algorithm.

[0059] By acquiring two-dimensional projection images from different angles and using computed tomography (CT) reconstruction algorithms, these scattered two-dimensional information can be integrated into a complete and continuous three-dimensional internal structure model. This model can display details such as holes, cracks, and interlayer bonding inside the workpiece, providing a more comprehensive understanding of the workpiece's internal structure. As a result, potential quality problems can be detected in a timely manner during the printing process.

[0060] In one specific embodiment of the present invention, in step 5, after analysis, no internal defects are found, the quality is determined to be qualified, and the process returns to step 2 to continue printing the next cycle;

[0061] Analysis revealed repairable defects, such as pores on the surface of the workpiece. The process was then returned to step 2, where subsequent printing parameters (such as laser power and scanning speed) were adjusted to compensate for these defects.

[0062] Analysis revealed irreparable defects, such as holes or cracks inside the workpiece, prompting the printing process to be halted.

[0063] Once the quality is deemed satisfactory, the process returns to step 2 to continue printing. This fully utilizes the completed inspection results, ensuring the current printing quality meets standards and allowing for the orderly advancement of subsequent printing processes. This avoids unnecessary interruptions in inspection that could impact overall printing efficiency and guarantees the continuity of the production process. If repairable defects such as pores are found on the workpiece surface, the process returns to step 2 and adjusts subsequent printing parameters for compensation. By optimizing parameters such as laser power and scanning speed, the molten pool condition can be improved, reducing the likelihood of pore formation and allowing for defect repair in subsequent printing, thus improving workpiece quality. If irreparable defects such as holes or cracks exist inside the workpiece, the printing program can be stopped to minimize losses, preventing the continued investment of time and materials to produce substandard products, reducing production costs, and preventing defective workpieces from flowing into subsequent stages and potentially causing safety issues.

[0064] Example 2

[0065] Embodiment 2 of the present invention is a further improvement based on Embodiment 1, such as... Figure 2 As shown, step 5 also includes using the precise three-dimensional geometric data of the formed part obtained by the CT scan after each CT scan, combined with the preset material thermophysical property parameters and the process parameters to be used for subsequent printing, to calculate and evaluate the local residual stress accumulation of the internal structural components using a thermodynamic calculation model. Based on the above evaluation results, the risk of deformation or cracking that may be caused to the subsequent printing layer is analyzed, and intelligent decision-making and parameter adjustment suggestions are provided based on the evaluation results.

[0066] Precise 3D geometric data obtained from CT scans provides a framework for constructing digital models of internal structural components. This allows thermodynamic calculation models to operate based on the actual structure, improving assessment accuracy. It also helps locate the approximate locations of potential problems. When combined with residual stress distribution, it can identify geometric features prone to deformation or cracking. The thermodynamic calculation model assesses the accumulation of local residual stress, applying mathematical and physical principles to comprehensively calculate 3D geometric data, material parameters, and process parameters. This quantifies the magnitude and distribution of residual stress in various parts of the internal structural components, providing a scientific basis for accurately assessing deformation and cracking risks. For additive manufacturing parts with complex internal structures, it effectively handles complex geometries and boundary conditions, accurately calculating stress states. Analysis of residual stress assessment results regarding potential deformation or cracking risks in subsequent printing layers allows for early detection of potential risks. This enables operators to take preventative measures, such as adjusting support structures or changing the printing sequence, reducing printing failures and ensuring the subsequent printing process remains under control, thus improving printing quality and reliability.

[0067] Based on this, such as Figure 3 As shown, the calculation steps of the thermodynamic model include:

[0068] Step 5.1: Extract the current three-dimensional geometric model of the formed workpiece and automatically identify stress concentration areas;

[0069] Step 5.2: Automatically obtain the process parameters of the current and subsequent printing layers, and call up the thermophysical properties of the materials used;

[0070] Step 5.3: For the identified stress concentration areas, use the model to calculate the local temperature gradient, thermal stress distribution, and residual stress accumulation.

[0071] Step 5.4: Compare the calculated local stress accumulation and stress gradient with the preset material safety threshold to assess the risk;

[0072] Step 5.5: Based on the risk assessment results, provide intelligent decision-making and parameter adjustment suggestions.

[0073] In step 5.1, the CT monitoring system scans the formed workpiece to obtain image data of different layers inside the workpiece; the image data is processed to remove noise from the CT image, improve image quality, enhance edge and detail information in the image to facilitate subsequent segmentation and recognition, separate the workpiece part from the background part in the image, and extract the contour information of the workpiece; based on the segmented CT image data, a three-dimensional geometric model of the workpiece is generated using a three-dimensional reconstruction algorithm.

[0074] In step 5.1, the geometric inspection tools and surface analysis tools of CAD software are used to automatically monitor potential stress concentration sources in the model, such as sharp corners, sharp edges, small fillet radii, and abrupt changes in surface curvature, thereby obtaining stress concentration areas.

[0075] By using CT scanning, image processing, 3D reconstruction, and CAD analysis, solid workpieces are transformed into editable 3D CAD models. By automatically monitoring geometric anomalies (sharp corners, sharp edges, small rounded corners, abrupt changes in curved surfaces, etc.), potential failure risks are predicted. Thus, a closed loop of monitoring, modeling, and optimization is achieved, transforming hidden geometric defects into quantifiable data.

[0076] In step 5.2, the process parameters of the currently printed layer are read in real time by the control system of the stereolithography component 1, including laser power, scanning speed, scanning spacing, layer thickness, etc., and a database containing the thermophysical properties of commonly used additive manufacturing materials is established. This database can cover parameters such as thermal conductivity, specific heat capacity, density, melting point, and solidification point of materials at different temperatures. According to the type of material currently being printed, the corresponding thermophysical property data is automatically retrieved from the database.

[0077] By reading the current layer's process parameters in real time and calling the material thermophysical property database, boundary conditions and material property inputs are provided for the subsequent thermo-mechanical coupling model, which is beneficial for deformation prediction.

[0078] In step 5.3, a multiphysics coupling model (such as COMSOL Multiphysics) can be used to calculate the local temperature gradient, and then calculate the thermal stress distribution and the cumulative amount of residual stress.

[0079] Among them, the total accumulated stress σ total Thermal stress σ thermal With residual stress σ residual The vector sum, that is:

[0080] σ total =σ thermal +σ residual ;

[0081] The stress gradient is derived from the spatial derivative of the total stress field. Calculations are performed to assess the risk of localized stress concentration.

[0082] In step 5.4, the calculation results from step 5.3 are compared with the material safety threshold:

[0083] If the total accumulated stress exceeds the yield strength or fatigue limit, it is considered high-risk (requiring optimization of design / process).

[0084] If the stress gradient exceeds the critical value (the stress gradient threshold for crack initiation), it is classified as medium risk (requiring local reinforcement or monitoring).

[0085] Otherwise, it is considered low risk (acceptable).

[0086] In step 5.5, based on the risk assessment results in step 5.4, and combined with the pre-set decision rules and expert knowledge base, intelligent decision suggestions are generated. The decision rules can be formulated according to different risk levels and workpiece usage requirements. For example, for high-risk areas, it is recommended to immediately stop printing and carry out inspection and repair; for medium-risk areas, it is recommended to adjust printing parameters or add subsequent heat treatment processes.

[0087] If the risk assessment results indicate that printing parameters need to be adjusted, specific parameter adjustment suggestions will be provided based on the analysis results of the thermodynamic model. For example, if the excessive local stress accumulation is due to excessive laser power or excessive scanning speed, it is recommended to appropriately reduce the laser power or increase the scanning speed; if the excessive stress gradient is due to uneven layer thickness or unreasonable scanning spacing, it is recommended to adjust parameters such as layer thickness or scanning spacing.

[0088] Example 3

[0089] like Figure 4 As shown, this embodiment of the invention provides an apparatus for monitoring the forming quality of additively manufactured workpieces, used to implement the method described in Embodiment 1 or Embodiment 2. The apparatus includes:

[0090] 3D forming component 1, used for printing workpieces layer by layer;

[0091] CT component 2, which is mounted on stereolithography component 1, is used to perform CT scanning on the workpiece during the workpiece printing process;

[0092] The printing cylinder 3, which is capable of being raised, lowered, and rotated, is located in the stereolithography assembly 1 and provides motion conditions during CT scanning.

[0093] The stereolithography component 1 utilizes additive manufacturing technology (such as selective laser melting) to deposit materials (metal powder, plastic filaments, etc.) layer by layer according to pre-designed 3D model data, ultimately forming a complete workpiece. The CT component 2 can perform CT scanning on the workpiece being printed without stopping the stereolithography component 1 or interrupting the printing process. CT scanning technology uses X-rays or other rays to penetrate the workpiece, and receives projection data from different angles through the X-ray receiver 22. Then, a computer is used to reconstruct the 3D structural image of the workpiece's interior. The printing cylinder 3 has a lifting function. During the additive manufacturing process, after each layer of material is deposited, the printing cylinder 3 will lower a certain height to provide space for the laying and melting of the next layer of material, ensuring that each layer of material is deposited in the correct position, thereby ensuring that the workpiece is formed layer by layer according to the design requirements. The printing cylinder 3 also has a rotation function. When the CT component 2 scans the workpiece, the rotation of the printing cylinder can make the workpiece move in a circle relative to the X-ray emitter 21 and the X-ray receiver 22, so that the CT scanning system can obtain projection data of the workpiece from multiple angles.

[0094] During the workpiece printing process, CT scanning is performed on the workpiece to directly present its internal three-dimensional structure, avoiding indirect signal conversion errors. High resolution enables quantitative analysis of defect size and shape, eliminating subjective judgment bias. Furthermore, it can scan and report defect information, allowing for timely correction of process parameters and preventing defect accumulation caused by offline monitoring delays. Compared to indirect methods such as acoustic emission and infrared thermography, the device described in this embodiment improves monitoring accuracy and reliability, ensuring additive manufacturing quality.

[0095] One specific implementation of the present invention is as follows: Figure 4 As shown, the stereolithography component 1 includes a printing chamber 11, and a printing cylinder 3 is disposed inside the printing chamber 11.

[0096] The printing chamber 11 provides an openable, closed, and stable environment, effectively isolating it from external environmental interference such as airflow and dust. This prevents defects such as porosity and cracks caused by external factors, improving the quality and performance of the workpiece. In addition, the printing chamber 11 can contain inert gases (such as argon) to prevent oxidation reactions between the metal material and oxygen during high-temperature melting. Furthermore, the closed printing chamber 11 makes it easier to precisely control and adjust process parameters such as temperature and pressure, providing favorable conditions for additive manufacturing with different materials and process requirements.

[0097] One specific implementation of the present invention is as follows: Figure 4 As shown, the stereolithography assembly 1 also includes a base panel 12, a powder spreading blade 13, and a sintering laser 14. The base panel 12 is disposed in the printing chamber 11, and a base panel through hole 121 is provided on the base panel 12 for the printing cylinder 3 to pass through. The powder spreading blade 13 and the sintering laser 14 are both movably disposed in the printing chamber 11. The powder spreading blade 13 is close to the surface of the base panel 12, and the sintering laser 14 is located above the printing cylinder 3.

[0098] The base panel 12 provides a supporting surface for additive manufacturing. Before printing begins, printing material (such as metal powder) is evenly spread on the base panel 12. Simultaneously, the base panel 12 cooperates with the printing cylinder 3. A through-hole 121 on the base panel 12 allows the printing cylinder 3 to pass through, enabling the printing cylinder 3 to be positioned below the base panel 12 and to move up and down within the through-hole 121 according to printing requirements. Through the coordinated work of the base panel 12 and the printing cylinder 3, the height and position of each layer of printing material are controlled, achieving layer-by-layer deposition of the workpiece. The powder spreading scraper 13 is used to spread the powder on the base panel before each layer of printing begins. The printing material on plate 12 is evenly spread. In addition, the powder spreading blade 13 is used to scrape off excess material, making the material usage of each layer more precise and avoiding material waste. The sintering laser 14 is used to emit a high-energy laser beam. When the laser beam irradiates the printing material spread on the base plate 12, it will cause the material to melt rapidly. The sintering laser 14 selectively melts the material according to the preset scanning path, so that the melted material is fused with the next layer or adjacent material, thereby realizing the layer-by-layer construction of the workpiece. This improves the forming accuracy and internal quality of the workpiece, and also improves production efficiency and material utilization.

[0099] One specific implementation of the present invention is as follows: Figure 4 As shown, the stereolithography component 1 also includes a powder blowing and suction mechanism, which is mounted on the sintering laser 14.

[0100] After the material is melted and formed, some unmelted powder may remain in the forming area. The powder blowing and suction mechanism blows these residual powders away from the forming area by blowing air, preventing them from interfering with the spreading and melting of the new layer of material during subsequent printing, thus ensuring the purity and quality of each printed layer. In addition, before the powder spreading blade 13 spreads the material, the powder blowing and suction mechanism can also agitate and disperse the powder on the base plate 12 to a certain extent by blowing air, making the powder looser and more uniform, which is conducive to the powder spreading blade 13 spreading the powder evenly into a thin layer, improving the uniformity of material spreading. The powder blown up during the powder blowing process and the excess powder generated during the printing process can be recovered in time by the powder suction function. This not only avoids the powder flying around in the printing chamber 11, polluting the equipment and the environment, but also allows the recovered powder to be reused, reducing material costs.

[0101] As an improvement, the powder blowing and suction mechanism includes a powder blowing tube and a powder suction tube, both of which are mounted on the sintering laser 14.

[0102] The powder blowing tube is used to clean residual powder in the forming area. The airflow blown out by the powder blowing tube can remove some heat and smoke, reduce the temperature of the heat-affected zone, reduce the scattering and interference of smoke on the laser beam, and ensure that the laser beam can be focused on the material surface, thus improving the melting quality. The powder suction tube is used to recover excess powder. The powder blown out by the powder blowing tube and the excess powder generated during the printing process not only prevent the powder from flying around in the printing chamber 11 and polluting the equipment and environment, but also allows the recovered powder to be reused, reducing material costs.

[0103] One specific implementation of the present invention is as follows: Figure 4 As shown, the CT component 2 includes a radiation emitter 21 and a radiation receiver 22, which are located on both sides of the printing cylinder 3.

[0104] The X-ray emitter 21 is the energy source for CT monitoring, capable of generating X-ray beams of specific types (such as X-rays, gamma rays, etc.) and energies. These rays can penetrate the workpiece being manufactured, providing a basis for imaging monitoring of the workpiece. The X-ray receiver 22 is located on the other side of the printing cylinder 3. Its function is to receive the X-rays after they have been attenuated by the workpiece. When the X-rays penetrate the workpiece, due to the differences in the tissue structure, density, etc. of different parts of the workpiece, the absorption and scattering of the X-rays are also different. The X-ray receiver 22 can capture these changed X-ray signals. The X-ray receiver 22 can also convert the received X-ray signals into electrical signals or other processable signal forms, and amplify, filter, digitize, etc., these signals through built-in circuits and algorithms. Finally, based on the X-ray attenuation at different locations, a two-dimensional or three-dimensional image of the internal structure of the workpiece is reconstructed, intuitively displaying the defects, pores, cracks, and other features inside the workpiece.

[0105] In one specific embodiment of the present invention, a protective gas injection module is further included, which is used to inject protective gas into the interior of the stereolithography component 1.

[0106] The protective gas injection module injects inert protective gas into the device, eliminating oxygen from the air and creating an oxygen-free environment around the workpiece and the molten pool. This effectively prevents oxidation reactions and ensures the surface quality and internal properties of the workpiece.

[0107] One specific implementation of the present invention is as follows: Figure 4 As shown, the printing cylinder 3 includes a printing cylinder frame 31, a rotating component 32, a lifting component 33, and a printing tray 34. The printing cylinder frame 31 is detachably and fixedly installed in the stereolithography assembly 1. The rotating component 32 is installed on the printing cylinder frame 31, the lifting component 33 is installed on the rotating component 32, and the printing tray 34 is installed on the lifting component 33.

[0108] The printing cylinder frame 31 provides a mounting base for other components; the rotating component 32 provides rotational power to the printing tray 34, enabling the workpiece to rotate at multiple angles in the horizontal plane. For example, the rotating component 32 can be implemented by a stepper motor in conjunction with a synchronous belt; the lifting component 33 is used to support the printing tray 34 and enable vertical movement. After each layer of material is stacked, it descends by a preset layer thickness to provide space for the laying and melting of the next layer of material. For example, the lifting component 33 can be implemented by a ball screw in conjunction with a servo motor; the printing tray 34 directly supports the workpiece in the additive manufacturing process.

[0109] Example 4

[0110] Embodiment 4 of the present invention is a further improvement based on Embodiment 3, wherein the ray emitter 21 includes:

[0111] The first transmitting tube, with a tube voltage of 120-150kV, is used to penetrate thick cross-section areas to monitor deep pore defects;

[0112] The second transmitter, with a voltage of 40-60kV, is used to obtain shallow surface resolution and identify microcracks and interlayer bonding defects.

[0113] A height adjustment seat is mounted on the three-dimensional molding assembly 1. It is used to mount the first and second transmitter tubes. The first and second transmitter tubes are arranged side by side in the vertical direction on the height adjustment seat, and the first and second transmitter tubes can move in the vertical direction on the height adjustment seat.

[0114] The first emission tube is used to provide high-energy rays. Its tube voltage is set at 120-150kV. The higher tube voltage enables electrons to be accelerated in the electric field to obtain higher energy. After impacting the target material, high-energy X-rays are generated, which can penetrate the thicker cross-sectional areas in the additive manufacturing workpiece. It is also used to monitor deep pore defects. During the additive manufacturing process, there may be defects such as pores inside the workpiece. If these defects exist in the deep layer, they are difficult to detect by ordinary monitoring methods. High-energy X-rays can penetrate deep tissues. By analyzing information such as the intensity change of the rays after penetration, the location, size and distribution of deep pore defects can be monitored, providing a basis for assessing the internal quality of the workpiece.

[0115] The second emission tube provides low-energy X-rays. Its tube voltage is 40-60kV. The relatively low tube voltage results in lower energy for electrons, leading to lower energy X-rays. Low-energy X-rays have shorter wavelengths, enabling the acquisition of shallow surface resolution. Low-energy X-rays are more sensitive to the interactions of shallow materials, providing a clearer view of the structural information of the shallow surface of the workpiece, thus achieving higher shallow surface resolution. In addition, they are used to identify microcracks and interlayer bonding defects. In additive manufacturing, defects such as microcracks are prone to appear on the workpiece surface and at interlayer bonding points. Low-energy X-rays can effectively monitor these shallow micro-defects. By observing the characteristic changes in X-ray imaging, the location and orientation of microcracks, as well as the tightness of interlayer bonding, can be accurately identified, helping to promptly detect and resolve potential surface and interlayer quality problems.

[0116] The height adjustment base is used to mount and fix the first and second transmitting tubes. It is set on the three-dimensional molding assembly 1 and provides a movable mounting position for the first and second transmitting tubes, allowing them to move vertically on the height adjustment base. This enables the positions of the two transmitting tubes to be flexibly adjusted according to different parts of the workpiece and monitoring needs, so that they can accurately illuminate the area to be monitored, achieving effective monitoring of different depths and positions of the workpiece.

[0117] This enables comprehensive monitoring of additively manufactured workpieces from the shallow surface to the deep interior. The second emission tube is used to monitor shallow surface and interlayer bonding defects, while the first emission tube is used to monitor deep pore defects. The two complement each other, avoiding the limitations of monitoring with a single X-ray emitter and improving the coverage and accuracy of defect monitoring.

[0118] Correspondingly, two layers of ray receivers are stacked vertically opposite the emitting tubes (e.g., the upper layer receives high-energy rays and the lower layer receives low-energy rays), with each layer of ray receivers aligned with its corresponding emitting tube to ensure an unobstructed projection path.

[0119] By receiving high-energy and low-energy rays separately at the upper and lower layers, layered monitoring of defects at different depths of the workpiece is achieved. The upper-layer ray receiver focuses on monitoring deep structures, while the lower-layer ray receiver focuses on monitoring shallow surfaces. This layered setup helps to more systematically and comprehensively assess the quality of the workpiece. At the same time, the combination of the two layers can simultaneously obtain detailed information about different depths of the workpiece, avoiding the information gaps that may occur with monitoring by a single ray emitter and improving the comprehensiveness of defect monitoring. Since high-energy and low-energy rays have different characteristics and monitoring focuses, receiving and analyzing the corresponding ray signals by two layers of ray receivers can mutually verify and supplement the monitoring results.

[0120] Example 5

[0121] Embodiment 5 of the present invention is a further improvement based on Embodiment 3 or Embodiment 4. The X-ray receiver 22 includes a first detection unit, which includes a fan-shaped arc detector module, a flat panel detector module, a bracket, and a lead shielding layer. The flat panel detector module is installed in the central area of ​​the fan-shaped arc detector module. For example, the flat panel detector module is made of CMOS or a-Si material, with a pixel size ≤100μm and a dynamic range ≥16bit. The bracket is set on the stereolithography component 1 and is used to support the fan-shaped arc detector module, enabling the fan-shaped arc detector module to rotate in the horizontal direction and adjust its height in the vertical direction to adapt to the monitoring needs of workpieces with different shapes. The lead shielding layer covers the non-monitoring surface of the flat panel detector module to reduce X-ray scattering noise interference.

[0122] The fan-shaped arc surface detector module is used to receive scattered or transmitted signals from the side or tilt direction of the workpiece. When X-rays penetrate the workpiece, internal defects (such as pores and cracks) will cause the rays to scatter. The large-angle coverage capability of the fan-shaped arc surface detector module enables it to receive these scattered signals from the side or tilt direction. These signals can contain detailed information such as the edge and shape of the defects, which helps to identify defects in small or complex structures. For workpieces with complex geometries, the side / tilt signal reception capability can reduce the monitoring blind spots caused by the shape of the workpiece. In addition, the fan-shaped arc surface detector module is mainly used to quickly obtain the overall information of the workpiece.

[0123] The flat panel detector module is used to receive the projected signal in the orthogonal direction. The projected signal in the orthogonal direction is used to generate high-resolution two-dimensional projection images or reference data for three-dimensional reconstruction. The flat panel detector module is used for high-precision monitoring of key areas or suspected defective parts. By having two X-ray receivers complement each other, it not only ensures the comprehensiveness of monitoring but also meets the monitoring accuracy requirements of different parts. The bracket allows the X-ray receivers to flexibly adjust the monitoring angle to adapt to the monitoring needs of workpieces with different shapes. The lead shielding layer reduces X-ray scattering noise interference.

[0124] In summary, the fan-shaped arc surface detector module offers wide-angle coverage, enabling it to receive scattered or transmitted signals from the workpiece's sides or tilt, quickly acquiring overall information, reducing blind spots, and facilitating defect identification. Combining the fan-shaped arc surface detector module with the flat panel detector module leverages the latter's wide-angle coverage to receive signals from the sides or tilt, rapidly acquiring overall workpiece information, reducing blind spots, and effectively identifying minute and complex defects. Simultaneously, the flat panel detector module receives orthophoto signals, generating high-resolution images or 3D reconstruction reference data for high-precision monitoring of critical areas or suspected defect locations. The complementary advantages of both modules enhance the accuracy and reliability of monitoring.

[0125] Those skilled in the art should understand that the above embodiments are merely for illustrating the present invention and are not intended to limit the scope of the invention. Those skilled in the art can make other changes or modifications based on the above disclosure, and these changes or modifications still fall within the scope of the present invention.

Claims

1. A method for monitoring the forming quality of additively manufactured workpieces, comprising an apparatus for monitoring the forming of additively manufactured workpieces, characterized in that, The method includes: Step 1: Print the workpiece layer by layer; Step 2: After printing a fixed number of layers, pause the printing job and remove any powder from the workpiece; Step 3: Perform a CT scan on the workpiece using a radiation emitter and a radiation receiver; Step 4: Reconstruct the acquired CT data to generate tomographic images and 3D images of the formed parts of the workpiece. Step 5: Analyze the reconstructed image to identify internal defects, calculate dimensional accuracy, and decide whether to continue printing or stop processing.

2. The method for monitoring the forming quality of additively manufactured workpieces according to claim 1, characterized in that, In step 3, during the CT scan, the printing cylinder rotates via a rotating platform at the bottom.

3. The method for monitoring the forming quality of additively manufactured workpieces according to claim 1, characterized in that, In step 2, the powder present on the workpiece is removed by blowing and / or sucking powder.

4. The method for monitoring the forming quality of additively manufactured workpieces according to claim 1, characterized in that, Step 1 also includes injecting a protective gas into the stereolithography assembly to prevent the metal powder from oxidizing during the printing process.

5. The method for monitoring the forming quality of additively manufactured workpieces according to claim 1, characterized in that, In step 2, pause the printing job after printing 20-50 layers.

6. The method for monitoring the forming quality of additively manufactured workpieces according to claim 1, characterized in that, In step 2, after printing stops, the printing cylinder rises and blows away the powder above the workpiece, exposing the upper surface of the printed workpiece.

7. The method for monitoring the forming quality of additively manufactured workpieces according to claim 6, characterized in that, In step 3, after the powder blowing and suction mechanism removes the unmelted powder covering the printed workpiece, the printing cylinder rotates, and the X-ray emitter and X-ray receiver complete the imaging scan of the printed workpiece.

8. The method for monitoring the forming quality of additively manufactured workpieces according to claim 7, characterized in that, In step 4, a three-dimensional internal structure model of the printed part of the workpiece is reconstructed based on the two-dimensional projection images of the printed part from different angles.

9. The method for monitoring the forming quality of additively manufactured workpieces according to claim 1, characterized in that, If a repairable defect is found in step 5, return to step 2, adjust subsequent printing parameters to compensate, and continue printing.

10. The method for monitoring the forming quality of additively manufactured workpieces according to claim 1, characterized in that, In step 5, an unrepairable defect was found, and the printing process was stopped.

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