Coaxial SLM real-time monitoring and real-time feedback control device and method

Abstract

The application discloses a coaxial SLM real-time monitoring and real-time feedback control device and method, the device comprises a laser light path module, a coaxial monitoring light path module and a feedback control module. The laser light path module is connected with the feedback control module to realize the SLM processing process, and is connected with the coaxial monitoring light path module, and the infrared thermal imager and the high-speed camera are used to realize the real-time temperature distribution and the molten pool area monitoring of the SLM processing process. The semiconductor laser is installed above the processing surface to generate laser irradiation to the processing surface as an auxiliary light source of the high-speed camera, and the monitoring effect is improved. The high-speed camera and the infrared thermal imager are respectively connected with the feedback control module, the feedback control module analyzes and processes the molten pool state data to be displayed in real time to supply the user with online analysis and printing, and meanwhile generates a real-time feedback control signal to adjust the laser power and the scanning speed in the processing process, and the stability of the SLM process is improved.

Description

Technical Field

[0001] This invention relates to the field of additive manufacturing technology, and in particular to a coaxial SLM real-time monitoring and real-time feedback control device and method. Background Technology

[0002] Selective Laser Melting (SLM) is a popular metal additive manufacturing (AM) technology that has been widely used in the automotive, medical, and aerospace industries to manufacture critical components. SLM works by using a high-energy laser beam to selectively melt metal powder. The melted powder then solidifies, and the process is repeated layer by layer to ultimately create a metal part.

[0003] During SLM (Selective Laser Melting) processing, the thermal stress in the molten pool formed by the melting of metal powder can lead to abnormal disturbances in the molten pool and potentially cause defects such as porosity, spheroidization, and keyholes, resulting in fluctuations in part quality. The generation of molten pool thermal stress is directly related to the laser power and scanning speed. Therefore, in the complex SLM process, to obtain high-quality formed parts, it is essential to monitor a series of key parameters during the selective laser melting process, along with the molten pool morphology and temperature information. Real-time control of the laser power must be implemented based on the molten pool morphology data and temperature information. Process monitoring and real-time control of laser parameters are necessary to ensure part quality and future production.

[0004] Researchers are continuously optimizing methods for monitoring the molten pool in SLM (Self-Made Metal Lung) machining. Some researchers use side-mounted high-speed cameras and pyrometers to monitor the molten pool. Others connect high-speed cameras to laser beam paths for monitoring the molten pool area. However, these methods cannot obtain clear images of the molten pool area or temperature signals, nor can they use real-time acquired machining process signals for real-time feedback control of machining parameters to reduce defects, improve the quality of molded parts, and ensure the stability of SLM machining. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention proposes a coaxial SLM real-time monitoring and feedback control device and method. The purpose is to perform real-time monitoring and feedback control of the SLM machining process, thereby solving the problems in existing technologies where clear images of the molten pool area and temperature signals cannot be obtained, and where real-time acquired machining process signals cannot be used for real-time feedback control of machining process parameters, reducing the generation of defects, improving the quality of molded parts, and ensuring the stability of SLM machining.

[0006] To achieve the above objectives, the specific contents of this invention are as follows:

[0007] A coaxial SLM real-time monitoring and feedback control device includes a feedback control module, a laser optical path module, and a coaxial monitoring optical path module. The laser optical path module includes a laser, a collimating lens, a first beam combiner, a scanning galvanometer, and a field lens. The laser and the scanning galvanometer are respectively connected to the feedback control module. The collimating lens is connected to the laser via an optical fiber. The feedback control module controls the laser to generate a laser with a preset power. After being collimated by the collimating lens, the laser passes through the first beam combiner. The feedback control module controls the scanning galvanometer to reflect the laser transmitted through the first beam combiner to a designated position on the processing surface, and then focuses it onto the processing surface through the field lens.

[0008] The coaxial monitoring optical path module includes a second beam combiner, an infrared thermal imager, a high-speed camera, a first filter, a second filter, and a semiconductor laser. The second beam combiner, the second filter, and the high-speed camera are respectively arranged in the vertical direction of the first beam combiner. The first filter and the infrared thermal imager are respectively arranged in the horizontal direction of the second beam combiner. The high-speed camera and the infrared thermal imager are respectively connected to the feedback control module. The semiconductor laser is mounted above the processing surface, and the laser generated by the semiconductor laser irradiates the processing surface.

[0009] Furthermore, the feedback control module includes a high-speed camera controller, a temperature signal processor, and a computer. The high-speed camera controller, temperature signal processor, laser, and scanning mirror are respectively connected to the computer. The high-speed camera is connected to the high-speed camera controller, and the infrared thermal imager is connected to the temperature signal processor.

[0010] Furthermore, the high-speed camera controller includes a high-speed camera control module, an image processing module, and a data transfer module. The high-speed camera control module is connected to both the computer and the image processing module. The image processing module is connected to the data transfer module, and the data transfer module is connected to the computer. The temperature signal processor includes a thermal imager control module, a temperature distribution processing module, and a data storage module. The thermal imager control module is connected to both the computer and the temperature distribution processing module. The temperature distribution processing module is connected to the data storage module, and the data storage module is connected to the computer.

[0011] Furthermore, the first filter is a narrowband filter in the 810-920nm band with a transmittance of over 99%; the second filter is a single-pass filter in the 450nm band with a transmittance of over 99%; the semiconductor laser generates 450nm band laser; and the laser with the preset power is a high-energy laser in the 1080nm band.

[0012] The control method of the coaxial SLM real-time monitoring and real-time feedback control device, as described above, includes the following steps:

[0013] Step 1: During SLM printing, the feedback control module controls the high-speed camera and infrared thermal imager to start recording, and controls the laser to emit a laser of preset power and controls the scanning speed and scanning path of the scanning galvanometer. The laser of preset power is reflected by the collimating lens, the first beam combiner and the scanning galvanometer in sequence to the field lens, and then focused by the field lens onto the metal powder on the processing surface, so that the metal powder on the processing surface melts rapidly to form a molten pool. At the same time, the laser generated by the semiconductor laser is irradiated onto the molten pool area of ​​the processing surface.

[0014] Step 2: During the processing, the high-power 450nm laser reflected light generated by the semiconductor laser on the processing surface in Step 1, mixed with the molten pool self-luminescence in the 450nm and 810-920nm bands, enters the laser optical path module through the field lens, and then is reflected by the scanning galvanometer to the first beam combiner. The first beam combiner reflects the light to the second beam combiner. The second beam combiner reflects the molten pool self-luminescence in the 810-920nm band of the mixed beam to the first filter and then transmits it to the infrared thermal imager for coaxial molten pool temperature distribution imaging. At the same time, the molten pool self-luminescence in the 450nm band and the high-power 450nm laser reflected light generated by the semiconductor laser are transmitted to the second filter and then transmitted to the high-speed camera for coaxial molten pool area imaging.

[0015] Step 3: The feedback control module processes the molten pool area image from the high-speed camera and the molten pool temperature distribution data from the infrared thermal imager in real time, and obtains and stores the ROI area image and the ROI area temperature distribution from the molten pool area image centered on the laser spot position.

[0016] Step 4: The ROI region image and ROI region temperature distribution from Step 3 are mapped to the corresponding processing positions on the single-layer path and the 3D model and displayed in real time through the feedback control module. At the same time, the temperature distribution and temperature gradient of the molten pool are analyzed to see if there are any abnormalities. Combined with the analysis of abnormalities in the molten pool fluctuation state, molten pool morphology, molten pool splash and surrounding powder distribution at the same moment, it is determined whether to generate a feedback control signal.

[0017] Furthermore, the method for determining the generated feedback control signal includes the following steps:

[0018] Step 41: When the feedback control module determines that there are no abnormalities in the image and temperature distribution of the molten pool area during the SLM processing, it will continue to use the current printing process parameters by default.

[0019] Step 42: When the feedback control module determines that there is an abnormality in the image or temperature distribution of the molten pool area during the SLM processing, it generates a feedback control signal, adjusts the output laser power of the laser and the scanning speed of the scanning galvanometer in real time, and continues printing until the entire part is printed layer by layer.

[0020] Advantages of the present invention

[0021] The coaxial SLM real-time monitoring and feedback control device and method of the present invention generates a high-energy laser through a laser optical path module, which is collimated, reflected by a scanning galvanometer, and focused onto metal powder on the processing surface by a field lens to generate a molten pool, thereby realizing the SLM processing. The coaxial monitoring optical path module is based on two detectors, a high-speed camera and an infrared thermal imager, and a semiconductor laser, distributed on the same plane. The two are integrated into a coaxial optical system along the path of the processing laser by a beam combiner, and high-quality coaxial monitoring is achieved by auxiliary illumination from the semiconductor laser. The feedback control module is based on a high-speed camera and an infrared thermal imager on the same plane as the laser, and performs feedback control of processing parameters by analyzing and processing the molten pool temperature distribution and molten pool image.

[0022] (2) In the laser selective melting process, the coaxial monitoring of this invention analyzes the temperature distribution and image of the molten pool, enabling intuitive and real-time evaluation on the 3D model during and after printing. Users can analyze the printing process online or offline. The feedback control module can use the high-quality molten pool image and temperature distribution acquired in real time to control the laser power and scanning speed during processing, thereby ensuring the forming quality of the processed parts.

[0023] (3) The coaxial monitoring module of the present invention is in the same optical path as the laser, thus realizing true coaxial monitoring.

[0024] (4) The feedback control module of the present invention analyzes the temperature distribution of the molten pool and the control signal of the laser power obtained from the molten pool image. The control signal controls the laser power and scanning speed in real time during the laser selective melting process, realizing the closed-loop control of SLM. Attached Figure Description

[0025] Figure 1 This is an optical path diagram of the coaxial SLM real-time monitoring and real-time feedback control device of the present invention.

[0026] Figure 2 This is a flowchart of the coaxial SLM real-time monitoring and real-time feedback control method of the present invention.

[0027] In the picture:

[0028] 1. Coaxial monitoring optical path module; 2. High-speed camera; 3. Second filter; 4. Second beam combiner; 5. Scanning galvanometer; 6. Semiconductor laser; 7. Laser optical path module; 8. Processed surface; 9. Field lens; 10. First beam combiner; 11. Collimating lens; 12. Optical fiber; 13. Laser; 14. Temperature signal processor; 15. Computer; 16. High-speed camera controller; 17. Feedback control module; 18. Infrared thermal imager; 19. First filter. Detailed Implementation

[0029] The present invention will be further explained and described below with reference to the accompanying drawings and specific embodiments. It should be noted that the specific embodiments are not intended to limit the scope of the present invention.

[0030] In the description of this invention, it should be understood that the terms "vertical," "horizontal," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature.

[0031] like Figure 1 As shown in the figure, the coaxial SLM real-time monitoring and feedback control device provided in this specific embodiment includes a laser optical path module, a coaxial monitoring optical path module, and a feedback control module. The laser optical path module 7 is used to receive signals from the computer 15 to generate a high-energy laser with a preset power and focus it onto the processing surface 8 for SLM processing. The infrared molten pool self-luminescence generated during SLM processing and the laser light reflected from the semiconductor laser 6 of the coaxial monitoring optical path module 1 on the processing surface 8 enter the laser optical path module 7 and are reflected into the coaxial monitoring optical path module 1.

[0032] The coaxial monitoring optical path module 1 is used to receive the infrared band molten pool self-luminescence generated on the processing surface 8 during the processing process and the reflected light of the laser generated by the semiconductor laser 6 on the processing surface 8 transmitted by the laser optical path module 7, so as to form visible light imaging and infrared thermal imaging.

[0033] The feedback control module 17 is used to receive the real-time SLM processing melt pool temperature distribution and melt pool image obtained by the coaxial monitoring optical path module 1, store the data, analyze the data, generate feedback control signals and transmit them to the laser optical path module 7, and at the same time, real-time correspondence between the ROI areas of the melt pool temperature distribution and melt pool image data and the corresponding processing positions on the path and the three-dimensional model and display them in real time.

[0034] Specifically, the laser optical path module 7 includes a laser 13, an optical fiber 12, a collimating lens 11, a first beam combiner 10, a scanning galvanometer 5, and a field lens 9, and the coaxial monitoring optical path module 1 includes a semiconductor laser 6, a second beam combiner 4, an infrared thermal imager 18, a high-speed camera 2, a first filter 19, and a second filter 3. The feedback control module 17 includes a high-speed camera controller 16, a temperature signal processor 14, and a computer 15. The high-speed camera controller 16, the temperature signal processor 14, the laser 13, and the scanning galvanometer 5 are electrically connected to the computer 15. The computer 15 generates a laser control signal to control the laser 13 to generate a high-energy laser with a preset power of 1080nm wavelength, which is transmitted through the optical fiber 12 to the collimating lens 11. The collimating lens 11 collimates the 1080nm high-energy laser with a preset power of 1080nm wavelength at a fixed divergence angle and then transmits it to the first beam combiner 10. The first beam combiner 10 transmits the 1080nm high-energy laser with a preset power of 1080nm wavelength generated by the laser 13 with a transmittance of more than 99.9%. The computer 15 generates a control signal to control the scanning galvanometer 5 to reflect the 1080nm high-energy laser with a preset power of 1080nm wavelength transmitted by the first beam combiner 10 to a designated position on the processing surface 8, and then focuses the 1080nm high-energy laser with a preset power of 1080nm wavelength onto the metal powder on the processing surface through the field lens 9. The field lens 9 serves two purposes: first, it focuses a high-energy laser in the 1080nm band onto the processing surface 8; second, it transmits the reflected light from the 450nm and 810-920nm band molten pool self-luminescence generated by the processing surface 8 and the 450nm band laser generated by the semiconductor laser 6 onto the processing surface 8, with a transmittance exceeding 95%, of which the transmittance of the 1080nm band high-energy laser exceeds 99%.

[0035] A semiconductor laser 6 is mounted above the processing surface. When the field mirror 9 focuses a high-energy laser with a preset power of 1080nm onto the metal powder on the processing surface 8, the metal powder on the processing surface 8 melts rapidly to form a molten pool. Simultaneously, a 450nm wavelength laser generated by the semiconductor laser 6 is irradiated onto the processing surface 8. During the processing, the mixed beam of laser light generated by the semiconductor laser 6 and irradiated onto the processing surface 8, reflected from the processing surface 8, and the self-luminous light from the molten pool, enters the laser optical path module through the field mirror 9. It then passes through the field mirror 9 and is reflected by the scanning galvanometer 5 to the first beam combiner 10. The first beam combiner 10 reflects the mixed beam of the 450nm laser light from the processing surface 8, the 810-920nm wavelength self-luminous light from the molten pool, and the high-power 450nm laser light generated by the semiconductor laser 6 onto the processing surface 8, and enters the coaxial monitoring optical path module 1. The reflectivity exceeds 90%. The semiconductor laser 6 is used to generate a high-power 450nm laser during the printing process of the laser optical path module 7. The high-power 450nm laser light reflected from the metal powder and the molten pool on the processing surface 8 is reflected by the laser optical path module 7 into the coaxial monitoring optical path module 1 for visible light imaging.

[0036] The second beam combiner 4, the second filter 19, and the high-speed camera 2 are arranged sequentially from bottom to top in the vertical direction of the first beam combiner 10. The second beam combiner 4 receives a mixed beam of light reflected from the first beam combiner 10 onto the processing surface 8, consisting of 450nm and 810-920nm band molten pool self-luminous light and high-power 450nm band laser light generated by the semiconductor laser 6. The second beam combiner 4 transmits the reflected light from the 450nm band molten pool self-luminous light and the high-power 450nm band laser light generated by the semiconductor laser 6 to the second filter 3. The second filter 3 is a single-pass filter for the 450nm band with a transmittance exceeding 99%. The light is then transmitted to the high-speed camera 2 through the second filter 3 to ensure that the high-speed camera 2 avoids potential reflected laser radiation and the influence of reflected light radiation from other bands in the camera's spectrum. The high-speed camera 2 is required to have a pixel resolution of no less than 1920×1080, a frame rate of no less than 2247 frames per second at full resolution, a dynamic range of 56dB, and four CoaXPress2.0 data transmission interfaces with a total data transmission speed of 50Gbps. The high-speed camera 2 is used for visible light imaging of the processing area. The high-speed camera 2 is connected to a high-speed camera controller 16, which includes a high-speed camera control module, an image processing module, and a data transfer module. The high-speed camera control module is connected to a computer 15 and the image processing module, the image processing module is connected to the data transfer module, and the data transfer module is connected to the computer 15.

[0037] The high-speed camera controller 16 is used to acquire and transfer the melt pool image data transmitted from the high-speed camera 2, process the data to obtain the ROI region, and transmit the processed melt pool image data to the computer 15.

[0038] The high-speed camera control module is used to receive the parameters of the high-speed camera 2 output by the computer 15, set the parameters of the high-speed camera 2, control and save the real-time data of the molten pool acquired by the high-speed camera 2.

[0039] The image processing module is used to crop the image with the laser spot position as the image center to obtain the ROI region.

[0040] The data transfer module is used to transfer image data to the image processing module in real time and store the processed image data in the computer 15.

[0041] The computer 15 is used to receive and store real-time data generated by the high-speed camera 2 and the infrared thermal imager 18 during the SLM processing and to provide real-time feedback control to the scanning galvanometer 5 and the laser 13. Before the SLM processing begins, the high-speed camera 2 records parameters and a start signal, which are transmitted to the high-speed camera controller 16. The infrared thermal imager 18 records parameters and a start signal, which are transmitted to the temperature signal processor 14. The galvanometer control signal is output to the scanning galvanometer 5, and the laser control signal is output to the laser 13. The SLM processing begins. During the processing, the computer receives real-time data processed by the high-speed camera controller 16 and the infrared thermal imager 18. After image analysis and processing, laser power and scanning speed control signals are generated and transmitted to the laser 13 and the scanning galvanometer 5, respectively, to realize real-time feedback control of the SLM processing. The computer also maps the temperature distribution ROI area obtained by the infrared thermal imager 18 and the image data ROI area obtained by the high-speed camera 2 to the corresponding processing positions on the single-layer path and the three-dimensional model, and displays them in real time.

[0042] The first filter 19 and the infrared thermal imager 18 are respectively positioned from left to right in the horizontal direction of the second beam combiner 4. The first filter 19 is a narrowband filter in the 810-920nm band with a transmittance of over 99%. The second beam combiner 4 receives the self-emitted light from the 810-920nm band molten pool on the processing surface reflected by the first beam combiner 4 and transmits it to the first filter 19, with a reflectance of over 99%. The light is then transmitted from the first filter 19 to the infrared thermal imager 18, ensuring that the infrared thermal imager 18 avoids the influence of possible reflected laser radiation and improves the accuracy of temperature distribution monitoring. The infrared thermal imager 18 is required to have a pixel resolution of no less than 640×480, a frame rate of no less than 60 frames / second under full resolution conditions, a spectral range of 810-920nm, and sub-temperature ranges of 800-1150℃, 1000-1500℃, 1350-2050℃, and 1900-3000℃. The infrared thermal imager 18 is used for infrared imaging of the processing area and for acquiring the temperature distribution of the processing area. The infrared thermal imager 18 is connected to a temperature signal processor 14, which includes a thermal imager control module, a temperature distribution processing module, and a data storage module. The thermal imager control module is connected to a computer 15 and the temperature distribution processing module, the temperature distribution processing module is connected to the data storage module, and the data storage module is connected to the computer 15.

[0043] The temperature signal processor 14 is used to receive temperature distribution data transmitted from the infrared thermal imager 18, process the data to obtain the ROI region, and store the processed temperature distribution data in the computer 15.

[0044] The thermal imager control module is used to receive the start / stop signals output by the computer 15 and control the thermal imager to acquire the real-time temperature distribution of the molten pool.

[0045] The temperature distribution processing module is used to cut the data center of the molten pool based on the laser spot position to obtain the ROI region.

[0046] The data storage module is used to store temperature distribution data into computer 15.

[0047] Working principle:

[0048] The feedback control module 17 sends control signals to control the scanning galvanometer 5, laser 13, high-speed camera 2, and infrared thermal imager 18 to perform SLM processing. The computer 15 controls the laser 13 to generate a high-energy laser with a preset power, which is transmitted through the optical fiber 12 to the collimating lens 11. After being collimated by the collimating lens 11, it is transmitted to the first beam combiner 10. The first beam combiner 10 reflects the high-energy laser with the preset power to a designated position on the processing surface 8. Then, it is focused onto the metal powder on the processing surface 8 by the field lens 9, so that the metal powder on the processing surface 8 melts rapidly to form a molten pool and generates self-luminescence in the molten pool on the processing surface 8. At the same time, the semiconductor laser 6 is manually controlled to emit laser light to irradiate the metal powder on the processing surface 8. The laser light emitted by the semiconductor laser 6 is reflected on the processing surface 8 to form reflected light. The mixed beam of laser light reflected from the semiconductor laser 6 on the processing surface 8 and the infrared band molten pool self-luminescence enters the laser optical path module 7. After passing through the scanning galvanometer 5 and the first beam combiner 10, the corresponding band is totally reflected to the coaxial monitoring optical path module 1. Then, through the second beam combiner 4, the infrared band molten pool self-luminescence on the processing surface 8 is transmitted to the infrared thermal imager 18, and the molten pool self-luminescence and the reflected light from the semiconductor laser 6 on the processing surface 8 are transmitted to the high-speed camera 2 for synchronous imaging. The feedback control module 17 processes and stores the temperature data from the infrared thermal imager 18 and the data from the high-speed camera 2 in real time. Combining the two multi-source data, the processing parameters are adjusted in real time, and control signals are generated in real time to adjust the scanning galvanometer 5 and the laser 13 to change the scanning speed and laser power, thus completing the coaxial SLM high-speed and real-time temperature distribution monitoring and real-time feedback control.

[0049] like Figure 2 As shown in the figure, this specific embodiment also provides a control method for a coaxial SLM real-time monitoring and real-time feedback control device, including the following steps:

[0050] Step 1: During SLM printing, the feedback control module controls the high-speed camera and infrared thermal imager to start recording, and controls the laser to emit a laser of preset power and controls the scanning speed and scanning path of the scanning galvanometer. The laser of preset power is reflected by the collimating lens, the first beam combiner and the scanning galvanometer in sequence and then focused onto the metal powder on the processing surface by the field lens, so that the metal powder on the processing surface melts rapidly to form a molten pool. At the same time, the laser generated by the semiconductor laser is irradiated onto the molten pool area on the processing surface.

[0051] Step 2: During the processing, the high-power 450nm laser reflected light generated by the semiconductor laser on the processing surface in Step 1, mixed with the molten pool self-luminescence in the 450nm and 810-920nm bands, enters the laser optical path module through the field lens, and then is reflected by the scanning galvanometer to the first beam combiner. The first beam combiner reflects the light to the second beam combiner. The second beam combiner reflects the molten pool self-luminescence in the 810-920nm band of the mixed beam to the first filter and then transmits it to the infrared thermal imager for coaxial molten pool temperature distribution imaging. At the same time, the molten pool self-luminescence in the 450nm band and the high-power 450nm laser reflected light generated by the semiconductor laser are transmitted to the second filter and then transmitted to the high-speed camera for coaxial molten pool area imaging.

[0052] Step 3: The high-speed camera controller 16 of the feedback control module 17 processes the molten pool area image of the high-speed camera 2 in real time. The image processing module 24 crops the molten pool area image with the laser spot position as the center to obtain the ROI area image. The data transfer module 25 stores the ROI area image into the computer 15. The temperature signal processor 14 of the feedback control module 17 processes the molten pool temperature distribution data of the infrared thermal imager 18 in real time. The temperature distribution processing module 21 crops the molten pool temperature distribution data with the laser spot position as the center to obtain the ROI area temperature distribution. The data storage module 22 stores the ROI area temperature distribution into the computer 18.

[0053] Step 4: The computer 15 simultaneously receives and stores the ROI region image and ROI region temperature distribution transmitted from the high-speed camera controller 16 and the temperature signal processor 14. It then maps the ROI region image and ROI region temperature distribution from Step 3 to the corresponding processing positions on the single-layer path and the 3D model, displaying them in real time. Simultaneously, it analyzes whether there are any anomalies in the molten pool temperature distribution and temperature gradient. Combining this with anomaly analysis of the molten pool fluctuation state, molten pool morphology, molten pool splash, and surrounding powder distribution at the same moment, it determines whether a feedback control signal should be generated. The method for determining whether a feedback control signal should be generated includes the following steps:

[0054] Step 41: When the feedback control module determines that there are no abnormalities in the image and temperature distribution of the molten pool area during the SLM processing, it will continue to use the current printing process parameters by default.

[0055] Step 42: When the feedback control module determines that there is an abnormality in the image or temperature distribution of the molten pool area during the SLM processing, it generates a feedback control signal, adjusts the output laser power of the laser and the scanning speed of the scanning galvanometer in real time, and continues printing until the entire part is printed layer by layer.

[0056] In step 42, when there is a lot of molten pool spatter in the molten pool area or the molten pool temperature distribution gradient is large or uneven, the computer 15 determines, in conjunction with the changes in the molten pool morphology, to appropriately reduce the laser power or increase the scanning speed, so as to ultimately ensure that the laser energy density is within an appropriate range.

[0057] When the molten pool exhibits severe spheroidization or the molten pool temperature distribution is significantly lower than the threshold or the gradient is low, the computer 15, in conjunction with changes in the molten pool morphology, determines whether to appropriately increase the laser power or decrease the scanning speed. Ultimately, this ensures that the laser energy density remains within an appropriate range. Then, based on the printing parameters controlled by real-time feedback, the SLM processing runs normally until the entire part is printed layer by layer.

[0058] In conjunction with the above embodiments, this invention adds a coaxial monitoring optical path module to the laser optical path of SLM processing, and uses a semiconductor laser as an auxiliary light source to realize coaxial status monitoring of SLM processing. This includes using a high-speed camera 2 to acquire images of the molten pool area, and an infrared thermal imager 18 to acquire the temperature distribution of the molten pool. The high-speed camera controller 16 and the temperature signal processor 14 store and process the above molten pool status data in real time. The computer 15 further analyzes and processes the data and displays it in real time for users to analyze the printing process online. At the same time, it generates real-time feedback control signals to adjust the laser power and scanning speed in real time during processing, thereby realizing real-time feedback control of the SLM processing process, avoiding serious quality defects, and improving the stability of the SLM process.

Claims

1. A coaxial SLM real-time monitoring and real-time feedback control device, characterized in that, The system includes a feedback control module, a laser optical path module, and a coaxial monitoring optical path module. The laser optical path module includes a laser, a collimating lens, a first beam combiner, a scanning galvanometer, and a field lens. The laser and the scanning galvanometer are respectively connected to the feedback control module. The collimating lens is connected to the laser via an optical fiber. The feedback control module controls the laser to generate a laser with a preset power. After being collimated by the collimating lens, the laser passes through the first beam combiner. The feedback control module controls the scanning galvanometer to reflect the laser transmitted through the first beam combiner to a designated position on the processing surface, and then focuses it onto the processing surface through the field lens. The coaxial monitoring optical path module includes a second beam combiner, an infrared thermal imager, a high-speed camera, a first filter, a second filter, and a semiconductor laser. The second beam combiner, the second filter, and the high-speed camera are respectively arranged in the vertical direction of the first beam combiner. The first filter and the infrared thermal imager are respectively arranged in the horizontal direction of the second beam combiner. The high-speed camera and the infrared thermal imager are respectively connected to the feedback control module. The semiconductor laser is installed above the processing surface, and the laser generated by the semiconductor laser irradiates the processing surface. The feedback control module includes a high-speed camera controller, a temperature signal processor, and a computer. The high-speed camera controller, temperature signal processor, laser, and scanning galvanometer are respectively connected to the computer. The first filter is a narrowband filter with a wavelength range of 810-920nm and a transmittance of over 99%; the second filter is a single-pass filter with a wavelength of 450nm and a transmittance of over 99%; the semiconductor laser generates 450nm wavelength laser and the laser generates 1080nm wavelength high-energy laser.

2. The coaxial SLM real-time monitoring and real-time feedback control device according to claim 1, characterized in that, The high-speed camera is connected to the high-speed camera controller, and the infrared thermal imager is connected to the temperature signal processor.

3. The coaxial SLM real-time monitoring and real-time feedback control device according to claim 2, characterized in that, The high-speed camera controller includes a high-speed camera control module, an image processing module, and a data transfer module. The high-speed camera control module is connected to both the computer and the image processing module. The image processing module is connected to the data transfer module, and the data transfer module is connected to the computer. The temperature signal processor includes a thermal imager control module, a temperature distribution processing module, and a data storage module. The thermal imager control module is connected to both the computer and the temperature distribution processing module. The temperature distribution processing module is connected to the data storage module, and the data storage module is connected to the computer.

4. The control method of a coaxial SLM real-time monitoring and real-time feedback control device as described in any one of claims 1 to 3, characterized in that, The steps include the following: Step 1: During SLM printing, the feedback control module controls the high-speed camera and infrared thermal imager to start recording, and controls the laser to emit a laser of preset power and controls the scanning speed and scanning path of the scanning galvanometer. The laser of preset power is reflected by the collimating lens, the first beam combiner and the scanning galvanometer in sequence and then focused onto the metal powder on the processing surface by the field lens, so that the metal powder on the processing surface melts rapidly to form a molten pool. At the same time, the laser generated by the semiconductor laser is irradiated onto the molten pool area on the processing surface. Step 2: During the processing, the mixed beam of laser reflection light in the 450nm band generated by the semiconductor laser on the processing surface in Step 1 and the self-luminous light of the molten pool in the 450nm and 810-920nm bands enters the laser optical path module through the field lens, and then is reflected by the scanning galvanometer through the field lens to the first beam combiner. The first beam combiner reflects the light to the second beam combiner. The second beam combiner reflects the self-luminous light of the molten pool in the 810-920nm band of the mixed beam to the first filter and then transmits it to the infrared thermal imager for coaxial molten pool temperature distribution imaging. At the same time, the self-luminous light of the molten pool in the 450nm band and the laser reflection light in the 450nm band generated by the semiconductor laser are transmitted to the second filter and then transmitted to the high-speed camera for coaxial molten pool area imaging. Step 3: The feedback control module processes the molten pool area image from the high-speed camera and the molten pool temperature distribution data from the infrared thermal imager in real time, and crops the molten pool area image with the laser spot position as the center, obtains and stores the ROI area image, and crops the molten pool temperature distribution data with the laser spot position as the center, obtains and stores the ROI area temperature distribution. Step 4: The ROI region image and ROI region temperature distribution from Step 3 are mapped to the corresponding processing positions on the single-layer path and the 3D model and displayed in real time through the feedback control module. At the same time, the temperature distribution and temperature gradient of the molten pool are analyzed to see if there are any abnormalities. Combined with the analysis of abnormalities in the molten pool fluctuation state, molten pool morphology, molten pool splash and surrounding powder distribution at the same moment, it is determined whether to generate a feedback control signal.

5. The control method of the coaxial SLM real-time monitoring and real-time feedback control device according to claim 4, characterized in that, The method for determining the generated feedback control signal includes the following steps: Step 41: When the feedback control module determines that there are no abnormalities in the image and temperature distribution of the molten pool area during the SLM processing, it will continue to use the current printing process parameters by default. Step 42: When the feedback control module determines that there is an abnormality in the image or temperature distribution of the molten pool area during the SLM processing, it generates a feedback control signal, adjusts the output laser power of the laser and the scanning speed of the scanning galvanometer in real time, and continues printing until the entire part is printed layer by layer.

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