Heat conduction on-line monitoring system based on forming micro-area and support-free forming method
By building an online monitoring system for heat conduction of forming micro-zone heat conduction in laser selection molten metal additive manufacturing, monitoring and adjusting the heat input of forming micro-zone, the problems of heat accumulation and overheating during the formation of complex structures are solved, and unsupported forming is achieved, reducing production costs and expanding forming properties.
Patent Information
- Application Number
- CN202411971459.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-30
- Publication Date
- 2025-04-25
AI Technical Summary
In laser selection molten metal additive manufacturing, during the forming process of complex structures, due to low thermal conductivity, the forming micro-zone is prone to heat accumulation and overheating, resulting in increased stress gradients. Support structures need to be added to prevent stress deformation, but this increases production costs and limits forming properties.
The online monitoring system for heat conduction of forming micro-zones built based on CMOS cameras, photodiodes, thermal imagers, etc. is adopted to monitor the radiation intensity and morphology of the forming micro-zone, obtain temperature information, and modify the laser power and scanning speed through feedback from the control module, adjust the heat input, and control the temperature gradient to achieve unsupported forming.
It realizes that the temperature gradient of the forming micro-zone is controlled without adding a support structure, avoiding heat accumulation and overheating, reducing production costs, and expanding the formability of the laser selection melting technology.
Smart Images
Figure CN119870520A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of laser selective melting metal additive manufacturing, in particular to an online monitoring system based on heat conduction in a forming micro-area and a support-free forming method. Background Art
[0002] In recent years, with the rapid growth of market demand, especially the demand for large-scale complex structural parts manufacturing in the aerospace field, laser selective melting metal additive technology has developed rapidly due to its characteristics of forming complex and fine structures, short forming process, and strong adaptability of the formed part size range. The parts produced have also shifted from rapid trial production to actual terminal parts, and from single-piece and small batches to medium-batch production.
[0003] Since the laser selective melting metal additive technology uses a high energy density and small spot to process the powder bed, the material heating rate and cooling rate are very high during the process, and it is extremely cold and hot, and the temperature gradient in the forming micro-area is high. Relatively speaking, when forming regular parts, its heat conduction mainly relies on the solid part that has been formed in the previous order, with high heat conduction efficiency, and no heat accumulation and overheating will occur, so there is no need to add support structures. Due to changes in the actual structural characteristics of parts, such as cantilevers, small angles, long bridges, and large-sized horizontal holes, the forming process mainly relies on the lower layer of powder for heat conduction, and the thermal conductivity efficiency is low. As a result, under the same laser energy input conditions, heat accumulation will occur in the micro-area, resulting in overheating, an increase in temperature gradient, and a large stress gradient.
[0004] In order to prevent stress deformation, support structures need to be added. However, the use of support as an auxiliary structure has the following shortcomings: on the one hand, the added support structure needs to be removed in the post-processing stage, which increases the workload, the consumption of powder materials, the forming time, and the production cost of the parts; on the other hand, some structures such as internal flow channels and closed cavities cannot remove the internal support structure after forming, which limits the addition of support and also limits the formability of this type of parts using laser selective melting technology. Summary of the invention
[0005] The present invention provides an online monitoring system based on heat conduction in a forming micro-area and a support-free forming method. The present invention builds a forming micro-area online monitoring system based on a CMOS camera, a photodiode, a thermal imager, etc., obtains its temperature information by comprehensively monitoring the radiation intensity of the forming micro-area, the morphology of the forming micro-area and other characteristics, and modifies the input laser power and scanning speed through feedback from a control module to adjust the heat input to the forming micro-area, control the temperature gradient of the forming micro-area and its adjacent micro-areas, and realize support-free forming.
[0006] In a first aspect, an online monitoring system based on heat conduction in a formed micro-area is provided, comprising a working plane, a laser light source, a spectroscope 1, a spectroscope, an x-galvanometer, a y-galvanometer, a first photodiode, and a CMOS camera;
[0007] The laser light from the laser light source is reflected by the beam splitter 1 to the x-galvanometer, and then the laser light is further reflected by the y-galvanometer and projected into the working plane, thereby completing the part forming on the working plane;
[0008] The light spot of the forming micro-area on the working plane emits light, which passes through the y galvanometer and the x galvanometer and then enters the beam splitter 1; the beam splitter 1 allows this light to pass through so that the light continues to enter the beam splitter 2; the beam splitter 2 is used to split the light into two, one path enters the first photodiode, and the other path enters the CMOS camera; the CMOS camera and the first photodiode are used to complete the coaxial online monitoring of the forming micro-area of the part product to track the light spot of the forming micro-area; the first photodiode is used to monitor the radiation intensity of the forming micro-area of the part product; the CMOS camera is used to monitor the melting and solidification morphology of the forming micro-area of the part product.
[0009] In combination with the first aspect, in certain implementations of the first aspect, the online monitoring system includes a control module; the control module receives signals collected by the CMOS camera and the first photodiode, and when the temperature is too high, the control module feedback modifies the input laser power and / or scanning speed to control the heat input to the forming micro-area and control the temperature gradient of the forming micro-area and its adjacent micro-areas; wherein, when the temperature is too high, the laser power is reduced and / or the scanning speed is increased; when the temperature is too low, the laser power is increased and / or the scanning speed is reduced.
[0010] In combination with the first aspect, in some implementations of the first aspect, the first photodiode is used to convert the collected signal into a grayscale value and input it into the control module for processing as temperature information.
[0011] In combination with the first aspect, in certain implementations of the first aspect, the online monitoring system also includes a thermal imager and a second photodiode; the thermal imager and the second photodiode are used to complete off-axis online monitoring of the formed micro-area, and to fixedly detect the temperature change of the micro-area when the standard sample is formed to establish a benchmark; the second photodiode is used to monitor the radiation intensity of the formed micro-area of the standard sample; and the thermal imager is used to monitor the temperature of the formed micro-area of the standard sample.
[0012] In combination with the first aspect, in certain implementations of the first aspect, by comparing the signals of the first photodiode and the second photodiode, the temperature comparison of the micro-area of the part product and the standard sample forming is determined, so that the temperature of the micro-area of the part product forming is controlled based on the standard sample forming.
[0013] In combination with the first aspect, in some implementations of the first aspect, the first photodiode and / or the second photodiode is selected to capture a wavelength of 400 nm-950 nm.
[0014] In combination with the first aspect, in some implementations of the first aspect, the CMOS camera is selected to capture a wavelength of 400nm-900nm.
[0015] In combination with the first aspect, in some implementations of the first aspect, the selection requirement of the thermal imager is a resolution of not less than 1 mm*1 mm.
[0016] In a second aspect, a support-free forming method is provided, comprising:
[0017] Building an online monitoring system as described in any one of the implementations of the first aspect above;
[0018] Preliminary selection of laser forming parameters for parts;
[0019] When forming the part begins, the control module collects the characteristics of the forming micro-area through the online monitoring system to obtain the temperature information of the forming micro-area;
[0020] When a certain position of the formed part is reached, the online monitoring system collects signals indicating that the temperature of the formed micro-area is too low or too high;
[0021] The input laser power and scanning speed are modified through feedback from the control module to adjust the heat input to the forming micro-area, control the temperature gradient of the forming micro-area and its adjacent micro-areas, and continue the forming after the adjustment;
[0022] Complete part forming.
[0023] Compared with the prior art, the solution provided by the present invention includes at least the following beneficial technical effects:
[0024] The present invention builds an online monitoring system based on a CMOS camera, a first photodiode, a second photodiode, a thermal imager, etc., and obtains the temperature information of the forming micro-area by comprehensively monitoring the radiation intensity of the forming micro-area, the morphology of the forming micro-area, etc. Afterwards, the control module modifies the input laser power and scanning speed based on the temperature information feedback to adjust the heat input to the forming micro-area, control the temperature gradient of the forming micro-area and its adjacent micro-areas, and realize support-free forming. BRIEF DESCRIPTION OF THE DRAWINGS
[0025] Figure 1 Schematic diagram of the coaxial online monitoring part of the online monitoring system based on heat conduction in the forming micro-area.
[0026] Figure 2 Schematic diagram of off-axis online monitoring.
[0027] Figure 3 Schematic diagram of the principle of heat input and output balance control based on forming micro-area. DETAILED DESCRIPTION
[0028] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.
[0029] Figure 1 An online monitoring system based on heat conduction in a forming micro-area is shown. The system includes a working plane, a laser light source, a beam splitter 1, a beam splitter, an x-galvanometer, a y-galvanometer, a first photodiode, a CMOS camera and a control module. The laser light emitted by the laser light source is reflected to the x-galvanometer by the beam splitter 1, and the laser light is further reflected by the y-galvanometer and injected into the working plane, thereby completing the part forming on the working plane.
[0030] The light spot of the forming micro-area on the working plane emits light, which passes through the y galvanometer and the x galvanometer and then enters the beam splitter 1. Beam splitter 1 allows this light to pass through so that the light continues to enter the beam splitter 2. Beam splitter 2 is used to split the light into two, one path enters the first photodiode, and the other enters the CMOS camera. Through the above-mentioned online monitoring system based on heat conduction in the forming micro-area, the CMOS camera and the first photodiode can be used to complete the coaxial online monitoring of the forming micro-area of the part product. The first photodiode can be used to monitor the radiation intensity of the forming micro-area of the part product. The CMOS camera can be used to monitor the morphology of the forming micro-area.
[0031] The coaxial online monitoring part includes a photodiode and a high-speed camera. The coaxial online detection accurately obtains the radiation intensity of the forming micro-area by tracking the spot position, and converts it into a grayscale value and inputs it into the control module for processing as temperature information; the CMOS camera tracks and photographs the melting and solidification of the forming micro-area. The control module can receive the signals collected by the CMOS camera and the first photodiode. When the temperature is too high, the control module can feedback and modify the input laser power and scanning speed to reduce the heat input to the forming micro-area and control the temperature gradient of the forming micro-area and its adjacent micro-areas.
[0032] In some embodiments, Figure 2 As shown, the online monitoring system based on heat conduction of the formed micro-area can also include a thermal imager and a second photodiode. The thermal imager and the second photodiode can be used to complete the off-axis online monitoring of the formed micro-area, and the temperature change of the micro-area when the standard sample is formed is fixedly detected to establish a benchmark. The second photodiode can be used to monitor the radiation intensity of the formed micro-area of the standard sample. The thermal imager can be used to monitor the temperature of the formed micro-area of the standard sample.
[0033] The online monitoring system can include two main parts: coaxial online monitoring and off-axis online monitoring. By comparing the signals of coaxial and off-axis photodiodes, the temperature change of micro-area during the actual part forming can be analyzed in real time, thus providing a basis for its temperature control (heat input value).
[0034] In some embodiments, the first photodiode and / or the second photodiode are selected to capture a wavelength of 400 nm-950 nm.
[0035] In some embodiments, the CMOS camera is selected to capture wavelengths of 400nm-900nm.
[0036] In some embodiments, the selection requirement of the thermal imager is that the resolution is not less than 1mm*1mm.
[0037] Figure 3 The schematic diagram is based on the principle of heat input and output balance control of the forming micro-area. During the part forming process, the online monitoring system of heat conduction in the forming micro-area collects the radiation intensity of the forming micro-area, the morphology of the forming micro-area and other characteristics to obtain temperature information, and analyzes the degree of change of the micro-area temperature during the actual part forming in real time. The input laser power and scanning speed are modified through feedback from the control module to adjust the temperature (heat input value) of the forming micro-area and control the temperature gradient of the forming micro-area and its adjacent micro-areas. When the temperature is too high, reduce the laser power and / or increase the scanning speed; when the temperature is too low, increase the laser power and / or reduce the scanning speed.
[0038] The following two embodiments introduce the unsupported forming method based on the application of the forming micro-area heat conduction online monitoring system provided by the present invention.
[0039] Example 1
[0040] ①Based on Figure 1 and Figure 2 , build an online monitoring system for the forming micro-area;
[0041] ② Preliminary selection of laser forming parameters for parts, including: laser power 380w, scanning speed 1.25m / s;
[0042] ③ When forming the parts, the control module collects the radiation intensity and morphology of the forming micro-area through the coaxial online monitoring system and the off-axis online monitoring system to obtain the temperature information;
[0043] ④ When the forming angle is 25° without supporting structure, the online monitoring system collects signals indicating that the temperature of the forming micro-area is too high;
[0044] ⑤ The input laser power and scanning speed are modified through feedback from the control module to reduce the heat input to the forming micro-area and control the temperature gradient of the forming micro-area and its adjacent micro-areas; the control module adjusts the laser forming parameters, including: the laser power is 320w, and the scanning speed is 1.50m / s to continue to complete the forming of the area and the adjacent areas;
[0045] ⑥Complete part forming.
[0046] Example 2
[0047] ①Based on Figure 1 and Figure 2 , build an online monitoring system for the forming micro-area;
[0048] ② Preliminary selection of laser forming parameters for parts, including: laser power 350w, scanning speed 1.25m / s;
[0049] ③ When forming the parts, the control module collects the radiation intensity and morphology of the forming micro-area through the coaxial online monitoring system and the off-axis online monitoring system to obtain the temperature information;
[0050] ④When the formed part is at a certain position, the online monitoring system collects signals indicating that the temperature of the forming micro-area is too low;
[0051] ⑤ The input laser power and scanning speed are modified through feedback from the control module to reduce the heat input to the forming micro-area and control the temperature gradient of the forming micro-area and its adjacent micro-areas; the control module adjusts the laser forming parameters, including: the laser power is 390w, the scanning speed is 1.20m / s to continue forming;
[0052] ⑥Complete part forming.
[0053] Although the present invention is disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be based on the scope defined by the claims of the present invention.
Claims
1. Based on the online monitoring system of heat conduction in forming micro-area, it is characterized by: It includes a working plane, a laser light source, a beam splitter 1, a beam splitter, an x-galvanometer, a y-galvanometer, a first photodiode, and a CMOS camera; The laser light from the laser light source is reflected by the beam splitter 1 to the x-galvanometer, and then the laser light is further reflected by the y-galvanometer and projected into the working plane, thereby completing the part forming on the working plane; The light spot of the forming micro-area on the working plane emits light, which passes through the y galvanometer and the x galvanometer and then enters the beam splitter 1; the beam splitter 1 allows this light to pass through so that the light continues to enter the beam splitter 2; the beam splitter 2 is used to split the light into two, one path enters the first photodiode, and the other path enters the CMOS camera; the CMOS camera and the first photodiode are used to complete the coaxial online monitoring of the forming micro-area of the part product to track the light spot of the forming micro-area; the first photodiode is used to monitor the radiation intensity of the forming micro-area of the part product; the CMOS camera is used to monitor the melting and solidification morphology of the forming micro-area of the part product.
2. The online monitoring system according to claim 1, characterized in that: The online monitoring system includes a control module; the control module receives signals collected by a CMOS camera and a first photodiode, and when the temperature is too high, the control module feedback modifies the input laser power and / or scanning speed to control the heat input to the forming micro-area and the temperature gradient of the forming micro-area and its adjacent micro-areas; wherein, when the temperature is too high, the laser power is reduced and / or the scanning speed is increased; when the temperature is too low, the laser power is increased and / or the scanning speed is reduced.
3. The online monitoring system according to claim 1, characterized in that: The first photodiode is used to convert the collected signal into a gray value and input it into the control module for processing as temperature information.
4. The online monitoring system according to any one of claims 1 to 3, characterized in that: The online monitoring system also includes a thermal imager and a second photodiode; the thermal imager and the second photodiode are used to complete off-axis online monitoring of the formed micro-area, and to fixedly detect the temperature change of the micro-area when the standard sample is formed to establish a benchmark; the second photodiode is used to monitor the radiation intensity of the formed micro-area of the standard sample; the thermal imager is used to monitor the temperature of the formed micro-area of the standard sample.
5. The online monitoring system according to claim 4, characterized in that: By comparing the signals of the first photodiode and the second photodiode, the temperature comparison of the micro-region of the part product and the standard sample is determined, so that the temperature of the micro-region of the part product is controlled based on the standard sample forming.
6. The online monitoring system according to claim 4, characterized in that: The first photodiode and / or the second photodiode are selected to capture a wavelength of 400nm-950nm.
7. The online monitoring system according to claim 1, characterized in that: The CMOS camera was selected to capture wavelengths of 400nm-900nm.
8. The online monitoring system according to claim 1, characterized in that: The selection requirement for thermal imagers is a resolution of no less than 1mm*1mm.
9. A method for forming without support, characterized in that: include: Building an online monitoring system as claimed in any one of claims 1 to 9; Preliminary selection of laser forming parameters for parts; When forming the part begins, the control module collects the characteristics of the forming micro-area through the online monitoring system to obtain the temperature information of the forming micro-area; When a certain position of the formed part is reached, the online monitoring system collects signals indicating that the temperature of the formed micro-area is too low or too high; The input laser power and scanning speed are modified through feedback from the control module to adjust the heat input to the forming micro-area, control the temperature gradient of the forming micro-area and its adjacent micro-areas, and continue the forming after the adjustment; Complete part forming.