An auxiliary energy field elimination method for buckling deformation of an additively manufactured thin-walled structure

Abstract

This invention discloses an auxiliary energy field elimination method for buckling deformation of additively manufactured thin-walled structures, comprising: Step 1: setting up an auxiliary energy field system, including an external laser source with a Gaussian light distribution; Step 2: obtaining the correlation curves of laser spot diameter-current-temperature under different spot diameters and currents in the powder; Step 3: selecting a spot diameter such that the diameter of the heating area of ​​the external laser source is larger than the maximum cross-sectional dimension of the thin-walled structure to be formed; Step 4: based on the correlation of spot diameter-current-temperature, adjusting the current of the external laser source to change the temperature of the heating area, and using the external laser source to controllably irradiate and synchronously heat the selected area to achieve in-situ elimination of buckling deformation of the additively manufactured thin-walled structure. This invention can homogenize the structural temperature field of the printed area, reduce the temperature gradient and thermal stress amplitude, improve the dimensional accuracy and shape stability of the thin-walled structure, and achieve active control over the forming quality of the thin-walled structure.

Description

Technical Field

[0001] This invention belongs to the field of laser additive manufacturing and rapid prototyping technology, and specifically relates to an auxiliary energy field elimination method for buckling deformation of thin-walled structures manufactured by additive manufacturing. Background Technology

[0002] Additive manufacturing technology, due to its advantages such as high forming precision, high material utilization, and the ability to manufacture complex structures, is widely used in aerospace, biomedical, and high-end equipment manufacturing fields, such as aerospace frame structures, heat exchangers, and biomedical implants. Extreme lightweight structures typically focus on optimizing the specific strength and functional integration of the structure. Among these, thin-walled structures, due to their light weight and high specific strength, are of significant value in engineering applications. However, the reliable manufacturing of these key structures still faces serious challenges.

[0003] During additive manufacturing, the high temperature gradient around the molten pool and the repeated thermal cycling experienced by the formed part cause complex temperature and stress evolution, resulting in severe residual stress and subsequent structural deformation. Especially for thin-walled structures with low stiffness, thermal stress can easily exceed their critical stability condition during forming, leading to buckling deformation. This severely affects the dimensional accuracy, shape stability, and forming quality of the part, and may even cause the formed part to fail to meet the usage requirements.

[0004] To reduce the deformation of thin-walled structures during additive manufacturing, existing technologies mainly control it by optimizing scanning strategies, reducing energy density, or performing heat treatment after forming. However, adjusting process parameters alone cannot fundamentally improve the transient temperature field and thermal stress distribution during forming, and post-forming heat treatment cannot achieve in-situ suppression of buckling deformation, increasing manufacturing cycle and cost.

[0005] Therefore, there is an urgent need for a method that can precisely and controllably heat the forming area of ​​thin-walled structures during additive manufacturing. By regulating the temperature field distribution during the forming process, the temperature gradient and thermal stress can be reduced, thereby achieving in-situ suppression and elimination of buckling deformation of thin-walled structures and improving the forming accuracy of thin-walled structures. Summary of the Invention

[0006] To address the shortcomings and deficiencies of existing technologies, this invention proposes an auxiliary energy field elimination method for buckling deformation of additively manufactured thin-walled structures. This method aims to homogenize the structural temperature field in the printed area during the additive manufacturing process, reduce the temperature gradient and thermal stress amplitude, improve the dimensional accuracy and shape stability of the thin-walled structure, and achieve proactive control over the forming quality of the thin-walled structure.

[0007] The technical solution adopted in this invention is:

[0008] A method for eliminating the auxiliary energy field of buckling deformation in additively manufactured thin-walled structures includes the following steps:

[0009] Step 1: Set up an auxiliary energy field system, which includes an external laser source with a Gaussian light distribution;

[0010] Step 2: Based on the auxiliary energy field system in Step 1, obtain the correlation curves of spot diameter-current-temperature under different spot diameters and currents in the powder.

[0011] Step 3: Based on the cross-sectional area of ​​the thin-walled structure to be manufactured, set the auxiliary energy field heating area and select the spot diameter from Step 2 so that the diameter of the heating area of ​​the external laser source is larger than the maximum cross-sectional size of the thin-walled structure to be formed.

[0012] Step 4: Based on the relationship between spot diameter, current, and temperature in Step 2, the temperature of the heating area is changed by adjusting the current of the external laser source. In the process of additive manufacturing thin-walled structures, the selected area is controlled and synchronously heated by the external laser source to achieve in-situ elimination of buckling deformation of the additive manufacturing thin-walled structure.

[0013] Further, step one specifically involves: setting a fixed bracket on the outside of the side window of the laser powder bed melting and forming equipment, and installing an external laser light source emitter through the fixed bracket to form an auxiliary energy field system for the additive manufacturing thin-walled structure forming process.

[0014] Furthermore, in step two, thermocouples are used to measure the temperature at the center and edge of the heating area of ​​the powder under different spot diameters and different currents, thereby obtaining the correlation curve of spot diameter-current-temperature for powder under different spot diameters and currents.

[0015] Furthermore, in step two, multiple thermocouple probes are placed near the surface of the powder, an external laser light source is turned on, and the same spot diameter is maintained. The temperature at the center and edge of the heating area is measured under different currents. The spot diameter is changed, and the temperature at the center and edge of the heating area is measured again under different current conditions until the temperature under all the required spot diameters is measured. The measured temperature data are then processed to obtain multiple sets of spot diameter-current-temperature correlation curves.

[0016] Furthermore, in step two, while keeping the spot diameter the same, the current of the external laser source is gradually increased in increments of 0.5A when measuring the temperature at the center and edge of the heating area under different currents.

[0017] Furthermore, the diameter of the light spot includes 30mm and 50mm.

[0018] Furthermore, in step four, the current is adjusted based on the solidus temperature, powder sintering temperature, and microstructure phase transformation temperature of the material properties, thereby changing the temperature of the heating zone so that the center temperature is lower than the solidus temperature, powder sintering temperature, and microstructure phase transformation temperature.

[0019] Furthermore, in step four, the current is adjusted to change the temperature of the heating zone, so that the center temperature is between 40% and 50% of the powder sintering temperature.

[0020] Furthermore, in the process of additive manufacturing thin-walled structures, an external laser light source is used to controllably irradiate and synchronously heat a selected area; based on the powder state and powder temperature monitoring results, the current is dynamically adjusted in real time to ensure that the center temperature of the heating area fluctuates within 40%-50% of the powder sintering temperature.

[0021] Furthermore, during the additive manufacturing of thin-walled structures, an infrared camera is used to monitor the temperature of the heating zone in real time, and the current of the external laser source is dynamically adjusted accordingly. Specifically, when the heating temperature exceeds 50% of the powder sintering temperature, the current value is reduced; when the heating temperature is below 40% of the powder sintering temperature, the current value is increased, ensuring that the temperature of the heating zone fluctuates within the range of 40%-50% of the powder sintering temperature.

[0022] The beneficial effects of this invention are as follows: This invention can homogenize the structural temperature field of the printing area during additive manufacturing, reduce the temperature gradient and thermal stress amplitude, eliminate buckling deformation of thin-walled structures, improve the dimensional accuracy and shape stability of thin-walled structures, and achieve active control over the forming quality of thin-walled structures. By adjusting the current of the external laser light source, the temperature of the heating area is changed to ensure that the temperature is maintained at 40%-50% of the powder sintering temperature. Within this temperature range, on the one hand, the temperature gradient and thermal stress level on the powder bed surface can be effectively reduced, and on the other hand, sintering of the powder and significant phase transformation of the microstructure can be avoided, thereby suppressing buckling deformation of the thin-walled structure. The auxiliary energy field system reduces the temperature gradient and cooling rate during the forming process by increasing the reference temperature of the powder bed and the thin-walled structure. The reduction of the temperature gradient reduces the accumulation of thermal stress. When the thermal stress is always lower than the buckling critical stress of the thin-walled structure, the thin-walled structure does not experience geometric instability, thereby completely eliminating buckling deformation. At the same time, since the heating temperature is much lower than the phase transformation temperature and sintering temperature of the microstructure, the curing path and phase composition of the material remain unchanged.

[0023] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The invention will now be described in further detail with reference to the figures. Attached Figure Description

[0024] Figure 1 Diagram showing the composition and setup of the auxiliary energy field system;

[0025] Figure 2 This is a diagram showing the position and status of the thermocouple probe.

[0026] Figure 3 The graph shows the temperature change curves of the heating region under different currents when the object being heated is Ti-6Al-4V powder and the diameter of the external laser light source spot is 50 mm.

[0027] Figure 4 The graph shows the relationship between light spot diameter, current, and temperature for heating Ti-6Al-4V powder.

[0028] Figure 5 A diagram of the auxiliary energy field heating region;

[0029] Figure 6 The diagram shows the effect of in-situ elimination of buckling deformation in a thin-walled structure with a cross-sectional dimension of 30 mm × 30 mm.

[0030] Figure 7 The diagram shows the effect of in-situ elimination of buckling deformation in a thin-walled structure with a cross-sectional dimension of 34 mm × 6 mm.

[0031] Figure 8 This is a flowchart of an auxiliary energy field elimination method for buckling deformation of a thin-walled additive manufacturing structure according to the present invention. Detailed Implementation

[0032] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0033] See Figure 8 A method for eliminating the auxiliary energy field of buckling deformation in additively manufactured thin-walled structures, comprising:

[0034] Step 1: Set up an auxiliary energy field system, which includes an external laser source with a Gaussian light distribution and a fixed support, specifically:

[0035] See Figure 1 A fixed bracket is set on the outside of the side window of the Concept Laser M2 laser powder bed melting and forming equipment, and an emitter of an external Gaussian light source is installed through the fixed bracket to form an auxiliary energy field system.

[0036] The external laser source is model LWWD808-150F (Laserwave), with an output wavelength of 808 nm. By placing the external laser source outside the forming chamber, non-contact auxiliary heating of the forming area can be implemented without interfering with the normal operation of the original forming laser system, thereby forming an auxiliary energy field for the forming process of thin-walled structures in additive manufacturing.

[0037] Step 2: Based on the auxiliary energy field system in Step 1, determine the correlation curves of spot diameter-current-temperature under different spot diameters and currents in the powder, specifically as follows;

[0038] Step 2.1: Using Ti-6Al-4V powder as the heating object, the temperature of the heating area formed by an external laser light source was measured. During the measurement, the spot diameter of the external laser light source was kept at 50 mm, and the temperature change of the heating area under different current conditions was measured.

[0039] Specifically, a dual-channel thermocouple temperature probe was fixed near the surface of Ti-6Al-4V powder, with the probes positioned 1 mm from the powder's surface. Two thermocouple probes were located at the center of the laser spot and at the edge (25 mm from the center), respectively. An external laser source was turned on, and its initial current was adjusted to 1 A. After heating for 2 minutes to allow the temperature of the heated area to stabilize, the temperature values ​​at the center and edge of the laser spot were recorded. Figure 2 The position of the thermocouple probe is shown.

[0040] Step 2.3: While keeping the spot diameter constant, gradually increase the current of the external laser source in increments of 0.5 A until the current reaches 8.2 A. Record the temperature at the center and edge of the spot under each current condition. Obtain the current-temperature correlation curve for Ti-6Al-4V powder with a spot diameter of 50 mm.

[0041] See Figure 3 , Figure 4 The figure shows the temperature change curves of the heating area under different currents when the object being heated is Ti-6Al-4V powder and the diameter of the laser light source spot is 50 mm.

[0042] Step 2.4: Using Ti-6Al-4V powder as the heating object, reduce the spot diameter of the external laser source to 30 mm and measure the temperature change of the heated area under different current conditions. Two thermocouple temperature probes are positioned at the center of the laser spot and at the edge (15 mm from the center), respectively. Turn on the external laser source and adjust its initial current to 3 A. After maintaining heating for 2 minutes to allow the temperature of the heated area to stabilize, record the temperature values ​​at the center and edge of the laser spot. Gradually increase the current of the external laser source in increments of 0.5 A until the current reaches 8.2 A, and record the temperature at the center and edge of the laser spot under each current condition. Organize the measured temperature data to obtain the current-temperature correlation curve for Ti-6Al-4V powder as the heating object when the laser spot diameter is 30 mm. (See [link to relevant documentation]). Figure 4 , Figure 4As shown Figure 4 The above describes the correlation curve between spot diameter, current, and temperature for heating Ti-6Al-4V powder. Following the above description, other spot diameters can be set according to actual needs to obtain the correlation curves between spot diameter, current, and temperature for those different spot diameters.

[0043] Step 3: Based on the cross-sectional area of ​​the thin-walled structure to be manufactured, adjust the heating area of ​​the external laser source so that the laser spot diameter is larger than the maximum cross-sectional area of ​​the thin-walled structure to be formed, ensuring that the heating area can completely cover the forming area of ​​the thin-walled structure. Specifically:

[0044] See Figure 5 The cross-sectional dimensions of the thin-walled structure are 30 mm × 30 mm. The diameter of the heating area of ​​the external laser source is adjusted to 50 mm so that its diameter is larger than the cross-sectional dimensions of the thin-walled structure to be formed. The position of the external laser source is adjusted so that the heating area can completely cover the forming area of ​​the thin-walled structure.

[0045] Step 4: Based on the relationship between spot diameter, current, and temperature in Step 2, and considering the solidus temperature, powder sintering temperature, and microstructure phase transition temperature in the material properties, adjust the current to change the temperature of the heating area, ensuring that the center temperature is lower than the solidus temperature, powder sintering temperature, and microstructure phase transition temperature (i.e., approximately 40%-50% of the powder sintering temperature). During the additive manufacturing of thin-walled structures, an external laser source is used to controllably irradiate and synchronously heat the selected area. Based on the powder state and the temperature monitoring results from the infrared camera, the current is dynamically adjusted in real time to ensure that the temperature of the heating area fluctuates within 40%-50% of the powder sintering temperature. This achieves in-situ, synchronous, and dynamically adjustable external laser source. By adjusting the current of the external laser source, the temperature of the heating area is changed, ensuring that the temperature is maintained at 40%-50% of the powder sintering temperature. Within this temperature range, on the one hand, it can effectively reduce powder... The surface temperature gradient and thermal stress level of the final bed can, on the other hand, prevent powder sintering and significant phase transformation of the microstructure, thereby suppressing buckling deformation of the thin-walled structure. The auxiliary energy field system reduces the temperature gradient and cooling rate during the forming process by increasing the reference temperature of the powder bed and the thin-walled structure. The reduction in temperature gradient reduces the accumulation of thermal stress. When the thermal stress is always lower than the buckling critical stress of the thin-walled structure, the thin-walled structure does not experience geometric instability, thus completely eliminating buckling deformation. At the same time, since the heating temperature is much lower than the phase transformation temperature and sintering temperature of the microstructure, the solidification path and phase composition of the material do not change. In this step, during the layer-by-layer forming process of the thin-walled structure, an external laser source is simultaneously turned on to heat the powder and the forming area, keeping the powder and the formed structure at the set temperature state, reducing the internal temperature gradient of the thin-walled structure, and simultaneously achieving in-situ annealing treatment in the additive manufacturing process. Specifically:

[0046] Based on the heating range of 50 mm determined in step two, and considering the solidus temperature of Ti-6Al-4V (1605 °C), the powder sintering temperature (initial temperature 600-700 °C), and the microstructure phase transition temperature (700 °C), the current of the external laser source was adjusted to 6 A. The temperatures at the center of the heating area and 25 mm away from the center were 250.5 °C and 88.3 °C, respectively. That is, the center temperature is about 42% of the powder sintering temperature, ensuring that the heating area temperature can eliminate the deformation of the thin-walled structure while avoiding powder sintering.

[0047] During the layer-by-layer forming process of thin-walled structures, an external laser light source is simultaneously turned on to continuously heat the powder and the formed structure, keeping the powder and the formed structure at a set temperature to reduce the temperature gradient and thermal stress inside the thin-walled structure, while also achieving in-situ annealing in the additive manufacturing process.

[0048] An infrared camera, model A615 (FLIRSystems), was used to measure the temperature distribution in the heating area. The camera monitored the heating area temperature in real time. When the center temperature exceeded 300°C (i.e., the center temperature exceeded 50% of the powder sintering temperature), the current of the external laser source was dynamically reduced to 5.5 A. When the center temperature was below 240°C (i.e., the center temperature exceeded 40% of the powder sintering temperature), the current of the external laser source was dynamically increased to 6.5 A. This ensured that the heating area temperature fluctuated within the set range. The buckling deformation of the thin-walled structure decreased from 0.76 mm to 0.045 mm, achieving in-situ elimination of buckling deformation in the additively manufactured thin-walled structure. Figure 8 The image shows the in-situ elimination effect of buckling deformation in a thin-walled structure.

[0049] The preceding examples demonstrate that the auxiliary energy field elimination method for buckling deformation of thin-walled structures in additive manufacturing, through the construction of the auxiliary energy field system, the determination of the temperature range and distribution, the setting of the heating zone, and synchronous heating, achieves in-situ elimination of buckling deformation in thin-walled structures during additive manufacturing. This method has been successfully applied to thin-walled structures with cross-sectional dimensions of 30 mm × 30 mm and 34 mm × 6 mm, and a wall thickness of 0.5 mm. The verification results are as follows: Figure 6 and Figure 7 As shown.

[0050] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for eliminating the auxiliary energy field of buckling deformation in additively manufactured thin-walled structures, characterized in that, Includes the following steps: Step 1: Set up an auxiliary energy field system, which includes an external laser source with a Gaussian light distribution; Step 2: Based on the auxiliary energy field system in Step 1, obtain the correlation curves of spot diameter-current-temperature under different spot diameters and currents in the powder. Step 3: Based on the cross-sectional area of ​​the thin-walled structure to be manufactured, set the auxiliary energy field heating area and select the spot diameter from Step 2 so that the diameter of the heating area of ​​the external laser source is larger than the maximum cross-sectional size of the thin-walled structure to be formed. Step 4: Based on the relationship between spot diameter, current, and temperature in Step 2, the temperature of the heating area is changed by adjusting the current of the external laser source. In the process of additive manufacturing thin-walled structures, the selected area is controlled and synchronously heated by the external laser source to achieve in-situ elimination of buckling deformation of the additive manufacturing thin-walled structure.

2. The auxiliary energy field elimination method for buckling deformation of additively manufactured thin-walled structures according to claim 1, characterized in that, Step one specifically involves: setting a fixed bracket on the outside of the side window of the laser powder bed melting and forming equipment, and installing an external laser light source emitter through the fixed bracket to form an auxiliary energy field system for the additive manufacturing thin-walled structure forming process.

3. The auxiliary energy field elimination method for buckling deformation of additively manufactured thin-walled structures according to claim 1 or 2, characterized in that, In step two, thermocouples are used to measure the temperature at the center and edge of the heating area of ​​the powder under different spot diameters and currents, thereby obtaining the correlation curve of spot diameter-current-temperature for powder under different spot diameters and currents.

4. The auxiliary energy field elimination method for buckling deformation of additively manufactured thin-walled structures according to claim 3, characterized in that, In step two, multiple thermocouple probes are placed near the surface of the powder, and an external laser light source is turned on. The same spot diameter is maintained, and the temperature at the center and edge of the heating area is measured under different currents. The spot diameter is changed, and the temperature at the center and edge of the heating area is measured again under different current conditions until the temperature under all the required spot diameters is measured. The measured temperature data are then processed to obtain multiple sets of spot diameter-current-temperature correlation curves.

5. The auxiliary energy field elimination method for buckling deformation of additively manufactured thin-walled structures according to claim 4, characterized in that, In step two, while keeping the spot diameter the same, the current of the external laser source is gradually increased in increments of 0.5A when measuring the temperature at the center and edge of the heating area under different currents.

6. The auxiliary energy field elimination method for buckling deformation of additively manufactured thin-walled structures according to claim 4, characterized in that, The light spot diameter includes 30mm and 50mm.

7. The auxiliary energy field elimination method for buckling deformation of additively manufactured thin-walled structures according to any one of claims 4-6, characterized in that, In step four, the current is adjusted based on the solidus temperature, powder sintering temperature, and microstructure phase transformation temperature of the material properties, thereby changing the temperature of the heating zone so that the center temperature is lower than the solidus temperature, powder sintering temperature, and microstructure phase transformation temperature.

8. The auxiliary energy field elimination method for buckling deformation of additively manufactured thin-walled structures according to claim 7, characterized in that, In step four, the current is adjusted to change the temperature of the heating zone, so that the center temperature is between 40% and 50% of the powder sintering temperature.

9. The auxiliary energy field elimination method for buckling deformation of additively manufactured thin-walled structures according to claim 8, characterized in that, In the process of additive manufacturing thin-walled structures, an external laser light source is used to controllably irradiate and synchronously heat a selected area; based on the powder state and powder temperature monitoring results, the current is dynamically adjusted in real time to ensure that the center temperature of the heating area fluctuates within 40%-50% of the powder sintering temperature.

10. The auxiliary energy field elimination method for buckling deformation of additively manufactured thin-walled structures according to claim 9, characterized in that, In the process of additive manufacturing thin-walled structures, an infrared camera is used to monitor the temperature of the heating area in real time and dynamically adjust the current of the external laser source. That is, when the heating temperature exceeds 50% of the powder sintering temperature, the current value is reduced, and when the heating temperature is lower than 40% of the powder sintering temperature, the current value is increased to ensure that the temperature of the heating area fluctuates within the range of 40%-50% of the powder sintering temperature.

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