Local atmosphere protection device and method for laser fuse additive manufacturing

Abstract

The invention discloses a local atmosphere protection device for laser fuse additive manufacturing, and relates to the technical field of metal additive manufacturing, the local atmosphere protection device comprises a printing substrate and a laser, the laser is arranged above the printing substrate, and the local atmosphere protection device further comprises a supporting assembly and a main protection air curtain assembly which are arranged on the printing substrate; the supporting assembly is used for supporting the laser, and the supporting assembly comprises an elastic upper cover body and a rigid lower cover body. Through the up-and-down split type structure with the upper portion moving and the lower portion static and the dynamic sealing connection design, the cooperative relation that the upper cover body moves along with a laser device and the rigid lower cover body keeps fixed relative to a printing substrate and keeps a constant gap is achieved, and the contradiction that dynamic movement and stable gap of a traditional rigid cover are difficult to consider is effectively solved.

Description

Technical Field

[0001] This invention relates to the field of metal additive manufacturing technology, and more specifically, to a local atmosphere protection device and method for laser filament additive manufacturing. Background Technology

[0002] Off-axis laser filament additive manufacturing, a key technology in the field of metal additive manufacturing, is based on laser cladding. By arranging the laser beam and the wire feeding mechanism at a certain side angle, continuous metal wire is fed into the molten pool, achieving efficient additive forming of complex structures and large-sized metal components. Compared with traditional powder bed melting or powder-fed laser cladding processes, off-axis laser filament additive manufacturing offers advantages such as high material utilization, low wire cost, minimal dust hazard, and high forming efficiency. It has broad application prospects in the manufacturing and repair of highly reactive metal components such as high-strength aluminum alloys, magnesium alloys, and titanium alloys.

[0003] However, highly reactive metals such as magnesium, aluminum, and titanium have an extremely high affinity for oxygen at high temperatures, and even in environments with low oxygen content, they will undergo severe oxidation, leading to defects such as oxide inclusions, elemental loss, and porosity, which seriously affect the strength, plasticity, and fatigue life of the formed parts. Therefore, in the off-axis laser filament additive manufacturing process, it is necessary to establish and maintain a stable low-oxygen or ultra-low-oxygen local protective atmosphere near the molten pool and the preheating zone of the metal wire.

[0004] The invention patent document, entitled "A Controllable Atmosphere Protection Device for Laser Rapid Forming of Titanium Alloy Parts," with authorization announcement number 200910122291.0 and authorization announcement date of 2012-04-18, consists of a rigid sealed box and a flexible bladder-type sealing cover. The rigid sealed box is provided with an inflation port and an exhaust port, each equipped with a valve. During the evacuation process, the air inside the cavity is extracted through the exhaust port. Under negative pressure, the flexible bladder-type sealing cover gradually approaches and eventually tightly adheres to the inner wall and bottom of the rigid sealed box, thus expelling all the air from the cavity. Subsequently, the valve on the evacuation port is closed, and the valve on the inflation port is opened to introduce the required protective gas. During the introduction of the protective gas, the flexible bladder-type sealing cover rises and expands, creating the required protective atmosphere inside the cavity. In the existing technology, the atmosphere protection methods commonly used in off-axis laser filament additive manufacturing mainly include: (1) Side-blown protective gas method: Inert gas is sprayed into the molten pool area through one or more nozzles to reduce the oxygen concentration around the molten pool. This method has a simple structure and is easy to integrate, but it has obvious shortcomings: First, the end of the metal wire is in a high-temperature preheated state before entering the molten pool, and is often located at the edge or dead corner of the side-blown airflow, which is not enough to protect it and is prone to oxidation; Second, the side-blown airflow is an open turbulent flow, which makes it difficult to form a uniform protective gas curtain at the tail of the molten pool and in complex geometric areas, resulting in serious local mixing and unstable protection effect; Third, the side-blown gas field is easily disturbed by the ambient airflow and operating conditions, and the flow field repeatability is poor. (2) Overall atmosphere glove box method: The entire processing system is arranged in a large closed cavity, and a low-oxygen environment is formed by filling it with high-purity inert gas to achieve protection of the entire processing area. This method provides good protection, but it requires a large, sealed enclosure and a complex atmosphere control system, resulting in extremely high equipment and operation and maintenance costs. Furthermore, the size of the enclosure limits the size and range of motion of the workpiece, making it unsuitable for large components and assembly line production scenarios.

[0005] It is evident that current off-axis laser filament additive manufacturing, when processing highly reactive metals, still lacks a local atmosphere device that can dynamically move with the laser, maintain an appropriate and constant gap with the substrate, and provide continuous, uniform, and stable protection for the molten pool and filament preheating zone without relying on a large, integrated glove box. In particular, during additive forming, as the number of forming layers increases, the height of the interface where the molten pool is located rises layer by layer, making it difficult for existing local protection devices to simultaneously ensure the continuity and stability of protection effects at different forming heights. Summary of the Invention

[0006] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a local atmosphere protection device and method for laser filament additive manufacturing.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a printing substrate and a laser, the laser being disposed above the printing substrate. The solution further includes a support assembly and a main protective air curtain assembly disposed on the printing substrate. The support assembly supports the laser and includes an elastic upper cover and a rigid lower cover. The elastic upper cover is connected to the rigid lower cover via a dynamic sealing connection, and a cavity is formed between the elastic upper cover and the rigid lower cover. The main protective air curtain assembly communicates with the cavity and is used to introduce gas into the cavity to maintain pressure balance within the cavity. During additive manufacturing, the laser drives the elastic upper cover to move and undergo elastic deformation, while the rigid lower cover remains fixed, allowing the dynamic sealing connection to adapt to the relative displacement between the upper and lower covers and maintain the cavity seal.

[0008] Preferably, the laser is disposed on the elastic upper cover.

[0009] Preferably, the rigid lower cover is fixedly installed on the annular rigid structure of the equipment bed, and the bottom of the rigid lower cover has an opening, with a gap of 0.5-3mm between its bottom edge and the surface of the printing substrate.

[0010] Preferably, the main protective gas curtain assembly includes an annular pressure equalization chamber and an annular microporous plate connected to and arranged around the bottom of the rigid lower cover. The annular microporous plate is provided with multiple densely packed micropores. The micropores are used to spray high-purity inert protective gas in an inclined direction towards the inside of the chamber perpendicular to the surface of the printing substrate or relative to the normal direction of the printing substrate, forming a laminar flow gas curtain above the surface of the printing substrate and overflowing through the gaps.

[0011] Preferably, the main protective air curtain assembly further includes an annular exhaust strip, which is disposed at the upper end of the rigid lower cover and near the dynamic sealing connection, and has multiple exhaust micro-holes opened in the circumferential direction. The exhaust micro-holes are used to discharge the mixed gas inside the cavity and maintain a slightly positive pressure and ultra-low oxygen environment inside the cavity. The protective gas is continuously introduced through the main protective air curtain assembly and flows from bottom to top. Combined with the bottom gap overflow and the exhaust of the annular exhaust strip, an organized airflow channel from bottom to top is formed in the cavity.

[0012] Preferably, the diameter of the micropores on the annular microporous plate is 0.1-0.5 mm, and the spacing between the pores is 2-5 times the diameter of the pores; the air outlet direction of the micropores is perpendicular to the surface of the printing substrate, or inclined at 0-15° towards the inside of the cover relative to the normal direction of the printing substrate.

[0013] Preferably, the gap between the bottom edge of the rigid lower cover and the surface of the printing substrate is 0.5-3mm.

[0014] Preferably, the elastic upper cover is made of a high-temperature resistant flexible material, and the elastic upper cover is provided with a wire feeding guide and a side blowing air pipe; wherein, the side wall of the elastic upper cover is provided with at least one rigid mounting seat, which is used to fix the wire feeding guide and the side blowing air pipe to achieve an integrated arrangement of wire feeding and local protection.

[0015] Preferably, the diameter of the exhaust micropores in the annular exhaust strip is 0.5-2mm, so as to balance exhaust capacity and stable maintenance of local micro-positive pressure.

[0016] A method for local atmosphere protection in metal laser filament additive manufacturing, applied to a local atmosphere protection device for laser filament additive manufacturing, includes the following steps: Step 1: First, high-purity inert protective gas is introduced into the main protective gas curtain assembly. Then, after being buffered by the annular equalizing chamber, the protective gas is ejected through the micropores on the annular microporous plate, forming a laminar flow gas curtain above the surface of the printed substrate and overflowing through the gaps. At the same time, a micro-positive pressure is established in the cavity formed by the elastic upper cover and the rigid lower cover. Under continuous gas supply conditions, the original air and water vapor in the cavity are gradually replaced and discharged through the annular exhaust strip until the oxygen concentration in the cavity drops below the preset threshold. Step 2: Start the laser and external wire feeding mechanism. The laser outputs a laser beam and forms a molten pool on the surface of the printed substrate. The metal wire is fed into the preheating zone in front of the molten pool through the wire feeding guide. During the additive manufacturing process, the laser drives the elastic upper cover to move and undergo elastic deformation, while the rigid lower cover remains fixed. In this way, the dynamic sealing connection adapts to the relative displacement between the upper and lower covers and keeps the cavity sealed, thereby protecting the gas from flowing continuously from bottom to top and forming a stable local low-oxygen environment around the molten pool and the end of the metal wire. Step 3: As the number of forming layers increases, the formed target component gradually grows upward in the inner cavity of the rigid lower cover, and the height of the interface where the molten pool is located increases accordingly. However, the rigid lower cover is fixed to the machine bed by the support structure, and the gap between its bottom edge and the printing substrate remains constant throughout the additive manufacturing process. Moreover, the bottom annular gap is located in the outer edge area of ​​the target component and is not blocked by the target component, so that the molten pool is always in the low oxygen cavity filled with inert gas throughout the additive manufacturing process. Step 4: After the target component is formed, turn off the laser and the external wire feeding mechanism. The main protective gas curtain assembly continues to operate at a low flow rate to cool the molten pool area and the high-temperature target component in a low-oxygen environment. After the temperature drops to a safe range, gradually reduce the protective gas flow rate and turn off the gas supply. Remove the device and inspect and clean the elastic upper cover, the annular microporous plate and the dynamic sealing connection.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1. In this invention, the upper and lower split structure of "upper moving and lower stationary" and dynamic sealing connection design realize the coordinated relationship of the upper cover moving with the laser, while the rigid lower cover remains fixed relative to the printing substrate and maintains a constant gap. This effectively solves the contradiction between dynamic movement and stable gap in traditional rigid covers.

[0018] 2. In this invention, the main protective gas curtain assembly based on the annular pressure equalization cavity and the annular microporous plate can form a uniform and stable laminar flow gas curtain in the molten pool and the preheating zone at the end of the wire, improve the uniformity of protective gas coverage, effectively eliminate the problem of dead corners in the wire preheating zone and the tail of the molten pool, and significantly reduce oxide inclusions and porosity defects.

[0019] 3. In this invention, by combining the main protective air curtain with the annular exhaust strip, an organized airflow channel from bottom to top is formed in the local cavity enclosed by the upper and lower covers. This enables rapid air replacement within a limited space and maintains a slightly positive pressure ultra-low oxygen environment, avoiding the defects of unstable atmosphere protection in traditional open side blowing under complex configurations and different forming heights.

[0020] 4. In this invention, the height of the inner cavity of the rigid lower cover has a reserved margin relative to the maximum forming height, so that the molten pool is always within the low oxygen cavity range as the height of the additive interface increases layer by layer. The protection mechanism can smoothly transition from "surface air curtain + overall low oxygen" to "overall low oxygen cavity + bottom-up flow field protection", ensuring the continuity and stability of the protection effect under different forming heights.

[0021] 5. In this invention, the elastic upper cover and its rigid mounting base realize the integrated arrangement of the wire feeding guide and the side blowing air pipe with the protective cover. The structure is compact and highly compatible. It can be easily integrated into the existing off-axis laser filament additive manufacturing system without the need for a large overall protective cabin. While ensuring the protection effect, it significantly reduces equipment costs and maintenance difficulty. It is suitable for large-size components and production line scenarios. Attached Figure Description

[0022] Figure 1 This invention presents a side view cross-sectional structural diagram of a local atmosphere protection device for laser filament additive manufacturing in the printing state.

[0023] Figure 2 This invention presents a schematic diagram of the annular pressure equalization cavity and the annular microporous plate in a local atmosphere protection device for laser filament additive manufacturing.

[0024] In the figure: 1-Laser; 2-Elastic upper cover; 3-Rigid lower cover; 4-Dynamic sealing connection; 5-Annular microporous plate; 5a-Annular pressure equalization cavity; 5b-Micropore; 6-Annular exhaust strip; 7-Wire feeding guide; 8-Side blowing pipe; 9-Laser beam; 10-Metal wire; 11-Molten pool; 12-Target component; 13-Printing substrate; G-Gap. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Reference Figures 1 to 2 This invention proposes a local atmosphere protection device for laser filament additive manufacturing, comprising a printing substrate 13 and a laser 1, the laser 1 being disposed above the printing substrate 13. It also includes a support assembly and a main protective gas curtain assembly disposed on the printing substrate 13. The support assembly supports the laser 1 and includes an elastic upper cover 2 and a rigid lower cover 3. The elastic upper cover 2 is connected to the rigid lower cover 3 via a dynamic sealing connection, forming a cavity between the elastic upper cover 2 and the rigid lower cover 3. During the additive manufacturing process, gas is first introduced into the main protective gas curtain assembly to maintain pressure balance within the cavity. Then, the laser 1 drives the elastic upper cover 2 to move and undergo elastic deformation, while the rigid lower cover 3 remains fixed, allowing the dynamic sealing connection 4 to adapt to the relative displacement between the upper and lower covers and maintain the cavity seal. The laser 1 is disposed on the elastic upper cover 2.

[0027] Specifically, the laser is mounted on the elastic upper cover 2, and the rigid lower cover 3 is located below the elastic upper cover 2, connected by a dynamic sealing connection. Further, the dynamic sealing connection 4 is positioned between the lower end of the elastic upper cover 2 and the upper end of the rigid lower cover 3, forming a ring-shaped sealing connection through an elastic sleeve, bellows, or an interference fit with an elastic sealing ring, allowing relative displacement without compromising airtightness. This resolves the contradiction between dynamic movement and maintaining a constant gap and airtightness. The rigid lower cover 3 is preferably made of steel, but other rigid materials are also acceptable, as long as it achieves rigidity and non-deformation. The elastic upper cover 2 is preferably made of rubber to allow deformation when the laser 1 moves. Thus, during additive manufacturing, the laser 1 drives the elastic upper cover 2 to move and undergo elastic deformation, while the rigid lower cover 3 remains fixed. In this way, the dynamic sealing connection 4 adapts to the relative displacement between the upper and lower covers and maintains the cavity seal. The rigid lower cover 3 is fixedly installed on the annular rigid structure of the equipment bed, and an opening is provided at the bottom of the rigid lower cover 3, with a gap of 0.5-3mm between its bottom edge and the surface of the printing substrate 13. It should be noted that a constant micro-gap of 0.5-3mm is provided at the bottom of the rigid lower cover 3, and a laminar flow air curtain is formed by using an "annular pressure equalization chamber + annular microporous plate". The overflow from the bottom gap drives the chamber to renew from bottom to top, maintaining a slightly positive pressure ultra-low oxygen environment. This solves the problems of unstable open side-blowing turbulent flow protection, dead corners in the preheating zone / melt pool tail, and mixing issues.

[0028] The main protective air curtain assembly includes an annular pressure equalization chamber 5a and an annular microporous plate 5 connected to and arranged around the bottom of the rigid lower cover 3. The annular microporous plate 5 is provided with multiple densely packed micropores 5b. The micropores 5b are used to spray high-purity inert protective gas in an inclined direction towards the inside of the chamber perpendicular to the surface of the printing substrate 13 or relative to the normal direction of the printing substrate 13, forming a laminar flow air curtain above the surface of the printing substrate 13 and overflowing through the gap G. The main protective air curtain assembly also includes an annular exhaust strip 6, which is located at the upper end of the rigid lower cover 3 and near the dynamic sealing connection part 4, and has multiple exhaust micro-holes along the circumference. The exhaust micro-holes are used to discharge the mixed gas inside the cavity and maintain a slightly positive pressure and ultra-low oxygen environment inside the cavity. The protective gas is continuously introduced through the main protective air curtain assembly and flows from bottom to top. Combined with the overflow of the bottom gap G and the exhaust of the annular exhaust strip 6, an organized airflow channel from bottom to top is formed in the cavity to achieve dynamic local atmosphere protection for the molten pool 11 and the preheating zone at the end of the metal wire 10.

[0029] It should be noted that the inner cavity height H of the rigid lower cover 3 is greater than 1.2-1.5 times the maximum forming height, ensuring that the molten pool 11 remains within a low-oxygen cavity filled with inert gas throughout the additive manufacturing process. In practical applications, the distance between the center of the molten pool 11 and the annular microporous plate 5 is maintained within the range of 10-40 mm by adjusting the Z-axis of the equipment or the substrate lifting mechanism, in order to balance the protective airflow velocity, the stability of the flow field around the molten pool 11, and the gas consumption at different forming heights.

[0030] In this embodiment, the diameter of the micropores on the annular microporous plate 5 is 0.1-0.5 mm, and the spacing between the pores is 2-5 times the diameter of the pores. The air outlet direction of the micropores is perpendicular to the surface of the printing substrate 13, or inclined at 0-15° relative to the normal direction of the printing substrate 13 towards the inner side of the cover, thereby obtaining a uniform and stable laminar flow air curtain under limited air volume, covering the molten pool and the wire preheating zone, and significantly reducing oxide inclusions and porosity defects.

[0031] In this invention, the gap between the bottom edge of the rigid lower cover 3 and the surface of the printing substrate 13 is 0.5-3 mm. Specifically, the gap between the bottom edge of the rigid lower cover 3 and the surface of the printing substrate 13 is more preferably about 1.5 mm, so as to ensure the formation of the bonding air curtain while taking into account the processing gap and workpiece height variation.

[0032] In this invention, the elastic upper cover 2 is made of a high-temperature resistant flexible material, and is equipped with a wire feeding guide 7 and a side-blowing air pipe 8. At least one rigid mounting seat is provided on the side wall of the elastic upper cover 2 to fix the wire feeding guide 7 and the side-blowing air pipe 8, achieving an integrated arrangement of wire feeding and local protection. It should be noted that the elastic upper cover 2 is connected to the laser 1 via a mounting flange and is sealed to the rigid lower cover 3 via a dynamic sealing connection 4. The wire feeding guide 7 and the side-blowing air pipe 8 are fixed on the rigid mounting seat of the elastic upper cover 2, and the inner cavity height H of the rigid lower cover 3 is selected according to the target maximum forming height, such that H ≥ 1.2 hmax. The diameter of the exhaust micropores in the annular exhaust strip 6 is 0.5-2 mm, allowing the mixed gas to be discharged in an organized manner under a slight positive pressure, forming a bottom-up channel. This improves the replacement efficiency, reduces external entrainment, and stably maintains low oxygen levels, thus balancing exhaust capacity and the stable maintenance of local slight positive pressure.

[0033] Working principle: Step 1: First, high-purity inert protective gas is introduced into the annular microporous plate 5. Then, after being buffered by the annular equalizing chamber 5a, the protective gas is ejected through the microholes 5b on the annular microporous plate 5, forming a laminar flow air curtain above the surface of the printed substrate 13 and overflowing through the gaps. At the same time, a micro-positive pressure is established in the cavity formed by the elastic upper cover 2 and the rigid lower cover 3. Under continuous gas supply conditions, the original air and water vapor in the cavity are gradually replaced and discharged through the annular exhaust strip 6 until the oxygen concentration in the cavity drops below the preset threshold. Step 2: Start the laser 1 and the external wire feeding mechanism. The laser 1 outputs a laser beam 9 and forms a molten pool 11 on the surface of the printing substrate 13. The metal wire 10 is fed into the preheating zone in front of the molten pool 11 through the wire feeding guide 7. During the additive manufacturing process, the laser 1 drives the elastic upper cover 2 to move and undergo elastic deformation, while the rigid lower cover 3 remains fixed. In this way, the dynamic sealing connection part 4 adapts to the relative displacement between the upper and lower covers and keeps the cavity sealed, thereby protecting the gas from flowing continuously from bottom to top and forming a stable local low oxygen environment around the molten pool 11 and the end of the metal wire 10. Step 3: As the number of forming layers increases, the formed target component 12 gradually grows upward in the inner cavity of the rigid lower cover 3, and the height of the interface where the molten pool 11 is located increases accordingly. However, the rigid lower cover 3 is fixed to the equipment bed by the support structure, and the gap G between its bottom edge and the printing substrate 13 remains constant throughout the additive manufacturing process. Moreover, the bottom annular gap G is located in the outer edge area of ​​the target component 12 and is not blocked by the target component 12, thereby ensuring that the surface gas curtain formed by the main protective gas curtain assembly can continuously overflow through the gap G and drive the gas inside the cavity to flow from bottom to top. This ensures that the molten pool 11 is always within the low-oxygen cavity filled with inert gas throughout the additive manufacturing process, smoothly transitioning from the initial stage of "surface gas curtain + overall low oxygen" to the later stage of "overall low oxygen cavity + bottom-up flow field protection", ensuring the continuity and stability of the protection effect at different forming heights. Step 4: After the target component 12 is formed, turn off the laser 1 and the external wire feeding mechanism. The main protective gas curtain assembly continues to operate at a low flow rate to cool the molten pool 11 area and the high-temperature target component 12 in a low-oxygen environment. After the temperature drops to a safe range, gradually reduce the protective gas flow rate and turn off the gas supply. Remove the device and inspect and clean the elastic upper cover 2, the annular microporous plate 5 and the dynamic sealing connection 4.

[0034] A method for local atmosphere protection in metal laser filament additive manufacturing, applied to a local atmosphere protection device for laser filament additive manufacturing, comprising the following steps: Step 1: First, high-purity inert protective gas is introduced into the annular microporous plate 5. Then, after being buffered by the annular pressure equalization chamber, the protective gas is ejected through the micropores on the annular microporous plate 5, forming a laminar flow air curtain above the surface of the printed substrate 13 and overflowing through the gap G. At the same time, a micro-positive pressure is established in the cavity formed by the elastic upper cover 2 and the rigid lower cover 3. Under continuous gas supply conditions, the original air and water vapor in the cavity are gradually replaced and discharged through the annular exhaust strip 6 until the oxygen concentration in the cavity drops below the preset threshold. Step 2: Start the laser 1 and the external wire feeding mechanism. The laser 1 outputs a laser beam 9 and forms a molten pool 11 on the surface of the printing substrate 13. The metal wire 10 is fed into the preheating zone in front of the molten pool 11 through the wire feeding guide 7. During the additive manufacturing process, the laser 1 drives the elastic upper cover 2 to move and undergo elastic deformation, while the rigid lower cover 3 remains fixed. In this way, the dynamic sealing connection part 4 adapts to the relative displacement between the upper and lower covers and keeps the cavity sealed, thereby protecting the gas from flowing continuously from bottom to top and forming a stable local low oxygen environment around the molten pool 11 and the end of the metal wire 10. Step 3: As the number of forming layers increases, the formed target component 12 gradually grows upward in the inner cavity of the rigid lower cover 3, and the height of the interface where the molten pool is located increases accordingly. However, the rigid lower cover 3 is fixed to the equipment bed by the support structure, and the gap between its bottom edge and the printing substrate 13 remains constant throughout the additive process. Moreover, the bottom annular gap is located in the outer edge area of ​​the target component 12 and is not blocked by the target component 12, so that the molten pool is always in the low oxygen cavity filled with inert gas throughout the additive process. Step 4: After the target component is formed, turn off the laser 1 and the external wire feeding mechanism. The main protective gas curtain assembly continues to operate at a low flow rate to cool the molten pool 11 area and the high-temperature target component 12 in a low-oxygen environment. After the temperature drops to a safe range, gradually reduce the protective gas flow rate and turn off the gas supply. Remove the device and inspect and clean the elastic upper cover 2, the annular microporous plate 5 and the dynamic sealing connection 4.

[0035] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A local atmosphere protection device for laser filament additive manufacturing, comprising a printing substrate and a laser, wherein the laser is disposed above the printing substrate, characterized in that, It also includes a support assembly and a main protective air curtain assembly disposed on the printing substrate. The support assembly is used to support the laser and includes an elastic upper cover and a rigid lower cover. The elastic upper cover is connected to the rigid lower cover through a dynamic sealing connection, and a cavity is formed between the elastic upper cover and the rigid lower cover. The main protective air curtain assembly is in communication with the cavity and is used to introduce gas into the cavity to maintain the air pressure balance in the cavity. During the additive manufacturing process, the laser drives the elastic upper cover to move and undergo elastic deformation, while the rigid lower cover remains fixed, so that the dynamic sealing connection adapts to the relative displacement between the upper and lower covers and keeps the cavity sealed.

2. The local atmosphere protection device for laser filament additive manufacturing according to claim 1, characterized in that, The laser is mounted on the elastic upper cover.

3. A local atmosphere protection device for laser filament additive manufacturing according to claim 2, characterized in that, The rigid lower cover is fixedly installed on the ring-shaped rigid structure of the equipment bed, and the bottom of the rigid lower cover has an opening, with a gap of 0.5-3mm between its bottom edge and the surface of the printing substrate.

4. A local atmosphere protection device for laser filament additive manufacturing according to claim 3, characterized in that, The main protective air curtain assembly includes an annular pressure equalization chamber and an annular microporous plate connected to and arranged around the bottom of the rigid lower cover. The annular microporous plate is provided with multiple densely packed micropores. The micropores are used to spray high-purity inert protective gas in an inclined direction towards the inside of the chamber perpendicular to the surface of the printing substrate or relative to the normal direction of the printing substrate, forming a laminar flow air curtain above the surface of the printing substrate and overflowing through the gaps.

5. A local atmosphere protection device for laser filament additive manufacturing according to claim 4, characterized in that, The main protective air curtain assembly also includes an annular exhaust strip, which is located at the upper end of the rigid lower cover and near the dynamic sealing connection, and has multiple exhaust micro-holes along the circumference. The exhaust micro-holes are used to discharge the mixed gas inside the cavity and maintain a slightly positive pressure and ultra-low oxygen environment inside the cavity. The protective gas is continuously introduced through the main protective air curtain assembly and flows from bottom to top. Combined with the bottom gap overflow and the exhaust of the annular exhaust strip, an organized airflow channel from bottom to top is formed in the cavity.

6. A local atmosphere protection device for laser filament additive manufacturing according to claim 5, characterized in that, The diameter of the micropores on the annular microporous plate is 0.1-0.5 mm, and the spacing between the pores is 2-5 times the diameter of the pores. The air outlet direction of the micropores is perpendicular to the surface of the printing substrate, or inclined at 0-15° towards the inside of the cover relative to the normal direction of the printing substrate.

7. A local atmosphere protection device for laser filament additive manufacturing according to claim 6, characterized in that, The gap between the bottom edge of the rigid lower cover and the surface of the printing substrate is 0.5-3mm.

8. A local atmosphere protection device for laser filament additive manufacturing according to claim 7, characterized in that, The elastic upper cover is made of high-temperature resistant flexible material, and is equipped with a wire feeding guide and a side blowing pipe. The elastic upper cover has at least one rigid mounting seat on its side wall. The rigid mounting seat is used to fix the wire feeding guide and the side blowing air pipe to achieve an integrated arrangement of wire feeding and local protection.

9. A local atmosphere protection device for laser filament additive manufacturing according to claim 8, characterized in that, The diameter of the exhaust micropores in the annular exhaust strip is 0.5-2mm, so as to balance exhaust capacity and stable maintenance of local micro-positive pressure.

10. A method for local atmosphere protection in metal laser filament additive manufacturing, applied to the local atmosphere protection device for laser filament additive manufacturing as described in claim 9, characterized in that, The method for local atmosphere protection in metal laser filament additive manufacturing includes the following steps: Step 1: First, high-purity inert protective gas is introduced into the main protective gas curtain assembly. Then, after being buffered by the annular equalizing chamber, the protective gas is ejected through the micropores on the annular microporous plate, forming a laminar flow gas curtain above the surface of the printed substrate and overflowing through the gaps. At the same time, a micro-positive pressure is established in the cavity formed by the elastic upper cover and the rigid lower cover. Under continuous gas supply conditions, the original air and water vapor in the cavity are gradually replaced and discharged through the annular exhaust strip until the oxygen concentration in the cavity drops below the preset threshold. Step 2: Start the laser and external wire feeding mechanism. The laser outputs a laser beam and forms a molten pool on the surface of the printed substrate. The metal wire is fed into the preheating zone in front of the molten pool through the wire feeding guide. During the additive manufacturing process, the laser drives the elastic upper cover to move and undergo elastic deformation, while the rigid lower cover remains fixed. In this way, the dynamic sealing connection adapts to the relative displacement between the upper and lower covers and keeps the cavity sealed, thereby protecting the gas from flowing continuously from bottom to top and forming a stable local low-oxygen environment around the molten pool and the end of the metal wire. Step 3: As the number of forming layers increases, the formed target component gradually grows upward in the inner cavity of the rigid lower cover, and the height of the interface where the molten pool is located increases accordingly. However, the rigid lower cover is fixed to the machine bed by the support structure, and the gap between its bottom edge and the printing substrate remains constant throughout the additive manufacturing process. Moreover, the bottom annular gap is located in the outer edge area of ​​the target component and is not blocked by the target component, so that the molten pool is always in the low oxygen cavity filled with inert gas throughout the additive manufacturing process. Step 4: After the target component is formed, turn off the laser and the external wire feeding mechanism. The main protective gas curtain assembly continues to operate at a low flow rate to cool the molten pool area and the high-temperature target component in a low-oxygen environment. After the temperature drops to a safe range, gradually reduce the protective gas flow rate and turn off the gas supply. Remove the device and inspect and clean the elastic upper cover, the annular microporous plate and the dynamic sealing connection.

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