Dual laser additive manufacturing apparatus and method for unsupported overhanging structures

Abstract

The application discloses a kind of double laser additive manufacturing forming equipment and method for unsupported overhanging structure. Double laser additive manufacturing forming equipment includes controller and laser generation device, and laser generation device includes first laser and second laser. First laser outputs fine laser beam with spot diameter d1, and second laser outputs large laser beam with spot diameter d2, d1 < d2, and d1 and d2 are microns. In the forming process, the first laser prints the overhanging part before the second laser, and after printing a layer of slice in the overhanging part, the second laser is responsible for the forming of the corresponding non-overhanging part of the part, and finally a more uniform and dense powder bed is obtained by small layer thickness forming, improving the powder laying quality, and further improving the printing accuracy and resolution of the overhanging area. As can be seen, the application can efficiently form components with overhanging structure without support, and the surface quality of the formed overhanging surface is high.

Description

Technical Field

[0001] The present invention belongs to the field of laser additive manufacturing equipment and process innovation, and relates to a dual-laser additive manufacturing forming equipment and method for unsupported overhanging structures. Background Art

[0002] Conventional laser powder bed fusion (c-LPBF), a common additive manufacturing technique, typically uses a laser beam spot size of 60-100 μm, enabling near-net-net-shape formation of complex structures. However, c-LPBF currently suffers from high overhang surface roughness, low alloy forming precision, and low density. This poor surface quality can severely compromise part performance, significantly limiting the further industrial application of the formed alloys.

[0003] To meet the demands of LPBF ultra-precision machining, micro-laser powder bed fusion (μ-LPBF) technology has been developed in recent years. Compared to c-LPBF, μ-LPBF utilizes a smaller laser beam spot, thinner layer thickness, and finer metal powder, resulting in higher minimum feature resolution (<50 μm). This effectively reduces forming defects, produces a finer microstructure, improves part surface quality, and ultimately enhances the mechanical properties (tensile and fatigue properties, etc.) of the structure. With the advancement of product miniaturization in the industrial era, μ-LPBF technology offers advantages in achieving high-precision forming of micro-feature structures, making it suitable for the manufacture of micro-scale functional components in a variety of fields, including aviation, automotive, medical, and electronics. However, while μ-LPBF improves part forming accuracy, it also increases the time it takes to print the part, significantly reducing printing efficiency. Summary of the Invention

[0004] The purpose of the present invention is to solve the technical problems of low efficiency, low precision, low density and high roughness in the prior art of forming overhang structures.

[0005] In order to achieve the above technical objectives, the present invention will adopt the following technical solutions:

[0006] A dual-laser additive manufacturing (AM) device for unsupported overhanging structures includes 3D printing slicing software, a controller, a laser generating device, a powder spreading device, and a printing platform, wherein a forming substrate is provided on the printing platform. The laser generating device includes two devices, namely a first laser generating device and a second laser generating device.

[0007] The first laser generating device includes a first laser and a first galvanometer; the second laser generating device includes a second laser and a second galvanometer;

[0008] The 3D printing slicing software is used to divide the three-dimensional solid geometric model corresponding to the target part with the overhang structure into two parts, and then perform layered slicing on the two parts to obtain first and second slicing data respectively; the two parts into which the target part is divided correspond to the overhang part and the support part, the first slicing data is the data obtained by layered slicing of the overhang part, and the second slicing data is the data obtained by layered slicing of the support part;

[0009] The controller can plan a slice forming printing file accordingly according to the first and second slice data transmitted by the 3D printing slice software;

[0010] The forming substrate includes two forming split areas, corresponding to a first forming split area for printing and forming the overhang portion and a second forming split area for printing and forming the support portion;

[0011] Under the control of the execution instructions output by the slice forming printing file, the powder spreading device can spread the powder layer by layer on the forming substrate and ensure that the powder thickness of each layer is H1;

[0012] Under the control of the execution instructions output by the slice forming print file, the laser light emitted by the first laser can be projected onto the first forming sub-area after being deflected by the first galvanometer, and form a first light spot with a diameter of d1, so as to complete the printing and forming of the overhang portion layer by layer in the first forming sub-area; the laser light emitted by the second laser can be projected onto the second forming sub-area after being deflected by the second galvanometer, and form a second light spot with a diameter of d2, so as to complete the printing and forming of the support portion layer by layer in the second forming sub-area;

[0013] Under the control of the execution instructions output by the slicing forming print file, during the printing process of the target part, after the first laser completes slicing printing of a layer in the first forming sub-area, the second laser is switched to complete slicing printing of a layer with a powder coating thickness of H2 in the first forming sub-area, and this cycle is repeated until the printing of the target part is completed; where H2=a*H1, a is a positive integer greater than 1;

[0014] The laser power of the laser beam emitted by the first laser is P1, the laser scanning speed is V1, and the scanning interval is D1; ​​the laser power of the laser beam emitted by the second laser is P2, the laser scanning speed is V2, and the scanning interval is D2; wherein, d1 <d2且d1、d2均为微米级,P1<P2,V1> V2.

[0015] Another technical object of the present invention is to provide a dual-laser additive manufacturing method for an unsupported overhang structure, comprising the following steps:

[0016] Step 1: Partition and obtain slice data of the target part with overhanging structure:

[0017] Using computer-aided design software to create a three-dimensional solid geometric model of a target part with an overhang structure, the three-dimensional solid geometric model of the target part is divided into two parts: an overhang part and a support part using 3D printing slicing software; and the overhang part and the support part are sliced ​​in layers to obtain first slice data matching the overhang part and second slice data matching the support part respectively;

[0018] Step 2: Set the printing parameters for the target part with overhanging structure by partition:

[0019] Using the first and second laser forming devices to correspondingly print and form the overhanging portion and the supporting portion;

[0020] The printing parameters of the first laser forming device are: laser power P1, laser scanning speed V1, scanning spacing D1, powder thickness H1, and spot diameter d1; the printing parameters of the second laser forming device are: laser power P2, laser scanning speed V2, scanning spacing D2, and spot diameter d2; where d1 <d2,P1<P2,V1> V2, H2=n*H1, n is a positive integer greater than 1;

[0021] Step 3: Printing preparation:

[0022] The forming substrate is placed on a liftable printing platform and leveled; high-purity Ar gas is introduced into the laser forming chamber as a protective atmosphere, maintaining the oxygen content below 50 ppm;

[0023] Step 4: Printing the first layer of the overhanging part:

[0024] Printing a first layer of a forming overhang portion in a first forming sub-area of ​​the forming substrate specifically includes the following steps:

[0025] Step 4.1: Control the forming substrate to descend by a powder spreading thickness H1 of the overhang portion. Simultaneously, control the piston of the powder supply cylinder to ascend by a powder spreading thickness H1, so that the powder spreading device spreads a layer of printing powder with a powder spreading thickness H1 on the forming substrate.

[0026] Step 4.2: Start the first laser and drive the optical path of the first laser to the preset position A. The laser enters the focusing device to form a converged light, which is then reflected by the first galvanometer to form a first light spot in the first forming sub-body area. According to the orthogonal scanning strategy, the printing powder laid in step 4.1 is sintered and melted in the first forming sub-body area, thus completing the printing of the first layer of the overhang portion.

[0027] Repeat step 4.1, step 4.2 until the first layer of the overhanging part is printed and formed on the first forming sub-area, and the first laser is turned off;

[0028] Step five, the first layer of the support part is printed and formed:

[0029] The second laser is started and the light path of the second laser is moved to the preset position B, and the converging light is formed through the focusing device, and then reflected by the second galvanometer to form a second light spot in the second forming sub-area. According to the orthogonal scanning strategy, the printing powder laid in step four is sintered and melted in this part of the second forming sub-area, that is, the first layer of the support part is printed and formed, and the splicing printing of the target part is realized. At this time, the laying thickness of the printing powder sintered and melted by the second light spot is H2.

[0030] Repeat step four, step five until the splicing printing of the entire target part is completed.

[0031] Preferably, the printing powder used by the target part is AlMgScZr powder; in the AlMgScZr powder, the content of magnesium is 4.0-4.4 wt.%, the content of scandium is 0.38-0.43 wt.%, the content of zirconium is 0.15-0.21 wt.%, and the balance is aluminum.

[0032] Preferably, the spot diameter d1 of the first light spot is 10-40 μm, and the spot diameter d2 of the second light spot is 60-100 μm.

[0033] Preferably, the laying thickness H2 of each layer of the support part is 3 times the laying thickness H1 of the overhanging part.

[0034] Preferably, the printing and forming parameters of the first laser forming device are: laser power P1 = 25-75 W, laser scanning speed V1 = 900-1100 mm / s, scanning pitch D1 = 50 μm, and laying thickness H1 = 10-15 μm.

[0035] The printing and forming parameters of the second laser forming device are: laser power P2 = 375-425 W, laser scanning speed V2 = 700-900 mm / s, scanning pitch D2 = 50 μm, and laying thickness H2 = 30-45 μm.

[0036] Preferably, the particle size distribution of the printing powder used by the target part is 2-20 μm.

[0037] Preferably, the target part has an overhanging structure with a bottom surface inclination angle of 10-40°.

[0038] Based on the above technical objectives, the present invention has the following advantages over the prior art:

[0039] The present invention utilizes dual laser beams for zoned printing of target parts with overhang structures, effectively alleviating problems such as dross and high roughness in the overhanging portions. This improves the resolution of the overhanging portions, effectively reduces forming defects, achieves a finer microstructure, improves the surface quality of the part, and ultimately enhances the mechanical properties (tensile strength, fatigue resistance, etc.) of the structure. Specifically, the present invention utilizes 3D printing slicing software to divide the target part with an overhanging structure into two sections, which are then sliced ​​and layered to obtain first slice data corresponding to the overhanging portion and second slice data corresponding to the supporting portion. Furthermore, during slicing and layering, the present invention utilizes a "small layer thickness" forming method for the overhanging portion, taking into account the structural characteristics of the overhanging portion. To ensure effective improvement in printing accuracy and resolution of the overhanging portion, the present invention utilizes a smaller layer thickness for the overhanging portion. This results in a smaller powder layer thickness for the overhanging portion than for the supporting portion when subsequently planning the slicing and forming print file. This ensures a more uniform and dense powder bed for the overhanging portion, improving the powder layer quality and, consequently, enhancing printing accuracy and resolution of the overhanging portion. In addition, for the overhanging portion, the present invention uses a finer laser beam for irradiation. After fine laser irradiation, the heat distribution of the powder bed is more concentrated, thereby reducing powder melting and metal evaporation, reducing Marangoni convection and recoil pressure, producing a more regular melt flow, and effectively reducing spattering during the forming process. As for the supporting portion, the use of a continuous large-diameter laser beam improves forming efficiency on the one hand, and on the other hand, due to the uniform distribution of laser energy, the sintered thin layer at the connection between the overhanging portion and the supporting portion is quickly and effectively heated during the forming process, resulting in remelting and forming a continuous and stable molten pool. This enhances the adhesion and density of the printed surface at the connection position and repairs defects and flaws on the printed surface.

[0040] Therefore, the dual-laser additive manufacturing equipment is conducive to obtaining filling structure parts with higher surface accuracy and better uniformity, achieving high-precision and high-flexibility printing, and finally forming parts with high-precision overhang structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, and the above and / or other advantages of the present invention will become more apparent.

[0042] Figure 1 It is a three-dimensional solid geometry model of the target part with an overhanging structure;

[0043] Figure 2 This is a schematic diagram of the structure of the dual laser additive manufacturing equipment for unsupported overhanging structures;

[0044] The parts marked in the figure represent: 1-first laser; 2-second laser; 3-first galvanometer; 4-second galvanometer; 5-scraper; 6-forming cylinder; 7-powder cylinder; 8-controller; 9-printing platform;

[0045] Figure 3 This is the state diagram after executing step 3;

[0046] Figure 4 This is the state diagram after executing step 4;

[0047] Figure 5 This is the state diagram after executing step 5;

[0048] Figure 6 This is the state diagram after executing step 7;

[0049] Figure 7 This is the OM image of the sample formed using traditional laser powder bed fusion equipment;

[0050] Figure 8 OM image of the sample formed using micro laser powder bed fusion equipment. DETAILED DESCRIPTION

[0051] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. The following description of at least one exemplary embodiment is actually only illustrative and in no way serves as any limitation on the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative work are within the scope of protection of the present invention. Unless otherwise specified, the relative arrangement of components and steps, expressions and numerical values ​​described in these embodiments do not limit the scope of the present invention. Technologies, methods and equipment known to ordinary technicians in the relevant fields may not be discussed in detail, but where appropriate, the technologies, methods and equipment should be considered part of the specification. In all examples shown and discussed here, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of the exemplary embodiments may have different values.

[0052] like Figure 1The figure shows a 3D solid geometry model of a target part with an overhang structure, which can be divided into two parts: the overhang portion and the non-overhang portion (i.e., the support portion). If this structure is directly formed using conventional LPBF forming, the center of the molten pool will be separated from the support of the previous solidification layer. The melt in the molten pool tends to fall downward due to the combined effects of gravity, recoil pressure, and thermal capillary forces, filling the gaps in the metal powder. After solidification, this increases the roughness of the overhang surface, reducing the surface quality of the formed part.

[0053] To this end, the present invention has developed a dual-laser additive manufacturing device and method for unsupported overhang structures. The technical solution of the present invention will be described in detail below with reference to various embodiments. Example

[0054] like Figure 2 As shown, the dual-laser additive manufacturing forming equipment for unsupported overhanging structures described in this embodiment includes 3D printing slicing software, a controller 8, a laser generating device, a powder spreading device, and a closed printing chamber, wherein:

[0055] A liftable printing platform 9 is arranged in the closed printing chamber, a forming substrate is provided on the printing platform 9, a scraper 5 is provided above the printing platform 9, and a forming cylinder 6 and a powder cylinder 7 are provided below the printing platform 9; in addition, a vent is provided at one end of the closed printing chamber to enable the introduction of inert gas; and a filter element is provided at the other end.

[0056] The laser generating device includes two, namely a first laser generating device and a second laser generating device; the first laser generating device includes a first laser 1 and a first galvanometer 3; the second laser generating device includes a second laser 2 and a second galvanometer 4;

[0057] The 3D printing slicing software is used to divide the three-dimensional solid geometric model corresponding to the target part with an overhang structure into two parts, and then perform layered slicing on the two parts respectively to obtain first and second slicing data respectively; the two parts into which the target part is divided correspond to the overhang part and the support part, the first slicing data is the data obtained by layered slicing of the overhang part, and the second slicing data is the data obtained by layered slicing of the support part.

[0058] The controller 8 can plan the slice forming printing file accordingly according to the first and second slice data transmitted by the 3D printing slice software;

[0059] The forming substrate includes two forming split areas, corresponding to a first forming split area for printing and forming the overhang portion and a second forming split area for printing and forming the support portion;

[0060] Under the control of the execution instructions output by the slice forming printing file, the powder spreading device can spread the powder layer by layer on the forming substrate and ensure that the powder thickness of each layer is H1;

[0061] Under the control of the execution instructions output by the slice forming print file, the laser light emitted by the first laser 1, after being deflected by the first galvanometer 3, can be projected onto the first forming sub-area, forming a first light spot with a diameter of d1, thereby completing the printing and forming of the overhang portion layer by layer in the first forming sub-area. The laser light emitted by the second laser 2, after being deflected by the second galvanometer 4, can be projected onto the second forming sub-area, forming a second light spot with a diameter of d2, thereby completing the printing and forming of the support portion layer by layer in the second forming sub-area. In this embodiment, the diameters of the light spots formed by the first and second lasers 2 are both in the micron range. Specifically, the first laser 1 outputs a fine laser beam spot, i.e., the first light spot has a diameter of d1 = 20-40 μm, while the second laser 2 outputs a larger laser beam spot, i.e., the second light spot has a diameter of d2 = 60-100 μm.

[0062] Under the control of the execution instructions output by the slicing forming print file, during the printing process of the target part, after the first laser 1 completes slicing printing of a layer in the first forming sub-area, the second laser 2 is switched to complete slicing printing of a layer with a powder coating thickness of H2 in the first forming sub-area, and this cycle is repeated until the printing of the target part is completed; where H2=a*H1, a is a positive integer greater than 1;

[0063] The laser power of the laser beam emitted by the first laser 1 is P1, the laser scanning speed is V1, and the scanning distance is D1; ​​the laser power of the laser beam emitted by the second laser 2 is P2, the laser scanning speed is V2, and the scanning distance is D2; wherein, d1 <d2,P1<P2,V1> V2.

[0064] As can be seen from this, the overhang portion of the present invention utilizes a thin layer thickness forming process. Compared to the support portion, its laser power is lower, and a tiny spot is used to sinter and melt the powder. Consequently, on the one hand, the heat distribution of the powder bed after fine laser irradiation is more concentrated, resulting in a more regular melt flow and effectively reducing spattering during the forming process. On the other hand, the thin layer thickness forming process for the overhang portion can achieve higher powder coating quality, alleviating problems such as slag and high roughness in the overhang structure. This can effectively reduce internal cracks and porosity in the part and improve the forming accuracy of the overhang structure. For the support area, a larger spot, higher laser power, and thicker powder coating are used to improve forming efficiency. Example

[0065] Based on the above-mentioned dual-laser additive manufacturing forming equipment for unsupported overhang structures, this embodiment provides a dual-laser additive manufacturing forming method for unsupported overhang structures, which specifically includes the following steps:

[0066] Step 1: Partition and obtain slice data of the target part with overhanging structure:

[0067] Computer-aided design software is used to establish a three-dimensional solid geometric model of a target part with an overhang structure. The three-dimensional solid geometric model of the target part is divided into two parts: an overhang part and a support part using 3D printing slicing software. The overhang part and the support part are layered and sliced ​​separately to obtain first slice data matching the overhang part and second slice data matching the support part respectively.

[0068] In this example, the target part is made from AlMgScZr powder. This AlMgScZr powder contains 4.0-4.4 wt.% magnesium, 0.38-0.43 wt.% scandium, 0.15-0.21 wt.% zirconium, and the balance aluminum. The printing powder typically has a particle size distribution of 2 μm to 20 μm.

[0069] Step 2: Set the printing parameters for the target part with overhanging structure by partition:

[0070] Using the first and second laser forming devices to correspondingly print and form the overhanging portion and the supporting portion;

[0071] The printing parameters of the first laser forming device are: laser power P1, laser scanning speed V1, scanning interval D1, powder thickness H1, and spot diameter d1;

[0072] The printing parameters of the second laser forming device are: laser power P2, laser scanning speed V2, scanning interval D2, and spot diameter d2; where d1 <d2,P1<P2,V1> V2, H2=n*H1, n is a positive integer greater than 1;

[0073] When the target part is printed using AlMgScZr powder, the printing parameters of the first laser forming device are: laser power P1=50 W, laser scanning speed V1=1000 mm / s, scanning spacing D1=50 μm, powder thickness H1=10μm-15μm, orthogonal scanning strategy, and interlayer rotation angle of 90°; the printing parameters of the second laser forming device are: laser power P2=400 W, laser scanning speed V2=800 mm / s, scanning spacing D2=50 μm, powder thickness H2=30μm-45 μm, orthogonal scanning strategy, and interlayer rotation angle of 90°.

[0074] Step three, print preparation:

[0075] Set the forming substrate on the liftable printing platform 9 and level it; introduce high-purity Ar gas into the laser forming chamber as a protective atmosphere, keeping the oxygen content below 50 ppm;

[0076] Step four: first layer printing forming of the overhanging part:

[0077] Print the first layer of the overhanging part on the first forming sub-area of the forming substrate, which specifically includes the following steps:

[0078] Step 4.1, control the forming substrate to descend by one powder laying thickness H1, and at the same time, control the powder supply cylinder piston to ascend by one powder laying thickness H1, so that the powder laying device lays a layer of printing powder with a powder laying thickness of H1 on the forming substrate;

[0079] Step 4.2, start the first laser 1 and drive the light path of the first laser 1 to move to the preset position A, enter the focusing device to form converging light, and then reflect through the first galvanometer 3 to form a first light spot in the first forming sub-area, and the light spot diameter d1 = 10 μm - 40 μm, according to the orthogonal scanning strategy, so that the printing powder laid in step 4.1 is sintered and melted in this part of the first forming sub-area, that is, the first layer printing forming of the overhanging part is completed.

[0080] Repeat steps 4.1 and 4.2 until the a-th layer of the overhanging part is completed in the first forming sub-area, and then turn off the first laser 1;

[0081] Step five: first layer printing forming of the support part:

[0082] Start the second laser 2 and drive the light path of the second laser 2 to move to the preset position B, enter the focusing device to form converging light, and then reflect through the second galvanometer 4 to form a second light spot in the second forming sub-area, and the light spot diameter d2 = 60 μm - 100 μm, according to the orthogonal scanning strategy, so that the printing powder laid in step four is sintered and melted in this part of the second forming sub-area, that is, the first layer printing forming of the support part is completed. In this process, due to the use of continuous large-diameter laser beam, the laser energy is uniformly distributed, which can quickly and effectively uniformly heat the sintered thin layer at the connection position between the overhanging part and the support part during the forming process, thereby causing remelting to form a continuous and stable molten pool, enhancing the adhesion and density of the printing surface at the connection position, repairing defects and flaws on the printing surface, and realizing the splicing printing of the target part. At this time, the powder laying thickness of the printing powder sintered and melted by the second light spot is H2;

[0083] Repeat steps 4 and 5 until the entire target part is printed. After printing is complete, the printing platform 9 and the parts are allowed to reach room temperature. Open the door and remove the printed parts. Use wire cutting to separate the parts from the forming substrate to obtain the target part.

[0084] In this embodiment, the support part's powder coating thickness (H2) is three times the overhang part's powder coating thickness (H1). In other words, during the printing process, after printing three layers of overhang part slices with a powder coating thickness of H1, one layer of support part slices with a powder coating thickness of H2 is printed. This cycle continues until the entire target part is printed. Example

[0085] Based on the above-mentioned dual-laser additive manufacturing forming equipment for unsupported overhang structures, this embodiment provides a dual-laser additive manufacturing forming method for unsupported overhang structures, which specifically includes the following steps:

[0086] Step 1: Partition and obtain slice data of the target part with overhanging structure:

[0087] Computer-aided design software is used to establish a three-dimensional solid geometric model of a target part with an overhang structure. The three-dimensional solid geometric model of the target part is divided into two parts: an overhang part and a support part using 3D printing slicing software. The overhang part and the support part are layered and sliced ​​separately to obtain first slice data matching the overhang part and second slice data matching the support part respectively.

[0088] In this example, the target part is made from AlMgScZr powder. This AlMgScZr powder contains 4.0-4.4 wt.% magnesium, 0.38-0.43 wt.% scandium, 0.15-0.21 wt.% zirconium, and the balance aluminum. The printing powder typically has a particle size distribution of 2 μm to 20 μm.

[0089] Step 2: Set the printing parameters for the target part with overhanging structure by partition:

[0090] Using the first and second laser forming devices to correspondingly print and form the overhanging portion and the supporting portion;

[0091] The printing parameters of the first laser forming device are: laser power P1, laser scanning speed V1, scanning interval D1, powder thickness H1, and spot diameter d1;

[0092] The printing forming parameters of the second laser forming device are: laser power P2, laser scanning speed V2, scanning interval D2, and spot diameter d2; wherein d1 < d2, P1 < P2, V1 > V2, H2 = n*H1, n is a positive integer greater than 1;

[0093] When the target part is printed and formed by using AlMgScZr powder, the printing forming parameters of the first laser forming device are: laser power P1 = 75 W, laser scanning speed V1 = 1100 mm / s, scanning interval D1 = 50 μm, powder laying thickness H1 = 10 μm-15 μm, and the orthogonal scanning strategy is adopted, and the interlayer rotation angle is 90°; the printing forming parameters of the second laser forming device are: laser power P2 = 375 W, laser scanning speed V2 = 900 mm / s, scanning interval D2 = 50 μm, powder laying thickness H2 = 30 μm-45 μm, and the orthogonal scanning strategy is adopted, and the interlayer rotation angle is 90°.

[0094] Step three, printing preparation:

[0095] A forming substrate is arranged on the liftable printing platform 9 and is leveled; high-purity Ar gas is introduced into the laser forming chamber as a protective atmosphere, and the oxygen content is kept below 50 ppm;

[0096] Step four: first layer printing forming of the overhanging part:

[0097] The first layer of the overhanging part is printed and formed in the first forming sub-area of the forming substrate, specifically including the following steps:

[0098] Step 4.1, control the forming substrate to descend by a powder laying thickness H1 of the overhanging part, and at the same time, control the powder supply cylinder piston to ascend by a powder laying thickness H1, so that the powder laying device lays a layer of printing powder with a powder laying thickness of H1 on the forming substrate;

[0099] Step 4.2, start the first laser 1, and drive the light path of the first laser 1 to move to the preset position A, form converging light through the focusing device, and then reflect through the first galvanometer 3 to form a first spot in the first forming sub-area, and the spot diameter d1 of the first spot is 10 μm-40 μm, according to the orthogonal scanning strategy, the printing powder laid in step 4.1 is sintered and melted in this part of the first forming sub-area, that is, the first layer printing forming of the overhanging part is completed.

[0100] When the printing powder is AlMgScZr powder,

[0101] Repeat steps 4.1 and 4.2 until the a-th layer of the overhanging part is printed and formed on the first forming sub-area, and the first laser 1 is turned off;

[0102] Step 5: Print the first layer of the support part:

[0103] Start the second laser 2 and drive the optical path of the second laser 2 to the preset position B. The light enters the focusing device to form a converged light, which is then reflected by the second galvanometer 4 to form a second light spot in the second forming split area. The spot diameter of the second light spot is d2 = 60μm-100μm. According to the orthogonal scanning strategy, the printing powder laid in step 4 is sintered and melted in this part of the second forming split area, thus completing the first layer printing of the support part and realizing the splicing printing of the target part. At this time, the powder thickness of the printing powder sintered and melted by the second light spot is H2;

[0104] Repeat steps 4 and 5 until the entire target part is printed. After printing is complete, the printing platform 9 and the parts are allowed to reach room temperature. Open the door and remove the printed parts. Use wire cutting to separate the parts from the forming substrate to obtain the target part.

[0105] In this embodiment, the support part's powder coating thickness (H2) is three times the overhang part's powder coating thickness (H1). In other words, during the printing process, after printing three layers of overhang part slices with a powder coating thickness of H1, one layer of support part slices with a powder coating thickness of H2 is printed. This cycle continues until the entire target part is printed. Example

[0106] Based on the above-mentioned dual-laser additive manufacturing forming equipment for unsupported overhang structures, this embodiment provides a dual-laser additive manufacturing forming method for unsupported overhang structures, which specifically includes the following steps:

[0107] Step 1: Partition and obtain slice data of the target part with overhanging structure:

[0108] Computer-aided design software is used to establish a three-dimensional solid geometric model of a target part with an overhang structure. The three-dimensional solid geometric model of the target part is divided into two parts: an overhang part and a support part using 3D printing slicing software. The overhang part and the support part are layered and sliced ​​separately to obtain first slice data matching the overhang part and second slice data matching the support part respectively.

[0109] In this example, the target part is made from AlMgScZr powder. This AlMgScZr powder contains 4.0-4.4 wt.% magnesium, 0.38-0.43 wt.% scandium, 0.15-0.21 wt.% zirconium, and the balance aluminum. The printing powder typically has a particle size distribution of 2 μm to 20 μm.

[0110] Step 2: Set the printing parameters for the target part with overhanging structure by partition:

[0111] Using the first and second laser forming devices to correspondingly print and form the overhanging portion and the supporting portion;

[0112] The printing parameters of the first laser forming device are: laser power P1, laser scanning speed V1, scanning interval D1, powder thickness H1, and spot diameter d1;

[0113] The printing parameters of the second laser forming device are: laser power P2, laser scanning speed V2, scanning interval D2, and spot diameter d2; where d1 <d2,P1<P2,V1> V2, H2=n*H1, n is a positive integer greater than 1;

[0114] When the target part is printed using AlMgScZr powder, the printing parameters of the first laser forming device are: laser power P1=25 W, laser scanning speed V1=900 mm / s, scanning spacing D1=50 μm, powder thickness H1=10μm-15μm, orthogonal scanning strategy, and interlayer rotation angle of 90°; the printing parameters of the second laser forming device are: laser power P2=425 W, laser scanning speed V2=700 mm / s, scanning spacing D2=50 μm, powder thickness H2=30μm-45 μm, orthogonal scanning strategy, and interlayer rotation angle of 90°.

[0115] Step 3: Printing preparation:

[0116] A forming substrate is placed on a liftable printing platform 9 and leveled; high-purity Ar gas is introduced into the laser forming chamber as a protective atmosphere, maintaining the oxygen content below 50 ppm;

[0117] Step 4: Printing the first layer of the overhanging part:

[0118] Printing a first layer of a forming overhang portion in a first forming sub-area of ​​the forming substrate specifically includes the following steps:

[0119] Step 4.1: Control the forming substrate to descend by a powder spreading thickness H1 of the overhang portion. Simultaneously, control the piston of the powder supply cylinder to ascend by a powder spreading thickness H1, so that the powder spreading device spreads a layer of printing powder with a powder spreading thickness H1 on the forming substrate.

[0120] Step 4.2: Start the first laser 1 and drive the optical path of the first laser 1 to move to the preset position A. The light enters the focusing device to form converged light, which is then reflected by the first galvanometer 3 to form a first light spot in the first forming split area. The spot diameter of the first light spot is d1 = 10μm - 40μm. According to the orthogonal scanning strategy, the printing powder laid in step 4.1 is sintered and melted in this part of the first forming split area, thereby completing the first layer printing of the overhanging part.

[0121] Repeat steps 4.1 and 4.2 until the a-th layer of slices of the overhanging portion is printed and formed on the first forming split area, and then turn off the first laser 1;

[0122] Step 5: Print the first layer of the support part:

[0123] Start the second laser 2 and drive the optical path of the second laser 2 to the preset position B. The light enters the focusing device to form a converged light, which is then reflected by the second galvanometer 4 to form a second light spot in the second forming split area. The spot diameter of the second light spot is d2 = 60μm-100μm. According to the orthogonal scanning strategy, the printing powder laid in step 4 is sintered and melted in this part of the second forming split area, thus completing the first layer printing of the support part and realizing the splicing printing of the target part. At this time, the powder thickness of the printing powder sintered and melted by the second light spot is H2;

[0124] Repeat steps 4 and 5 until the entire target part is printed. After printing is complete, the printing platform 9 and the parts are allowed to reach room temperature. Open the door and remove the printed parts. Use wire cutting to separate the parts from the forming substrate to obtain the target part.

[0125] In this embodiment, the support part's powder coating thickness (H2) is three times the overhang part's powder coating thickness (H1). In other words, during the printing process, after printing three layers of overhang part slices with a powder coating thickness of H1, one layer of support part slices with a powder coating thickness of H2 is printed. This cycle continues until the entire target part is printed.

[0126] Application Examples

[0127] By the process described in Example 2, a similar Figure 1 The target part with overhanging structure can obtain a formed part with good surface quality without support, which specifically includes the following steps:

[0128] Step 1: Select and dry Al-4.2Mg-0.4Sc-0.2Zr alloy fine powder with a powder particle size distribution of 2-20 μm, wherein the magnesium content is 4.0-4.4 wt.%, the scandium content is 0.38-0.43 wt.%, the zirconium content is 0.15-0.21 wt.%, and the balance is aluminum.

[0129] Step 2: Use computer-aided design software to establish a three-dimensional solid geometric model of the target part with an overhang structure, and use 3D printing slicing software to slice the part in layers and divide the overhang and non-overhang areas. Set different scanning laser process parameters according to the area, as follows: (1) Overhang part: The first laser 1 is formed with a laser power of 50 W, a laser scanning speed of 1000 mm / s, a scanning pitch of 50 μm, a powder thickness of 10 μm, an orthogonal scanning strategy, and an inter-layer rotation angle of 90°; (2) Non-overhang part: The second laser 2 is formed with a laser power of 400 W, a laser scanning speed of 800 mm / s, a scanning pitch of 50 μm, a powder thickness of 30 μm, an orthogonal scanning strategy, and an inter-layer rotation angle of 90°. The above laser parameters are determined after process optimization, and the slicing file is imported into a dual-laser additive manufacturing forming device;

[0130] Step 3: Wipe the equipment and laser lens with alcohol. Place the aluminum alloy substrate on a liftable workbench and level it. Introduce high-purity Ar gas into the laser forming chamber as a protective atmosphere, maintaining the oxygen content below 50 ppm.

[0131] In step 4, the control system lowers the substrate by the powder layer thickness (10 μm) of the overhanging area according to the slicing file. Conversely, it raises the piston of the powder supply cylinder by the corresponding powder layer thickness, and the powder spreading device spreads a layer of AlMgScZr powder to be processed. The controller 8 activates the optical path of the first laser 1 to move to the overhang preset position of the required processing part set by the program, enters the focusing device to form a concentrated light, and then reflects it through the first galvanometer 3 to form a fine light spot (spot diameter 30 μm) on the processing plane, causing the overhanging part powder to sinter and melt, completing the laser powder bed fusion forming of the first layer of overhanging slices, participating in Figure 3 ;

[0132] Step 5: The required processing parts are lowered by a slice layer thickness of an overhang area (10 μm) and powder is laid. The laser scanning is continued with the first laser beam (emitted by the first laser 1) to fill the second layer of non-overhanging area in the processing plane, completing the laser powder bed fusion forming of the second layer of overhanging slices. Figure 4 ;

[0133] Step 6: The required processing parts are lowered by a slice layer thickness of 10 μm in the non-overhanging area and powder laying is performed. The laser scanning is continued with the first laser beam mentioned above to fill the third layer of overhanging area in the processing plane, and the laser powder bed fusion forming of the third layer of overhanging slices is completed. Figure 5 ;

[0134] Step 7: After the overhang structure is printed, if the non-overhang structure needs to be printed, the scanning laser is converted from the first laser beam to the second laser beam (emitted by the second laser 2). The conversion process can be completed by the control software. Specifically, the control system starts the optical path of the second laser 2, moves to the non-overhang preset position of the required processing parts set by the program according to the slicing file, enters the focusing device to form converged light, and then reflects through the second galvanometer 4 to form a large light spot (spot diameter 70 μm) on the processing plane, and starts to quickly fill the non-overhang area in the processing plane, so that the powder of the non-overhang part is sintered and melted, completing the laser powder bed fusion forming of a layer of non-overhang slices, and realizing the splicing and printing of the same part. Figure 6 ;

[0135] In step 8, repeat steps 4-7 above, alternating the lasers, until a uniform, dense, three-dimensional solid part is formed. After printing is complete, the printing platform 9 and the part are allowed to cool to room temperature. The chamber door is opened and the printed part is removed. Wire cutting is used to separate the part from the forming substrate, yielding an AlMgScZr part with an overhanging structure.

[0136] Because the first laser (1) utilizes a finer laser beam, heat distribution in the powder bed is more concentrated after irradiation. This reduces powder melting and metal evaporation, lowering Marangoni convection and recoil pressure, and producing a more regular melt flow. Using a smaller layer thickness in the overhanging area creates a more uniform and dense powder bed, improving powder spreading quality and further enhancing printing accuracy and resolution in the overhanging area. Figure 7 The OM image of the sample formed using traditional laser powder bed fusion shows that there are many defects such as pores on the sample surface, which will lead to the deterioration of mechanical properties, such as reduced tensile strength and fatigue performance; Figure 8 The OM image of the sample formed using micro-laser powder bed fusion shows that the internal pores and other defects of the sample formed by fine laser, small layer thickness and fine powder are effectively reduced, forming a finer microstructure, thereby effectively improving the mechanical properties of the structure.

[0137] The laser output of the traditional laser powder bed melting equipment is large-diameter light spot, and the non-overhanging area is printed with large layer thickness, which can effectively improve the forming efficiency and reduce the occurrence of collapse or large deformation. Then, the fine laser beam and small layer thickness of the micro laser powder bed melting equipment ensure the interlayer bonding of the formed part to be dense and form a good metallurgical bond. Therefore, the double laser additive manufacturing forming equipment and method adopted in the embodiment can form an overhanging structure without support, and the surface quality of the overhanging surface is high.

Claims

1. A dual-laser additive manufacturing (AM) device for unsupported overhanging structures, comprising 3D printing slicing software, a controller, a laser generator, a powder spreading device, and a printing platform, wherein a forming substrate is provided on the printing platform; characterized in that: The laser generating device includes two, corresponding to a first laser generating device and a second laser generating device; The first laser generating device includes a first laser and a first galvanometer; the second laser generating device includes a second laser and a second galvanometer; The 3D printing slicing software is used to divide the three-dimensional solid geometric model corresponding to the target part with the overhang structure into two parts, and then perform layered slicing on the two parts to obtain first and second slicing data respectively; the two parts into which the target part is divided correspond to the overhang part and the support part, the first slicing data is the data obtained by layered slicing of the overhang part, and the second slicing data is the data obtained by layered slicing of the support part; The controller can plan a slice forming printing file accordingly according to the first and second slice data transmitted by the 3D printing slice software; The forming substrate includes two forming split areas, corresponding to a first forming split area for printing and forming the overhang portion and a second forming split area for printing and forming the support portion; Under the control of the execution instructions output by the slice forming printing file, the powder spreading device can spread the powder layer by layer on the forming substrate and ensure that the powder thickness of each layer is H1; Under the control of the execution instructions output by the slice forming print file, the laser light emitted by the first laser is deflected by the first galvanometer and projected onto the first forming sub-area, forming a first light spot with a diameter of d1, so as to complete the printing of the overhang portion layer by layer in the first forming sub-area; The laser light emitted by the second laser is deflected by the second galvanometer and can be projected onto the second forming split area, forming a second light spot with a diameter of d2, so as to complete the printing of the support part layer by layer in the second forming split area; Under the control of the execution instructions output by the slicing forming print file, during the printing process of the target part, after the first laser completes slicing printing of a layer in the first forming sub-area, the second laser is switched to complete slicing printing of a layer with a powder coating thickness of H2 in the first forming sub-area, and this cycle is repeated until the printing of the target part is completed; where H2=a*H1, a is a positive integer greater than 1; The laser power of the laser beam emitted by the first laser is P1, the laser scanning speed is V1, and the scanning interval is D1; ​​the laser power of the laser beam emitted by the second laser is P2, the laser scanning speed is V2, and the scanning interval is D2; wherein, d1 <d2,P1< P2,V1> V2.

2. A dual laser additive manufacturing method for unsupported overhanging structures, characterized in that: The steps include: Step 1: Partition and obtain slice data of the target part with overhanging structure: A 3D solid geometric model of a target part with an overhanging structure is established using computer-aided design software, and the 3D solid geometric model of the target part is divided into two parts: an overhanging part and a supporting part using 3D printing slicing software; and slicing the overhang portion and the supporting portion in layers, respectively, to correspondingly obtain first slicing data matching the overhang portion and second slicing data matching the supporting portion; Step 2: Set the printing parameters for the target part with overhanging structure by partition: Using the first and second laser forming devices to correspondingly print and form the overhanging portion and the supporting portion; The printing parameters of the first laser forming device are: laser power P1, laser scanning speed V1, scanning pitch D1, powder thickness H1, and spot diameter d1; the printing parameters of the second laser forming device are: laser power P2, laser scanning speed V2, scanning pitch D2, and spot diameter d2; where d1 < d2, P1 < P2, V1 > V2, and H2 = n * H1, where n is a positive integer greater than 1. Step 3: Printing preparation: The forming substrate is placed on a liftable printing platform and leveled; high-purity Ar gas is introduced into the laser forming chamber as a protective atmosphere, maintaining the oxygen content below 50 ppm; Step 4: Printing the first layer of the overhanging part: Printing a first layer of a forming overhang portion in a first forming sub-area of ​​a forming substrate specifically includes the following steps: Step 4.1: Control the forming substrate to descend by a powder spreading thickness H1 of the overhang portion. Simultaneously, control the piston of the powder supply cylinder to ascend by a powder spreading thickness H1, so that the powder spreading device spreads a layer of printing powder with a powder spreading thickness H1 on the forming substrate. Step 4.2: Start the first laser and drive the optical path of the first laser to the preset position A. The laser enters the focusing device to form a converged light, which is then reflected by the first galvanometer to form a first light spot in the first forming sub-body area. According to the orthogonal scanning strategy, the printing powder laid in step 4.1 is sintered and melted in the first forming sub-body area, thus completing the printing of the first layer of the overhang portion. Repeat steps 4.1 and 4.2 until the a-th layer of the overhanging portion is printed on the first forming split area, and then turn off the first laser. Step 5: Print the first layer of the support part: Start the second laser and drive the optical path of the second laser to the preset position B. The laser enters the focusing device to form a converged light, which is then reflected by the second galvanometer to form a second light spot in the second forming split area. According to the orthogonal scanning strategy, the printing powder laid in step 4 is sintered and melted in this part of the second forming split area, thus completing the first layer of printing of the support part and realizing the splicing printing of the target part. At this time, the powder thickness of the printing powder sintered and melted by the second light spot is H2; Repeat steps 4 and 5 until the entire target part is completed.

3. The dual laser additive manufacturing method for unsupported overhanging structures according to claim 2, characterized in that: The printing powder used for the target part is AlMgScZr powder; the AlMgScZr powder has a magnesium content of 4.0-4.4 wt.%, a scandium content of 0.38-0.43 wt.%, a zirconium content of 0.15-0.21 wt.%, and the balance is aluminum; The powder thickness H2 of each layer of the supporting part is 3 times the powder thickness H1 of the overhanging part; The printing parameters of the first laser forming device are: laser power P1 = 25W-75W, laser scanning speed V1 = 900mm / s-1100mm / s, scanning distance D1 = 50μm, powder thickness H1 = 10μm-15μm; The printing parameters of the second laser forming device are: laser power P2 = 375W - 425W, laser scanning speed V2 = 700mm / s - 900mm / s, scanning spacing D2 = 50 μm, and powder thickness H2 = 30μm - 45 μm.

4. The dual laser additive manufacturing method for an unsupported overhanging structure according to claim 3, characterized in that: The spot diameter of the first light spot is d1 = 10 μm - 40 μm, and the spot diameter of the second light spot is d2 = 60 μm - 100 μm.

5. The dual laser additive manufacturing method for unsupported overhanging structures according to claim 3, characterized in that: The particle size distribution of the printing powder used for the target parts is 2μm ~20μm.

6. The dual laser additive manufacturing method for an unsupported overhanging structure according to claim 2, characterized in that: The target part has an overhang structure with a bottom surface inclination angle of 10°-40°.

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