Selective laser melting grafting printing method for large-size metal thin-wall frame structure

Abstract

The invention discloses a selective laser melting grafting printing method for a large-size metal thin-wall frame structure, and belongs to the technical field of laser printing. The selective laser melting grafting printing method comprises the following steps that S1, an auxiliary substrate used for bearing selective laser melting printing is designed; s2, the modified three-dimensional model is input into the selective laser melting equipment and printed; s3, the original substrate and the auxiliary substrate are separated, stress relief heat treatment is conducted on the integrated structure, and the part, except for the bottom face, of the auxiliary substrate in the integrated structure is machined to form the bottom face of the large-size metal thin-wall frame structure; and S4, machining is adopted for carrying out cutting treatment on the supporting structure on the remaining part of the machined integrated structure so as to form the large-size metal thin-wall frame structure, by optimizing the clamping mode and the printing direction, the printing height is reduced as much as possible, and the residual stress and the printing time in the product forming process are reduced.

Description

Technical Field

[0001] The invention relates to the technical field of laser printing, and in particular to a laser selective melting grafting printing method for a large-size metal thin-wall frame structure. Background Art

[0002] In recent years, with the development of metal additive processing and innovative structural design, metal products with structural functional integration and lightweight characteristics have been widely used in the fields of aerospace and special equipment. Large-size metal frame thin-walled structural parts are typical representatives of this. For large-size metal thin-walled frame structures, the parts are large in size (length and width greater than 1000mm, thickness greater than 200mm), and it is difficult to forge through the thickness direction using traditional forging solutions. At the same time, the machining removal rate is large (more than 90%), and the processing cycle and cost are long. If a casting solution is adopted, due to the thin wall thickness (within 2.5mm), casting requires adding allowances on both sides of the thin wall, and some of the inner structures of the frame have problems such as inaccessibility to machining, and casting requires preparation of molds, and the overall manufacturing cycle is long.

[0003] Laser selective melting additive manufacturing can achieve integrated forming of metal thin-walled frame structures. However, the bottom cross-section of the frame structure is large (over 1m2). If the thickness direction is used as the printing direction, a large amount of heat will be generated at the contact position between the cross-section and the substrate. The risk of deformation of parts and substrates caused by thermal stress is uncontrollable, and the printing success rate is extremely low. If the length or width direction is used as the printing direction, the part printing height will exceed 1m, which greatly prolongs the printing cycle. In addition, there are a large number of overhanging surfaces, and a large number of auxiliary supports need to be added, making post-processing extremely difficult.

[0004] Therefore, it is urgent to design a large-size metal thin-walled frame structure laser selective melting grafting printing method to solve the above problems. Summary of the invention

[0005] The technical problem to be solved by the present invention is: for large-scale metal thin-walled frame structures, mainly rectangular frame structures, a sub-baseboard assembly and anti-locking clamping scheme that cooperates with the original baseboard of the laser selective melting equipment is adopted, and the sub-baseboard with the same base material as the frame structure is used as the thin-walled bottom surface of the frame mechanism, and the original baseboard is used as the anti-deformation bottom plate, so as to reduce the influence of thermal stress in traditional printing methods and reduce the printing time at the same time. By adding a support structure to the bent part of the frame structure where stress is concentrated, the risk of fracture and deformation at the connection between the bottom surface of large-size structural parts and the baseboard is greatly reduced.

[0006] The technical solution adopted by the present invention to solve the technical problem is: a laser selective melting grafting printing method for a large-size metal thin-walled frame structure, comprising the following steps:

[0007] S1: A sub-base plate designed to carry laser selective melting printing, the material of the sub-base plate is consistent with the material of the large-size metal thin-walled frame structure, the large-size metal thin-walled frame structure is a three-dimensional structure with a groove body composed of a bottom surface with a flat surface and a metal thin-walled frame part arranged on one side of the bottom surface, the format size of the sub-base plate is larger than the format size of the bottom surface of the large-size metal thin-walled frame structure, and the sub-base plate can be detachably installed in the center of the original base plate of the laser selective melting printing device for laser selective melting printing;

[0008] S2: inputting a modified three-dimensional model into the selective laser melting device, wherein the modified three-dimensional model includes a model of the metal thin-walled frame portion and a support model of a support structure for supporting the metal thin-walled frame portion during printing, and performing laser printing at the center of the secondary substrate according to the modified three-dimensional model to form an integrated structure combining the metal thin-walled frame portion, the support structure and the secondary substrate;

[0009] S3: taking out the integrated structure and the original substrate from the laser selective melting printing device, separating the secondary substrate from the original substrate, performing stress relief heat treatment on the integrated structure, and processing the secondary substrate to remove excess parts while retaining the bottom surface of the large-sized metal thin-walled frame structure;

[0010] S4: performing a cutting process of the supporting structure on the remaining part of the integrated structure after the processing to form a large-sized metal thin-wall frame structure.

[0011] As a preferred technical solution of the present invention, the bottom surface is a quadrilateral structure, and the metal thin-walled frame portion is composed of an outer frame connected end to end and an internal frame located inside the outer frame and dividing the outer frame into a plurality of troughs, and the outer frame is roughly vertically arranged on the bottom surface along the four sides of the bottom surface.

[0012] As a preferred technical solution of the present invention, the support structure is located on the secondary substrate and is connected to the bent portion on the outer side of the outer frame.

[0013] As a preferred technical solution of the present invention, the supporting structure includes reinforcing ribs and crack-stopping ribs. The number of the reinforcing ribs is several, and several of the reinforcing ribs are connected along the outer side of the outer frame and the front and rear positions of the bending part of the outer side of the outer frame. Several of the reinforcing ribs are connected to each other through the crack-stopping ribs, and the crack-stopping ribs are connected to the sub-baseboard. Several crack-stopping holes are arranged at the edge positions of the reinforcing ribs.

[0014] As a preferred technical solution of the present invention, the thickness of the bottom surface does not exceed 2.5mm, the thickness of the sub-substrate is greater than the thickness of the bottom surface, when the shortest side of the bottom surface is ≤600mm, the thickness range of the sub-substrate is 50mm-100mm, and when the shortest side of the bottom surface is >600mm, the thickness range of the sub-substrate is 25mm-40mm.

[0015] As a preferred technical solution of the present invention, a plurality of non-through blind holes are evenly formed on the side of the sub-substrate that does not bear printing, a plurality of countersunk holes corresponding to the blind holes are formed on the original substrate, mounting bolts are arranged in the countersunk holes, and the sub-substrate and the original substrate are detachably connected by the mounting bolts and the plurality of blind holes and countersunk holes.

[0016] As a preferred technical solution of the present invention, the depth of the blind hole is not less than 20 mm, and the distance from the printing-bearing side of the sub-substrate to the blind hole is greater than the thickness of the bottom surface.

[0017] As a preferred technical solution of the present invention, the length of the mounting bolt after being inserted into the blind hole is not less than 20 mm.

[0018] As a preferred technical solution of the present invention, the edge chamfer of the auxiliary substrate is not less than R10, the flatness of the auxiliary substrate does not exceed 20 degrees, the thickness of the original substrate is not less than 100 mm, and the flatness of the thick substrate does not exceed 20 degrees.

[0019] As a preferred technical solution of the present invention, the processing includes wire cutting-machining processing and milling processing. Wire cutting-machining processing is adopted when the shortest side of the bottom surface is ≤600mm, and milling processing is adopted when the shortest side of the bottom surface is greater than 600mm. When the wire cutting-machining processing is adopted, the part of the sub-substrate in the integrated structure except the bottom surface is wire cut, and the part of the sub-substrate remaining on the bottom surface after wire cutting is machined to form the bottom surface of the large-size metal thin-walled frame structure. When the milling processing is adopted, the part of the sub-substrate in the integrated structure except the bottom surface is milled to form the bottom surface of the large-size metal thin-walled frame structure.

[0020] The beneficial effects of the present invention are embodied in:

[0021] 1. Printing is performed by using a sub-substrate with the same substrate as the frame structure and the original substrate of the laser selective melting equipment. The sub-substrate with the same substrate as the frame structure is used as the thin-walled bottom surface of the frame mechanism, and the original substrate is used as the anti-deformation bottom plate. Through the above form, on the one hand, the thickness direction can be used as the printing direction, thereby saving printing time and reducing time costs. On the other hand, since printing is performed on the sub-substrate with the same substrate, the influence of thermal stress during printing is reduced, thereby ensuring the success rate of printing.

[0022] 2. For large-sized metal thin-walled frame structural parts, especially materials with large thermal stress such as titanium alloy and high-strength steel, by adding annular grid supports at the stress concentration point, specifically, by adding support structures to the outer bending part of the outer frame, the deformation of the parts and the risk of printing cracking can be effectively reduced, the printing success rate can be improved, and the support structure can be easily removed later.

[0023] 3. Reduce the probability of part deformation by selecting a thicker original substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a schematic top view of the auxiliary substrate portion of the present invention;

[0025] Figure 2 is a front cross-sectional schematic diagram of the auxiliary substrate portion of the present invention;

[0026] Figure 3 It is a partial connection schematic diagram of the support structure of the present invention;

[0027] Figure 4 It is a schematic diagram of a reinforcement rib provided with a crack-stopping hole according to the present invention;

[0028] Figure 5 It is a front cross-sectional schematic diagram of the auxiliary base plate of the present invention after being spliced ​​with the original base plate without installing the mounting bolts;

[0029] Figure 6 It is a front view and cross-sectional schematic diagram of the installation bolts installed after the auxiliary base plate and the original base plate of the present invention are spliced ​​together;

[0030] Figure 7 It is a flow chart of the method of the present invention.

[0031] In the figure: 1. Reinforcement ribs; 2. Crack-stop ribs; 3. Crack-stop holes; 4. Blind holes; 5. Countersunk holes; 6. Mounting bolts. DETAILED DESCRIPTION

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

[0033] Combined with Figure 1-7 As shown, a laser selective melting grafting printing method for a large-size metal thin-walled frame structure includes the following steps:

[0034] S1: A sub-base plate designed to carry laser selective melting printing, the material of the sub-base plate is consistent with the material of the large-size metal thin-walled frame structure, the large-size metal thin-walled frame structure is a three-dimensional structure with a groove body composed of a bottom surface with a flat surface and a metal thin-walled frame part arranged on one side of the bottom surface, the format size of the sub-base plate is larger than the format size of the bottom surface of the large-size metal thin-walled frame structure, the sub-base plate can be detachably installed in the center of the original base plate of the laser selective melting printing device used for laser selective melting printing, and the original base plate is located on the operating table of the laser selective melting printing device;

[0035] Specific:

[0036] For the present application, the secondary substrate format is the printing action surface of the laser selective melting printing, and the bottom surface format is the bearing surface of the bottom surface bearing the laser selective melting printing;

[0037] The bottom surface is in a quadrilateral structure, preferably in a rectangular structure, the metal thin-walled frame portion is composed of an outer frame connected end to end and an inner frame located inside the outer frame and dividing the outer frame into a plurality of troughs, and the outer frame is substantially vertically arranged on the bottom surface along the four sides of the bottom surface;

[0038] The thickness of the bottom surface does not exceed 2.5mm, the thickness of the sub-substrate is greater than the thickness of the bottom surface, when the shortest side of the bottom surface is ≤600mm, preferably, when the bottom surface width is ≤600mm, the thickness range of the sub-substrate is 50mm-100mm, when the shortest side of the bottom surface is greater than 600mm, preferably, when the bottom surface width is greater than 600mm, the thickness range of the sub-substrate is 25mm-40mm, preferably, the relationship between the bottom surface size and the sub-substrate size is shown in Table 1;

[0039] Table 1 Relationship between the bottom surface size of the large-size metal thin-wall frame structure and the size of the secondary substrate of the present invention

[0040] Model length(mm) Model width(mm) Sub-substrate length (mm) Sub-substrate width (mm) Sub-substrate thickness (mm) 1500 and above More than 1000 Model>30 Model>25 25-40 1200-1500 800-1000 Model>30 Compared with the model>20 25-35 1000-1200 600-800 Compared with the model>20 Model>15 25-30 Below 1000 Below 600 Compared with the model>10 Compared with the model>10 50-100

[0041] The chamfer of the edge of the sub-substrate is not less than R10, and the flatness of the sub-substrate is not more than 20 degrees;

[0042] The thickness of the original substrate is not less than 100 mm, and the flatness of the thick substrate is not more than 20 degrees. By adopting an original substrate of not less than 100 mm, the deformation probability of the parts can be reduced;

[0043] The side of the sub-base that does not bear printing is evenly provided with a plurality of blind holes 4 that are not through, the original base plate is provided with a plurality of countersunk holes 5 corresponding to the blind holes 4, and mounting bolts 6 are arranged in the countersunk holes 5. The sub-base plate is detachably connected to the original base plate through the mounting bolts 6 and the plurality of blind holes 4 and countersunk holes 5. The depth of the blind hole 4 is not less than 20 mm, and the distance from the side of the sub-base that bears printing to the blind hole 4 is greater than the thickness of the bottom surface. The length of the mounting bolt 6 after being inserted into the blind hole 4 is not less than 20 mm. By providing the blind holes 4 and the countersunk holes 5, the mounting bolts 6 are matched to facilitate the sub-base plate to be installed. The detachable installation between the board and the original substrate, the selection of the depth of the blind hole 4 and the selection of the corresponding thickness of the sub-substrate are determined according to factors such as the stress magnitude and the length of the matching mounting bolts 6. Generally, the larger the format, the greater the corresponding stress and the longer the mounting bolts 6 are required, so as to ensure the installation and fixation between the sub-substrate and the original substrate, thereby ensuring the stability of the fixation and preventing the sub-substrate and the original substrate from being separated due to the collapse of the mounting bolts 6 during the printing process or subsequent cooling or other reasons. The specific determination of the stress magnitude needs to be estimated according to the actual situation and the size and weight of the frame structure;

[0044] S2: inputting a modified three-dimensional model into the selective laser melting device, wherein the modified three-dimensional model includes a model of the metal thin-walled frame portion and a support model of a support structure for supporting the metal thin-walled frame portion during printing, and performing laser printing at the center of the secondary substrate according to the modified three-dimensional model to form an integrated structure combining the metal thin-walled frame portion, the support structure and the secondary substrate;

[0045] Specific:

[0046] The large-size metal thin-walled frame structure is a rectangular parallelepiped frame structure. The support structure is located on the sub-baseboard and connected to the bent portion of the outer frame. For the rectangular parallelepiped frame structure, its stress concentration is mainly concentrated on the bent portion. Further, the stress concentration is mainly concentrated at the angle where the frame structure and the sub-baseboard are connected. By setting the support structure, the risk of fracture and deformation at the connection angle is reduced. For other stress concentration locations on the frame structure, such as notches, holes, grooves and other locations, the support structure needs to avoid supporting such stress concentration locations, so as to avoid powder cleaning difficulties and interruption of the force transmission path, thereby ensuring the support effect.

[0047] The supporting structure includes reinforcing ribs 1 and crack-stopping ribs 2, the number of the reinforcing ribs 1 is several, several of the reinforcing ribs 1 are connected along the outer side of the outer frame and the front and rear positions of the bending part of the outer side of the outer frame, several of the reinforcing ribs 1 are connected to each other through the crack-stopping ribs 2, the reinforcing ribs 1 are connected to the sub-baseboard, the crack-stopping ribs 2 are connected to the sub-baseboard, and several crack-stopping holes 3 are arranged at the edge of the reinforcing ribs 1. Preferably, the number of the crack-stopping ribs 2 is several, and the relationship between the number of reinforcing ribs 1 and the crack-stopping ribs 2 and the bottom surface size is shown in Table 2. The width range of the reinforcing rib 1 is 4mm-10mm, the width of the crack-stopping rib 2 is 4mm-10mm, the spacing between two adjacent reinforcing ribs 1 is 6mm-15mm, and the spacing between two adjacent crack-stopping ribs 2 is 10mm-20mm. The spacing between them is 6mm-12mm, the diameter range of the crack stop hole 3 is 4mm-6mm, the spacing between two adjacent crack stop holes 3 is 3-5 times the diameter of the corresponding crack stop hole 3, and the distance between the crack stop hole 3 and the edge of the reinforcing rib 1 is not less than 1.5mm. By setting the reinforcing rib 1 and the crack stop rib 2, the purpose of supporting the bent part is achieved. Through the cracking of the crack stop hole 3 itself, the stress can be released, and the stress transfer is interrupted. In conjunction with the crack stop rib 2, the crack is prevented from expanding toward the frame direction. By setting the distance between the crack stop hole 3 and the edge of the reinforcing rib 1 to be not less than 1.5mm, if the distance is too small, it is difficult to form the crack stop hole 3. In addition, if the distance is too small, premature cracking may occur, thereby affecting the effect of releasing stress.

[0048] Table 2 Relationship between the bottom surface dimensions of the large-sized metal thin-walled frame structure of the present invention and the specifications and dimensions of the supporting structure

[0049]

[0050] S3: Cooling the integrated structure and the original substrate, taking the integrated structure and the original substrate out of the laser selective melting printing device, separating the secondary substrate from the original substrate, performing stress relief heat treatment on the integrated structure, and processing the secondary substrate to remove excess parts while retaining the bottom surface of the large-sized metal thin-walled frame structure;

[0051] Specific:

[0052] The processing includes wire cutting-machining and milling. When the shortest side of the bottom surface is ≤600mm, wire cutting-machining is adopted. Preferably, when the width of the bottom surface is ≤600mm, wire cutting-machining is adopted. When the shortest side of the bottom surface is greater than 600mm, milling is adopted. Preferably, when the width of the bottom surface is greater than 600mm, milling is adopted. When the wire cutting-machining is adopted, the part of the sub-substrate in the integrated structure except the bottom surface is wire cut, and the part of the sub-substrate remaining on the bottom surface after wire cutting is machined to form the bottom surface of a large-size metal thin-walled frame structure. The wire cutting-machining includes wire cutting and machining. When the milling is adopted, the part of the sub-substrate in the integrated structure except the bottom surface is machined. Milling is performed to form the bottom surface of a large-sized metal thin-walled frame structure. For the case where the shortest side of the bottom surface is ≤600mm, preferably, for the case where the bottom surface width is ≤600mm, when a 50mm-100mm sub-baseboard is used, due to the small size of the bottom surface, the corresponding sub-baseboard size is small, and a wire cutting process is used, so that the remaining sub-baseboard after cutting can be reused and reused as a subsequent sub-baseboard. For the case where the shortest side of the bottom surface is greater than 600mm, preferably, for the case where the bottom surface width is greater than 600mm, when a 25mm-40mm sub-baseboard is used, due to the large size of the bottom surface, it is difficult to use a wire cutting process, and a relatively thin sub-baseboard is selected to cooperate with milling processing, so that the sub-baseboard can be removed. At this time, the sub-baseboard cannot be used again;

[0053] S4: performing a cutting process of the support structure on the remaining part of the integrated structure after the processing to form a large-sized metal thin-wall frame structure;

[0054] Specific:

[0055] The modified three-dimensional model also includes a rounded corner model and a machined allowance model. The rounded corner model is located at the contact position between the metal thin-walled frame model and the sub-substrate, and the machined allowance model is located at the machined surface of the metal thin-walled frame in the metal thin-walled frame model. By setting the rounded corner model, the contact position between the metal thin-walled frame and the sub-substrate can be further avoided during subsequent printing. Correspondingly, the integrated structure also includes a rounded corner and a machined allowance. The processing also includes a rounded corner treatment and a machined allowance treatment. The rounded corner treatment is to process the rounded corner in the form of machining, and the machined allowance treatment is to process the machined allowance in the form of machining. In the process of machining the remaining part of the integrated structure after the processing to perform the support structure removal processing to form a large-size metal thin-walled frame structure, the rounded corner treatment and the machined allowance treatment are performed by machining to form a large-size metal thin-walled frame structure.

[0056] Take the large-size TC4 thin-wall frame structure as an example:

[0057] The bottom surface is a rectangular structure with a bottom width of 600mm and a thickness of 1.5mm. The frame structure height is 200mm. The thickness of the sub-baseboard is 50mm. The width of the sub-baseboard is selected according to Table 1. The sub-baseboard is made of TC4 material with a surface flatness of 20 wires and an edge chamfer of R10. The thickness of the original baseboard is 100mm. The original baseboard is 45# steel with a surface flatness of 20 wires. Accordingly, the depth of the blind hole 4 on the sub-baseboard is 20mm. Along the length direction of the sub-baseboard, the spacing between several blind holes 4 is 250mm. Along the width direction of the sub-baseboard, the spacing between several blind holes 4 is 200mm. The diameter of the blind hole 4 is 10mm. The original baseboard is provided with countersunk holes 5 corresponding to the blind holes 4. The sub-baseboard is placed in the center of the original baseboard and assembled by installing bolts 6. The assembled original baseboard and sub-baseboard are placed on the operating table of the laser selective melting printing equipment. The sub-baseboard is located above the original baseboard. , a modified three-dimensional model is generated according to the specific conditions of the bottom surface thickness and the frame structure, wherein the fillet of the fillet model is R3, the thickness of the machining allowance model is 2mm, the number of reinforcing ribs 1 is two, the number of crack stop ribs 2 is one, the width of the reinforcing rib 1 in the support model is 6mm, the width of the crack stop rib 2 is 6mm, the spacing between the reinforcing ribs 1 is 8mm, the distance between the crack stop rib 2 and the frame structure is 8mm, the diameter of the crack stop hole 3 is 4mm, the spacing between the crack stop holes 3 is 20mm, and the distance between the crack stop hole 3 and the reinforcing rib 1 is 1.5mm. Subsequently, corresponding laser printing is performed according to the corresponding modified three-dimensional model to form an integrated structure, and then the integrated structure is stress-relieved, and the integrated structure after the stress-relieved treatment is processed, and then the processed integrated structure is subjected to the cutting of the support structure, the fillet processing of the fillet part, and the machining allowance processing of the machining allowance part.

[0058] Take the large-size GH4169 thin-wall frame structure as an example:

[0059] The bottom surface is a rectangular structure with a bottom width of 1000mm and a thickness of 2.5mm. The frame structure height is 300mm. The thickness of the sub-baseboard is 30mm. The width of the sub-baseboard is selected according to Table 1. The sub-baseboard is made of GH4169 material with a surface flatness of 20 wires and an edge chamfer of R10. The thickness of the original baseboard is 150mm. The original baseboard is 45# steel with a surface flatness of 20 wires. Correspondingly, the depth of the blind hole 4 on the sub-baseboard is 25mm. Along the length direction of the sub-baseboard, the spacing between several blind holes 4 is 300mm. Along the width direction of the sub-baseboard, the spacing between several blind holes 4 is 250mm. The diameter of the blind hole 4 is 15mm. The original baseboard is provided with countersunk holes 5 corresponding to the blind holes 4. The sub-baseboard is placed in the center of the original baseboard and assembled by installing bolts 6. The assembled original baseboard and sub-baseboard are placed on the operating table of the laser selective melting printing equipment. The sub-baseboard is located above the original baseboard. According to the bottom thickness The modified three-dimensional model is generated according to the specific conditions of the degree and frame structure, wherein the fillet of the fillet model is R5, the thickness of the machining allowance model is 4mm, the number of stiffeners 1 is three, the number of crack stop ribs 2 is two, the width of the stiffener 1 in the support model is 8mm, the width of the crack stop rib 2 is 8mm, the spacing between the stiffeners 1 is 10mm, the distance between the crack stop rib 2 and the frame structure is 10mm, the distance between the two crack stop ribs 2 is 10mm, the diameter of the crack stop hole 3 is 5mm, the spacing between the crack stop holes 3 is 25mm, and the distance between the crack stop hole 3 and the stiffener 1 is 2mm. Subsequently, corresponding laser printing is performed according to the corresponding modified three-dimensional model to form an integrated structure, and then the integrated structure is stress-relieved, and the integrated structure after the stress-relief treatment is processed, and then the processed integrated structure is subjected to the cutting of the support structure, the fillet treatment of the fillet part, and the machining allowance treatment of the machining allowance part.

[0060] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. The above embodiments and the description in the specification are only preferred examples of the present invention and are not intended to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of the present invention to be protected is defined by the attached claims and their equivalents.

Claims

1. A laser selective melting grafting printing method for a large-size metal thin-walled frame structure, characterized in that: The steps include: S1: A sub-base plate designed to carry laser selective melting printing, the material of the sub-base plate is consistent with the material of the large-size metal thin-walled frame structure, the large-size metal thin-walled frame structure is a three-dimensional structure with a groove body composed of a bottom surface with a flat surface and a metal thin-walled frame part arranged on one side of the bottom surface, the format size of the sub-base plate is larger than the format size of the bottom surface of the large-size metal thin-walled frame structure, and the sub-base plate can be detachably installed in the center of the original base plate of the laser selective melting printing device for laser selective melting printing; S2: inputting a modified three-dimensional model into the selective laser melting device, wherein the modified three-dimensional model includes a model of the metal thin-walled frame portion and a support model of a support structure for supporting the metal thin-walled frame portion during printing, and performing laser printing at the center of the secondary substrate according to the modified three-dimensional model to form an integrated structure combining the metal thin-walled frame portion, the support structure and the secondary substrate; S3: taking out the integrated structure and the original substrate from the laser selective melting printing device, separating the secondary substrate from the original substrate, performing stress relief heat treatment on the integrated structure, and processing the secondary substrate to remove excess parts while retaining the bottom surface of the large-sized metal thin-walled frame structure; S4: performing a cutting process of the supporting structure on the remaining part of the integrated structure after the processing to form a large-sized metal thin-wall frame structure.

2. According to claim 1, a large-size metal thin-wall frame structure laser selective melting grafting printing method is characterized in that: The bottom surface is a quadrilateral structure, and the metal thin-wall frame portion is composed of an outer frame connected end to end and an inner frame located inside the outer frame to divide the outer frame into a plurality of troughs. The outer frame is vertically arranged on the bottom surface roughly along the four sides of the bottom surface.

3. According to claim 2, a large-size metal thin-wall frame structure laser selective melting grafting printing method is characterized in that: The supporting structure is located on the secondary substrate and is connected to the bent portion outside the outer frame.

4. According to claim 3, a large-size metal thin-wall frame structure laser selective melting grafting printing method is characterized in that: The support structure comprises reinforcing ribs (1) and crack-stopping ribs (2), the number of the reinforcing ribs (1) is several, several of the reinforcing ribs (1) are connected along the outer side of the outer frame and at the front and rear positions of the bending part of the outer side of the outer frame, several of the reinforcing ribs (1) are connected to each other through the crack-stopping ribs (2), the crack-stopping ribs (2) are connected to the sub-baseboard, and several crack-stopping holes (3) are arranged at the edge positions of the reinforcing ribs (1).

5. The method for laser selective melting grafting printing of a large-size metal thin-walled frame structure according to claim 2 is characterized in that: The thickness of the bottom surface does not exceed 2.5mm, the thickness of the sub-substrate is greater than the thickness of the bottom surface, when the shortest side of the bottom surface is ≤600mm, the thickness range of the sub-substrate is 50mm-100mm, when the shortest side of the bottom surface is >600mm, the thickness range of the sub-substrate is 25mm-40mm.

6. The method for laser selective melting grafting printing of a large-size metal thin-walled frame structure according to claim 1 is characterized in that: The side of the secondary substrate that does not bear printing is evenly provided with a plurality of blind holes (4) that are not through, the original substrate is provided with a plurality of countersunk holes (5) corresponding to the blind holes (4), the countersunk holes (5) are provided with mounting bolts (6), and the secondary substrate and the original substrate are detachably mounted and connected via the mounting bolts (6) and the plurality of blind holes (4) and the countersunk holes (5).

7. The method for laser selective melting grafting printing of a large-size metal thin-walled frame structure according to claim 6 is characterized in that: The depth of the blind hole (4) is not less than 20 mm, and the distance from the side of the secondary substrate that bears printing to the blind hole (4) is greater than the thickness of the bottom surface.

8. The method for laser selective melting grafting printing of a large-size metal thin-walled frame structure according to claim 7 is characterized in that: The length of the mounting bolt (6) after being inserted into the blind hole (4) is not less than 20 mm.

9. The method for laser selective melting grafting printing of a large-size metal thin-walled frame structure according to claim 5, characterized in that: The chamfer of the edge of the auxiliary substrate is not less than R10, the flatness of the auxiliary substrate is not more than 20 degrees, the thickness of the original substrate is not less than 100 mm, and the flatness of the thick substrate is not more than 20 degrees.

10. The method for laser selective melting grafting printing of a large-size metal thin-walled frame structure according to claim 5, characterized in that: The processing includes wire cutting-machining and milling. Wire cutting-machining is used when the shortest side of the bottom surface is ≤600mm, and milling is used when the shortest side of the bottom surface is >600mm. When the wire cutting-machining is used, the part of the sub-substrate in the integrated structure except the bottom surface is wire cut, and the part of the sub-substrate remaining on the bottom surface after wire cutting is machined to form the bottom surface of a large-size metal thin-walled frame structure. When the milling is used, the part of the sub-substrate in the integrated structure except the bottom surface is milled to form the bottom surface of a large-size metal thin-walled frame structure.

Images