High-precision additive manufacturing method for open type thin-wall cabin section

Abstract

The invention discloses a high-precision additive manufacturing method for an open type thin-wall cabin section, and belongs to the technical field of additive manufacturing. According to the method, the additive manufacturing direction is set to take the middle part of an open structure as the bottom, and latticed strong constraint is performed; the two open end faces are closed, and the open cabin section is converted into a near-closed cabin section; an interlayer shape-maintaining supporting structure is designed for the thin-wall structures on the two sides in a shape-following mode, and the two side walls with the low rigidity are converted into stable interlayer structures; and extended supporting rib plates are designed at four corners. And the dimensional structure is removed after stress relief heat treatment, and finally a high-precision additive manufacturing open type thin-wall cabin section product is obtained. An open structure is converted into a more stable closed structure, and by means of the interlayer design, the structural deformation risk is greatly reduced, and no extra shape correcting tool needs to be manufactured; and supporting structures such as bottom grids and rib plates are hollowed out, so that the high-precision profile level of a formed product is guaranteed, and meanwhile, the cost input is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of additive manufacturing, and in particular relates to a high-precision additive manufacturing method for an open thin-walled cabin section. Background Art

[0002] Additive manufacturing is a manufacturing technology that has developed rapidly in recent years. It is based on digital models and obtains processing procedures through layered slicing, path planning, etc. It directly forms structural parts by adding materials layer by layer. It has the advantages of no need for molds, high efficiency, and low development cost. In recent years, it has been widely used in high-end manufacturing fields such as aerospace.

[0003] With the development of high-end manufacturing technology, the structural form of cabin parts is becoming more complex and the wall thickness is becoming thinner. Traditional cabin structures are mostly closed circular, square, and polygonal cabins with closed cross-sections. The structural shape is relatively stable in all production links. However, in order to meet the needs of some assembly and use conditions, some new cabin structures are designed as split open cabins, which are manufactured separately and then assembled. Typical open thin-walled cabin structures are as follows: Figure 1 As shown in the figure, its shape is open in at least two directions, and the wall thickness X is generally ≤3mm. This split open thin-walled cabin section often has the characteristics of thin wall thickness, multiple features, and complex structure, and high surface accuracy is required in actual use. In order to meet the needs of rapid development, the new open thin-walled cabin section can be formed by additive manufacturing. However, due to the cumulative thermal stress of the additive manufacturing process, it is very easy to cause large deformation or even cracking of the open thin-walled structure.

[0004] In the deformation control of additively manufactured cabin products, rib and lattice dimensional shaping, pre-reverse deformation, thermal correction and other methods can be used to improve the shape accuracy. Rib and lattice dimensional shaping, pre-reverse deformation methods can have a good shape control effect for regular and closed cabins, but the deformation tendency of open thin-walled cabins is very large. The shape control effect of only using ribs and lattices is not good, and it is difficult to adopt pre-reverse deformation under large deformation. At the same time, the structural stability of open thin-walled cabins is low. Not only will large deformations occur during the additive process, but also in the subsequent heat treatment, support removal and other links, deformations that are difficult to predict will occur. Therefore, traditional rib and lattice dimensional shaping, pre-reverse deformation methods cannot achieve high-precision manufacturing of such structural parts. Although the thermal correction method can theoretically improve the shape accuracy of the cabin, the time and economic cost of developing the corresponding correction tooling are high, and generally cannot meet the development and use requirements. Therefore, there is no effective high-precision additive manufacturing method for open thin-walled cabin structures. Summary of the invention

[0005] The technical problem solved by the present invention is: to overcome the shortcomings of the prior art and provide a high-precision additive manufacturing method for an open thin-walled cabin section. The open structure is converted into a more stable closed structure, and the weak rigid thin-walled structure is converted into a sandwich structure with better rigidity by means of sandwich design. The structural rigidity is significantly improved, and the risk of cracking and deformation during the additive and heat treatment process is greatly reduced.

[0006] The technical solution of the present invention is:

[0007] A high-precision additive manufacturing method for an open thin-walled cabin section comprises the following steps:

[0008] Step 1: The additive manufacturing model is selected such that the additive direction is the middle part of the open structure as the bottom, a strong grid constraint is applied to the bottom surface, and the bottom surface grid formed is used as the bottom support;

[0009] Step 2: Close the two open ends, and after closing, the open cabin section is transformed into a nearly closed cabin section;

[0010] Step 3: Design a conformal sandwich-shaped dimensional support structure for the thin-walled structures on both sides to transform the two side walls with weaker rigidity into a stable sandwich structure;

[0011] Step 4: Design extended support ribs at the four corners;

[0012] Step 5: Design the bottom surface grid of step 1, the closed structure of step 2, the conformal sandwich dimensional support structure of step 3, and the extended support ribs of step 4 into a hollow structure that can be self-formed by additive manufacturing;

[0013] Step 6: Add additive overhanging surface support to the designed additive manufacturing model, and then perform additive manufacturing;

[0014] Step 7: After the additive manufacturing is completed, stress relief annealing is performed according to the use requirements, and then the bottom grid, two conformal sandwich-shaped dimensional support structures, and four corner extended support ribs are cut away along the outer contour of the product; finally, the residual support structure is removed to obtain a high-precision additively manufactured open thin-walled cabin product.

[0015] Preferably, in step one, the wall thickness of the bottom surface grid body is (2 to 4) times the wall thickness of the middle part of the additive manufacturing model, and the connection part with the additive manufacturing model is thinned to (0.5 to 1) times the wall thickness of the middle part of the model.

[0016] Preferably, in step 2, when the open two end faces are closed, if a sealing plate is used for sealing, the thickness of the sealing plate is (3 to 5) times the wall thickness of the additive manufacturing model body; if a dot matrix is ​​used for sealing, the overall thickness of the dot matrix is ​​(0.1 to 0.2) times the distance between the two end faces.

[0017] Preferably, in step three, the conformal sandwich-shaped dimensional support structure includes three parts: a conformal outer plate, an inner sandwich rib perpendicular to the model surface, and an internal filling sandwich structure; the conformal outer plate is a plate-like structure whose shape conforms to the outer shape of the thin walls on both sides and falls on the additive substrate; the sandwich ribs are evenly distributed on the thin walls on both sides and are at a normal angle to the thin wall surface, connecting the model side wall and the conformal outer plate; the internal filling sandwich structure is a lattice or grid-shaped rib.

[0018] Preferably, in step 4, the height of the four corner extended support ribs is consistent with the height of the model at the location, and square or round solid columns are designed at the ends.

[0019] Preferably, in step five, the self-formed hollow structure is in the form of a circle or a diamond.

[0020] Preferably, the additive manufacturing method is suitable for additive manufacturing of elliptical parts made of any alloy material.

[0021] Preferably, the additive manufacturing method is suitable for high-precision additive manufacturing of open thin-walled cabins using various additive processes.

[0022] Preferably, the additive process includes laser selective melting, electron beam selective melting, photocuring, and direct energy deposition process.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) Based on the structural characteristics of the open thin-walled structure, the present invention transforms the open structure into a more stable closed structure through a dimensional support structure design, and transforms the weak rigid thin-walled structure into a sandwich structure with better rigidity through sandwich design. This significantly improves the structural rigidity and greatly reduces the risk of cracking and deformation during the material addition and heat treatment process.

[0025] (2) The sealing plate, sandwich ribs and other structures used in the present invention can be integrated with the part body by additive manufacturing, and no additional shape calibration and shape maintenance tooling is required, so that a better surface accuracy control effect can be achieved.

[0026] (3) The end face sealing plate used in the present invention not only plays a shape-controlling role in the additive manufacturing process, but also plays a shape-controlling role in the subsequent heat treatment and machining processes, which can reduce the use of tooling in the subsequent processing process and ensure the shape and surface accuracy of the final delivered product.

[0027] (4) The main sandwich dimensional support structure of the present invention is simple in form and can be quickly removed by cutting processing methods, ensuring the work efficiency of the support removal process. At the same time, the present invention takes into account the need to reduce costs and increase efficiency in actual production. On the premise of improving the manufacturing rigidity effect, the bottom grid, ribs and other support structures are hollowed out, while ensuring the high-precision surface level of the formed product, reducing cost investment. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic diagram of the open thin-walled cabin structure;

[0029] Figure 2 It is a flow chart of the present invention;

[0030] Figure 3 This is a schematic diagram of the dimensions of an open thin-walled cabin section in an embodiment;

[0031] Figure 4 A diagram of a dimensional support structure designed according to the method of the present invention is shown in the following example;

[0032] Figure 5 A schematic diagram of a thinning structure designed according to the method of the present invention is shown in the embodiment;

[0033] Figure 6 Deformation results of direct additive manufacturing of the embodiment;

[0034] Figure 7 1 is the deformation result of additive manufacturing after shape control according to the method of the present invention. DETAILED DESCRIPTION

[0035] The present invention will be described in detail below based on specific embodiments and in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0036] For open thin-walled cabin sections, due to their weak structural rigidity and instability, when laser selective melting additive manufacturing is used, it is often easy to cause cracking and large deformation under the action of large internal stress, making it difficult to achieve high-precision manufacturing. The present invention proposes a high-precision additive manufacturing method for open thin-walled cabin sections. The additive manufacturing direction is set to take the middle part of the open structure as the bottom, and a grid-like strong constraint bottom support connection is made; the open two end faces are closed by sealing plates, lattice and other structures to convert the open cabin section into a nearly closed cabin section; further, a sandwich-like dimensional support structure is designed for the thin-walled structures on both sides to convert the two side walls with weak rigidity into a stable sandwich structure; finally, extended support ribs are designed for the four corners to disperse stress concentration and large deformation to the extended support ribs. The above-mentioned dimensional structure is removed by wire cutting, grinding and other methods after stress relief heat treatment, and finally a high-precision additive manufacturing open thin-walled cabin section product is obtained.

[0037] The present invention provides a high-precision additive manufacturing method for an open thin-walled cabin section, according to Figure 2 Follow the steps shown.

[0038] Step 1: Select the additive direction of the additive manufacturing model: the middle part of the open structure is the bottom. Make a strong grid constraint on the bottom part and use it as the bottom support to ensure the stability of the bottom structure.

[0039] The size of each grid is between (20×20) and (100×100) mm, the wall thickness of the main body is (2 to 4) times the wall thickness of the middle part of the model, and the wall thickness at the connection part with the model is thinned to (0.5 to 1) times the wall thickness of the middle part of the model.

[0040] Step 2: The open end faces are closed with sealing plates, lattice structures, etc., thus converting the open cabin section into a nearly closed cabin section.

[0041] If a sealing plate is used for closure, the thickness of the sealing plate is (3 to 5) times the thickness of the model body wall; if a lattice is used for closure, the overall thickness of the lattice is (0.1 to 0.2) times the distance between the two end faces, the lattice cell size is (0.2 to 0.5) times the overall thickness of the lattice, and the lattice rod diameter is (0.5 to 0.8) times the thickness of the model body wall.

[0042] Step 3: Design a sandwich-shaped dimensional support structure for the thin-walled structures on both sides to transform the two side walls with weaker rigidity into a stable sandwich structure.

[0043] The conformal sandwich dimensional support structure consists of three parts: the conformal outer plate, the inner sandwich rib plate perpendicular to the model surface, and the internal filling sandwich structure.

[0044] The conformal outer plate is located at a distance of (15 to 30) mm from the side wall, has a thickness of (2 to 4) times the thickness of the main wall of the model, and has a shape similar to the outer shape of the thin walls on both sides and a plate-like structure that falls on the additive substrate.

[0045] The sandwich ribs are evenly distributed on the side walls and are at a normal angle to the side wall surface. They connect the side walls of the model with the conformal outer plate. The thickness is (1 to 2) times the thickness of the main wall of the model. The thickness is reduced to (0.5 to 0.9) times the thickness of the main wall of the model at the connection with the model.

[0046] The internal filling sandwich structure can be a lattice or grid rib. If a lattice is used, the lattice cell size is (0.2-0.5) times the overall thickness of the lattice, and the lattice rod diameter is (0.5-0.8) times the thickness of the model body wall; if a grid rib is used, the grid can be a rhombus, hexagon or other polygonal shape, with a thickness of (0.5-0.8) times the thickness of the model body wall, and at a normal angle to the side wall surface.

[0047] Step 4: Design extended support ribs at the four corners to disperse stress concentration and large deformation to the extended support ribs.

[0048] The height of the extended support ribs at the four corners is consistent with the height of the model at the location, and the thickness is (1.5-3) times the thickness of the main wall of the model. Square or round solid columns are designed at the ends to further disperse the stress. The side length of the square solid column is (2-4) times the thickness of the support rib; the diameter of the round solid column is (2-4) times the thickness of the support rib.

[0049] Step 5: Design the bottom grid, ribs, lattice and other dimensional supports into a self-forming hollow structure, which can reduce the weight of additive manufacturing materials, improve production efficiency and reduce production costs. The self-forming hollow structure includes circular, diamond and other hollow structures.

[0050] Step 6: After adding additive suspended surface support to the designed model, perform additive manufacturing.

[0051] Step 7: After the additive manufacturing is completed, stress relief annealing is performed according to the use requirements. Then, the bottom grid, two sandwich supports, and four corner extended support rib structures are cut along the outer contour of the product by wire cutting or manual cutting. Finally, the residual support structure is removed by grinding, machining, etc., and finally a high-precision additive manufacturing open thin-wall cabin product is obtained.

[0052] The invention is suitable for additive manufacturing of elliptical parts made of any material such as titanium alloy, high-temperature alloy, aluminum alloy, etc.

[0053] The present invention is applicable to high-precision additive manufacturing of open thin-wall cabin sections using various additive processes such as laser selective melting, electron beam selective melting, photocuring, and direct energy deposition.

[0054] Example:

[0055] like Figure 3 As shown, the embodiment is an open thin-walled cabin section, made of titanium alloy, with a length of 300 mm, a U-shaped cross section, an arc radius of R150 mm, a cross section width of 300 mm, a height of 350 mm, and a wall thickness of 2 mm. The model designed according to the method of the present invention is shown in FIG. Figure 4 As shown, perform the following operations:

[0056] Step 1: The additive manufacturing model is selected to have the additive direction: the middle part of the open structure is the bottom, that is, the arc part of the "U"-shaped cross section in the embodiment is the bottom. The bottom part is strongly constrained in a grid-like manner to connect to the bottom support to ensure the stability of the bottom structure.

[0057] The size of the bottom grid 1 is set to (80×100) mm, the grid wall thickness is 5 mm, and the thinning at the connection with the model is 1.5 mm. The thinning structure is as follows Figure 5 shown.

[0058] Step 2: Use dot matrix to close the two end faces of the open thin-walled cabin section, thus converting the open cabin section into a nearly closed cabin section.

[0059] The thickness of the lattice 2 area at both ends is 20mm, that is, the overall thickness is 40mm. The lattice cell size is 10mm, and the lattice rod diameter is 1mm.

[0060] Step 3: Design a sandwich-shaped dimensional support structure for the thin-walled structures on both sides to transform the two side walls with weaker rigidity into a stable sandwich structure.

[0061] The conformal sandwich dimensional support structure is composed of three parts: one is the conformal outer plate 3, the second is the inner sandwich rib plate 4 perpendicular to the model surface, and the third is the internal filling sandwich structure 5.

[0062] The conformal outer plate is located 20 mm away from the side wall, has a thickness of 4 mm, and is in the shape of a plate-like structure parallel to the outer shape of the thin walls on both sides, and is connected to the additive substrate.

[0063] The sandwich rib is perpendicular to the side wall of the product and connects the side wall of the model with the outer plate of the conformal shape. The thickness is 3mm, and the thickness is reduced to 1.5mm at the connection with the model.

[0064] The internal filling sandwich structure is designed as a diamond grid-like rib plate with a thickness of 1 mm and a normal angle to the side wall surface.

[0065] Step 4: Design extended support ribs at the four corners to disperse stress concentration and large deformation to the extended support ribs.

[0066] The height of the four extended support ribs 6 is consistent with the height of the model at the location, with a thickness of 3 mm. A circular solid column is designed at the end to further disperse the stress. The diameter of the circular solid column is 6 mm.

[0067] Step 5: Design the bottom grid, ribs, lattice and other dimensional supports into a self-forming hollow structure, which can reduce the weight of additive manufacturing materials, improve production efficiency and reduce production costs. The self-forming hollow structure includes circular, diamond and other hollow structures.

[0068] Step 6: After adding additive suspended surface support to the designed model, additive manufacturing is performed. Before additive manufacturing, the deformation results of additive manufacturing using the original model and additive manufacturing using the method of the present invention are simulated. The results are as follows: Figure 6 and Figure 7 It can be seen that after adopting the method of the present invention, the large deformations of the original cabin section are completely eliminated, and the local maximum deformation is reduced from 13 mm to within 0.3 mm.

[0069] Step 7: After forming, stress relief annealing is performed to remove the internal stress of the product, and then wire cutting or manual cutting is used to cut off the bottom grid, two sandwich supports, and four corner extended support rib structures along the outer contour of the product. Finally, the residual support structure is removed by grinding, machining, etc., and finally a high-precision additive manufacturing open thin-wall cabin product is obtained.

[0070] The above description is only the best specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

[0071] The contents not described in detail in the specification of the present invention belong to the common knowledge of the professionals in this field.

Claims

1. A high-precision additive manufacturing method for an open thin-walled cabin section, characterized in that: The steps include: Step 1: The additive manufacturing model is selected such that the additive direction is the middle part of the open structure as the bottom, a strong grid constraint is applied to the bottom surface, and the bottom surface grid formed is used as the bottom support; Step 2: Close the two open ends, and after closing, the open cabin section is transformed into a nearly closed cabin section; Step 3: Design a conformal sandwich-shaped dimensional support structure for the thin-walled structures on both sides to transform the two side walls with weaker rigidity into a stable sandwich structure; Step 4: Design extended support ribs at the four corners; Step 5: Design the bottom surface grid of step 1, the closed structure of step 2, the conformal sandwich dimensional support structure of step 3, and the extended support ribs of step 4 into a hollow structure that can be self-formed by additive manufacturing; Step 6: Add additive overhanging surface support to the designed additive manufacturing model, and then perform additive manufacturing; Step 7: After the additive manufacturing is completed, stress relief annealing is performed according to the use requirements, and then the bottom grid, two conformal sandwich-shaped dimensional support structures, and four corner extended support ribs are cut away along the outer contour of the product; finally, the residual support structure is removed to obtain a high-precision additively manufactured open thin-walled cabin product.

2. A high-precision additive manufacturing method for an open thin-walled cabin section according to claim 1, characterized in that: In step 1, the wall thickness of the bottom mesh body is (2 to 4) times the wall thickness of the middle part of the additive manufacturing model, and the connection part with the additive manufacturing model is thinned to (0.5 to 1) times the wall thickness of the middle part of the model.

3. A high-precision additive manufacturing method for an open thin-walled cabin section according to claim 1, characterized in that: In step 2, when the open two end faces are closed, if a sealing plate is used for closing, the thickness of the sealing plate is (3 to 5) times the wall thickness of the additive manufacturing model body; if a dot matrix is ​​used for closing, the overall thickness of the dot matrix is ​​(0.1 to 0.2) times the distance between the two end faces.

4. A high-precision additive manufacturing method for an open thin-walled cabin section according to claim 1, characterized in that: In step three, the conformal sandwich dimensional support structure includes three parts: a conformal outer plate, an inner sandwich rib perpendicular to the model surface, and an internal filling sandwich structure; the conformal outer plate is a plate-like structure whose shape conforms to the outer shape of the thin walls on both sides and falls on the additive substrate; the sandwich ribs are evenly distributed on the thin walls on both sides and are normal to the surface of the thin walls, connecting the model side walls and the conformal outer plate; the internal filling sandwich structure is a lattice or grid-shaped rib.

5. The high-precision additive manufacturing method for an open thin-walled cabin section according to claim 1, characterized in that: In step 4, the height of the four corner extended support ribs is consistent with the height of the model at the location, and square or round solid columns are designed at the ends.

6. A high-precision additive manufacturing method for an open thin-walled cabin section according to claim 1, characterized in that: In step five, the self-formed hollow structure is in the form of a circle or a diamond.

7. A high-precision additive manufacturing method for an open thin-walled cabin section according to claim 1, characterized in that: The additive manufacturing method is suitable for additive manufacturing of elliptical parts made of any alloy material.

8. The high-precision additive manufacturing method for an open thin-walled cabin section according to claim 1, characterized in that: The additive manufacturing method is suitable for high-precision additive manufacturing of open thin-walled cabins using various additive processes.

9. A high-precision additive manufacturing method for an open thin-walled cabin section according to claim 8, characterized in that: The additive process includes laser selective melting, electron beam selective melting, photocuring, and direct energy deposition process.

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