Additive manufacturing method for lightweight integrated multi-cavity structural component

Abstract

The invention provides a lightweight integrated multi-cavity structural member additive manufacturing method, which comprises the following steps of: firstly, selecting a forming direction, designing a self-forming structure for a partition structure between cavities on the aspect of process model design, and realizing multi-cavity integrated forming; the requirements for integration and light weight of products are further met, and an integrated pipeline based on topological optimization, self-forming ribs and a rib plate or variable-density lattice structure used for supporting the surface which is internally suspended or cannot be self-formed are designed. And in order to consider the problems of redundant material cleaning and detection, process hole structures which are communicated with one another and are communicated with the outside are designed at the lowest point in the forming direction of each cavity, and the design of the lightweight integrated multi-cavity structure additive process model is completed. And after additive manufacturing is completed according to the selected forming direction, redundant materials such as residual powder and liquid are thoroughly removed by means of the designed process holes, and finally additive manufacturing of the light-weight integrated multi-cavity structure is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of additive manufacturing, and in particular relates to an additive manufacturing method for a lightweight integrated multi-cavity structural component. Background Art

[0002] With the development of additive manufacturing technology, the technology of manufacturing one-piece structural parts by utilizing the characteristics of additive manufacturing "additive material forming" has been widely used. One-piece formed structural parts generally have a single cavity, and functional structures such as pipelines and ribs can be integrated inside the cavity. In order to further give play to the advantages of "integrated" forming of additive manufacturing, it is further considered to integrate components with multiple cavities to form an integrated part. However, when a structural part has multiple cavities, due to the presence of a large number of suspended surfaces in the direction of additive forming and poor cavity connectivity, the weight of the formed structural part increases, the excess material is difficult to remove, and additive manufacturing is extremely difficult.

[0003] In order to solve such problems and improve the quality of complex structure laser selective melting forming structures, CN 117773152A "Detail Optimization Design Method for Laser Selective Melting Multi-Ring Multi-Cavity Thin-Wall Complex Structure Parts" proposes to optimize the details of characteristic structures such as reinforcing ribs, right angles or sharp angles, thin walls, small gaps, and closed cavities to reduce the stress concentration of these parts during the laser selective melting forming process, thereby avoiding deformation and cracking and improving the quality of the formed parts. However, these detail optimizations can only ensure the smooth forming of structural parts. For the additive manufacturing of one-piece multi-cavity structures, it is impossible to solve the problem that the excess materials such as powder and liquid in the inner cavity of the formed parts are difficult to clean, and the suspended surface support or self-forming structure causes a large amount of weight gain. Therefore, for one-piece multi-cavity structural parts, there is no effective additive manufacturing method that can take into account lightweight, forming quality, and excess material control. Summary of the invention

[0004] The technical problem solved by the present invention is to overcome the deficiencies of the prior art and provide a method for additive manufacturing of a lightweight integrated multi-cavity structural part.

[0005] The technical solution of the present invention is:

[0006] A method for additive manufacturing of a lightweight integrated multi-cavity structural component comprises the following steps:

[0007] Step 1: Design the inter-cavity partition structure that is suspended or has an insufficient forming angle in the forming direction into a self-forming structure while maintaining its function of dividing the cavity area to achieve multi-cavity integrated direct forming;

[0008] Step 2: Design an integrated pipeline based on topology optimization, and connect it with the surrounding structure using the least material; the topology optimization method is: connect the bottom surface of the pipeline in the forming direction with the surrounding structure of the product to form a connecting plate, set the design input as the plate bearing structural warping stress, the connection surface with the surrounding structure as a fixed surface, the non-calculation threshold as the peripheral area of ​​the plate, the calculation threshold as the central area of ​​the plate, the topology algorithm as maximum rigidity, the material reduction as (50-70)%, and the peripheral area of ​​the plate as the boundary of the plate offset inward by (1-5) mm;

[0009] Step 3: Design the self-forming ribs according to the self-forming angle of step 1;

[0010] Step 4: Design a support structure under the structure that still cannot self-form inside the cavity, wherein the support structure is a self-forming rib plate or a variable density lattice, and the support structure is still retained after the structural component is manufactured;

[0011] Step 5: at least one interconnected process hole structure is designed at the lowest point in the forming direction of each cavity to interconnect the multi-cavity structures; at least one process hole connected to the outside is designed at the lowest point in the forming direction of the interconnected multi-cavity structure to discharge the internal excess; at least one process hole structure connected to the outside is designed on the top surface in the forming direction of each cavity connected to the outside to clean and inspect the excess;

[0012] Step 6: Add necessary supports to the outside of the structural part according to the selected forming direction. The added supports cannot cover the designed process hole structure connected to the outside world, and complete the additive process model design;

[0013] Step 7: Complete the additive manufacturing process according to the additive manufacturing process selected in step 1;

[0014] Step 8: After the additive manufacturing is completed, the process hole structure designed in step 5 is used to thoroughly clean the excess material remaining inside;

[0015] Step 9: Complete the subsequent drying, heat treatment, support removal, grinding, and machining processes to achieve additive manufacturing of lightweight integrated multi-cavity structures.

[0016] Preferably, the self-forming structure includes, but is not limited to: an inclined plate and a "pyramid" shaped plate which are at a certain angle to the horizontal direction.

[0017] Preferably, in step 2, the outer diameter of the integrated pipeline is denoted as R, and the thickness of the connecting plate is 1 / 3R~R.

[0018] Preferably, in step three, if the self-forming rib is a hollow rib, it must be ensured that each independent cavity space has at least one hole / groove structure communicating with the outside.

[0019] Preferably, in step three, the outer contour of the self-forming rib is a triangle, the upper surface is in contact with the supported structure and is (1 to 5) mm away from the edge of the structure; the side is in contact with the adjacent self-forming surface; and the bevel angle is designed according to the self-forming angle of step one.

[0020] Preferably, the self-forming rib is designed as a hollow structure based on topological optimization, and the topological optimization method is: setting the design input as the upper surface of the triangular rib to bear the structural warping stress, the non-calculation threshold is the peripheral area of ​​the triangular plate, the calculation threshold is the central area of ​​the triangular plate, the topological algorithm is maximum rigidity, the material reduction is (50~70)%, and the peripheral area of ​​the plate is the boundary of the plate offset inward by (1~4) mm.

[0021] Preferably, in step five, the shape of the process hole includes circular, semicircular, and rectangular.

[0022] Preferably, the method of inspecting excess material using the process hole structure includes but is not limited to endoscopic inspection and visual inspection.

[0023] Preferably, in step 1, the self-forming angle refers to the angle between the structure and the horizontal plane where the additive forming is performed.

[0024] Preferably, in step eight, cleaning the residual waste inside includes: high-pressure gas cleaning, high-pressure liquid flushing, and liquid rinsing; during the cleaning process, X-ray or endoscope inspection is used to perform real-time inspection on the residual waste in the inner cavity until the residual waste is completely cleaned;

[0025] The gas includes air and inert gas; the liquid includes water, anhydrous ethanol, acetone, gasoline and special cleaning agent.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) The present invention takes into account both the processability of additive manufacturing and the functionality of structural parts, designs partitions, pipelines and other structures based on the additive forming direction, and realizes the integrated forming of multi-cavity structures, thereby significantly reducing the number of parts of complex structural parts and improving product development efficiency.

[0028] (2) The present invention takes into account the structural weight on the basis of integrated forming, and makes extreme lightweight design based on topological optimization in the design of pipelines, ribs, and internal supporting structures without removing them, thereby retaining functionality while minimizing weight.

[0029] (3) Based on the one-piece forming effect, the present invention can effectively solve the problem that the excess materials inside the multi-cavity structure are difficult to remove and detect. Through the design of process holes and the method of cleaning and detecting after forming, the excess materials can be completely removed to meet the needs of engineering applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a flow chart of the present invention;

[0031] Figure 2 This is a schematic diagram of an open thin-walled cabin section in an embodiment;

[0032] Figure 3 This is a schematic diagram of an integrated multi-cavity structure of an embodiment;

[0033] Figure 4 A schematic diagram of the internal structure designed according to the method of the present invention is shown in the embodiment;

[0034] Figure 5 The schematic diagram of the process of designing a pipeline structure according to the method of the present invention is an embodiment;

[0035] Figure 6 A schematic diagram of a self-forming rib structure designed according to the method of the present invention is shown in the embodiment;

[0036] Figure 7 A schematic diagram of the spacing dimensions of ribs designed according to the method of the present invention is shown in the embodiment;

[0037] Figure 8 The schematic diagram of the process of designing ribs according to the method of the present invention is an embodiment. DETAILED DESCRIPTION

[0038] 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.

[0039] The present invention discloses a method for additive manufacturing of a lightweight integrated multi-cavity structural component. Figure 1 As shown, the following steps are included:

[0040] Step 1: Design a self-forming structure for the partition structure between multiple cavities. The specific method is to design the partition structure between cavities that is suspended or has insufficient forming angle in the forming direction into a self-forming structure while maintaining its function of dividing the cavity area. The self-forming angle is determined according to the forming process and material selection. The self-forming structure includes but is not limited to: an inclined plate at a certain angle to the horizontal direction, a "pyramid" shaped plate, etc.

[0041] The forming processes include: powder bed sintering / melting additive manufacturing, direct deposition additive manufacturing, photo-curing additive manufacturing, etc.

[0042] The self-forming angle refers to the angle between the structure and the horizontal plane where the additive forming is located. For powder bed sintering processes, it is generally ≥30°; for powder bed melting processes, it is generally: aluminum alloy, titanium alloy ≥45°, high temperature alloy, alloy steel ≥55°; for direct deposition additive manufacturing processes, it is generally ≥45° for aluminum alloy, titanium alloy, high temperature alloy, alloy steel ≥45°; for photo-curing additive manufacturing, it is generally ≥30°.

[0043] Step 2: Design an integrated pipeline based on topological optimization. The original pipeline is usually laid in a fixed shape and direction according to its functionality. In accordance with the principle of self-forming additive manufacturing, a topological optimization design is performed to connect it to the surrounding structure with the least amount of material.

[0044] The topology optimization method is: connect the bottom surface of the pipeline forming direction with the surrounding structure of the product into a plate, set the design input as the plate that bears the structural warping stress and the connection surface with the surrounding structure as a fixed surface, the non-calculation threshold is the peripheral area of ​​the plate, the calculation threshold is the central area of ​​the plate, the topology algorithm is the maximum rigidity, the material reduction is (50~70)%, and the peripheral area of ​​the plate is the boundary of the plate offset inward by (1~5) mm.

[0045] Step 3: Design self-forming ribs. Self-forming ribs are designed according to the self-forming angle principle described in step 1. If hollow ribs are designed, it must be ensured that each independent cavity space has at least one hole / groove structure connected to the outside world, and the cross-sectional area of ​​the hole / groove structure is ≥3mm 2 .

[0046] Step 4: Design a self-forming rib or variable density dot matrix under the structure that still cannot self-form inside the cavity as its support structure, and retain it as a part of it after the structural parts are manufactured. The spacing between the self-forming rib or variable density dot matrix and the solid structure in contact with the supported surface is (1-6) mm. The outer contour of the self-forming rib is a triangle, the upper surface is in contact with the supported structure, and the distance from the edge of the structure is (1-5) mm; the side is in contact with the adjacent self-forming surface; the hypotenuse angle is designed according to the self-forming angle described in step 1. The rib is designed based on topological optimization to design a hollow structure. The topological optimization method is: set the design input as the upper surface of the triangular rib to bear the structural warping stress, the non-calculation threshold is the perimeter area of ​​the triangular plate, the calculation threshold is the central area of ​​the plate, the topology algorithm is the maximum rigidity, the material reduction is (50-70)%, and the perimeter area of ​​the plate is the boundary of the plate offset inward by (1-4) mm.

[0047] Step 5: Design at least one interconnected process hole structure at the lowest point in the forming direction of each cavity to interconnect the multi-cavity structures; design at least one process hole connected to the outside world at the lowest point in the forming direction of the interconnected multi-cavity structures to discharge the internal excess. Design at least one process hole structure connected to the outside world at the top surface in the forming direction of each cavity connected to the outside world to clean and inspect the excess.

[0048] The cross-sectional area of ​​the process hole connecting each cavity is ≥3mm 2 The cross-sectional area of ​​the process hole connecting the cavity to the outside world is ≥10mm 2 The shapes of the process holes include circular, semicircular, rectangular, etc.

[0049] The method of using the process hole structure to inspect the excess material situation includes endoscopic inspection, visual inspection, etc.

[0050] Step 6: Add necessary supports to the outside of the structural part according to the selected forming direction. The added supports cannot block the designed process hole structure connected to the outside world to complete the additive process model design.

[0051] Step 7: Complete the additive manufacturing process according to the additive manufacturing process selected in step 1.

[0052] Step 8: After the additive manufacturing is completed, the process hole structure designed in step 5 is used to thoroughly clean the residual powder, liquid and other excess materials inside. The cleaning methods include: high-pressure gas cleaning, high-pressure liquid flushing, liquid rinsing, etc. The high-pressure gas includes air and inert gas. The liquid includes water, anhydrous ethanol, acetone, gasoline, special cleaning agent, etc. During the cleaning process, X-ray, endoscopy and other means are used to check the excess materials in the inner cavity in real time until the excess materials are completely cleaned up.

[0053] Step 9: Complete subsequent drying, heat treatment, support removal, grinding, machining and other processes to achieve additive manufacturing of lightweight integrated multi-cavity structure.

[0054] Example:

[0055] like Figure 2 As shown in FIG. 1 , the embodiment is an open thin-walled cabin section, made of aluminum alloy, and formed in one piece by laser selective melting additive manufacturing. The end with a smaller cross section is selected as the bottom, and additive manufacturing is performed from the bottom to the top. The length in the additive forming direction is 600 mm, and the cross section in the forming direction is a rectangular cross section of 200×200 mm. The model designed according to the method of the present invention is shown in FIG. Figure 3 As shown, perform the following operations:

[0056] Step 1: Design a self-forming structure for the partition structure 1-1 lower horizontal plate, 1-2 upper horizontal plate, and 1-3 vertical plate between the multiple cavities, and select a self-forming angle of 45° according to the materials and process methods of aluminum alloy powder bed fusion process.

[0057] The lower horizontal plate of 1-1 is designed as a "pyramid" plate structure, and each surface has an angle of 45° with the horizontal plane, and the optimized lower horizontal plate of 2-1 is obtained. The upper horizontal plate of 1-2 is designed as two inclined plate structures, and each surface has an angle of 45° with the horizontal plane, and the optimized lower horizontal plate of 2-2 is obtained. The vertical plate of 1-3 meets the self-forming conditions, so the original structure is maintained unchanged, and the vertical plate of 2-3 is the same as the vertical plate of 1-3.

[0058] Step 2: Design the pipeline structure 1-4 into an integrated pipeline based on topology optimization. The specific method is as follows: Figure 4 As shown: the bottom surface of the pipeline forming direction is connected to the bottom structure into a plate, the outer diameter of the pipeline is 12mm, and the thickness of the connecting plate is 4mm; the design input is set to the plate to bear the warping force of the pipeline, the connecting surface with the bottom surface inside the cavity is a fixed constraint, the non-computational domain is the 3mm range of the perimeter of the connecting plate, the calculation threshold is the other central area of ​​the connecting plate, and the calculated material reduction is (50~70)%, and the topological optimization calculation threshold shape is obtained; according to the requirement of ≥45° self-forming angle, the calculation domain shape design is completed on the topological optimization shape to obtain the topologically optimized connecting plate, which is merged with the original model to obtain the optimized integrated 2-4 pipeline structure, which has a material reduction of 65% compared with before optimization.

[0059] Step 3: Design the middle 1-5 hollow ring ribs according to the self-forming angle of 45° to obtain the self-forming 2-5 self-forming hollow ring ribs. Figure 5 As shown in the figure, the lower part of the central ring rib is designed with a self-forming bevel structure, and a 1 / 4 circular section with a radius of 4mm is added to the four corners, and the cross-sectional area of ​​each hole is about 12.56mm 2 , there is enough powder leakage flux.

[0060] Step 4: Design a self-forming rib plate under the 1-6 top surface structure that still cannot self-form inside the cavity. The distance between the self-forming rib plate and the solid structure in contact with the supported surface is 6mm, that is, the distance between the rib plates is 6mm and the distance from the edge of the structure is 4mm. Figure 6 The topological optimization and weight reduction of the rib plate are carried out as follows: Figure 7 As shown, a triangular rib plate shape is taken, the 2mm range of the edge of the design structure is the reserved area, and the rest of the middle structure is the design domain. The upper surface of the triangular rib plate is set to bear the structural warping stress, the plane of the side contacting the inner wall of the cavity is a fixed constraint, the topology algorithm is the maximum rigidity, and the material reduction is 65%, so as to obtain a top surface structure with maximum weight reduction and 2-6 self-forming.

[0061] Step 5: If Figure 8 As shown, four 1 / 4 circular process holes are designed at the lowest point in each cavity forming direction, with a radius of 4mm and a cross-sectional area of ​​each hole of approximately 12.56mm 2 A process hole connected to the outside world is designed at the lowest point of the cavity in the forming direction. The shape is circular, the radius is 3mm, and the cross-sectional area is about 28.26mm. A process hole structure connected to the outside world is designed near the upper top surface in each cavity in the forming direction for cleaning and detection of excess materials. This process hole can be used to insert an endoscope to detect excess materials inside.

[0062] Step 6: Add necessary supports to the external suspended surface of the structural part according to the selected forming direction. The added supports avoid the process hole structure connected to the outside world, and the additive process model design is completed.

[0063] Step 7: Select the laser selective melting forming process, perform additive manufacturing according to the designed process model, and complete the additive manufacturing forming.

[0064] Step 8: After the additive manufacturing is completed, the process hole structure designed in step 5 is used to thoroughly clean the residual powder inside by high-pressure gas cleaning and high-pressure liquid flushing. Until there is no excess material found by X-ray, endoscope inspection and other means.

[0065] Step nine: completing subsequent drying, heat treatment, support removal, grinding, machining and other processes, thereby achieving additive manufacturing of the lightweight integrated multi-cavity structure of the embodiment.

[0066] The present invention proposes a method for additive manufacturing of a lightweight, one-piece multi-cavity structural part. First, a forming direction is selected, and a self-forming structure is designed for the partition structure between cavities in the process model design to achieve multi-cavity one-piece forming. Further taking into account the requirements of product integration and lightweight, an integrated pipeline based on topological optimization, self-forming ribs, and ribs or variable-density lattice structures for supporting internal suspended or non-self-forming surfaces are designed. In order to consider the cleaning and detection of excess materials, a process hole structure that is interconnected and connected to the outside world is designed at the lowest point in each cavity forming direction to complete the design of the additive process model for the lightweight, one-piece multi-cavity structure. After completing the additive manufacturing in the selected forming direction, the residual powder, liquid and other excess materials are completely removed with the help of the designed process holes, and finally the additive manufacturing of the lightweight, one-piece multi-cavity structure is achieved.

[0067] 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.

[0068] 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 lightweight integrated multi-cavity structural component additive manufacturing method, characterized in that: The steps include: Step 1: Design the inter-cavity partition structure that is suspended or has an insufficient forming angle in the forming direction into a self-forming structure while maintaining its function of dividing the cavity area to achieve multi-cavity integrated direct forming; Step 2: Design an integrated pipeline based on topology optimization, and connect it with the surrounding structure using the least material; the topology optimization method is: connect the bottom surface of the pipeline in the forming direction with the surrounding structure of the product to form a connecting plate, set the design input as the plate bearing structural warping stress, the connection surface with the surrounding structure as a fixed surface, the non-calculation threshold as the peripheral area of ​​the plate, the calculation threshold as the central area of ​​the plate, the topology algorithm as maximum rigidity, the material reduction as (50-70)%, and the peripheral area of ​​the plate as the boundary of the plate offset inward by (1-5) mm; Step 3: Design the self-forming ribs according to the self-forming angle of step 1; Step 4: Design a support structure under the structure that still cannot self-form inside the cavity, wherein the support structure is a self-forming rib plate or a variable density lattice, and the support structure is still retained after the structural component is manufactured; Step 5: at least one interconnected process hole structure is designed at the lowest point in the forming direction of each cavity to interconnect the multi-cavity structures; at least one process hole connected to the outside is designed at the lowest point in the forming direction of the interconnected multi-cavity structure to discharge the internal excess; at least one process hole structure connected to the outside is designed on the top surface in the forming direction of each cavity connected to the outside to clean and inspect the excess; Step 6: Add necessary supports to the outside of the structural part according to the selected forming direction. The added supports cannot cover the designed process hole structure connected to the outside world, and complete the additive process model design; Step 7: Complete the additive manufacturing process according to the additive manufacturing process selected in step 1; Step 8: After the additive manufacturing is completed, the process hole structure designed in step 5 is used to thoroughly clean the excess material remaining inside; Step 9: Complete the subsequent drying, heat treatment, support removal, grinding, and machining processes to achieve additive manufacturing of lightweight integrated multi-cavity structures.

2. The method for additive manufacturing of a lightweight integrated multi-cavity structural component according to claim 1, characterized in that: Structures that can self-form include, but are not limited to, inclined plates and "pyramid" shaped plates that are at a certain angle to the horizontal.

3. The method for additive manufacturing of a lightweight integrated multi-cavity structural component according to claim 1, characterized in that: In the step 2, the outer diameter of the integrated pipeline is R, and the thickness of the connecting plate is 1 / 3R~R.

4. The method for additive manufacturing of a lightweight integrated multi-cavity structural component according to claim 1, characterized in that: In the step three, if the self-forming rib is a hollow rib, it must be ensured that each independent cavity space has at least one hole / groove structure communicating with the outside.

5. The additive manufacturing method for a lightweight integrated multi-cavity structural component according to claim 1, characterized in that: In step three, the outer contour of the self-forming rib is a triangle, the upper surface contacts the supported structure and is (1 to 5) mm away from the edge of the structure; the side contacts the adjacent self-forming surface; and the bevel angle is designed according to the self-forming angle of step one.

6. The method for additive manufacturing of a lightweight integrated multi-cavity structural component according to claim 5, characterized in that: The self-forming rib plate is designed as a hollow structure based on topological optimization. The topological optimization method is: setting the design input as the upper surface of the triangular rib plate to bear the structural warping stress, the non-calculation threshold is the peripheral area of ​​the triangular plate, the calculation threshold is the central area of ​​the triangular plate, the topology algorithm is maximum rigidity, the material reduction is (50~70)%, and the peripheral area of ​​the plate is the boundary of the plate offset inward by (1~4) mm.

7. The additive manufacturing method for a lightweight integrated multi-cavity structural component according to claim 1, characterized in that: In step five, the shapes of the process holes include circular, semicircular, and rectangular.

8. The method for additive manufacturing of a lightweight integrated multi-cavity structural component according to claim 1, characterized in that: Methods for excess material inspection using process hole structures include but are not limited to endoscopic inspection and visual inspection.

9. The additive manufacturing method for a lightweight integrated multi-cavity structural component according to claim 1, characterized in that: In the step 1, the self-forming angle refers to the angle between the structure and the horizontal plane where the additive forming is performed.

10. The method for additive manufacturing of a lightweight integrated multi-cavity structural component according to claim 1, characterized in that: In the step eight, cleaning the residual waste inside includes: high-pressure gas cleaning, high-pressure liquid flushing, and liquid rinsing; during the cleaning process, the residual waste in the inner cavity is checked in real time by means of X-ray or endoscope inspection until the residual waste is completely cleaned; The gas includes air and inert gas; the liquid includes water, anhydrous ethanol, acetone, gasoline and special cleaning agent.

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