Elliptical thin-walled cabin section additive manufacturing profile accuracy control method

Abstract

This invention relates to a method for controlling the surface accuracy of elliptical thin-walled compartments in additive manufacturing, belonging to the field of additive manufacturing technology. Addressing the challenges of surface control in additive manufacturing and post-processing of elliptical thin-walled compartments, this invention proposes a surface accuracy control method based on an internally supported dimensional structure. This method includes steps such as additive manufacturing model design of the elliptical compartment and its internally supported dimensional structure, integrated additive design, thermal processing, machining, and removal of the internally supported dimensional structure. The method applies the control of the internally supported dimensional structure extension used in additive manufacturing to the post-processing stage, achieving full-process surface control from additive manufacturing to post-processing, saving product manufacturing time and improving the overall efficiency of additive manufacturing.

Description

Technical Field

[0001] This invention relates to the field of additive manufacturing technology for thin-walled compartments, and in particular to a method for controlling the surface accuracy of elliptical thin-walled compartments in additive manufacturing. Background Technology

[0002] With the development of high-end manufacturing, in fields such as aerospace and transportation, the structural forms of cabin components are constantly breaking through the limits of traditional manufacturing processes, continuously evolving towards irregular shapes and thin walls. Typically, cabin structures have a circular cross-section, with an overall three-dimensional cylindrical shape, exhibiting symmetry and uniformity, thus ensuring good structural stability and easy deformation control. However, with the evolution of component structures, the traditional circular cross-section has gradually evolved into an irregular elliptical cross-section, accompanied by thinner walls, more features, and higher requirements for surface precision. Compared to standard cylindrical cabin sections, these irregular elliptical cross-section cabin sections face challenges in additive manufacturing, including uneven internal stress distribution, greater deformation tendencies, and highly complex shape control.

[0003] For deformation control of additively manufactured compartment products, traditional methods mainly employ ribs and lattice shaping, pre-deformation, and thermal straightening to improve surface accuracy. Ribs and lattice shaping, and pre-deformation are effective for cylindrical compartments because their deformation trend is regular, exhibiting uniform radial shrinkage, thus providing a clear basis for application. However, for elliptical thin-walled compartments, with uneven internal stress distribution, large deformation, and low structural stability, large deformations will occur not only during additive manufacturing but also in subsequent heat treatment and support removal processes, leading to unpredictable deformations. Therefore, lattice shaping and pre-deformation are less effective. While thermal straightening can theoretically improve surface accuracy, it requires significant time and cost for the straightening tooling.

[0004] Therefore, for elliptical thin-walled compartments, it is necessary to develop a method that can effectively control surface accuracy during additive manufacturing and post-processing, thereby improving the overall additive manufacturing efficiency. Summary of the Invention

[0005] Based on the above analysis, the present invention aims to provide a method for controlling the surface accuracy of elliptical thin-walled compartments in additive manufacturing, in order to solve at least one of the following problems in existing additive manufacturing and post-processing of elliptical thin-walled compartments: difficulty in controlling deformation, poor surface accuracy, and low manufacturing efficiency.

[0006] This invention provides a method for controlling the surface accuracy of elliptical thin-walled compartments in additive manufacturing. The design method includes the following steps:

[0007] Step 1: Design the additive manufacturing model of the elliptical thin-walled section, and generate the body model of the elliptical thin-walled section and its internal support structure model. The internal support structure includes a mating structure that can be connected with subsequent heat treatment and machining tooling.

[0008] Step 2: Integrate the elliptical thin-walled section and its internal support dimensional structure model into an additive manufacturing process to obtain the overall component;

[0009] Step 3: Use fitting tooling that can be connected to the internal support structure to clamp the whole component, and perform integrated heat treatment on the whole component to eliminate residual stress inside the structure.

[0010] Step 4: Determine whether machining is required on the mating structure of the internal support structure. If so, use mating fixtures that can be connected to the mating structure of the internal support structure to clamp the overall component and machine the elliptical thin-walled section. If not, proceed to Step 5.

[0011] Step 5: Remove the internal support structure.

[0012] Preferably, step one includes:

[0013] An elliptical thin-walled section model was constructed based on simulation analysis software;

[0014] Two cylindrical internal support structures are set on both sides of the short axis centerline of the inner surface of the elliptical thin-walled section, and a rib is set between the two cylindrical internal support structures along the short axis direction.

[0015] The elliptical thin-walled cabin was simulated using simulation analysis software to obtain the model deformation results.

[0016] A thin-plate support is provided between the inner wall of the straight section of the elliptical thin-walled compartment and the cylindrical internal support structure or rib plate, passing through the center of the deformation curvature circle at the deformation point.

[0017] Preferably, in step two, the additive manufacturing energy density of the elliptical thin-walled compartment body model is set to 1.5 to 2 times that of the internally supported dimensional structure model.

[0018] Preferably, in step two, the elliptical thin-walled section is made of titanium alloy, and the laser power for the part body is set to 250-400W, the scanning speed is 950-1400mm / s, and the scanning border is scanned.

[0019] Preferably, in step two, the laser power for the inner support structure is set to 250-320W, the scanning speed is 1100-1600mm / s, and the border is not scanned;

[0020] The scanning spacing and powder thickness are the same for the main body of the part and the internal support structure.

[0021] Preferably, in step three, the heat treatment is annealing.

[0022] Preferably, in step three, the elliptical thin-walled compartment is made of titanium alloy, and the annealing treatment is vacuum annealing at a temperature of 600–800°C for 3–5 hours.

[0023] Preferably, in step three, the elliptical thin-walled section is made of aluminum alloy, and the annealing temperature is 200-300℃, with a holding time of 2-3 hours.

[0024] Preferably, in step three, the elliptical thin-walled section is made of a high-temperature alloy and is vacuum annealed at a temperature of 500–800°C for 3–5 hours.

[0025] Preferably, in step three, the elliptical thin-walled section is made of alloy steel, and the annealing temperature is 400-600℃, with a holding time of 3-5 hours.

[0026] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0027] 1. The method of the present invention utilizes the matching structure of the internal support shaped structure and the matching tooling of the post-processing to extend the control of the internal support shaped structure in the additive manufacturing process to the post-processing process, thereby realizing full-process shape control from additive manufacturing to post-processing and saving the overall manufacturing time of the product.

[0028] 2. This invention controls the degree of material melting and heat distribution by adjusting the volume energy density of the elliptical thin-walled compartment part body and the internal support dimensional structure. While ensuring that the material is fully melted, it maintains the stability of the internal support dimensional structure, thereby achieving surface accuracy control in the additive manufacturing process.

[0029] 3. This invention utilizes simulation analysis to simulate the thin plate support component, obtains the model deformation results, and adds the thin plate support component at the center of the deformation curvature circle at the deformation point, thus solving the problem of difficulty in determining the thin plate support component and easily realizing the determination and setting of the thin plate support component position.

[0030] 4. This invention eliminates residual stress generated during additive manufacturing by integrating the elliptical thin-walled compartment part body and the internal support structure with heat treatment, while simultaneously improving the material's toughness. During heat treatment, the internal support structure continues to function as an internal support, thereby achieving precise control of the surface shape during the heat treatment process.

[0031] 5. The mating structure and tooling used in the method of the present invention are simple in structure, which makes it convenient to assemble and clamp the whole component in the post-processing process. There is no need to design special fixtures, which saves time and cost in the manufacturing process and ensures the reliability of operation.

[0032] 6. This invention introduces an internally supported dimensional structure into the additive manufacturing model of an elliptical compartment. Through the model design of the internally supported dimensional structure, a cylindrical internally supported dimensional structure, ribs, and thin plate supports are used to internally support the elliptical compartment in layers, transforming the unstable elliptical cross-sectional structure into a stable approximately circular, triangular, or quadrilateral cross-sectional structure, thereby achieving effective control over the surface accuracy of the additive manufacturing of the elliptical thin-walled compartment structure.

[0033] 7. The present invention adopts a combination of cylindrical internal support structure, rib plate and thin plate support component. With a simple structure, it maximizes the expansion of the internal space of the internal support structure while ensuring the support strength, thereby improving the efficiency of the overall additive manufacturing process.

[0034] 8. This invention achieves easy removal of the internal support structure after additive manufacturing by thinning the part connecting the internal surface of the internal support structure and the elliptical thin-walled compartment; and saves the overall printing time of the model by setting a lower additive manufacturing volume energy density for the internal support structure model.

[0035] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0036] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0037] Figure 1 A flowchart of a method for controlling the surface accuracy of elliptical thin-walled compartments in additive manufacturing;

[0038] Figure 2a This is a schematic diagram of the elliptical thin-walled compartment body model;

[0039] Figure 2b This is a cross-sectional view of the AA section of the elliptical thin-walled compartment model.

[0040] Figure 3 This is a schematic diagram of the cross-section of the additive manufacturing support structure of the present invention;

[0041] Figure 4 This is a schematic diagram of the deformation of the straight section of the elliptical thin-walled compartment.

[0042] Figure 5 This is a schematic diagram of the cross-section of the elliptical thin-walled section and its supporting structure in Example 1;

[0043] Figure 6 This is a schematic diagram of the cross-section of the elliptical thin-walled section and its supporting structure before the simulation of Example 2;

[0044] Figure 7 This is a schematic diagram of the cross-section of the part and its support structure after the first addition of the thin plate support in Embodiment 2;

[0045] Figure 8 This is a schematic diagram of the cross-section of the part and its support structure after the second addition of the thin plate support in Embodiment 2;

[0046] Figure 9 This is a schematic diagram of the cross-section of the part and its supporting structure after the third addition of the thin plate support in Example 2;

[0047] Figure 10 This is a schematic diagram of the elliptical thin-walled compartment body in Embodiment 3;

[0048] Figure 11 This is a schematic diagram of the elliptical thin-walled section and its supporting structure in Example 3;

[0049] Figure 12 This is a schematic diagram of the thin-plate support and the component in Embodiment 3;

[0050] Figure 13 This is a diagram showing the deformation effect of a part manufactured using direct additive manufacturing in Example 3;

[0051] Figure 14 This is a diagram illustrating the deformation effect of the part after the support structure according to the present invention has been controlled in Example 3.

[0052] Figure 15 This is a schematic diagram of the internal support structure and fitting tooling in Example 3.

[0053] Figure label:

[0054] 1-Elliptical thin-walled section; 2-Cylindrical internal support structure; 3-Rib plate; 4-First thin-plate support; 5-Second thin-plate support; 6-Third thin-plate support; 7-Matching tooling. Detailed Implementation

[0055] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0056] A specific embodiment of the present invention discloses a method for controlling the surface accuracy of elliptical thin-walled compartments in additive manufacturing, such as... Figure 1 As shown, it includes the following steps:

[0057] Step 1: Design the additive manufacturing model of the elliptical thin-walled section, and generate the body model of the elliptical thin-walled section 1 and its internal support structure model. The internal support structure includes a mating structure that can be connected with subsequent heat treatment and machining tooling.

[0058] Step 2: Integral additive manufacturing of the elliptical thin-walled section 1 and its internal support dimensional structure model to obtain the overall component;

[0059] Step 3: Use fitting fixture 7, which can be connected to the internal support structure, to clamp the overall component and perform integrated heat treatment on the overall component to eliminate residual stress inside the structure. During integrated heat treatment, necessary heat treatment fixtures can be installed according to the workpiece surface accuracy control requirements and the heat treatment deformation characteristics of the parts to further control heat treatment deformation and improve product accuracy. The design of the heat treatment fixtures can be matched with the product's internal support structure, and installation can be carried out by taking advantage of the structural features of the internal support structure.

[0060] Step 4: Determine whether machining is required for the mating structure of the internal support structure. If so, use the mating fixture 7, which can be connected to the mating structure of the internal support structure, to clamp the overall component and machine the elliptical compartment. If not, proceed to Step 5.

[0061] Step 5: Remove the internal support structure;

[0062] like Figures 2a-2b As shown, the elliptical thin-walled section 1 has a flattened elliptical cross-section with a major axis and a minor axis, corresponding to a major axis centerline and a minor axis centerline. The middle section is a straight line segment, and the two sides are circular arc segments. For example, the ratio of the major axis diameter X to the minor axis diameter Y is greater than 1.2.

[0063] Compared to existing technologies, the method of this invention considers the tooling for post-processing during the additive manufacturing model design stage, and combines the tooling for controlling the internal support structure with the tooling for post-processing. This extends the use of the internal support structure in the additive manufacturing process to the post-processing process, achieving full-process shape control from additive manufacturing to post-processing, and saving the overall manufacturing time of the product.

[0064] In step one, the additive manufacturing model design method includes: designing an additive manufacturing model for an elliptical thin-walled section, generating a model of the elliptical thin-walled section 1 body and its internal support dimensional structure, including:

[0065] Model 1 of the elliptical thin-walled section was constructed based on simulation analysis software;

[0066] Two cylindrical internal support structures 2 are provided on both sides of the short axis centerline of the inner surface of the elliptical thin-walled section 1, and a rib plate 3 is provided between the two cylindrical internal support structures 2 along the short axis direction.

[0067] The elliptical thin-walled section 1 was simulated using simulation analysis software to obtain the model deformation results.

[0068] A thin-plate support is provided between the inner wall of the straight section of the elliptical thin-walled compartment 1 and the cylindrical inner support structure 2 or rib plate 3, passing through the center of the deformation curvature circle at the deformation point.

[0069] Specifically, the simulation analysis software can be commonly used simulation analysis software in existing technologies, such as Fluent from ANSYS and Fastran from CFX ESI.

[0070] In step one, an additive manufacturing model of the elliptical thin-walled section is designed, generating the main body model of the elliptical thin-walled section 1 and its internal support dimensional structure model, specifically including:

[0071] Step a. Construct a model of the elliptical thin-walled section 1;

[0072] Step b: Determine the center and outer radius of the cylindrical internal support structure 2 based on the major axis dimension and minimum machining spacing of the elliptical thin-walled section 1, and symmetrically set two cylindrical internal support structures 2 on both sides of the minor axis centerline of the inner surface of the elliptical thin-walled section 1.

[0073] Step c. Determine the location of the rib plate 3 based on the major axis dimension of the elliptical thin-walled section 1 and the outer diameter dimension of the cylindrical internal support structure, and set the rib plate 3 along the minor axis direction between the two cylindrical internal support structures 2;

[0074] Step d. Determine the setting direction of the first thin plate support 4 according to the center position of the cylindrical internal support structure 2. The first thin plate support 4 is connected to the outer surface of the cylindrical internal support structure 2 at one end and to the nearest rib 3 at the other end.

[0075] Step e. Determine the setting direction of the second thin plate support 5 according to the center position of the arc segment of the elliptical thin-walled compartment 1. The second thin plate support is connected to the inner wall of the arc segment of the elliptical thin-walled compartment 1 at one end and to the outer surface of the cylindrical inner support structure 2 at the other end. The setting direction of the second thin plate support 5 points to the center of the arc segment of the elliptical thin-walled compartment 1.

[0076] Step f. Perform additive manufacturing simulation on the elliptical thin-walled section 1 model equipped with ribs 3, cylindrical internal support structure 2, first thin plate support 4, and second thin plate support 5 to obtain the model deformation results;

[0077] Step g. Determine whether a thin-plate support needs to be added based on the deformation results. If the model deformation results do not meet the target deformation requirements, then a thin-plate support is added; if the model deformation results meet the target deformation requirements, then it is determined to be an elliptical thin-walled compartment additive manufacturing model.

[0078] Step h. Repeat steps f and g until the deformation of the simulated model meets the target deformation requirements.

[0079] The elliptical thin-walled module body and its internal support dimensional structure model obtained using the above design method are as follows: Figure 3 As shown in the cross-sectional view, the internal support structure of the elliptical thin-walled section 1 includes a support body and support components;

[0080] Among them, the support body consists of two cylindrical internal support structures 2 symmetrically arranged on both sides of the center line of the short axis of the inner surface of the elliptical thin-walled section 1;

[0081] Among them, the support includes a rib plate 3 located between the two cylindrical inner support structures 2 and arranged along the short axis direction. The rib plate 3 is parallel to the short axis direction and penetrates the interior of the elliptical thin-walled section 1. Its two ends are respectively connected to the inner side of the straight section sidewall on both sides of the short axis direction of the elliptical thin-walled section 1, and support the inner surface of the elliptical thin-walled section 1 along the short axis direction.

[0082] The support components also include a first thin plate support component 4, a second thin plate support component 5, and a third thin plate support component 6. The thin plate support components 4, 5, and 6 are disposed in the area between the inner surface of the elliptical thin-walled section 1, the support body, and the rib plate 3. The support body and the support components divide the elliptical cross-sectional structure into circular, triangular, and / or quadrilateral cross-sectional structures.

[0083] like Figure 15 As shown, the mating structure in the internal support structure that connects with the subsequent heat treatment and machining fixtures is the cylindrical internal support structure 2. The mating fixture 7 is a cover plate with a protrusion. The protrusion can be embedded into the cylindrical body of the internal support structure and mat with the inner surface of the cylindrical body.

[0084] This invention utilizes the mating structure of the internally supported shaped structure and the mating tooling for post-processing, extending the control of the internally supported shaped structure used in additive manufacturing to the post-processing stage. This achieves full-process shape control from additive manufacturing to post-processing, saving overall product manufacturing time. In the support structure of this invention, through the internally supported structure design of the support members and the support body, the elliptical thin-walled compartment section is internally supported and shaped in layers, transforming the unstable elliptical cross-sectional structure into a stable cross-sectional structure such as an approximate circle, triangle, or quadrilateral. This achieves effective control over the shape accuracy of the elliptical thin-walled compartment structure in additive manufacturing.

[0085] For example, in step b of step one, the centers of the two cylindrical internal support structures 2 are respectively set at two eccentric points on the major axis diameter of the inner surface of the elliptical thin-walled compartment, and the outer surface of the cylindrical internal support structure 2 does not directly contact the inner surface of the elliptical thin-walled compartment.

[0086] For example, in step b of step one, the outer surface of the cylindrical internal support structure 2 is set to be as close as possible to the inner surface of the elliptical thin-walled section 1, and the outer radius of the cylindrical internal support structure 2 is set as the shortest distance between the center of the cylindrical internal support structure 2 and the inner surface of the elliptical thin-walled section 1 minus the minimum processing spacing. The minimum processing spacing is the distance between the outer surface of the cylindrical internal support structure 2 and the inner surface of the cylindrical section where they are closest, and is set according to the processing requirements of removing the internal support structure after additive manufacturing. The value of the minimum processing spacing is 5 to 50 mm.

[0087] Specifically, when half of the major axis diameter of the inner surface of the elliptical thin-walled compartment 1 is greater than the minor axis diameter, the shortest distance between the center of the cylindrical internal support structure 2 and the inner surface of the elliptical thin-walled compartment 1 is in the minor axis direction, and the closest point is on the straight section wall. The outer radius of the cylindrical internal support structure 2 is set to half of the minor axis diameter minus the minimum machining spacing. When half of the major axis diameter of the inner surface of the elliptical thin-walled compartment 1 is less than the minor axis diameter, the shortest distance between the center of the cylindrical internal support structure 2 and the inner surface of the elliptical thin-walled compartment 1 is in the major axis direction, and the closest point is on the arc section wall. The outer radius of the cylindrical internal support structure 2 is set to one-quarter of the major axis diameter minus the minimum machining spacing.

[0088] For example, in step b of step one, the cylindrical internal support structure 2 is set as a multi-layer cylindrical structure. The multi-layer cylindrical structures can be connected by means of lattice, truss, thin plate, etc. The multi-layer cylindrical structures form a support structure with triangular or quadrilateral cross sections. The total thickness of the cylindrical internal support structure 2 is 1 to 3 times the minimum wall thickness of the elliptical thin-walled section 1.

[0089] For example, in step c of step one, the rib 3 is set as one, arranged along the center line of the short axis, the thickness of the rib 3 is 1 to 3 times the minimum wall thickness of the elliptical thin-walled section 1, and the closest distance to the cylindrical inner support structure 2 on both sides of the center line of the short axis is set as the minimum processing spacing.

[0090] For example, in step c of step one, multiple ribs 3 are provided, and the thickness of each rib 3 is 1 to 3 times the minimum wall thickness of the elliptical thin-walled section 1. The closest distance to the cylindrical inner support structure 2 on both sides of the short axis centerline is set as the minimum processing spacing, and the spacing between the multiple ribs 3 is the minimum processing spacing.

[0091] Specifically, when half of the major axis diameter of the inner surface of the elliptical thin-walled section 1 is greater than the minor axis diameter, the distance between the two cylindrical internal support structures 2 is relatively large, and multiple ribs 3 are used for support. The rib 3 located adjacent to the cylindrical internal support structure 2 is closest to the arc vertex of the cylindrical internal support structure 2, and this distance is set as the minimum processing spacing. When half of the major axis diameter of the inner surface of the elliptical thin-walled section 1 is less than the minor axis diameter, the distance between the two cylindrical internal support structures 2 is relatively small, and one rib 3 is used for support. In this case, the distance between the rib 3 and the arc vertex of the two cylindrical internal support structures 2 is set as the minimum processing spacing.

[0092] For example, in step c of step one, the rib plate 3 is set as a multi-layer plate, and the multi-layer plates can be connected by means of lattice, truss, thin plate, etc., forming a support structure with triangular or quadrilateral cross sections between the multi-layer plates.

[0093] For example, in step d of step one, the first thin plate support 4 is positioned in the direction of the center of the cylindrical inner support structure; the thickness of the first thin plate support 4 is set to 1 to 3 times the minimum wall thickness of the elliptical thin-walled section 1.

[0094] Specifically, such as Figure 3 As shown, the first thin plate support member 4 located between the cylindrical inner support structure 2 and the rib plate 3 is symmetrically arranged about the short axis, with 5 on each side, for a total of 10. Among them, the 5 first thin plate support members 4 located on the same side of the short axis are symmetrically arranged about the long axis. Specifically, each of them has one end connected to the outer surface of the cylindrical inner support structure 2 and the other end connected to the rib plate 3.

[0095] Specifically, such as Figure 5 As shown, the first thin plate support member 4 located between the cylindrical inner support structure 2 and the rib plate 3 is symmetrically arranged about the short axis, with 3 on each side, for a total of 6. Among them, the 3 first thin plate support members 4 located on the same side of the short axis are symmetrically arranged about the long axis. Specifically, each of them has one end connected to the outer surface of the cylindrical inner support structure 2 and the other end connected to the rib plate 3.

[0096] For example, in step e of step one, the setting direction of the second thin plate support 5 is directed towards the center of the arc segment of the elliptical thin-walled compartment 1; the thickness of the second thin plate support 5 is set to 1 to 3 times the minimum wall thickness of the elliptical thin-walled compartment.

[0097] Specifically, such as Figure 3 As shown, the second thin plate support 5 located in the arc segment of the elliptical thin-walled compartment 1 is symmetrically arranged about the short axis, with 16 on each side. Two of them are located at the intersection of the arc segment and the straight segment. All of them are configured to have one end connected to the inner wall of the arc segment of the elliptical thin-walled compartment 1, and the other end connected to the outer surface of the cylindrical inner support structure 2, pointing towards the center of the arc segment of the elliptical thin-walled compartment 1.

[0098] Specifically, such as Figure 5 As shown, the second thin plate support 5 located in the arc segment of the elliptical thin-walled compartment 1 is symmetrically arranged about the short axis, with 13 on each side. Two of them are located at the intersection of the arc segment and the straight segment. All of them are configured to have one end connected to the inner wall of the arc segment of the elliptical thin-walled compartment 1, and the other end connected to the outer surface of the cylindrical inner support structure 2, pointing towards the center of the arc segment of the elliptical thin-walled compartment 1.

[0099] For example, in step g of step one, the direction of setting the added thin plate support is determined according to the deformation curvature of the straight section of the elliptical thin-walled compartment when it is unsupported; the added thin plate support is the third thin plate support 6, one end of the third thin plate support 6 is connected to the inner wall of the straight section of the elliptical thin-walled compartment, the connection point is the place where the deformation curvature is the maximum when the straight section is unsupported, the third thin plate support 6 passes through the center of the circle of deformation curvature when it is unsupported at the connection point, and the other end is connected to the cylindrical inner support structure, rib plate or the first thin plate support 4.

[0100] Specifically, such as Figure 4 As shown in the figure, the dashed line portion represents the simulated deformation of the straight segment of the elliptical thin-walled section 1. The location where the third thin-plate support 6 is added is the point where the curvature of the straight segment of the elliptical thin-walled section 1 is at its maximum. The direction in which the third thin-plate support 6 is added is the center of the circle of curvature at that point. It should be noted that the deformation direction of the straight segment of the elliptical thin-walled section 1 is not necessarily perpendicular to the straight segment.

[0101] Specifically, such as Figure 3 As shown, the third thin-plate support 6 located on the straight section of the elliptical thin-walled compartment 1 is symmetrical about the minor axis, with 10 on each side. Among them, 8 on each side are configured to connect one end to the inner wall of the straight section of the elliptical thin-walled compartment 1 and the other end to the outer surface of the cylindrical inner support structure 2, with the direction passing through the center of the circle of curvature of deformation when there is no support at the connection point with the elliptical thin-walled compartment 1; and 2 on each side are configured to connect one end to the inner wall of the straight section of the elliptical thin-walled compartment 1 and the other end to the rib plate 3, with the direction passing through the center of the circle of curvature of deformation when there is no support at the connection point with the elliptical thin-walled compartment 1.

[0102] Specifically, such as Figure 9 As shown, the third thin plate support 6 located on the straight section of the elliptical thin-walled compartment 1 is symmetrically arranged about the short axis, with 6 on each side. It is configured such that one end is connected to the inner wall of the straight section of the elliptical thin-walled compartment 1, and the other end is connected to the outer surface of the cylindrical inner support structure 2. The direction passes through the center of the circle of curvature of the deformation when there is no support at the connection point with the elliptical thin-walled compartment 1.

[0103] For example, the second thin plate support 5 and the third thin plate support 6 are thinned near the part that connects with the inner surface of the elliptical thin-walled compartment 1, and the thinning thickness is 0.5 to 1 times the minimum wall thickness of the compartment.

[0104] For example, in step two, the additive manufacturing material in this invention is a titanium alloy, aluminum alloy, high-temperature alloy, or alloy steel.

[0105] For example, in step two, the additive manufacturing parameters of general parts with high fusion strength are set for the elliptical thin-walled compartment 1 body, and the solid support parameters with low fusion strength are set for the inner support dimensional structure. Specifically, the additive manufacturing body energy density of the elliptical thin-walled compartment 1 body model is set to 1.5 to 2 times that of the inner support dimensional structure model.

[0106] Volume energy density can be calculated using the following formula:

[0107] E = P / (vht)

[0108] E is the volume energy density (J / mm²). 3 P is the laser power (W), v is the scanning speed (mm / s), h is the scanning spacing (mm), and t is the powder thickness of each layer (mm). In this invention, these values ​​are set to constants for the same product and the same material.

[0109] For example, for titanium alloys, the laser power is set to 250-400W and the scanning speed is 950-1400mm / s for the part body, and the border is scanned; the laser power is set to 250-320W and the scanning speed is 1100-1600mm / s for the inner support structure, and the border is not scanned; the scanning spacing and powder thickness are the same for the part body and the inner support structure.

[0110] For example, for aluminum alloys, the laser power is set to 300-400W and the scanning speed is 850-1200mm / s for the part body, and the border is scanned; the laser power is set to 200-300W and the scanning speed is 1100-1500mm / s for the inner support structure, and the border is not scanned; the scanning spacing and powder thickness are the same for the part body and the inner support structure.

[0111] For example, for high-temperature alloys, the laser power is set to 230-320W and the scanning speed is 700-1000mm / s for the part body, and the border is scanned; the laser power is set to 200-300W and the scanning speed is 800-1200mm / s for the inner support structure, and the border is not scanned; the scanning spacing and powder thickness are the same for the part body and the inner support structure.

[0112] This invention further controls surface accuracy by adjusting the volume energy density of the elliptical thin-walled section component and its internal supporting dimensional structure. Increasing the volume energy density of the component body—that is, setting the laser power, scanning speed, and scanning border—helps to melt the material more fully, improving surface accuracy. Simultaneously, reducing the volume energy density of the internal supporting dimensional structure—that is, reducing the laser power and scanning speed, and omitting the scanning border—limits the melting of the internal supporting dimensional structure, reducing its impact on the component's shape.

[0113] In terms of material melting control, volume energy density also affects the melting process. Increasing the volume energy density of the part body ensures sufficient melting, thereby reducing solidification shrinkage and deformation. Reducing the volume energy density of internal support structures helps maintain their shape stability and avoids unnecessary melting and deformation. Adjusting the volume energy density can also affect heat distribution.

[0114] In terms of heat distribution control, setting a high volume energy density for the main body of the component makes the heat more concentrated in these areas, which helps to better control the shape of the component. Setting a low volume energy density for the internal support structure helps to maintain the stability of the internal support structure and prevents excessive heat transfer to these areas.

[0115] In addition, the volume energy density setting of this invention varies for different materials. The volume energy density is adjusted according to the type of material used to meet the melting and forming requirements of specific materials, thereby achieving better control of surface accuracy.

[0116] For example, in step three, the heat treatment is annealing; specifically, for titanium alloys, vacuum annealing is used at a temperature of 600–800°C for 3–5 hours; for aluminum alloys, the annealing temperature is 200–300°C for 2–3 hours; for high-temperature alloys, vacuum annealing is used at a temperature of 500–800°C for 3–5 hours; and for alloy steels, the annealing temperature is 400–600°C for 3–5 hours.

[0117] During additive manufacturing, rapid cooling and solidification can lead to residual stress within the material. The annealing process of this invention helps eliminate these residual stresses, thereby reducing the risk of surface deformation and material instability. Simultaneously, annealing improves the material's toughness, making it more machinable. Materials with better toughness are easier to cut and machine, helping to maintain surface accuracy. Furthermore, for different materials, annealing temperatures and times tailored to their characteristics can be set for targeted annealing to achieve optimal shape retention.

[0118] For example, in step four, it is determined whether the part body is easy to hold or whether there is a clear reference, and whether the internal support structure is needed for machining. In the embodiment of the present invention, if the elliptical thin-walled compartment 1 does not have a good plane or cylindrical surface for machining and clamping, it is suitable to use the internal support structure to clamp it with its two obvious cylindrical surfaces to achieve stable machining clamping.

[0119] For example, in step four, the fitting tool is a cover plate with two cylindrical protrusions. The outer diameter of the protrusions is the same as the inner diameter of the cylindrical inner support structure 2. The protrusions can be engaged with the cylindrical inner support structure 2.

[0120] For example, in step four, the assembly tolerance of the inner support structure and the mating tooling generally meets the clearance fit requirements of H7 / g6 or H7 / h6;

[0121] For example, in step five, one or a combination of wire cutting, machining (turning, planing, milling, etc.), bench work, and grinding are used to remove the inner supporting structure; for example, wire cutting is used to remove the overall inner supporting structure along the inner contour of the elliptical thin-walled section 1; for example, firstly, wire cutting or machining is used to remove the middle overall structure of the inner supporting structure, leaving only the peripheral thin plate structure, and then the remaining part is removed by bench work using tools such as chisels, air chisels, and air grinders.

[0122] This invention introduces an internally supported dimensional structure into the additive manufacturing model of an elliptical compartment. Through the model design of the internally supported dimensional structure, a cylindrical internally supported dimensional structure, ribs, and thin-plate supports are used to internally support the elliptical compartment in layers, transforming the unstable elliptical cross-sectional structure into a stable approximately circular, triangular, or quadrilateral cross-sectional structure, thereby achieving effective control over the surface accuracy of the additive manufacturing of the elliptical thin-walled compartment structure.

[0123] Meanwhile, the present invention adopts a combination of cylindrical internal support structure, rib plate and thin plate support component. With a simple structure, it maximizes the expansion of the internal space of the internal support structure while ensuring the support strength, thereby improving the efficiency of the overall additive manufacturing process.

[0124] The surface accuracy of the elliptical thin-walled cabin structure additively manufactured according to the present invention can be controlled within ±0.67mm.

[0125] Example 1

[0126] This embodiment provides a method for controlling the surface accuracy of an elliptical thin-walled section 1 in additive manufacturing.

[0127] The target part for additive manufacturing is an elliptical thin-walled compartment 1 with a major axis diameter of 240 mm, a minor axis diameter of 200 mm, a minimum wall thickness of 2.5 mm, and an aluminum alloy material. The design documents specify that the deformation for additive manufacturing should be less than ±0.8 mm.

[0128] The additive manufacturing surface accuracy control method specifically includes the following steps:

[0129] Step 1: Design the additive manufacturing model of the elliptical thin-walled section, and generate the body model of the elliptical thin-walled section 1 and its internal support structure model. The internal support structure includes a mating structure that can be connected with the subsequent machining tooling.

[0130] Step 2: Integral additive manufacturing of the elliptical thin-walled section 1 and its internal support dimensional structure model to obtain the overall component;

[0131] Step 3: Use the fitting tool 7, which can be connected to the internal support structure, to clamp the whole component and perform integrated heat treatment on the whole component to eliminate residual stress inside the structure.

[0132] Step 4: Determine whether machining is required for the mating structure of the internal support structure. If so, use the mating fixture 7, which can be connected to the mating structure of the internal support structure, to clamp the overall component and machine the elliptical compartment. If not, proceed to Step 5.

[0133] Step 5: Remove the internal support structure.

[0134] In step one, an additive manufacturing model of the elliptical thin-walled section is designed, generating the main body model of the elliptical thin-walled section 1 and its internal support dimensional structure model, specifically including:

[0135] Step a. Construct the model of the elliptical thin-walled section 1.

[0136] Step b. Determine the center and outer radius of the cylindrical internal support structure 2 based on the major axis dimension and minimum machining spacing of the elliptical thin-walled section 1, and symmetrically set two cylindrical internal support structures 2 on both sides of the minor axis centerline of the inner surface of the elliptical thin-walled section 1.

[0137] Specifically, cylindrical internal support structures 2 are symmetrically arranged on both sides of the center line of the minor axis of the inner surface of the elliptical thin-walled section 1. The centers of the two cylindrical internal support structures 2 are respectively set at the points that are eccentrically divided into four parts (cross-shaped points in the figure) on the major axis diameter of the inner surface of the elliptical thin-walled section 1. The outer radius of the cylindrical internal support structure 2 is set as 1 / 4 of the major axis diameter of the elliptical thin-walled section 1 minus the minimum machining spacing of 15mm, which equals 45mm. The cylindrical internal support structure 2 is a concentric double-layer cylindrical structure, with each layer of cylinder having a thickness of 1.5mm and a distance of 2mm between the two layers of cylinders. The total thickness of the cylindrical internal support structure 2 is 5mm, and the two layers of cylinders are connected by thin plates.

[0138] Step c. Determine the location of the rib plate 3 based on the major axis dimension of the elliptical thin-walled section 1 and the outer diameter dimension of the cylindrical internal support structure, and set the rib plate 3 along the minor axis direction between the two cylindrical internal support structures 2;

[0139] Specifically, a rib 3 is set between the two cylindrical internal support structures 2. The rib 3 is set perpendicular to the cross section along the short axis direction. The rib 3 penetrates the interior of the elliptical thin-walled section 1, and its two ends are respectively connected to the inner side of the straight section sidewall on both sides of the short axis direction of the elliptical thin-walled section 1. The rib 3 is composed of parallel double-layer plates, each plate is 1.5mm thick, the distance between the double-layer plates is 3mm, and the total thickness of the rib 3 is 6mm. The double-layer plates are connected by a dot matrix. The shortest distance between the rib 3 and the outer surface of the two cylindrical internal support structures 2 is 12mm.

[0140] Step d. Determine the setting direction of the first thin plate support 4 according to the center position of the cylindrical internal support structure 2. The first thin plate support 4 is connected to the outer surface of the cylindrical internal support structure 2 at one end and to the nearest rib 3 at the other end.

[0141] Specifically, the thickness of the first thin plate support 4 is 3mm. The first thin plate support 4 is symmetrically arranged about the short axis, with 3 on each side, for a total of 6. Among them, the 3 first thin plate support 4 located on the same side of the short axis are symmetrically arranged about the long axis. Specifically, each of them has one end connected to the outer surface of the cylindrical inner support structure 2 and the other end connected to the rib plate 3, pointing towards the center of the cylindrical inner support structure 2.

[0142] Step e. Determine the setting direction of the second thin plate support 5 according to the center position of the arc segment of the elliptical thin-walled compartment 1. The second thin plate support 5 is connected to the inner wall of the arc segment of the elliptical thin-walled compartment 1 at one end and to the outer surface of the cylindrical inner support structure 2 at the other end.

[0143] Specifically, the thickness of the second thin plate support 5 is 3mm. The second thin plate support 5 is symmetrically arranged about the short axis, with 13 on each side. Two of them are located at the intersection of the arc segment and the straight segment. All of them are configured to connect one end to the inner wall of the arc segment of the elliptical thin-walled compartment 1 and the other end to the outer surface of the cylindrical inner support structure 2, pointing towards the center of the arc segment of the elliptical thin-walled compartment 1 (X-shaped point in the figure).

[0144] like Figure 5 The schematic diagram of the cross-section of the part body and its supporting structure shown shows that the inner support structure of the elliptical thin-walled section 1 is composed of the cylindrical inner support structure 2, the rib plate 3, the first thin plate support member 4 and the second thin plate support member 5, which divides the elliptical cross-section structure into circular, triangular or quadrilateral cross-section structures.

[0145] Step f. Perform additive manufacturing simulation on the elliptical thin-walled section 1 model, which is equipped with ribs 3, cylindrical internal support structure 2, first thin plate support 4, and second thin plate support 5, and obtain the model deformation results.

[0146] Step g. Determine whether a thin-plate support needs to be added based on the deformation results; the simulation deformation results show that the maximum deformation of the elliptical thin-walled section 1 model is -0.7mm, which meets the technical requirement of ±0.8mm and the target deformation requirement in the design document, and is determined to be the additive manufacturing model of the elliptical thin-walled section.

[0147] In step two, the additive manufacturing parameters for the elliptical thin-walled section 1 body, which has high fusion strength, are set as follows: laser power is 400W, scanning speed is 900mm / s, and the border is scanned. For the inner support structure, the solid support parameters, which have lower fusion strength, are set: laser power is 280W, scanning speed is 1100mm / s, and the border is not scanned. The scanning spacing and powder thickness are the same for both the body and the inner support structure. The additive manufacturing volume energy density of the elliptical thin-walled section 1 body model is set to 1.746 times that of the inner support structure model.

[0148] In step three, the heat treatment is annealing. In this embodiment, the annealing temperature is 270°C and the holding time is 3 hours.

[0149] In step four, the elliptical thin-walled compartment 1 part in this embodiment only needs to have its outer surface polished, and it is determined that it does not require machining of the internal support structure.

[0150] In step five, wire cutting is used to remove the overall internal support structure along the inner contour of the elliptical thin-walled section 1.

[0151] Measurements show that the maximum deformation of the elliptical thin-walled section 1 manufactured in this embodiment is 0.62 mm, which meets the target deformation requirements in the design documents.

[0152] Example 2

[0153] This embodiment provides a method for controlling the surface accuracy of an elliptical thin-walled section 1 in additive manufacturing.

[0154] The target part for additive manufacturing is an elliptical thin-walled compartment 1 with a major axis diameter of 500 mm, a minor axis diameter of 200 mm, a minimum wall thickness of 3.5 mm, and a nickel-based high-temperature alloy material. The design documents specify that the deformation for additive manufacturing should be less than ±0.8 mm.

[0155] The additive manufacturing surface accuracy control method specifically includes the following steps:

[0156] Step 1: Design the additive manufacturing model of the elliptical thin-walled section, and generate the body model of the elliptical thin-walled section 1 and its internal support structure model. The internal support structure includes a mating structure that can be connected with subsequent heat treatment and machining tooling.

[0157] Step 2: Integral additive manufacturing of the elliptical thin-walled section 1 and its internal support dimensional structure model to obtain the overall component;

[0158] Step 3: Use the fitting tool 7, which can be connected to the internal support structure, to clamp the whole component and perform integrated heat treatment on the whole component to eliminate residual stress inside the structure.

[0159] Step 4: Determine whether machining is required for the mating structure of the internal support structure. If so, use the mating fixture 7, which can be connected to the mating structure of the internal support structure, to clamp the overall component and machine the elliptical compartment. If not, proceed to Step 5.

[0160] Step 5: Remove the internal support structure.

[0161] In step one, an additive manufacturing model of the elliptical thin-walled section is designed, generating the main body model of the elliptical thin-walled section 1 and its internal support dimensional structure model, specifically including:

[0162] Step a. Construct the model of the elliptical thin-walled section 1.

[0163] Step b: Determine the center and outer radius of the cylindrical internal support structure 2 based on the major axis dimension and minimum machining spacing of the elliptical thin-walled section 1, and symmetrically set two cylindrical internal support structures 2 on both sides of the minor axis centerline of the inner surface of the elliptical thin-walled section 1.

[0164] Specifically, cylindrical internal support structures 2 are symmetrically arranged on both sides of the center line of the minor axis of the inner surface of the elliptical thin-walled section 1. The centers of the two cylindrical internal support structures 2 are respectively set at the points that are off-center from the major axis diameter of the inner surface of the elliptical thin-walled section 1 (cross-shaped points in the figure). The outer radius of the cylindrical internal support structure 2 is set as 1 / 2 of the minor axis diameter of the elliptical thin-walled section 1 minus the minimum processing distance of 45mm, which equals 55mm. The cylindrical internal support structure 2 is a concentric double-layer cylindrical structure. The thickness of each layer of the cylinder is 2mm, the distance between the two layers of cylinders is 1mm, and the total thickness of the cylindrical internal support structure 2 is 5mm. The two layers of cylinders are connected by a truss.

[0165] Step c. Determine the location of the rib plate 3 based on the major axis dimension of the elliptical thin-walled section 1 and the outer diameter dimension of the cylindrical internal support structure, and set the rib plate 3 along the minor axis direction between the two cylindrical internal support structures 2;

[0166] Specifically, three ribs 3 are arranged between the two cylindrical internal support structures 2. The ribs 3 are arranged perpendicular to the cross-section along the minor axis. The ribs 3 penetrate the interior of the elliptical thin-walled section 1, and their two ends are connected to the inner sidewalls of the straight sections on both sides of the minor axis of the elliptical thin-walled section 1. Each rib 3 consists of parallel double-layer plates, each layer of which is 2mm thick. The distance between the double-layer plates is 4mm, and the total thickness of each rib 3 is 8mm. The double-layer plates are connected by trusses. The spacing between each rib 3 is 18mm. The shortest distance between the rib 3 on the same side and the outer surface of the cylindrical internal support structure 2 is 35mm.

[0167] Step d. Determine the setting direction of the first thin plate support 4 according to the center position of the cylindrical internal support structure 2. The first thin plate support 4 is connected to the outer surface of the cylindrical internal support structure 2 at one end and to the nearest rib 3 at the other end.

[0168] Specifically, the thickness of the first thin plate support 4 is 4mm. The first thin plate support 4 is symmetrically arranged about the short axis, with 5 on each side, for a total of 10. Among them, the 5 first thin plate support 4 located on the same side of the short axis are symmetrically arranged about the long axis. Specifically, each of them has one end connected to the outer surface of the cylindrical inner support structure 2 and the other end connected to the rib plate 3, pointing towards the center of the cylindrical inner support structure 2.

[0169] Step e. Determine the setting direction of the second thin plate support 5 according to the center position of the arc segment of the elliptical thin-walled compartment 1. The second thin plate support 5 is connected to the inner wall of the arc segment of the elliptical thin-walled compartment 1 at one end and to the outer surface of the cylindrical inner support structure 2 at the other end.

[0170] Specifically, the thickness of the second thin plate support 5 is 4mm. The second thin plate support 5 is symmetrically arranged about the short axis, with 11 on each side. Two of them are located at the intersection of the arc segment and the straight segment. All of them are configured to connect one end to the inner wall of the arc segment of the elliptical thin-walled compartment 1 and the other end to the outer surface of the cylindrical inner support structure 2, pointing towards the center of the arc segment of the elliptical thin-walled compartment 1 (X-shaped point in the figure).

[0171] like Figure 6 As shown in the schematic diagram of the cross-section of the part body and its supporting structure, the inner support structure 2, the rib plate 3, the first thin plate support member 4 and the second thin plate support member 5 constitute the inner support structure of the elliptical thin-walled section 1, which divides the elliptical cross-section structure into circular, triangular or quadrilateral cross-section structures.

[0172] Step f-1. Perform additive manufacturing simulation on the elliptical thin-walled section 1 model, which is equipped with ribs 3, cylindrical internal support structure 2, first thin plate support 4, and second thin plate support 5, and obtain the model deformation results.

[0173] Step g-1. Determine whether it is necessary to add thin-plate support components based on the deformation results; the simulation deformation results show that the maximum deformation of the thin-walled section 1 model is 2.1mm, which exceeds the technical requirement of ±0.8mm and does not meet the target deformation requirements in the design documents;

[0174] A third thin plate support 6 with a thickness of 4mm is added to the straight section of the elliptical thin-walled compartment 1. Two of them are symmetrically arranged about the short axis. The two third thin plate supports 6 located on the same side of the short axis are symmetrically arranged about the long axis. All of them are configured to connect one end to the inner wall of the straight section of the elliptical thin-walled compartment 1. The connection point is the point where the deformation curvature is the maximum when the straight section is unsupported. This point is located near the middle of the straight section. The direction is through the center of the circle of deformation curvature when the unsupported section is unsupported at the connection point. The other end is connected to the inner support structure 2 of the cylinder.

[0175] like Figure 7 The diagram shown is a cross-sectional view of the part and its supporting structure after the addition of the third thin plate support member 6 for the first time.

[0176] Step f-2. Perform additive manufacturing simulation on the elliptical thin-walled section 1 model, which is equipped with ribs 3, cylindrical internal support structure 2, first thin plate support 4, second thin plate support 5, and third thin plate support 6, and obtain the model deformation results.

[0177] Step g-2. Determine whether thin-plate support components are needed based on the deformation results; the simulation deformation results show that the maximum deformation of the elliptical thin-walled section 1 model is 1.5mm, which exceeds the technical requirement of ±0.8mm and does not meet the target deformation requirements in the design documents;

[0178] Two third thin plate supports 6 are added to the straight section of the elliptical thin-walled compartment 1. They are symmetrically arranged about the short axis, with two on each side. The two third thin plate supports 6 located on the same side of the short axis are symmetrically arranged about the long axis. All of them are configured to connect one end to the inner wall of the straight section of the elliptical thin-walled compartment 1. The connection point is the point where the deformation curvature is the maximum when the straight section is unsupported. This point is located in the middle of the straight section, biased towards the ribs 3. The direction is through the center of the circle of deformation curvature when the unsupported section is unsupported at the connection point. The other end is connected to the inner support structure 2 of the cylinder.

[0179] like Figure 8 The diagram shown is a cross-sectional view of the part and its supporting structure after the addition of the third thin plate support member 6 for the second time.

[0180] Step f-3. Perform additive manufacturing simulation on the elliptical thin-walled compartment 1 model, which is equipped with ribs 3, cylindrical internal support structure 2, first thin plate support 4, second thin plate support 5, and third thin plate support 6, and obtain the model deformation results.

[0181] Step g-3. Determine whether it is necessary to add thin plate support components based on the deformation results; the simulation deformation results show that the maximum deformation of the elliptical thin-walled section 1 model is 1.0mm, which exceeds the technical requirement of ±0.8mm and does not meet the target deformation requirements in the design documents;

[0182] Two third thin plate supports 6 are added to the straight section of the elliptical thin-walled compartment 1. They are symmetrically arranged about the short axis, with two on each side. The two third thin plate supports 6 located on the same side of the short axis are symmetrically arranged about the long axis. All of them are configured to connect one end to the inner wall of the straight section of the elliptical thin-walled compartment 1. The connection point is the point where the deformation curvature is the maximum when the straight section is unsupported. This point is located in the middle of the straight section, biased towards the second thin plate support 4. The direction is through the center of the circle of deformation curvature when the unsupported section is unsupported at the connection point. The other end is connected to the inner support structure 2 of the cylinder.

[0183] like Figure 9 The diagram shown is a cross-sectional view of the part and its supporting structure after the third thin plate support member 6 was added for the third time.

[0184] Step f-4. Perform additive manufacturing simulation on the elliptical thin-walled section 1 model, which is equipped with ribs 3, cylindrical internal support structure 2, first thin plate support 4, second thin plate support 5, and third thin plate support 6, and obtain the model deformation results.

[0185] Step g-5. Determine whether a thin-plate support needs to be added based on the deformation results; the simulation deformation results show that the maximum deformation of the elliptical thin-walled section 1 model is 0.7mm, which meets the technical requirement of ±0.8mm and the target deformation requirement in the design document, and is determined to be the additive manufacturing model of the elliptical thin-walled section.

[0186] In step two, the additive manufacturing parameters for the elliptical thin-walled section 1 body, which has high fusion strength, are set as follows: laser power is 300W, scanning speed is 800mm / s, and the border is scanned. For the inner support dimensional structure, the solid support parameters, which have lower fusion strength, are set: laser power is 200W, scanning speed is 1000mm / s, and the border is not scanned. The scanning spacing and powder thickness are the same for both the body and the inner support dimensional structure. The additive manufacturing volume energy density of the elliptical thin-walled section 1 body model is set to 1.875 times that of the inner support dimensional structure model.

[0187] In step three, the heat treatment is annealing. In this embodiment, vacuum annealing is used, the annealing temperature is 700℃, and the holding time is 4 hours.

[0188] In step four, the elliptical thin-walled compartment 1 part in this embodiment needs to be cut and its outer surface ground, and the matching structure that requires an internal support structure needs to be machined.

[0189] The integral component is clamped using a fitting fixture 7 that can be connected to the internal support structure, and the elliptical compartment is machined. The fitting fixture is a cover plate with two cylindrical protrusions. The outer diameter of the protrusions is the same as the inner diameter of the cylindrical internal support structure 2. The protrusions can be engaged with the cylindrical internal support structure 2. The assembly tolerance between the internal support structure and the fitting fixture is treated as a clearance fit, and the clearance fit tolerance is H7 / g6.

[0190] In step five, wire cutting is used to remove the middle integral structure of the inner support structure, leaving only the peripheral thin plate structure. Then, a fitter uses tools such as chisels, pneumatic chisels, and air grinders to remove the remaining parts.

[0191] Measurements show that the maximum deformation of the elliptical thin-walled section 1 manufactured in this embodiment is 0.6 mm, which meets the target deformation requirements in the design documents.

[0192] Example 3

[0193] This embodiment provides a method for controlling the surface accuracy of an elliptical thin-walled section 1 in additive manufacturing.

[0194] like Figure 10 As shown, the target part for additive manufacturing is an elliptical thin-walled compartment 1 with a major axis diameter of 400mm, a minor axis diameter of 200mm, a height of 200mm, a minimum wall thickness of 3mm, a major axis dimension of 400mm, and a material of titanium alloy. The design documents specify that the deformation for additive manufacturing should be less than ±0.8mm.

[0195] The additive manufacturing surface accuracy control method specifically includes the following steps:

[0196] Step 1: Design the additive manufacturing model of the elliptical thin-walled section, and generate the body model of the elliptical thin-walled section 1 and its internal support structure model. The internal support structure includes a mating structure that can be connected with subsequent heat treatment and machining tooling.

[0197] Step 2: Integral additive manufacturing of the elliptical thin-walled section 1 and its internal support dimensional structure model to obtain the overall component;

[0198] Step 3: Use the fitting tool 7, which can be connected to the internal support structure, to clamp the whole component and perform integrated heat treatment on the whole component to eliminate residual stress inside the structure.

[0199] Step 4: Determine whether machining is required for the mating structure of the internal support structure. If so, use the mating fixture 7, which can be connected to the mating structure of the internal support structure, to clamp the overall component and machine the elliptical compartment. If not, proceed to Step 5.

[0200] Step 5: Remove the internal support structure.

[0201] In step one, an additive manufacturing model of the elliptical thin-walled section is designed, generating the main body model of the elliptical thin-walled section 1 and its internal support dimensional structure model, specifically including:

[0202] Step a. Construct the model of the elliptical thin-walled section 1.

[0203] Step b. Determine the center and outer radius of the cylindrical internal support structure 2 based on the major axis dimension and minimum machining spacing of the elliptical thin-walled section 1, and symmetrically set two cylindrical internal support structures 2 on both sides of the minor axis centerline of the inner surface of the elliptical thin-walled section 1.

[0204] Specifically, cylindrical internal support structures 2 are symmetrically arranged on both sides of the center line of the minor axis of the inner surface of the elliptical thin-walled section 1. The centers of the two cylindrical internal support structures 2 are respectively set at the points that are off-center from the quarter points of the major axis diameter of the inner surface of the elliptical thin-walled section 1. The outer radius of the cylindrical internal support structure 2 is set as 1 / 4 of the major axis diameter of the elliptical thin-walled section 1 minus the minimum machining spacing of 10mm, which equals 90mm. The cylindrical internal support structure 2 is a concentric double-layer cylindrical structure, with each layer of cylinder having a thickness of 2mm and a distance of 1mm between the two layers of cylinders. The total thickness of the cylindrical internal support structure 2 is 5mm, and the two layers of cylinders are connected by a dot matrix.

[0205] Step c. Determine the location of the rib plate 3 based on the major axis dimension of the elliptical thin-walled section 1 and the outer diameter dimension of the cylindrical internal support structure, and set the rib plate 3 along the minor axis direction between the two cylindrical internal support structures 2;

[0206] Specifically, a rib plate 3 is set between the two cylindrical internal support structures 2. The rib plate 3 is set perpendicular to the cross section along the short axis direction. The rib plate 3 penetrates the interior of the elliptical thin-walled section 1, and its two ends are respectively connected to the inner side of the straight section sidewall on both sides of the short axis direction of the elliptical thin-walled section 1. The rib plate 3 is composed of parallel double-layer plates, each layer of which is 2.5mm thick. The distance between the double-layer plates is 1mm, and the total thickness of the rib plate 3 is 6mm. Multiple thin plates are used to connect the double-layer plates. The two ends of the thin plates are respectively connected to the side of the double-layer plates at an angle. The thin plates are staggered in pairs to form an X shape. Several pairs of thin plates are distributed between the double-layer plates, so that the space between the double-layer plates forms a support structure with triangular and quadrilateral cross sections. The shortest distance between the rib plate 3 and the outer surface of the two cylindrical internal support structures 2 is 7mm.

[0207] Step d. Determine the setting direction of the first thin plate support 4 according to the center position of the cylindrical internal support structure 2. The first thin plate support 4 is connected to the outer surface of the cylindrical internal support structure 2 at one end and to the nearest rib 3 at the other end.

[0208] Specifically, the thickness of the first thin plate support 4 is 3mm. The first thin plate support 4 is symmetrically arranged about the short axis, with 3 on each side, for a total of 6. Among them, the 3 first thin plate support 4 located on the same side of the short axis are symmetrically arranged about the long axis. Specifically, each of them has one end connected to the outer surface of the cylindrical inner support structure 2 and the other end connected to the rib plate 3, pointing towards the center of the cylindrical inner support structure 2.

[0209] Step e. Determine the setting direction of the second thin plate support 5 according to the center position of the arc segment of the elliptical thin-walled compartment 1. The second thin plate support 5 is connected to the inner wall of the arc segment of the elliptical thin-walled compartment 1 at one end and to the outer surface of the cylindrical inner support structure 2 at the other end.

[0210] Specifically, the thickness of the second thin plate support 5 is 3mm. The second thin plate support 5 is symmetrically arranged about the short axis, with 10 on each side. Two of them are located at the intersection of the arc segment and the straight segment. All of them are configured to connect one end to the inner wall of the arc segment of the elliptical thin-walled compartment 1 and the other end to the outer surface of the cylindrical inner support structure 2, pointing towards the center of the arc segment of the elliptical thin-walled compartment 1.

[0211] Step f. Perform additive manufacturing simulation on the elliptical thin-walled section 1 model, which is equipped with ribs 3, cylindrical internal support structure 2, first thin plate support 4, and second thin plate support 5, and obtain the model deformation results.

[0212] Step g. Determine whether a thin plate support needs to be added based on the deformation results; if the model deformation results do not meet the target deformation requirements, then add a third thin plate support 6; one end of the third thin plate support 6 is connected to the inner wall of the straight section of the elliptical thin-walled compartment, and the connection point is the point where the deformation curvature is the maximum when the straight section is unsupported. The third thin plate support 6 passes through the center of the circle of deformation curvature when the connection point is unsupported, and the other end is connected to the cylindrical internal support structure, rib plate or the first thin plate support 4.

[0213] Step h. Repeat steps f and g until the maximum deformation of the simulated elliptical thin-walled section 1 model is less than ±0.8 mm, meeting the target deformation requirement. In this embodiment, steps f and g are repeated four times to obtain the following result. Figure 11 The part body and its supporting structure are shown. The added third thin-plate support members are symmetrical about the short axis, with 6 on each side; 4 on each side are configured such that one end connects to the inner wall of the straight section of the elliptical thin-walled compartment 1, and the other end connects to the outer surface of the cylindrical inner support structure 2, with the direction passing through the center of the circle of curvature of the deformation when there is no support at the connection point with the elliptical thin-walled compartment 1; 2 on each side are configured such that one end connects to the inner wall of the straight section of the elliptical thin-walled compartment 1, and the other end connects to the rib plate 3, with the direction passing through the center of the circle of curvature of the deformation when there is no support at the connection point with the elliptical thin-walled compartment 1.

[0214] After simulating the deformation results of direct additive manufacturing of the elliptical thin-walled section 1 and additive manufacturing using the support structure of this invention, the results are shown in the following figures: Figure 13 and Figure 14 As shown in the figure, after adopting the support structure of the present invention, the large deformation of the original compartment was completely eliminated, and the maximum local deformation was reduced from 2.56 mm to 0.67 mm. This result indicates that the support structure of the present invention improves the stability and surface accuracy of the additive manufacturing of the elliptical thin-walled compartment 1, and effectively controls the deformation problem.

[0215] Specifically, during the model design phase, the portions connecting the second thin-plate support 5 and the third thin-plate support 6 to the inner surface of the elliptical thin-walled section 1 are thinned, such as... Figure 12 As shown, the thickness reduction is 2mm.

[0216] In step two, the additive manufacturing parameters for the elliptical thin-walled section 1 body, which has high fusion strength, are set as follows: laser power is 360W, scanning speed is 1000mm / s, and the border is scanned. For the inner support dimensional structure, the solid support parameters, which have lower fusion strength, are set: laser power is 300W, scanning speed is 1600mm / s, and the border is not scanned. The scanning spacing and powder thickness are the same for both the body and the inner support dimensional structure. The additive manufacturing volume energy density of the elliptical thin-walled section 1 body model is set to 1.92 times that of the inner support dimensional structure model.

[0217] In step three, the heat treatment is annealing. In this embodiment, vacuum annealing is used, the annealing temperature is 800℃, and the holding time is 3 hours.

[0218] In step four, if it is determined that no machining is required, use, for example... Figure 15 The mating fixture shown can be connected to the internal support structure to clamp the integral component, and then the outer surface of the elliptical thin-walled compartment 1 is machined. The mating fixture is a cover plate with two cylindrical bosses. The outer diameter of the bosses is the same as the inner diameter of the cylindrical internal support structure 2, and the bosses can be engaged with the cylindrical internal support structure 2.

[0219] In step four, the elliptical thin-walled compartment 1 part in this embodiment needs to be drilled and its outer surface ground, and the mating structure that requires an internal support structure needs to be machined.

[0220] The integral component is clamped using a fitting tool 7 that can be connected to the internal support structure, and the elliptical compartment is machined; using, for example Figure 15 The fitting fixture shown can be connected to the internal support structure to clamp the overall component, and then the outer surface of the elliptical thin-walled section 1 is machined; the assembly tolerance of the internal support structure and the fitting fixture is treated as clearance fit, and the clearance fit tolerance is H7 / h6.

[0221] In step five, wire cutting is used to remove the middle integral structure of the inner support structure, leaving only the peripheral thin plate structure. Then, a fitter uses tools such as chisels, pneumatic chisels, and air grinders to remove the remaining parts.

[0222] Measurements showed that the maximum deformation of the elliptical thin-walled section 1 manufactured in this embodiment was 0.7 mm, which meets the target deformation requirements in the design documents. Subsequent calibration or other procedures are unnecessary, allowing for direct and effective control of surface accuracy.

[0223] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for controlling the surface accuracy of an elliptical thin-walled compartment in additive manufacturing, characterized in that, The method includes the following steps: Step 1: Design the additive manufacturing model of the elliptical thin-walled section, and generate the body model of the elliptical thin-walled section and its internal support structure model. The internal support structure includes a mating structure that can be connected with subsequent heat treatment and machining tooling. The ratio of the major axis diameter X to the minor axis diameter Y of the elliptical thin-walled section is greater than 1.

2. Step 2: Integrate the elliptical thin-walled compartment body and its internal support dimensional structure model into an additive manufacturing process to obtain the overall component; Step 3: Use fitting tooling that can be connected to the internal support structure to clamp the whole component, and perform integrated heat treatment on the whole component to eliminate residual stress inside the structure. Step four: Determine whether the internal support structure needs to be machined. If necessary, use fitting tooling that can be connected to the internal support structure to clamp the overall component and machine the elliptical thin-walled section; if not, proceed to step five. Step 5: Remove the internal support structure; In step one, an additive manufacturing model of the elliptical thin-walled section is designed, generating the elliptical thin-walled section body and its internal support structure model, including: Step a. Construct an elliptical thin-walled section model; Step b. Determine the center and outer radius of the cylindrical internal support structure based on the major axis diameter and minimum machining spacing of the elliptical thin-walled section. Symmetrically set two cylindrical internal support structures on both sides of the minor axis centerline of the inner surface of the elliptical thin-walled section. The minimum machining spacing is the distance between the outer surface of the cylindrical internal support structure and the inner surface of the elliptical thin-walled section where they are closest. It is set according to the machining requirements of removing the internal support structure after additive manufacturing. The value of the minimum machining spacing is 5 to 50 mm. Step c. Determine the rib placement position based on the major axis diameter of the elliptical thin-walled section and the outer diameter of the cylindrical internal support structure, and place the rib along the minor axis between the two cylindrical internal support structures; Step d. Determine the setting direction of the first thin plate support member according to the center position of the cylindrical internal support structure. The first thin plate support member is connected to the outer surface of the cylindrical internal support structure at one end and to the nearest rib at the other end. Step e. Determine the setting direction of the second thin plate support member according to the center position of the arc segment of the elliptical thin-walled compartment section. The second thin plate support member is connected to the inner wall of the arc segment of the elliptical thin-walled compartment section at one end and to the outer surface of the cylindrical inner support structure at the other end. The setting direction of the second thin plate support member points to the center of the arc segment of the elliptical thin-walled compartment section. Step f. Perform additive manufacturing simulation on the elliptical thin-walled compartment model equipped with ribs, a cylindrical internal support structure, a first thin-plate support, and a second thin-plate support to obtain the model deformation results; Step g. Determine whether a thin-plate support needs to be added based on the deformation results. If the model deformation results do not meet the target deformation requirements, then a thin-plate support is added; if the model deformation results meet the target deformation requirements, then it is determined to be an elliptical thin-walled compartment additive manufacturing model. Step h. Repeat steps f and g until the deformation of the simulated model meets the target deformation requirements.

2. The surface accuracy control method according to claim 1, characterized in that, In step two, the additive manufacturing energy density of the elliptical thin-walled module body model is set to 1.5 to 2 times that of the internally supported dimensional structure model.

3. The surface accuracy control method according to claim 1, characterized in that, In step two, the elliptical thin-walled section is made of titanium alloy. The laser power of the elliptical thin-walled section body is set to 250~400W, the scanning speed is 950~1400mm / s, and the scanning border is scanned.

4. The surface accuracy control method according to claim 3, characterized in that, In step two, the laser power is set to 250~320W and the scanning speed is 1100~1600mm / s for the internal support structure, and the border is not scanned; The scanning spacing and powder coating thickness are the same for the elliptical thin-walled compartment body and the internal support structure.

5. The surface accuracy control method according to claim 1, characterized in that, In step three, the heat treatment is annealing.

6. The surface accuracy control method according to claim 5, characterized in that, In step three, the elliptical thin-walled compartment is made of titanium alloy, and the annealing treatment is vacuum annealing at a temperature of 600~800℃ for 3~5 hours.

7. The surface accuracy control method according to claim 5, characterized in that, In step three, the elliptical thin-walled section is made of aluminum alloy, and the annealing temperature is 200~300℃, with a holding time of 2~3 hours.

8. The surface accuracy control method according to claim 5, characterized in that, In step three, the elliptical thin-walled section is made of high-temperature alloy and is vacuum annealed at a temperature of 500~800℃ for 3~5 hours.

9. The surface accuracy control method according to claim 5, characterized in that, In step three, the elliptical thin-walled section is made of alloy steel, and the annealing temperature is 400~600℃, with a holding time of 3~5h.

Images