Forming method and forming die for ribbed skin product

Abstract

The invention provides a forming method and a forming die for a ribbed skin product, relates to the technical field of metal forming, and aims to solve one of the technical problems that the ribbed skin product is long in processing time consumption, difficult to release residual stress, difficult to guarantee dimensional precision and strength and high in cost. The forming method of the ribbed skin product comprises the following steps that a forming die is provided, and the forming die comprises a bracket and a bottom block; determining a blank model according to the model of the ribbed skin product, and cutting the blank according to the blank model; the cut blank is placed in a forming die, and the blank is located on the bottom block; and the blank is rolled through a pressing roller, and a ribbed skin product is formed. The forming method is short in processing time consumption.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal forming, in particular to a forming method and forming die for a ribbed skin product. BACKGROUND

[0002] Aerospace parts are increasingly developing towards lightweight, and ribbed skin products, as a typical component, are widely used in aerospace vehicles.

[0003] Due to the non-equal wall thickness characteristics of ribbed skin products, they cannot be processed by conventional sheet metal or hot forming processes, and therefore rely on the method of directly milling out the rib and cavity structure by a plate mill. When ribbed skin products are processed by conventional methods, not only is the time-consuming long, but there are also residual stresses after processing, which can cause the parts to warp and deform, and additional heat treatment is required to release the internal stress. This not only increases the manufacturing cost, but also makes it difficult to ensure the dimensional accuracy of the parts. SUMMARY

[0004] The present application aims to provide a forming method and forming die for a ribbed skin product to solve one of the technical problems of long processing time, difficulty in releasing residual stress, difficulty in ensuring dimensional accuracy and strength, and high cost.

[0005] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0006] In a first aspect, the present application provides a forming method for a ribbed skin product, comprising the following steps:

[0007] A forming die is provided, wherein the forming die comprises a bracket and a bottom block;

[0008] A model of a blank is determined according to a model of the ribbed skin product, and the blank is cut according to the model of the blank;

[0009] The cut blank is placed in the forming die, and the blank is located above the bottom block;

[0010] The blank is rolled by a pressure roller to form a ribbed skin product.

[0011] According to at least one embodiment of the present application, the bracket comprises two opposite first positioning plates and two opposite second positioning plates, and the two first positioning plates and the two second positioning plates enclose a cavity.

[0012] According to at least one embodiment of the present application, the top surfaces of the two first positioning plates and the two second positioning plates are flush.

[0013] The bottom block is located in the cavity, and the top surface of the bottom block is lower than the top surface of the first positioning plate to form a containing space for forming the ribbed skin product.

[0014] According to at least one embodiment of the present application, at least one of the first positioning plates is detachably connected with the second positioning plates.

[0015] According to at least one embodiment of the present application, the size and shape of the bottom block are determined according to the size and shape of the bottom cavity of the ribbed skin product, so that the bottom block matches the cavity of the ribbed skin product.

[0016] According to at least one embodiment of the present application, at least one groove is formed on the top surface of the bottom block, which is matched with the rib structure of the ribbed skin product.

[0017] According to at least one embodiment of the present application, the height difference between the top surface of the bottom block and the top surface of the first positioning plate is determined according to the thickness of the ribbed skin product.

[0018] According to at least one embodiment of the present application, when determining the model of the blank according to the model of the ribbed skin product, the following steps are included:

[0019] According to the volume of the ribbed skin product, the volume of the blank is determined.

[0020] According to at least one embodiment of the present application, the pressing roller includes a roller shaft and a connecting shaft arranged at both ends of the roller shaft respectively, the outer diameter of the roller shaft is larger than that of the connecting shaft, and the length of the roller shaft is greater than or equal to the distance between the two first positioning plates; the blank is rolled by the pressing roller, including:

[0021] The blank is rolled by the roller shaft, and the pressure of the roller shaft is in the range of 1000t-2000t.

[0022] In the second aspect, the present application provides a forming mold for realizing the forming method of the first aspect.

[0023] In one or more technical solutions provided in the exemplary embodiments of the present application, at least one of the following beneficial effects can be achieved.

[0024] The forming method of the ribbed skin product of the exemplary embodiment of the present application uses a forming die including a bracket and a bottom block, and the thickness of the ribbed skin product is adapted by the height difference between the top surface of the bottom block and the top surface of the first positioning plate, so that the blank is accurately positioned and uniformly stressed during the rolling process. At the same time, by controlling the temperature of the bottom block and the blank at 470-480°C, the deformation resistance of the blank during the forming process is effectively reduced, thereby improving the plastic flow ability of the metal material. Compared with the conventional forming method of the ribbed skin product, the processing time is significantly shortened from 10-18 hours, and the production efficiency is greatly improved.

[0025] Further, since the temperature of the blank is increased to 470-480°C, the metal flows and the grains are refined during the forming process of the blank, and the mechanical properties after forming can be increased by about 20% compared with the base material.

[0026] Further, compared with the machining forming in the conventional processing method, the heating and rolling process of the aluminum alloy forming die of the present application effectively reduces the residual stress in the forming process and reduces the deformation problem caused by stress release, so that subsequent heat treatment can be omitted, the part size stability and manufacturing precision are significantly improved, and the processing cost is also saved. BRIEF DESCRIPTION OF DRAWINGS

[0027] The accompanying drawings illustrate exemplary embodiments of the present application and, together with the general description of the application given above, and the detailed description of the embodiments given below, serve to explain the principles of the present application. These drawings should be understood to be included in the specification and form a part of the specification;

[0028] Figure 1 is an axonometric structural schematic diagram of a bracket according to an embodiment of the present application;

[0029] Figure 2 is an axonometric structural schematic diagram of a forming die according to an embodiment of the present application;

[0030] Figure 3 is an axonometric structural schematic diagram of a bottom block according to an embodiment of the present application;

[0031] Figure 4 is an axonometric structural schematic diagram of a ribbed skin product according to an embodiment of the present application.

[0032] Reference Signs:

[0033] 11, first positioning plate; 111, positioning hole; 12, second positioning plate; 13, heating table; 14, positioning rod;

[0034] 20, roller; 21, connecting shaft;

[0035] 30, blank; 31, rib structure; 32, cavity;

[0036] 41, recess; 42, through hole. DETAILED DESCRIPTION

[0037] In order to make the technical problems to be solved by the present application, technical solutions and beneficial effects more clearly understood, the present application will be further described in detail below in conjunction with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and not intended to limit the present application.

[0038] Figure 4 is a perspective view of a ribbed skin product according to an embodiment of the present application. As shown in Figure 4 , the ribbed skin product includes a main plate surface and a rib structure 31 and a cavity 32 distributed on the surface of the main plate surface, the rib structure 31 is also called rib or reinforcing rib, and the cavity 32 together constitute the non-equal wall thickness feature of the ribbed skin product, so that it has higher structural strength and rigidity. The ribbed skin product can meet the stringent requirements of aerospace vehicles for lightweight and high strength, while reducing the overall weight and improving the carrying capacity.

[0039] Exemplarily, the distance between the flat surface of the main plate surface (the surface without rib structure 31) of the ribbed skin product and the top surface of the rib structure 31 is 8mm, part of the rib structure 31 can be formed on the surface of the main plate surface, and part or all of the rib structure 31 can also be formed on the bottom surface of the cavity 32 of the main plate surface.

[0040] In the related art, the processing method of the ribbed skin product adopts the way of processing ribs and cavities 32 by a flat plate machine, but there are problems such as long processing cycle, large residual stress and easy deformation, which is difficult to meet the manufacturing requirements of high-precision components, and the processing cycle is 10-18 hours; if the processed parts are heat treated to eliminate residual stress, the cycle is further prolonged, and there is still a risk of deformation during the heat treatment process, which affects the final precision.

[0041] Example one

[0042] The exemplary embodiment of the present application proposes a forming die for realizing the forming method of the ribbed skin product, which includes a bracket and a bottom block, as shown in Figure 1 and Figure 3 , wherein, Figure 1 is a perspective view of a bracket according to an embodiment of the present application; Figure 3 is a perspective view of a bottom block according to an embodiment of the present application.

[0043] Exemplarily, the bracket cooperates with the base block to form a containing space for supporting and positioning the blank 30 in the forming process of the ribbed skin product. The base block is provided with one or more grooves 41 corresponding to the rib structure 31 and a protruding structure matching the cavity 32.

[0044] Specifically, the bracket includes two opposite first positioning plates 11 and two opposite second positioning plates 12, which enclose a cavity. That is, the four positioning plates jointly define a cavity for accommodating the blank 30, wherein the first positioning plate 11 and the second positioning plate 12 are arranged perpendicular to each other to limit the blank 30 in the horizontal and vertical directions, thereby maintaining the stability and positioning accuracy of the blank 30 during the forming process.

[0045] Exemplarily, one or both of the two first positioning plates 11 are detachably connected with the two second positioning plates 12, facilitating disassembly for taking out the formed ribbed skin product and improving production efficiency. For example, the two first positioning plates 11 are fixedly connected with the second positioning plate 12 by screws, and when disassembled, the first positioning plate 11 and the second positioning plate 12 can be separated by loosening the screws, realizing rapid mold opening. The four positioning plates of the bracket are all made of high-strength alloy steel, and the surface is treated by nitriding to improve wear resistance and deformation resistance, maintaining dimensional stability during long-term use.

[0046] In order to solve the problem of universality of the base block to adapt to the rapid change of different specifications of ribbed skin products, the base block adopts a modular structure. As shown in Figure 3 The base block is composed of a plurality of repeated unit modules, which are standardized designed according to the distribution law of the rib structure 31 and the cavity 32 of the ribbed skin product. Each unit module can contain a groove 41 corresponding to the rib and / or a protrusion matching the cavity 32, and after arrangement and combination, a complete base block structure is formed, realizing rapid adaptation of different product specifications.

[0047] For example, as shown in Figure 4 The length, width and height of the ribbed skin product are 500mm×400mm×8mm, and the unit module forming the base block can include two kinds, one is a 60mm×60mm rectangular block and the other is a 480mm×20mm rectangular block, and after arrangement and combination, it is as shown in Figure 3

[0048] Since the forming mold needs to work under certain temperature conditions, in order to solve the problem of size deviation caused by thermal expansion during the forming process and improve the accuracy of the formed ribbed skin product, the size design of the unit module needs to consider the influence of the material thermal expansion coefficient and the forming temperature.

[0049] The size of the unit module at room temperature needs to meet:

[0050] ​

[0051] Among them, D part0 The cavity dimensions of a ribbed skin product at room temperature;

[0052] D die0 This refers to the dimensions of the protrusion of the unit module at room temperature;

[0053] α part The coefficient of linear expansion for products with reinforced skin;

[0054] α die The coefficient of linear expansion of the unit module material;

[0055] ΔT is the difference between the molding temperature and room temperature.

[0056] The dimensions of the unit module at room temperature are compensated for by thermal expansion differences, ensuring a precise match between the unit module protrusion and the product cavity 32 during high-temperature molding.

[0057] For example, such as Figure 1 As shown, a heating platform 13 is also provided at the bottom of the cavity enclosed by the two first positioning plates 11 and two second positioning plates 12 of the forming mold. This heating platform 13 is used for uniform heating of the bottom block, keeping the forming temperature stable within the process requirements range. The heating platform 13 has built-in multi-channel heating tubes and is equipped with a temperature sensor and a closed-loop control system to achieve a temperature control accuracy of ±0.5℃. A thermally conductive pad can be provided between the heating platform 13 and the bottom block to further improve the uniformity of heat conduction and reduce local overheating.

[0058] The overall outline of the base block matches the cavity of the forming mold. In order to maintain the stability of the relative position between each unit module during the rolling process and prevent misalignment or loosening, mortise and tenon structures, plug-in splicing and other methods can be used on each unit module to realize the connection and positioning between unit modules.

[0059] Alternatively, multiple positioning holes 111 are provided on the two first positioning plates 11, and the forming mold also includes multiple positioning rods 14. The positioning rods 14 pass through the positioning holes 111 on the two first positioning plates 11 and the through holes 42 on the corresponding unit modules, fixing each unit module in the cavity of the forming mold and maintaining the stability of the bottom block formed by each unit module under high temperature and high pressure environment.

[0060] Optionally, both the positioning rod 14 and the through hole 42 on the unit module are circular. Each unit module and the positioning rod 14 are securely connected via an interference fit, effectively suppressing minor displacements caused by thermal expansion. Specifically, the diameters of the positioning rod 14 and the through hole 42 on the unit module must meet the following requirements:

[0061] r1(1+α1ΔT)≥r2(1+α2ΔT), Equation 2;

[0062] wherein, r1 is the diameter of the positioning rod at room temperature;

[0063] a1 is the thermal expansion coefficient of the positioning rod at the hot forming temperature;

[0064] ΔT is the difference between the forming temperature and the room temperature;

[0065] r2 is the diameter of the through hole on the unit module at room temperature;

[0066] a2 is the thermal expansion coefficient of the through hole on the unit module at the hot forming temperature.

[0067] Exemplarily, the unit module is made of one of the following materials: forged die steel, stainless steel, 45 steel, and medium silicon molybdenum cast iron; the material of the positioning rod 14 can be 321 stainless steel, which has excellent high-temperature strength and thermal fatigue resistance, and the thermal expansion coefficient is 17.9x10 -6 - -1 When the temperature is 470℃, the diameter is 18mm; at this temperature, the diameter of the through hole 42 on the unit module is 17.7mm, and the two form an interference fit, so that the unit module remains in a stable connected state during the high-temperature and high-pressure forming process, reducing the loosening or deformation caused by the difference in thermal expansion, thereby ensuring the forming precision of the ribbed skin product.

[0068] Figure 2 is a schematic view of the shaft structure of the forming die according to the embodiment of the present application. As shown in the figure, the forming die provided by the exemplary embodiment of the present application further comprises a press roller for roll forming the aluminum alloy ribbed skin blank 30 placed on the unit module profile, the press roller reciprocates along the length direction of the die (the extension direction of the first positioning plate 11), and cooperates with the temperature control of the heating table 13 to realize uniform plastic deformation of the material. Figure 2

[0069] Exemplarily, the press roller comprises a roller shaft 20 and a connecting shaft 21 respectively arranged at both ends of the roller shaft 20, the outer diameter of the roller shaft 20 is greater than the outer diameter of the connecting shaft 21, and the length of the roller shaft 20 is greater than or equal to the spacing between the two first positioning plates 11. The connecting shaft 21 is used to be connected with a driving device to drive the roller shaft 20 to roll on the blank 30 in the cavity of the forming die. Compared with extrusion forming, since roll forming is linear contact forming, the applied pressure is smaller, and the cost of the roll forming machine is orders of magnitude lower than that of the hot forming extrusion machine. Therefore, the production cost and the purchase cost of the forming die of the exemplary embodiment of the present application are both lower.

[0070] ​Furthermore, compared to traditional thermoforming molds, which require a separate mold for each product, the base block of this exemplary embodiment is composed of standardized unit modules. This allows for flexible adjustment of the mold's surface dimensions and structure according to different product requirements, significantly improving the versatility of the forming mold and reducing its development cycle and manufacturing costs.

[0071] For example, such as Figure 2 As shown, a fixing plate is provided on the outer side of the top surface of a first positioning plate 11. The fixing plate and the first positioning plate 11 are L-shaped. The fixing plate can facilitate the fixing of brackets and other equipment, such as fixed connection with external support frames, to maintain the stability of the forming mold during operation.

[0072] Example 2

[0073] To address the issue of time-consuming molding methods for ribbed skin products, this invention also provides a molding method for ribbed skin products, using the molding mold from Embodiment 1 to produce the ribbed skin product. The molding method includes the following steps:

[0074] Step 1: Provide a forming mold, wherein the forming mold includes a bracket and a base block.

[0075] Based on the dimensions and shape of the bottom cavity (mold) of the ribbed skin product, the dimensions and shape of the bottom block are determined so that the bottom block matches the mold 32 of the ribbed skin product. The bottom block is composed of multiple unit modules, and some or all of the unit modules have grooves 41 formed on their top surfaces. The grooves 41 are used to accommodate the rib structure 31 part of the aluminum alloy ribbed skin blank 30.

[0076] Furthermore, based on the size and shape of the cavity of the ribbed skin product, the size and shape of the bottom block are determined, that is, the size and shape of the unit module are determined. The top surface of the unit module has protrusions that are distributed alternately with the grooves 41 to form the cavity 32 of the bottom surface of the ribbed skin product.

[0077] Assemble the base block according to the selected unit module, fix it in the bracket by positioning rod 14, and place it on the heating platform 13 to ensure good contact between the base block and the heating platform 13 and achieve uniform heat conduction.

[0078] It should be noted that when selecting unit modules, the height difference between the top surface of the bottom block and the top surface of the first positioning plate 11 should be determined according to the material thickness of the ribbed skin product. The top surfaces of the first positioning plate 11 and the second positioning plate 12 are flush to ensure that the ribbed skin blank 30 makes stable contact with the mold positioning surface during the roll forming process.

[0079] Step 2: Determine the blank model based on the model of the ribbed skin product, and cut out the final blank 30 according to the blank model.

[0080] The volume of the blank 30 meets the volume requirement of the material needed for forming, which needs to meet:

[0081]

[0082] Wherein, v0 is the volume of the ribbed skin product; v1 is the volume of the blank.

[0083] Then, the size of the blank 30 is determined according to the volume of the blank 30, and the blank 30 can be made by using a plate shearing machine, machining, water cutting, etc.

[0084] Step 3, place the cut blank 30 into the forming mold (the accommodating space surrounded by the bracket and the bottom block), and the blank 30 is located above the bottom block.

[0085] Step 4, the heating table 13 heats each unit module and the blank 30, and the temperature reaches the preset temperature after 3 minutes, and then the rolling can be performed. The preset temperature is in the range of 470℃-480℃, for example, it can be 470℃, 471℃, 472℃, 473℃, 474℃, 475℃, 476℃, 477℃, 478℃, 479℃, 480℃ or in the range of any two of the above values.

[0086] Then start the pressure roller, and continuously roll the blank 30 along the predetermined trajectory under the driving of the hydraulic system at a predetermined pressure until the blank 30 is flush with the top surface of the bracket (the first positioning plate 11 and the second positioning plate 12). The preset pressure is in the range of 1000t-2000t, for example, it can be 1000t, 1100t, 1200t, 1300t, 1400t, 1500t, 1600t, 1700t, 1800t, 1900t, 2000t or in the range of any two of the above values.

[0087] After rolling, the demolding process of the ribbed skin product is performed, the pressure roller is first lifted, then the first positioning plate 11 and the second positioning plate 12 of the bracket are disassembled, and then the formed ribbed skin product is taken out from the bottom block, and the demolding is completed.

[0088] Example three

[0089] The material of the ribbed skin product of this embodiment is 5A06 aluminum alloy, the thickness is 8mm, the length and width size is 500mmx400mm, and it has a non-equal wall thickness rib structure. The forming method of the ribbed skin product comprises the following steps:

[0090] The material of the unit module is selected to be stainless steel, and the material of the positioning rod 14 is 321 stainless steel. The volume of the ribbed skin product is 743907mm 3 , and the volume of the blank 30 is 1600000mm 3The size of the blank 30 is 8 mm x 400 mm x 500 mm, which meets the material volume requirement for forming.

[0091] The blank 30 is placed in the accommodating space of the cavity of the assembled forming die, the heating table 13 is controlled to heat the blank 30 and the unit module, the temperature is raised to 470 DEG C and kept for 3 min, then the pressure roller is started, and the pressure roller is continuously rolled along the predetermined track under the driving of the hydraulic system at a pressure of 1500 t until the blank 30 is flush with the top surface of the bracket.

[0092] After rolling, the pressure roller is lifted, the first positioning plate 11 and the second positioning plate 12 on the bracket are disassembled, the formed ribbed skin product is taken out from the bottom block, and the demolding is completed.

[0093] Example Four

[0094] The difference between this example and example three is that when the blank 30 and the unit module are heated, the heating temperature is set to 480 DEG C and kept for 3 min, and then the rolling step is started.

[0095] Comparative Example One

[0096] The difference between this comparative example and example three is that when the blank 30 and the unit module are heated, the heating temperature is set to 460 DEG C and kept for 3 min, and then the rolling step is started.

[0097] Comparative Example Two

[0098] The difference between this comparative example and example three is that when the blank 30 and the unit module are heated, the heating temperature is set to 490 DEG C and kept for 3 min, and then the rolling step is started.

[0099] It is detected that the mechanical properties of the ribbed skin products obtained in example three, example four, comparative example one and comparative example two under the same test conditions are shown in table 1.

[0100] Table 1 Mechanical properties of ribbed skin products

[0101]

[0102] From the data of Table 1, it can be seen that the heating temperature (forming temperature) has a significant influence on the forming time and mechanical properties of the ribbed skin product. When the heating temperature of Comparative Example 1 is 460℃, although the yield strength and tensile strength decrease slightly, the forming time is prolonged to 5 minutes, indicating that the material plasticity is insufficient, resulting in an increase in deformation resistance and a decrease in forming efficiency; while Comparative Example 2 has a forming time comparable to that of Example 3 and Example 4 at 490℃, but the yield strength decreases significantly to 152 MPa, and the tensile strength also decreases, indicating that a too high temperature can lead to grain coarsening and deterioration of material strength. In contrast, the comprehensive mechanical properties of Example 3 and Example 4 are relatively superior, and the mechanical properties of the material can be improved by about 20% relative to the blank, indicating that a suitable forming temperature can effectively balance the forming efficiency and microstructure performance.

[0103] Compared with the prior art, the forming method of the ribbed skin product of the exemplary embodiments of the present application significantly shortens the processing time, significantly improves the processing efficiency, and does not cause mechanical stress, effectively reducing the warping deformation problem caused by residual stress after mechanical processing. Further, the flexible combination of unit modules realizes the sharing of a set of molds for multiple models of products, and also saves the cost of forming molds.

[0104] Those skilled in the art should understand that the above embodiments are only for clearly illustrating the present application, and are not intended to limit the scope of the present application. Based on the above disclosure, other changes or modifications can also be made by those skilled in the art, and these changes or modifications are still within the scope of the present application.

Claims

1. A method for forming a product with ribbed skin, characterized in that, Includes the following steps: A forming mold is provided; wherein the forming mold includes a bracket and a base block; The blank model is determined based on the model of the ribbed skin product, and the blank is cut out based on the blank model. The cut blank is placed into the forming mold, and the blank is positioned on top of the bottom block; The blank is rolled by pressure rollers to form a ribbed skin product.

2. The forming method according to claim 1, characterized in that, The bracket includes two opposing first positioning plates and two opposing second positioning plates, which enclose a cavity.

3. The forming method according to claim 2, characterized in that, The top surfaces of the two first positioning plates and the two second positioning plates are flush. The bottom block is located in the cavity, and the top surface of the bottom block is lower than the top surface of the first positioning plate to form an accommodating space, which is used to form a ribbed skin product.

4. The forming method according to claim 3, characterized in that, At least one of the two first positioning plates is detachably connected to the two second positioning plates.

5. The forming method according to claim 3, characterized in that, The size and shape of the base block are determined based on the size and shape of the bottom cavity of the ribbed skin product, so that the base block matches the cavity of the ribbed skin product.

6. The forming method according to claim 5, characterized in that, The top surface of the base block has at least one groove, which is adapted to the rib structure of the ribbed skin product.

7. The forming method according to claim 6, characterized in that, The height difference between the top surface of the bottom block and the top surface of the first positioning plate is determined based on the material thickness of the ribbed skin product.

8. The forming method according to claim 6, characterized in that, When determining the blank model based on the model of the ribbed skin product, the following steps are included: The volume of the blank is determined based on the volume of the ribbed skin product.

9. The forming method according to claim 6, characterized in that, The pressure roller includes a roller and connecting shafts respectively disposed at both ends of the roller. The outer diameter of the roller is larger than the outer diameter of the connecting shaft, and the length of the roller is greater than or equal to the distance between the two first positioning plates. Roll pressing the blank using pressure rollers includes: The blank is rolled by the roller, and the pressure of the roller ranges from 1000t to 2000t.

10. A forming mold, characterized in that, Used to implement the forming method according to any one of claims 1-9.

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