Forming method of combined variable-wall-thickness aluminum skin

Abstract

The invention discloses a forming method of a combined variable-wall-thickness aluminum skin, which comprises the following steps of: in a spherical area forming stage, pre-pressing a first spherical section by using a first ejection piece, providing a stable initial molded surface for subsequent spinning roller spinning, and avoiding acting force concentration when a spinning roller directly acts on a blank which is not pre-formed; the mandrel rotates to drive a blank to synchronously rotate, the spinning roller performs multiple times of spinning from the first spherical section, and only small-amplitude material deformation and thinning are realized in each spinning, so that the problem of material accumulation is effectively relieved, the extrusion strength of single spinning on the material is reduced, the flow resistance of the material is reduced, and in the forming stage of a cylindrical surface area, the yield of the material is improved. The cylindrical surface area is gradually thinned by the spinning roller, so that the axial flow and the radial flow of the material are always kept coordinated, and the material flow difficulty caused by overlarge single forming amount is avoided; and the tensile stress generated by each pass of spinning is controlled within the material bearing limit range, so that the problem that cracks are generated due to overlarge stress in the spun thinned area is thoroughly solved.

Description

Technical Field

[0001] This application relates to the field of aluminum alloy spinning forming technology, and in particular to a forming method for a combined variable wall thickness aluminum skin. Background Technology

[0002] In aerospace, high-end equipment manufacturing, and other fields, the fairing serves as a crucial component for protecting core engine components from external environmental corrosion and reducing airflow resistance. Its performance and forming quality directly affect the operational stability and aerodynamic efficiency of the entire equipment. Currently, common fairing designs are mostly combinations of spherical and cylindrical structures. This structure not only meets aerodynamic shape requirements but also provides ample installation and protection space for core engine components, thus finding widespread application in related fields.

[0003] However, because fairings must simultaneously meet requirements for structural strength, aerodynamic performance, and installation accuracy, their product structures exhibit significant characteristics such as complex shapes, uneven wall thickness, and high dimensional accuracy requirements, posing extremely stringent challenges to forming and manufacturing technologies. Among existing manufacturing processes, spin forming technology has become one of the main forming methods for rotating components like fairings due to its advantages such as high material utilization, excellent mechanical properties of formed parts, and the ability to achieve integrated forming of complex rotating parts.

[0004] However, in actual production, the existing spinning forming technology faces insurmountable technical bottlenecks when using the fairing with the above-mentioned spherical and cylindrical combined structure. In particular, when using a single-stage strong spinning forming process, serious problems such as material accumulation, difficult material flow, and high risk of cracking are exposed uncontrollably, making it difficult for the traditional single-stage strong spinning forming process to meet the high precision and high quality forming requirements of the combined structure fairing. Summary of the Invention

[0005] In view of the deficiencies in the prior art, this application provides a forming method for a combined variable wall thickness aluminum skin to solve the problems of high forming difficulty and low reliability of the combined variable wall thickness aluminum skin in the prior art.

[0006] The above-mentioned objectives of this application are mainly achieved through the following technical solutions: A method for forming a composite variable wall thickness aluminum skin, the forming method comprising: Select blanks with varying wall thickness; Prepare a core mold, a first ejector, and a second ejector according to molding requirements. The core mold is coaxially assembled to the rotating end of the spinning equipment. The first top piece is coaxially assembled to the pressing end of the spinning equipment. The blank is coaxially arranged between the core mold and the first top piece. After pressing the first spherical section onto the blank using the first top piece, the first top piece is disassembled. The spinning wheel is assembled onto the spinning equipment, and the second top piece is coaxially assembled onto the pressing end of the spinning equipment. After the second top piece is pressed onto the blank, the core mold is rotated, and at the same time, the spinning wheel is operated to spin the spherical area of ​​the blank from the first spherical section to the cylindrical section until the thickness of the spherical area of ​​the blank reaches the design requirements. The spinning wheel is operated from the spherical region of the billet to the cylindrical region of the billet, and spins the billet in the cylindrical region until the thickness of the cylindrical region of the billet reaches the required level, thus obtaining the initial product; Remove the initial product and process the end face allowance of the initial product as required to obtain the finished product.

[0007] In an optional implementation, when taking a blank with variable wall thickness, the sheet is first processed into a round blank with variable wall thickness as required, and the thickness of the round blank increases uniformly from the center outward along the radial direction.

[0008] In an optional implementation, when taking blanks with variable wall thickness, the processed blanks are sent to a heat treatment equipment for annealing. The annealing temperature is controlled at 350-360℃, the holding time is 150-200min, and the blanks are air-cooled after the holding time is completed.

[0009] In an optional implementation, when taking blanks with variable wall thickness, ultrasonic testing equipment is used to inspect the blanks. If cracks are detected in the blanks, they are discarded, and the blanks are reprocessed and inspected again until the test results meet the requirements.

[0010] In an optional embodiment, the core mold includes a main body, an end cap, and a stripper rod. One end of the main body is provided with an mounting port for assembling the end cap. One end of the stripper rod is connected to the end cap, and the other end passes through the main body and extends to the other side of the main body. The stripper rod can move axially and drive the end cap to push out the initial product.

[0011] In an optional embodiment, when assembling the end cap, the transition between the end cap and the outer spherical surface of the main body is kept smooth, and the circular runout of the spinning surface on the spinning wheel, the cylindrical surface of the mandrel, and the spherical surface of the mandrel is checked to ensure that they meet the requirements.

[0012] In an optional embodiment, before the first spherical segment performs multiple spins on the spherical region of the blank, the position of the spinning wheel is adjusted so that there is a first gap between the spinning wheel and the spherical surface of the mandrel. Before the spinning wheel is repeatedly spun from the spherical region of the blank to the cylindrical region of the blank, the position of the spinning wheel is adjusted so that there is a second gap between the spinning wheel and the cylindrical surface of the mandrel, and the first gap is larger than the second gap.

[0013] In an optional implementation, when the spinning wheel repeatedly spins the blank in the spherical area, the spinning wheel is first operated to repeatedly apply force to the blank until the blank adheres to the spherical area of ​​the mandrel, and then the spinning wheel is operated to repeatedly apply force to the blank until the blank is reduced to the required thickness.

[0014] In an optional embodiment, the contact area between the first top piece and the blank is greater than the contact area between the second top piece and the blank. Two rotating wheels are arranged, each with rounded corners, and they are symmetrically arranged on both sides of the core mold.

[0015] In an optional embodiment, after removing the initial product, the initial product is sent to a heat treatment device for annealing. The annealing temperature is controlled at 350-360℃, and the holding time is 150-200 minutes. After the holding time is completed, the initial product is air-cooled, and then the end face allowance of the initial product is machined until the end face size and flatness of the initial product meet the requirements.

[0016] Compared with the prior art, the advantages of this application are: The forming method described in this application is used for forming a composite variable wall thickness aluminum skin. The forming method involves first taking a variable wall thickness blank; preparing a core mold, a first ejector, and a second ejector according to forming requirements; coaxially assembling the core mold to the rotating end of a spinning equipment; coaxially assembling the first ejector to the pressing end of the spinning equipment; coaxially arranging the blank between the core mold and the first ejector; pressing a first spherical segment onto the blank using the first ejector, then disassembling the first ejector; taking a spinning wheel and assembling it to the spinning equipment; coaxially assembling the second ejector to the pressing end of the spinning equipment; pressing the second ejector onto the blank; rotating the core mold; and repeatedly spinning the first spherical segment onto the spherical region of the blank until the thickness of the spherical region reaches the required level; repeatedly spinning the spherical region onto the cylindrical region of the blank until the thickness of the cylindrical region reaches the required level, thus obtaining a preliminary product; removing the preliminary product and machining the end face allowance as required to obtain the finished product.

[0017] This forming method precisely addresses the shortcomings of existing technologies through a phased, multi-pass spinning operation: In the spherical region forming stage, the first spherical segment is pre-pressed using the first extruder, providing a stable initial profile for subsequent spinning by the rotary wheel, thus avoiding force concentration when the rotary wheel directly acts on the unformed blank; the core mold rotates, causing the blank to rotate synchronously, and the rotary wheel performs multiple spinning operations starting from the first spherical segment. Each spinning operation only achieves a small degree of material deformation and thinning. This multi-pass motion allows the material sufficient time to flow uniformly along the core mold surface in the spherical region, effectively alleviating the problem of material accumulation in the transition area during traditional single-pass spinning, while also reducing the extrusion strength of the material during a single spinning operation and reducing material flow resistance. During the cylindrical region forming stage, the spinning wheel smoothly transitions from the already formed spherical region to the cylindrical region, continuing the multi-pass spinning motion logic. The mandrel rotates continuously and stably to ensure uniform stress on the blank. The spinning wheel gradually thins the cylindrical region, ensuring that the material flow in the axial and radial directions remains coordinated, avoiding material flow difficulties caused by excessive single forming volume. Furthermore, the multi-pass spinning disperses the axial tensile force, and the tensile stress generated by each pass is controlled within the material's bearing limit, completely solving the problem of cracks caused by excessive stress in the already thinned region.

[0018] This forming method employs a segmented forming strategy, separating the forming processes of spherical and cylindrical surfaces. By combining pre-pressed surfaces with multi-pass spinning, it achieves precise control over the forming process of complex-shaped parts. Furthermore, the coordinated positioning of the first and second ejectors and the core mold, along with the orderly planning of the spinning wheel's motion path, ensures the coaxiality and stability of the blank during the forming process, guaranteeing dimensional accuracy control. Moreover, the multi-pass, small-deformation spinning method improves material flowability and reduces the risk of forming defects. Ultimately, this method enables high-quality forming of composite variable-wall-thickness aluminum skins, achieving dimensional accuracy that meets design drawing requirements. It significantly improves the part production pass rate and efficiency while ensuring the mechanical property stability of the formed parts, meeting the stringent requirements of related fields for fairing components. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 A schematic flowchart of the forming method provided in the embodiments of this application; Figure 2 This is a structural diagram of the first top piece during operation, provided in an embodiment of this application. Figure 3 This is a structural diagram of the second top piece during operation, provided in an embodiment of this application. In the diagram: 100, blank; 200, core mold; 201, main body; 202, end cap; 203, unloading rod; 301, first ejector; 302, second ejector; 401, first gap; 402, second gap; 500, rotating wheel. Detailed Implementation

[0021] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be noted that the description of these embodiments is intended to aid in understanding the invention, but does not constitute a limitation thereof. The specific structural and functional details disclosed herein are merely for describing exemplary embodiments of the invention. However, the invention can be embodied in many alternative forms and should not be construed as being limited to the embodiments described herein.

[0022] Because fairings must simultaneously meet requirements for structural strength, aerodynamic performance, and installation accuracy, their structures are characterized by complex shapes, uneven wall thicknesses, and high dimensional accuracy requirements, posing extremely stringent challenges to forming and manufacturing technologies. Among existing manufacturing processes, spin forming technology has become one of the main forming methods for rotating components such as fairings due to its advantages such as high material utilization, excellent mechanical properties of formed parts, and the ability to achieve integrated forming of complex rotating parts.

[0023] In actual production, the use of existing spinning forming technology for fairings with the aforementioned spherical and cylindrical combined structure faces insurmountable technical bottlenecks, especially when using a single-stage strong spinning forming process, where the technical defects are particularly prominent. In the transition area between the spherical and cylindrical surfaces, due to the large difference in curvature between the two surfaces, the extrusion force of the rotating wheel on the material is concentrated during the first strong rotation, causing the material in this area to be unable to flow in a timely and uniform manner. This results in obvious material accumulation at the front end of the rotating wheel, which not only damages the shape of the part but also creates potential quality problems for subsequent processing.

[0024] Limited by the single forming volume and fixed forming path of a single strong spin, the flow channel of the material during the forming process is restricted, especially in the transition area. The radial and axial flow coordination of the material is poor, and it is impossible to achieve uniform distribution according to the part surface requirements, which further aggravates the excessive accumulation or shortage of local material.

[0025] A single spin forming process requires applying a large axial tensile force to the material to achieve material thinning and mold application. However, in the thinned area, the mechanical properties of the material have changed, its tensile strength has decreased, and the excessive axial tensile stress exceeds the material's bearing limit, which can easily lead to cracks in this area, directly causing part scrap and seriously affecting the production qualification rate and production efficiency.

[0026] like Figure 1 As shown, Figure 1 This is a schematic flowchart of the forming method provided in the embodiments of this application; a forming method for a combined variable wall thickness aluminum skin, the forming method comprising: Take 100 of the blank with variable wall thickness; A core mold 200, a first ejector 301, and a second ejector 302 are prepared according to molding requirements. The core mold 200 is coaxially assembled to the rotating end of the spinning equipment. like Figure 2 As shown, Figure 2 This is a schematic diagram of the structure of the first top piece 301 during operation according to an embodiment of this application. The first top piece 301 is coaxially assembled to the pressing end of the spinning equipment. The blank 100 is coaxially arranged between the core mold 200 and the first top piece 301. After the first top piece 301 is pressed into the blank 100 to form the first spherical section, the first top piece 301 is disassembled. like Figure 3 As shown, Figure 3 This is a schematic diagram of the structure of the second top piece 302 during operation according to an embodiment of this application. The spinning wheel 500 is assembled onto the spinning equipment, and the second top piece 302 is coaxially assembled onto the pressing end of the spinning equipment. After the second top piece 302 is pressed onto the blank 100, the mandrel 200 is rotated, and the spinning wheel 500 performs multiple spinning operations on the spherical area of ​​the blank 100 from the first spherical section until the thickness of the spherical area of ​​the blank 100 reaches the required level. The operating rotary wheel 500 performs multiple spin presses from the spherical area of ​​the billet 100 to the cylindrical area of ​​the billet 100 until the thickness of the cylindrical area of ​​the billet 100 reaches the required level, thus obtaining the initial product. Remove the initial product and process the end face allowance of the initial product as required to obtain the finished product.

[0027] Furthermore, when selecting the blank 100 with variable wall thickness, an aluminum alloy blank 100 with a suitable thickness is selected according to the final variable wall thickness requirement of the aluminum skin to be formed. The initial thickness distribution of the blank 100 needs to match the final wall thickness change trend of the part. For example, a machining allowance slightly larger than the finished product thickness is reserved in the spherical area corresponding to the blank 100 segment to provide sufficient material adjustment space for subsequent spinning forming and avoid local wall thickness failure after forming due to improper initial blank 100 thickness. At the same time, the blank 100 needs to undergo pretreatment processes, such as deburring and surface oil cleaning, to improve reliability.

[0028] When preparing the core mold 200, the first ejector 301, and the second ejector 302, the core mold 200, the first ejector 301, and the second ejector 302 are prepared according to the molding requirements. The outer surface profile of the core mold 200 must be completely adapted to the inner surface profile of the finished aluminum skin. The core mold 200 is made of high-strength alloy material to ensure that it does not deform when subjected to the extrusion of the blank 100 and the force of the spinning wheel 500 during the spinning process. One end of the core mold 200 is provided with a connection structure adapted to the rotating end of the spinning equipment. The core mold 200 and the rotating end of the spinning equipment are coaxially assembled through key connection or flange connection. The coaxiality error is controlled within the required range to ensure the stability of the blank 100 during subsequent rotation. One end of the first ejector 301 is arranged as an arc-shaped structure that matches the spherical section of the core mold 200. Its curvature is consistent with the curvature of the first spherical section to be formed. The surface of the first ejector 301 needs to be polished to avoid scratching the surface of the blank 100 during pressing. One end of the second top piece 302 is also arranged as an arc-shaped structure that matches the spherical section of the core mold 200. Its curvature is consistent with the curvature of the first spherical section to be formed, ensuring that it can form a stable axial support for the blank 100 and prevent the blank 100 from axially moving during the spinning process.

[0029] Subsequently, the first ejector 301 is coaxially assembled to the pressing end of the spinning equipment via bolt connection or quick-clamping structure, ensuring that the coaxiality error between the first ejector 301 and the core mold 200 is within the required range. The blank 100 is coaxially arranged between the core mold 200 and the first ejector 301, with one side of the blank 100 contacting the core mold 200 and the other end aligned with the pressing end of the first ejector 301. Through the pressing system, the first ejector 301 is controlled to apply a pressing force to the blank 100 at a preset feed speed, pressing out a first spherical segment on the blank 100 that is initially adapted to the spherical segment of the core mold 200. During the pressing process, the pressure sensor can monitor the change of pressing force in real time to avoid excessive pressure causing excessive deformation of the blank 100 or insufficient pressure preventing the formation of a complete first spherical segment. After the first spherical segment is formed, the pressing system is turned off, and the first ejector 301 is removed according to the preset disassembly procedure. During the disassembly process, it is necessary to avoid contact between the tools and the formed first spherical segment to prevent damage to the surface accuracy of the sphere.

[0030] Next, a suitable spinning wheel 500 is selected and assembled onto the spinning wheel 500 holder using a tool holder fixture. The installation angle of the spinning wheel 500 is adjusted so that the angle between the working surface of the spinning wheel 500 and the tangent of the outer surface of the mandrel 200 is controlled between 15° and 30°, ensuring a stable extrusion and thinning effect on the blank 100 during spinning. Simultaneously, the second ejector 302 is coaxially assembled to the pressing end of the spinning equipment, and the coaxiality error between the second ejector 302 and the mandrel 200 is controlled within a predetermined range. The pressing system is started, and the second ejector 302 is controlled to press against the non-forming end of the blank 100 at a preset feed speed, applying a pressing force to stabilize the blank 100. The axial positioning is then performed; subsequently, the rotation system of the spinning equipment is started, controlling the mandrel 200 to rotate at a preset speed, and the mandrel 200 drives the blank 100 to rotate synchronously; at the same time, the spinning wheel 500 frame is controlled to drive the spinning wheel 500 to start from the starting position of the first spherical section with a preset feed amount, and to perform multiple spinning along the spherical area of ​​the mandrel 200. The thinning amount of each spinning can be controlled within 0.1-0.3mm. The feed position of the spinning wheel 500 can also be monitored in real time by a displacement sensor to ensure that the thickness of the spherical area of ​​the blank 100 gradually approaches the design requirements after each spinning pass, until the thickness error of the spherical area of ​​the blank 100 is controlled within the required range after multiple spinning passes.

[0031] After the spherical area is formed, the rotation speed of the core mold 200 and the clamping force of the second ejector 302 are kept constant. The movement trajectory of the rotating wheel 500 is adjusted to control the rotating wheel 500 to smoothly transition from the spherical area of ​​the blank 100 to the cylindrical area. During the transition, the angle between the feed direction of the rotating wheel 500 and the axis of the core mold 200 is gradually adjusted from the angle that adapts to the spherical surface to 90° that adapts to the cylindrical surface, so as to avoid wrinkles or cracks in the blank 100 due to abrupt changes in trajectory. During the spinning process in the cylindrical area, the rotating wheel 500 is controlled to perform multiple spinning operations with a preset feed amount. The thinning amount of each spinning operation is controlled. The number of spinning passes is set according to the length of the cylindrical area. After each spinning pass, the thickness of the cylindrical area of ​​the blank 100 is detected by a laser thickness gauge to ensure that the thickness uniformity error does not exceed the preset range. After the thickness of the cylindrical area reaches the design requirements, the rotation system and the pressing system are turned off, and the feed of the rotating wheel 500 is stopped, resulting in a preliminary product whose shape is initially adapted to the surface of the core mold 200.

[0032] Finally, following the preset part removal process, a special fixture is used to remove the initial part from the core mold 200. During the part removal process, it is necessary to avoid hard collisions between the initial part and the core mold 200 to prevent deformation of the initial part or damage to the core mold 200. The end face allowance of the initial part is machined by cutting, and the finished product is surface cleaned and quality inspected.

[0033] In an optional embodiment, the forming method of this application is used for forming a combined variable wall thickness aluminum skin. The forming method involves first taking a variable wall thickness blank 100; preparing a core mold 200 and a first ejector 301 and a second ejector 302 according to forming requirements; coaxially assembling the core mold 200 to the rotating end of a spinning machine; coaxially assembling the first ejector 301 to the pressing end of the spinning machine; coaxially arranging the blank 100 between the core mold 200 and the first ejector 301; pressing a first spherical section onto the blank 100 using the first ejector 301; and then disassembling the first ejector 301; taking a spinning wheel 5... The blank 100 is assembled onto the spinning equipment. The second top piece 302 is coaxially assembled onto the pressing end of the spinning equipment. After the second top piece 302 is pressed onto the blank 100, the core mold 200 is rotated. The spinning wheel 500 performs multiple spinning operations on the spherical area of ​​the blank 100 from the first spherical section until the thickness of the spherical area of ​​the blank 100 reaches the required level. The spinning wheel 500 performs multiple spinning operations on the cylindrical area of ​​the blank 100 from the spherical area until the thickness of the cylindrical area of ​​the blank 100 reaches the required level, thus obtaining a preliminary product. The preliminary product is removed, and the end face allowance of the preliminary product is processed as required to obtain the finished product.

[0034] This forming method precisely solves the defects of existing technologies through staged, multi-pass spinning operations: In the spherical region forming stage, the first spherical segment is pre-pressed out using the first ejector 301, providing a stable initial profile for subsequent spinning by the spinning wheel 500, avoiding the force concentration when the spinning wheel 500 directly acts on the unformed blank 100; the rotation of the core mold 200 drives the blank 100 to rotate synchronously, and the spinning wheel 500 performs multiple spinning operations starting from the first spherical segment. Each spinning operation only achieves a small degree of material deformation and thinning. This multi-pass motion allows the material to flow evenly along the profile of the core mold 200 in the spherical region, effectively alleviating the problem of material accumulation in the transition area in traditional single-pass spinning, while also reducing the extrusion strength of the material in a single spinning operation and reducing the material flow resistance. During the cylindrical region forming stage, the spinning wheel 500 smoothly transitions from the already formed spherical region to the cylindrical region, continuing the multi-pass spinning motion logic. The core mold 200 rotates continuously and stably to ensure that the blank 100 is subjected to uniform force. The spinning wheel 500 gradually thins the cylindrical region, so that the material flow in the axial and radial directions remains coordinated, avoiding material flow difficulties caused by excessive single forming volume. Moreover, the multi-pass spinning disperses the axial tensile force, and the tensile stress generated by each pass is controlled within the material's bearing limit, completely solving the problem of cracks caused by excessive stress in the already thinned region.

[0035] This forming method employs a segmented forming strategy, separating the forming processes of spherical and cylindrical surfaces. By combining pre-pressed surfaces with multi-pass spinning, it achieves precise control over the forming process of complex-shaped parts. Furthermore, the coordinated positioning of the first ejector 301, the second ejector 302, and the core mold 200, along with the orderly planning of the spinning wheel 500's movement path, ensures the coaxiality and stability of the blank 100 during the forming process, guaranteeing dimensional accuracy control. Moreover, the multi-pass, small-deformation spinning method improves material flowability and reduces the risk of forming defects. Ultimately, this method enables high-quality forming of composite variable-wall-thickness aluminum skins, achieving dimensional accuracy that meets design drawing requirements. It significantly improves the part production pass rate and efficiency while ensuring the mechanical property stability of the formed parts, meeting the stringent requirements of related fields for fairing components.

[0036] In an optional implementation, when taking a blank 100 with variable wall thickness, the sheet is first processed into a round blank with variable wall thickness as required, and the thickness of the round blank increases uniformly from the center outward along the radial direction.

[0037] When taking a blank of 100 with variable wall thickness, first, according to the variable wall thickness distribution law required by the finished product and the material flow characteristics during the spinning process, the initial sheet is processed into a variable wall thickness round blank by a CNC milling machine or laser cutting equipment as required. The thickness of the round blank increases uniformly from the center outward along the radial direction. This thickness distribution is compatible with the subsequent spinning path of the spherical area from the center to the edge. The center corresponds to the top area of ​​the spherical segment. The material deformation in this area is small, and a thinner initial thickness can be reserved to reduce the processing amount of the subsequent thinning process. The radially outward area corresponds to the transition area from the spherical segment to the cylindrical segment. The material flow demand in this area is large. A thicker initial thickness can provide sufficient reserves for material replenishment during spinning, avoiding local depressions in the transition area due to insufficient material. At the same time, the uniformly increasing thickness change can ensure a smooth material stress distribution during spinning, reducing the risk of forming defects caused by sudden thickness changes.

[0038] In an optional embodiment, when taking a blank 100 with variable wall thickness, the processed blank 100 is sent to a heat treatment equipment for annealing. The annealing temperature is controlled at 350-360℃, the holding time is 150-200min, and the blank is air-cooled after the holding time is completed.

[0039] When taking a billet 100 with varying wall thickness, the processed billet 100 is sent to a box-type heat treatment furnace or a continuous annealing furnace for targeted annealing treatment. The annealing temperature is precisely controlled at 350-360℃, which is within the recrystallization temperature range of aluminum alloys. This effectively eliminates work hardening generated during the previous processing of the billet 100 (such as cutting and milling) and avoids excessively high temperatures that could lead to coarse grains and decreased mechanical properties. The holding time is set to 150-200 minutes to ensure uniform internal temperature of the billet 100. This process fully releases the internal stress within the material and allows the crystal structure to undergo a stable recrystallization transformation, thereby enhancing the material's plastic deformation capacity. After heat preservation, air cooling is employed. Compared to water or oil cooling, air cooling slows down the cooling rate, preventing the billet 100 from generating new internal stress due to excessive temperature differences. This ensures that the billet 100 is in a stable mechanical state before spinning, providing a guarantee for the smooth progress of subsequent multiple spinning passes. Especially for aluminum alloy grades with high hardness, the annealing process can increase the elongation of the material and significantly reduce the risk of spinning cracks.

[0040] In an optional implementation, when taking a blank 100 with variable wall thickness, an ultrasonic flaw detection device is used to test the blank 100. If a crack is detected in the blank 100, it is discarded, and the blank 100 is reprocessed and tested again until the test results meet the requirements.

[0041] When taking blank 100 with variable wall thickness, ultrasonic flaw detection equipment is used to perform full surface and internal quality inspection of blank 100. The inspection range covers the entire circular surface and thickness direction of blank 100, focusing on checking for defects such as pores, inclusions, and microcracks inside blank 100, as well as scratches or dents on the surface. Because blank 100 needs to withstand continuous extrusion and tensile stress during spin forming, if blank 100 itself has microcracks, the cracks will propagate rapidly under the spin forming force, eventually leading to the scrapping of the part. Therefore, once cracks or other defects exceeding the standard requirements are detected, blank 100 is immediately discarded, and qualified sheet metal is selected for processing and inspection until the inspection results meet the flaw detection requirements. This step can control the quality of blank 100 from the source, reduce the scrap rate of subsequent spin forming, and avoid abnormal equipment wear caused by defects in blank 100.

[0042] In an optional embodiment, the core mold 200 includes a main body 201, an end cap 202, and a stripper rod 203. One end of the main body 201 is provided with an mounting port for assembling the end cap 202. One end of the stripper rod 203 is connected to the end cap 202, and the other end passes through the main body 201 and extends to the other side of the main body 201. The stripper rod 203 can move axially and drive the end cap 202 to push out the initial product.

[0043] The main body 201 can be forged from a high-strength alloy and its hardness reaches the required level after heat treatment, ensuring that it can withstand the combined force of the spinning wheel 500 and the blank 100 without deformation during the spinning process. One end of the main body 201 is provided with an installation port for assembling the end cap 202. The inner wall of the installation port can be provided with a positioning step and a sealing groove. The end cap 202 is coaxially positioned with the main body 201 through the positioning step. A heat-resistant rubber ring can be embedded in the sealing groove to prevent lubricant or metal debris from entering the core mold 200 during the spinning process. The unloading rod 203 can be made of alloy material. One end of the unloading rod 203 is fixed to the end cap 202 by a threaded connection or a pin connection, and the other end passes through the through hole in the center of the main body 201 and extends to the other side of the main body 201. The inner wall of the through hole can be provided with a guide sleeve to ensure that the unloading rod 203 can move smoothly along the axial direction. After spinning is completed and a preliminary product is obtained, due to the tightness of the fit between the preliminary product and the outer surface of the core mold 200 (especially in the spherical area), direct disassembly can easily lead to deformation of the preliminary product. At this time, the extension end of the unloading rod 203 is pushed, and the unloading rod 203 drives the end cap 202 to move outward along the axis. The end cap 202 applies a uniform pushing force to the inner surface of the preliminary product, so that the preliminary product and the outer surface of the core mold 200 are gradually separated. Compared with the traditional manual prying method, this unloading structure can improve the disassembly efficiency of the preliminary product and avoid scratches or local deformation on the surface of the preliminary product caused by prying, ensuring that the shape accuracy of the preliminary product is not affected.

[0044] In an optional embodiment, when assembling the end cap 202, the transition between the end cap 202 and the outer spherical surface of the main body 201 is kept smooth, and the circular runout of the spinning surface on the spinning wheel 500, the cylindrical surface of the core mold 200, and the spherical surface of the core mold 200 is checked to ensure that they meet the requirements.

[0045] When assembling the end cap 202, the end cap 202 is first pre-assembled with the mounting port of the main body 201. The transition area between the outer spherical surface of the end cap 202 and the outer spherical surface of the main body 201 is detected by a dial indicator to ensure that the surface roughness at the transition does not exceed the preset range and the center deviation of the transition arc is controlled within the preset range, so as to achieve a smooth transition between the outer spherical surfaces of the two. This transition area corresponds to the connection part between the spherical section and the cylindrical section. If there are steps or unevenness here, it will cause stress concentration in the blank 100 during spinning, which will then produce wrinkles or cracks.

[0046] Simultaneously, a circular runout detector is used to detect the circular runout of the spinning surface on the spinning wheel 500, the cylindrical surface of the mandrel 200, and the spherical surface of the mandrel 200. This controls the circular runout error of the spinning surface of the spinning wheel 500, preventing ripples on the surface of the blank 100 due to eccentricity of the spinning wheel 500 during spinning; it also controls the circular runout error of the cylindrical surface of the mandrel 200, ensuring the uniformity of wall thickness after spinning in the cylindrical area; and it controls the circular runout error of the spherical surface of the mandrel 200, ensuring the forming accuracy of the spherical area. All tests must be performed after the mandrel 200 and spinning wheel 500 are assembled and before the blank 100 is installed. If the test results exceed the allowable range, calibration must be performed by adjusting the fixing bolts of the mandrel 200 or the tool holder position of the spinning wheel 500 until the parameters meet the requirements, providing a reliable foundation for high-precision subsequent spinning forming.

[0047] In an optional embodiment, before the first spherical section performs multiple spins on the spherical area of ​​the blank 100, the position of the spinning wheel 500 is adjusted so that there is a first gap 401 between the spinning wheel 500 and the spherical surface of the core mold 200. Before the spherical region of the blank 100 is repeatedly spun from the spherical region to the cylindrical region of the blank 100, the position of the spun wheel 500 is adjusted so that there is a second gap 402 between the spun wheel 500 and the cylindrical surface of the core mold 200, wherein the first gap 401 is larger than the second gap 402.

[0048] In an optional embodiment, before the first spherical section performs multiple spins on the spherical region of the blank 100, the position of the spinning wheel 500 is adjusted by the CNC system of the spinning equipment according to the initial thickness of the blank 100 and the target thickness of the spherical region. This ensures that there is a first gap 401 between the spinning wheel 500 and the spherical surface of the mandrel 200. The first gap 401 ensures that when the spinning wheel 500 first contacts the blank 100, it only applies a moderate squeezing force to the blank 100, pushing the material to conform to the spherical surface, rather than directly thinning it significantly, thus avoiding excessive local deformation of the blank 100 due to an excessively small initial gap. Before the spherical region of the blank 100 is spun multiple times in the cylindrical region of the blank 100, the position of the spinning wheel 500 is adjusted according to the initial thickness and target thickness of the cylindrical region so that there is a second gap 402 between the spinning wheel 500 and the cylindrical surface of the mandrel 200, and the first gap 401 is larger than the second gap 402. This is because the spinning of the cylindrical region is mainly axial thinning, and the material flow direction is more singular. A smaller initial gap can improve the spinning efficiency of the cylindrical region. At the same time, the cylindrical region has no complex curvature changes, and a smaller gap will not cause stress concentration. This differentiated gap arrangement can achieve precise matching of the spinning process of the spherical and cylindrical regions, taking into account both forming quality and efficiency.

[0049] In an optional embodiment, when the spinning wheel 500 repeatedly spins the spherical area of ​​the blank 100, the spinning wheel 500 is first operated to repeatedly apply force to the blank 100 until the blank 100 adheres to the spherical area of ​​the core mold 200, and then the spinning wheel 500 is operated to repeatedly apply force to the blank 100 until the blank 100 is reduced to the required thickness.

[0050] When the spinning wheel 500 repeatedly spins the spherical area of ​​the blank 100, it first applies force to the blank 100 repeatedly with a lower feed pressure and a slower feed speed. The core objective of this stage is to push the blank 100 to gradually fit into the spherical area of ​​the mandrel 200. Through repeated light pressure, the inner surface of the blank 100 is made to fit completely into the outer surface of the mandrel 200, eliminating the gap between the blank 100 and the mandrel 200 and ensuring the thickness uniformity of the subsequent thinning process. After the molding is completed, the feed pressure of the spinning wheel 500 is increased and the feed speed is adjusted to repeatedly apply force to the blank 100. In this stage, the thickness of the blank 100 is precisely reduced by gradually increasing the extrusion intensity. The amount of thinning is controlled within a preset range each time until the thickness of the blank 100 is reduced to the design requirements. This operation method avoids the local thickness deviation caused by the blank 100 not being fully coated with the mold when the coating and thinning are carried out simultaneously in the traditional operation. If the thinning is carried out first and then the coating is coated, the thinned area may undergo secondary deformation due to the extrusion effect of the subsequent coating.

[0051] In an optional embodiment, the contact area between the first top member 301 and the blank 100 is greater than the contact area between the second top member 302 and the blank 100. Two rotating wheels 500 are arranged, each of which has rounded corners and is symmetrically arranged on both sides of the core mold 200.

[0052] The contact area between the first top member 301 and the blank 100 is greater than the contact area between the second top member 302 and the blank 100. This is because the function of the first top member 301 is to press out the first spherical segment on the blank 100. The larger contact area can make the pressing force evenly distributed in the spherical pre-forming area of ​​the blank 100, avoiding excessive local pressure that could cause the blank 100 to dent or crack, while ensuring the surface accuracy of the first spherical segment.

[0053] The second top piece 302 only needs to provide axial support for the non-formed end of the blank 100 to prevent the blank 100 from moving axially during spinning. The smaller contact area can reduce the contact friction between the top piece and the blank 100, reduce the risk of surface damage to the non-formed end of the blank 100, and at the same time facilitate the adjustment of the clamping force. In addition, two spinning wheels 500 are arranged symmetrically on the spinning wheel 500 frame of the spinning equipment and symmetrically arranged on both sides of the mandrel 200. Each spinning wheel 500 has rounded corners, which can prevent the edge of the spinning wheel 500 from scratching the surface of the blank 100 and reduce the stress concentration between the spinning wheel 500 and the blank 100. The symmetrically arranged double spinning wheels 500 can apply equal and opposite extrusion forces to the blank 100 from both sides of the mandrel 200 during spinning, so that the radial resultant forces on the blank 100 cancel each other out, avoiding eccentric deformation of the blank 100 caused by unilateral force. At the same time, the double spinning wheels 500 can perform spinning operations simultaneously, shortening the spinning time of the spherical area and the cylindrical area, improving production efficiency, and significantly improving forming stability.

[0054] In an optional embodiment, after removing the initial product, the initial product is sent to a heat treatment device for annealing. The annealing temperature is controlled at 350-360℃, and the holding time is 150-200 minutes. After the holding time is completed, the initial product is air-cooled, and then the end face allowance of the initial product is machined until the end face size and flatness of the initial product meet the requirements.

[0055] After removing the initial product, considering that the initial product will undergo new work hardening during multiple spinning processes, resulting in increased material hardness and decreased plasticity, if the end face is directly cut, it is easy to cause problems such as excessive tool wear and excessive surface roughness. Therefore, the initial product is first sent to a heat treatment device for secondary annealing. The annealing temperature is also controlled at 350-360℃, and the holding time is 150-200min. These process parameters match the annealing process of the pre-treated billet 100, which can ensure that the internal stress of the initial product is fully released and that the material restores good machinability. After the holding time is completed, air cooling is used to avoid deformation of the initial product due to excessive cooling rate.

[0056] After annealing, the initial part is clamped on the three-jaw chuck of a CNC lathe. The coaxiality of the initial part is corrected by a dial indicator. Then, the end face allowance of the initial part is cut by high-speed steel tools or carbide tools. During the machining process, the end face size is monitored in real time by a laser diameter gauge until the end face size error of the initial part is controlled within the preset range and the flatness error does not exceed the preset range. At the same time, the surface roughness of the machined end face can meet the accuracy requirements of subsequent assembly.

[0057] It should be understood that the terms "first," "second," etc., are used only for distinguishing descriptions and should not be construed as indicating or implying relative importance. Although the terms "first," "second," etc., may be used herein to describe various units, these units should not be limited by these terms. These terms are only used to distinguish one unit from another. For example, a first unit may be referred to as a second unit, and similarly, a second unit may be referred to as a first unit, without departing from the scope of the exemplary embodiments of the invention.

[0058] It should be understood that the term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists alone, B exists alone, and A and B exist simultaneously. The term " / and" in this article describes another relationship between related objects, indicating that two relationships can exist. For example, A / and B can mean: A exists alone, and A and B exist alone. In addition, the character " / " in this article generally indicates that the related objects before and after it are in an "or" relationship.

[0059] It should be understood that in the description of this invention, the terms "upper," "vertical," "inner," "outer," etc., indicate the orientation or positional relationship as commonly placed when the disclosed product is used, or the orientation or positional relationship commonly understood by those skilled in the art. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0060] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," and "connect" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0061] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments of the invention. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising,” “including,” “containing,” and / or “including” as used herein specify the presence of the stated features, integers, steps, operations, units, and / or components, and do not exclude the presence or addition of one or more other features, quantities, steps, operations, units, components, and / or combinations thereof.

[0062] Specific details are provided in the following description to provide a complete understanding of the exemplary embodiments. However, those skilled in the art will understand that the exemplary embodiments can be implemented without these specific details. In other embodiments, well-known processes, structures, and techniques may be omitted in the depiction of non-essential details to avoid obscuring the exemplary embodiments.

[0063] The above are merely specific embodiments of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

[0064] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art.

Claims

1. A method for forming a combined variable wall thickness aluminum skin, characterized in that, The forming method includes: Select blanks with varying wall thickness; Prepare a core mold, a first ejector, and a second ejector according to molding requirements. The core mold is coaxially assembled to the rotating end of the spinning equipment. The first top piece is coaxially assembled to the pressing end of the spinning equipment. The blank is coaxially arranged between the core mold and the first top piece. After pressing the first spherical section onto the blank using the first top piece, the first top piece is disassembled. The spinning wheel is assembled onto the spinning equipment, and the second top piece is coaxially assembled onto the pressing end of the spinning equipment. After the second top piece is pressed onto the blank, the core mold is rotated, and at the same time, the spinning wheel is operated to spin the spherical area of ​​the blank from the first spherical section to the cylindrical section until the thickness of the spherical area of ​​the blank reaches the design requirements. The spinning wheel is operated from the spherical region of the billet to the cylindrical region of the billet, and spins the billet in the cylindrical region until the thickness of the cylindrical region of the billet reaches the required level, thus obtaining the initial product; Remove the initial product and process the end face allowance of the initial product as required to obtain the finished product.

2. The forming method of the combined variable wall thickness aluminum skin as described in claim 1, characterized in that: When taking blanks with variable wall thickness, first process the sheet material into a round blank with variable wall thickness as required, and the thickness of the round blank increases uniformly from the center outward along the radial direction.

3. The forming method of the combined variable wall thickness aluminum skin as described in claim 1, characterized in that: When taking blanks with variable wall thickness, the processed blanks are sent to heat treatment equipment for annealing. The annealing temperature is controlled at 350-360℃, the holding time is 150-200min, and the blanks are air-cooled after the holding time is completed.

4. The forming method of the combined variable wall thickness aluminum skin as described in claim 1, characterized in that: When taking blanks with varying wall thickness, ultrasonic testing equipment is used to inspect the blanks. If cracks are detected, the blanks are discarded and reprocessed for inspection until the test results meet the requirements.

5. The forming method of the combined variable wall thickness aluminum skin as described in claim 1, characterized in that: The core mold includes a main body, an end cap, and a stripper rod. One end of the main body is provided with an mounting port for assembling the end cap. One end of the stripper rod is connected to the end cap, and the other end passes through the main body and extends to the other side of the main body. The stripper rod can move axially and drive the end cap to push out the initial product.

6. The forming method of the combined variable wall thickness aluminum skin as described in claim 5, characterized in that: When assembling the end cap, ensure a smooth transition between the end cap and the outer spherical surface of the main body, and check that the circular runout of the spinning surface on the spinning wheel, the cylindrical surface of the core mold, and the spherical surface of the core mold meets the requirements.

7. The forming method of the combined variable wall thickness aluminum skin as described in claim 1, characterized in that: Before the first spherical section spins the blank multiple times in the spherical area, the position of the spinning wheel is adjusted so that there is a first gap between the spinning wheel and the spherical surface of the mandrel. Before the spinning wheel is repeatedly spun from the spherical region of the blank to the cylindrical region of the blank, the position of the spinning wheel is adjusted so that there is a second gap between the spinning wheel and the cylindrical surface of the mandrel, and the first gap is larger than the second gap.

8. The forming method of the combined variable wall thickness aluminum skin as described in claim 1, characterized in that: When the spinning wheel repeatedly spins the blank in the spherical area, first operate the spinning wheel to repeatedly apply force to the blank until the blank fits into the spherical area of ​​the mandrel, then operate the spinning wheel to repeatedly apply force to the blank until the blank is reduced to the required thickness.

9. The forming method of the combined variable wall thickness aluminum skin as described in claim 1, characterized in that: The contact area between the first top piece and the blank is greater than the contact area between the second top piece and the blank. There are two rotating wheels, each with rounded corners, and they are symmetrically arranged on both sides of the core mold.

10. The forming method of the combined variable wall thickness aluminum skin as described in claim 1, characterized in that: After removing the initial product, the initial product is sent to a heat treatment device for annealing. The annealing temperature is controlled at 350-360℃ and the holding time is 150-200 minutes. After the holding time is completed, the initial product is air-cooled. Then, the end face allowance of the initial product is machined until the end face size and flatness of the initial product meet the requirements.

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