A machining method for an inner boss annular sheet part

Abstract

The present application relates to the technical field of aircraft sheet metal part processing, and particularly relates to a processing method of an inner boss annular sheet part, which comprises the following steps: selecting a metal sheet material meeting the material quality requirement of the part; cutting and blanking the sheet material according to the specification; obtaining a sheet material blank with a preset size through numerical control milling; cleaning the surface of the sheet material blank; clamping the pretreated sheet material blank to a three-axis roll bending machine; calculating and adjusting the upper roller shaft pressure H of the three-axis roll bending machine; performing a multi-pass gradual roll bending process to form an annular blank with a preset curvature; and placing the roll-bent annular blank into an expansion die, introducing high-pressure gas, and making the annular blank adhere to the cavity of the expansion die to form an inner boss, thus achieving the precise forming of the inner boss and the annular outer contour at one time. The present application avoids cracks and defects in roll bending forming, maximizes the use of materials, reduces waste, and realizes the efficient and accurate manufacturing of the inner boss annular aluminum alloy sheet part.

Description

Technical Field

[0001] This invention relates to the field of sheet metal parts processing technology for aircraft. Background Technology

[0002] With the rapid development of the aviation industry, the demand for high-performance aerospace components is increasing. These components typically require high strength, lightweight, and complex geometries to meet the performance requirements of aircraft in extreme environments. Aluminum alloys, due to their excellent strength-to-weight ratio and good machinability, have become an important material in the aerospace field. However, annular aluminum alloy sheet components with internal boss structures are widely used in many industrial sectors due to their lightweight, high structural strength, and excellent space utilization. Currently, the main processing methods for such components include casting and forging followed by machining. However, existing processing methods have many shortcomings. Traditional processing methods often struggle to simultaneously meet the requirements of high precision, high strength, and complex geometries. These components are typically used in critical parts of aircraft engines or fuselages, and their complex geometries, including inner and outer annular surfaces and a central internal boss structure, pose a significant challenge to the machining process.

[0003] Traditional machining methods primarily rely on techniques such as machine milling and stamping. However, these methods are prone to deformation when processing thin sheet materials, especially when forming internal boss structures requiring high-precision control. Furthermore, traditional casting or forging processes may not completely eliminate internal defects such as porosity or cracks, which can affect the fatigue strength and reliability of parts. In recent years, while modern manufacturing technologies such as laser cutting and precision stamping have improved processing efficiency and accuracy in some aspects, they still face many limitations when processing annular internal boss structures. For example, deformation control of thin sheet materials remains a significant challenge, and the high-precision forming of complex structures requires even more precise process control.

[0004] Therefore, inventing a highly efficient and precise machining method capable of accurately forming annular aluminum alloy sheet parts with internal bosses while maintaining material properties has become a critical issue urgently needing to be addressed in the aerospace manufacturing field. This new method can not only improve the performance and reliability of parts but also significantly increase production efficiency and reduce costs, which is of great significance to promoting the development of the aerospace industry. Summary of the Invention

[0005] The purpose of this invention is to provide a process method for making an inner boss annular aluminum alloy sheet part by combining roll bending with air expansion, so as to solve the problems of difficulty in accurately forming complex three-dimensional curved surface structures, low material utilization and insufficient mechanical properties in traditional manufacturing processes. To achieve the above objectives, the technical solution of the present invention is as follows: a method for processing an annular thin plate part with an inner boss, the specific steps of which are as follows: Step 1: Select metal sheet material that meets the requirements of the part material, cut the sheet material according to the specifications, and CNC mill it to obtain a blank of the preset size. Clean the oil and oxide scale from the surface of the blank. Step 2: Clamp the pre-treated sheet blank into the three-axis roll bending machine, calculate and adjust the upper roller shaft pressing amount H of the three-axis roll bending machine, and perform a multi-pass progressive roll bending process to form a ring blank with a preset curvature. Step 3: Place the rolled and bent annular blank into the bulging mold, and introduce high-pressure gas to make the annular blank fit the cavity of the bulging mold and form an inner boss, thus completing the precise forming of the inner boss and the outer contour of the annular shape in one go.

[0006] Furthermore, in step one, the cutting and blanking process involves using aerospace sheet metal design software to unfold the three-dimensional model of the inner boss ring part into a two-dimensional planar outline. Then, a two-axis CNC milling machine and a tool with a diameter of 4-6mm are used to precision mill the two-dimensional planar outline. This allows for the completion of internal and external machining without tool changes, making it easier to machine the inner hole of the part, thereby obtaining a sheet blank that meets the dimensional accuracy requirements.

[0007] Furthermore, in step two, the calculation formula for adjusting the upper roller shaft pressing amount H is as follows: , In the formula, Rq is the bending radius of the inner surface of the annular thin plate part before springback; Rz is the radius of the lower roller shaft; t is the material thickness; and a is half of the horizontal center distance between the two lower roller shafts of the three-axis roll bending machine.

[0008] Furthermore, in step two, the multi-pass progressive roll bending process specifically includes: Each pass involves pre-bending the annular blank to a radius 1.0 to 1.1 times larger than the preset curvature radius, followed by bending at 1.1 to 1.2 times the upper roller pressing amount H to form a preliminary profile. Then, gradually reduce the bending radius to 0.9 to 1.0 times the bending radius Rq of the inner surface of the sheet blank before springback, that is, roll bending to obtain a cylindrical annular blank with unclosed joints; Meanwhile, diameter is checked after each rolling bend to correct roundness and flatness, ensuring that the outer contour of the annular billet meets the subsequent bulging reference requirements and ultimately achieves the preset curvature radius of curvature of the annular billet.

[0009] Furthermore, in step three, the bulging mold includes a lower mold and an upper mold; The lower mold is a cylindrical structure mold with a cylindrical mounting cavity. Multiple through-holes are evenly opened on the circumferential surface of the circular bottom of the lower mold to discharge residual gas in the forming process. The upper mold with a central hole is coaxial and installed in the cylindrical mounting cavity of the lower mold by connecting bolts. The upper mold and the lower mold together form a forming cavity that matches the outer contour of the annular thin plate part with the inner boss. The plug is installed in the center hole of the upper mold. Sealing grooves are opened at both ends of the plug in the circumferential direction. Upper sealing ring and lower sealing ring are installed in the sealing grooves respectively for radial sealing and leakage prevention during the inflation process. A circumferential air guide groove is provided on the outer wall of the plug core located between the upper and lower sealing rings; an air outlet connected to the forming cavity is provided on the wall of the air guide groove. The pressure cap is fixed to the plug core with fasteners, and the air inlet pipe passes through the through hole on the pressure cap to connect to an external high-pressure air source.

[0010] Furthermore, the lower mold is made of cold work die steel; the number of vent holes in the lower mold is 4 to 6. Too many vent holes in the lower mold will affect the strength of the mold, while too few vent holes in the lower mold will affect the application of film to the parts.

[0011] Furthermore, a through-hole is provided at the central axis of the plug core to quickly release the high-pressure gas inside the mold after molding and to ensure uniform release.

[0012] Furthermore, a through hole is opened in the center of the clamping cover, and the air inlet pipe is screwed into the through hole and coaxially connected with the exhaust hole of the plug core, for connecting an external high-pressure air source and delivering forming pressure into the mold.

[0013] Furthermore, the method of using the bulging mold is as follows: First, fix the upper mold to the cylindrical mounting cavity of the lower mold to complete the positioning and locking of the upper and lower molds; then, install the upper and lower sealing rings into the sealing grooves at both ends of the plug core, and finally, coaxially install the plug core into the center hole of the upper mold and position it. Then, the rolled annular blank is placed into the forming cavity from top to bottom along the outer wall of the plug core, so that the lower end of the annular blank is stably attached to the positioning surface of the end of the plug core, ensuring that the blank is coaxial with the forming cavity and without offset. Next, press the clamping cap onto the plug core and tighten it evenly with screws to ensure the overall sealing of the mold; introduce high-pressure gas through the air inlet pipe to force the outer wall of the blank to fit tightly against the inner wall of the upper and lower mold cavities, and complete the precise forming of the inner boss and outer ring contour of the boss ring thin plate part in one go. Hold the pressure for 3 to 5 minutes to ensure the stability of the boss shape and the accuracy of the dimensions. Finally, after the forming process is completed, the high-pressure gas in the forming cavity is released through the core-plugging vent hole, and the residual gas is discharged from the forming cavity through the lower mold vent hole. After the pressure is completely released, the upper and lower mold connecting bolts are loosened and the mold is separated. The formed inner boss ring aluminum alloy sheet part is taken out from the bulging mold, and the processing is completed.

[0014] Furthermore, the annular thin plate part with the boss is made of aluminum alloy; the pressure value of the high-pressure gas is greater than 10% of the yield strength of the aluminum alloy material, ensuring that the air pressure can compress the plate and force it to stretch.

[0015] The beneficial effects of this invention are: by combining pre-roll bending forming technology with pneumatic bulging post-processing, the dimensional accuracy of the parts is improved, and the overall processing time is shortened. Roll bending forming allows for precise control of the roundness and flatness of the annular structure, ensuring that the outer contour meets design requirements and reducing cutting waste. Subsequent pneumatic bulging optimizes the complex shape of the inner boss portion, reduces dimensional deviations, and overcomes potential local scratches or deformations that might occur with roll bending forming. This ensures the smoothness of the internal structure, avoids cracks and defects, maximizes material utilization, reduces waste, and achieves efficient and precise manufacturing of annular aluminum alloy sheet parts with inner bosses. Attached Figure Description

[0016] Figure 1 This is a drawing of the annular aluminum alloy sheet part with an inner boss according to the present invention; Figure 2 This is a diagram showing the relationship between the upper roller shaft pressing amount; Figure 3 This is a diagram of the bulging mold involved in the present invention; Figure 4 This is a structural diagram of the lower mold and plug installation of the bulging mold of the present invention; Figure 5 This is a diagram showing the core mounting structure of the bulging mold of the present invention; Figure 6 This is a top view of the lower mold of the bulging mold of the present invention.

[0017] In the diagram: 1-lower mold, 2-upper mold, 3-lower mold vent hole, 4-plug, 5-lower sealing ring, 6-upper sealing ring, 7-air outlet, 8-air guide groove, 9-pressure cover, 10-air inlet pipe, 11-forming cavity. Detailed Implementation

[0018] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0019] To achieve the above objectives, the present invention provides the following specific embodiments: Example 1: As Figure 1-6 As shown, a machining method for an annular thin plate part with an inner boss includes the following specific steps: Step 1: Select metal sheet material that meets the requirements of the part material, cut the sheet material according to the specifications, and CNC mill it to obtain a blank of the preset size. Clean the oil and oxide scale from the surface of the blank. The cutting and blanking process involves using aerospace sheet metal design software to unfold the three-dimensional model of the inner boss ring part into a two-dimensional planar outline. Then, a two-axis CNC milling machine and a tool with a diameter of 4-6mm are used to precision mill the two-dimensional planar outline. This allows for the completion of internal and external machining without tool changes, making it easier to machine the internal holes of the part and thus obtaining a sheet blank that meets the dimensional accuracy requirements.

[0020] Step 2: Clamp the pre-treated sheet metal blank onto the three-axis roll bending machine, such as... Figure 2 The diagram showing the relationship between the upper roller reduction of the three-axis roll bending machine is used to calculate and adjust the upper roller reduction H. The formula for calculating the upper roller reduction H is as follows: , In the formula, Rq is the bending radius of the inner surface of the annular thin plate part before springback; Rz is the radius of the lower roller shaft; t is the material thickness; and a is half of the horizontal center distance between the two lower roller shafts of the three-axis roll bending machine. Afterwards, a multi-pass progressive rolling bending process is performed to form a ring-shaped blank with a preset curvature; The multi-pass progressive roll bending process specifically includes: Each pass involves pre-bending the annular blank to a radius 1.0 to 1.1 times larger than the preset curvature radius, followed by bending at 1.1 to 1.2 times the upper roller pressing amount H to form a preliminary profile. Then, gradually reduce the bending radius to 0.9 to 1.0 times the bending radius Rq of the inner surface of the sheet blank before springback, that is, roll bending to obtain a cylindrical annular blank with unclosed joints; Meanwhile, diameter is checked after each rolling bend to correct roundness and flatness, ensuring that the outer contour of the annular billet meets the subsequent bulging reference requirements and ultimately achieves the preset curvature radius of curvature of the annular billet.

[0021] Step 3: Place the rolled and bent annular blank into the bulging mold, and introduce high-pressure gas to make the annular blank fit the cavity of the bulging mold and form an inner boss, thus completing the precise forming of the inner boss and the outer contour of the annular shape in one go. Among them, such as Figures 3-6 As shown in the figure, the bulging mold includes a lower mold 1 and an upper mold 2; The lower mold 1 is a cylindrical structure mold with a cylindrical mounting cavity. Multiple through lower mold vent holes 3 are evenly opened on the circumferential direction of the circular bottom surface of the lower mold 1 to discharge residual gas in the forming process inside the mold. The upper mold 2, which has a central hole, is coaxial and installed in the cylindrical mounting cavity of the lower mold 1 by connecting bolts. The upper mold 2 and the lower mold 1 together form a forming cavity 11 that matches the outer contour of the inner boss annular thin plate part. The plug core 4 is installed in the center hole of the upper mold 2. The plug core 4 has sealing grooves at both ends of its circumference. The upper sealing ring 6 and the lower sealing ring 5 are installed in the sealing grooves to provide radial sealing and prevent leakage during the inflation process. A gas guide groove 8 is provided circumferentially on the outer wall of the plug core 4 located between the upper sealing ring 6 and the lower sealing ring 5; an air outlet 7 is provided on the groove wall of the gas guide groove 8, which is connected to the forming cavity 11. The compression cap 9 is fixed to the plug core 4 by fasteners, and the air inlet pipe 10 passes through the through hole on the compression cap 9 to connect to an external high-pressure air source. The lower mold 1 is made of cold work die steel; the number of vent holes 3 in the lower mold is 4 to 6. Too many vent holes 3 in the lower mold will affect the strength of the mold, and too few vent holes 3 in the lower mold will affect the film application of the parts. A through-hole is opened at the central axis of the plug core 4 to quickly release the high-pressure gas in the mold after molding and to ensure uniform release. A through hole is opened in the center of the pressure cap 9, and the air inlet pipe 10 is screwed into the through hole and coaxially connected with the exhaust hole of the plug core, which is used to connect an external high-pressure air source and deliver forming pressure into the mold. The method of using the bulging mold is as follows: First, fix the upper mold 2 to the cylindrical mounting cavity of the lower mold 1 to complete the positioning and locking of the upper and lower molds; then install the upper sealing ring 6 and the lower sealing ring 5 into the sealing grooves at both ends of the plug core 4, and then coaxially install the plug core 4 into the center hole of the upper mold 2 and position it. Then, the rolled annular blank is placed into the forming cavity 11 from top to bottom along the outer wall of the plug core 4, so that the lower end of the annular blank is stably attached to the positioning surface of the end of the plug core 4, ensuring that the blank is coaxial with the forming cavity 11 without offset. Next, press the clamping cap 9 onto the plug core 4 and tighten it evenly with screws to ensure the overall sealing of the mold; introduce high-pressure gas through the air inlet pipe 10 to force the outer wall of the blank to fit tightly against the inner wall of the upper and lower mold cavities, and complete the precise forming of the inner boss and outer ring contour of the boss ring thin plate part in one go. Hold the pressure for 3 to 5 minutes to ensure the stability of the boss shape and the accuracy of the dimensions. Finally, after the forming is completed, the high-pressure gas in the forming cavity 11 is released through the core-plugging vent hole. The residual gas is discharged from the forming cavity 11 through the lower mold vent hole 3. After the pressure is completely released, the upper and lower mold connecting bolts are loosened and the mold is separated. The formed inner boss annular aluminum alloy sheet part is taken out from the bulging mold, and the processing is completed.

[0022] like Figure 1 As shown, the annular thin plate part with the boss is made of aluminum alloy; the pressure value of the high-pressure gas is greater than 10% of the yield strength of the aluminum alloy material, ensuring that the air pressure can compress the plate and force it to stretch.

[0023] To further illustrate the technical solution and technical effects of the present invention, the following specific examples are provided: A ring-shaped aluminum alloy sheet part with an inner boss is produced by a process combining roll bending and pneumatic expansion to solve the problems of difficulty in accurately forming complex three-dimensional curved surface structures, low material utilization, and insufficient mechanical properties in traditional manufacturing processes.

[0024] The method combines roll forming with pneumatic bulging to achieve efficient and high-precision manufacturing of annular aluminum alloy sheet parts with internal bosses, while optimizing the stress distribution and fatigue performance of the parts, thus meeting the aerospace industry's demand for lightweight and high-performance parts.

[0025] To achieve the above objectives, the processing method of the present invention mainly includes the following steps: Sheet metal pretreatment: Select aluminum alloy sheet metal that meets the material requirements of the part, cut the sheet metal, and before the cutting process, use software commonly used in the aerospace manufacturing industry to unfold the three-dimensional part into a two-dimensional state, and then use a two-axis CNC milling machine to CNC mill the shape to obtain a sheet metal blank of the preset size; then the sheet metal blank is surface treated to remove surface oil, oxide scale and other impurities to ensure that the sheet metal surface is clean and to avoid impurities affecting the forming quality during subsequent processing.

[0026] During CNC milling, the aluminum alloy sheet material is fixed on the fixture of the milling machine to ensure that the material is stable and vibration-free during the machining process; based on the two-dimensional unfolded data, the part shape is precision machined using a Φ6mm diameter tool to ensure that the dimensional accuracy meets the design requirements.

[0027] Roll forming: The pre-treated sheet blank is placed in the roller bed. The roller spacing and speed of the roller bed are adjusted according to the outer diameter of the annular part. The roller bed is started, and the sheet blank gradually undergoes plastic deformation under the extrusion and drive of the rollers to form a circular sheet blank with a preset curvature (i.e., a preliminary annular structure. At this time, the interface of the annular structure is not closed, and only an approximately circular cylindrical structure is formed). During the roll bending process, the curvature and roundness of the circular sheet blank are monitored in real time. A steel tape measure can be used to measure the diameter during the roll bending process to ensure that the formed circular sheet blank meets the requirements of subsequent bulging processing.

[0028] Adjust the bending radius, angle, and roller spacing of the roll bending machine according to the design shape and size of the part.

[0029] When the sheet metal is bent in a triaxial motion, the amount of pressure applied by the upper roller can be determined according to formula (1), such as... Figure 2 As shown.

[0030] , In the formula: H — Upper roller shaft pressing amount, in millimeters (mm). Rq—Bending radius of the inner surface of the part before springback, in millimeters (mm). Rz — Radius of the lower roller shaft, in millimeters (mm). t — Material thickness, in millimeters (mm); a——Half of the horizontal center distance of the lower roller shaft, in millimeters (mm).

[0031] Finishing: Place the round sheet blank after roll bending into a special bulging mold, adjust the position of the round sheet blank in the mold to ensure that the sheet blank is aligned with the positioning structure of the mold; then close the mold to make the upper mold, lower mold and side mold tightly closed to form a closed forming cavity, while ensuring that the sealing structure of the mold is tightly fitted with the round sheet blank to prevent gas leakage during subsequent inflation.

[0032] Specifically, this includes transferring the milled aluminum alloy sheet to a roll bending machine, adjusting the bending radius, angle, and roller spacing of the roll bending machine according to the design shape and size of the part; using a multi-pass bending method, starting with small angles and gradually increasing the angle, to gradually bend the aluminum alloy sheet into a circular structure. After each bending pass, the shape of the part is checked to ensure it meets the design requirements, and adjustments are made according to the formula for the upper roller reduction; after roll bending is completed, the inner and outer contours of the part are corrected and shaped to ensure no deformation or deviation.

[0033] Inflatable forming: To achieve the above-mentioned inflatable forming process, this invention designs a forming mold. The mold is specifically designed for annular aluminum alloy sheet parts with internal bosses of different sizes and wall thicknesses, as follows: Structural components: including lower mold 1, upper mold 2, lower mold vent 3, plug 4, lower sealing ring 5, upper sealing ring 6, air outlet 7, air guide groove 8, pressure cover 9, air inlet pipe 10, and plug vent 11.

[0034] The lower mold 1 serves as the base of the mold, made of cold-work die steel. The upper mold 2 is connected to the lower mold 1 via bolts to ensure strength. Four air vents 3 are formed on the bottom surface of the lower mold 1 to vent residual gas from the mold during part forming, preventing reverse forces that could cause incomplete forming. After the lower mold 1 and upper mold 2 are connected, a plug 4 is placed into the upper mold 2. Sealing grooves are formed at the top and bottom of the plug 4, housing an upper sealing ring 6 and a lower sealing ring 5. A guide groove 8 is formed between the upper and lower sealing rings 6 and 5, with an outlet 7 inside the guide groove 8 to introduce external high-pressure gas into the mold for part forming. A vent 11 is machined at the bottom of the plug 4. The vent 11 allows the high-pressure gas injected into the original mold to escape smoothly after the lower mold 1 is removed, reducing gas pressure on the part and facilitating its removal.

[0035] After the lower mold 1, upper mold 2 and plug 4 are installed, a pressure cap 9 is installed on the plug 4 and tightened with hexagonal screws. Then, an air inlet pipe 10 is inserted into the center of the plug 4 and tightened. Its function is to connect with external high-pressure gas.

[0036] It also includes fixing the upper mold 2 on the upper surface of the lower mold 1 to ensure accurate positioning between the upper and lower molds; installing the upper sealing ring 6 and the lower sealing ring 5 on the upper and lower ends of the plug core 4 respectively to ensure that gas will not leak during the subsequent inflation and expansion process; and placing the plug core 4 with the sealing rings installed into the upper mold 2 and fixing it to ensure a stable and reliable connection between the plug core and the mold.

[0037] Then, the annular aluminum alloy sheet material, which has been rolled and formed, is placed into the mold along the upper edge of the plug core 4, and the lower end of the sheet material is stably fixed at the lower end position of the plug core 4.

[0038] The specific process involves placing the clamping cap 9 above the plug core 4 and tightening it with hexagonal screws to ensure the sealing of the mold interior; connecting an external high-pressure gas source through the air inlet pipe 10 and adjusting the gas pressure parameters, which should be set according to the different grades and thicknesses of the aluminum alloy sheet, with the force value exceeding 10% of the material's yield strength; opening the air inlet valve to inject high-pressure gas into the mold. After entering the mold, the gas acts on the inner surface of the aluminum alloy sheet; under the action of the high-pressure gas, the inner surface of the aluminum alloy sheet is subjected to uniform pressure, forcing the sheet to tightly adhere to the inner surfaces of the lower mold 1 and the upper mold 2, thereby completing the forming process of the boss on the annular part. Venting and Pressure Holding: The original air inside the mold enters the bottom of the lower mold through the vent hole 11 and is finally discharged to the outside of the mold through the vent hole 3 of the lower mold, thereby ensuring the pressure balance inside the mold; the high-pressure gas is kept in the mold for 3-5 minutes to ensure the stability of the boss shape and the forming quality; the fastening device between the lower mold 1 and the upper mold 2 is loosened to separate the upper and lower molds, and the formed inner boss ring aluminum alloy sheet part is taken out from the mold to complete the part processing.

[0039] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for machining a thin annular plate part with an inner boss, characterized in that, The specific steps are as follows: Step 1: Select metal sheet material that meets the requirements of the part material, cut the sheet material according to the specifications, and CNC mill it to obtain a blank of the preset size. Clean the oil and oxide scale from the surface of the blank. Step 2: Clamp the pre-treated sheet blank into the three-axis roll bending machine, calculate and adjust the upper roller shaft pressing amount H of the three-axis roll bending machine, and perform a multi-pass progressive roll bending process to form a ring blank with a preset curvature. Step 3: Place the rolled and bent annular blank into the bulging mold, and introduce high-pressure gas to make the annular blank fit the cavity of the bulging mold and form an inner boss, thus completing the precise forming of the inner boss and the outer contour of the annular shape in one go.

2. The processing method for an annular thin plate part with an inner boss as described in claim 1, characterized in that, In step one, the cutting and blanking process involves using aerospace sheet metal design software to unfold the three-dimensional model of the inner boss ring part into a two-dimensional planar outline. Then, a two-axis CNC milling machine and a tool with a diameter of 4-6mm are used to precision mill the two-dimensional planar outline. This allows for the completion of internal and external machining without tool changes, making it easier to machine the internal holes of the part, thereby obtaining a sheet blank that meets the dimensional accuracy requirements.

3. The processing method for an annular thin plate part with an inner boss as described in claim 1, characterized in that, In step two, the calculation formula for adjusting the upper roller shaft pressing amount H is as follows: ， In the formula, Rq is the bending radius of the inner surface of the annular thin plate part before springback; Rz is the radius of the lower roller shaft; t is the material thickness; and a is half of the horizontal center distance between the two lower roller shafts of the three-axis roll bending machine.

4. The processing method for an annular thin plate part with an inner boss as described in claim 1, characterized in that, In step two, the multi-pass progressive roll bending process specifically includes: Each pass involves pre-bending the annular blank to a radius 1.0 to 1.1 times larger than the preset curvature radius, followed by bending at 1.1 to 1.2 times the upper roller pressing amount H to form a preliminary profile. Then, gradually reduce the bending radius to 0.9 to 1.0 times the bending radius Rq of the inner surface of the sheet blank before springback, that is, roll bending to obtain a cylindrical annular blank with unclosed joints; Meanwhile, diameter is checked after each rolling bend to correct roundness and flatness, ensuring that the outer contour of the annular billet meets the subsequent bulging reference requirements and ultimately achieves the preset curvature radius of curvature of the annular billet.

5. The processing method for an annular thin plate part with an inner boss as described in claim 1, characterized in that, In step three, the bulging mold includes a lower mold (1) and an upper mold (2). The lower mold (1) is a cylindrical structure mold with a cylindrical mounting cavity. Multiple through lower mold vent holes (3) are evenly opened on the circumferential direction of the circular bottom surface of the lower mold (1) to discharge the residual gas in the forming process inside the mold. The upper mold (2) with a central hole is coaxial and installed in the cylindrical mounting cavity of the lower mold (1) by connecting bolts. The upper mold (2) and the lower mold (1) together form a forming cavity (11) that matches the outer contour of the inner boss annular thin plate part. The plug (4) is installed in the center hole of the upper mold (2). The plug (4) has sealing grooves at both ends of the circumference. The upper sealing ring (6) and the lower sealing ring (5) are installed in the sealing grooves to provide radial sealing and prevent leakage during the inflation process. The outer wall of the plug core (4) located between the upper sealing ring (6) and the lower sealing ring (5) is provided with an air guide groove (8); an air outlet (7) communicating with the forming cavity (11) is provided on the groove wall of the air guide groove (8). The pressure cap (9) is fixed to the plug (4) by fasteners, and the air inlet pipe (10) passes through the through hole on the pressure cap (9) to connect to the external high-pressure air source.

6. The processing method for an annular thin plate part with an inner boss as described in claim 5, characterized in that, The lower mold (1) is made of cold work die steel; the number of vent holes (3) of the lower mold is 4 to 6. Too many vent holes (3) of the lower mold will affect the strength of the mold, and too few vent holes (3) of the lower mold will affect the film application of the parts.

7. The processing method for an annular thin plate part with an inner boss as described in claim 5, characterized in that, The plug (4) has a through-hole at its central axis, which is used to quickly release the high-pressure gas in the mold after molding and to ensure uniform release.

8. The method for processing an annular thin plate part with an inner boss as described in claim 7, characterized in that, The compression cap (9) has a through hole in the center, and the air inlet pipe (10) is screwed into the through hole and coaxially connected with the exhaust hole of the plug core, for connecting an external high-pressure air source and delivering forming pressure into the mold.

9. A method for processing an annular thin plate part with an inner boss as described in any one of claims 5 to 8, characterized in that, The method of using the bulging mold is as follows: First, fix the upper mold (2) in the cylindrical mounting cavity of the lower mold (1) to complete the positioning and locking of the upper and lower molds; install the upper sealing ring (6) and the lower sealing ring (5) into the sealing grooves at both ends of the plug core (4) respectively, and then install the plug core (4) coaxially into the center hole of the upper mold (2) and position it. Then, the rolled annular blank is placed into the forming cavity (11) from top to bottom along the outer wall of the plug (4), so that the lower end of the annular blank is stably attached to the positioning surface of the end of the plug (4), ensuring that the blank is coaxial with the forming cavity (11) without offset. Next, press the clamping cap (9) onto the plug (4) and tighten it evenly with screws to ensure the overall sealing of the mold; introduce high-pressure gas through the air inlet pipe (10) to force the outer wall of the blank to fit tightly against the inner wall of the upper and lower mold cavities, and complete the precise forming of the inner boss and outer ring contour of the boss ring thin plate part in one go. Hold the pressure for 3 to 5 minutes to ensure the stable shape and accurate size of the boss. Finally, after the forming is completed, the high pressure gas in the forming cavity (11) is released through the core plug vent hole. The residual gas is discharged from the forming cavity (11) through the lower mold vent hole (3). After the pressure is completely released, the upper and lower mold connecting bolts are loosened and the mold is separated. The formed inner boss ring aluminum alloy thin plate part is taken out from the bulging mold to complete the processing.

10. A method for processing an annular thin plate part with an inner boss as described in any one of claims 1 to 8, characterized in that, The annular thin plate part with the boss is made of aluminum alloy; the pressure value of the high-pressure gas is greater than 10% of the yield strength of the aluminum alloy material, ensuring that the air pressure can compress the plate and force it to stretch.

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