A processing method of a long-span annular hollow structure part with thin wall and weak rigidity

Abstract

The application relates to the technical field of aerospace part machining, and discloses a machining method for a thin-wall weak-rigidity long-span annular hollow structure part, which comprises the following steps: S1, preparation of a part blank; S2, clamping of the part blank by using a front face pad-up tooling, and the like. For the clamping of the thin-wall weak-rigidity structure, a self-adaptive compression tooling is designed to realize self-adaptive compression of the part, so that the clamping force direction of the self-adaptive compression device is perpendicular to the larger surface among all the contact surfaces between the main positioning element and the part, the part has sufficient clamping rigidity, machining vibration is prevented, the machining efficiency is improved, and the part surface quality is ensured; the part is divided into zones for stable cutting machining by taking the part reinforcing ribs as the division interfaces; the principle followed in the stable machining is'machining from the weak-rigidity part to the stronger-rigidity part', the unprocessed part of the zero is fully utilized to support the part being milled, the part is always in the best rigidity state, and the machining spring of the part is effectively prevented.

Description

Technical Field

[0001] This invention relates to the field of aerospace parts machining technology, specifically, a machining method for thin-walled, weakly rigid, long-span annular hollow structural parts. Background Technology

[0002] The problem of machinability issues in weakly rigid structural components is widespread in the aerospace, aviation, automotive, shipbuilding, and other mechanical manufacturing industries, as well as the chemical industry. With the development of aircraft design and manufacturing technology, aerospace structural components have gradually moved towards larger size, integral construction, and thinner walls. To reduce aircraft weight, thin-walled structures are widely used in aircraft design and manufacturing. These thin-walled, weakly rigid parts are directly machined from sheet metal, presenting numerous processing challenges, such as high material removal rates from sheet metal, complex part structures, numerous curved surfaces, and difficulty in controlling clamping and machining deformation.

[0003] As attached Figure 1 , Figure 2 The image shows a typical thin-walled, weakly rigid aerospace component. The component has a long-span, hollow, annular structure with extremely poor overall structural rigidity. The component spans approximately 650mm in length and 210mm in width, with an overall wall thickness requirement of 2mm ± 0.1mm. The opening depth is approximately 195mm, and the material removal rate reaches 97.8%. Currently, it is typically manufactured using the following methods:

[0004] (1) Using 3D printing. This requires specialized 3D printing equipment for additive printing of parts. Due to the extremely poor overall structural rigidity of the parts, the printing performance is poor; moreover, the surface quality of the printed parts cannot meet the design requirements, requiring secondary processing. Clamping and positioning are difficult, the processing is challenging, and the cost is high.

[0005] (2) Traditional machining methods, due to the complex shape and structure of the parts, typically involve leaving process bosses in the relatively simple internal cavities. After rough machining, the parts undergo manual aging for more than 30 days. Then, fillers (such as plaster) are added to the internal cavities to enhance the rigidity of the parts. After the parts are shaped, a fitter removes the process bosses and grinds the connecting surfaces of the process bosses. This method results in a long production cycle, low efficiency of manual work by fitters, and the processing quality of the products largely depends on the experience of the workers, requiring extremely high skill levels from them, leading to poor product quality stability. Summary of the Invention

[0006] The purpose of this invention is to provide a processing method for thin-walled, weakly rigid, long-span annular hollow structural parts, which solves the problems of long production cycle, difficult clamping and positioning, and poor product quality stability in the existing technology.

[0007] This invention is achieved through the following technical solution: a method for processing thin-walled, weakly rigid, long-span annular hollow structural parts, comprising the following steps:

[0008] Step S1: Preparation of part blanks;

[0009] Step S2: Use a front-mounted lifting fixture to clamp the part blank, and clamp it once on a vertical-horizontal convertible five-axis CNC machine tool to process the front shape features and all internal features of the target part.

[0010] Step S3: Use a reverse-side shim fixture to clamp the part blank. The reverse-side shim fixture is equipped with multiple adaptive clamping mechanisms. The adaptive clamping mechanisms are used to assist in clamping the target part. The reverse features of the target part are processed in one clamping on a vertical-horizontal conversion five-axis CNC machine tool.

[0011] Step S4: After CNC machining is completed, the target part is removed from the raised fixture on the reverse side. The fitter then removes the process boss reserved in step S3 to obtain the final product.

[0012] To better realize the present invention, step S1 further includes the following steps:

[0013] Step S11: Machining a rectangular parallelepiped blank;

[0014] Step S12: Make several tension threaded holes on the reverse side of the target part corresponding to the part blank. The tension threaded holes are used to fix the part blank on the front side of the raised tooling.

[0015] To better realize the present invention, the front-side elevation fixture is further provided with multiple first U-shaped grooves, second U-shaped grooves, third U-shaped grooves, and bolt through holes; the vertical-to-horizontal conversion five-axis CNC machine tool is provided with five cutting tools; step S2 specifically includes the following steps:

[0016] Step S21: Using ordinary bolts, place the front-mounted shim fixture on the vertical-horizontal conversion five-axis CNC machine tool through the first U-shaped groove and the second U-shaped groove. After multiple tension bolts are inserted through the corresponding bolt through holes and screwed into the tension thread holes, the part blank is tightly locked on the front-mounted shim fixture. At this time, the machined part of the target part is fully exposed, and the deep groove cavity of the target part is in a horizontal state.

[0017] Step S22: Due to the large amount of material to be removed from the part blank, first select a φ100 large diameter tool to remove the large amount, leaving a 5mm allowance.

[0018] Step S23: Select a φ32 tool for secondary roughing and leave a 1mm allowance;

[0019] Step S24: Select a φ20 tool to finish the plane, and a φ16R3B4 tapered ball end tool to finish the curved surface and V-shaped flange narrow groove, so that the target part has the first front unit, the second front unit, the third front unit, the fourth front unit, the fifth front unit, and the sixth front unit plane, and at the same time mill process bosses on the part blank.

[0020] Step S25: After machining the front shape features and all internal features of the target part, remove the tension bolts, remove the part blank from the front shim fixture, and remove the front shim fixture.

[0021] To better realize the present invention, the reverse side shim tooling is further provided with a clamping threaded hole, a part support surface, a clearance groove, a fourth U-shaped groove, a clamping bolt, a fifth U-shaped groove, and a clearance step; step S3 specifically includes the following steps:

[0022] Step S31: Using ordinary bolts, place the reverse shim fixture on the vertical-horizontal conversion five-axis CNC machine tool through the fourth U-shaped groove and the fifth U-shaped groove. Then, after multiple clamping bolts are inserted through the corresponding process bosses and screwed into the clamping threaded holes, the part blank is tightly locked on the reverse shim fixture. At this time, the support surface of the part is in contact with the first unit, the second unit, the third unit, and the fourth unit of the front side to provide support.

[0023] Step S32: Adjust the adaptive clamping mechanism to clamp the fifth and sixth front units to assist in fixing the target part;

[0024] Step S33: Use CAM software to program and process the front features of the part;

[0025] Step S34: Use a φ32 cutting tool to roughen the part as a whole, leaving a 30mm allowance;

[0026] Step S35: Select a φ16 cutting tool to perform a second roughing process from the part with the weakest rigidity in the middle to both sides, leaving an 8mm allowance.

[0027] Step S36: Use a φ16R3B4 tapered ball end mill to divide the curved surface of the target part into sections, cut to size in one pass, leave an 8mm finishing allowance, and then finish directly to the final size.

[0028] Step S37: After all parts are machined, leave the connecting ribs of the process boss on both ends of the target part, and use a φ8R0.5 tool to machine the connecting ribs between the process boss and the target part body.

[0029] To better implement the present invention, further, mounting threaded holes are provided on the reverse elevation tooling, and a locking nut, a pressure plate, a support screw, a compression nut, a washer, a compression stud, and a pressure head assembly are provided on the adaptive clamping mechanism. The compression stud is slidably connected to the pressure plate. The specific step S32 is as follows: Insert the compression stud into the mounting threaded hole, lock the compression stud with the locking nut to prevent the compression stud from moving up and down. By pulling the pressure plate, adjust the position of the pressure head assembly so that the pressure head assembly presses on the fifth unit or the sixth unit on the front side. Then place the support screw on the avoidance step, and at the same time twist the locking nuts on the compression nut and the support screw, so that the pressure plate presses the target part tightly.

[0030] To better implement the present invention, further, the pressure head assembly includes a pressure ball support stud, a pressure ball, and a hole-type wire snap ring. The pressure ball support stud is threadedly connected to the pressure plate. The pressure ball is nested on the pressure ball support stud. The pressure ball is designed in a "convex" shape, and one end of the spherical surface of the pressure ball is installed and fixed in the spherical surface groove at the end of the pressure ball support stud through the hole-type wire snap ring.

[0031] To better implement the present invention, further, the end of the support screw is set as a ball head with SR30. The compression nut is designed as a nut with a shoulder structure, and the compression surface is set as a convex spherical surface with SR25. One side of the washer is set as a flat surface and contacts the pressure plate, and the other side is set as a concave spherical surface with SR25 and is used in cooperation with the convex spherical surface of the compression nut; the through-hole φD of the washer is 3 mm larger than the diameter of the compression stud, that is, φD = φd + 3 mm.

[0032] To better implement the present invention, further, a taper ball nose cutter with φ16R3B4 is used to perform stable cutting on the curved surface features of the target part. The principle followed by stable machining is "machining from the weak rigid part to the stronger rigid part".

[0033] To better implement the present invention, further, the feed trajectory during contour milling is in an "S" shape.

[0034] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0035] (1) This technical solution provides a numerical control milling method for the efficient machining of thin-walled, weakly rigid, long-span annular hollow structure parts. For the clamping of thin-walled and weakly rigid structures, through the designed reverse elevation tooling and adaptive clamping mechanism, the support surface of the tooling base is made to fit the part surface, and then the small plane of the "convex" pressure ball adapts to the change of the inclined plane of the part for self-adaptive adjustment to achieve self-adaptive clamping of the part, ensure the clamping rigidity of the part, prevent machining vibration, thereby improving machining efficiency and ensuring the surface quality of the part;

[0036] (2) In this technical solution, two roughing operations are performed using a large-diameter tool to remove residual stress generated during the large allowance, reduce the deformation of the parts during machining, and reserve a large finishing allowance (8mm finishing allowance) to ensure that the parts have sufficient rigidity. During finishing, the parts are directly machined to the final size, so that the tool is always in contact with the rigid surface to be machined. Although the final rigidity of the parts is weak, it has good real-time rigidity during the machining process, which reduces machining deformation, improves the surface quality of the parts, and minimizes the problem of parts being scrapped due to deviation. This further reduces the workload of subsequent fitter grinding.

[0037] (3) In this technical solution, based on the structural characteristics of the part, the part is divided into sections for stable cutting. The principle of stable cutting is "processing from the weakest part to the strongest part". The unprocessed part of the part is fully utilized to support the part being milled, so that the part is always in the best rigidity state and effectively prevents the part from being ejected during processing.

[0038] (4) In this technical solution, a tapered end mill is used to cut and finish the curved surface from the middle of the weak rigidity to both sides. When the tapered ball end mill is used for cutting, it can effectively reduce the vibration caused by bending deformation under the action of the radial force of the tool and the risk of tool pull under the action of axial force. The downward resultant force can make the side of the tool press against the surface of the workpiece, effectively improving the stability of the machining process, preventing tool pull, and further reducing the subsequent work of fitter grinding. Attached Figure Description

[0039] Figure 1 This is a two-dimensional planar schematic diagram of a ring-shaped hollow structure part.

[0040] Figure 2 This is a two-dimensional planar sectional view of a ring-shaped hollow structural part.

[0041] Figure 3 A schematic diagram of a clamping device for machining the front side of the target part.

[0042] Figure 4 A schematic diagram of the process path planning when machining the front side of the target part.

[0043] Figure 5 This is a schematic diagram of the target part after the front surface has been finished.

[0044] Figure 6 A schematic diagram of a clamping device for machining the reverse side of the target part.

[0045] Figure 7 This is a schematic diagram of the tooling structure for raising the reverse side.

[0046] Figure 8 This is a cross-sectional view of the adaptive clamping mechanism.

[0047] Figure 9 for Figure 8 Enlarged view of the local structure at point I.

[0048] Figure 10 This is a schematic diagram of the clamping nut and washer structure.

[0049] Figure 11 A schematic diagram of the machining process route for the reverse side of the target part.

[0050] Figure 12 This is a schematic diagram of the tool path of a tapered tool cutting the reverse side.

[0051] Figure 13 This is a schematic diagram of the force analysis during tapered cutting.

[0052] Figure 14 This is a schematic diagram of the thin-walled connection structure between the process boss and the part body.

[0053] Wherein: 1-Front-side shim fixture; 2-Part blank; 3-Target part; 4-Back-side shim fixture; 5-Adaptive clamping mechanism; 6-Cutting tool; 101-First U-groove; 102-Second U-groove; 103-Third U-groove; 104-Bolt through hole; 105-Tightening bolt; 201-Tightening threaded hole; 202-Process boss; 301-Front-side first unit; 302-Front-side second unit; 303-Front-side third unit; 304-Front-side fourth unit; 305-Front-side fifth unit Unit; 306 - Sixth unit on the front; 401 - Mounting threaded hole; 402 - Clamping threaded hole; 403 - Part support surface; 404 - Clearance groove; 405 - Fourth U-shaped groove; 406 - Clamping bolt; 407 - Fifth U-shaped groove; 408 - Clearance step; 501 - Locking nut; 502 - Pressure plate; 503 - Support screw; 504 - Clamping nut; 505 - Washer; 506 - Clamping stud; 507 - Clamping ball support stud; 508 - Clamping ball; 509 - Wire retaining ring for hole. Detailed Implementation

[0054] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0055] Example 1:

[0056] like Figures 1-14 As shown, a method for processing a thin-walled, weakly rigid, long-span annular hollow structural part is characterized by the following steps:

[0057] Step S1: Preparation of part blank 2;

[0058] Step S2: Use the front-mounted lifting fixture 1 to clamp the part blank 2, and clamp it once on the vertical-horizontal conversion five-axis CNC machine tool to process the front shape features and all internal features of the target part 3.

[0059] Step S3: The blank part 2 is clamped using the reverse side shim fixture 4. The reverse side shim fixture 4 is equipped with multiple adaptive clamping mechanisms 5. The adaptive clamping mechanisms 5 are used to assist in clamping the target part 3. The reverse side features of the target part 3 are processed in one clamping on the vertical-horizontal conversion five-axis CNC machine tool.

[0060] Step S4: After CNC machining is completed, the target part 3 is removed from the reverse side of the raised fixture 4. The fitter then removes the process boss 202 reserved in step S3 to obtain the final product.

[0061] Example 2:

[0062] This embodiment is a further optimization based on Embodiment 1, such as... Figure 3 As shown, step S1 specifically includes the following steps:

[0063] Step S11: Machining a rectangular parallelepiped part blank 2;

[0064] Step S12: Make several tension threaded holes 201 on the reverse side of the target part 3 corresponding to the part blank 2. The tension threaded holes 201 are used to fix the part blank 2 on the front raised tooling 1.

[0065] like Figures 3-5 As shown, the front-side elevation fixture 1 is provided with multiple first U-shaped grooves 101, second U-shaped grooves 102, third U-shaped grooves 103, and bolt through holes 104; the vertical-to-horizontal conversion five-axis CNC machine tool is provided with five cutting tools 6, and the process sequence of the five cutting tools 6 is A→B→C→D→E→A; step S2 specifically includes the following steps:

[0066] Step S21: Using ordinary bolts, place the front-mounted shim fixture 1 on the vertical-horizontal conversion five-axis CNC machine tool through the first U-shaped groove 101 and the second U-shaped groove 102. After multiple tension bolts 105 are inserted through the corresponding bolt through holes 104 and screwed into the tension threaded holes 201, the workpiece blank 2 is tightly locked on the front-mounted shim fixture 1. At this time, the machined part of the target part 3 is fully exposed, and the deep groove cavity of the target part 3 is in a horizontal state, which makes it easier to remove chips when machining the deep groove.

[0067] Step S22: Due to the large amount of material to be removed from the blank 2, a φ100 large-diameter tool 6 is first selected to remove the large amount of material, leaving a 5mm allowance to improve the part processing efficiency.

[0068] Step S23: Select a φ32 tool 6 for secondary roughing and leave a 1mm allowance. Secondary roughing can effectively reduce the residual stress generated when the large-diameter tool 6 removes a large allowance, thereby reducing the machining deformation of the target part 3.

[0069] Step S24: Select a φ20 tool 6 to finish the plane, and a φ16R3B4 (tool shank diameter 16mm, ball head radius R3mm, taper 4mm) tapered ball head tool 6 to finish the curved surface and V-shaped flange narrow groove. The tapered tool 6 can effectively improve the rigidity of the tool 6. The tapered tool 6 can effectively achieve avoidance at the tool shank. The large diameter tool shank enhances the rigidity of the tool. The ball head at the front end of the cone can be machined to produce a smaller bottom angle or corner, so that the target part 3 has the front first unit 301, front second unit 302, front third unit 303, front fourth unit 304, front fifth unit 305, and front sixth unit 306 planes. At the same time, the process boss 202 is milled on the part blank 2.

[0070] Step S25: After machining the front shape features and all internal features of the target part 3, remove the tension bolt 105, remove the part blank 2 from the front shim fixture 1, and remove the front shim fixture 1.

[0071] Example 3:

[0072] This embodiment is a further optimization based on embodiment 1 or 2, such as... Figures 6-14 As shown, the reverse-side shim tooling 4 is provided with a clamping threaded hole 402, a part support surface 403, a clearance groove 404, a fourth U-shaped groove 405, a clamping bolt 406, a fifth U-shaped groove 407, and a clearance step 408; step S3 specifically includes the following steps:

[0073] Step S31: Using ordinary bolts, place the reverse shim fixture 4 on the vertical-horizontal conversion five-axis CNC machine tool through the fourth U-shaped groove 405 and the fifth U-shaped groove 407. Then, after multiple clamping bolts 406 are inserted through the corresponding process bosses 202 and screwed into the clamping threaded holes 402, the part blank 2 is tightly locked on the reverse shim fixture 4. At this time, the part support surface 403 is in contact with the front first unit 301, front second unit 302, front third unit 303 and front fourth unit 304 to provide support and improve the clamping rigidity of the target part 3.

[0074] Step S32: Adjust the adaptive clamping mechanism 5 to clamp the fifth unit 305 and the sixth unit 306 on the front side to assist in fixing the target part 3. The pressure ball 508 of the adaptive clamping mechanism can adaptively change with the angle of the inclined surface of the fifth unit 305 or the sixth unit 306 on the front side to clamp the target part 3, so that the clamping force direction is perpendicular to the surface with the larger area among all the contact surfaces between the main positioning element and the target part 3. The larger the contact area, the smaller the unit pressure, and the smaller the deformation of the part, ensuring that the target part 3 has sufficient clamping rigidity.

[0075] Step S33: Use CAM software to program and process the front features of the part;

[0076] Step S34: Select a φ32 cutting tool 6 to roughen the part as a whole, leaving a 30mm allowance to improve the machining efficiency of the target part 3.

[0077] Step S35: Select a φ16 cutting tool 6 to perform a second roughing process from the part with the worst rigidity in the middle to both sides, leaving an 8mm allowance. This can effectively ensure a certain overall rigidity, thereby improving the surface quality of the target part 3.

[0078] Step S36: Use a φ16R3B4 tapered ball end mill 6 to partition the curved surface of the target part 3, and cut it to the size in one pass, leaving an 8mm finishing allowance so that the target part 3 has sufficient rigidity. During finishing, it is directly machined to the final size, so that the tool 6 always contacts the machined surface with high rigidity. Although the final rigidity of the target part 3 is weak, it has good real-time rigidity during the machining process, which reduces the deformation of the tool 6.

[0079] Step S37: After all parts are machined, the connecting ribs of the process boss 202 are left on both ends of the target part 3. The connecting ribs between the process boss 202 and the target part 3 body are machined using a φ8R0.5 tool 6. This allows the fitter to easily separate the process boss 202, and finally achieves complete and accurate machining of the target part 3, minimizing the need for the fitter to grind the parts.

[0080] like Figures 6-10As shown, the reverse side shim tool 4 is provided with a mounting threaded hole 401, and the adaptive clamping mechanism 5 is provided with a locking nut 501, a pressure plate 502, a support screw 503, a clamping nut 504, a washer 505, a clamping stud 506, and a clamping head assembly. The clamping stud 506 is slidably connected to the pressure plate 502. Step S32 is specifically as follows: the clamping stud 506 is inserted into the mounting threaded hole 401, and the locking nut 501 is used to lock the clamping stud 506 to prevent the clamping stud 506 from moving up and down. By pulling the pressure plate 502, the position of the clamping head assembly is adjusted so that the clamping head assembly presses on the fifth unit 305 or the sixth unit 306 on the front side. Then, the support screw 503 is placed on the clearance step 408, and the clamping nut 504 and the locking nut 501 on the support screw 503 are twisted at the same time, so that the pressure plate 502 clamps the target part 3.

[0081] like Figure 8 , Figure 9 As shown, the pressure head assembly includes a pressure ball support stud 507, a pressure ball 508, and a wire retaining ring 509 for the hole. The pressure ball support stud 507 is threaded onto the pressure plate 502, and the pressure ball 508 is nested on the pressure ball support stud 507. The pressure ball 508 is designed in a "convex" shape, and one end of the spherical surface of the pressure ball 508 is fixed in the spherical groove at the end of the pressure ball support stud 507 through the wire retaining ring 509. This allows the device to adaptively adjust as the position of the pressed workpiece surface changes, and the flat end of the "convex" shaped pressure ball 508 can increase the contact area with the target part 3 to provide greater frictional clamping force. At the same time, the pressure ball 508 can achieve a wide range of adaptive adjustment from 0 degrees to 11 degrees, increasing the application range.

[0082] like Figures 6-10 As shown, the end of the support screw 503 is set as an SR30 ball head to adapt to changes in the position of the pressure plate 502 and better support the pressure plate 502. The clamping nut 504 is designed as a nut with a shoulder structure and the clamping surface is set as an SR25 convex spherical surface. One side of the washer 505 is set as a flat surface to contact the pressure plate 502, and the other side is set as an SR25 concave spherical surface to cooperate with the convex spherical surface of the clamping nut 504. The through hole φD of the washer 505 is 3mm larger than the diameter of the clamping stud 506, that is, φD=φd+3mm, so as to automatically adjust and adapt to changes in the position of the pressure plate 502 and make the force more uniform.

[0083] Example 4:

[0084] This embodiment is a further optimization based on embodiment 2 or 3, such as... Figure 13As shown, a φ16R3B4 tapered ball end mill 6 is used to perform stable cutting on the curved surface features of the target part 3. The principle of stable machining is "machining from the weakest part to the strongest part". By making full use of the unmachined part of the target part 3 to support the part being milled, the target part 3 is always in the optimal rigidity state, thereby reducing deformation.

[0085] like Figure 11 As shown, based on the structural characteristics of target part 3, the area is divided according to the position of the reinforcing rib of the target part 3 body. The area far from the clamping force point of target part 3 or far from the connecting rib of target part 3 has the weakest rigidity. The priority processing path is planned as follows: serial number a → serial number b → serial number c → serial number d → serial number e → serial number f → serial number g → serial number h → serial number i → serial number j → serial number k → serial number l → serial number m → serial number n → serial number o → serial number p.

[0086] like Figure 12 As shown, the tool path during the traverse cutting process is "S" shaped. When using a φ16R3B4 tapered ball end mill 6 to machine the curved surface features on the front of the target part 3, according to the force analysis, the tool 6 is subjected to a downward resultant force during the traverse cutting process. This effectively reduces the vibration caused by bending deformation under the radial force of the tool and the risk of tool breakage under the axial force. The downward resultant force can make the side of the tool press against the surface being machined, effectively improving the stability of the machining process.

[0087] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for processing a thin-walled, weakly rigid, long-span annular hollow structural part, characterized in that, Includes the following steps: Step S1: Preparation of part blank (2); Step S2: Use the front-mounted lifting fixture (1) to clamp the part blank (2), and clamp it once on the vertical-horizontal conversion five-axis CNC machine tool to process the front shape features and all internal features of the target part (3); Step S3: Use a reverse-side shim fixture (4) to clamp the part blank (2). The reverse-side shim fixture (4) is equipped with multiple adaptive clamping mechanisms (5). The adaptive clamping mechanisms (5) are used to assist in clamping the target part (3). The target part (3) is processed by clamping it once on a vertical-horizontal conversion five-axis CNC machine tool. Step S4: After the CNC machining is completed, the target part (3) is removed from the back-raised fixture (4), and the fitter removes the process boss (202) reserved in step S3 to obtain the final product. The front-side elevation fixture (1) is provided with multiple first U-shaped grooves (101), second U-shaped grooves (102), third U-shaped grooves (103), and bolt through holes (104); the target part (3) is provided with several tension thread holes (201); the vertical-horizontal conversion five-axis CNC machine tool is provided with five cutting tools (6); the step S2 specifically includes the following steps: Step S21: Using ordinary bolts, place the front-side shim fixture (1) on the vertical-horizontal conversion five-axis CNC machine tool through the first U-shaped groove (101) and the second U-shaped groove (102). After multiple tension bolts (105) are inserted into the corresponding bolt through holes (104) and screwed into the tension thread hole (201), the part blank (2) is locked on the front-side shim fixture (1). At this time, the machined part of the target part (3) is fully exposed, and the deep groove cavity of the target part (3) is in a horizontal state. Step S22: Due to the large amount of material to be removed from the blank (2), first select a φ100 large diameter tool (6) to remove the large amount of material and leave a 5mm allowance. Step S23: Select a φ32 tool (6) for secondary roughing and leave a 1mm allowance; Step S24: Select a φ20 tool (6) to finish the plane, and a φ16R3B4 tapered ball end mill (6) to finish the curved surface and V-shaped flange narrow groove, so that the target part (3) has the front first unit (301), front second unit (302), front third unit (303), front fourth unit (304), front fifth unit (305), and front sixth unit (306) planes, and at the same time, mill the process boss (202) on the part blank (2); Step S25: After processing the front shape features and all features of the inner cavity of the target part (3), remove the tension bolt (105), remove the part blank (2) from the front shim fixture (1), and remove the front shim fixture (1). The reverse-side shim tooling (4) is provided with a clamping threaded hole (402), a part support surface (403), a clearance groove (404), a fourth U-shaped groove (405), a clamping bolt (406), a fifth U-shaped groove (407), and a clearance step (408); step S3 specifically includes the following steps: Step S31: Using ordinary bolts, place the reverse side shim fixture (4) on the vertical-horizontal conversion five-axis CNC machine tool through the fourth U-shaped groove (405) and the fifth U-shaped groove (407). Then, through multiple clamping bolts (406) inserted into the corresponding process bosses (202), they are screwed into the clamping threaded holes (402) so that the part blank (2) is tightly locked on the reverse side shim fixture (4). At this time, the part support surface (403) is in contact with the front first unit (301), front second unit (302), front third unit (303), and front fourth unit (304) to provide support. Step S32: Adjust the adaptive clamping mechanism (5) to clamp the fifth unit (305) and the sixth unit (306) on the front side to assist in fixing the target part (3); Step S33: Use CAM software to program and process the front features of the part; Step S34: Select a φ32 cutting tool (6) to roughen the part as a whole, leaving a 30mm allowance; Step S35: Select a φ16 cutting tool (6) to perform a second roughing process from the part with the worst rigidity in the middle to both sides, leaving an 8mm allowance; Step S36: Use a φ16R3B4 tapered ball end mill (6) to partition the curved surface of the target part (3), cut it to size in one pass, leave an 8mm finishing allowance, and then finish it directly to the final size; Step S37: After all parts are machined, leave the connecting ribs of the process boss (202) on both ends of the target part (3), and use a φ8R0.5 tool (6) to machine the connecting ribs between the process boss (202) and the target part (3) body; The reverse side shim tool (4) is provided with a mounting threaded hole (401). The adaptive clamping mechanism (5) is provided with a locking nut (501), a pressure plate (502), a support screw (503), a clamping nut (504), a washer (505), a clamping stud (506), and a pressure head assembly. The clamping stud (506) is slidably connected to the pressure plate (502). The specific step S32 is: inserting the clamping stud (506) into the mounting threaded hole (401) and using the locking nut (504) to clamp the pressure plate (505). 01) Lock the clamping stud (506) to prevent the clamping stud (506) from moving up and down. By pulling the pressure plate (502), adjust the position of the pressure head assembly so that the pressure head assembly presses on the fifth unit (305) or the sixth unit (306) on the front. Then place the support screw (503) on the clearance step (408) and twist the clamping nut (504) and the locking nut (501) on the support screw (503) so that the pressure plate (502) presses the target part (3). The pressure head assembly includes a pressure ball support stud (507), a pressure ball (508), and a wire retaining ring (509) for the hole. The pressure ball support stud (507) is threaded onto the pressure plate (502). The pressure ball (508) is nested on the pressure ball support stud (507). The pressure ball (508) is designed in a "convex" shape. One end of the spherical surface of the pressure ball (508) is installed and fixed in the spherical groove at the end of the pressure ball support stud (507) through the wire retaining ring (509). The surface features of the target part (3) are machined using a tapered ball end mill (6) with a diameter of φ16R3B4. The principle of the machining process is to "machine from the weakest part to the strongest part".

2. The processing method for a thin-walled, weakly rigid, long-span annular hollow structural part according to claim 1, characterized in that, Step S1 specifically includes the following steps: Step S11: Machining a rectangular parallelepiped blank (2); Step S12: Make several tension threaded holes (201) on the reverse side of the target part (3) corresponding to the part blank (2). The tension threaded holes (201) are used to fix the part blank (2) on the front-side raised tooling (1).

3. The processing method for a thin-walled, weakly rigid, long-span annular hollow structural part according to claim 1, characterized in that: The end of the support screw (503) is set as an SR30 ball head, the clamping nut (504) is designed as a nut with a shoulder structure and the clamping surface is set as an SR25 convex spherical surface. One side of the washer (505) is set as a flat surface to contact the pressure plate (502), and the other side is set as an SR25 concave spherical surface to cooperate with the convex spherical surface of the clamping nut (504). The through hole φD of the washer (505) is 3mm larger than the diameter of the clamping stud (506), that is, φD=φd+3mm.

4. The processing method for a thin-walled, weakly rigid, long-span annular hollow structural part according to claim 1, characterized in that: The tool path during line cutting is "S" shaped.

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