Manufacturing method of variable-curvature complex skin with reinforcing bent edge and n-shaped cross section

Abstract

The invention belongs to the technical field of aviation aircraft sheet metal part machining, and relates to a manufacturing method of a variable-curvature complex skin with a reinforcing bent edge and an n-shaped cross section. The technological process of stretching forming, numerical control milling and manual forming is used for replacing the single technological process of linear blanking, pressure falling forming, manual forming, appearance cutting and drilling, and two sets of newly-designed tools are matched for part forming and edge cutting. The problems of out-of-tolerance of the profile size, high labor intensity, poor surface quality, high rejection rate and the like in the forming process of the variable-curvature complex skin part with the n-shaped section are solved. In production, main deformation and edge milling of parts are completed through machining, product precision is improved, labor intensity of workers is remarkably reduced, the parts do not have large-area hammer marks, and surface quality is remarkably improved. The method can be used for machining large complex variable-curvature parts and can be widely applied to the field of aeronautical manufacturing.

Description

Technical Field

[0001] The invention belongs to the technical field of processing sheet metal parts of aviation aircraft, and relates to a method for manufacturing a complex skin with a "J"-shaped cross section and variable curvature with a reinforced bent edge. Background Art

[0002] Aircraft have a special structural skin, which is different from the traditional single-curvature or double-curvature large-radius skin structure. The typical characteristics of this type of parts are the complex variable curvature shape of the "J"-shaped cross-section with reinforced curved edges, and the belly plate has 10-φ2.7 assembly holes. Since the fairing skin affects the aerodynamic shape of the aircraft, high manufacturing accuracy and surface quality requirements are required. The typical processing flow of this type of parts is "straight line cutting-press forming-manual forming-cutting shape-drilling", that is, the shape of the part is pressed out by a press die in the rough state, and then the reinforced curved edges are made manually, and finally the shape is cut and the assembly holes are drilled according to the template. Because the part is a slender structure, the press die used for forming is large in size and is easily deformed under the impact of the drop hammer, resulting in errors in the part surface. During drop forming, the rough material is deformed under the impact of the drop hammer, and the surfaces with different characteristics are subjected to uneven force, resulting in large rebound and residual stress. After forming, it is necessary to manually "collect", "release" and "combine collection and release" to perform rebound trimming and residual stress removal. Not only is the manufacturing precision of the parts low, but the labor intensity is also high. A large amount of trimming and grinding causes poor surface quality of the parts, thus affecting the aerodynamic shape of the aircraft. In addition, the material thickness of the part is δ1.5mm, and the minimum radius of the reinforced bending edge is only R2.4mm. Cracks are easily generated during the forming process, and the scrap rate is usually more than 30%. The edges of the parts are cut manually, with low precision. They cannot be quickly assembled with other parts during assembly, and the assembly efficiency is low. The above problems make it difficult to form such parts. Summary of the invention

[0003] The purpose of the present invention is to invent a method for manufacturing a complex variable curvature skin with a "J"-shaped cross section with a reinforced curved edge. The manufacturing method changes the processing mode of "straight line blanking - drop pressure forming - manual forming - cutting shape" to "stretching forming - CNC milling - manual forming" by designing a new set of molds for forming parts and a set of fixtures for milling. The molds used in the present invention can realize the precise forming of parts with complex curvatures, and the milling fixture can realize fast cutting and drilling of the edge of the parts, thereby realizing the precise manufacturing of the complex variable curvature skin with a "J"-shaped cross section with a reinforced curved edge, reducing labor intensity and scrap rate, and improving production efficiency.

[0004] In order to achieve the above object, the technical solution of the present invention is:

[0005] The invention discloses a method for manufacturing a complex skin with a "J"-shaped cross section and variable curvature with a reinforced bent edge. The manufacturing method mainly comprises three processes: stretching forming, CNC milling and manual forming.

[0006] The first process is stretch forming.

[0007] Stretching forming and manual forming share a set of molds. The tooling adopts a detachable structure and can be disassembled and used according to forming requirements to achieve its function. The tooling includes: carcass, partial carcass, positioning pins, screws, special positioning pins, side cover plates, integral cover plates, special mold pins, cores, fixed drill sleeves, movable handles, and eye screws.

[0008] The tooling "mold tire" can realize the variable curvature structure of the "U" cross section of the sheet material, and can form this structure to the final shape of the part. Its structural carcass is designed according to the inner surface of the part, and the local carcass is made into an unfolded state and a detachable structure according to the corresponding position of the "J"-shaped bend. The local carcass and the carcass are aligned with the carcass by positioning pins and fixed with screws. The special positioning pins are used to position the part on the carcass. The side cover plate is designed according to the inner shape of the "J"-shaped bend, and is aligned with the carcass by positioning pins and fixed with screws. The overall cover plate is aligned with the carcass through a special mold pin, which is used to clamp and fix the parts when trimming, and a through hole is made at the reinforced bend, which is used to strengthen the bend forming with the core. The core is manufactured according to the outer surface of the reinforced bend of the part, which is used to strengthen the bend forming. The fixed drill sleeve is installed on the cover plate for the inspection of the assembly hole position, and the movable handle is installed on the overall cover plate to facilitate the installation and removal of the overall cover plate. The eye screw is installed on the carcass for the handling and lifting of the tooling. The above structure is manufactured according to the data set, the surface manufacturing tolerance is ±0.1mm, and the working surface roughness is not higher than Ra1.6.

[0009] During stretch forming, the overall cover plate, side cover plate, core and other structures are removed, leaving only the main structures such as the carcass and partial carcass.

[0010] The second process is CNC milling.

[0011] The tooling used in the CNC milling process is the "milling fixture", which includes: locating pins, vacuum adsorption devices and sealing strips, uncoated wire screw sleeves, hanging rods, and nozzles for vacuum fixtures.

[0012] The tooling "milling fixture" can realize the precise milling of the edges and inner holes of the "U" section blank formed by the stretching process and the drilling of assembly holes for subsequent sheet metal forming. Its structural carcass is designed according to the part process data set. Considering the slender structure of the part, in order to prevent the deformation of the tooling and tipping during milling, the bottom of the carcass is widened to form a "convex" structure as a whole. A pressure plate groove is added at a position 40mm from the bottom to fix the tooling on the platform during milling. A reference hole is set at the top of the carcass for tooling alignment and as the coordinate origin during CNC milling. The positioning pin is installed at the top of the carcass for part positioning during milling. In order to ensure that the parts and the fixture fit tightly during milling, a vacuum adsorption device is added inside the carcass, and a sealing strip is laid near the milling edge. The uncoated wire screw sleeve is installed at the carcass position about 150mm away from the edge of the part. During milling, it cooperates with the pressure plate to enhance the compaction of the blank to prevent the failure of the vacuum adsorption device during milling and cause the position of the part to move. The lifting rod runs through the carcass for the handling and lifting of the tooling. The vacuum fixture uses a nozzle to connect the vacuum adsorption device inside the tire body to evacuate the vacuum during milling. The above structure is manufactured using SAM-900-LX epoxy resin as the surface and SAM910 resin as the base. The manufacturing tolerance of the profile is ±0.1mm, and the roughness of the working profile is not higher than Ra1.6.

[0013] The third process is manual forming.

[0014] The tooling used for manual forming is the "mold tire", which is the same set of tooling used for stretch forming. During manual forming and trimming, the partial tire body is removed, and the tire body is used in conjunction with the cover plate and the side cover plate to form a "J"-shaped structure. The tire body is used in conjunction with the core to form the reinforced curved edge on the web.

[0015] Beneficial effects of the present invention:

[0016] By using the process of "stretching forming - CNC milling - manual forming" to replace the single process of "straight line cutting - drop forming - manual forming - cutting shape - drilling", and using two sets of newly designed tooling for part forming and edge cutting, the problems of "J"-shaped cross-section variable curvature complex skin parts forming process, large labor intensity, poor surface quality, high scrap rate, etc. were solved. The main deformation and edge milling of parts in production are completed by mechanical processing, the product precision is improved, the labor intensity of workers is significantly reduced, there are no large-area hammer marks on the parts, and the surface quality is significantly improved.

[0017] This method can be used to process large and complex parts with variable curvature and can be widely used in the field of aviation manufacturing. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 , Parts appearance drawing;

[0019] Figure 2, Schematic diagram of milling parts;

[0020] Figure 3 , overall structure diagram of mold;

[0021] Figure 4 , detailed structure diagram of mold;

[0022] Figure 5 , milling fixture structure diagram.

[0023] In the figure: 1. carcass; 2. partial carcass; 3. locating pin; 4. screw; 5. special locating pin; 6. side cover; 7. integral cover; 8. special die pin; 9. core; 10. fixed drill sleeve; 11. movable handle; 12. lifting eye screw; 13. structural carcass; 14. locating pin; 15. vacuum adsorption device and sealing strip; 16. uncoated wire screw sleeve; 17. hanging rod; 18. nozzle for vacuum clamp. DETAILED DESCRIPTION

[0024] Embodiment 1:

[0025] The specific plan for manufacturing a complex variable curvature skin with a "J"-shaped cross-section and reinforced curved edges is as follows:

[0026] By using the process flow of "stretching forming - CNC milling - manual forming" to replace the single process flow of "straight line cutting - drop pressing forming - manual forming - cutting shape - drilling", and coordinating two sets of newly designed tooling for part forming and edge cutting, the problems of out-of-tolerance surface size, high labor intensity, poor surface quality, high scrap rate, etc. in the forming process of complex skin parts with "J"-shaped cross-section and variable curvature are solved. The specific steps are briefly introduced as follows.

[0027] Figure 3 , Figure 4 , Figure 5 As shown, a complex variable curvature skin with a "J"-shaped cross section and a reinforced curved edge is manufactured, and the manufacturing method is implemented based on a mold and a milling fixture. The mold structure includes: a carcass 1, a partial carcass 2, a positioning pin 3, a screw 4, a special positioning pin 5, a side cover plate 6, an integral cover plate 7, a special mold pin 8, a core 9, a fixed drill sleeve 10, a movable handle 11, and a lifting eye screw 12. The milling fixture structure includes: a positioning pin 14, a vacuum adsorption device and a sealing strip 15, an uncoated wire screw sleeve 16, a hanging rod 17, and a nozzle 18 for a vacuum fixture.

[0028] The tooling "mold tire" can realize the variable curvature structure of the "U" cross section of the sheet material, and can form this structure to the final shape of the part. Its structural carcass 1 is designed according to the inner surface of the part, and the partial carcass 2 is made into an unfolded state and a detachable structure according to the corresponding position of the "J"-shaped bend. The partial carcass 2 and the carcass 1 are aligned with the positioning pin 3 and fixed with the screw 4, and the special positioning pin 5 is used to position the part on the carcass. The side cover plate 6 is designed according to the inner shape of the "J"-shaped bend, and is aligned with the carcass 1 with the positioning pin 3 and fixed with the screw 4. The integral cover plate 7 is aligned with the carcass through a special mold pin 8, which is used to clamp and fix the part when trimming the part, and a through hole is made at the reinforced bend, and the core 9 is used to strengthen the bend forming. The core 9 is manufactured according to the outer surface of the reinforced bend of the part, and is used to strengthen the bend forming. The fixed drill sleeve 10 is installed on the cover plate for the inspection of the assembly hole position, and the movable handle 11 is installed on the integral cover plate to facilitate the installation and disassembly of the integral cover plate. The eyebolt 12 is installed on the carcass for the handling and lifting of the tooling. The above structure is manufactured according to the data set, the profile manufacturing tolerance is ±0.1mm, and the working profile roughness is not higher than Ra1.6.

[0029] During stretch forming, structures such as the cover plate, the side cover plate, and the core are removed, and only the main structures such as the carcass 1 and the partial carcass 2 are retained.

[0030] During manual forming and trimming, the partial carcass 2 is removed, and the carcass is used in conjunction with the cover plate and the side cover plate to form a "J"-shaped structure. The carcass is used in conjunction with the core to form a reinforced curved edge on the web.

[0031] The tooling "milling fixture" can realize the precise milling of the edges and inner holes of the "U" section blank formed by the stretching process and the drilling of assembly holes for subsequent sheet metal forming. Its structural carcass 13 is designed according to the part process data set, that is, the bottom bend of the part and the reinforced bend are unfolded according to the sheet metal unfolding algorithm. Considering the slender structure of the part, in order to prevent the tooling from deforming and tipping over during milling, the bottom of the carcass is widened to form a "convex" structure as a whole. A pressure plate groove is added 40mm from the bottom to fix the tooling on the platform during milling. A reference hole is set at the top of the carcass for tooling alignment and as the coordinate origin during CNC milling. The positioning pin 14 is installed at the top of the carcass for part positioning during milling. In order to ensure that the parts and the fixture fit tightly during milling, a vacuum adsorption device is added inside the carcass, and a sealing strip 15 is laid near the milling edge. The uncoated wire thread sleeve 16 is installed at the position of the carcass about 150mm away from the edge of the part. During milling, it cooperates with the pressing plate to enhance the pressing effect of the blank to prevent the vacuum adsorption device from failing during milling and causing the part position to move. The hanging rod 17 passes through the carcass and is used for the transportation and lifting of the tooling. The vacuum fixture nozzle 18 is connected to the vacuum adsorption device inside the carcass and is used to evacuate the vacuum during milling.

[0032] Furthermore, the above-mentioned milling fixture is manufactured using SAM-900-LX epoxy resin as the surface and SAM910 resin as the base, the manufacturing tolerance of the profile is ±0.1mm, and the roughness of the working profile is not higher than Ra1.6.

[0033] Embodiment 2:

[0034] The specific method of the complex variable curvature skin of the "J"-shaped cross section with reinforced curved edges includes the following steps:

[0035] Step 1: Cutting

[0036] The parts are made of aluminum alloy sheet with material grade 7B04, OB state, thickness of δ1.5mm, size 1750mmX1200mm, where the length direction is parallel to the fiber direction of the sheet, which is conducive to maximize the forming performance of the material during stretching and manual bending.

[0037] Step 2: Stretch forming

[0038] First, use a crane to place the special platform required for stretching in the center of the stretching machine, remove the side cover plate 6, the overall cover plate 7, the core 9 and other structures, and only keep the main structure of the mold 1 and the partial carcass 2 in the center of the platform to ensure that the mold is well fixed to the platform and the stretching direction is consistent with the clamping direction of the jaws; then clean the mold and apply lubricating oil on its surface to allow the material to flow when it is stretched. During stretching, place both ends of the part raw material in the jaws of the stretching machine so that the end contacts the bottom of the jaws to ensure sufficient clamping volume, close the jaws to clamp the raw material, and stretch the jaws through the control system to gradually deform the raw material and approach the mold surface until it fits tightly. The process can be coordinated with the top action on the table. After the stretching is completed, use a wooden hammer or rubber board to knock on the surface of the stretched part to check whether the part is attached to the tire. After the qualified part is stretched for the first time, save the loading and jaw trajectory for subsequent part forming. After the stretching is completed, open the jaws, unload the part from the jaws, and take it out from the top of the mold. Compared with drop forming, in this process, the material flows more evenly on the surface of the flow mold under the tensile force and finally fits with it, so the thickness of the obtained stretched part changes more evenly, the surface quality is better, and it is not easy to wrinkle, rapidly thin the material or even crack due to excessive local deformation in drop forming, which not only improves production efficiency but also reduces labor intensity;

[0039] Step 3: CNC milling

[0040] Preparation before milling: First, use a crane to hoist the milling fixture to the CNC five-axis milling platform, accurately measure the X, Y, Z and processing coordinate origin of the milling fixture through a dial indicator and a ruby ​​probe, and manually adjust the position of the fixture slightly. After it is accurate, fix the milling fixture to the milling platform through a pressure plate; then cut off the clamping part of the stretched "U"-shaped piece and install it to the tire body 13, ensure that the relative position of the profile and the fixture is accurate, and then use the positioning pin 14 to fix it, and install a movable pressure plate at the corresponding position of the uncoated wire screw sleeve 16 to prevent the vacuum adsorption device from failing during milling and causing the part position to move;

[0041] Milling: straighten and align the coordinate system so that the coordinate system of the machine tool coincides with the programming coordinate system, connect the nozzle 18 for the vacuum fixture, turn on the vacuum adsorption equipment, ensure that the parts are tightly adsorbed to the surface of the milling fixture under the action of the sealing strip 15, run the CNC milling program, complete the milling of the outer edge and the inner edge of the expansion hole and the drilling of the assembly hole. After completing the milling, turn off the machine button, clean the aluminum chips on the surface of the parts, and check the edge size of the parts and whether there are any bruises and other mechanical damages on the surface; after completing the above operations, turn off the vacuum adsorption equipment, unload the movable pressure plate, and remove the parts;

[0042] Step 4: Manual Forming

[0043] First, remove the partial carcass 2 of the mold, place the milled "U"-shaped blank on the carcass 1, fix the two ends with special positioning pins 5, and use special mold pins 8 and screws 4 to close the overall cover plate 7 and the side cover plate 6. Use a hammer, a plate hitter and other tools to knock the blank to force the blank to fit the side cover plate to complete the "J"-shaped bending. Then, remove the overall cover plate, place the core in the reinforced bending position, and use an aluminum hammer to knock the core. The core is forced to move downward, and the blank bends under the pressure of the core, thereby completing the reinforced bending. Since the part surface is mainly completed by stretching, the material has good fluidity and small residual stress, which reduces the workload of manual finishing in the later stage. In addition, the core forming sheet is evenly stressed, so the reinforced bending is not easy to crack, thereby reducing the risk of cracks. After completing the above forming, remove the cover plate and check whether the gap between the part and the carcass and the side cover plate meets the requirements of the design drawing. If the gap does not meet the requirements, repeat this process for trimming;

[0044] Step 5: Quenching

[0045] The purpose of quenching the parts is to improve the strength and hardness of the parts. The specific operation is as follows: clean the parts, make sure there is no visible dirt on the surface, and load them into the air furnace heat treatment equipment. When loading the furnace, ensure that the parts are placed in the effective heating area of ​​the air furnace, and there should be gaps between the parts. Close placement, stacking or bundling is not allowed. Quenching temperature range: 465℃~475℃, holding time 30min~45min, after quenching, completely cool the parts in flowing cold water at 10℃~40℃, and the cooling time is not less than 2min;

[0046] Step 6: Finishing

[0047] Place the parts on the mold body and fix them, install the overall cover plate and side cover plate, and perform quenching and deformation trimming manually to ensure that the gap between the parts and the tooling is no more than 0.5mm;

[0048] Step 7: Artificial Aging

[0049] The purpose of artificial aging is to eliminate internal stress and stabilize the structure and size. First, clean the parts to ensure that the surface is dry and free of dirt, oil, grease, etc. Then load the furnace. When all the temperature sensors of the equipment reach the temperature range required by the process, the parts are put into the furnace. They can also be put into the furnace in a cold state, but the furnace temperature recovery time shall not exceed 2h. The parts should be placed in the effective heating area of ​​the equipment. Parts are allowed to be stacked with a stacking thickness of no more than 25mm and a stacking spacing of at least 25mm. Primary aging: Heating temperature range: 115±5℃, aging insulation time: 7h~8h; after the first aging, the parts are not taken out of the furnace and are directly heated to enter the second aging, heating temperature range: 165±5℃, insulation time: 15h~16h. After aging is completed, the parts are cooled by air cooling;

[0050] Step 8: Physical and chemical performance testing

[0051] After aging, the parts are sent to the physical and chemical department for conductivity or hardness inspection according to the standard. The hardness value is 450-530MPa, and the conductivity is ≥21MS / m. If both the conductivity and hardness tests are unqualified, the heat treatment is repeated, and then the test of this step is carried out again until the physical and chemical properties are qualified before entering the subsequent process;

[0052] Complete the above steps to obtain the final shape of the part.

Claims

1. A method for manufacturing a complex skin with a "J"-shaped cross-section and variable curvature with a reinforced curved edge, characterized in that: Here are the steps: The first process is stretch forming; Stretching forming and manual forming share a set of molds. The tooling adopts a detachable structure and can be disassembled and used according to forming requirements to achieve its function; The tooling comprises: a carcass (1), a partial carcass (2), a positioning pin (3), a screw (4), a special positioning pin (5), a side cover plate (6), an integral cover plate (7), a special mold counter pin (8), a core (9), a fixed drill sleeve (10), a movable handle (11), and a lifting eye screw (12); The tooling "mold" can stretch the sheet material into a variable curvature structure of a "U" cross section, and can form the structure into the final shape of the part; the carcass (1) is designed according to the inner profile of the part, and the partial carcass (2) is made into an unfolded state and a detachable structure according to the corresponding position of the "J"-shaped curved edge, and the partial carcass (2) and the carcass (1) are aligned with the positioning pin (3) and fixed with the screw (4), and the special positioning pin (5) is used to position the part on the carcass; the side cover plate (6) is designed according to the inner shape of the "J"-shaped curved edge and is aligned with the carcass (1) by the positioning pin (3). The integral cover plate (7) is aligned with the carcass through a special die pin (8) for clamping and fixing when trimming parts, and a through hole is made at the reinforcing bend to cooperate with the core (9) for reinforcing the bend forming; the core (9) is manufactured according to the outer profile of the reinforcing bend of the part and is used to strengthen the bend forming; a fixed drill sleeve (10) is installed on the cover plate for checking the position of the assembly hole, and a movable handle (11) is installed on the integral cover plate to facilitate the installation and removal of the integral cover plate; a lifting eye screw (12) is installed on the carcass for carrying and lifting the tooling; The second process is CNC milling; The tooling used in the CNC milling process is a "milling fixture", which includes: a structural carcass (13), a positioning pin (14), a vacuum adsorption device and a sealing strip (15), an uncoated steel wire screw sleeve (16), a hanging rod (17), and a nozzle for a vacuum fixture (18); The "milling fixture" can realize the precise milling of the edges and inner holes of the "U" cross-section blank formed by the stretching process and the drilling of assembly holes for subsequent sheet metal forming; the positioning pin (14) is installed on the top of the tire body and is used to position the parts during milling; in order to ensure that the parts and the fixture fit tightly during the milling process, a vacuum adsorption device is added inside the tire body, and a vacuum adsorption device and a sealing strip (15) are laid near the milling edge; the hanging rod (17) passes through the tire body and is used for the transportation and lifting of the tooling; the vacuum fixture is connected to the vacuum adsorption device inside the tire body with a nozzle (18) for vacuuming during the milling process; The third process is manual forming; The tooling used for manual forming is a "mold", which is the same set of tooling used for stretch forming. During manual forming and trimming, a partial carcass (2) is removed, and the carcass is used in conjunction with a cover plate and a side cover plate to form a "J"-shaped structure. The carcass is used in conjunction with a mold core to form a reinforced curved edge on the web.

2. The method for manufacturing a complex skin with a "J"-shaped cross-section and variable curvature with a reinforced curved edge as claimed in claim 1, characterized in that: The carcass (1), partial carcass (2), positioning pins (3), screws (4), special positioning pins (5), side cover plates (6), integral cover plates (7), special counter-die pins (8), cores (9), fixed drill sleeves (10), movable handles (11), and eye screws (12) are manufactured according to a data set, with a manufacturing tolerance of the molding surface of ±0.1 mm and a working molding surface roughness of no higher than Ra1.

6.

3. The method for manufacturing a complex skin with a "J"-shaped cross-section and variable curvature with a reinforced curved edge as claimed in claim 1 or 2, characterized in that: The positioning pin (14), vacuum adsorption device and sealing strip (15), uncoated wire screw sleeve (16), hanging rod (17), and vacuum clamp nozzle (18) are manufactured using SAM-900-LX epoxy resin as the surface and SAM910 resin as the matrix. The manufacturing tolerance of the profile is ±0.1mm, and the roughness of the working profile is not higher than Ra1.

6.

4. The method for manufacturing a complex skin with a "J"-shaped cross-section and variable curvature with a reinforced curved edge as claimed in claim 1 or 2, characterized in that: The structural carcass (13) is in a "convex" structure as a whole, and a pressure plate groove is added at a position 40 mm from the bottom for fixing the tooling on the platform during milling; a reference hole is arranged at the top of the structural carcass (13) for tooling alignment and as a coordinate origin during CNC milling.

5. The method for manufacturing a complex skin with a "J"-shaped cross section and variable curvature with a reinforced curved edge as claimed in claim 3, characterized in that: The structural carcass (13) is in a "convex" structure as a whole, and a pressure plate groove is added at a position 40 mm from the bottom for fixing the tooling on the platform during milling; a reference hole is arranged at the top of the structural carcass (13) for tooling alignment and as a coordinate origin during CNC milling.

6. The method for manufacturing a complex skin with a "J"-shaped cross section and variable curvature with a reinforced curved edge as claimed in claim 1, 2 or 5, characterized in that: The uncoated wire screw sleeve (16) is installed at a position of the carcass about 150 mm away from the edge of the part, and cooperates with the pressing plate to enhance the pressing effect of the blank during milling, so as to prevent the vacuum adsorption device from failing during milling and causing the part position to move.

7. The method for manufacturing a complex skin with a "J"-shaped cross section and variable curvature with a reinforced curved edge as claimed in claim 3, characterized in that: The uncoated wire screw sleeve (16) is installed at a position of the carcass about 150 mm away from the edge of the part, and cooperates with the pressing plate to enhance the pressing effect of the blank during milling, so as to prevent the vacuum adsorption device from failing during milling and causing the part position to move.

8. The method for manufacturing a complex skin with a "J"-shaped cross section and variable curvature with a reinforced curved edge as claimed in claim 4, characterized in that: The uncoated wire screw sleeve (16) is installed at a position of the carcass about 150 mm away from the edge of the part, and cooperates with the pressing plate to enhance the pressing effect of the blank during milling, so as to prevent the vacuum adsorption device from failing during milling and causing the part position to move.

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