A method for forming and milling an integrated skin
By integrating forming and milling processes, combined with heat treatment fixtures and special molds, the problems of low precision, low efficiency and high cost in traditional skin processing are solved, and high-precision and high-efficiency skin processing is achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHENYANG AIRCRAFT CORP
- Filing Date
- 2025-08-01
- Publication Date
- 2026-06-26
AI Technical Summary
In traditional skinning processes, the separation of forming and milling operations results in low processing accuracy, low efficiency, and high cost, and makes it difficult to guarantee the shape consistency and positioning accuracy of the skin.
The process employs an integrated forming and milling process, using heat treatment fixtures and special molds. By combining finite element analysis and real-time monitoring data, stretching and milling can be performed on the same mold. The machining accuracy is ensured by an adaptive clamping and cooling system, and the machining parameters are adjusted in real time using a CNC system and sensors.
It improves the precision and efficiency of skin processing, reduces production costs, reduces cumulative errors and process transfers, and ensures the high quality and consistency of the skin.
Smart Images
Figure CN120644931B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of aerospace sheet metal processing technology, and relates to the forming and shape processing of skin-type parts. Background Technology
[0002] In the aerospace field, the skin, as a crucial component of the aircraft's structure, directly impacts aircraft performance and safety through its machining precision and quality. Traditional skin manufacturing processes typically employ two different sets of molds for forming and milling, resulting in cumbersome procedures and high costs. During the forming stage, methods such as mold stretching and rolling are generally used to achieve the designed curved surface shape of the sheet metal. However, this approach presents several problems. Due to the manufacturing precision of the molds and wear during use, it is difficult to guarantee a high degree of consistent shape accuracy in every formed skin. Furthermore, the forming process generates complex residual stress distributions within the sheet metal, which can lead to skin deformation during subsequent processing and use, affecting product quality.
[0003] During the milling stage, the formed skin is fixed on a milling machine for milling to obtain the required shape, hole system, and other features. However, due to the irregular shape of the formed skin, it is difficult to ensure its positioning accuracy during clamping. Improper clamping can lead to displacement and vibration of the skin during milling, thus affecting the milling accuracy. In addition, multiple transfers and repositionings are required between the two processing steps, which not only increases the processing cycle but also introduces more cumulative errors.
[0004] Therefore, there is an urgent need for an integrated skin processing method that can organically combine forming and milling processes to improve processing accuracy and efficiency and reduce production costs. Summary of the Invention
[0005] The purpose of this invention is to provide an integrated forming and milling method for skin processing, in order to solve the problems of low processing accuracy, low production efficiency and high cost caused by the separation of forming and milling processes in existing skin processing technology, and to achieve high-precision, high-efficiency and high-quality skin processing.
[0006] According to one aspect of this application, a method for forming and milling an integrated skin processing method is provided, comprising the following steps:
[0007] I. Raw material preparation: Based on the design requirements of the skin, select suitable metal sheets as raw materials, and conduct strict testing on the chemical composition and mechanical properties of the sheets to ensure that they meet the standards for use in aerospace components. Pre-treat the surface of the metal sheets to remove impurities such as oil and oxide layers, improve the surface quality of the metal sheets, and lay a good foundation for subsequent processing to obtain pre-treated metal sheets.
[0008] 2. Use heat treatment fixtures to clamp the metal sheet for quenching to reduce deformation and residual stress, and obtain the quenched metal sheet.
[0009] 3. Stretching forming: A stretching control algorithm is adopted, combined with finite element analysis and real-time monitoring data from the CNC skin stretching machine, to achieve precise control of the stretching process and obtain the formed metal sheet.
[0010] 4. Mill the outer shape to obtain the skin.
[0011] The heat treatment fixture consists of a frame (1), a lower clamping plate (2), an upper clamping plate (3), and an adaptive clamping block (4).
[0012] The frame (1) is made of high-strength heat-resistant alloy material with a heat resistance temperature of not less than 1000℃ and a rectangular shape to facilitate the placement of pre-treated metal plates.
[0013] The frame (1) is fitted with an upper clamping plate (3) and a lower clamping plate (2) on its upper and lower sides;
[0014] The upper clamping plate (3) and the lower clamping plate (2) are connected by several adjustable adaptive clamping blocks (4). The height of the adaptive clamping blocks (4) can be adjusted according to the width of the pre-treated metal plate. The adaptive clamping blocks (4) can also adapt to the clamping requirements of pre-treated metal plates of different thicknesses, so as to achieve uniform clamping of the pre-treated metal plate and avoid deformation of the pre-treated metal plate due to uneven force during the quenching process.
[0015] The upper clamping plate (3) and the lower clamping plate (2) are provided with universal positioning grooves and positioning pins. By adjusting the position of the positioning pins in the positioning grooves, the pre-treated metal plates of different sizes and shapes can be positioned quickly and accurately, thus improving the versatility of the fixture.
[0016] The heat treatment fixture is equipped with cooling pipes arranged in a mesh pattern, which ensures that the coolant is evenly sprayed onto the surface of the pretreated metal sheet, achieving uniform cooling of the sheet and improving the quenching quality.
[0017] Before stretching, the stretching process is simulated and analyzed using finite element software to predict the deformation and required tensile force at different locations. Based on the simulation results, a stretching process curve is developed, including the relationship between tensile force, stretching speed, and stretching path over time. During the stretching process, force sensors, displacement sensors, and strain sensors installed on the stretching equipment are used to monitor the stress, deformation, and displacement of the quenched metal sheet in real time. The stretching control algorithm dynamically adjusts the stretching process curve based on the real-time monitoring data to ensure that the quenched metal sheet is always under optimal stress during the stretching process, avoiding overstretching or understretching.
[0018] Special molds are used in the stretching and milling of the shape.
[0019] The special mold consists of a support body (5), a lower positioning part (6), a support rod (7), a mold bracket (8), a stretching surface (9), a positioning plate (10), a rotating wheel (11), a transmission shaft sleeve (12), a milling surface (13), a vacuum nozzle (14), a reference hole (15), and a clamping threaded hole (16).
[0020] The support (5) is made of Q235 or metal of the same strength and is used for support during stretching and milling processes;
[0021] A row of lower positioning parts (6) is installed on each side of the support body (5). The number is calculated according to the length of the support body (5), and is usually set to be installed at 300mm intervals.
[0022] A support rod (7) is installed on the lower positioning member (6). The support rod (7) is used to ensure the position of the stretchable surface 9 in the horizontal direction and prevent it from rotating.
[0023] The stretchable surface 9 is supported by four mold brackets (8). The mold brackets (8) are installed on both sides of the support body (5) without affecting the stretching direction. Two mold brackets are installed in each direction.
[0024] Two to three positioning plates (10) are installed on the surface of the stretch-shaped surface 9 for drilling positioning holes after the quenched metal sheet is formed, for use in the next process of milling.
[0025] A rotating wheel (11) is installed on each side of the stretching surface 9 in the non-stretching direction. The function of the rotating wheel (11) is to rotate the stretching surface 9 by 180° after the first forming process is completed, and then use another surface to perform the next process.
[0026] To save effort during rotation, each rotating wheel (11) is equipped with a transmission shaft sleeve (12). The transmission shaft sleeve (12) can use multiple gears or other structures to transmit torque, reduce the loading force during rotation, and facilitate direction change.
[0027] During the milling process, the special mold uses a hex wrench to open all the support rods (7) on both sides, and then rotates the rotating wheel (11) to rotate the support body (5) 180°.
[0028] The other side of the stretching surface (9) is the milling surface (13). A vacuum nozzle (14) is installed on the side of the milling surface (13) for installing a rubber tube and a vacuum pump during the milling process to provide adsorption force, ensuring that each position of the formed metal sheet can get sufficient adsorption loading force so that it fits tightly with the milling surface (13).
[0029] After the formed metal sheet is tightly adsorbed with the mold, a pressure block and a threaded pin are used to tighten the threaded pin into the pressing threaded hole (16) so that the edge of the formed metal sheet to be milled is pressed tightly to achieve the milling state.
[0030] A coordinate system is established using two reference holes (15) on the surface of the milled profile (13). The two reference holes (15) should be set on both sides of the profile and kept on a horizontal plane to reduce errors and improve machining accuracy. The machining steps of the metal sheet after forming are completed using the programmed procedure, so that one mold can complete two machining steps, reduce multiple positioning in the middle, and reduce the number of tooling.
[0031] The skin also needs to undergo inspection and control. Non-contact measuring equipment, such as laser scanners and coordinate measuring machines, is used to comprehensively inspect the skin's dimensions, surface shape, and key features. The inspection data is compared and analyzed with a digital model to determine if the processing accuracy meets design requirements. For products that fail inspection, data analysis identifies the causes, such as improper processing parameter settings or equipment malfunctions, and corresponding corrective measures are taken for rework. A comprehensive quality traceability system is established to record information such as parameters, operators, and inspection data for each processing stage. This allows for rapid and accurate tracing of the root cause of quality problems, enabling effective improvement measures and continuous enhancement of processing quality.
[0032] The advantages of this application are:
[0033] The forming and milling processes are integrated into a single mold, avoiding multiple transfers and repositionings between processes, greatly shortening the processing cycle, improving production efficiency, and reducing production costs. Attached Figure Description
[0034] Figure 1 Structure diagram of heat treatment fixture.
[0035] Figure 2 This is a structural diagram of a special mold.
[0036] Figure 3 This is a structural diagram of a special mold.
[0037] The components include: 1. Frame; 2. Lower clamping plate; 3. Upper clamping plate; 4. Adaptive clamping block; 5. Support body; 6. Lower positioning component; 7. Support rod; 8. Mold bracket; 9. Stretching surface; 10. Positioning plate; 11. Rotating wheel; 12. Transmission shaft sleeve; 13. Milling surface; 14. Vacuum nozzle; 15. Reference hole; and 16. Pressing threaded hole. Detailed Implementation
[0038] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.
[0039] Example 1
[0040] The first step is to quench the sheet metal.
[0041] Sheet clamping: The aluminum alloy sheet is placed on the lower clamping plate 2, and the sheet is accurately positioned by adjusting the position of the positioning pin in the positioning groove. Then, the upper clamping plate 3 descends, and the self-adaptive clamping block 4 automatically fits against the surface of the sheet under the action of the elastic connector, achieving uniform clamping of the sheet.
[0042] Quenching Operation: Start the quenching equipment to heat and cool the aluminum alloy sheet. During heating, the clamps ensure the stability of the sheet; during cooling, coolant is evenly sprayed onto the sheet surface through cooling pipes, achieving rapid and uniform cooling. Sheet Removal: After quenching, release the upper clamp and remove the aluminum alloy sheet, completing the entire quenching process.
[0043] The second step is stretching and shaping.
[0044] The cut aluminum alloy sheet is stretched and shaped using a skin stretching machine. To ensure the sheet adheres well to the mold after stretching, the aluminum alloy sheet is quenched, and the forming process is completed within 20 minutes after quenching. During the forming process, lubricating oil should be applied to the surface of the stretching profile 9 to improve the stretching of the sheet during the forming process and reduce the friction between the part surface and the tooling.
[0045] Pre-stretching stage: The metal sheet to be stretched is fixed on the stretching equipment, and a small initial tensile force is applied to the sheet to induce preliminary plastic deformation, eliminate residual stress inside the sheet, and simultaneously allow the sheet to initially fit against the stretching profile 9, preparing for subsequent formal stretching. During this stage, precise control of the stretching speed and tensile force ensures uniform stress distribution across all parts of the sheet.
[0046] Zonal stretching stage: Based on the shape and design requirements of the skin, the sheet metal is divided into multiple zones. Different stretching parameters, such as stretching speed, tensile force, and stretching direction, are used for different zones. For zones with complex shapes and high deformation requirements, the stretching force and number of stretching cycles are appropriately increased to ensure that the zone can deform sufficiently; for relatively flat zones, a relatively smaller stretching force and a faster stretching speed are used to improve overall stretching efficiency. By controlling the stretching in zones, each part of the sheet metal deforms in a predetermined manner, effectively improving the uniformity of the skin thickness distribution.
[0047] Synchronous Compensation Stretching Stage: During the stretching process, the deformation of the sheet material is monitored in real time, and strain data of various parts of the sheet are acquired using sensors. Based on the monitoring data, the stretching equipment is adjusted in real time, and additional compensation stretching is applied to areas with insufficient deformation to ensure uniform deformation of the entire sheet material and reduce defects such as wrinkles and springback caused by deformation differences. Simultaneously, by adjusting the shape and position of the stretching die, an appropriate counterforce is applied to the sheet material to further optimize its deformation state.
[0048] Post-processing stage: After stretching, the skin undergoes heat treatment and shaping. Heat treatment eliminates residual stress caused by stretching inside the skin, improving its mechanical properties; shaping fine-tunes the shape of the skin to better meet design requirements and ensure dimensional accuracy.
[0049] Simultaneously, based on the stretching process curve obtained from finite element simulation analysis, parameters such as stretching force, stretching speed, and stretching path are input into the control system of the stretching equipment. The stretching equipment is started, and the stretching die begins stretching the skin. During the stretching process, force sensors monitor the stretching force in real time, displacement sensors monitor the stretching displacement of the skin, and strain sensors monitor the strain of the skin. The intelligent stretching control algorithm compares and analyzes the real-time monitoring data with the preset stretching process curve. When deviations occur between the monitored data and the process curve, the algorithm automatically adjusts the operating parameters of the stretching equipment, such as increasing or decreasing the stretching force or adjusting the stretching speed, to ensure that the skin is stretched according to the predetermined process curve.
[0050] The third step is milling. The stretched surface 9 is rotated 180° by the rotation of the rotating wheel 11, and then all the support rods 7 on both sides are tightened to ensure it is level. A coordinate system is established for the reference hole 15 using a CNC machine tool probe, completing the pre-milling process preparation. The skin, processed in the above steps, is then placed on the milling surface 13. The vacuum adsorption system is activated to ensure the skin is fully attached to the worktable, and the threaded pins are tightened to firmly attach the clamping block to the sheet metal, preventing vibration during milling. Based on the material type of the skin (e.g., aluminum alloy 7075) and the shape design requirements, the CNC system retrieves the corresponding cutting parameters from the cutting parameter database, such as a cutting speed of 2000 m / min, a feed rate of 0.15 mm / r, and a depth of cut of 0.5 mm. The milling equipment is started, and the new coated carbide end mill begins milling the skin. During the processing, the cutting force sensor, vibration sensor, and position sensor collect data in real time and transmit it to the monitoring and error compensation system. When the cutting force sensor detects a sudden increase of 15% in the cutting force, the system determines that there may be tool wear or abnormal cutting conditions, automatically reduces the cutting speed by 10%, and adjusts the feed rate to restore the cutting force to the normal range, ensuring the stability and accuracy of the machining process.
[0051] The fourth step is quality inspection. After milling, a high-precision coordinate measuring machine is used to comprehensively inspect the milled shape of the skin. According to the design drawings, the skin's outline, key dimensions, and surface accuracy are measured. The measurement data are compared and analyzed with the design standards. For minor deviations (such as dimensional deviations within ±0.3mm), the CNC system is used to fine-tune and compensate the machining equipment to ensure that the milled skin shape fully meets the manufacturing standards.
[0052] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions made by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.
Claims
1. A method for integrated forming and milling of skin processing, characterized in that, Includes the following steps: I. Raw material preparation: Based on the design requirements of the skin, select suitable metal sheets as raw materials, and conduct strict testing on the chemical composition and mechanical properties of the sheets to ensure that they meet the standards for use in aerospace components. Pre-treat the surface of the metal sheets to remove oil and oxide layers, improve the surface quality of the metal sheets, and lay a good foundation for subsequent processing to obtain pre-treated metal sheets.
2. Use heat treatment fixtures to clamp the metal sheet for quenching to reduce deformation and residual stress, and obtain the quenched metal sheet.
3. Stretching and forming: A stretching control algorithm is adopted, combined with finite element analysis and real-time monitoring data from the CNC skin stretching machine, to achieve precise control of the stretching process and obtain the stretched metal sheet. IV. Mill the outer shape to obtain the skin; Special molds are used in the stretching and milling of the shape; The special mold consists of a support body (5), a lower positioning part (6), a support rod (7), a mold bracket (8), a stretching surface (9), a positioning plate (10), a rotating wheel (11), a transmission shaft sleeve (12), a milling surface (13), a vacuum nozzle (14), a reference hole (15), and a clamping threaded hole (16). The support (5) is made of Q235 or metal of the same strength and is used for support during stretching and milling processes; A row of lower positioning parts (6) is installed on each side of the support body (5). The number is calculated according to the length of the support body (5), and is usually set to be installed at 300mm intervals. A support rod (7) is installed on the lower positioning member (6). The function of the support rod (7) is to ensure the position of the stretch-shaped surface (9) in the horizontal direction and prevent it from rotating. The stretchable surface (9) is supported by four mold brackets (8). The mold brackets (8) are installed on both sides of the support body (5) without affecting the stretching direction. Two mold brackets are installed in each direction. Two to three positioning plates (10) are installed on the surface of the stretch profile (9) for drilling positioning holes after the quenched metal sheet is formed, for use in the next milling process; A rotating wheel (11) is installed on each side of the non-stretching direction of the stretching surface (9). The function of the rotating wheel (11) is to rotate the stretching surface (9) by 180° after the stretching forming process is completed, and then use the milling surface (13) to perform the next process. To save effort during rotation, each rotating wheel (11) is fitted with a drive shaft sleeve (12).
2. The integrated forming and milling skin processing method according to claim 1, characterized in that, The heat treatment fixture consists of a frame (1), a lower clamping plate (2), an upper clamping plate (3), and an adaptive clamping block (4).
3. The integrated forming and milling skin processing method according to claim 2, characterized in that, The frame (1) is made of high-strength heat-resistant alloy material with a heat resistance temperature of not less than 1000℃ and a rectangular shape to facilitate the placement of pre-treated metal plates. The frame (1) is fitted with an upper clamping plate (3) and a lower clamping plate (2) on the top and bottom. The upper clamping plate (3) and the lower clamping plate (2) are connected by several adjustable adaptive clamping blocks (4). The height of the adaptive clamping blocks (4) can be adjusted according to the width of the pre-treated metal plate. The adaptive clamping blocks (4) can also adapt to the clamping requirements of pre-treated metal plates of different thicknesses, so as to achieve uniform clamping of the pre-treated metal plate and avoid deformation of the pre-treated metal plate due to uneven force during the quenching process. The upper clamping plate (3) and the lower clamping plate (2) are provided with universal positioning grooves and positioning pins. By adjusting the position of the positioning pins in the positioning grooves, the pre-treated metal plates of different sizes and shapes can be positioned quickly and accurately, which improves the versatility of the fixture.
4. The integrated forming and milling skin processing method according to claim 3, characterized in that, The heat treatment fixture is equipped with cooling pipes arranged in a mesh pattern, which ensures that the coolant is evenly sprayed onto the surface of the pretreated metal sheet, achieving uniform cooling of the sheet and improving the quenching quality.
5. The integrated forming and milling skin processing method according to claim 1, characterized in that, Before stretching, the stretching process is simulated and analyzed using finite element software to predict the deformation of different parts and the required tensile force. Based on the simulation results, a stretching process curve is developed, including the relationship between tensile force, stretching speed and stretching path over time. During the stretching process, force sensors, displacement sensors, and strain sensors installed on the stretching equipment are used to monitor the stress, deformation, and displacement of the quenched metal sheet in real time. The stretching control algorithm dynamically adjusts the stretching process curve based on the real-time monitoring data to ensure that the quenched metal sheet is always in the optimal stress state during the stretching process, avoiding overstretching or understretching.
6. The integrated forming and milling skin processing method according to claim 1, characterized in that, During the milling process, the special mold uses a hex wrench to open all the support rods (7) on both sides, and then rotates the rotating wheel (11) to rotate the support body (5) 180°. The other side of the stretching surface (9) is the milling surface (13). A vacuum nozzle (14) is installed on the side of the milling surface (13) to install a rubber tube and a vacuum pump during the milling process, provide adsorption force, and ensure that each position of the stretched metal sheet can get sufficient adsorption loading force so that it fits tightly with the milling surface (13). After the stretched metal sheet is tightly adsorbed to the mold, a pressure block and a threaded pin are used to tighten the threaded pin into the pressing threaded hole (16) so that the edge of the stretched metal sheet is pressed tightly to achieve the milling state. A coordinate system is established using two reference holes (15) on the surface of the milled profile (13). The two reference holes (15) should be set on both sides of the milled profile (13) and kept on a horizontal plane to reduce errors and improve processing accuracy. The processing steps of the metal sheet after stretching are completed using the programmed program, so that one mold can complete two processing steps, reduce multiple positioning in the middle, and reduce the number of tooling.
7. The integrated forming and milling skin processing method according to claim 1, characterized in that, The skin also needs to undergo testing and control. Non-contact measuring equipment is used to comprehensively test the skin's dimensions, surface shape, and key features. The test data is then compared and analyzed with the digital model to determine whether the processing accuracy meets the design requirements.