Forming method and device for eccentric two-roller flexible roll bending of variable-curvature metal sheet

Abstract

The invention provides a forming method and device for variable-curvature metal sheet eccentric type two-roller flexible roll bending, and relates to the technical field of metal sheet forming. The forming method comprises the steps that S1, a metal sheet is placed between a rigid roller and a flexible roller; s2, loading displacement from the rigid roller to the direction of the flexible roller; s3, the flexible roller is driven to rotate around the center of the mandrel, so that the bending radius of the metal sheet is dynamically adjusted in the feeding process, and a variable-curvature contour is formed after rebounding; s4, calculating the curvature radius of a neutral layer before and after the plate rebounds, and optimizing the forming precision; and S5, the rigid roller is reset, and forming of the metal sheet is completed. The curvature is dynamically adjusted through rotation of the eccentric flexible roller in the eccentric flexible roller-rigid roller asymmetric forming mechanism, non-modeling variable-curvature forming of a metal plate is achieved, high-efficiency and high-precision forming of a variable-curvature thin plate is achieved in combination with parameterization regulation and control, and the method is suitable for manufacturing of aerospace complex-curvature parts.

Description

Technical Field

[0001] The present invention relates to the technical field of metal sheet forming, and in particular to a forming method and a device for eccentric two-roller flexible rolling bending of a variable-curvature metal sheet. Background Art

[0002] In the aerospace manufacturing industry, due to the highly customized nature of products, sheet metal bending parts are generally produced in a variety of varieties and small batches. Traditional roll bending processes face significant technical limitations: (1) Existing two-roller roll bending devices rely on fixed curvature molds, resulting in frequent mold changes for parts with different curvatures and poor production flexibility; (2) The mold cost is too high in small batch production, resulting in poor economic efficiency; (3) Complex curvature parts require multiple forming passes, resulting in low processing efficiency.

[0003] Therefore, it is necessary to propose a forming method and device for eccentric two-roller flexible rolling bending of variable curvature metal sheets. Through a dynamically adjustable eccentric roller system structure, moldless continuous curvature forming can be achieved, which is particularly suitable for the manufacture of thin-walled parts with variable curvature characteristics such as spacecraft skins and aircraft engine special-shaped ducts. Summary of the Invention

[0004] In order to solve the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a forming method and device for eccentric two-roller flexible rolling bending of variable-curvature metal sheets, and dynamically adjust the curvature by rotating the eccentric flexible roller in the eccentric flexible roller-rigid roller asymmetric forming mechanism to achieve moldless variable-curvature forming of the metal sheet, which improves the efficiency of the thin plate rolling bending process compared with traditional multi-pass forming; adopts flexible processing with coordinated control of multiple parameters, and adapts to the forming requirements of metal sheets with different geometric shapes by adjusting each combination parameter, breaking through the curvature limitation of traditional fixed molds; adopts modular quick-change flexible rollers, and realizes rapid separation and assembly of the flexible rollers and the device through mechanical linkage, meeting the needs of replacing the flexible rollers when they reach the end of their service life or producing metal sheets with different geometric parameters.

[0005] Specifically, on one hand, the present invention provides a forming method of a variable curvature metal sheet by eccentric two-roller flexible rolling, characterized in that it comprises the following steps: S1, placing the metal sheet between a rigid roller and a flexible roller; S2, driving the rigid roller to load a displacement L in the direction of the flexible roller by a lifting hydraulic cylinder, causing the metal sheet to undergo initial bending deformation; S3, drive the flexible roller to rotate clockwise around the center of the mandrel at a speed of V, driving the metal sheet to feed, the eccentricity between the center of the mandrel and the center of the flexible roller is e, and the value range of e is 0.01 to , the metal sheet dynamically changes its bending radius during the feeding process and forms a variable curvature profile after springback; Flexible roller rotation After the angle is set, the metal sheet with variable curvature profile is obtained, and the pressing amount L e , the specific expression of polyurethane rubber thickness H is: ; ; in, is the loading displacement of the flexible roller to the rigid roller, is the diameter of the flexible roller, e is the eccentricity between the center of the flexible roller and the center of the core shaft, and d0 is the core diameter of the flexible roller; S4. Under plane strain conditions, the curvature radius of the neutral layer of the metal sheet before springback is obtained The expression: ; At the same time, the curvature radius of the neutral layer of the metal sheet after unloading and rebound is obtained The expression: ; in, is the downward pressure, is the thickness of polyurethane rubber, is the elastic modulus of the plate, is the material constant of the plate material, is the power strengthening coefficient of the plate material, is the plate thickness, is the Poisson's ratio of the plate material, is the elastic modulus of the polyurethane rubber layer of the flexible roller, is the rigid roller radius, is the elastic modulus of the rigid roller.

[0006] S5. The flexible roller is moved away from the rigid roller by a displacement L1 through the lifting hydraulic cylinder to complete the reset.

[0007] Preferably, the flexible roller is a roller shaft of cured polyurethane rubber on the outside of a rigid core shaft, and the thickness of the polyurethane rubber layer is eccentrically distributed.

[0008] Preferably, the flexible roller has the freedom to rotate only about the center, and the rigid roller has the freedom to rotate about the core axis and to move vertically.

[0009] Preferably, the eccentricity e between the center of the core shaft and the center of the flexible roller, the hardness of the polyurethane rubber, the diameter of the rigid roller, the diameter of the flexible roller, the diameter of the core shaft, and the eccentricity of the core shaft and the flexible roller are changed to achieve roll bending of metal sheets with different curvature profiles.

[0010] Preferably, the positions of the axis of the flexible roller core and the axis of the rigid roller can be adjusted to meet the needs of roll-bending metal sheets with different curvature profiles.

[0011] Preferably, the metal sheet includes materials that are spray-painted, electroplated, multi-layered, have a protective layer, have embossing, and have a polished surface.

[0012] On the other hand, the present invention provides a forming device for eccentric two-roller flexible rolling bending of variable curvature metal sheets, which includes a drive assembly, an upper roller support assembly and a quick-change assembly. The drive assembly includes a frame, a drive motor, a reducer, a flexible roller, a hydraulic cylinder and a rigid roller. The drive motor and the reducer are both connected to the frame. The first end of the flexible roller is connected to the output shaft of the drive motor through the reducer and the coupling. The second end of the flexible roller is rotatably connected to the frame. The fixed end of the hydraulic cylinder is connected to the frame. The first end of the rigid roller is connected to the output end of the hydraulic cylinder through a bearing seat. The second end of the rigid roller is slidably connected to the frame through the bearing seat. The upper roller support assembly is arranged above the frame, and the quick-change assembly is arranged on both sides of the flexible roller.

[0013] Preferably, the upper roller support assembly includes a crossbeam, a bracket, a pin and a friction roller. Both ends of the crossbeam are connected to the frame, the brackets are evenly distributed below the crossbeam, the friction roller is rotatably connected to the bracket through the pin, and the friction roller is rollingly engaged with the rigid roller.

[0014] Preferably, the quick-change assembly includes a coupling joint, a first open shaft seat, a fixing pin and a second open shaft seat, the coupling joint is connected to the flexible roller through the fixing pin and the first open shaft seat, and the end of the flexible roller is connected to the second open shaft seat through the fixing pin.

[0015] Preferably, the rotation axis of the flexible roller and the rotation axis of the rigid roller are parallel.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a forming method for eccentric two-roller flexible rolling of variable-curvature metal sheets. The curvature is dynamically adjusted by rotating the eccentric flexible roller in an eccentric flexible roller-rigid roller asymmetric forming mechanism, thereby realizing moldless variable-curvature forming of the metal sheet. Compared with traditional multi-pass forming, the efficiency of the sheet rolling process is improved.

[0017] The forming method of the variable curvature metal sheet by eccentric two-roller flexible rolling bending of the present invention adopts flexible processing with coordinated control of multiple parameters. By adjusting the combined parameters of the polyurethane rubber hardness, the rigid roller diameter, the flexible roller diameter and the core shaft diameter, it adapts to the forming requirements of metal sheets with different geometric shapes, breaks through the curvature limitation of traditional fixed molds, and realizes "one machine, multiple shapes" processing.

[0018] The present invention provides a forming device for eccentric two-roller flexible rolling bending of variable curvature metal sheets, which adopts modular quick-change flexible rollers and realizes rapid separation and assembly of the flexible rollers and the device through mechanical linkage, thereby meeting the needs of replacing the flexible rollers when their service life has reached the end or producing metal sheets with different geometric shape parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a flow chart of the forming method of the variable curvature metal sheet by eccentric two-roller flexible rolling bending according to the present invention; Figure 2 A schematic diagram showing the forming process of the eccentric two-roller flexible rolling bending method for a variable curvature metal sheet according to the present invention; Figure 3 Schematic diagram of the overall structure of the eccentric two-roller flexible roll-bending device for metal sheets with variable curvature according to the present invention; Figure 4 It is a schematic diagram of the overall side view of the forming device of the present invention; Figure 5 Schematic diagram of the structure of the upper roller support assembly in the forming device of the present invention; Figure 6 It is a structural schematic diagram of the quick assembly in the forming device of the present invention.

[0020] Main reference numerals: 1. Drive assembly; 11. Frame; 12. Drive motor; 13. Reducer; 14. Flexible roller; 141. Rigid core shaft; 142. Polyurethane rubber; 15. Lifting hydraulic cylinder; 16. Rigid roller; 2. Upper roller support assembly; 21. Crossbeam; 22. Bracket; 23. Pin; 24. Friction roller; 3. Quick-change assembly; 31. Coupling joint; 32. First open-type shaft seat; 33. Fixing pin; 34. Second open-type shaft seat. DETAILED DESCRIPTION

[0021] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0022] like Figure 1 and Figure 2 As shown, the present invention provides a forming method of eccentric two-roller flexible rolling bending of a variable curvature metal sheet, which comprises the following steps: S1, placing the metal sheet between a rigid roller and a flexible roller; S2, driving the rigid roller to load a displacement L in the direction of the flexible roller by a lifting hydraulic cylinder, causing the metal sheet to undergo initial bending deformation; S3, drive the flexible roller to rotate clockwise around the center of the mandrel at a speed of V, driving the metal sheet to feed, the eccentricity between the center of the mandrel and the center of the flexible roller is e, and the value range of e is 0.01 to , the metal sheet dynamically changes its bending radius during the feeding process and forms a variable curvature profile after springback; Flexible roller rotation After the angle is set, the metal sheet with variable curvature profile is obtained, and the pressing amount L e , the specific expression of polyurethane rubber thickness H is: ; ; in, is the loading displacement of the flexible roller to the rigid roller, is the diameter of the flexible roller, e is the eccentricity between the center of the flexible roller and the center of the core shaft, and d0 is the core diameter of the flexible roller; S4. Under plane strain conditions, based on the classical elastic-plastic theory and Hertz contact theory, the curvature radius of the neutral layer of the metal sheet before springback is obtained. The expression: ; According to the classical springback theory, the curvature radius of the neutral layer of the metal sheet after unloading and rebound can be obtained: The expression: ; in, is the downward pressure, is the thickness of polyurethane rubber, is the elastic modulus of the plate, is the material constant of the plate material, is the power strengthening coefficient of the plate material, is the plate thickness, is the Poisson's ratio of the plate material, is the elastic modulus of the polyurethane rubber layer of the flexible roller, is the rigid roller radius, is the elastic modulus of the rigid roller.

[0023] S5. The flexible roller is moved away from the rigid roller by a displacement L1 through the lifting hydraulic cylinder to complete the reset.

[0024] The flexible roller 14 is a roller shaft with a rigid core shaft 141 and a cured polyurethane rubber 142 , and the thickness of the polyurethane rubber layer is eccentrically distributed.

[0025] The flexible roller only has the freedom to rotate around the center, while the rigid roller has the freedom to rotate around the core axis and move vertically.

[0026] By changing the process parameters of the eccentric distance e between the center of the mandrel and the center of the flexible roller, the hardness of the polyurethane rubber, the diameter of the rigid roller, the diameter of the flexible roller, the diameter of the mandrel, and the eccentricity of the mandrel and the flexible roller, the roll bending of metal sheets with different curvature profiles can be achieved.

[0027] The center of the flexible roller core and the center of the rigid roller may not be distributed up and down, so as to meet the requirements of roll bending forming of metal sheets with different curvature profile changes.

[0028] On the other hand, Figures 2 to 6As shown, the present invention provides a forming device for eccentric two-roller flexible rolling bending of variable curvature metal sheets, which includes a drive assembly 1, an upper roller support assembly 2 and a quick-change assembly 3. The drive assembly 1 includes a frame 11, a drive motor 12, a reducer 13, a flexible roller 14, a hydraulic cylinder 15 and a rigid roller 16. The drive motor 12 and the reducer 13 are both connected to the frame 11. The first end of the flexible roller 14 is connected to the output shaft of the drive motor 12 through the reducer 13 and a coupling. The second end of the flexible roller 14 is rotatably connected to the frame 11. The fixed end of the hydraulic cylinder 15 is connected to the frame 11. The first end of the rigid roller 16 is connected to the output end of the hydraulic cylinder 15 through a bearing seat. The second end of the rigid roller 16 is slidably connected to the frame 11 through a bearing seat. The upper roller support assembly 2 is arranged above the frame 11, and the quick-change assembly 2 is arranged on both sides of the flexible roller 14.

[0029] The upper roller support assembly 2 includes a crossbeam 21, a bracket 22, a pin 23, and a friction roller 24. The ends of the crossbeam 21 are connected to the frame 11, and the brackets 22 are evenly distributed below the crossbeam 21. The friction roller 24 is rotatably connected to the bracket 22 via the pin 23, and the friction roller 24 is in rolling engagement with the rigid roller 16.

[0030] The quick-change assembly 3 includes a coupling 31, a first open-type shaft seat 32, a fixing pin 33, and a second open-type shaft seat 34. The coupling 31 is connected to the flexible roller 14 via the fixing pin 33 and the first open-type shaft seat 34. The end of the flexible roller 14 is connected to the second open-type shaft seat 34 via the fixing pin 33. The quick-change assembly 3 allows the flexible roller 14 to be separated from the other components of the device, allowing for rapid replacement of the flexible roller 14 to meet the needs of replacing the flexible roller 14 at the end of its service life or producing metal sheets with different geometric parameters. Example The following is a further description of the forming method and device of the variable curvature metal sheet eccentric two-roller flexible rolling bending of the present invention in conjunction with the embodiments: Take an aluminum alloy sheet metal with a length of 500 mm, a width of 1000 mm, and a wall thickness of 1.5 mm as an example. The mechanical properties of the sheet metal are: elastic modulus of 210 GPa, yield strength of 270 MPa, plastic modulus of 1790 MPa, and Poisson's ratio of 0.33.

[0031] This process is achieved by: S1, placing the metal sheet between a rigid roller and a flexible roller; S2. Start the lifting hydraulic cylinder at the end of the frame to drive the flexible roller to load one end of the rigid roller, with a loading displacement of 2 mm; S3. Start the motor. Driven by the coupling and the main reducer, the flexible roller rotates counterclockwise around the center of the core shaft at a speed of 0.52 rad / s. The metal sheet is bent and deformed between the rigid roller and the flexible roller. The bending radius of the metal sheet is different at different times, and the curvature radius after unloading and rebounding is different. After the flexible roller rotates 180 degrees, a metal sheet with a variable curvature profile is obtained. S4. Start the lifting hydraulic cylinder at the end of the frame to drive the flexible roller to move 10 mm away from the rigid roller, and reset the device; Pressure L e , the specific expression of polyurethane rubber thickness H is: ; ; in, is the loading displacement of the flexible roller to the rigid roller, is the diameter of the flexible roller, e is the eccentricity between the center of the flexible roller and the center of the core shaft, and d0 is the core diameter of the flexible roller.

[0032] Under plane strain conditions, based on the classical elastic-plastic theory and Hertz contact theory, the curvature radius of the neutral layer of the metal sheet before springback is obtained. The expression: ; According to the classical springback theory, the curvature radius of the neutral layer of the metal sheet after unloading and rebound can be obtained: The expression: ; in, is the downward pressure, is the thickness of polyurethane rubber, is the elastic modulus of the plate, is the material constant of the plate material, is the power strengthening coefficient of the plate material, is the plate thickness, is the Poisson's ratio of the plate material, is the elastic modulus of the polyurethane rubber layer of the flexible roller, is the rigid roller radius, is the elastic modulus of the rigid roller.

[0033] The main parameters of the flexible roller are: diameter 400mm, eccentricity between the center of the flexible roller and the center of the core shaft is 3mm, length 1400mm, and core diameter of the flexible roller is 200mm. The main parameters of the rigid roller are: diameter 150mm, length 1700mm.

[0034] The time and pressure L can be calculated from the above data e, the relationship between the thickness H of polyurethane rubber: ; ; Here, t is the time it takes for the flexible roller to rotate counterclockwise around the center of the mandrel at a speed of 0.52 rad / s.

[0035] Under plane strain conditions, based on the classical elastic-plastic theory and Hertz contact theory, the curvature radius of the neutral layer of the sheet metal before springback is obtained. The expression: ; According to the classical rebound theory, the expression of the neutral layer curvature radius r after unloading rebound can be obtained: ; in, is the pressing amount, H is the thickness of polyurethane rubber; The embodiments described above are merely descriptions of preferred implementations of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should fall within the scope of protection determined by the claims of the present invention.

Claims

1. A forming method for eccentric two-roller flexible bending of a variable curvature metal sheet, characterized by: It includes the following steps: S1, placing the metal sheet between a rigid roller and a flexible roller; S2, driving the rigid roller to load a displacement L in the direction of the flexible roller by a lifting hydraulic cylinder, causing the metal sheet to undergo initial bending deformation; S3, drive the flexible roller to rotate clockwise around the center of the mandrel at a speed of V, driving the metal sheet to feed, the eccentricity between the center of the mandrel and the center of the flexible roller is e, and the value range of e is 0.01 to , the metal sheet dynamically changes its bending radius during the feeding process and forms a variable curvature profile after springback; Flexible roller rotation After the angle is set, the metal sheet with variable curvature profile is obtained, and the pressing amount L e , the specific expression of polyurethane rubber thickness H is: ； ； in, is the loading displacement of the flexible roller to the rigid roller, is the diameter of the flexible roller, e is the eccentricity between the center of the flexible roller and the center of the core shaft, and d0 is the core diameter of the flexible roller; S4. Under plane strain conditions, the curvature radius of the neutral layer of the metal sheet before springback is obtained The expression: ； At the same time, the curvature radius of the neutral layer of the metal sheet after unloading and rebound is obtained The expression: ； in, is the downward pressure, is the thickness of polyurethane rubber, is the elastic modulus of the plate, is the material constant of the plate material, is the power strengthening coefficient of the plate material, is the plate thickness, is the Poisson's ratio of the plate material, is the elastic modulus of the polyurethane rubber layer of the flexible roller, is the rigid roller radius, is the elastic modulus of the rigid roller; S5. The flexible roller is moved away from the rigid roller by a displacement L1 through the lifting hydraulic cylinder to complete the reset.

2. The forming method of variable curvature metal sheet by eccentric two-roller flexible rolling according to claim 1, characterized in that: In step S1 , the flexible roller is a roller shaft of polyurethane rubber cured outside a rigid core shaft, and the thickness of the polyurethane rubber layer is eccentrically distributed.

3. The forming method of variable curvature metal sheet by eccentric two-roller flexible rolling according to claim 2, characterized in that: In step S2 , the flexible roller only has the freedom to rotate around the center, and the rigid roller has the freedom to rotate around the core axis and to move vertically.

4. The forming method of variable curvature metal sheet by eccentric two-roller flexible rolling according to claim 1, characterized in that: By changing the eccentricity e between the center of the mandrel and the center of the flexible roller, the hardness of the polyurethane rubber, the diameter of the rigid roller, the diameter of the flexible roller, the diameter of the mandrel, and the eccentricity of the mandrel and the flexible roller, the roll bending of metal sheets with different curvature profiles can be achieved.

5. The forming method of variable curvature metal sheet by eccentric two-roller flexible rolling according to claim 1, characterized in that: The axis of the flexible roller core and the axis of the rigid roller can be adjusted to meet the needs of roll bending of metal sheets with different curvature profiles.

6. The forming method of variable curvature metal sheet by eccentric two-roller flexible rolling according to claim 1, characterized in that: Sheet metal includes materials with painting, electroplating, multi-layer combination, protective layer, embossing and surface polishing.

7. A forming device for eccentric two-roller flexible rolling of a variable curvature metal sheet according to any one of claims 1 to 6, characterized in that: It includes a drive assembly, an upper roller support assembly and a quick-change assembly. The drive assembly includes a frame, a drive motor, a reducer, a flexible roller, a hydraulic cylinder and a rigid roller. The drive motor and the reducer are both connected to the frame. The first end of the flexible roller is connected to the output shaft of the drive motor through the reducer and a coupling. The second end of the flexible roller is rotatably connected to the frame. The fixed end of the hydraulic cylinder is connected to the frame. The first end of the rigid roller is connected to the output end of the hydraulic cylinder through a bearing seat. The second end of the rigid roller is slidably connected to the frame through the bearing seat. The upper roller support assembly is arranged above the frame, and the quick-change assembly is arranged on both sides of the flexible roller.

8. The forming device according to claim 6, characterized in that: The upper roller support assembly includes a crossbeam, a bracket, a pin and a friction roller. Both ends of the crossbeam are connected to the frame. The brackets are evenly distributed under the crossbeam. The friction roller is rotatably connected to the bracket through the pin, and the friction roller is rollingly engaged with the rigid roller.

9. The forming device according to claim 6, characterized in that: The quick-change assembly includes a coupling joint, a first open shaft seat, a fixing pin and a second open shaft seat. The coupling joint is connected to the flexible roller through the fixing pin and the first open shaft seat, and the end of the flexible roller is connected to the second open shaft seat through the fixing pin.

10. The forming device according to claim 6, characterized in that: The rotation axis of the flexible roller is parallel to the rotation axis of the rigid roller.

Images