Method and die for preventing springback of sheet metal during bending

Abstract

The application discloses a metal plate bending forming anti-rebound method and a die, and solves the technical problems of high rebound rate and insufficient forming precision in the conventional metal plate bending forming process. The die comprises an upper die assembly, a lower die assembly and a rebound compensation mechanism, the upper die assembly is matched with the lower die assembly, and the rebound compensation mechanism is embedded in the inner wall of the bending die of the lower die assembly. The method comprises the steps of plate pretreatment, die debugging, plate positioning, bending forming, pressure maintaining and shaping, demolding and taking, and forming detection. Through the rebound compensation mechanism, compensation pressure is applied in the bending process, combined with the pressure maintaining and shaping process, the rebound trend of the plate is effectively offset, the bending angle deviation is controlled within ±0.3°, the forming precision is improved, and the bending processing is suitable for various metal plates such as aluminum alloy, high-strength steel and the like.

Description

Technical Field

[0001] This invention relates to the field of metal material processing technology, specifically to a method and mold for preventing springback during bending and forming of metal sheets. Background Technology

[0002] Sheet metal bending is a common processing technique in machinery manufacturing, automotive parts, aerospace, and other fields. Pressure is applied to the sheet metal using a mold, causing it to plastically deform and form the desired bending angle. However, due to the elastic recovery characteristics of metal materials, the sheet metal will spring back to some extent after bending, resulting in a deviation between the actual bending angle and the target angle, affecting product accuracy.

[0003] Traditional sheet metal bending dies typically consist of only an upper and lower die, lacking a dedicated springback compensation structure. To counteract springback, multiple trial runs are often required to adjust the die angle, or over-bending may be employed, increasing processing costs and reducing production efficiency. Furthermore, traditional bending methods are mostly simple pressure bending, lacking precise control over parameters such as pressure and temperature during the bending process. This makes it difficult to meet the high-precision forming requirements for sheets with high springback rates, such as aluminum alloys and high-strength steel.

[0004] As industrial manufacturing demands ever higher precision, the development of a metal sheet bending forming method and mold that can effectively suppress springback and improve forming accuracy has become an urgent need in the industry. Summary of the Invention

[0005] The purpose of this invention is to provide a method and mold for preventing springback during bending and forming of metal sheets, so as to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a metal sheet bending forming anti-springback mold, comprising an upper mold assembly, a lower mold assembly, and a springback compensation mechanism; the upper mold assembly includes an upper mold base and a bending punch detachably connected to the bottom of the upper mold base; the lower mold assembly includes a lower mold base and a bending die formed at the top of the lower mold base, the bending die being adapted to the bending punch; the springback compensation mechanism is dynamically disposed on the inner wall of the cavity of the bending die, and is used to apply a compensation pressure that changes proportionally and in tandem with the main bending pressure to the deformation area of ​​the sheet during the sheet bending process, based on the real-time deformation state of the sheet, so as to counteract the springback tendency of the sheet in the forming stage.

[0007] As a further improvement of the present invention, the springback compensation mechanism includes a plurality of elastic ejector pins, a pressure sensor and a controller; the elastic ejector pins are embedded in the inner wall of the cavity of the bending die, the pressure sensor is disposed at the bottom end of the elastic ejector pin and is used to detect the pressure value of the elastic ejector pin on the plate; the controller is electrically connected to the pressure sensor and the elastic ejector pin respectively and is used to adjust the extension length of the elastic ejector pin according to the pressure value.

[0008] As a further improvement of the present invention, the elastic ejector pin includes a pin body, a spring, and an adjusting screw; the spring is sleeved on the outside of the pin body, and one end of the spring abuts against the bottom end of the pin body, and the other end abuts against the inner wall of the bending die; the adjusting screw is threadedly connected to the bending die, and one end of the adjusting screw abuts against the end of the spring away from the pin body.

[0009] As a further improvement of the present invention, the upper mold assembly further includes a guide post, and the lower mold assembly further includes a guide sleeve. The guide post and the guide sleeve are adapted to achieve precise guidance between the upper mold assembly and the lower mold assembly.

[0010] As a further improvement of the present invention, the surface of the bending punch is coated with a wear-resistant coating, and the material of the wear-resistant coating is titanium nitride or diamond.

[0011] As a further improvement of the present invention, the mold further includes a temperature regulating mechanism, which includes a heating pipe disposed inside the bending punch and a cooling channel disposed inside the bending die, for adjusting the temperature during the bending process according to the material of the sheet metal.

[0012] As a further improvement of the present invention, the temperature regulating mechanism further includes a temperature sensor disposed on the surface of the bending punch, which is used to detect the temperature at the contact point between the sheet metal and the bending punch.

[0013] As a further improvement of the present invention, the inner wall of the cavity of the bending die is provided with a plurality of venting grooves, the depth of which is 0.1-0.3 mm and the width of which is 0.2-0.5 mm.

[0014] This invention also discloses a method for preventing springback during bending and forming of metal sheets, which includes the following steps: S1. Sheet metal pretreatment: Clean and lubricate the area of ​​the sheet metal to be bent. S2. Mold Adjustment: After assembling the upper mold assembly, lower mold assembly, and springback compensation mechanism, adjust the initial compensation parameters of the springback compensation mechanism according to the material, thickness, and target bending angle of the metal sheet; S3. Sheet metal positioning: Place the pre-treated metal sheet on the bending die of the lower die assembly, and fix the metal sheet with the positioning structure to ensure that the area to be bent is aligned with the cavity of the bending die; S4. Bending Forming: Drive the upper die assembly downward to make the bending punch contact with the metal sheet and apply pressure, causing the metal sheet to deform into the cavity of the bending die. During the bending process, the springback compensation mechanism applies compensation pressure to the deformed area of ​​the metal sheet. S5. Pressure holding and shaping: After the metal sheet reaches the target bending angle, the pressure of the upper mold assembly is maintained for a preset time, while the compensation pressure of the springback compensation mechanism is maintained. The temperature of the bending area of ​​the sheet is controlled within the range of 50-200℃ by the temperature adjustment mechanism. S6. Demolding and Part Removal: Drive the upper mold assembly to reset upwards, release the compensation pressure of the springback compensation mechanism, and remove the formed metal sheet from the mold; Step S7: Forming inspection. Use visual inspection equipment to inspect the bending angle and surface quality of the formed metal sheet. If the bending angle deviation exceeds ±0.5°, readjust the parameters of the springback compensation mechanism and bend the sheet again. If scratches or wrinkles appear on the surface, polish the surfaces of the bending punch and bending die, or change the lubrication method.

[0015] As a further improvement of the present invention, in step S1, the surface lubrication treatment is carried out by spraying lubricating oil or pasting a lubricating film, and the viscosity of the lubricating oil is 50-150 mm² / s; in step S2, the initial compensation parameters include the extension length of the elastic pin in the springback compensation mechanism and the preload force, and the adjustment range of the preload force is 500-2000 N; in step S4, the pressing speed of the upper mold assembly is 5-20 mm / s, and the magnitude of the compensation pressure is 10%-30% of the pressure required for bending the metal sheet; in step S5, the preset time is 10-60 s, and during the pressure holding process, the temperature of the bending area is controlled at 50-200℃ by the temperature adjustment mechanism.

[0016] Compared with the prior art, the beneficial effects of the present invention are: 1. In this invention, by setting a springback compensation mechanism on the inner wall of the bending die, compensation pressure is applied to the deformed area of ​​the sheet during the bending process. Combined with the pressure holding and shaping process, the springback tendency of the sheet is effectively counteracted, so that the bending angle deviation is controlled within ±0.3°, thereby improving the forming accuracy. 2. The pressure sensor and controller in the springback compensation mechanism of this invention can realize real-time adjustment of the compensation pressure, adapt to the bending requirements of plates of different materials and thicknesses, and improve the versatility of the mold. 3. In this invention, by setting a temperature adjustment mechanism, the temperature of the bending area can be adjusted according to the material of the board, reducing the rebound rate of the material, and avoiding problems such as cracking and deformation of the board due to excessively high or low temperature. The preset pressure and temperature parameters are controlled in synergy, producing a precision improvement effect that cannot be achieved by simply superimposing the two. 4. The method of the present invention has a complete process, including pretreatment, debugging, positioning, bending, pressure holding, demolding and testing steps, realizing automated and precise processing of metal sheet bending and forming, and improving production efficiency. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall invention; Figure 2 This is a schematic diagram of the springback compensation mechanism of the present invention; Figure 3 This is a top view of the bending die of the present invention; Figure 4 This is a flowchart of the method of the present invention.

[0018] In the diagram: 1. Upper mold assembly; 101. Upper mold base; 102. Bending punch; 103. Guide post; 2. Lower mold assembly; 21. Lower mold base; 22. Bending die; 23. Guide sleeve; 3. Springback compensation mechanism; 31. Elastic ejector pin; 311. Pin body; 312. Spring; 313. Adjusting screw; 32. Pressure sensor; 33. Controller; 4. Temperature regulation mechanism; 41. Heating tube; 42. Cooling channel; 43. Temperature sensor. Detailed Implementation

[0019] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0020] It should be noted that when an element is referred to as "fixed," "mounted," "connected," or "set" with another element, it can be directly on or indirectly on the other element. It should be understood that the terms "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention.

[0021] As a further improvement of the present invention, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature.

[0022] Example 1 Please see Figure 1-4 The present invention provides a technical solution: a metal sheet bending forming anti-springback mold, including an upper mold assembly 1, a lower mold assembly 2, a springback compensation mechanism 3, and a temperature adjustment mechanism 4; the upper mold assembly 1 includes an upper mold base 101 and a bending punch 102 detachably connected to the bottom of the upper mold base 101, the surface of the bending punch 102 is coated with a wear-resistant coating, the material of the wear-resistant coating is titanium nitride or diamond, the upper mold assembly 1 also includes a guide post 103, the lower mold assembly 2 includes a guide sleeve 23, the guide post 103 is adapted to the guide sleeve 23, and is used to achieve precise guidance between the upper mold assembly 1 and the lower mold assembly 2.

[0023] The lower die assembly 2 includes a lower die base 21 and a bending die 22 opened on the top of the lower die base 21. The bending die 22 is adapted to the bending punch 102. The inner wall of the cavity of the bending die 22 is also provided with several venting grooves. The depth of the venting grooves is 0.1-0.3mm and the width is 0.2-0.5mm. The springback compensation mechanism 3 is dynamically set on the inner wall of the cavity of the bending die 22. It is used to apply a compensation pressure that changes proportionally with the bending main pressure to the deformation area of ​​the sheet during the bending process, according to the real-time deformation state of the sheet, so as to counteract the springback tendency of the sheet in the forming stage.

[0024] The springback compensation mechanism 3 includes several elastic ejector pins 31, a pressure sensor 32, and a controller 33. The elastic ejector pins 31 are embedded in the inner wall of the cavity of the bending die 22. The pressure sensor 32 is located at the bottom end of the elastic ejector pin 31. The elastic ejector pin 31 includes a pin body 311, a spring 312, and an adjusting screw 313. The spring 312 is sleeved on the outside of the pin body 311, with one end of the spring 312 abutting against the bottom end of the pin body 311 and the other end abutting against the inner wall of the bending die 22. The adjusting screw 313 is threadedly connected to the bending die 22, with one end of the adjusting screw 313 abutting against the end of the spring 312 away from the pin body 311, for detecting the pressure value of the elastic ejector pin 31 on the sheet metal. The controller 33 is electrically connected to the pressure sensor 32 and the elastic ejector pin 31 respectively, for adjusting the extension length of the elastic ejector pin 31 according to the pressure value.

[0025] The temperature regulation mechanism 4 includes a heating tube 41 disposed inside the bending punch 102 and a cooling channel 42 disposed inside the bending die 22, which are used to adjust the temperature during the bending process according to the material of the sheet metal. It also includes a temperature sensor 43 disposed on the surface of the bending punch 102, which is used to detect the temperature at the contact point between the sheet metal and the bending punch 102.

[0026] Another method for preventing springback during bending and forming of metal sheets includes the following steps: S1. Sheet metal pretreatment: Clean and lubricate the area of ​​the sheet metal to be bent. S2. Mold Adjustment: After assembling the upper mold assembly 1, lower mold assembly 2 and springback compensation mechanism 3, adjust the initial compensation parameters of the springback compensation mechanism 3 according to the material, thickness and target bending angle of the metal sheet. S3. Sheet metal positioning: Place the pre-treated metal sheet on the bending die 22 of the lower die assembly 2, and fix the metal sheet through the positioning structure to ensure that the area to be bent is aligned with the cavity of the bending die 102; S4. Bending Forming: Drive the upper die assembly 1 to move downward, so that the bending punch 102 contacts the metal sheet and applies pressure, causing the metal sheet to deform into the cavity of the bending die 22. During the bending process, the springback compensation mechanism 3 applies compensation pressure to the deformation area of ​​the metal sheet. S5. Pressure holding and shaping: When the metal sheet reaches the target bending angle, the pressure of the upper mold assembly 1 is maintained for a preset time, while the compensation pressure of the springback compensation mechanism 3 is maintained. The temperature of the bending area of ​​the sheet is controlled within a specific range determined according to the material of the sheet through the temperature adjustment mechanism 4. S6. Demolding and part removal: Drive the upper mold assembly to reset upwards, and release the compensation pressure of the springback compensation mechanism 3 to remove the formed metal sheet from the mold; Step S7: Forming inspection. Use a visual inspection device to inspect the bending angle and surface quality of the formed metal sheet. If the bending angle deviation exceeds ±0.5°, readjust the parameters of the springback compensation mechanism 3 and perform bending again. If scratches or wrinkles appear on the surface, polish the surfaces of the bending punch 102 and the bending die 22, or change the lubrication method. Surface lubrication is achieved by spraying lubricating oil or applying a lubricating film. The viscosity of the lubricating oil is 50-150 mm² / s. In step S2, the initial compensation parameters include the extension length of the elastic pin 31 in the springback compensation mechanism 3 and the preload force. The adjustment range of the preload force is 500-2000 N. In step S4, the pressing speed of the upper mold assembly 1 is 5-20 mm / s, and the compensation pressure is 10%-30% of the pressure required for bending the metal sheet. In step S5, the preset time is 10-60 s, and during the pressure holding process, the temperature of the bending area is controlled at 50-200℃ by the temperature adjustment mechanism 4.

[0027] Example 2 The aluminum alloy sheet (2mm thick) was bent using the mold in Example 1, with a target bending angle of 90°. The specific method is as follows: S1. Plate pretreatment: The area of ​​the aluminum alloy plate to be deformed is cleaned with an ultrasonic cleaner, and then a lubricating oil with a viscosity of 100 mm² / s is sprayed on. S2. Mold Adjustment: After assembling the mold components, adjust the extension length of the elastic ejector pin to 5mm and the preload force to 1000N; S3. Sheet positioning: Place the pre-treated aluminum alloy sheet on the bending die and fix the sheet in place with positioning pins and positioning blocks; S4. Bending Forming: The upper die assembly is driven to move downward at a speed of 10 mm / s. The bending punch contacts the sheet metal and applies pressure. The springback compensation mechanism applies a compensation pressure of 20% of the bending pressure required. S5. Pressure holding and shaping: After the board reaches a 90° bending angle, maintain the pressure for 30 seconds, and at the same time control the temperature of the bending area at 80°C through the temperature adjustment mechanism; S6. Demolding and part removal: Drive the upper mold assembly to reset upwards, release the compensation pressure of the springback compensation mechanism, and remove the molded sheet material; S7. Molding Inspection: Visual inspection equipment was used to inspect the sheet metal. The bending angle was 89.8° with a deviation of -0.2°. The surface was free of scratches and wrinkles, meeting the accuracy requirements.

[0028] Example 3 A metal sheet bending forming anti-rebound mold has a structure that is basically the same as that of Example 1, except that the bending punch surface is coated with a diamond wear-resistant coating, and the venting groove has a depth of 0.15 mm and a width of 0.4 mm.

[0029] The above-mentioned mold is used to bend and form high-strength steel sheet (3mm thick) with a target bending angle of 60°. The specific method is as follows: S1. Plate pretreatment: The area of ​​the high-strength steel plate to be deformed is sandblasted and cleaned, and then a lubricating film is applied; S2. Mold Adjustment: Adjust the extension length of the elastic ejector pin to 6mm and the preload force to 1500N; S3. Sheet positioning: The sheet metal is fixed to the bending die by positioning pins and positioning blocks; S4. Bending Forming: Drive the upper die assembly downward at a speed of 8 mm / s, and apply a compensation pressure of 25% of the bending pressure required by the springback compensation mechanism; S5. Pressure holding and shaping: After the board reaches a bending angle of 60°, maintain the pressure for 40 seconds, while controlling the temperature of the bending area at 150°. S6. Demolding and Part Removal: Remove the molded sheet material; S7. Forming Inspection: The bending angle of the sheet is 60.2°, the deviation is +0.2°, the surface quality is good, and it meets the accuracy requirements.

[0030] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus.

[0031] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A metal sheet bending and forming anti-springback mold, characterized in that: The assembly includes an upper mold assembly (1), a lower mold assembly (2), and a springback compensation mechanism (3). The upper mold assembly (1) includes an upper mold base (101) and a bending punch (102) detachably connected to the bottom of the upper mold base (101). The lower mold assembly (2) includes a lower mold base (21) and a bending die (22) opened on the top of the lower mold base (21). The bending die (22) is adapted to the bending punch (102). The springback compensation mechanism (3) is dynamically set on the inner wall of the cavity of the bending die (22). During the bending process of the sheet metal, it applies a compensation pressure that changes proportionally with the main bending pressure to the deformation area of ​​the sheet metal according to the real-time deformation state of the sheet metal, so as to offset the springback tendency of the sheet metal in the forming stage. The springback compensation mechanism (3) includes several elastic ejector pins (31), a pressure sensor (32), and a controller (33); the elastic ejector pins (31) are embedded in the inner wall of the cavity of the bending die (22); the pressure sensor (32) is located at the bottom end of the elastic ejector pins (31) and is used to detect the pressure value of the elastic ejector pins (31) on the sheet metal; the controller (33) is electrically connected to the pressure sensor (32) and the elastic ejector pins (31) respectively, and is used to adjust the extension length of the elastic ejector pins (31) according to the pressure value. The elastic ejector pin (31) includes a pin body (311), a spring (312), and an adjusting screw (313); the spring (312) is sleeved on the outside of the pin body (311), and one end of the spring (312) abuts against the bottom end of the pin body (311), and the other end abuts against the inner wall of the bending die (22); the adjusting screw (313) is threadedly connected to the bending die (22), and one end of the adjusting screw (313) abuts against the end of the spring (312) away from the pin body (311).

2. The anti-springback mold for bending and forming metal sheets according to claim 1, characterized in that: The upper mold assembly (1) further includes a guide post (103), and the lower mold assembly (2) further includes a guide sleeve (23). The guide post (103) is adapted to the guide sleeve (23) to achieve precise guidance between the upper mold assembly (1) and the lower mold assembly (2).

3. The anti-springback mold for bending and forming metal sheets according to claim 2, characterized in that: The surface of the bending punch (102) is coated with a wear-resistant coating, the material of which is titanium nitride or diamond.

4. The anti-springback mold for bending and forming metal sheets according to claim 1, characterized in that: The mold also includes a temperature regulating mechanism (4), which includes a heating pipe (41) disposed inside the bending punch (102) and a cooling channel (42) disposed inside the bending die (22), for adjusting the temperature during the bending process according to the material of the sheet.

5. The anti-springback mold for bending and forming metal sheets according to claim 4, characterized in that: The temperature regulating mechanism (4) further includes a temperature sensor (43), which is disposed on the surface of the bending punch (102) and is used to detect the temperature at the contact position between the sheet metal and the bending punch (102).

6. The anti-springback mold for bending and forming metal sheets according to claim 1, characterized in that: The inner wall of the cavity of the bending die (22) is also provided with several venting grooves, the depth of which is 0.1-0.3 mm and the width of which is 0.2-0.5 mm.

7. A method for preventing springback during bending and forming of metal sheets, wherein the method employs a metal sheet bending and forming anti-springback mold as described in any one of claims 1-6, characterized in that: This method includes the following steps: S1. Sheet metal pretreatment: Clean and lubricate the area of ​​the sheet metal to be bent. S2. Mold debugging: After installing the upper mold assembly (1), lower mold assembly (2) and springback compensation mechanism (3), adjust the initial compensation parameters of the springback compensation mechanism (3) according to the material, thickness and target bending angle of the metal sheet; S3. Plate positioning: Place the pre-treated metal plate on the bending die (22) of the lower die assembly (2), and fix the metal plate by the positioning structure to ensure that the area to be bent is aligned with the cavity of the bending die; S4. Bending and forming: Drive the upper die assembly (1) to move downward, so that the bending punch (102) contacts the metal sheet and applies pressure, causing the metal sheet to deform into the cavity of the bending die (22). During the bending process, the springback compensation mechanism (3) applies compensation pressure to the deformation area of ​​the metal sheet. S5. Pressure holding and shaping: When the metal sheet reaches the target bending angle, the pressure of the upper mold assembly is maintained for a preset time, while the compensation pressure of the springback compensation mechanism (3) is maintained. The temperature of the bending area of ​​the sheet is controlled within the range of 50-200℃ by the temperature adjustment mechanism (4). S6. Demolding and part removal: Drive the upper mold assembly to reset upwards, and release the compensation pressure of the springback compensation mechanism (3) to remove the formed metal sheet from the mold; Step S7: Forming inspection. Use a visual inspection device to inspect the bending angle and surface quality of the formed metal sheet. If the bending angle deviation exceeds ±0.5°, readjust the parameters of the springback compensation mechanism (3) and bend the sheet again. If scratches or wrinkles appear on the surface, polish the surfaces of the bending punch (102) and bending die (22) or change the lubrication method.

8. The method for preventing springback during bending and forming of metal sheets according to claim 7, characterized in that: In step S1, the surface lubrication treatment is carried out by spraying lubricating oil or pasting a lubricating film, and the viscosity of the lubricating oil is 50-150 mm² / s; in step S2, the initial compensation parameters include the extension length of the elastic pin (31) in the springback compensation mechanism (3) and the preload force, and the adjustment range of the preload force is 500-2000 N; in step S4, the pressing speed of the upper mold assembly (1) is 5-20 mm / s, and the magnitude of the compensation pressure is 10%-30% of the pressure required for bending the metal sheet; in step S5, the preset time is 10-60 s, and during the pressure holding process, the temperature of the bending area is controlled at 50-200 ℃ by the temperature adjustment mechanism (4).

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