A method of prestress incremental forming
Patent Information
- Application Number
- CN202610948049.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-06-29
- Publication Date
- 2026-09-25
AI Technical Summary
[0003]然而，在制造深腔形薄壁构件（高径比通常大于1）时，传统渐进成形技术面临以下严峻挑战：（1）材料堆积与起皱：在成形过程中，板材边缘区域的材料会向中心流动，导致在构件侧壁，特别是深腔的底部转角区域，产生严重的材料堆积和起皱现象，严重影响构件精度和表面质量
本发明提供的预应力渐进成形方法，预弯曲步骤通过增大成形区域未变形坯料面积，降低渐进成形变形量，同时在坯料中部引入了有益的初始应变，有效抑制了起皱等缺陷，使得制造更深、圆角更小的薄壁深腔构件成为可能。通过预弯曲引入的初始应力场可以与渐进成形产生的应力场相互抵消，从而显著降低整体的残余应力和回弹效应。结合集成了回弹补偿的优化轨迹，能够主动、精确地控制构件的最终形状，获得较高的尺寸精度。
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Figure CN122806934A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of sheet metal plastic forming technology, and more particularly to a prestressed progressive forming method. Background Technology
[0002] Progressive forming technology is an advanced digital sheet metal forming technology. It uses a forming tool head controlled by a CNC system to perform localized, point-by-point plastic processing on the sheet metal along a predetermined trajectory, eventually accumulating to form the required three-dimensional part. It has advantages such as high flexibility, short cycle time, and no need for special molds.
[0003] However, when manufacturing deep-cavity thin-walled components (with a height-to-diameter ratio usually greater than 1), traditional incremental forming technology faces the following severe challenges: (1) Material accumulation and wrinkling: During the forming process, the material in the edge area of the sheet metal will flow towards the center, resulting in severe material accumulation and wrinkling on the sidewalls of the component, especially in the bottom corner area of the deep cavity, which seriously affects the component's accuracy and surface quality. (2) Uneven wall thickness distribution: Incremental forming follows the sine law, causing the component's sidewall thickness to gradually decrease from the opening to the bottom. For deep-cavity components, the bottom area is very prone to cracking due to excessive thinning. (3) Poor forming stability: As the forming depth increases, the already formed suspended sidewall is prone to instability and vibration under the subsequent extrusion of the tool head, and may even lead to the failure of the forming process. (4) Excessive forming force: One-time forming of a deep cavity requires the tool head to perform a large amount of continuous plastic work in a local area, resulting in huge forming force, which places extremely high demands on the rigidity of the equipment and the life of the tool head.
[0004] To address the defects in incremental forming of deep-cavity, thin-walled components, existing technologies primarily employ multi-pass incremental forming, multi-point and incremental composite forming, and stretching-incremental composite forming. Multi-pass incremental forming is mainly used for forming straight-walled parts with large forming angles. Its characteristic is controlling material flow and redistribution through multiple forming processes, achieving crack-free forming of straight-walled parts. Multi-point and incremental composite forming is a flexible metal sheet processing method. Its basic idea is to discretize the traditional integral forming die into a series of regularly arranged and height-adjustable basic shapes. Based on the high efficiency and low precision of multi-point forming and the high precision and low efficiency of incremental forming, a multi-point and incremental composite forming technology is proposed. Its basic idea is to combine multi-point forming and incremental forming processes, utilizing existing multi-point forming equipment, and developing a suitable process for three-dimensional curved surface forming of sheet metal according to the shape characteristics and precision requirements of the formed part. This technology fully leverages the advantages of both multi-point and incremental technologies, improving the forming capacity, forming accuracy, and forming efficiency of sheet metal.
[0005] Stretch-incremental composite forming: The process flow of stretch-incremental composite forming involves first CNC stretching of the sheet metal, followed by incremental forming. This process only requires a lower die; the upper die is replaced by a general-purpose incremental forming tool head, which can significantly improve the forming accuracy and thickness uniformity of the parts. Although multi-pass incremental forming can compensate for the material thinning in large-angle areas of single-pass forming and delay material fracture by controlling material flow through path optimization, it still cannot effectively solve the core contradiction of material accumulation and bottom thinning in deep cavity forming, and the improvement in forming capacity is limited. Multi-point and incremental composite forming and stretch-incremental composite forming require multi-point forming presses and dies, stretch forming machines and dies, making the process flow complex and costly. In addition, due to the limitations of multi-point forming and stretch forming technologies, the above two composite forming methods are only applicable to aluminum alloy parts.
[0006] Therefore, there is an urgent need for a new method for forming deep cavity thin-walled components that can take into account the types of forming materials, formability, precision and efficiency. Summary of the Invention
[0007] This invention provides a prestressed progressive forming method to solve the problems mentioned in the background art.
[0008] Specifically, the present invention provides a prestressed progressive forming method, comprising: The metal sheet blank is fixed to the support frame of the forming equipment by a flexible clamping mechanism. The clamping mechanism is moved to make the effective forming area produce a pre-bending arc in the same direction as the final forming direction. The pre-bent metal sheet blank is fixed and clamped around its perimeter using a flexible clamping structure, and the pre-bent surface is modeled using laser scanning or other shape detection methods. The forming tool head performs layered progressive forming on the pre-bent metal sheet blank according to the pre-generated forming trajectory.
[0009] Furthermore, before fixing the metal sheet blank to the support frame of the forming equipment using a flexible clamping mechanism, the method further includes: analyzing the shape of the target part and determining the direction with the largest curvature as the pre-bending direction.
[0010] Furthermore, before fixing the metal sheet blank to the support frame of the forming equipment using a flexible clamping mechanism, the method further includes: dividing the metal sheet blank into a clamping area and an effective forming area.
[0011] Furthermore, the size of the effective forming area is determined based on the shape of the target part, and the size of the clamping area is determined based on the size of the clamping jaws.
[0012] Furthermore, the effective forming area length of the pre-bending blank is 0.8 to 0.85 times the arc length of the target part in the direction of large curvature.
[0013] Furthermore, the effective forming area length of the blank in the vertical pre-bending direction is 0.9 to 0.95 times the arc length of the target part in the small curvature direction.
[0014] Furthermore, the clamping area size is 30~50mm.
[0015] Furthermore, after generating a pre-bending arc in the effective forming area that is the same as the final forming direction, the method further includes: stopping the movement of the clamping jaws when the chord length of the pre-bending arc surface is the same as the chord length of the target part.
[0016] Furthermore, the forming trajectory is generated based on the pre-bent surface and the three-dimensional CAD model of the target part, and a springback compensation algorithm is integrated for path optimization.
[0017] The above-described technical solution of the present invention has the following advantages: The prestressed progressive forming method provided by this invention reduces progressive forming deformation by increasing the area of the undeformed blank in the forming region through a pre-bending step. Simultaneously, it introduces beneficial initial strain in the middle of the blank, effectively suppressing defects such as wrinkling, making it possible to manufacture deeper, thin-walled deep-cavity components with smaller corner radii. The initial stress field introduced by pre-bending can cancel out the stress field generated by progressive forming, thereby significantly reducing overall residual stress and springback effect. Combined with an optimized trajectory integrating springback compensation, the final shape of the component can be actively and precisely controlled, achieving high dimensional accuracy. Attached Figure Description
[0018] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0019] Figure 1 A process flow diagram provided for an embodiment of the present invention; Figure 2 A target part drawing provided for an embodiment of the present invention; Figure 3 A planar slab drawing provided for an embodiment of the present invention; Figure 4 A diagram showing the clamping and pre-bending of a planar slab provided in an embodiment of the present invention; Figure 5 This is a diagram showing the clamping of the sheet metal around its perimeter, provided in an embodiment of the present invention. Figure 6 This is a diagram showing the progressive forming of sheet metal according to an embodiment of the present invention; Figure 7The digital model of the U-shaped cross-section annular thin-walled component provided in the embodiment of the present invention. Detailed Implementation
[0020] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of the invention. However, those skilled in the art will understand that the invention can be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the invention with unnecessary detail.
[0021] It should be understood that, when used in this specification and the appended claims, the term "comprising" indicates the presence of the described features, integrals, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.
[0022] Furthermore, in the description of this invention and the appended claims, the terms "first," "second," "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.
[0023] References to "one embodiment" or "some embodiments" as described in this specification mean that one or more embodiments of the invention include a particular feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized. "A plurality" means "two or more."
[0024] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.
[0025] This invention provides a prestressed progressive forming method, comprising: fixing a metal sheet blank to the support frame of a forming equipment using a flexible clamping mechanism; moving the clamping mechanism to generate a pre-bending arc in the effective forming area that is the same as the final forming direction; fixing and clamping the pre-bent metal sheet blank around its perimeter using the flexible clamping structure; modeling the pre-bent surface using laser scanning or other shape detection methods; and performing layered progressive forming of the pre-bent metal sheet blank using a forming tool head according to a pre-generated forming trajectory.
[0026] In some embodiments, before fixing the metal sheet blank to the support frame of the forming equipment using a flexible clamping mechanism, the method further includes: analyzing the shape of the target part and determining the direction with the largest curvature as the pre-bending direction.
[0027] In some embodiments, before fixing the metal sheet blank to the support frame of the forming equipment by a flexible clamping mechanism, the method further includes: dividing the metal sheet blank into a clamping area and an effective forming area.
[0028] In some embodiments, the size of the effective forming area is determined based on the shape of the target part, and the size of the clamping area is determined based on the size of the clamping jaws.
[0029] In some embodiments, the effective forming region length of the pre-bending direction blank is 0.8 to 0.85 times the arc length of the target part in the direction of large curvature.
[0030] In some embodiments, the effective forming region length of the blank in the vertical pre-bending direction is 0.9 to 0.95 times the arc length of the target part in the small curvature direction.
[0031] In some embodiments, the clamping area size is 30~50mm.
[0032] In some embodiments, after generating a pre-bent arc in the effective forming area that is the same as the final forming direction, the method further includes: stopping the movement of the clamping jaws when the chord length of the pre-bent arc surface is the same as the chord length of the target part.
[0033] In some embodiments, the forming trajectory is generated based on the pre-bent surface and the three-dimensional CAD model of the target part, and a springback compensation algorithm is integrated for path optimization.
[0034] To address the shortcomings of existing technologies, this invention proposes a prestressed progressive forming method, the process flow diagram of which is shown below. Figure 1 This method aims to effectively improve material flow, suppress wrinkling and excessive thinning by introducing a pre-bending step combined with a specific progressive forming path. Furthermore, by actively controlling springback, it significantly improves the forming depth, dimensional accuracy, and surface quality of deep-cavity thin-walled components. The specific scheme is as follows: Step 1: Blank Preparation: Analyze the shape of the target part and determine the direction of maximum curvature as the pre-bending direction. See... Figure 2 Flat blank (see...) Figure 3 The forming area is divided into a clamping area and an effective forming area. The size of the effective forming area is determined based on the shape of the target part, and generally follows these principles: (1) In the formula: The effective forming area length of the blank in the pre-bending direction, in mm. The arc length in the direction of maximum curvature of the target part, in mm. The effective forming area of the blank perpendicular to the pre-bending direction, in mm. The arc length in the direction of small curvature of the target part, in mm. The size of the clamping area is determined according to the size of the clamping jaws, and is generally 30~50mm.
[0035] Step 2: Clamping and Pre-bending: The metal sheet blank is fixed to the support frame of the forming equipment using a flexible clamping mechanism. Figure 4 The moving clamping mechanism creates a pre-bent arc in the effective forming area that is in the same direction as the final forming direction. When the chord length of the pre-bent arc is the same as the chord length of the target part, the moving clamping jaws stop.
[0036] Step 3: Clamping the sheet metal around its perimeter: A flexible clamping structure is used to secure the pre-bent metal sheet around its perimeter. (See...) Figure 5 The pre-bent surface is modeled using laser scanning or other shape inspection methods.
[0037] Step 4: Progressive Forming: The forming tool head is used to progressively form the pre-bent metal sheet blank in layers according to a predetermined forming trajectory. See... Figure 6 The forming trajectory is generated based on the pre-bent surface and the three-dimensional CAD model of the target part, and a springback compensation algorithm is integrated for path optimization.
[0038] Taking the forming of a thin-walled component with a U-shaped cross-section and annular segment as an example, the specific implementation process of this invention is illustrated. The part design digital model is shown below. Figure 7 ,Depend on Figure 7 The effective forming area of the part blank is calculated as 180mm×115mm using formula (1) with the middle arc length combined. With a 30mm clamping area around the perimeter, the part blank is 240mm×175mm. The blank is clamped on the support frame, and the upper and lower clamps are moved towards the middle until the chord length of the pre-bent arc surface is the same as the chord length of the target part (i.e., 144mm). The clamping jaws are then stopped. The pre-bent sheet is then fixed and clamped around the perimeter, and the pre-bent surface is modeled using a laser scanning detection method. The pre-bent surface and the target component surface are compared to generate a contour line progressive forming trajectory. A 5mm diameter tool head is used for layer-by-layer forming.
[0039] This invention proposes a prestressed progressive forming method to address the problem of severe wall thickness reduction in the progressive forming of deep-cavity thin-walled components. By pre-bending the sheet metal, the method pre-fills the progressive forming process based on pure shear thinning deformation. Compared with existing technologies, this invention has the following significant advantages: (1) Significantly improves forming limit: The pre-bending step increases the area of the undeformed blank in the forming region, reduces the amount of progressive forming deformation, and introduces beneficial initial strain in the middle of the blank, effectively suppressing defects such as wrinkling, making it possible to manufacture thin-walled deep cavity components with deeper corners and smaller radii.
[0040] (2) Effective control of springback: The initial stress field introduced by pre-bending can cancel out the stress field generated by progressive forming, thereby significantly reducing the overall residual stress and springback effect. Combined with the optimized trajectory that integrates springback compensation, the final shape of the component can be actively and accurately controlled to obtain high dimensional accuracy.
[0041] (3) Improve material flowability and thickness distribution: This method makes material deformation more coordinated, the wall thickness distribution of components more uniform, and reduces the thinning rate of the thinnest point.
[0042] (4) Enhanced process flexibility: The present invention retains the core advantage of incremental forming. It can adapt to thin-walled deep cavity components of different sizes and curvatures simply by changing the CNC program. There is no need to make expensive physical molds, which is especially suitable for small-batch, multi-variety production mode.
[0043] (5) Improve surface quality and forming efficiency: Pre-bending makes the sheet material closer to the target shape in the early stage of forming, reducing the ineffective stroke and material accumulation of the tool head in subsequent processing, which helps to improve surface finish and shorten the total processing time.
[0044] (6) A wider range of applicable materials: Since the convex and concave surfaces of the sheet are not obstructed during pre-bending, components of difficult-to-deform materials such as titanium alloys can be formed by heating on one side and forming on the other.
[0045] The prestressed progressive forming method provided by this invention is an efficient, low-cost, and highly reliable method with good economic benefits.
[0046] It should be noted that the various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. The present invention is not limited to the specific structures described above and shown in the figures. Furthermore, for the sake of brevity, detailed descriptions of known methods and techniques are omitted here.
[0047] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.
Claims
1. A prestressed progressive forming method, characterized in that, include: The metal sheet blank is fixed to the support frame of the forming equipment by a flexible clamping mechanism. The clamping mechanism is moved to make the effective forming area produce a pre-bending arc in the same direction as the final forming direction. The pre-bent metal sheet blank is fixed and clamped around its perimeter using a flexible clamping structure, and the pre-bent surface is modeled using laser scanning or other shape detection methods. The forming tool head performs layered progressive forming on the pre-bent metal sheet blank according to the pre-generated forming trajectory.
2. The prestressed progressive forming method as described in claim 1, characterized in that, Before fixing the metal sheet blank to the support frame of the forming equipment using a flexible clamping mechanism, the process further includes: analyzing the shape of the target part and determining the direction with the largest curvature as the pre-bending direction.
3. The prestressed progressive forming method as described in claim 1, characterized in that, Before fixing the metal sheet blank to the support frame of the forming equipment using a flexible clamping mechanism, the method further includes: dividing the metal sheet blank into a clamping area and an effective forming area.
4. The prestressed progressive forming method as described in claim 3, characterized in that, The size of the effective forming area is determined based on the shape of the target part, and the size of the clamping area is determined based on the size of the clamping jaws.
5. The prestressed progressive forming method as described in claim 4, characterized in that, The effective forming area length of the pre-bending blank is 0.8 to 0.85 times the arc length of the target part in the direction of large curvature.
6. The prestressed progressive forming method as described in claim 4, characterized in that, The effective forming area length of the blank in the vertical pre-bending direction is 0.9 to 0.95 times the arc length of the small curvature direction of the target part.
7. The prestressed progressive forming method as described in claim 4, characterized in that, The clamping area size is 30~50mm.
8. The prestressed progressive forming method as described in claim 1, characterized in that, After generating a pre-bending arc in the effective forming area that is the same as the final forming direction, the method further includes: stopping the movement of the clamping jaws when the chord length of the pre-bending arc surface is the same as the chord length of the target part.
9. The prestressed progressive forming method as described in claim 1, characterized in that, The forming trajectory is generated based on the pre-bent surface and the three-dimensional CAD model of the target part, and a springback compensation algorithm is integrated for path optimization.