Incremental forming method and device capable of dynamically releasing stress
The dynamic stress release method using ball-shaped pressure heads on a CNC machine addresses stress accumulation issues in gradual forming, improving precision and tool life while enhancing forming efficiency.
Patent Information
- Application Number
- CN202510765316.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-10
- Publication Date
- 2025-07-15
AI Technical Summary
In the existing progressive forming technology, local stress concentration and uneven strain lead to problems such as low forming accuracy, serious tool wear, reduced forming limits and high processing costs.
The spherical indenter group is used to link with the CNC machine tool. By dynamically adjusting the head movement path, the sheet stress is released in real time, avoiding stress accumulation and local concentration, and combining lubrication optimization to reduce friction heat.
Significantly reduce rebound and residual stress, improve forming accuracy and tool life, reduce processing costs, and improve processing efficiency and stability.
Smart Images
Figure CN120306490A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of advanced manufacturing technologies, and particularly to a progressive forming method and device capable of dynamically releasing stress. Background Art
[0002] Incremental forming of metal sheets is a flexible manufacturing technology suitable for single-piece and small-batch metal products. It adopts a "layered manufacturing" method, using a forming tool head to move along the contour line under the control of a numerical control system to shape the sheet layer by layer. This forming method eliminates the need for expensive die manufacturing and realizes the digital and customized production of metal products.
[0003] Some processing characteristics of current progressive forming technologies may lead to factors affecting forming accuracy, including: 1. Progressive forming is a local deformation process, and the material is gradually deformed only in a small area. This concentration of local stress and strain easily leads to local instability, especially when the deformation area is narrow or sharp. 2. The tool path and feed strategy directly affect the stress distribution and deformation state. If the path planning is improper, it may cause over-concentration of stress in certain areas, promoting instability. 3. Progressive forming is usually processed layer by layer, and this characteristic leads to the accumulation of stress and strain during each layer of forming. If the deformation of the previous layers is uneven or there are existing internal defects, they will appear in subsequent layers and trigger instability. 4. During the forming process, the material thickness changes. Weak areas may not be able to withstand the stress due to insufficient thickness, resulting in instability. At the same time, workpieces with complex shapes are also prone to uneven stress distribution during the forming process, causing instability. 5. The elastic springback of the material during the forming process will affect the accuracy of the final shape. If the springback amount is large and not fully considered and controlled, it may lead to a deviation between the expected and actual shapes during the forming process, triggering instability. 6. Strain non-uniformity is prone to occur in progressive forming, especially at corners or where the curvature changes significantly. This strain non-uniformity will lead to local instability and cracking. 7. If the clamping and support of the workpiece are unstable, the action of the forming force will cause the movement or uneven deformation of the workpiece, resulting in instability during the forming process. Therefore, appropriate support and clamping are the keys to ensuring the stability of progressive forming. 8. The friction conditions between the tool and the material directly affect the forming force and material flow. If the friction coefficient is too large, it may increase the surface stress of the material, causing local instability; if the friction coefficient is too small, it may cause the tool to slide instead of effective deformation. 9. Stress accumulation will form in the sheet during processing. During the processing, due to the clamping of the tooling fixture, it is not obvious. When the fixture is removed after processing, the stress release will cause the sheet to have a large springback, resulting in serious distortion of the sheet.
[0004] In traditional progressive forming technologies, due to the accumulation and uneven distribution of internal stress, the following technical problems may occur: 1. Springback effect: After forming, the material undergoes elastic recovery due to the release of internal stress, resulting in deviations between the geometric shape of the part and the target dimensions, necessitating repeated corrections to process parameters or die design, thereby increasing costs and time. 2. Local stress concentration and fracture risk: Stress concentration is prone to occur in complex shapes or areas of rapid deformation (such as corners, deep drawing sites), exceeding the material's ductility limit, triggering microcracks or macroscopic fractures, and reducing the yield rate. 3. Residual stress causes subsequent deformation: The residual stress after forming gradually releases during subsequent processing (such as cutting, welding) or use, causing secondary deformation of the part.
[0005] 4. Reduced forming limit: Internal stress limits the further plastic deformation ability of the material, making it difficult to achieve single-step forming of complex shapes. 5. Accelerated tool wear: The stress concentration area causes the forming tools (such as punches, rollers) to bear higher loads, accelerating wear.
[0006] Therefore, the existing technology has defects and needs improvement. Summary of the Invention
[0007] The technical problem to be solved by the present invention is to provide a progressive forming method and device capable of dynamically releasing stress in view of the problems existing in the prior art.
[0008] The technical solution of the present invention is as follows: A progressive forming device capable of dynamically releasing stress, comprising an upper bracket 1, a lower bracket 7, an upper spherical punch group mounted on the upper bracket 1, a lower spherical punch group mounted on the lower bracket 7, and a tool head 3. Both the upper bracket 1 and the lower bracket 7 are connected to a numerical control machine tool. The upper spherical punch group and the lower spherical punch group press on the sheet metal. The upper spherical punch group and the lower spherical punch group are linked to the numerical control machine tool program. The numerical control machine tool drives the upper spherical punch group and the lower spherical punch group to rotate correspondingly according to preset parameters and paths, moving the sheet metal to the theoretical contact position with the tool head 3. During this process, the position of the tool head 3 remains fixed, and only the sheet metal moves, realizing the progressive forming process.
[0009] In the progressive forming device capable of dynamically releasing stress, the upper spherical punch group includes four spherical punches, two of which are located on the X-axis and the other two are located on the Y-axis; the lower spherical punch group also includes four spherical punches and adopts the same arrangement as the upper spherical punch group.
[0010] In the progressive forming device capable of dynamically releasing stress, when it is necessary to move the sheet metal along the X-axis, under the drive of the numerical control machine tool, the upper spherical punch group in the X-axis direction rotates counterclockwise, the lower spherical punch group rotates clockwise, and the punch group in the X-axis direction follows; when it is necessary to move the sheet metal along the Y-axis, the same principle applies.
[0011] According to the incremental forming method capable of dynamically releasing stress of any of the above-mentioned devices, the CNC machine tool drives the upper spherical pressure head group and the lower spherical pressure head group to rotate accordingly according to preset parameters and paths, and moves the sheet metal to the theoretical contact position with the tool head 3. During this process, the position of the tool head 3 remains fixed, and only the sheet metal moves, thereby realizing the incremental forming process.
[0012] By adopting the above scheme, the present invention has the following beneficial effects: 1. Dynamic stress release, significantly reducing springback and residual stress: Plane movement of the spherical indenter: Through the active movement of the spherical indenter, the local pressure distribution is adjusted in real time during the forming process, so that the internal stress of the material is gradually released as the indenter moves, rather than accumulating all at once. Dynamic stress release reduces the amount of elastic recovery after forming and improves the dimensional accuracy of parts.
[0013] 2. Effectively alleviate the risk of local stress concentration and rupture: The spherical indenter is combined with the machine tool linkage program to adjust the movement trajectory in real time according to the forming shape, dispersing stress concentration in complex areas (such as corners and deep drawing areas). The rolling of the spherical indenter replaces the fixed friction of the traditional clamp, reducing local shear force and preventing the material from rupture due to insufficient ductility caused by excessive friction resistance. Improving the forming limit Single forming can achieve more complex geometric features.
[0014] 3. Extend tool life and reduce processing costs: The spherical indenter disperses local contact stress through dynamic movement, avoiding local high-load wear caused by fixed contact of traditional clamps. Lubrication optimization: The rolling contact of the indenter reduces friction heat accumulation, reduces the risk of high-temperature oxidation or adhesive wear on the tool surface, reduces the frequency of tool replacement and downtime, and saves significant comprehensive costs.
[0015] 4. Improve processing efficiency and process stability: Simplify machine tool movement: Actively move the platen to replace the XY direction movement of the machine tool, reduce the dynamic response delay of the machine tool, and shorten the idle travel time. Program linkage control: The platen movement path and the forming tool trajectory are optimized synchronously to avoid pauses or repeated corrections caused by insufficient coordination in traditional processes. It systematically solves the core problem caused by stress concentration in incremental forming, and has the advantages of high precision, high efficiency and low cost. Its innovative design not only improves the reliability of the current process, but also provides key technical support for the development of future intelligent and composite forming technologies. BRIEF DESCRIPTION OF THE DRAWINGS
[0016] Figure 1 It is a schematic diagram of the structure of the incremental forming device of the present invention; Figure 2 It is a schematic diagram of the structure of the incremental forming device of the present invention; Figure 3 It is a schematic diagram of the arrangement structure of the spherical pressure head group of the present invention; 1. Upper bracket, 2. Fixator, 3. Tool head, 4. Forming area, 5. Sheet metal, 6. Spherical punch, 7. Lower bracket; Detailed implementation mode
[0017] The present invention will be described in detail below in conjunction with specific embodiments.
[0018] Reference Figures 1 - 3 , a progressive forming device capable of dynamically releasing stress, including an upper bracket 1, a lower bracket 7, an upper spherical punch group installed on the upper bracket 1 and a lower spherical punch group installed on the lower bracket 7, and a tool head 3. Both the upper bracket 1 and the lower bracket 7 are connected to a numerical control machine tool. The upper spherical punch group and the lower spherical punch group are pressed against the sheet metal. The upper spherical punch group and the lower spherical punch group are linked to the numerical control machine tool program. The numerical control machine tool drives the upper spherical punch group and the lower spherical punch group to perform corresponding rotations according to preset parameters and paths to realize the movement of the sheet metal. During this process, the position of the tool head 3 remains fixed, and only the sheet metal moves to realize the progressive forming process.
[0019] Specifically, as Figure 3 shown, the upper spherical punch group includes four spherical punches, two of which are located on the X-axis and the other two are located on the Y-axis; the lower spherical punch group also includes four spherical punches and adopts the same arrangement as the upper spherical punch group. When it is necessary to move the sheet metal along the X-axis, the upper spherical punch group in the X-axis direction rotates counterclockwise, and the lower spherical punch group rotates clockwise, and the punch group in the X-axis direction follows. When it is necessary to move the sheet metal along the Y-axis, the same principle applies.
[0020] Step 1: The loading and unloading of the sheet metal on the machine tool are completed by the rotation of the upper punch. When loading is required, the upper bracket is lifted upward. After placing the sheet metal, the upper punch clamps the sheet metal downward.
[0021] Step 2: The cooperation relationship between the machine tool and the punch is that the machine tool controls the rolling of the punch. When it is necessary for the punch to move the sheet metal in the positive X-axis direction, the upper punches of the two groups of punches in the x direction rotate counterclockwise, the lower punches rotate clockwise, and the punches in the y direction follow. The same principle applies when it is necessary to move in the y direction.
[0022] Step 3: In the CAD / CAM software, first, it is necessary to establish a three-dimensional model of the basic target workpiece. After completing the three-dimensional model, the corresponding numerical control code is automatically generated by the software.
[0023] Step 4: Install the selected tool head on the progressive forming machine tool to ensure its reliable and stable connection with the machine tool.
[0024] Step 5: Perform standard positioning on the sheet metal. During the positioning process, specific positioning is required according to the geometric shape and processing requirements to be processed to ensure the accuracy of positioning.
[0025] Step 6: After positioning is completed, the generated numerical control code is used for machining. At this time, the machine tool will perform automated operations according to the preset parameters and paths. When the trajectory of the traditional motion mode requires the tool head to move in the positive X-axis direction, the spherical indenter in this patent will drive the sheet material to move in the negative X-axis direction. For example, when the diameter of the spherical indenter is 100 mm and it needs to move 500π mm in the positive X-axis direction, the motor drives the spherical indenter to rotate 5 circles, which can make the sheet material move a distance of 500π mm. The distance that the spherical indenter drives the sheet material to move is the diameter of the spherical indenter multiplied by π. The mutual cooperation relationship between each roller can be obtained through conversion to meet the conversion between the traditional code and the code of this device.
[0026] After machining is completed, the operator removes the machined sheet material from the machine tool, and the springback phenomenon of the sheet material is greatly improved. This is because the indenter moves back and forth during the machining process (the spherical indenter rolls back and forth, enabling the sheet material to move to the position where it theoretically contacts the tool head), and the continuous rolling of the indenter releases the stress of the sheet material. At this time, the forming effect of the sample is in line with the expectation, with good appearance and flatness, providing a guarantee for subsequent applications.
[0027] It should be understood that for those of ordinary skill in the art, improvements or changes can be made according to the above description, and all such improvements and changes should fall within the protection scope of the appended claims of the present invention.
Claims
1. A progressive forming device capable of dynamically releasing stress, characterized in that, It includes an upper bracket (1), a lower bracket (7), an upper spherical indenter group installed on the upper bracket (1), a lower spherical indenter group installed on the lower bracket (7), and a tool head (3). Both the upper bracket (1) and the lower bracket (7) are connected to a numerical control machine tool. The upper spherical indenter group and the lower spherical indenter group press on the sheet metal. The upper spherical indenter group and the lower spherical indenter group are linked to the numerical control machine tool program. The numerical control machine tool drives the upper spherical indenter group and the lower spherical indenter group to perform corresponding rotations according to preset parameters and paths, and moves the sheet metal to the theoretical contact position with the tool head (3). During this process, the position of the tool head (3) remains fixed, and only the sheet metal moves to achieve the incremental forming process.
2. The incremental forming device capable of dynamically releasing stress according to claim 1, wherein, The upper spherical indenter group includes four spherical indenters, two of which are located on the X-axis and the other two are located on the Y-axis; the lower spherical indenter group also includes four spherical indenters and adopts the same layout as the upper spherical indenter group.
3. The incremental forming device capable of dynamically releasing stress according to claim 1, characterized in that, When it is necessary to move the sheet metal along the X-axis, under the drive of the numerical control machine tool, the upper spherical indenter group in the X-axis direction rotates counterclockwise, and the lower spherical indenter group rotates clockwise, and the indenter group in the X-axis direction follows; when it is necessary to move the sheet metal along the Y-axis, the same principle applies.
4. The incremental forming method capable of dynamically releasing stress for the device according to any one of claims 1-3, wherein the numerical control machine tool drives the upper spherical indenter group and the lower spherical indenter group to perform corresponding rotations according to preset parameters and paths, and moves the sheet metal to the theoretical contact position with the tool head (3). During this process, the position of the tool head (3) remains fixed, and only the sheet metal moves to achieve the incremental forming process.