A method for controlling edge wrinkling in a sheet metal part incremental forming process

Abstract

This invention relates to a method for controlling edge wrinkling during the progressive forming process of sheet metal parts, comprising the following steps: analyzing the target sheet metal part, generating a processing trajectory, determining the outer edge geometry of the flat base material, designing an auxiliary back plate, and selecting the materials of the upper and lower auxiliary plates; placing the flat base material between the upper and lower auxiliary plates, which are fixed by the auxiliary back plate and a clamping table; processing with a tool head; and obtaining the target sheet metal part. Compared with the prior art, this invention has the advantages of controlling wrinkling of parts by setting four aspects: the planar progressive forming processing trajectory, the shape of the flat base material, the shape of the auxiliary back plate, and the materials of the upper and lower auxiliary plates, thereby improving the geometric accuracy of thin-walled sheet metal parts. It is particularly suitable for sheet metal parts with easily wrinkled edges during progressive forming; it requires no extensive experimental foundation, no custom molds, hydraulic presses, or tool heads, and significantly reduces the difficulty of wrinkling control.

Description

Technical Field

[0001] This invention relates to the progressive forming process of sheet metal parts, and more particularly to a method for controlling edge wrinkling during the progressive forming process of sheet metal parts. Background Technology

[0002] Wrinkling is a typical defect in thin sheet forming. It frequently occurs in various thin sheet forming processes when process conditions are not properly set, requiring improvement and optimization of the forming process to eliminate it. For some thin-walled sheet metal parts, when using a three-sheet free incremental forming process, such as the one described in the literature "Investigations on the deformation mechanism of a novel three-sheet incremental forming" (Journal of Materials Processing Tech., Volume 281, June 2020, 116619), the boundary of the intermediate target plate is not fixedly constrained, and the thinning of the outer edge is not obvious, but wrinkling is very easy to occur, failing to meet the requirements of geometric accuracy. Lopez-Fernandez et al., in the literature "Wrinkling in shrink flanging by single point incremental forming" (International Journal of Mechanical Sciences, Volume 240, November 2022, 107930), predicted the wrinkling phenomenon of sheet metal during incremental forming shrinkage flanging through experiments and simulations, and established a corresponding process window. However, this method requires a large number of experiments and cannot be extended to industrial applications. To control wrinkling in sheet metal parts, current methods use rigid molds controlled by hydraulic presses or multi-point molds to provide a certain blank holder force. However, this method is difficult to apply in progressive forming processes. To address edge wrinkling of the intermediate target plate during the free progressive forming of three-layer sheets, a new flexible control method is needed.

[0003] A search revealed that application publication number CN109550833A discloses a progressive forming method and equipment for frame edge parts. Specifically, it discloses that the frame edge parts are formed by deep drawing sheet metal through multiple pressings of the upper die of a forming equipment. The progressive forming method includes the following steps: selecting the amount of sheet metal to be pressed into the upper die; placing multiple wrinkle-suppressing blocks or one wrinkle-suppressing block on each side of the upper die according to the amount of pressing; the bottom surface of the multiple wrinkle-suppressing blocks or one wrinkle-suppressing block is higher than the bottom surface of the upper die by a difference, the difference being equivalent to the amount of pressing; and pressing the upper die down until a predetermined position is reached. However, this method mainly uses rigid wrinkle-suppressing blocks to replace the pressure ring, suppressing the generation of wrinkles and eliminating existing wrinkles during the manufacturing process of the frame edge parts. It still belongs to the field of deep drawing and differs significantly from the progressive forming process of sheet metal parts in terms of forming principle and technology.

[0004] In summary, controlling the edge wrinkling of the intermediate target plate during the free progressive forming process of a three-layer plate is a technical problem that needs to be solved. Summary of the Invention

[0005] The purpose of this invention is to overcome the defect of edge wrinkling of the intermediate target plate in the free progressive forming process of three-layer plates in the prior art, and to provide a method for controlling edge wrinkling in the progressive forming process of sheet metal parts.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] According to one aspect of the present invention, a method for controlling edge wrinkling during the progressive forming process of sheet metal parts is provided for the manufacturing of flat sheet metal base materials. The method employs an auxiliary back plate, an upper auxiliary plate, a lower auxiliary plate, a clamping table, and a tool head for processing, and specifically includes the following steps:

[0008] Step S1: Analyze the structure of the target sheet metal part and generate the machining trajectory;

[0009] Step S2: Determine the outer edge geometry of the flat base material based on the axial projection of the target sheet metal part.

[0010] Step S3: Design an auxiliary backplate based on the geometric features of the outer edge of the target sheet metal part and the dimensions of the clamping table;

[0011] Step S4: Select the upper auxiliary plate material and the lower auxiliary plate material according to the material of the target sheet metal part;

[0012] Step S5: Place the flat base material between the upper auxiliary plate and the lower auxiliary plate, and fix the upper auxiliary plate and the lower auxiliary plate by the auxiliary back plate and the clamping table.

[0013] Step S6: The tool head moves along the machining trajectory generated in step S1 to perform machining;

[0014] Step S7: After processing is completed, the target sheet metal part is obtained.

[0015] As a preferred technical solution, in step S1, the machining trajectory is offset outward by a distance equal to the radius of the tool head compared to the original machining dimension.

[0016] As a preferred technical solution, the processing trajectory is circular, and the diameter of the two annular layers at the top of the processing trajectory is 5-10 mm larger than the size of the flat substrate.

[0017] As a preferred technical solution, in step S2, the geometry of the outer edge of the flat substrate is based on the two-dimensional projection shape of the top edge along the axial direction, and each edge is rounded.

[0018] As a preferred technical solution, in step S3, the inner edge shape of the auxiliary back plate is offset outward by 3-5 mm from the outer edge geometry of the flat substrate.

[0019] As a preferred technical solution, in step S4, the upper auxiliary plate is made of metal with a strength greater than or equal to that of the flat base material.

[0020] As a preferred technical solution, in step S4, the lower auxiliary plate is made of metal, and its strength is less than that of the flat plate base material.

[0021] As a preferred technical solution, in step S5, the flat substrate is placed centered on the lower auxiliary plate, and the upper and lower auxiliary plates are aligned and installed.

[0022] As a preferred technical solution, step S6 specifically involves the tool head applying downward pressure to the upper auxiliary plate, causing the flat base material and the lower auxiliary plate to undergo plastic deformation simultaneously.

[0023] As a preferred technical solution, after obtaining the target sheet metal part in step S7, edge inspection and geometric accuracy measurement are performed. If it does not meet the manufacturing requirements, steps S1 to S4 are adjusted.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1) This invention sets four aspects: planar progressive forming processing trajectory, flat base material shape, auxiliary back plate shape, and upper and lower auxiliary plate materials, which can improve the geometric accuracy of thin-walled sheet metal parts and control the wrinkling of parts. It is especially suitable for sheet metal parts with easily wrinkled edges during progressive forming.

[0026] 2) This invention does not require extensive experimental foundation, custom molds and hydraulic presses, has low manufacturing cost, and significantly reduces the difficulty of wrinkle control;

[0027] 3) This invention does not require custom-shaped wrinkle-reducing blocks or tool heads; it can be achieved using conventional tool heads with hemispherical ends. Attached Figure Description

[0028] Figure 1 This is a flowchart of a method for controlling edge wrinkling during the progressive forming process of sheet metal parts according to the present invention.

[0029] Figure 2 This is a schematic diagram of the progressive forming process of the present invention;

[0030] Figure 3 This is the planar progressive forming process trajectory for the truncated cone component of the present invention;

[0031] Figure 4 This is a top view of the circular flat substrate with rounded corners according to the present invention;

[0032] Figure 5 This is a front view of the auxiliary backplate of the present invention;

[0033] The numbers in the diagram are as follows:

[0034] 1. Flat base material; 10. Rounded corners; 2. Auxiliary back plate; 3. Upper auxiliary plate; 4. Lower auxiliary plate; 5. Clamping table; 6. Machining trajectory. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0036] This invention utilizes the compressive stress in the thickness direction provided by the upper and lower auxiliary plates during progressive forming to suppress wrinkling of the target sheet metal part. The compressive stress in the thickness direction on the target sheet metal part is controlled by selecting the material type and thickness of the upper and lower auxiliary plates.

[0037] Example 1

[0038] like Figure 1 As shown, this invention provides a method for controlling edge wrinkling during the progressive forming process of sheet metal parts. To control edge wrinkling of the target sheet metal part, the method includes: planar progressive forming trajectory design, flat base material 1 shape design, auxiliary back plate 2 design, and material selection of upper and lower auxiliary plates. It includes the following steps:

[0039] S1: Analyze the structural features of the target sheet metal part and generate a progressive forming planar forming machining trajectory 6 for the sheet metal part, ensuring that the machining trajectory 6 can completely enclose the CAD model of the sheet metal part to be formed.

[0040] S2: Determine the outline shape of the flat base material 1 and cut it according to the axial projection of the target sheet metal part;

[0041] S3: Design and manufacture the auxiliary backplate 2 based on the geometric features of the outer edge of the target sheet metal part and the dimensions of the clamping table 5.

[0042] S4: Based on the material of the target sheet metal part, select 1-2 types of upper auxiliary plate 3 materials with higher strength, and cut and process them;

[0043] S5: Based on the material of the target sheet metal part, select 1-2 types of lower auxiliary plate 4 materials with lower strength and cut them for processing;

[0044] S6: Place the processed auxiliary back plate 2 on the clamping table 5, align the upper auxiliary plate 3, the flat base material 1 and the lower auxiliary plate 4, and place them on the clamping table 5 in sequence and fix them.

[0045] S7: The tool head performs progressive forming processing on the three-layer thin plate along a planar trajectory;

[0046] S8: After processing, remove the auxiliary plate and conduct a preliminary inspection of the target sheet metal part to observe whether its outer edge is wrinkled.

[0047] S9: Perform further contact or non-contact geometric accuracy measurements on the target sheet metal part, and adjust the processing parameters if necessary;

[0048] S10: By adjusting the materials of the upper and lower auxiliary plates 4, the planar trajectory method, and the shape of the flat base material 1, the wrinkling behavior of the target sheet metal is further suppressed, and the geometric accuracy of the target plate forming is improved.

[0049] like Figure 2 As shown, when a flat base material 1 with a certain initial shape is placed between the upper auxiliary plate 3 and the lower auxiliary plate 4, the edges of the flat base material 1 are never fixed and can extend freely. The upper auxiliary plate 3 and the lower auxiliary plate 4 are fixed by clamps. When the tool head moves along the predetermined processing trajectory 6, a certain downward pressure is applied to the upper auxiliary plate 3, causing the flat base material 1 and the lower auxiliary plate 4 to undergo plastic deformation simultaneously through contact. After the progressive forming is completed, the upper auxiliary plate 3 and the lower auxiliary plate 4 are removed to obtain the target sheet metal part with the set geometry.

[0050] like Figure 3 As shown, the planar progressive forming trajectory requires the digital model of the sheet metal part to be offset outward by the radius of a tool head, and the top two layers of the trajectory need to be 5-10mm larger than the size of the flat base material 1 to ensure that the tool head completely covers and processes the sheet metal along the trajectory.

[0051] like Figure 4As shown, the shape of the flat base material 1 has a certain influence on the control of wrinkling. The shape of the flat base material 1 is based on the two-dimensional projection shape of the top edge of the target sheet metal part along the axial direction. It is modified according to the actual forming accuracy. If the wrinkling control effect is not good, the size of the base material can be appropriately reduced to ensure that the trajectory completely covers the processing of the base material. At the same time, all edges of the flat base material 1 need to be rounded by 10 to reduce the cutting effect on the lower auxiliary plate 4.

[0052] like Figure 5 As shown, the inner edge shape of the auxiliary back plate 2 can be offset outward by 3-5mm from the outer edge geometry of the flat base material 1 to constrain the springback and wrinkling of the outer edge of the flat base material 1 and ensure the geometric accuracy of the target sheet metal part.

[0053] The upper auxiliary plate 3 is made of a metal plate with strength close to or exceeding that of the target sheet metal part. For example, if the sheet metal part to be formed is a high-strength aluminum alloy, the upper auxiliary plate 3 can be made of deep drawing steel or high-strength steel.

[0054] The lower auxiliary plate 4 is made of a metal plate with a strength significantly lower than that of the target sheet metal part. The lower the strength of the lower auxiliary plate 4, the better the wrinkling control effect. If the sheet metal part to be formed is a high-strength aluminum alloy, then the lower auxiliary plate 4 is made of a soft aluminum alloy.

[0055] Example 2

[0056] This invention provides a method for controlling edge wrinkling during the progressive forming process of sheet metal parts, mainly used for processing circular target sheet metal parts to control edge wrinkling. A circular high-strength aluminum alloy AA2024 flat base material 1 is placed between a square upper auxiliary plate 3 and a square lower auxiliary plate 4. The edges of the flat base material 1 are never fixed and can extend freely. The upper and lower auxiliary plates 4 are fixed by clamps. When the tool head moves along a predetermined planar trajectory, a certain amount of pressure is applied to the upper auxiliary plate 3, causing plastic deformation of both the target plate and the lower auxiliary plate through contact. After progressive forming is completed, the upper auxiliary plate 3 and the lower auxiliary plate 4 are removed to obtain the target sheet metal part with the set geometry. To control edge wrinkling of the flat base material 1, the planar progressive forming processing trajectory 6 can be offset 5mm outward from the digital model of the sheet metal part, and the top two layers of the trajectory must be 5-10mm larger than the size of the flat base material 1 to ensure that the tool head completely covers and processes the sheet metal along the trajectory.

[0057] Based on the two-dimensional projection shape of the top edge of the target sheet metal part along the axial direction, the geometric contour of the flat base material 1 is confirmed. According to the actual forming accuracy, certain modifications are made. Specifically, if the wrinkling control effect is not good, the size of the base material is reduced to ensure that the trajectory completely covers the processing of the base material. At the same time, each edge of the flat base material 1 needs to be rounded by 102mm to reduce the cutting effect on the lower auxiliary plate 4.

[0058] The inner edge shape of the auxiliary back plate 2 can be offset outward by 3-5mm from the outer edge geometry of the flat base material 1. Its function is to constrain the springback and wrinkling of the outer edge of the sheet metal part and ensure the geometric accuracy of the part.

[0059] The upper auxiliary plate 3 is made of SAPH440 steel, and the lower auxiliary plate 4 is made of AA5052 aluminum alloy.

[0060] This invention is applicable to the problem of wrinkling at the edges of general sheet metal parts, while sheet metal parts with non-cavity geometric features generally do not produce wrinkling defects.

[0061] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for controlling edge wrinkling during the progressive forming process of sheet metal parts, characterized in that, The manufacturing of the flat base material (1) is carried out using an auxiliary back plate (2), an upper auxiliary plate (3), a lower auxiliary plate (4), a clamping table (5), and a tool head. The specific steps include: Step S1: Analyze the structure of the target sheet metal part and generate the machining trajectory (6). Step S2: Determine the outer edge geometry of the flat base material (1) based on the axial projection of the target sheet metal part; Step S3: Design the auxiliary back plate (2) based on the geometric features of the outer edge of the target sheet metal part and the dimensions of the clamping table (5); Step S4: Select the material of the upper auxiliary plate (3) and the lower auxiliary plate (4) according to the material of the target sheet metal part; Step S5: Place the flat base material (1) between the upper auxiliary plate (3) and the lower auxiliary plate (4), and fix the upper auxiliary plate (3) and the lower auxiliary plate (4) through the auxiliary back plate (2) and the clamping table (5); In step S6, the tool head moves along the machining trajectory (6) generated in step S1 to perform machining; Step S7: After processing, the target sheet metal part is obtained; In step S1, the machining trajectory (6) is offset outward by a distance equal to the radius of the tool head compared to the original machining dimension; In step S2, the outer edge geometry of the flat substrate (1) is based on the two-dimensional projection shape of the top edge along the axial direction, and each edge is rounded (10). In step S4, the upper auxiliary plate (3) is made of metal and has a strength greater than or equal to that of the flat base material (1). In step S4, the lower auxiliary plate (4) is made of metal and has a strength less than that of the flat base material (1). In step S3, the inner edge shape of the auxiliary back plate (2) is offset outward by 3~5mm from the outer edge geometry of the flat substrate (1); The processing trajectory (6) is a ring, and the diameter of the two rings at the top of the processing trajectory (6) is 5~10mm larger than the size of the flat substrate (1).

2. The method for controlling edge wrinkling during the progressive forming process of sheet metal parts according to claim 1, characterized in that, In step S5, the flat substrate (1) is placed centered on the lower auxiliary plate (4), and the upper auxiliary plate (3) and the lower auxiliary plate (4) are aligned and installed.

3. The method for controlling edge wrinkling during the progressive forming process of sheet metal parts according to claim 1, characterized in that, The step S6 is specifically the application of downward pressure by the tool head to the upper auxiliary plate (3), which causes the flat base material (1) and the lower auxiliary plate (4) to undergo plastic deformation simultaneously.

4. The method for controlling edge wrinkling during the progressive forming process of sheet metal parts according to claim 1, characterized in that, After obtaining the target sheet metal part in step S7, edge inspection and geometric accuracy measurement are performed. If it does not meet the manufacturing requirements, steps S1 to S4 are adjusted.

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