Forming method based on combination of multi-pass drawing and wedge forming

Abstract

According to the fillet thin-wall forming method based on multi-pass deep drawing and wedge forming composition, after a rectangular shell is formed through multi-pass deep drawing, the circumferential wall and the bottom fillet of the shell are trimmed through a wedge forming die, and fillet thin-wall forming is achieved. Shaping of the peripheral wall and the bottom fillet of the rectangular box is achieved through the wedge forming device, the axial tensile stress borne by a material at the bottom fillet of a blank is greatly reduced, and therefore the fillet thinning rate is remarkably reduced; and during die assembly, the terrace die, the tapered wedge block, the peripheral wall concave die and the bottom concave die have a strong restraining effect on the periphery, the bottom and a round corner of a blank, so that the thin-wall shell can be effectively prevented from wrinkling.

Description

Technical Field

[0001] This invention relates to a technology in the field of metal forming, specifically a forming method based on a combination of multi-pass deep drawing and wedge forming. Background Technology

[0002] The battery boxes of existing electric vehicles generally adopt a small rounded rectangular thin shell design. Conventional rigid mold deep drawing forming process is prone to cracking when manufacturing small peripheral walls and bottom rounded corner features of the shell. The current method of axial upsetting sidewalls to form small bottom rounded corners cannot be applied to the forming of such parts because the sidewalls are too high and are prone to compressive instability. Summary of the Invention

[0003] This invention addresses the problems of thinning and cracking at the bottom rounded corners of products in existing multi-pass deep drawing forming processes, as well as the gaps between the forming block, positioning plate, and forming die at the side and bottom rounded corner areas, forming unconstrained areas. Local loading during forming can easily lead to wrinkling in the unconstrained areas of the shell, resulting in low precision of the rounded corner areas of the product. The invention proposes a rounded corner thin-wall forming method based on a combination of multi-pass deep drawing and wedge forming. The wedge forming device shapes the peripheral wall and bottom rounded corners of the rectangular box, significantly reducing the axial tensile stress on the material at the bottom rounded corners of the blank, thereby significantly reducing the rounded corner thinning rate. During mold closing, the punch, wedge block, peripheral die, and bottom die provide strong constraint on the blank's perimeter, bottom, and rounded corners, effectively preventing wrinkling of the thin-walled shell.

[0004] This invention is achieved through the following technical solution:

[0005] This invention relates to a rounded corner thin-wall forming method based on a combination of multi-pass deep drawing and wedge forming. After forming a rectangular shell through multi-pass deep drawing, the perimeter wall and bottom rounded corners of the shell are trimmed using a wedge forming mold to achieve rounded corner thin-wall forming.

[0006] The multi-pass deep-drawn rectangular shell has the same overall dimensions of length, width, and height as the final part, except that the side wall fillets and bottom fillets are larger than the fillets of the final part.

[0007] The wedge forming mold includes: four wedge blocks, a punch, a bottom die, and a peripheral die arranged sequentially from top to bottom, wherein the four wedge blocks are symmetrically and orientably arranged on the punch.

[0008] The wedge block includes a main wedge surface, a side wedge surface, and two vertical surfaces, wherein a stepped groove is provided between the main wedge surface and the side wedge surface, and a limiting block is provided on the main wedge surface.

[0009] The punch is a polyhedral structure with four symmetrically arranged side concave cavities. The shape of each side concave cavity matches the wedge block. A convex ridge is provided between two adjacent side concave cavities, and each side concave cavity is provided with an open rectangular groove corresponding to a limiting block.

[0010] The concave inner cavity and the upper surface of the punch are provided with a rounded corner.

[0011] The aforementioned directional movement setting refers to: the main and side wedge surfaces of the wedge block slide in contact with the inclined surface of the punch, the wedge block moves directionally along the inclined surface, the stepped groove on the wedge block and the corresponding protrusion on the punch cooperate to enhance the guiding effect on the wedge block, and the limiting block on the wedge block cooperates with the open rectangular groove on the punch to realize the control of the movement stroke of the wedge block.

[0012] The aforementioned wedge block and punch, in the mold-closed state, have outer surfaces that match the shape and size of the inner surface of the final part.

[0013] The peripheral wall cavity includes a cavity surface with rounded side corners and a rounded top corner.

[0014] The bottom cavity includes a cavity surface with four rounded bottom corners.

[0015] The peripheral wall die and bottom die, when in the mold-closed state, have inner cavity surfaces that match the shape and size of the final part's outer surface, and together with the wedge block and the outer surface of the punch, they form a constraint on the blank, preventing wrinkling of the blank during corner trimming.

[0016] The trimming process involves placing the rectangular shell, after multiple deep-drawing processes, into the cavities of the bottom die and the peripheral die. The press controls the punch to move downwards under pressure until its bottom contacts the upper surface of the bottom die, shaping the bottom rounded corners. At this point, the wedge moves down to a position 6mm above the upper surface of the punch. The punch remains stationary, and the press applies downward pressure to the wedge. The wedge moves along its surface by a set displacement to complete the shaping of the remaining rounded corners on the peripheral wall and bottom. During the wedge forming process, the press's downward speed is set to 1-5mm / s. After forming, the punch and wedge return, and the blank and bottom die are ejected under the action of a counter-force, completing the final removal of the rectangular box. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of multi-pass deep drawing and wedge forming;

[0018] In the diagram: 1. Wedge block; 2. Punch; 3. Bottom die; 4. Peripheral die.

[0019] Figure 2 A schematic diagram illustrating the process of obtaining parts through multi-pass deep drawing and wedge forming;

[0020] In the figure: (a) Part after multiple deep drawing passes; (b) Part after wedge forming.

[0021] Figure 3 This is a schematic diagram showing the movement of the wedge block and punch during wedge forming;

[0022] Wherein: (a) the moment when the bottom of the punch contacts the bottom die; (b) the moment when the wedge forming is completed;

[0023] In the figure: (a) front view, (b) left view, (c) top view, (d) isometric side view;

[0024] Figure 4 Flowchart of multi-pass deep drawing and wedge forming composite process;

[0025] Figure 5 This is a schematic diagram of the wedge forming process;

[0026] In the figure: (a) front view, (b) left view, (c) top view, (d) isometric side view;

[0027] In the diagram: 5. Stepped groove, 7. Limiting block, 9. Main inclined wedge surface, 10. Side inclined wedge surface, 11. Two vertical surfaces;

[0028] Figure 6 This is a schematic diagram of the punch used in the wedge forming process;

[0029] In the figure: (a) front view, (b) left view, (c) top view, (d) isometric side view;

[0030] In the diagram: 6 raised ridges, 8 open rectangular grooves, 12 concave inner cavities, 13 rounded corners;

[0031] Figure 7 This is a schematic diagram of the peripheral wall cavity mold for the wedge forming process;

[0032] In the diagram: 14. Side wall fillet, 15. Top fillet, 16. Cavity surface;

[0033] Figure 8 This is a schematic diagram of the bottom cavity die in the wedge forming process;

[0034] In the diagram: 17. Bottom rounded corners; 18. Cavity surface;

[0035] Figure 9 This is a diagram of a five-pass deep drawing process;

[0036] Figure 10 The diagram shows the thinning and forming limits of a five-pass deep drawing part.

[0037] Figure 11 This is a diagram showing the thinning process and forming limit of a five-pass deep drawing and wedge composite forming part. Detailed Implementation

[0038] like Figure 1 , Figure 2 , Figure 3 , Figure 4 As shown, this embodiment uses a combination of multi-pass deep drawing and wedge forming. A rectangular shell is formed by multi-pass deep drawing, and the perimeter wall and bottom rounded corners of the shell are trimmed by the wedge forming die to achieve the forming of the target part of the thin-walled box with small rounded corners. The forming die includes a wedge block 1, a punch 2, a bottom die 3 and a perimeter die 4.

[0039] The target part has the following outer dimensions: length 200mm, width 75mm, height 105mm, peripheral wall radius 2mm, and bottom radius 1.5mm.

[0040] like Figure 9 As shown, the multi-pass deep drawing refers to drawing a 0.2mm thick 304 stainless steel sheet in five passes to obtain a blank with a length of 200mm, a width of 75mm, a height of 105mm, a peripheral wall radius of 8mm, and a bottom radius of 3mm; for comparison, Figure 9 The paper also provides a process design drawing for traditional five-pass deep drawing direct forming with a peripheral wall radius of 2mm and a bottom radius of 1.5mm.

[0041] The wedge block 1 is provided with a stepped groove 5, which cooperates with the protruding rib 6 located at the corresponding position on the punch 2 to enhance the guiding effect on the wedge.

[0042] The wedge 1 has a limiting block 7 on its main wedge surface 9 for controlling the stroke, and the corresponding punch 2 has an open rectangular groove 8 that matches the limiting block.

[0043] like Figure 4 As shown, the main wedge surface 9 and the side wedge surface 10 of the wedge 1 form angles of 12° and 28° with the vertical edge, respectively. The rounded corners between the two vertical surfaces 11 and the corners intersecting with the bottom surface are used to shape the peripheral wall and part of the bottom rounded corners of the product.

[0044] The main inclined wedge surface 9 and the side inclined wedge surface 10 are connected by a guide step.

[0045] like Figure 6 As shown, the concave inner cavity 12 of the punch 2 matches the shape of the wedge 1 and is integrated into a rectangular core; the rectangular groove 8 on the main wedge surface cooperates with the wedge limiting block 7 to adjust the movement stroke of the wedge.

[0046] The bottom of the punch 2 is provided with a rounded corner 13 for shaping the bottom rounded corner of the product.

[0047] like Figure 7 and Figure 8As shown, the bottom cavity 3 is an inlaid cavity, the peripheral cavity 4 is a thick-walled rectangular cavity with a hollow center, the side wall rounded corner 14 is used to shape the peripheral wall rounded corner of the product, and the upper rounded corner 15 is the blank transition area.

[0048] The upper surface of the bottom die is a rounded corner shaping cavity 18 for the bottom of the product; the use of an interlocking die structure improves the processability.

[0049] The aforementioned wedge forming refers to: placing the blank after the fifth deep drawing between the bottom die 3, the peripheral die 4, the punch 2, and the wedge block 1. The bottom die 3 and the peripheral die 4 remain fixed, while the punch 2 moves downward under the drive of the press slide, causing the wedge block 1 to move downward synchronously, pulling the blank into the cavity of the peripheral die 4; the punch 2 moves down to contact the cavity surface 18, completing the shaping of the bottom part of the blank's rounded corners. At this time, the wedge 1 moves down to a position 6mm above the upper surface of the punch 2; then the punch 2 remains stationary, and the press applies downward pressure to the wedge block 1. The wedge block 1 moves along the wedge surface with a set displacement of 6.86mm, completing the shaping of the remaining rounded corners of the peripheral wall and bottom; during the wedge forming process, the press's downward movement speed is set to 1-5mm / s; after forming is completed, the punch 2 and the wedge 1 return, and the blank and the bottom die 3 are ejected under the action of the counter-ejection force, completing the final removal of the rectangular box.

[0050] The aforementioned trimming process involves pre-lubricating the wedge forming device with ordinary deep drawing oil.

[0051] Through simulation verification using the finite element software dynaform, material parameters and mold shape were input into the software. The deformation process of the billet was simulated using the mold movement modes of the traditional five-pass deep drawing process and the combined five-pass deep drawing and wedge forming process. The simulation data obtained are as follows:

[0052] In the forming process design of this product, the original traditional process adopted a five-stage deep drawing process, as shown in the process diagram. Figure 8 As shown, the maximum thinning in the bottom fillet area of ​​the final pass is 50%. The forming limit diagram indicates that cracking has occurred during this forming process. The thinning rate of the formed part is as follows: Figure 9 As shown; this invention employs a five-pass deep drawing and wedge forming composite process, and redesigns the shape of the fifth pass mold, enlarging the sidewall and bottom fillets from R2 and R1.5 to R8 and R3 respectively, as shown. Figure 8 As shown, after the fifth pass, all dimensions of the part, except for the fillets, met the product requirements. Finally, a wedge forming process was used to obtain the small fillets on the sidewalls and bottom. The maximum thinning of the bottom fillet area was reduced to 30%. The forming limit diagram shows that no cracking occurred during the forming process. The thinning rate of the formed part is as follows: Figure 10 As shown.

[0053] Compared with existing technologies, the wedge forming process of this invention adopts a bulging and shaping method, overcoming the disadvantage of continuous thinning of the bottom rounded corner during conventional deep drawing, thus improving the forming stress of the bottom rounded corner and reducing its thinning. To achieve the forming of rectangular boxes with small rounded corners while controlling a certain thinning rate, existing research often increases the number of deep drawing passes. This multi-pass deep drawing combined with wedge forming process can complete the forming of small rounded corners in one pass, and the thinning rate meets production requirements. This not only improves material flow at the bottom rounded corners and effectively reduces the thinning of the bottom rounded corners, but also reduces the number of deep drawing passes, thereby increasing production efficiency.

[0054] The above-described specific implementations can be partially adjusted by those skilled in the art in different ways without departing from the principles and purpose of the present invention. The scope of protection of the present invention is defined by the claims and is not limited to the above-described specific implementations. All implementation schemes within the scope of the claims are bound by the present invention.

Claims

1. A method for forming a round corner thin-walled part based on a combination of multi-pass deep drawing and wedge forming, characterized in that, After the rectangular shell is formed by multi-pass deep drawing, the peripheral wall and the bottom round corner of the shell are trimmed and round corner thin wall forming is realized by using a wedge forming die; The wedge forming die comprises four wedge blocks, a punch, a bottom die and a peripheral wall die arranged from top to bottom, wherein the four wedge blocks are symmetrically and movably arranged on the punch, and the outer surfaces of the wedge blocks and the punch match the shape and size of the inner surface of the final part in the closed die state.

2. The method of claim 1, wherein the method is a multi-stage drawing and wedge forming combined round corner thin wall forming method, characterized in that, The wedge block comprises a main wedge surface, a side wedge surface and two vertical surfaces, wherein a stepped groove is arranged between the main wedge surface and the side wedge surface, and a limiting block is arranged on the main wedge surface. The punch is a polyhedral structure with four symmetrically arranged side recessed cavities, and the shape of each side recessed cavity matches the wedge block, wherein a convex edge is arranged between two adjacent side recessed cavities, and an open rectangular slot corresponding to the limiting block is arranged on each side recessed cavity.

3. The method of claim 2, wherein the method is a multi-stage drawing and wedge forming combined round corner thin wall forming method, characterized in that, A round corner is arranged between the side recessed cavity and the upper surface of the punch.

4. The method of claim 2, wherein the method is a multi-stage drawing and wedge forming combined round corner thin wall forming method, characterized in that, The directional and movable arrangement refers to the sliding contact between the main and side wedge surfaces of the wedge block and the inclined surface of the punch, the directional movement of the wedge block along the inclined surface, the cooperation of the stepped groove arranged on the wedge block and the convex edge arranged at the corresponding position of the punch to strengthen the guiding effect of the wedge block, and the cooperation of the limiting block arranged on the wedge block and the open rectangular slot arranged on the punch to control the movement stroke of the wedge block.

5. The method of claim 1, wherein the method is a multi-stage drawing and wedge forming combined round corner thin wall forming method, characterized in that, The peripheral wall die comprises a cavity surface with a side wall round corner and an upper round corner, and the bottom die comprises a cavity surface with four bottom round corners. In the closed die state, the inner cavity surface of the peripheral wall die and the bottom die matches the shape and size of the outer surface of the final part, and together with the outer surfaces of the wedge block and the punch, it forms a constraint on the blank to prevent wrinkling of the blank during round corner trimming.

6. The method of claim 1, wherein the method is a multi-stage drawing and wedge forming combined round corner thin wall forming method, characterized in that, The trimming refers to placing the rectangular shell with shaped round corners after multi-pass deep drawing into the cavity of the bottom die and the peripheral wall die, moving the punch downward under the control of the press, contacting the bottom of the punch with the upper surface of the bottom die to shape the bottom round corner, keeping the punch stationary when the wedge moves downward to above the upper surface of the punch, applying downward pressure on the wedge block by the press, moving the wedge block along the wedge surface to set the displacement, and completing the shaping of the remaining round corners of the peripheral wall and the bottom; after the forming is completed, the punch and the wedge return, the blank and the bottom die are ejected under the action of the counterforce, and the final rectangular box is ejected.

7. The method according to claim 6, wherein, In the wedge forming process, the speed of the press is set to 1-5 mm / s.

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