A forming device and forming method for a small rounded stepped box-shaped part

Abstract

The present invention relates to the field of sheet metal forming technology, and specifically provides a forming device and a forming method for a stepped box-shaped part with small rounded corners, wherein the forming device for the stepped box-shaped part with small rounded corners comprises a shaping die and a shaping mechanism, wherein a preform is placed between the shaping die and the shaping mechanism, and the shaping mechanism is used to push and expand the rounded corner area of ​​the preform; the shaping mechanism comprises a shaping block and a central frustum. The preform is placed between the shaping die and the shaping mechanism, and the liquid outlet and the through hole on the shaping block cooperate to connect with a low-temperature medium, and when the shaping rounded corner portion of the shaping block contacts the rounded corner area of ​​the preform, the liquid outlet sprays liquid nitrogen to locally cool the rounded corner area of ​​the preform, thereby improving the deformation resistance of the rounded corner area of ​​the preform, making it less likely to undergo local over-thinning, and reducing the risk of local thinning and rupture during shaping of the rounded corner area.

Description

Technical Field

[0001] The present invention relates to the technical field of sheet metal forming, and in particular to a forming device and a forming method for a small-radius stepped box-shaped part. Background Art

[0002] Stepped box-shaped parts are widely used in industrial production, especially in automobiles, aircraft and electrical products. Box-shaped parts with small fillet radius can have a larger storage space, making the product space utilization higher, and have always been the preferred solution for designers. However, parts with small fillet radius are extremely difficult to form, which brings great difficulties to production.

[0003] At present, there are two main types of forming schemes for small-radius stepped box-shaped parts: one is die-casting, which can effectively form stepped box-shaped parts with very small radius and complex structure, but this method has low production efficiency, high cost, and is difficult to form large-sized thin-walled components. The second is multi-pass deep drawing, which has high production efficiency and low cost, but due to the plasticity of the material, the material flow in the small-radius area of ​​the stepped box-shaped part is difficult during the multi-pass forming process, and rupture defects are prone to occur, especially when the radius of the fillet is less than 4 times the plate thickness, this defect is more difficult to avoid.

[0004] Therefore, the existing technical methods have problems such as difficulty in forming small fillet features, easy transition thinning of the fillet, necking resulting in cracking, and difficulty in obtaining suitable preforms. Summary of the invention

[0005] The present invention aims to solve at least one aspect of the above technical problems.

[0006] To solve the above problems, the present invention proposes the following technical solutions:

[0007] A forming device for a small-rounded stepped box-shaped part, comprising a shaping die and a shaping mechanism, wherein a preformed part is placed between the shaping die and the shaping mechanism, and the shaping mechanism is used to push and expand the rounded corner area of ​​the preformed part;

[0008] The shaping mechanism comprises a shaping block and a central frustum, wherein an inclined surface is arranged on the inner side of the shaping block, and the inclined surface is used for slidingly cooperating with the side surface of the central frustum, and when the shaping die moves in the vertical direction, the central frustum acts on the shaping block, so that the shaping block moves in the horizontal direction to realize the pushing and expanding shaping of the fillet area of ​​the preform;

[0009] A shaping rounded corner portion is formed on the outer side of the shaping block, and the shaping rounded corner portion is used to contact the rounded corner area of ​​the preform. The surface of the shaping rounded corner portion is provided with evenly distributed liquid outlet holes. A through hole is provided inside the shaping block, one end of the through hole is connected to the liquid outlet hole, and the other end of the through hole is connected to a low-temperature medium source.

[0010] The forming device and forming method of a small rounded stepped box-shaped part provided by the present invention have, compared with the prior art, but are not limited to the following beneficial effects:

[0011] In the forming device of the small rounded stepped box-shaped part, the shaping die and the shaping rounded corner part of the shaping mechanism cooperate to push and expand the preformed part, wherein the preformed part is placed between the shaping die and the shaping mechanism, and the liquid outlet and the through hole on the shaping block cooperate to be connected with the low-temperature medium. When the shaping rounded corner part of the shaping block contacts the rounded corner area of ​​the preformed part, the liquid outlet sprays liquid nitrogen to locally cool the rounded corner area of ​​the preformed part, thereby improving the deformation resistance of the rounded corner area of ​​the preformed part. When the shaping die and the shaping mechanism pressurize the preformed part, the preformed part is driven to The material around the rounded corner area of ​​the preform enters the rounded corner area to achieve push-expansion shaping. In this structure, the rounded corner area of ​​the preform is cooled, so that the flow stress of the material in the rounded corner area is increased, and local excessive thinning is not easy to occur. The material far away from the rounded corner area is still at room temperature, and its deformation resistance is smaller than that of the material in the rounded corner area. The push-expansion shaping process in the rounded corner area of ​​the preform can yield earlier than the material in the rounded corner area. Therefore, the rounded corner area can be supplemented with material, reducing the risk of local thinning and rupture during shaping of the rounded corner area.

[0012] Preferably, the shaping mechanism further comprises a sliding mold frame, and the sliding mold frame is provided with a sliding groove;

[0013] The lower end surface of the shaping block is provided with a sliding block, and the sliding block is used for sliding connection with the sliding groove. The sliding block cooperates with the sliding groove so that the shaping block can move horizontally on the sliding mold frame.

[0014] Preferably, the slide groove is inclined from the inside of the sliding mold frame toward the rounded corner area of ​​the preformed part, and the sliding block is also inclined to cooperate with the slide groove and is arranged on the lower end surface of the shaping block.

[0015] Preferably, the shaping block is provided with two auxiliary surfaces, the two auxiliary surfaces are arranged on both sides of the shaping rounded corner portion, and the two auxiliary surfaces are arranged at an angle, and the two auxiliary surfaces are respectively matched with two adjacent side walls of the preformed part.

[0016] Preferably, the shaping mechanism further comprises an elastic member;

[0017] Auxiliary grooves are provided on the two auxiliary surfaces of the shaping block, and positioning plates are provided on the four sides of the central cone facing the auxiliary grooves. The upper end of the positioning plate is used to adapt to the auxiliary grooves, one end of the elastic member is fixedly connected to the inner wall of the auxiliary groove, and the other end of the elastic member is used to abut against the side wall of the positioning plate.

[0018] Preferably, it further comprises a lower die base, the positioning plate and the central frustum are both arranged on the lower die base, a nitrogen spring is installed on the lower die base, and the upper end of the nitrogen spring is used to connect with the sliding die frame.

[0019] Preferably, it also includes an upper die seat, and the shaping die is arranged on the lower end surface of the upper die seat;

[0020] A guide column is arranged on the lower die seat, and a guide sleeve matching the guide column is arranged on the lower end surface of the upper die seat, and the guide sleeve is used for sliding connection with the guide column.

[0021] The present invention also provides a method for forming a small rounded stepped box-shaped piece, using the above-mentioned small rounded stepped box-shaped piece forming device, comprising the following steps:

[0022] S1. According to the three-dimensional model of the target stepped box-shaped part, a preforming device, a forming device for the rounded stepped box-shaped part and a final forming device are designed and assembled, and the size of the preformed sheet, the fillet radius of the lower part of the preformed part and the fillet radius of the shaping part are determined;

[0023] S2, determining the blank holding force, liquid chamber pressure, and loading path during preforming according to the preforming device and the preformed sheet material, and optimizing these three parameters;

[0024] S3, after the preforming device is installed, the preformed sheet is placed between the preformed liquid chamber and the preformed blank holder, and the preformed sheet is positioned by a positioning mechanism;

[0025] S4, a preforming blank holder is installed on the outer slide of the double-action press, and the outer slide of the double-action press is controlled to move downward so that the working surface of the preforming blank holder contacts the preforming sheet material, and then the preforming liquid chamber is filled with liquid;

[0026] A preforming punch is installed on the inner slide of the double-action press, and the inner slide of the double-action press is controlled to move downward, so that the bottom of the preforming punch contacts the preforming sheet material, undergoes elastic-plastic deformation, and forms the preformed part;

[0027] S5, placing the preform upside down on the shaping mechanism of the rounded stepped box-shaped part forming device, and spraying a cooling medium through the rounded corner shaping portion to cool the rounded corner area of ​​the preform;

[0028] S6, the upper die seat moves downward until the shaping die contacts the preformed part. When the fillet area of ​​the preformed part cools to below -150°C, the upper die seat continues to move downward, and the preformed part, the shaping block and the sliding die frame move downward together. During this process, the shaping block is forced to move outward, pulling a portion of the material on the side of the preformed part into the fillet area, so that the fillet area of ​​the preformed part is gradually pressed against the inner wall of the shaping die to form a shaped part.

[0029] S7, the upper die seat maintains the set displacement for 5-10 seconds, then stops inputting the low-temperature medium, and the upper die seat drives the shaping die upward. Under the action of the nitrogen spring, the sliding die frame, the shaping block and the sliding die frame are reset accordingly. At the same time, under the action of the elastic member, the shaping block moves inward to achieve demoulding;

[0030] S8, placing the shaping piece in the final forming floating die of the final forming device, and at this time, under the action of the final forming spring, the working surface of the final forming floating die and the working surface of the fixed die are at the same horizontal position;

[0031] S9. A final forming pressure ring is installed on the outer slider of the double-acting press on the final forming device, and a final forming stepped punch is installed on the inner slider of the double-acting press on the final forming device. The outer slider of the double-acting press is controlled to move downward until the working surface of the final forming pressure ring contacts the pressure part of the shaping part. Then, the inner slider of the double-acting press is controlled to move downward to the bottom of the final forming step punch contacts the bottom of the shaping part and continues to move downward to compress the final forming spring. The reaction force generated by the compression of the final forming spring enables the final forming floating die and the final forming step punch to completely wrap the bottom of the shaping part in the mold cavity, thereby avoiding deformation of the bottom formed area of ​​the shaping part during the final forming process, and limiting the deformation in the final forming process to the flange area of ​​the shaping part, so that on the basis of ensuring the accuracy of the lower formed area, the pressure part of the shaping part is pressed out of the step to form a stepped box-shaped part.

[0032] Preferably, the height of the preformed part is higher than the preset height of the stepped box-shaped part, and the rounded corners of the preformed part are larger than the rounded corners of the shaping part.

[0033] Preferably, the rounded corner area of ​​the shaping die, the rounded corner portion of the shaping block and the rounded corner area of ​​the shaping piece are consistent in size. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic diagram of the overall structure of a forming device for a small-rounded stepped box-shaped piece according to an embodiment of the present invention;

[0035] Figure 2 A schematic diagram of the shaping mechanism structure of an embodiment of the present invention;

[0036] Figure 3 A schematic diagram of the shaping block structure of an embodiment of the present invention;

[0037] Figure 4 It is a schematic cross-sectional structure diagram of a forming device for a small-rounded stepped box-shaped piece according to an embodiment of the present invention;

[0038] Figure 5 This is a schematic diagram of the structure of a preformed part and a shaping part according to an embodiment of the present invention;

[0039] Figure 6 Schematic diagram of the cross-sectional structure of a preforming device and a preformed sheet material according to an embodiment of the present invention;

[0040] Figure 7 Schematic diagram of the cross-sectional structure of a preforming device and a preformed part according to an embodiment of the present invention;

[0041] Figure 8 This is a schematic diagram of the structure of a preform according to an embodiment of the present invention;

[0042] Fig. 9 It is a schematic cross-sectional structure diagram of a final forming device and a shaping piece according to an embodiment of the present invention;

[0043] Fig.10 is a schematic cross-sectional structural diagram of a final forming device and a stepped box-shaped member according to an embodiment of the present invention;

[0044] Fig.11 It is a schematic diagram of the structure of the preformed sheet, preformed part, shaping part and stepped box-shaped part according to an embodiment of the present invention.

[0045] Description of reference numerals:

[0046] 1 shaping die; 2 shaping mechanism; 21 shaping block; 210 through hole; 2100 slider; 22 center cone; 23 inclined surface; 24 shaping fillet; 240 liquid outlet; 25 sliding die frame; 250 slide groove; 26 auxiliary surface; 260 auxiliary groove; 27 elastic member; 28 positioning plate; 280 guide surface; 29 nitrogen spring; 3 lower die seat; 30 guide column; 4 upper die seat; 40 guide sleeve; 5 preformed sheet ; 51 pre-forming liquid chamber; 52 pre-forming pressure ring; 53 pre-forming punch; 54 pre-forming upper pad; 55 pre-forming lower pad; 6 pre-forming part; 60 groove; 600 pressure part; 7 shaping part; 71 final forming floating die; 72 final forming spring; 73 fixed die; 74 final forming pressure ring; 75 final forming stepped punch; 76 final forming upper pad; 77 final forming lower pad; 8 stepped box-shaped part. DETAILED DESCRIPTION

[0047] The following is a further detailed description of the implementation of the present application in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present application but cannot be used to limit the scope of the present application.

[0048] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by the terms "up", "down", "front", "back", "left", "right", etc. are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention.

[0049] It should be noted that the coordinate system XYZ provided in this paper (such as Figure 1 As shown in the figure, the positive direction of the X-axis represents the right, the reverse direction of the X-axis represents the left, the positive direction of the Y-axis represents the front, the reverse direction of the Y-axis represents the back, the positive direction of the Z-axis represents the top, and the reverse direction of the Z-axis represents the bottom; the meanings of the Z-axis, X-axis, and Y-axis are only for the convenience of describing the present 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 operate in a specific orientation, and therefore cannot be understood as limiting the present invention.

[0050] See also Figure 1-Figure 5 A forming device for a rounded stepped box-shaped part provided in an embodiment of the present invention comprises a shaping die 1 and a shaping mechanism 2, a preformed part 6 is placed between the shaping die 1 and the shaping mechanism 2, and the shaping mechanism 2 is used to push and expand the rounded corner area of ​​the preformed part 6.

[0051] See also Figure 1-Figure 2 The shaping mechanism 2 includes a shaping block 21 and a center frustum 22. A slope 23 is provided on the inner side of the shaping block 21. The slope 23 is used to slide with the side of the center frustum 22. When the shaping die 1 moves in the vertical direction, the center frustum 22 acts on the shaping block 21 to make the shaping block 21 move in the horizontal direction to achieve the pushing and expanding shaping of the fillet area of ​​the preform 6.

[0052] Specifically, a matching surface is provided on the outer wall of the central cone 22 , and the matching surface is arranged parallel to the inclined surface 23 .

[0053] In this embodiment, when the shaping die 1 moves downward, the center cone 22 approaches the preform 6, and the mating surface contacts and pushes the inclined surface 23 to push the shaping block 21 toward the inner wall of the shaping die 1 and together with the shaping die 1, push and shape the preform 6.

[0054] See also Figure 3A shaping fillet 24 is formed on the outer side of the shaping block 21, and the shaping fillet 24 is used to contact the fillet area of ​​the preform 6. The surface of the shaping fillet 24 is provided with evenly distributed liquid outlet holes 240. A through hole 210 is provided inside the shaping block 21, and one end of the through hole 210 is connected to the liquid outlet hole 240, and the other end of the through hole 210 is connected to a low-temperature medium source.

[0055] In this embodiment, in the forming device of the small rounded stepped box-shaped part, the shaping die 1 and the shaping rounded corner portion 24 of the shaping mechanism 2 cooperate to push and expand the preform 6, wherein the preform 6 is placed between the shaping die 1 and the shaping mechanism 2, and the liquid outlet 240 and the through hole 210 on the shaping block 21 cooperate to be connected with the low-temperature low-temperature medium, and when the shaping rounded corner portion 24 of the shaping block 21 contacts the rounded corner area of ​​the preform 6, the liquid outlet 240 sprays liquid nitrogen to locally cool the rounded corner area of ​​the preform 6, thereby improving the deformation resistance of the rounded corner area of ​​the preform 6, and the shaping When the die 1 and the shaping mechanism 2 apply pressure to the preform 6, the material around the rounded corner area of ​​the preform 6 is driven into the rounded corner area to achieve push-expansion shaping to obtain a shaped part 7. In this structure, the rounded corner area of ​​the preform 6 is cooled, so that the flow stress of the material in the rounded corner area is increased, and local excessive thinning is not easy to occur. The material far away from the rounded corner area is still at room temperature, and its deformation resistance is smaller than that of the material in the rounded corner area. The push-expansion shaping process in the rounded corner area of ​​the preform 6 can yield earlier than the material in the rounded corner area, so the rounded corner area can be supplemented with material, reducing the risk of local thinning and rupture during shaping of the rounded corner area.

[0056] See also Figure 2 Preferably, the shaping mechanism 2 further comprises a sliding mold frame 25, and a sliding groove 250 is provided on the sliding mold frame 25;

[0057] A slider 2100 is provided on the lower end surface of the shaping block 21 . The slider 2100 is used for sliding connection with the slide groove 250 . The slider 2100 cooperates with the slide groove 250 to enable the shaping block 21 to move horizontally on the sliding mold frame 25 .

[0058] Specifically, a through hole is provided in the middle of the sliding mold frame 25, and the upper end of the center cone 22 is used to penetrate the through hole. When the upper end of the center cone 22 penetrates the through hole, the mating surface of the outer wall of the center cone 22 contacts the inclined surface 23 and pushes the inclined surface 23 to push the shaping block 21 toward the inner wall direction of the shaping die 1 and together with the shaping die 1, push and expand the preform 6.

[0059] In this embodiment, the sliding mold frame 25 provides an installation carrier for the shaping block 21, and the slide groove 250 and the slider 2100 cooperate with each other, so that the shaping block 21 can move in a set direction and is beneficial to avoid position displacement of the shaping block 21 during the movement, thereby helping to improve the processing effect of the preform 6.

[0060] See also Figure 2 Preferably, the slide groove 250 is inclined from the inside of the sliding mold frame 25 toward the rounded corner area of ​​the preform 6, and the slider 2100 is also inclined to cooperate with the slide groove 250 on the lower end surface of the shaping block 21.

[0061] In this embodiment, the slide groove 250 is obliquely arranged on the sliding mold frame 25, and the slider 2100 is obliquely arranged on the lower end surface of the shaping block 21. This structure enables the slider 2100 and the slide groove 250 to cooperate, and the shaping block 21 moves from the inside of the sliding mold frame 25 toward the outer wall of the sliding mold frame 25, that is, moves toward the rounded corner area close to the preform 6. This structure enables the shaping rounded corner portion 24 of the shaping block 21 to directly contact the rounded corner area of ​​the preform 6, which is beneficial to improve the processing effect of the preform 6 and avoid the shaping rounded corner portion 24 contacting other parts of the preform 6 and causing unnecessary deformation.

[0062] Preferably, the shaping block 21 is provided with two auxiliary surfaces 26 , which are arranged on both sides of the shaping fillet portion 24 and are arranged at an angle, and the two auxiliary surfaces 26 are respectively adapted to two adjacent side walls of the preform 6 .

[0063] Specifically, the preform 6 as a whole is a hollow rectangular box body, and the two adjacent side walls of the preform 6 are vertically arranged, so the two auxiliary surfaces 26 on the shaping block 21 are also vertically arranged. The preform 6 has four rounded corners, and accordingly, four shaping blocks 21 are arranged corresponding to the four rounded corners of the preform 6.

[0064] In this embodiment, when the shaping block 21 moves toward the inner wall of the shaping die 1 and pushes and expands the preform 6 together with the shaping die 1, the setting of the auxiliary surface 26 is beneficial to ensuring that the two adjacent side walls of the preform 6 are perpendicular to each other during the pushing and expanding shaping, thereby helping to improve the processing effect of the preform 6.

[0065] See also Figure 4 , preferably, the shaping mechanism 2 further includes an elastic member 27;

[0066] Auxiliary grooves 260 are provided on the two auxiliary surfaces 26 of the shaping block 21, and positioning plates 28 are provided on the four sides of the central cone 22 facing the auxiliary grooves 260. The upper end of the positioning plate 28 is used to adapt to the auxiliary grooves 260, one end of the elastic member 27 is fixedly connected to the inner wall of the auxiliary groove 260, and the other end of the elastic member 27 is used to abut against the side wall of the positioning plate 28.

[0067] Specifically, the elastic member 27 includes a spring, one end of which is fixedly connected to the inner wall of the auxiliary groove 260, and the other end of the spring abuts against the side wall of the positioning plate 28; or, the elastic member 27 includes a spring sheet, one end of which is fixedly connected to the inner wall of the auxiliary groove 260, and the other end of the spring abuts against the side wall of the positioning plate 28.

[0068] See also Figure 2 A guide surface 280 is provided at the connection between the side of the upper end of the positioning plate 28 away from the elastic member 27 and the upper end surface of the positioning plate 28. Under normal conditions, when the preform 6 is inverted onto the shaping mechanism 2 and the shaping die 1 is not pressed down, the elastic member 27 has no effect on the upper end of the positioning plate 28, and the upper end of the positioning plate 28 where the guide surface 280 is provided is partially inserted into the interior of the preform 6 and has no effect on the inner wall of the preform 6.

[0069] See also Figure 4-Figure 5 In this embodiment, when the shaping die 1 moves downward, the center cone 22 approaches the preform 6, and the matching surface contacts the inclined surface 23 and pushes the inclined surface 23 to push the shaping block 21 to move toward the inner wall of the shaping die 1. When the shaping block 21 moves, the elastic member 27 abuts against the upper end of the positioning plate 28. At the same time, the preform 6 moves over the guide surface 280 of the positioning plate 28. The middle position of the positioning plate 28; when the shaping block 21 and the shaping die 1 cooperate to push and expand the preformed part 6 to form the shaping part 7, the shaping die 1 moves upward, and at the same time, the elastic member 27 pushes the shaping block 21 to reset and pushes the upper end of the positioning plate 28 to move outward until the shaping part 7 is loosened from the guide surface 280 at the upper end of the positioning plate 28, thereby facilitating the removal of the shaping part 7 from the shaping mechanism 2 and facilitating demoulding.

[0070] See also Figure 1Preferably, it also includes a lower die base 3, the positioning plate 28 and the center cone 22 are both arranged on the lower die base 3, and a nitrogen spring 29 is installed on the lower die base 3, and the upper end of the nitrogen spring 29 is used to connect with the sliding die frame 25.

[0071] In this embodiment, the nitrogen spring 29 is used to support the sliding die frame 25 and the shaping block 21, so that the sliding die frame 25 is located at a suitable position above the central frustum 22; when the shaping die 1 moves downward and extrude the preform 6 with the shaping mechanism 2, the shaping die 1 will also press down the shaping block 21 and the sliding die frame 25, so that the central frustum 22 passes through the sliding die frame 25 to push the shaping block 21 to move. In this process, The nitrogen spring 29 is squeezed; after the preformed part 6 is pushed and expanded to form the shaping part 7, the shaping die 1 moves upward, and the nitrogen spring 29 is reset, so that the sliding mold frame 25 moves upward, and the shaping block 21 is reset by the elastic member 27, and the upper end of the positioning plate 28 is pushed to move outward until the shaping part 7 is relaxed from the guide surface 280 at the upper end of the positioning plate 28, thereby facilitating the removal of the shaping part 7 from the shaping mechanism 2 and facilitating demoulding.

[0072] Preferably, it further comprises an upper die seat 4, and the shaping die 1 is arranged on the lower end surface of the upper die seat 4;

[0073] A guide post 30 is disposed on the lower die base 3 , and a guide sleeve 40 matching the guide post 30 is disposed on the lower end surface of the upper die base 4 . The guide sleeve 40 is used for sliding connection with the guide post 30 .

[0074] In this embodiment, the upper die base 4 provides a mounting carrier for the shaping die 1, and a driving device drives the upper die base 4 to move up and down, thereby driving the shaping die 1 to move up and down. During the up and down movement of the upper die base 4, the guide column 30 and the guide sleeve 40 cooperate with each other, so that the upper die base 4 and the shaping die 1 are aligned with the shaping mechanism 2, thereby avoiding the problem of position offset affecting the shaping effect.

[0075] See also Figure 1-Figure 11 The present invention also provides a method for forming a small rounded stepped box-shaped piece, using the above-mentioned rounded stepped box-shaped piece forming device, comprising the following steps:

[0076] S1. According to the three-dimensional model of the target stepped box-shaped part 8, the preforming device, the rounded stepped box-shaped part forming device and the final forming device are designed and assembled, and the size of the preformed sheet 5, the rounded corner radius of the lower part of the preformed part 6 and the rounded corner radius of the shaping part 7 are determined.

[0077] Preferably, the rounded corners of the preformed part 6 are larger than the rounded corners of the shaping part 7 .

[0078] Specifically, the fillet radius of the shaping piece 7 is set to no more than 4 times the thickness of the preformed sheet 5, and the fillet radius of the lower part of the preformed piece 6 is enlarged to 6-8 times the thickness of the preformed sheet 5. The preformed sheet 5 is processed into the preformed piece 6 by the preforming device, and then the preformed piece 6 with a larger fillet radius is processed into the shaping piece 7 by the forming device of the rounded stepped box-shaped piece, and finally the shaping piece 7 is processed into a stepped box-shaped piece 8 by the final forming device.

[0079] In this embodiment, this method is suitable for forming a stepped box-shaped part 8 with a very small fillet radius and a complex structure. Since the rounded stepped box-shaped part is usually designed to have a very small fillet radius, generally not exceeding 4 times the thickness of the preformed sheet 5, and sometimes even less than 2 times the thickness of the preformed sheet 5, the preformed device cannot directly form the lower part of the small rounded stepped box-shaped part. In the present invention, the preformed sheet needs to be rounded twice before the final step box-shaped part 8 is obtained. First, the preformed sheet 5 is processed into a preformed part 6 with a larger fillet radius, and then the preformed part 6 is processed into a plastic part 7 with a smaller fillet radius.

[0080] Preferably, the height of the preform 6 is higher than the preset height of the stepped box-shaped part 8 .

[0081] In this embodiment, the height of the preform 6 is higher than the preset height of the step box-shaped part 8, so that material is reserved at the upper edge of the preform 6 for pressing out a double-layer step, which is beneficial to ensure that the final step box-shaped part 8 meets the original design requirements.

[0082] S2. Determine the blank holding force, liquid chamber pressure, and loading path during preforming according to the preforming device and the preforming sheet material 5, and optimize these three parameters.

[0083] See also Figure 6-Figure 7Specifically, the preforming device includes a preforming upper pad 54, a preforming punch 53, a preforming pressure ring 52, a preforming liquid chamber 51 and a preforming lower pad 55. The preforming upper pad 54 is connected to the outer slider of the double-acting press by bolts, and the preforming pressure ring 52 is installed to the bottom of the preforming upper pad 54 by bolts. A through hole 210 is opened in the middle of the preforming upper pad 54 so that the preforming punch 53 can be connected to the inner slider of the double-acting press; the shape of the preforming punch 53 is designed according to the inner wall size of the lower half of the target stepped box-shaped part 8, the preforming liquid chamber 51 is installed on the preforming lower pad 55, and the preforming lower pad 55 is connected to the worktable of the double-acting press by bolts. A guide column is set between the preforming upper pad 54 and the preforming lower pad 55 to ensure that the preforming upper pad 54 and the preforming lower pad 55 are aligned during the preforming process.

[0084] S3. After the preforming device is installed, the preforming sheet material 5 is placed between the preforming liquid chamber 51 and the preforming blank holder 52, and the preforming sheet material 5 is positioned by a positioning mechanism.

[0085] See also Figure 7-Figure 8 , S4, a preforming blank holder 52 is installed on the outer slide of the double-action press, and the outer slide of the double-action press is controlled to move downward so that the working surface of the preforming blank holder 52 contacts the preforming sheet 5, and then the preforming liquid chamber 51 is filled with liquid;

[0086] A preforming punch 53 is installed on the inner slide of the double-action press. When the inner slide of the double-action press is controlled to move downward, the bottom of the preforming punch 53 contacts the preforming sheet 5, undergoes elastic-plastic deformation, and forms the preformed part 6.

[0087] In this embodiment, when the preforming punch 53 is descending, the preforming punch 53 pushes the preforming sheet 5, and the preforming punch 53 and the preforming liquid chamber 51 cooperate to deform the preforming sheet 5 into a preformed part 6. The preformed part 6 has a rectangular groove 60 in the middle, and the four sides of the groove 60 have a pressing edge portion 600 perpendicular to the side wall of the groove 60.

[0088] See also Figure 1-Figure 5 S5, remove the preform 6 from the preform device, and invert the preform 6 on the shaping mechanism 2 of the shaping device for the small-radius stepped box-shaped part, and cool the rounded area of ​​the preform 6 by spraying cooling medium through the rounded corner shaping part 24.

[0089] Preferably, the rounded corner area of ​​the shaping die 1 , the rounded corner portion 24 of the shaping block 21 , and the rounded corner area of ​​the shaping member 7 are consistent in size.

[0090] In this embodiment, the fillet radius of the shaping piece 7 is set to be no more than 4 times the thickness of the preformed sheet 5, and the fillet area of ​​the shaping die 1, the shaping fillet portion 24 of the shaping block 21 and the fillet area of ​​the shaping piece 7 are of the same size. This structure is conducive to processing a shaping piece 7 that meets the requirements.

[0091] See also Figure 4 , S6, the upper die base 4 descends to the shaping die 1 and contacts the preform 6. When the rounded area of ​​the preform 6 is cooled to below -150°C, the upper die base 4 continues to descend, and the preform 6, the shaping block 21 and the sliding die frame 25 descend together. During this process, the shaping block 21 is forced to move outward, pulling a part of the material on the side of the preform 6 into the rounded area, so that the rounded area of ​​the preform 6 is gradually pressed against the inner wall of the shaping die 1 to form a shaping part 7.

[0092] In this embodiment, the liquid outlet 240 on the rounded corner shaping portion 24 is connected to the through hole 210, so that the low-temperature medium can be sprayed to the rounded corner area at the lower part of the preform 6 through the through hole 210 and the liquid outlet 240, so that the temperature of the sheet material in the rounded corner area is reduced, thereby increasing the flow stress of the material of the preform 6, and preventing local excessive thinning. The material far away from the rounded corner area of ​​the preform 6 is still at room temperature, and its deformation resistance is smaller than that of the material in the rounded corner area. During the rounded corner pushing and expanding shaping process, it can yield earlier than the material in the rounded corner area. Therefore, the rounded corner area can be supplemented with material, reducing the risk of local thinning and rupture during shaping of the rounded corner area.

[0093] S7, after the upper die base 4 reaches the set displacement, it remains for 5-10s, and then the input of low-temperature medium is stopped. The upper die base 4 drives the shaping die 1 upward, and under the action of the nitrogen spring 29, the sliding die frame 25, the shaping block 21 and the sliding die frame 25 are reset accordingly. At the same time, under the action of the elastic member 27, the shaping block 21 moves inward to achieve demolding.

[0094] In this embodiment, the preformed part 6 moves over the guide surface 280 of the positioning plate 28 to the middle position of the positioning plate 28; when the shaping block 21 and the shaping die 1 cooperate to push and expand the preformed part 6 to form the shaping part 7, the shaping die 1 moves upward, and the nitrogen spring 29 is reset, so that the sliding mold frame 25 moves upward. Under the reset action of the elastic member 27, the shaping block 21 is reset and pushes the upper end of the positioning plate 28 to move outward until the shaping part 7 is loosened from the guide surface 280 at the upper end of the positioning plate 28, thereby facilitating the removal of the shaping part 7 from the shaping mechanism 2 for easy demoulding.

[0095] See also Figure 9-10 , S8, placing the shaping piece 7 in the final forming floating die 71 of the final forming device. At this time, under the action of the final forming spring 72, the working surface of the final forming floating die 71 and the working surface of the fixed die 73 are at the same horizontal position.

[0096] Specifically, the final forming device includes a final forming upper pad 76, a final forming stepped punch 75, a final forming blank holder 74, a final forming fixed die 73, a final forming floating die 71, a final forming spring 72 and a final forming lower pad 77. The final forming upper pad 76 is bolted to the outer slider of the double-acting press, the final forming blank holder 74 is bolted to the bottom of the final forming upper pad 76, a through hole 210 is opened in the center of the final forming upper pad 76 so that the final forming stepped punch 75 is connected to the inner slider of the double-acting press, and the shape of the final forming stepped punch 75 is designed according to the overall inner wall size of the target stepped box-shaped part. The final forming fixed die 73 is mounted on the final forming lower pad 77 by bolts. The cavity and working surface dimensions of the final forming fixed die 73 are obtained by adding a fixed gap to the outer wall dimension of the upper half of the target stepped box-shaped part. The fixed gap is 1.05-1.10 times the thickness of the preformed sheet 5. The final forming floating die 71 is connected to the final forming lower pad 77 by the final forming spring 72. The final forming floating die 71 provides a supporting reaction force after being compressed by the final forming spring 72 during the final forming process. The cavity and working surface dimensions of the final forming floating die 71 are obtained by adding a fixed gap to the outer wall dimension of the lower half of the target stepped box-shaped part. The fixed gap is 1.05-1.10 times the thickness of the preformed sheet 5. The final forming lower pad 77 is connected to the worktable of the double-acting press by bolts. A guide column is arranged between the final forming upper pad 76 and the final forming lower pad 77 to ensure that the final forming upper pad 76 and the final forming lower pad 77 are aligned during the final forming process. In actual production, the shaping piece 7 is placed between the final forming floating die 71 and the final forming blank holder 74 for processing.

[0097] See also Fig.10 , S9, a final forming pressure ring 74 is installed on the outer slider of the double-acting press on the final forming device, and a final forming stepped punch 75 is installed on the inner slider of the double-acting press on the final forming device. The outer slider of the double-acting press is controlled to move downward until the working surface of the final forming pressure ring 74 contacts with the pressure part 600 of the shaping member 7, and then the inner slider of the double-acting press is controlled to move downward to the bottom of the final forming step punch 75 contacts with the bottom of the shaping member 7, and continues to move downward to push and expand the final forming spring 72, so that the pressure part 600 of the shaping member 7 is pressed out of a step, thereby forming a stepped box-shaped member 8.

[0098] In the present invention, the deformation resistance of the rounded corner area is improved by locally cooling the rounded corner area, thereby driving the material around the rounded corner area into the rounded corner area, which can effectively avoid the problem of excessive thinning of the rounded corner area and subsequent rupture during the shaping of the rounded box-shaped part, resulting in difficulty in forming; when processing the step, the edge pressing portion 600 pressed out by the pre-forming device is used for the second deep drawing process, which greatly reduces the difficulty of forming the step; the entire forming process is simple and easy to operate, with a high degree of automation, which can greatly improve production efficiency, shorten the production cycle of the product, and reduce manufacturing costs.

[0099] Although the disclosure is disclosed as above, the protection scope of the disclosure is not limited thereto. Those skilled in the art may make various changes and modifications without departing from the spirit and scope of the disclosure, and these changes and modifications will fall within the protection scope of the present invention.

Claims

1. A forming device for a small rounded stepped box-shaped part, characterized in that: It comprises a shaping die (1) and a shaping mechanism (2), wherein a preformed part (6) is placed between the shaping die (1) and the shaping mechanism (2), and the shaping mechanism (2) is used to perform push-expansion shaping on the fillet area of ​​the preformed part (6); The shaping mechanism (2) comprises a shaping block (21) and a central frustum (22); an inclined surface (23) is provided on the inner side of the shaping block (21); the inclined surface (23) is used to slide with the side surface of the central frustum (22); when the shaping die (1) moves in the vertical direction, the central frustum (22) acts on the shaping block (21) to make the shaping block (21) move in the horizontal direction to achieve the pushing and expanding shaping of the fillet area of ​​the preform (6); A shaping fillet (24) is formed on the outside of the shaping block (21), the shaping fillet (24) being used to contact the fillet area of ​​the preform (6), the surface of the shaping fillet (24) being provided with evenly distributed liquid outlet holes (240), the inside of the shaping block (21) being provided with a through hole (210), one end of the through hole (210) being connected to the liquid outlet hole (240), and the other end of the through hole (210) being connected to a low-temperature medium source.

2. The forming device for a small rounded stepped box-shaped piece according to claim 1, characterized in that: The shaping mechanism (2) further comprises a sliding mold frame (25), and a sliding groove (250) is provided on the sliding mold frame (25); The lower end surface of the shaping block (21) is provided with a sliding block (2100), and the sliding block (2100) is used to be slidably connected with the sliding groove (250). The sliding block (2100) cooperates with the sliding groove (250) to enable the shaping block (21) to move in a horizontal direction on the sliding mold frame (25).

3. The forming device for a small rounded stepped box-shaped piece according to claim 2, characterized in that: The slide groove (250) is arranged obliquely from the inside of the sliding mold frame (25) toward the rounded corner area of ​​the preformed part (6), and the sliding block (2100) is also arranged obliquely on the lower end surface of the shaping block (21) in coordination with the slide groove (250).

4. The forming device for a small rounded stepped box-shaped part according to claim 3, characterized in that: The shaping block (21) is provided with two auxiliary surfaces (26), the two auxiliary surfaces (26) being arranged on both sides of the shaping fillet portion (24), and the two auxiliary surfaces (26) being arranged at an angle, and the two auxiliary surfaces (26) are respectively adapted to two adjacent side walls of the preformed part (6).

5. The forming device for a small rounded stepped box-shaped piece according to claim 4, characterized in that: The shaping mechanism (2) further comprises an elastic member (27); Auxiliary grooves (260) are provided on the two auxiliary surfaces (26) of the shaping block (21), and positioning plates (28) are provided on the four sides of the central cone (22) facing the auxiliary grooves (260). The upper end of the positioning plate (28) is used to match the auxiliary grooves (260), one end of the elastic member (27) is fixedly connected to the inner wall of the auxiliary groove (260), and the other end of the elastic member (27) is used to abut against the side wall of the positioning plate (28).

6. The forming device for a small rounded stepped box-shaped piece according to claim 5, characterized in that: It also includes a lower die base (3), the positioning plate (28) and the center cone (22) are both arranged on the lower die base (3), and a nitrogen spring (29) is installed on the lower die base (3), and the upper end of the nitrogen spring (29) is used to connect with the sliding die frame (25).

7. The forming device for a small rounded stepped box-shaped piece according to claim 6, characterized in that: It also comprises an upper die seat (4), the shaping die (1) being arranged on the lower end surface of the upper die seat (4); A guide column (30) is provided on the lower die base (3), and a guide sleeve (40) matching the guide column (30) is provided on the lower end surface of the upper die base (4), wherein the guide sleeve (40) is used for being slidably connected with the guide column (30).

8. A method for forming a small rounded stepped box-shaped part, characterized in that: The forming device of the small rounded stepped box-shaped part according to claim 7 comprises the following steps: S1. According to the three-dimensional model of the target stepped box-shaped part, a preforming device, a forming device for the stepped box-shaped part with small rounded corners and a final forming device are designed and assembled, and the size of the preformed sheet (5), the rounded corner radius of the lower part of the preformed part (6) and the rounded corner radius of the shaping part are determined; S2, determining the blank holding force, liquid chamber pressure, and loading path during preforming according to the preforming device and the preformed sheet material (5); S3, after the preforming device is installed, the preforming sheet material (5) is placed between the preforming liquid chamber (51) and the preforming blank holder (52), and the preforming sheet material (5) is positioned by a positioning mechanism; S4, a preforming blank holder (52) is installed on the outer slide of the double-action press, and the outer slide of the double-action press is controlled to move downward so that the working surface of the preforming blank holder (52) contacts the preforming sheet material (5), and then the preforming liquid chamber (51) is filled with liquid; A preforming punch (53) is installed on the inner slide of the double-action press, and the inner slide of the double-action press is controlled to move downward, so that the bottom of the preforming punch (53) contacts the preforming sheet material (5), undergoes elastic-plastic deformation, and forms the preformed part (6); S5, placing the preform (6) upside down on the shaping mechanism (2) of the shaping device for the small-rounded stepped box-shaped part, and spraying a cooling medium through the rounded corner shaping part (24) to cool the rounded corner area of ​​the preform (6); S6, the upper die seat (4) descends to the shaping die (1) and contacts the preform (6), and when the rounded corner area of ​​the preform (6) is cooled to below -150°C, the upper die seat (4) continues to descend, and the preform (6), the shaping block (21) and the sliding die frame (25) descend together. During this process, the shaping block (21) is forced to move outward, pulling a portion of the material on the side of the preform (6) into the rounded corner area, so that the rounded corner area of ​​the preform (6) is gradually pressed against the inner wall of the shaping die (1), forming a shaping piece (7); S7, after the upper die seat (4) reaches the set displacement, it is maintained for 5-10 seconds, and then the input of the low-temperature medium is stopped, and the upper die seat (4) drives the shaping die (1) upward, and under the action of the nitrogen spring (29), the shaping block (21) and the sliding die frame (25) are reset accordingly, and at the same time, under the action of the elastic member (27), the shaping block (21) moves inward to achieve demoulding; S8, placing the shaping piece (7) in the final forming floating die (71) of the final forming device, and at this time, under the action of the final forming spring (72), the working surface of the final forming floating die (71) and the working surface of the fixed die (73) are at the same horizontal position; S9, a final forming blank holder (74) is installed on the outer slide of the double-acting press on the final forming device, and a final forming stepped punch (75) is installed on the inner slide of the double-acting press on the final forming device, and the outer slide of the double-acting press is controlled to move downward until the working surface of the final forming blank holder (74) contacts the blank holder (600) of the shaping member (7), and then the inner slide of the double-acting press is controlled to move downward until the bottom of the final forming stepped punch (75) contacts the bottom of the shaping member (7), and continues to move downward, so as to press the final forming spring (72) The final forming spring (72) is compressed, and the reaction force generated by the compression causes the final forming floating die (71) and the final forming stepped punch (75) to completely wrap the bottom of the shaping part (7) in the mold cavity, thereby preventing the bottom formed area of ​​the shaping part (7) from deforming during the final forming process, and limiting the deformation in the final forming process to the flange area of ​​the shaping part (7), so that the edge pressing part (600) of the shaping part (7) is pressed out of the step while ensuring the accuracy of the lower formed area, thereby forming a stepped box-shaped part (8).

9. The method for forming a small-radius stepped box-shaped part according to claim 8, characterized in that: The height of the preformed part (6) is higher than the preset height of the stepped box-shaped part (8), and the rounded corners of the preformed part (6) are larger than the rounded corners of the shaping part (7).

10. The method for forming a small-radius stepped box-shaped part according to claim 8, characterized in that: The rounded corner area of ​​the shaping die (1), the shaping rounded corner portion (24) of the shaping block (21) and the rounded corner area of ​​the shaping piece (7) are of the same size.

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