Double-curvature deep cavity skin active bulging wall thickness uniform control mold and method

Abstract

The invention discloses a double-curvature deep cavity skin active bulging wall thickness uniform control mold and method. According to the method, two-step forming is achieved through a set of forming die, in the first step, reverse bulging is utilized, a plate is attached to an upper die for material storage, and in the second step, a final part state is formed through a lower die. According to the structural characteristics of the part, a groove structure is arranged on the periphery of the maximum thinning area of the material storage part of the upper die, the upper die part corresponding to the maximum thinning area is not provided with the groove structure, and the groove characteristics are formed in the first step. In the second step, forward bulging is conducted, the part formed in the first step is attached to the lower die, the thickness reduction of the bottom area of the skin part is reduced through the material storage groove structure of the upper die, the wall thickness of the double-curvature deep-cavity skin part is more uniform, and meanwhile the orange peel phenomenon caused by the thickness reduction can be reduced.

Description

Technical Field

[0001] The invention relates to a plastic forming method for a hyperbolic deep cavity skin part, in particular to a mold and method for controlling the active bulging wall thickness uniformity of a hyperbolic deep cavity skin. Background Art

[0002] Skin parts are usually formed using the skin stretching process. However, for skin parts with large curvature changes, large arch height, and reverse characteristic structures, since the two ends of the skin are supported by the equipment jaws during the skin stretching process, the sheet material will not flow, and the deformation of the parts depends entirely on the thinning of the sheet material. When the deformation is too large, it will produce orange peel or even cracking phenomena.

[0003] Therefore, this type of skin parts is suitable for the liquid bulging process. Under the condition of uniform liquid pressure loading, the flow of sheet metal can be realized to supplement the thinning area, thereby reducing the thinning rate of the parts. However, there is also a problem: in the hydraulic bulging process of deep-cavity skin parts, the sheet metal close to the edge of the part always fits with the mold first under the action of liquid pressure. This is completely opposite to the skin pulling process. The skin pulling sheet metal first fits with the area with a larger arch height, and finally the edge of the sheet metal fits with the mold. As the bulging continues, the bulging pressure becomes greater and greater. The sheet metal that has been fitted with the mold produces greater friction with the mold under the action of liquid pressure. Under certain pressure conditions, the sheet metal and the mold no longer move relative to each other, and the sheet metal in the deepest area of ​​the cavity cannot be supplemented, resulting in the deformation of the sheet metal in the deepest area of ​​the cavity completely relying on the thinning of the sheet metal, resulting in the largest thinning at the deepest center of the cavity, which may cause orange peel or even rupture at this location, especially for chemical milling parts, which have strict control over the thinning of parts.

[0004] Therefore, it is necessary to find a forming method and mold structure based on bulging to avoid thinning being too concentrated in one place to solve similar problems. Summary of the invention

[0005] The invention provides a mold and a method for controlling the uniform wall thickness of a hyperbolic deep cavity skin through active bulging.

[0006] The first aspect of the present invention provides a double-curvature deep cavity skin active bulging wall thickness uniform control die, comprising: an annular reverse groove structure 7, a boss structure 8, an upper die 11, a lower die 14, a lower die filling and draining channel 15, and an upper die filling and exhausting channel 16;

[0007] An annular reverse groove structure 7 is dug on the upper die 11, and a boss structure 8 is formed at the center of the annular reverse groove structure 7; the cross section of the annular reverse groove structure 7 is an arc;

[0008] The profile of the lower mold 14 is consistent with the profile of the double-curved deep cavity skin;

[0009] The sheet material is arranged between the upper die 11 and the lower die 14;

[0010] The upper mold 11 and the lower mold 14 are respectively provided with an upper mold filling and exhaust channel 16 and a lower mold filling and draining channel 15 for replenishing high-pressure liquid or exhausting air to the cavities of the upper mold 11 and the lower mold 14.

[0011] Optionally, the groove depth h of the annular reverse groove structure 7 is smaller than the profile height H of the lower mold 14 at the corresponding position in the vertical direction.

[0012] Optionally, the area of ​​the boss structure 8 is determined according to the profile structure of the hyperbolic deep cavity skin.

[0013] Optionally, the greater the hyperbolic curvature or the depth of the hyperbolic deep cavity skin, the larger the area of ​​the boss structure 8 .

[0014] Optionally, the height of the boss structure 8 is determined according to the groove depth h of the annular reverse groove structure 7 .

[0015] Optionally, the active bulging wall thickness uniformity control mold for the double-curvature deep cavity skin further includes: a calendering rib groove 5, a calendering rib convex rib 9, and a sealing groove 10;

[0016] The upper die 11 and the lower die 14 are provided with a convex rib 9 and a concave rib 5, respectively;

[0017] The upper die 11 is provided with a sealing groove 10 , which is arranged outside the convex rib 9 of the rolled rib.

[0018] Optionally, the double-curvature deep cavity skin active bulging wall thickness uniform control mold further includes: a liquid baffle 13;

[0019] A liquid baffle 13 is provided at the edge of the upper mold 11 to prevent high-pressure liquid from spraying.

[0020] Optionally, the profile of the lower die 14 is determined according to the positive bulging profile; the forming heights of the four corners of the part in the positive bulging profile are consistent; the circumferential profile of the flange surface in the positive bulging profile is consistent with the edge shape of the four sides of the part, and a smooth transition connection is adopted between the part profile and the flange surface in the positive bulging profile.

[0021] A second aspect of the present invention provides a method for controlling the uniform thickness of a hyperbolic deep cavity skin actively bulged, using the hyperbolic deep cavity skin actively bulged uniform thickness control mold as described in any one of the first aspects, the method comprising:

[0022] Step 1, the sheet is placed between the upper mold 11 and the lower mold 14, and after the molds are closed, the cavity of the lower mold 14 is continuously supplemented with high-pressure liquid through the lower mold filling and drainage channel 15, and the air in the cavity of the upper mold 11 is discharged through the upper mold filling and exhaust channel 16. Under the action of the high-pressure liquid, the sheet is gradually attached to the mold surface of the upper mold 11 until it is completely attached;

[0023] Step 2: High-pressure liquid is continuously added to the cavity of the upper mold 11 through the upper mold filling and exhaust channel 16, and the liquid in the cavity of the lower mold 14 is discharged through the lower mold filling and drainage channel 15. Under the action of the high-pressure liquid, the sheet material gradually adheres to the surface of the lower mold 14 until it is completely fitted.

[0024] The present invention provides a uniform wall thickness control die and method for active bulging of a hyperbolic deep cavity skin, which controls the maximum thinning of skin parts: for skin parts with large arch height, during the reverse bulging material storage process, the sheet material at the maximum arch height of the skin parts is first fitted to the upper mold surface due to the effect of liquid pressure during the forming process, and the normal flow of the sheet material is suppressed under the effect of liquid pressure, so that the sheet material in the area corresponding to the maximum arch height of the part is basically not thinned, and the sheet material in the circumferential groove part of the reverse bulging mold surface undergoes plastic thinning deformation. Due to the material storage effect of the upper mold groove structure, the thinning of the sheet material in the maximum arch height area of ​​the skin part becomes smaller during the forward bulging process, and the overall thinning of the part is more uniform, avoiding the orange peel or even cracking phenomenon caused by excessive thinning.

[0025] Low mold manufacturing cost: By constructing a positive bulging surface and a reverse bulging surface, a set of molds can be formed in two steps, which reduces the number of molds and manufacturing costs. At the same time, it reduces tooling change, part turnover and other processes to improve the production efficiency of parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic diagram of a double-curved high-arch skin part;

[0027] Figure 2 It is a schematic diagram of the positive bulging profile;

[0028] Figure 3 It is a schematic diagram of the reverse bulging profile;

[0029] Figure 4 It is a schematic diagram of the forming die structure;

[0030] Description of reference numerals:

[0031] 1 bottom of skin part, 2 four corners of skin part, 3 edge line of skin part, 4 flange surface, 5 calendering rib groove, 6 transition profile, 7 annular reverse groove structure, 8 boss structure, 9 calendering rib convex rib, 10 sealing groove, 11 upper die, 12 sheet material, 13 liquid baffle plate, 14 lower die, 15 lower die filling and drainage channel, 16 upper die filling and exhaust channel. DETAILED DESCRIPTION

[0032] The present application is further described in detail below with reference to examples and drawings:

[0033] like Figure 1-4 As shown, the present invention provides a mold and method for controlling the uniform wall thickness of a hyperbolic deep cavity skin active bulging.

[0034] The present invention provides a double-curvature deep cavity skin active bulging wall thickness uniform control die, comprising: an annular reverse groove structure 7, a boss structure 8, an upper die 11, a lower die 14, a lower die filling and draining channel 15, and an upper die filling and exhausting channel 16;

[0035] An annular reverse groove structure 7 is dug on the upper die 11, and a boss structure 8 is formed at the center of the annular reverse groove structure 7; the cross section of the annular reverse groove structure 7 is an arc;

[0036] The profile of the lower mold 14 is consistent with the profile of the double-curved deep cavity skin;

[0037] The sheet material is arranged between the upper die 11 and the lower die 14;

[0038] The upper mold 11 and the lower mold 14 are respectively provided with an upper mold filling and exhaust channel 16 and a lower mold filling and draining channel 15 for replenishing high-pressure liquid or exhausting air to the cavities of the upper mold 11 and the lower mold 14.

[0039] Optionally, the groove depth h of the annular reverse groove structure 7 is smaller than the profile height H of the lower mold 14 at the corresponding position in the vertical direction.

[0040] Optionally, the area of ​​the boss structure 8 is determined according to the profile structure of the hyperbolic deep cavity skin.

[0041] Optionally, the greater the hyperbolic curvature or the depth of the hyperbolic deep cavity skin, the larger the area of ​​the boss structure 8 .

[0042] Optionally, the height of the boss structure 8 is determined according to the groove depth h of the annular reverse groove structure 7 .

[0043] Optionally, the active bulging wall thickness uniformity control mold for the double-curvature deep cavity skin further includes: a calendering rib groove 5, a calendering rib convex rib 9, and a sealing groove 10;

[0044] The upper die 11 and the lower die 14 are provided with a convex rib 9 and a concave rib 5, respectively;

[0045] The upper die 11 is provided with a sealing groove 10 , which is arranged outside the convex rib 9 of the rolled rib.

[0046] Optionally, the double-curvature deep cavity skin active bulging wall thickness uniform control mold further includes: a liquid baffle 13;

[0047] A liquid baffle 13 is provided at the edge of the upper mold 11 to prevent high-pressure liquid from spraying.

[0048] Optionally, the profile of the lower die 14 is determined according to the positive bulging profile; the forming heights of the four corners of the part in the positive bulging profile are consistent; the circumferential profile of the flange surface in the positive bulging profile is consistent with the edge shape of the four sides of the part, and a smooth transition connection is adopted between the part profile and the flange surface in the positive bulging profile.

[0049] In this embodiment, the length and width of the skin part are about 1800mm, the height of the skin cavity is 450mm, the material thickness is 2.5mm, and 2A12 aluminum alloy is selected. The part has curvature variation characteristics in two directions. The key to this forming method is to construct a positive bulging surface and a reverse bulging surface, and complete the tooling design and manufacturing based on the surface. The specific steps are as follows:

[0050] 1. Construct the positive bulging profile and adjust the forming direction of the part so that the heights of the four corners 4 of the skin part are basically consistent. Construct the flange surface 4, the four-side circumferential profile of the flange surface 4 is consistent with the shape of the edge line 3 of the skin part, and a smooth transition connection is used between the part profile and the flange surface 4 to form a transition profile 6. Construct the calendering groove 5 near the die radius on the flange surface 4.

[0051] 2. Finite element simulation analysis: According to the constructed positive bulging surface, a hydraulic bulging finite element simulation analysis is performed, and the area S of the region with a larger thinning area and a concentrated thinning area is obtained according to the simulation results.

[0052] 3. Construct the reverse bulging pressing surface 4 according to the flange surface 4 of the constructed forward bulging profile, and set the bulging rib 9 at the corresponding position of the forward bulging bulging rib groove 5. Set the annular reverse groove structure 7 around the area S corresponding to the area where the reverse bulging profile and the forward bulging simulation results have a large thinning area and a concentrated thinning area. The groove depth h needs to be less than the corresponding forward bulging profile height H in the vertical direction. The area of ​​the boss structure 8 is basically close to S, and a sealing groove 10 is set on the outside of the bulging rib 9.

[0053] 4. Design of mold structure profile: The mold structure is designed according to the constructed forward bulging profile and reverse bulging profile. The forward bulging profile is used for the structural design of the lower mold 14, and a lower mold filling and drainage channel 15 is set at the bottom of the profile. The reverse bulging profile is used for the structural design of the upper mold 11, and an upper mold filling and exhaust channel 16 is set at the top. A sealing strip is set in the sealing groove 10, and a liquid baffle 13 is set at the edge of the mold.

[0054] 5. Reverse bulging storage, the sheet 12 is placed between the upper mold 11 and the lower mold 14. After the mold is closed, the high-pressure liquid is continuously added to the cavity of the lower mold 14 through the lower mold filling and discharge channel 15, and the air in the upper mold 14 cavity is discharged by the upper mold filling and exhaust channel 16. Under the action of high-pressure liquid, the sheet 12 gradually adheres to the surface of the upper mold 11 until it is completely fitted.

[0055] 6. For the parts formed by the forward bulging, after the reverse bulging storage process is completed, the high-pressure liquid is continuously added to the cavity of the upper mold 11 through the upper mold filling and exhaust channel 16, and the liquid in the cavity of the lower mold 14 is discharged by the lower mold filling and drainage channel 15. Under the action of the high-pressure liquid, the transition part gradually adheres to the surface of the lower mold 14 until it is fully fitted.

Claims

1. A double-curvature deep cavity skin active bulging wall thickness uniform control die, characterized in that: include: An annular reverse groove structure (7), a boss structure (8), an upper mold (11), a lower mold (14), a lower mold filling and draining channel (15), and an upper mold filling and exhausting channel (16); An annular reverse groove structure (7) is excavated on the upper mold (11), and a boss structure (8) is formed at the center of the annular reverse groove structure (7); the cross section of the annular reverse groove structure (7) is arc-shaped; The profile of the lower mold (14) is consistent with the profile of the double-curved deep cavity skin; The sheet material is arranged between an upper die (11) and a lower die (14); The upper mold (11) and the lower mold (14) are respectively provided with an upper mold filling and exhaust channel (16) and a lower mold filling and exhaust channel (15) for replenishing high-pressure liquid or exhausting air to the upper mold (11) and the lower mold (14) cavities.

2. The active bulging wall thickness uniformity control mold for double-curvature deep cavity skin according to claim 1 is characterized in that: The groove depth h of the annular reverse groove structure (7) is less than the profile height H of the lower mold (14) at the corresponding position in the vertical direction.

3. The active bulging wall thickness uniformity control mold for double-curvature deep cavity skin according to claim 1 is characterized in that: The area of ​​the boss structure (8) is determined according to the profile structure of the double-curvature deep cavity skin.

4. The active bulging wall thickness uniformity control mold for double-curvature deep cavity skin according to claim 1 is characterized in that: The greater the hyperbolic curvature or depth of the hyperbolic deep cavity skin, the larger the area of ​​the boss structure (8).

5. The active bulging wall thickness uniformity control mold for double-curvature deep cavity skin according to claim 2 is characterized in that: The height of the boss structure (8) is determined according to the groove depth h of the annular reverse groove structure (7).

6. The active bulging wall thickness uniformity control mold for double-curvature deep cavity skin according to claim 1 is characterized in that: Also includes: Rolled rib groove (5), rolled rib convex rib (9), and sealing groove (10); The upper die (11) and the lower die (14) are respectively provided with a convex rib (9) and a concave rib (5); A sealing groove (10) is provided on the upper die (11), and the sealing groove (10) is arranged on the outer side of the convex rib (9) of the rolled rib.

7. The active bulging wall thickness uniformity control mold for double-curvature deep cavity skin according to claim 1 is characterized in that: Also includes: Liquid baffle (13); A liquid baffle (13) is provided on the edge of the upper mold (11) to prevent high-pressure liquid from spraying.

8. The active bulging wall thickness uniformity control die for double-curvature deep cavity skin according to claim 1, characterized in that: The profile of the lower die (14) is determined according to the positive bulging profile; the forming heights of the four corners of the part in the positive bulging profile are consistent; the peripheral profile of the flange surface in the positive bulging profile is consistent with the edge shapes of the four sides of the part, and a smooth transition connection is adopted between the part profile and the flange surface in the positive bulging profile.

9. A method for controlling the uniform wall thickness of a double-curvature deep cavity skin active bulging, characterized in that: Using the double-curvature deep cavity skin active bulging wall thickness uniform control mold according to any one of claims 1 to 8, the method comprises: Step 1, placing the sheet material between the upper mold (11) and the lower mold (14), and after the molds are closed, high-pressure liquid is continuously added to the cavity of the lower mold (14) through the lower mold filling and drainage channel (15), and the air in the mold cavity of the upper mold (11) is discharged through the upper mold filling and exhaust channel (16). Under the action of the high-pressure liquid, the sheet material gradually adheres to the mold surface of the upper mold (11) until it is completely adhered; Step 2: High-pressure liquid is continuously added to the cavity of the upper mold (11) through the upper mold filling and exhaust channel (16), and the liquid in the cavity of the lower mold (14) is discharged through the lower mold filling and exhaust channel (15). Under the action of the high-pressure liquid, the sheet material gradually adheres to the surface of the lower mold (14) until it is completely fitted.

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