A method for forming cylindrical parts with small curvature radius

Abstract

The present invention discloses a method and system for forming cylindrical parts with small curvature fillet radii, belonging to the technical field of sheet metal forming. The shape and size of the pre-forming die are determined based on the shape and size of the cylindrical part. Pressure is applied to the pre-formed sheet in stages or simultaneously through a combined forming rubber body, promoting the sheet to flow toward the fillet during the forming process, thereby achieving the forming of a small curvature fillet radius. The present invention is simple to operate and can effectively improve the forming quality of small curvature fillets. The workpiece wall thickness reduction rate is low, and stress distribution is uniform. During the forming process, the rebound deformation of the part can be suppressed, resulting in low rebound and a more precise configuration.

Description

Technical Field

[0001] The invention belongs to the technical field of plate forming, and in particular relates to a method for forming a cylindrical part with a small curvature radius. Background Art

[0002] As manufacturing demands for lightweight, high-strength, and precision forming continue to increase, a large number of lightweight alloy shell components are being designed with geometric features such as thin walls, heterogeneous structures, and small corners to meet the performance requirements of equipment in the aerospace and automotive industries. During the forming process of thin-walled shell components, the material's low plasticity leads to significant localized stress concentration in the parts, especially at small curvature corners. This can cause excessive thinning and cracking in localized areas, leading to part failure during the forming process.

[0003] In the traditional rigid die deep drawing process, there are overhanging areas, which are prone to severe wall thinning in some areas. Stress concentration occurs at the corners of the formed parts, causing the parts to break. In addition, the rigid die deep drawing process will produce large residual stress and deformation, requiring subsequent annealing and heat treatment processes, thereby increasing production costs and process difficulty.

[0004] Compared to traditional steel die drawing, soft die drawing eliminates overhangs, offers superior filling performance, produces superior surface quality, minimizes wall thinning, and provides more uniform local stress distribution. However, in traditional hydraulic drawing or polyurethane rubber soft die drawing, small radius corners can still crack due to insufficient material flow, creating an urgent need for new methods for deep drawing of small radius corners. Summary of the Invention

[0005] In order to solve the defects existing in the above-mentioned prior art, the purpose of the present invention is to provide a method for forming cylindrical parts with a small curvature radius, which effectively improves the forming quality of small curvature fillets, has a low wall thickness thinning rate of the workpiece, and has a uniform stress distribution; the rebound deformation of the parts can be suppressed during the forming process, the rebound is small, and the configuration is more precise.

[0006] The present invention is achieved through the following technical solutions:

[0007] A method for forming a cylindrical part with a small curvature radius, comprising:

[0008] S1: The blank is mounted on the preforming die, and the medium chamber is mounted above the blank; the forming chamber formed between the medium chamber and the blank is filled with forming medium; the preforming punch is mounted on the medium chamber; the shoulder angle and bottom angle of the preforming die cavity are both rounded, the side wall of the cavity is a first arc surface arched toward the cavity, and the bottom of the cavity is a second arc surface arched toward the cavity;

[0009] S2: A downward force is applied to the medium chamber to clamp the blank. The preforming punch moves downward and squeezes the forming medium. Pressure is generated in the forming chamber. The forming medium applies pressure to the blank to deform it and fit it into the preforming concave mold cavity.

[0010] S3: The preforming punch stops descending, the medium compartment is removed, the preforming punch is removed, and the preformed workpiece is taken out;

[0011] S4: Mounting the preformed workpiece on the forming die, and mounting the medium chamber above the preformed workpiece; sleeve the annular first forming rubber over the cylindrical second forming rubber to form a combined forming rubber body, wherein the bottom of the second forming rubber is a convex arc surface and is filled into the forming chamber formed by the medium chamber and the preformed workpiece; the shoulder angle and bottom angle of the forming die cavity are both rounded;

[0012] S5: applying a downward force to the medium chamber to clamp the preformed workpiece, and the forming punch moves downward to fit with the combined forming rubber body; the lower end of the forming punch is a boss structure;

[0013] S6: The forming punch continues to move downward, the first forming rubber generates pressure on the side wall of the preformed workpiece, and the side wall of the preformed workpiece is fitted to the side wall of the forming concave mold cavity; the forming punch continues to move downward, the second forming rubber contacts the bottom of the preformed workpiece, the second forming rubber generates pressure on the bottom of the preformed workpiece, and the bottom of the preformed workpiece is fitted to the bottom of the forming concave mold cavity; the forming punch continues to move downward, the second forming rubber is squeezed, and the bottom of the preformed workpiece is fitted to the bottom of the forming concave mold cavity, the radially expanded portion of the second forming rubber squeezes the first forming rubber, and at the same time, the first forming rubber is squeezed downward by the forming punch, and the preformed workpiece is fitted to the rounded corner of the bottom of the forming concave mold cavity;

[0014] S7: Remove the medium bin, remove the forming punch, remove the combined forming rubber body, and take out the formed workpiece.

[0015] Preferably, the radius of the forming concave mold cavity is R, the depth is H, the bottom corner radius of the cavity is r1, and the shoulder corner radius of the cavity is r2; the radius of the pre-forming concave mold cavity is r, the depth is h, The bottom corner radius of the preformed concave mold cavity is r1 ′ , the shoulder radius is r2 ′ , The first arc radius of the preforming die is r3, and the second arc radius is r4.

[0016] Preferably, the inner surface area of the pre-forming female mold cavity is equal to that of the forming female mold.

[0017] Preferably, the shaping medium is water, oil or a viscous medium.

[0018] Preferably, in S2, the speed at which the preforming punch descends is 0.1 to 0.5 mm / s; and in S5, the speed at which the forming punch descends is 0.1 to 0.5 mm / s.

[0019] Preferably, the outer diameter of the first molded rubber is equal to the inner diameter of the medium chamber, and the outer diameter d of the second molded rubber is equal to the inner diameter of the first molded rubber.

[0020] Further preferably, the radius of the pre-formed concave mold cavity is r, the outer diameter of the second forming rubber is d,

[0021] Preferably, the second molded rubber has a harder hardness than the first molded rubber.

[0022] More preferably, the Shore hardness of the first molded rubber is in the range of 20-25A, and the Shore hardness of the second molded rubber is in the range of 45-50A.

[0023] Preferably, the height of the first forming rubber is equal to that of the second forming rubber, and the height of the convex arc surface at the bottom of the second forming rubber is equal to h is the depth of the pre-formed concave mold cavity; the diameter of the boss at the lower end of the forming punch is equal to the inner diameter of the second forming rubber, and the height of the boss is equal to the height of the convex surface of the second forming rubber.

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

[0025] The method for forming cylindrical parts with small curvature and fillet radius disclosed in the present invention effectively improves the quality of small fillet forming by utilizing reasonable preforming and combined forming rubber bodies. Compared with traditional steel die drawing, the method for forming cylindrical parts with small curvature and fillet radius disclosed in the present invention preforms the blank through soft die drawing, and the blank is pre-accumulated in the transverse and longitudinal directions, forming a larger fillet at the corner position, with a low wall thickness thinning rate and uniform stress distribution. The combined forming rubber body is used to regulate the deformation sequence of the sheet material, which can effectively promote material flow. The combined forming rubber body is used as a pressure medium during the forming process. The soft rubber at the edge first contacts the side wall of the workpiece, and the accumulated material flows longitudinally. The hard rubber at the center contacts the bottom of the workpiece, causing the material at the bottom of the workpiece to flow from the center to the edge. The lateral expansion of the rubber at the center deforms the rubber at the edge, promoting the workpiece material to fit the fillet, and the formed parts are fully formed at the fillet. During the processing, the workpiece has little rebound and precise configuration. By combining the rubber to contact the pre-formed workpiece successively or simultaneously, the workpiece can obtain good material flow in the axial and radial directions, solving the current problem of insufficient rounded corner forming in deep drawing. At the same time, due to the elasticity of the rubber soft mold itself after forming, it can suppress the rebound deformation of the part, resulting in small rebound and more precise configuration.

[0026] Furthermore, the size range of the pre-forming die can make the pre-formed workpiece accumulate material in the horizontal and vertical directions, making it easier for the material to flow to the rounded corners during final forming, and can ensure that the blank can be fully unfolded without wrinkles during final forming.

[0027] Furthermore, the inner surface area of the pre-formed concave mold cavity is equal to that of the forming concave mold, which can ensure that the accumulated material portion of the pre-formed workpiece fits the concave mold during final forming without wrinkles or cracks, and the wall thickness distribution is more uniform.

[0028] Furthermore, the forming medium is water, oil or a viscous medium, which has better fluidity and is more suitable for forming more complex preformed structures.

[0029] Furthermore, the moving speed of the punch in the preforming and final forming is 0.1 to 0.5 mm / s, which provides a suitable forming rate range for the preforming and final forming of the blank and avoids surface defects of the formed parts.

[0030] Furthermore, the outer diameter of the first molded rubber is equal to the inner diameter of the medium bin, and the outer diameter d of the second molded rubber is equal to the inner diameter of the first molded rubber. At the same time, the value range of the outer diameter of the second molded rubber can enable the edge portion of the rubber to contact the side wall of the preformed workpiece first, thereby promoting the flow of the side wall accumulated material.

[0031] Furthermore, the hardness of the second forming rubber is greater than that of the first forming rubber, and the selection of the hardness range of the two can enable the central portion rubber to assist the edge portion rubber in deformation, thereby promoting the flow of material toward the fillet.

[0032] Furthermore, the height of the forming punch boss is equal to the height of the convex camber of the second forming rubber, and the height range of the convex camber of the bottom of the second forming rubber is such that the top of the second forming rubber contacts the center of the preformed workpiece. As the central part of the rubber is continuously pressurized, the material at the bottom of the preformed workpiece gradually flows from the center to the edge. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a main sectional view of the overall structure of the pre-formed mold assembly of the present invention;

[0034] Figure 2 This is a main cross-sectional view of the overall structure of the present invention when preforming is completed;

[0035] Figure 3 This is a main sectional view of the overall structure of the mold before final forming of the present invention;

[0036] Figure 4 This is a cross-sectional view of the overall structure when the male mold is attached to the composite rubber during the final forming process of the present invention;

[0037] Figure 5It is a cross-sectional view of the overall structure of the side wall of the rubber forming workpiece at the edge portion during the final forming process of the present invention;

[0038] Figure 6 It is a cross-sectional view of the overall structure when the rubber forming workpiece is assembled during the final forming process of the present invention;

[0039] Figure 7 This is a schematic diagram of the overall structure of the present invention when it is finally formed;

[0040] Figure 8 This is a diagram of the shape and size of the pre-forming die and the final forming die of the present invention.

[0041] In the figure: 1 is a pre-forming convex die, 2 is a medium bin, 3 is a forming medium, 4 is a pre-forming concave die, 5 is a forming convex die, 6 is a first forming rubber, 7 is a second forming rubber, and 8 is a forming concave die. DETAILED DESCRIPTION

[0042] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, which are intended to explain the present invention rather than to limit it.

[0043] The method for forming a cylindrical part with a small curvature radius of the present invention comprises the following steps:

[0044] S1: The blank is mounted on the preforming die 4, and the medium chamber 2 is mounted above the blank; the forming chamber formed between the medium chamber 2 and the blank is filled with the forming medium 3; the preforming punch 1 is mounted on the upper portion of the medium chamber; the shoulder angle and bottom angle of the cavity of the preforming die 4 are both rounded, the side wall of the cavity is a first arc surface arched toward the cavity, and the bottom of the cavity is a second arc surface arched toward the cavity;

[0045] S2: A downward force is applied to the medium chamber 2 to clamp the blank. The preforming punch 1 moves downward and squeezes the forming medium 3. Pressure is formed in the forming chamber. The forming medium 3 applies pressure to the blank, causing it to deform and fit into the cavity of the preforming die 4.

[0046] S3: The preforming punch 1 stops descending, the medium bin 2 is removed, the preforming punch 1 is removed, and the preformed workpiece is taken out;

[0047] S4: The preformed workpiece is mounted on the forming die 8, and the medium chamber 2 is mounted above the preformed workpiece; the annular first forming rubber 6 is sleeved onto the cylindrical second forming rubber 7 to form a combined forming rubber body, the bottom of the second forming rubber 7 being a convex arc surface and being filled into the forming chamber formed by the medium chamber 2 and the preformed workpiece; the shoulder angle and bottom angle of the cavity of the forming die 8 are both rounded;

[0048] S5: Applying downward force to the medium chamber 2 to clamp the preformed workpiece, the forming punch 5 moves downward to fit the combined forming rubber body; the lower end of the forming punch 5 is a boss structure;

[0049] S6: the forming punch 5 continues to move downward, the first forming rubber 6 generates pressure on the side wall of the preformed workpiece, and the side wall of the preformed workpiece is fitted to the side wall of the cavity of the forming die 8; the forming punch 5 continues to move downward, the second forming rubber 7 contacts the bottom of the preformed workpiece, the second forming rubber 7 generates pressure on the bottom of the preformed workpiece, and the bottom of the preformed workpiece is fitted to the bottom of the cavity of the forming die 8; the forming punch 5 continues to move downward, the second forming rubber 7 is squeezed, and the bottom of the preformed workpiece is fitted to the bottom of the cavity of the forming die 8. The radially expanded part of the second forming rubber 7 squeezes the first forming rubber 6. At the same time, the first forming rubber 6 is squeezed downward by the forming punch 5, and the preformed workpiece is fitted to the fillet of the bottom cavity of the forming die 8;

[0050] S7: Remove the medium bin 2, remove the forming punch 5, remove the combined forming rubber body, and take out the formed workpiece.

[0051] In a preferred embodiment of the present invention, the radius of the forming die 8 cavity is R, the depth is H, the bottom corner radius of the cavity is r1, and the shoulder corner radius of the cavity is r2; the radius of the preforming die 4 cavity is r, the depth is h, The bottom corner radius of the pre-forming die 4 cavity is r1 ′ , the shoulder radius is r2 ′ , The first arc radius of the preforming die 4 is r3, and the second arc radius is r4.

[0052] In a preferred embodiment of the present invention, the inner surface area of the cavity of the preforming die 4 is equal to that of the forming die 8 .

[0053] In a preferred embodiment of the present invention, the shaping medium 3 is water, oil or a viscous medium.

[0054] In a preferred embodiment of the present invention, in S2, the speed at which the preforming punch 1 descends is 0.1 to 0.5 mm / s; in S5, the speed at which the forming punch 8 descends is 0.1 to 0.5 mm / s.

[0055] In a preferred embodiment of the present invention, the outer diameter of the first forming rubber 6 is equal to the inner diameter of the medium chamber 2, and the outer diameter d of the second forming rubber 7 is equal to the inner diameter of the first forming rubber 6. Preferably, the radius of the cavity of the pre-forming die 4 is r, the outer diameter of the second forming rubber 7 is d,

[0056] In a preferred embodiment of the present invention, the hardness of the second molded rubber 7 is greater than that of the first molded rubber 6 .

[0057] In a preferred embodiment of the present invention, the Shore hardness of the first molded rubber 6 is in the range of 20-25A, and the Shore hardness of the second molded rubber 7 is in the range of 45-50A.

[0058] In a preferred embodiment of the present invention, the heights of the first molded rubber 6 and the second molded rubber 7 are equal, and the height of the convex curved surface at the bottom of the second molded rubber 7 is equal to h is the depth of the pre-forming die cavity 4; the boss diameter at the lower end of the forming punch 5 is equal to the inner diameter of the second forming rubber 7, and the boss height is equal to the height of the second forming rubber 7 convex arc surface.

[0059] The present invention will be further described below with a specific example:

[0060] like Figure 8 First, determine the shape and size of the forming die 8 according to the size of the cylindrical part. The cavity radius of the forming die 8 is R, the depth is H, the bottom fillet radius is r1, and the shoulder fillet radius is r2, where R = 10mm, H = 4mm, r1 = 0.2mm, and r2 = 0.4mm;

[0061] The shape and size of the preforming die 4 are determined according to the shape and size of the forming die 8. The cavity radius of the preforming die 4 is r, the depth is h, and the bottom fillet radius is r1 ′ , the shoulder fillet radius is r2 ′ The radius of the second arc surface at the bottom is r3, and the radius of the first arc surface on the side wall is r4.

[0062] Preferably, Take r = 7mm, h = 2.8mm, r1 ′ =0.45mm, r2 ′ =0.9mm, r3=11.2mm, r4=4.5mm, so that the blank is accumulated in the appropriate range in the horizontal and vertical directions.

[0063] like Figure 1 , install the blank on the preforming die 4, install the medium bin 2 on the blank, apply downward force to the medium bin 2 to clamp the blank, fill the medium bin with hydraulic oil, install the preforming punch 1 on the upper part of the medium bin 2, and the preforming punch 1 descends at a certain speed.

[0064] like Figure 2 When the blank is completely fitted with the preforming die 4, the preforming punch 1 stops descending, the preforming punch 1 is removed, the medium bin 2 is removed, and the preformed workpiece is taken out.

[0065] like Figure 3, install the preformed workpiece on the forming die 8, install the medium bin 2 on the preformed workpiece, fill the first forming rubber 6 and the second forming rubber 7 into the medium bin 2, and install the forming punch 5 on the upper part of the medium bin 2. The medium bin 2 applies a downward force to clamp the blank, and the forming punch 5 descends at a speed of 0.5 mm / s.

[0066] The outer diameter of the first forming rubber 6 is the inner diameter of the medium chamber 2, the outer diameter of the second forming rubber 7 is the inner diameter of the first forming rubber 6, the forming punch 5 has a boss, and the boss height is the height h1 of the second forming rubber arc surface convex. Take h1 = 0.85 mm, and the boss diameter is the diameter d of the second molding rubber 7.

[0067] like Figure 4 , the forming punch 5 moves downward to fit the combined rubber.

[0068] Preferably, Taking d=9.8 mm, the first forming rubber 6 is first in contact with the preformed workpiece, promoting the preformed workpiece to fit into the cavity in the longitudinal direction.

[0069] like Figure 5 The first forming rubber 6 first contacts the preformed workpiece, and the preformed workpiece accumulates longitudinally and fits into the cavity.

[0070] Preferably, the hardness of the first forming rubber 6 is less than that of the second forming rubber 7. The Shore hardness of the first forming rubber 6 is 22A, and the Shore hardness of the second forming rubber 7 is 47A. This allows the second forming rubber 7 to promote radial flow of the material at the bottom of the preformed workpiece. When the second forming rubber 7 is compressed, the radially expanded portion deforms the first forming rubber 6, promoting the flow of the preformed workpiece material toward the fillet.

[0071] like Figure 6 The second forming rubber 7 presses down the bottom of the preformed workpiece, and the material at the bottom of the preformed workpiece flows from the center to the surrounding area, gradually fitting the bottom of the cavity. Under the action of the first forming rubber 6, the side wall of the preformed workpiece is about to fit the side wall of the cavity.

[0072] like Figure 7 The second forming rubber 7 presses down the bottom of the preformed workpiece, and the bottom of the preformed workpiece completely fits the cavity. The radial expansion part of the second forming rubber 7 under pressure deforms the first forming rubber 6, and the side wall of the preformed workpiece completely fits the side wall of the cavity. The material of the preformed workpiece flows to the fillet, and the corner of the preformed workpiece fits the fillet.

[0073] Remove the forming punch 5, remove the medium bin 2, remove the combined rubber, and take out the formed cylindrical part.

[0074] It should be noted that the above is only part of the embodiments of the present invention. Equivalent changes made to the system described in the present invention are all included in the scope of protection of the present invention. Those skilled in the art of the present invention may make similar substitutions for the specific examples described, as long as they do not deviate from the structure of the present invention or exceed the scope defined by the claims, and all such substitutions are within the scope of protection of the present invention.

Claims

1. A method for forming a cylindrical part with a small curvature radius, characterized in that: include: S1: The blank is mounted on the preforming die (4), and the medium bin (2) is mounted above the blank; the forming medium (3) is filled into the forming chamber formed between the medium bin (2) and the blank; the preforming punch (1) is mounted on the upper part of the medium bin; the shoulder angle and the bottom angle of the cavity of the preforming die (4) are both rounded, the side wall of the cavity is a first arc surface arched toward the cavity, and the bottom of the cavity is a second arc surface arched toward the cavity; S2: A downward force is applied to the medium chamber (2) to clamp the blank, and the preforming punch (1) moves downward while squeezing the forming medium (3), thereby forming pressure in the forming chamber. The forming medium (3) applies pressure to the blank to deform the blank and fit it into the cavity of the preforming die (4); S3: the preforming punch (1) stops descending, the medium bin (2) is removed, the preforming punch (1) is taken out, and the preformed workpiece is taken out; S4: The preformed workpiece is mounted on the forming die (8), and the medium chamber (2) is mounted above the preformed workpiece; the annular first forming rubber (6) is sleeved on the outside of the cylindrical second forming rubber (7) to form a combined forming rubber body, the bottom of the second forming rubber (7) is a convex arc surface, and is filled into the forming chamber formed by the medium chamber (2) and the preformed workpiece; the shoulder angle and bottom angle of the forming die (8) cavity are both rounded; S5: applying downward force to the medium chamber (2) to clamp the preformed workpiece, and the forming convex die (5) moves downward to fit with the combined forming rubber body; the lower end of the forming convex die (5) is a boss structure; S6: the forming punch (5) continues to move downward, the first forming rubber (6) generates pressure on the side wall of the preformed workpiece, and the side wall of the preformed workpiece fits against the side wall of the forming cavity of the forming die (8); the forming punch (5) continues to move downward, the second forming rubber (7) contacts the bottom of the preformed workpiece, the second forming rubber (7) generates pressure on the bottom of the preformed workpiece, and the bottom of the preformed workpiece fits against the bottom of the forming cavity of the forming die (8); the forming punch (5) continues to move downward, the second forming rubber (7) is squeezed, and the bottom of the preformed workpiece fits against the bottom of the forming cavity of the forming die (8), the radially expanded part of the second forming rubber (7) squeezes the first forming rubber (6), and at the same time, the first forming rubber (6) is squeezed downward by the forming punch (5), and the preformed workpiece fits against the fillet of the bottom of the forming cavity of the forming die (8); S7: Remove the medium bin (2), remove the forming punch (5), remove the combined forming rubber body, and take out the formed workpiece.

2. The method for forming a cylindrical part with a small curvature radius according to claim 1, wherein: The radius of the forming die (8) cavity is R, the depth is H, the bottom corner radius of the cavity is r1, and the shoulder corner radius of the cavity is r2; the radius of the preforming die (4) cavity is r, the depth is h, The bottom corner radius of the preforming die (4) cavity is r1 ′ , the shoulder radius is r2 ′ , The first arc surface radius of the preforming die (4) is r3, and the second arc surface radius is r4.

3. The method for forming a cylindrical part with a small curvature radius according to claim 1, wherein: The inner surface area of the cavity of the preforming die (4) is equal to that of the forming die (8).

4. The method for forming a cylindrical part with a small curvature radius according to claim 1, wherein: The forming medium (3) is water, oil or a viscous medium.

5. The method for forming a cylindrical part with a small curvature radius according to claim 1, wherein: In S2, the speed at which the preforming punch (1) moves downward is 0.1 to 0.5 mm / s; and in S5, the speed at which the forming punch (5) moves downward is 0.1 to 0.5 mm / s.

6. The method for forming a cylindrical part with a small curvature radius according to claim 1, wherein: The outer diameter of the first molded rubber (6) is equal to the inner diameter of the medium chamber (2), and the outer diameter d of the second molded rubber (7) is equal to the inner diameter of the first molded rubber (6).

7. The method for forming a cylindrical part with a small curvature radius according to claim 6, wherein: The radius of the pre-forming die (4) cavity is r, and the outer diameter of the second forming rubber (7) is d.

8. The method for forming a cylindrical part with a small curvature radius according to claim 1, wherein: The second molding rubber (7) has a harder hardness than the first molding rubber (6).

9. The method for forming a cylindrical part with a small curvature radius according to claim 8, wherein: The Shore hardness of the first molded rubber (6) is in the range of 20 to 25A, and the Shore hardness of the second molded rubber (7) is in the range of 45 to 50A.

10. The method for forming a cylindrical part with a small curvature radius according to claim 1, wherein: The height of the first forming rubber (6) is equal to that of the second forming rubber (7), and the height of the raised arc surface at the bottom of the second forming rubber (7) is equal to that of the first forming rubber (6) and the second forming rubber (7). h is the depth of the cavity of the preforming die (4); the diameter of the boss at the lower end of the forming punch (5) is equal to the inner diameter of the second forming rubber (7), and the height of the boss is equal to the height of the convex surface of the second forming rubber (7).

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