A hollow rivet near-net cold extrusion forming die

Abstract

This invention discloses a near-net-shape cold extrusion forming die for hollow rivets. Based on the structure of hollow rivets, an equal weight conversion algorithm is used to construct and unfold the blank ring. The extrusion male and female die tooling structures required for cold extrusion forming are designed. Formulas are established to quantitatively design the structure of each part of the forming surface of the male and female rivets. By limiting the height of the male die and adjusting the die closing gap, the thickness of the part flange is precisely controlled. By controlling the gap between the male die extrusion ejector and the female die ejector slot, phenomena such as flash caused by the blank flowing along the gap between the male and female rivets are prevented, achieving net-size forming, reducing the scrap rate in the production process, and improving the production efficiency of hollow rivets.

Description

Technical Field

[0001] This invention relates to sheet metal rivet parts extrusion forming technology in the field of aircraft manufacturing, specifically a near-net-shape cold extrusion forming die for hollow rivets. Background Technology

[0002] Rivets are widely used in a wide range of fields, from aerospace and sporting goods to automotive machine tools and office supplies. There are many types of rivets, the most common being: R-type, tree-shaped, hollow, solid, semi-hollow, driven, and blind rivets. Rivets can be used as connectors, protective parts, and decorative parts. Hollow rivets are used between holes in parts made of both metallic and non-metallic materials. They are developed from semi-hollow rivets by countersunk holes all the way to the head. Due to their light weight and weak head, they are used for riveting non-metallic materials with relatively low loads. Hollow rivets have a wide range of applications, including civilian industries such as clothing and footwear, as well as military fields such as naval artillery and aerospace.

[0003] As is well known, traditional hollow rivets are generally formed from thin sheets of pure aluminum, brass, or copper. Taking pure aluminum as an example, it has the characteristics of being strong, having low density, being easy to process, and having low density. The traditional method of processing hollow rivets involves using tubing of a certain specification through a corresponding flaring forming process. Due to the small size of hollow rivets, the size of the tubing blank during flaring is also relatively small, making clamping inconvenient and the blank prone to instability. The resulting parts have a large thinning of the flange and shank corner radius and are prone to cracking, resulting in unstable processing quality. Currently, patent CN115958079A proposes a cold extrusion forming die for short hollow rivets, which initially solves the extrusion forming tooling structure for standard short hollow rivets. However, this tooling structure is only suitable for hollow rivets with simple shapes, a maximum outer diameter of no more than 12mm, and a height of no more than 10mm. It lacks universal applicability for hollow rivets with complex shapes, flanges, or a height greater than 10mm. Furthermore, due to the lack of limitation on the height of the male die's extrusion section, the degree of die closing cannot be controlled after the male and female dies are closed, requiring manual adjustment of the die gap. This results in parts flanges that are either too thin or too thick. Additionally, the lack of coordination between the male and female dies, with the male die ejector pin manufactured using negative tolerances and the female die groove using positive tolerances, causes the center of the hollow rivet flange to shift during extrusion. This leads to flash and other phenomena such as the blank flowing along the gap between the male and female dies, making it impossible to achieve net dimensional forming and resulting in a large amount of scrap. Therefore, there is an urgent need for a near-net-shape cold extrusion forming die suitable for various types of large-sized, complex-structured hollow rivets. Summary of the Invention

[0004] This invention provides a near-net-shape cold extrusion forming die for hollow rivets, which is suitable for near-net-shape cold extrusion forming of various types of large-sized and complex-structured hollow rivets.

[0005] This invention provides a near-net-shape cold extrusion forming die for hollow rivets, comprising: an extrusion male die 5 and an extrusion female die 6;

[0006] The extrusion die 5 includes: a die body and a die base 10; the die body is fixed on the die base 10 and is an integral structure, which includes, from bottom to top: a die shape 7, an extrusion ejector rod 8, and a reinforcing cone 9;

[0007] The length of the extrusion rod 8 is greater than the length of the hollow rivet 1, and the forming surface of the extrusion rod 8 is greater than the outer contour dimension of the unfolded blank 2. The unfolded blank 2 is annular, with an inner diameter equal to the diameter of the inner shaft 3 of the hollow rivet, an outer diameter equal to the diameter of the flange face 4 of the hollow rivet, and the weight of the unfolded blank 2 is the same as the weight of the hollow rivet.

[0008] The male mold body 7 includes: a male mold body transition radius 25, a male mold body cylindrical segment 24, and a guide 11; the length of the male mold body cylindrical segment 24 is η+δ, the diameter of the male mold body cylindrical segment 24 matches the inner shaft surface 3 of the hollow rivet, and η is the thickness of the unfolded blank; the value of the male mold body transition radius 25 between the male mold body cylindrical segment 24 and the extrusion ejector 8 is R+δ, where R is the transition radius dimension between the hollow rivet flange surface 4 and the hollow rivet shank, and δ is the thickness of the hollow rivet part; the guide 11 is rounded at the contact surface between the male mold body cylindrical segment 24 and the unfolded blank 2, and the rounding radius is equal to the diameter of the cylindrical segment 24 of the male mold body;

[0009] The extrusion die 6 includes: a die body 12 and a die base 14, wherein the die body 12 is fixed on the die base 14;

[0010] The female mold body 12 has a trapezoidal structure with a conical outer contour and a central slot. The slot includes a forming slot 15 and an ejector slot 16. The forming slot 15 matches the outer surface of the hollow rivet 1 rod. The unfolded blank 2 is placed in the ejector slot 16. The ejector slot 16 matches the diameter of the extrusion ejector 8 and adopts a zero-clearance fit. The depth of the ejector slot 16 is H = δ + h, where h is the dimension from the lower surface of the male mold base 10 to the forming surface 18 of the extrusion ejector.

[0011] Optionally, the reinforcing cone 9 and the extrusion rod 8 are connected by a platform transition, and the reinforcing cone 9 and the extrusion rod 8 maintain an opening angle of 45-60 degrees.

[0012] Optionally, a positioning groove 19 is provided at the upper end of the top rod groove 16. The diameter of the positioning groove 19 is 1.2 times the outer contour diameter of the unfolded blank 2, and the connecting boss of the reinforcing cone 9 and the extrusion top rod 8 is fitted with the positioning groove 19 without clearance.

[0013] Optionally, the lower end of the forming groove 15 is opened through the female mold body 12 to form a trumpet-shaped groove 20, and the wall of the trumpet-shaped groove 20 is deviated from the vertical direction by 2 degrees.

[0014] The total length of the forming groove 15 must be 3 / 4 of the height of the hollow rivet 1 rod.

[0015] Optionally, the female mold base 14 is slotted and connected to the lower end of the groove of the female mold body 12 for installing the rubber bladder automatic unloading device 21;

[0016] The automatic unloading device 21 for rubber bladders includes a top plate 22 and a rubber bladder sphere 23. The top plate 22 is positioned above the rubber bladder sphere 23. The rubber bladder sphere 23 is a sphere in its free state. After the extrusion male mold 5 and the extrusion female mold 6 are closed, the blank 2 is expanded and deformed, causing the top plate 22 to be subjected to force and move downward. The rubber bladder sphere 23 contracts. After the extrusion male mold 5 and the extrusion female mold 6 are separated, the rubber bladder sphere 23 rebounds, and the top plate 22 ejects the hollow rivet from the female mold.

[0017] Optionally, the male mold base 10 adopts a platform structure, and the platform is slotted and connected to the reinforcing cone 9.

[0018] Optionally, the diameter D of the forming surface 18 of the extrusion push rod is (1.05~1.15)×d;

[0019] Where d is the diameter of the hollow rivet flange face 4.

[0020] Optionally, the extrusion die 6 may also include: a pressure ring 13;

[0021] The pressure ring 13 is a cuboid structure with a tapered hole that fits the shape of the female mold body 12. The female mold base 14 is a platform structure with a slot and is connected and fixed to the pressure ring 13 by screws 17.

[0022] The beneficial effects of this application are as follows:

[0023] 1) This invention provides a near-net-shape cold extrusion forming die for hollow rivets. By designing a cold extrusion forming die with a widely applicable structure, it solves the problems of blank instability, large thinning of the flange and rod corner radius and easy cracking during traditional hollow rivet flaring forming. It also solves the problem that traditional extrusion forming dies are only suitable for standard short rod hollow rivets, thus expanding the application range of the die and having important practical value.

[0024] 2) This invention provides an equal weight conversion method for calculating the unfolded blank of a hollow rivet. By designing an annular unfolded blank, with the inner diameter of the annular hole being equal to the inner shaft diameter of the hollow rivet and the outer diameter being slightly smaller than the flange diameter, and adjusting the blank thickness to make the blank weight consistent with the weight of the hollow rivet, the material deformation of the raw material during the plastic flow of the sheet during the extrusion forming process is accurately calculated, so as to achieve the purpose of net size forming and reduce the amount of trimming after forming.

[0025] 3) This invention provides a method for restricting the flow of plastic deformation of blank during the extrusion forming of hollow rivets. By limiting the height of the male mold and adjusting the mold closing gap, the thickness of the part flange can be precisely controlled. By using the gap between the male mold extrusion ejector and the female mold ejector slot, the blank is prevented from flowing along the gap between the male and female molds and generating flash, thus achieving net size forming, reducing the scrap rate in the production process, and reducing the amount of manual finishing work.

[0026] 4) This invention provides an automatic unloading method for hollow rivets after extrusion forming, which solves the problem of traditional manual unloading or manual unloading using a die handle, which requires manual operation and involves a large workload, reduces working hours in the production process, and improves production efficiency. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of a hollow rivet part;

[0028] Figure 2 This is a schematic diagram of the outline of a hollow rivet unfolded into a blank.

[0029] Figure 3 This is a schematic diagram of an extrusion molding die structure;

[0030] Figure 4 This is a schematic diagram of the extrusion male die structure;

[0031] Figure 5 This is a schematic diagram of the extrusion die structure;

[0032] Figure 6 This is a schematic diagram of the automatic unloading device.

[0033] Explanation of the numbering in the diagram:

[0034] 1 Hollow rivet, 2 Unfolded blank, 3 Hollow rivet inner shaft, 4 Hollow rivet flange face, 5 Extrusion male die, 6 Extrusion female die, 7 Male die shape, 8 Extrusion ejector pin, 9 Reinforcing cone, 10 Male die base, 11 Guide, 12 Female die shape, 13 Pressure ring, 14 Female die base, 15 Forming groove, 16 Ejector pin groove, 17 Screw, 18 Extrusion ejector pin forming surface, 19 Positioning groove, 20 Horn-shaped groove, 21 Rubber bladder automatic unloading device, 22 Top plate, 23 Rubber bladder sphere, 24 Cylindrical section of male die shape, 25 Transition radius of male die shape. Detailed Implementation

[0035] The present application will be further described in detail below with reference to the accompanying drawings of the embodiments.

[0036] See appendix Figure 1The typical hollow rivet part provided in the embodiment is shown in the figure. The hollow rivet is made of pure aluminum metal, with a height of about 20mm, a flange diameter of about 14mm, and a corner radius of about 1mm between the flange and the rivet shank. Hundreds of different specifications of this type of hollow rivet exist in production and daily life. The original extrusion forming equipment, due to the lack of restriction on the height of the male die, could not control the degree of die closing after the male and female dies were closed, and could only be adjusted manually, resulting in the flange of the part being too thin or too thick. Furthermore, due to the lack of coordination between the male and female dies, the male die ejector rod was manufactured with negative tolerance, while the female die groove was manufactured with positive tolerance, causing the center of the hollow rivet flange to shift during the extrusion process. This resulted in phenomena such as flash caused by the blank flowing along the gap between the male and female dies, making it impossible to form to net dimensions and resulting in a large amount of scrap. Therefore, there is an urgent need for a near-net-shape cold extrusion forming die suitable for various types, larger sizes, and complex structures of hollow rivets.

[0037] like Figures 2-6 As shown, the present invention provides a near-net-shape cold extrusion forming die for hollow rivets, comprising the following steps:

[0038] Step 1: Construct the unfolded blank of the hollow rivet;

[0039] Step 2: Design the extrusion die required for cold extrusion forming of hollow rivets based on the unfolded blank;

[0040] Step 3: Lay the unfolded blank on the cold extrusion die structure for extrusion forming;

[0041] Step 4: After extrusion molding, the hollow rivet with the net size of the molded part will automatically pop out.

[0042] Optionally, step 1 involves constructing the unfolded blank 2 of the hollow rivet 1, and the specific process is as follows:

[0043] The calculation method for the extrusion forming raw material process unfolded blank 2 is the equal weight conversion method. The hollow rivet 1 model is imported into CAT IA software, and the annular unfolded blank 2 is designed. The inner diameter of the annular hole is equal to the diameter of the inner shaft 3 of the hollow rivet, and the outer diameter is close to the diameter of the flange face 4 of the hollow rivet, which can be slightly smaller than the diameter of the flange face 4 of the hollow rivet. The thickness of the unfolded blank 2 is adjusted so that the weight of the unfolded blank 2 is consistent with the weight of the hollow rivet.

[0044] Define the thickness of the unfolded blank as η, and the thickness of the hollow rivet part as δ.

[0045] Optionally, step 2 involves designing the extrusion die required for the cold extrusion forming of the hollow rivet 1 based on the unfolded blank 2. The specific process is as follows:

[0046] Step 3-1: Design the structure of the extrusion male die 5

[0047] The main body of the extrusion male die 5 includes: male die shape 7, extrusion ejector 8, reinforcing cone 9, and male die base 10; the male die shape 7 is composed of a transition radius, a cylindrical section, and a guide; the length of the extrusion ejector 8 is greater than the length of the hollow rivet 1, and the forming surface 18 of the extrusion ejector is slightly larger than the outer contour dimension of the unfolded blank 2; the reinforcing cone 9 and the extrusion ejector 8 are connected by a platform transition, and the reinforcing cone 9 and the extrusion ejector 8 maintain an opening angle of 45-60 degrees; the male die base 10 adopts a platform structure, the platform is slotted and connected to the reinforcing cone 9, and an upper template is made on the platform, the specifications of which are determined according to the equipment table surface;

[0048] Step 3-2: Design the structure of the extrusion die 6

[0049] The main body of the extrusion die 6 includes: a die body 12, a pressure ring 13, and a die base 14. The die body 12 has a trapezoidal structure with a conical outer contour. The die body 12 has a central slot, which includes a forming groove 15 and an ejector pin groove 16. The forming groove 15 matches the outer surface of the hollow rivet 1, and the ejector pin groove 16 matches the diameter of the extrusion ejector pin 8. The pressure ring 13 has a cuboid structure with a conical hole that fits the outer shape of the die body. The die base 14 has a platform structure, and the platform with a slot is connected and fixed to the pressure ring 13 by screws 17.

[0050] Optionally, the male mold body 7 described in step 3-1 is composed of a male mold body transition radius 25, a male mold body cylindrical section 24, and a guide 11. The formula for calculating the size of the male mold body transition radius 25 is R+δ, where R is the transition radius size between the hollow rivet flange surface 4 and the hollow rivet rod.

[0051] The formula for calculating the length of the cylindrical segment 24 of the male mold is η+δ. The diameter of the cylindrical segment of the male mold matches the inner axial surface 3 of the hollow rivet to minimize the gap.

[0052] The guide 11 is rounded on the contact surface between the cylindrical section 24 of the male mold and the unfolded blank 2. The rounding radius is equal to the diameter of the cylindrical section 24 of the male mold, so that the male mold 7 can fit with the inner hole of the unfolded blank 2 during the extrusion process, and the center position of the unfolded blank will not shift during the extrusion forming process.

[0053] The above formula ensures that the front and rear volumes of the unfolded blank 2 are equal during the extrusion forming process. The volume of the hollow rivet flange and the rivet rod raw material is distributed according to the requirements of the part drawing. At the same time, the rivet rod grows in the vertical direction and the rivet rod material thickness is evenly distributed.

[0054] Optionally, in step 3-1, the forming surface 18 of the extrusion die 5 and the extrusion ejector 8 is set to be slightly larger than the outer contour dimension of the hollow rivet flange surface 4, and the calculation formula is D = (1.05~1.15) × d;

[0055] Where D is the diameter of the forming surface 18 of the extrusion pin, and d is the diameter of the flange surface 4 of the hollow rivet.

[0056] Optionally, the groove of the female mold body 12 in step 3-2 includes a forming groove 15 and an ejector groove 16. A positioning groove 19 can be added to the upper end of the ejector groove 16 of the female mold body 12. The diameter of the positioning groove 19 is 1.2 times the outer contour diameter of the unfolded blank 2. At the same time, it is necessary to ensure that the reinforcing cone 9 of the extrusion die 5 and the connecting boss of the male mold body 7 are in a gapless fit with the positioning groove 19. The positioning groove 19, through its joint action with the guide 11, makes the unfolded blank 2 located at the center position in the extrusion forming process.

[0057] The female mold body 12 and the ejector groove 16 are matched in diameter with the extrusion ejector 8 using a zero-clearance fit. This prevents flash from flowing along the gap during the forming process of the unfolded blank 2, achieving net-size forming and reducing the problem of the hollow rivet flange surface 4 being too thin due to flash.

[0058] The lower end of the forming groove 15 of the female mold body 12 can be completely opened through the female mold body 12, specifically as a trumpet-shaped groove 20. The groove wall of the trumpet-shaped groove 20 is deviated from the vertical direction by 2 degrees and opens up, so that air can smoothly enter the gap between the male and female molds during the forming process, which is convenient for unloading.

[0059] The total length of the forming groove 15 of the female mold body 12 needs to be 3 / 4 of the height of the hollow rivet 1 to ensure that the hollow rivet 1 exceeds the lower surface of the female mold body 12 during the extrusion forming process as the height of the hollow rivet 1 increases, in preparation for subsequent automatic unloading;

[0060] Optionally, the extrusion die and the extrusion mold must fit together completely after they are joined. The shape of the die 12 and the shape of the mold 7 are matched. The calculation formula is: δ=Hh;

[0061] Wherein, H is the height dimension from the lower surface of the ejector groove 16 of the female mold body 12 to the upper surface of the female mold body 12, and h is the dimension from the lower surface of the male mold seat 10 of the extrusion male mold 6 to the forming surface 18 of the extrusion ejector.

[0062] This formula can precisely control the thickness of the hollow rivet flange face 4 after extrusion forming, preventing the hollow rivet flange face 4 from being too thin or too thick, achieving net size forming, and reducing product scrap problems caused by incorrect thickness of the hollow rivet flange face 4.

[0063] Optionally, the female mold base 14 is slotted and connected to the lower end of the groove of the female mold body 12 for installing the rubber bladder automatic unloading device 21, specifically the rubber bladder ball 23 connected to the top plate 22. The rubber bladder ball 23 is a sphere in the free state. After the extrusion male mold 5 and the extrusion female mold 6 are closed, the hollow rivet 1 grows, causing the top plate 22 to be subjected to force and move downward, and the rubber bladder ball 23 contracts. After the extrusion male mold 5 and the extrusion female mold 6 are separated, the rubber bladder ball 23 rebounds, and the top plate 22 ejects the hollow rivet from the female mold.

[0064] Optionally, in step 3, the unrolled blank 2 is laid on the extrusion die cooling structure for extrusion forming, and the specific process is as follows:

[0065] Step 3-1: Install the extrusion molding die

[0066] The extrusion male die 5 and the extrusion female die 6 are installed on the worktable of the extrusion forming machine. The extrusion female die 6 is fixed to the worktable of the extrusion forming machine. The extrusion male die 5 can move up and down. The forming working surfaces of the extrusion male die 5 and the extrusion female die 6 are coated with lubricating oil.

[0067] Step 3-2: Unfold the blank and position it.

[0068] The unrolled blank 2 is placed on the working surface of the extrusion die 6 according to the positioning groove 19 on the extrusion die 6;

[0069] Step 3-3: Extrusion molding

[0070] The extrusion male die 5 moves downward and touches the extrusion female die 6. It clamps the unfolded blank 2 with the extrusion female die 6 and applies pressure P to the unfolded blank 2, causing the unfolded blank 2 to undergo plastic deformation in the ejector groove 16 of the female die body 12. The unfolded blank 2 flows downward along the gap between the male and female dies and adheres to the forming groove 15 of the extrusion female die 6 to form the cavity of the part.

[0071] Optionally, after step 4, the hollow rivet 1 with the net dimensions after forming is automatically ejected. The specific process is as follows:

[0072] During the extrusion molding process, the hollow rivet 1 grows, and the lower end of the rivet extends beyond the lower surface of the female mold body 12, causing the top plate 22 to be stressed and the rubber bladder 23 to contract. After the extrusion male mold 5 and the extrusion female mold 6 separate, the rubber bladder 23 rebounds, the top plate 22 moves upward, and the hollow rivet 1 is ejected from the extrusion female mold 6.

Claims

1. A near-net-shape cold extrusion forming die for hollow rivets, characterized in that, include: Extrusion male die (5) and extrusion female die (6); The extrusion die (5) includes: a die body and a die base (10); The male mold body is fixed on the male mold base (10) and is an integral structure. From bottom to top, it includes: male mold body (7), extrusion ejector (8), and reinforcing cone (9). The length of the extrusion rod (8) is greater than the length of the hollow rivet (1), and the forming surface of the extrusion rod (8) is greater than the outer contour dimension of the unfolded blank (2); the unfolded blank (2) is annular, with an inner diameter equal to the diameter of the inner shaft (3) of the hollow rivet, an outer diameter equal to the diameter of the flange face (4) of the hollow rivet, and the weight of the unfolded blank (2) is the same as the weight of the hollow rivet; The male mold body (7) includes: a male mold body transition radius (25), a male mold body cylindrical section (24), and a guide (11); the length of the male mold body cylindrical section (24) is η+δ, the diameter of the male mold body cylindrical section (24) matches the shape of the hollow rivet inner shaft (3), and η is the thickness of the unfolded blank; the value of the male mold body transition radius (25) between the male mold body cylindrical section (24) and the extrusion rod (8) is R+δ, where R is the transition radius dimension between the hollow rivet flange surface (4) and the hollow rivet rod, and δ is the thickness of the hollow rivet part; the guide (11) is made rounded on the contact surface between the male mold body cylindrical section (24) and the unfolded blank (2), and the rounding radius is equal to the diameter of the male mold body cylindrical section (24); The extrusion die (6) includes: a die body (12) and a die base (14), with the die body (12) fixed on the die base (14); The female mold body (12) has a trapezoidal structure with a cone-shaped outer contour and a central slot. The slot includes a forming slot (15) and an ejector slot (16). The forming slot (15) matches the outer surface of the hollow rivet (1). The unfolded blank (2) is set in the ejector slot (16). The ejector slot (16) matches the diameter of the extrusion ejector (8) and adopts a clearance-free fit. The depth of the ejector slot (16) is H=δ+h, where h is the dimension from the lower surface of the male mold base (10) to the forming surface (18) of the extrusion ejector.

2. The near-net-shape cold extrusion forming die for hollow rivets according to claim 1, characterized in that, The reinforcing cone (9) and the extrusion rod (8) are connected by a platform transition, and the reinforcing cone (9) and the extrusion rod (8) maintain an opening angle of 45-60 degrees.

3. The near-net-shape cold extrusion forming die for hollow rivets according to claim 2, characterized in that, The top of the push rod groove (16) is provided with a positioning groove (19). The diameter of the positioning groove (19) is 1.2 times the outer contour diameter of the unfolded blank (2). The connecting boss of the reinforcing cone (9) and the extrusion push rod (8) is in a gapless fit with the positioning groove (19).

4. The near-net-shape cold extrusion forming die for hollow rivets according to claim 1, characterized in that, The lower end of the forming groove (15) is opened through the female mold body (12) to form a trumpet-shaped groove (20). The wall of the trumpet-shaped groove (20) is deviated from the vertical direction by 2 degrees and opens up. The total length of the forming groove (15) should be 3 / 4 of the height of the hollow rivet (1).

5. The near-net-shape cold extrusion forming die for hollow rivets according to claim 4, characterized in that, The female mold base (14) is slotted and connected to the lower end of the groove of the female mold body (12) for installing the rubber bladder automatic unloading device (21). The automatic unloading device (21) for rubber bladder includes a top plate (22) and a rubber bladder ball (23). The top plate (22) is positioned above the rubber bladder ball (23). The rubber bladder ball (23) is a sphere in its free state. After the extrusion male mold (5) and the extrusion female mold (6) are closed, the blank (2) is unfolded and deformed, causing the top plate (22) to be subjected to force and move downward. The rubber bladder ball (23) contracts. After the extrusion male mold (5) and the extrusion female mold (6) are separated, the rubber bladder ball (23) rebounds, and the top plate (22) ejects the hollow rivet from the female mold.

6. The near-net-shape cold extrusion forming die for hollow rivets according to claim 1, characterized in that, The male mold base (10) adopts a platform structure, and the platform is slotted and connected to the reinforcing cone (9).

7. The near-net-shape cold extrusion forming die for hollow rivets according to claim 1, characterized in that, The diameter D of the forming surface (18) of the extrusion push rod is (1.05~1.15)×d; Where d is the diameter of the hollow rivet flange face (4).

8. The near-net-shape cold extrusion forming die for hollow rivets according to claim 1, characterized in that, The extrusion die (6) also includes: a pressure ring (13); The pressure ring (13) is a cuboid structure with a conical hole, which fits the shape of the female mold body (12). The female mold base (14) adopts a platform structure, and the platform is slotted and connected to the pressure ring (13) with screws (17).

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