Near-net cold extrusion forming die for hollow rivet

Abstract

According to the structure of the hollow rivet, an equal-weight conversion method is adopted to construct an unfolded blank circular ring, an extrusion male die and extrusion female die tool structure needed by cold extrusion forming is designed, a formula is established to quantitatively design the structures of all parts of the female and male die forming surfaces, and by limiting the height of the male die body, the near-net cold extrusion forming die for the hollow rivet is obtained. The die assembly gap is adjusted, the thickness of a part flange is accurately controlled, through control over the gap between the male die extrusion ejector rod and the female die ejector rod groove, the phenomenon that a blank flows along the gap between the male die and the female die to generate flashes and the like is prevented, net size forming is achieved, the rejection rate in the production process is reduced, and the production efficiency of hollow rivets is improved.

Description

Technical Field

[0001] The invention relates to a sheet metal rivet parts extrusion forming technology in the field of aircraft manufacturing, in particular to a hollow rivet near-net cold extrusion forming die. Background Art

[0002] Rivets are widely used in a wide range of fields, from aerospace to sports products, from automobile machine tools to office appliances. There are many types of rivets, the commonly used ones are: R-type, tree-shaped, hollow, solid, semi-hollow, core-driving and core-pulling, etc. Rivets can be connectors, protective parts and decorative parts. Hollow rivets are rivets used between the holes of parts made of metal materials and non-metallic materials. On the basis of semi-hollow rivets, the countersunk hole is processed all the way to the head. Due to its light weight and weak nail head, it is used for riveting non-metallic materials with small loads. Hollow rivets are also widely used. They can be used in civilian industries such as clothing and footwear, and can also be used to cover various military fields such as ship artillery, aerospace, etc.

[0003] It is known that traditional hollow rivets are generally formed by pure aluminum or brass or copper thin sheets. Taking pure aluminum as an example, it has the characteristics of being able to be strengthened, having low density, being easy to process, and having low density. The traditional hollow rivet processing method is to use a certain specification of pipe to process through a corresponding expansion forming process. Since the hollow rivet has a small external dimension, the pipe blank size is also relatively small during the expansion process, which makes it inconvenient to clamp and the blank is easy to lose stability. The processed parts flange and the rod corner radius become thinner and are easy to crack, and the processing quality is unstable. At present, the CN115958079A patent proposes a short hollow rivet cold extrusion forming die, which preliminarily solves the extrusion forming tooling structure of standard short hollow rivets, but the 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 with flange rings or a height of more than 10mm. At the same time, since the height of the male die convex extrusion section is not limited, the degree of mold closing cannot be controlled after the male and female dies are closed, and the mold closing gap can only be adjusted manually, resulting in the flange of the part being too thin or too thick. In addition, since the gap between the male and female dies is not coordinated, the male die ejector is manufactured using a negative difference, and the female die slot is manufactured using a positive difference, resulting in the center of the hollow rivet flange being offset during the extrusion process, and the blank flowing along the gap between the male and female dies to produce flash, etc., which makes it impossible to form the net size and results in a large amount of scrap. Therefore, there is an urgent need for a near-net cold extrusion forming die for hollow rivets that is suitable for a variety of large sizes and complex structures. Summary of the invention

[0004] The invention provides a hollow rivet near-net cold extrusion forming die, which is suitable for near-net cold extrusion forming of hollow rivets of various types, larger sizes and complex structures.

[0005] The present invention provides a hollow rivet near-net cold extrusion forming die, comprising: an extrusion male die 5 and an extrusion female die 6;

[0006] The extrusion male mold 5 comprises: a male mold body and a male mold base 10; the male mold body is fixed on the male mold base 10, and is an integrated structure, and comprises from bottom to top: a male mold body 7, an extrusion ejector rod 8, and a reinforcing cone 9;

[0007] The rod length of the extrusion ejector rod 8 is greater than the rod length of the hollow rivet 1, and the extrusion ejector rod forming surface of the extrusion ejector rod 8 is greater than the outer contour size of the unfolded blank 2; the unfolded blank 2 is annular, the inner hole diameter is equal to the diameter of the inner shaft 3 of the hollow rivet, the outer diameter is equal to the diameter of the flange surface 4 of the hollow rivet, and the weight of the unfolded blank 2 is consistent with 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 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 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 section 24 and the extrusion ejector 8 is R+δ, where R is the transition radius size between the hollow rivet flange surface 4 and the hollow rivet nail rod, and δ is the thickness of the hollow rivet part; the guide 11 is for rounding 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 round male mold body cylindrical section 24;

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

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

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

[0012] Optionally, a positioning groove 19 is provided at the upper end of the ejector groove 16 , and the diameter of the positioning groove 19 is 1.2 times the outer contour diameter of the unfolded blank 2 , so that the connecting boss between the vertebral body 9 and the extruded ejector 8 fits 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 groove wall of the trumpet-shaped groove 20 is opened 2 degrees away from the vertical direction;

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

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

[0016] The rubber bag automatic unloading device 21 includes: a top plate 22 and a rubber bag sphere 23. The top plate 22 is arranged above the rubber bag sphere 23. The rubber bag sphere 23 is a sphere in a free state. After the extrusion male mold 5 and the extrusion female mold 6 are molded together, the blank 2 is unfolded and deformed, so that the top plate 22 is forced to move downward, and the rubber bag sphere 23 shrinks. After the extrusion male mold 5 and the extrusion female mold 6 are separated, the rubber bag sphere 23 rebounds, and the top plate 22 pops the hollow rivet out of the female mold.

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

[0018] Optionally, the diameter of the extrusion ejector forming surface 18 is D=(1.05-1.15)×d;

[0019] Wherein, d is the diameter of the hollow rivet flange surface 4.

[0020] Optionally, the extrusion female die 6 further comprises: a pressing ring 13;

[0021] The pressing ring 13 is a rectangular parallelepiped structure with a tapered hole, which matches the outer shape of the female mold body 12 ; the female mold base 14 is a table structure with a slot in the table connected and fixed to the pressing ring 13 by screws 17 .

[0022] The beneficial effects of this application are:

[0023] 1) The present invention provides a hollow rivet near-net cold extrusion forming die. By designing a cold extrusion forming die with a widely applicable structure, the problem that the blank is easy to become unstable during the expansion forming of the traditional hollow rivet, the radius of the corner between the flange and the rod becomes thinner and easy to crack is solved. The problem that the traditional extrusion forming die is only suitable for standard short-rod hollow rivets is solved, the application range of the die is expanded, and the die has important practical value;

[0024] 2) The present invention provides an equal weight conversion method for calculating the expanded blank of a hollow rivet, by designing a circular expanded blank, the inner diameter of the circular ring is equal to the inner shaft diameter of the hollow rivet, the outer diameter is slightly smaller than the flange surface diameter, and the blank thickness is adjusted to make the blank weight consistent with the hollow rivet weight. The method accurately calculates the raw material deformation during the plastic flow of the plate during the extrusion forming process, achieves the purpose of net size forming, and reduces the amount of trimming after forming;

[0025] 3) The present invention provides a method for limiting the flow of the blank during the extrusion forming process of the hollow rivet, which limits the height of the male mold and adjusts the mold clearance to achieve accurate control of the flange thickness of the part, and prevents the blank from flowing along the gap between the male and female molds to produce flash and the like through the gap between the male mold extrusion push rod and the female mold push rod groove, thereby achieving net size forming, reducing the scrap rate in the production process, and reducing the workload of manual finishing;

[0026] 4) The present 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 has a large workload, reduces the working hours in the production process, and improves production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0029] Figure 3 It is a schematic diagram of the structure of the extrusion die;

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

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

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

[0033] Description of the numbers in the figure:

[0034] 1 hollow rivet, 2 unfolded blank, 3 hollow rivet inner shaft, 4 hollow rivet flange surface, 5 extrusion male die, 6 extrusion female die, 7 male die body, 8 extrusion ejector pin, 9 reinforcing cone, 10 male die seat, 11 guide, 12 female die body, 13 pressure ring, 14 female die seat, 15 forming groove, 16 ejector pin groove, 17 screw, 18 extrusion ejector pin forming surface, 19 positioning groove, 20 trumpet-shaped groove, 21 rubber bag automatic unloading device, 22 ejector plate, 23 rubber bag sphere, 24 male die body cylindrical section, 25 male die body transition radius. DETAILED DESCRIPTION

[0035] The present application is further described in detail below in conjunction with the accompanying drawings of the embodiments.

[0036] See attached Figure 1, as shown in the figure, the typical hollow rivet parts provided in the embodiment are made of pure aluminum metal material, 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 rod. There are hundreds of hollow rivets of various specifications in production and life. The original extrusion forming process equipment does not limit the height of the male mold, and the degree of mold closing cannot be controlled after the male and female molds are closed. The mold closing gap can only be adjusted manually, resulting in the flange of the part being too thin or too thick. In addition, due to the lack of coordination of the male and female mold gaps, the male mold ejector rod is manufactured using a negative difference, and the female mold trough body is manufactured using a positive difference, resulting in the center of the hollow rivet flange being offset during the extrusion process, and the blank flowing along the gap between the male and female molds to produce flash and other phenomena, which makes it impossible to form the net size, and the scrap volume is large. Therefore, there is an urgent need for a near-net cold extrusion forming die for hollow rivets that is suitable for a variety of large sizes and complex structures.

[0037] like Figure 2 to Figure 6 As shown, the present invention provides a hollow rivet near-net cold extrusion forming die, comprising the following steps:

[0038] Step 1, constructing an expanded blank of a hollow rivet;

[0039] Step 2, designing the extrusion die required for cold extrusion forming of the hollow rivet according to the unfolded blank;

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

[0041] Step 4: After extrusion forming, the hollow rivet with the net size after forming will automatically pop out.

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

[0043] The calculation method of the expanded blank 2 of the extrusion forming raw material process is the equal weight conversion method. The hollow rivet 1 model is imported into the CATIA software, and the circular expanded blank 2 is designed. The inner diameter of the circular ring 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 hollow rivet flange surface 4, which can be slightly smaller than the diameter of the hollow rivet flange surface 4. The thickness of the expanded blank 2 is adjusted to make the weight of the expanded blank 2 consistent with the weight of the hollow rivet.

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

[0045] Optionally, the step 2 designs an extrusion die required for cold extrusion forming of the hollow rivet 1 according to the unfolded blank 2, and the specific process is as follows:

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

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

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

[0049] The main body of the extrusion female die 6 includes: a female die body 12, a pressure ring 13 and a female die seat 14. The female die body 12 is a trapezoidal structure with a cone outer contour. The female die body 12 is slotted in the center. The slot body includes a forming slot 15 and a push rod slot 16. The forming slot 15 slot body matches the outer surface of the hollow rivet 1, and the push rod slot 16 matches the diameter of the extrusion push rod 8. The pressure ring 13 is a rectangular parallelepiped structure with a tapered hole, which matches the outer shape of the female die body. The female die seat 14 adopts a table structure, and the table slot is connected and fixed to the pressure ring 13 by screws 17.

[0050] Optionally, the male mold body 7 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, and the male mold body transition radius 25 size calculation formula is R+δ, where R is the transition radius size between the hollow rivet flange surface 4 and the hollow rivet shank;

[0051] The length calculation formula of the male mold cylindrical section 24 is η+δ, and the diameter of the male mold cylindrical section matches the inner shaft surface 3 of the hollow rivet to minimize the gap;

[0052] The guide 11 is rounded at the contact surface between the male mold body cylindrical section 24 and the expanded blank 2, and the rounding radius is equal to the diameter of the male mold body cylindrical section 24, so that the male mold body 7 can cooperate with the inner hole of the expanded blank 2 during the extrusion process, so that the center position of the expanded blank will not be offset during the extrusion forming process;

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

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

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

[0056] Optionally, the groove body of the female mold body 12 in step 3-2 includes a forming groove 15 and a push rod groove 16. A positioning groove 19 can be additionally provided at the upper end of the push rod 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 reinforced cone 9 of the extrusion male mold 5 and the connecting boss of the male mold body 7 are matched with the positioning groove 19 without clearance. The positioning groove 19 cooperates with the guide 11 to make the unfolded blank 2 located at the center of the extrusion forming process;

[0057] The ejector groove 16 of the female mold body 12 matches the diameter of the extrusion ejector 8, and adopts a gap-free fit to prevent the problem of flash generated by the flow along the gap during the forming process of the unfolded blank 2, realize net size forming, and reduce the problem of the hollow rivet flange surface 4 being too thin due to the flash.

[0058] The lower end of the forming groove 15 of the female mold body 12 can completely open the female mold body 12, specifically a trumpet-shaped groove 20, and the wall of the trumpet-shaped groove 20 is opened 2 degrees away from the vertical direction, 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 process of increasing the height of the hollow rivet 1 during the extrusion forming process, so as to prepare for the subsequent automatic unloading;

[0060] Optionally, the extrusion female mold 5 and the extrusion male mold 6 need to be completely fitted after the mold is closed, and the female mold body 12 and the male mold body 7 are in a matching relationship, and the calculation formula is: δ = Hh;

[0061] Among them, 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 extrusion ejector forming surface 18.

[0062] This formula can accurately control the thickness of the hollow rivet flange surface 4 after extrusion forming, prevent the hollow rivet flange surface 4 from being too thin or too thick, achieve net size forming, and reduce the problem of product scrapping caused by incorrect thickness of the hollow rivet flange surface 4;

[0063] Optionally, the female mold seat 14 is grooved and connected to the lower end of the groove body of the female mold body 12, and is used to install an automatic unloading device 21 for the rubber bag, specifically a rubber bag sphere 23 connected to the top plate 22. The rubber bag sphere 23 is a sphere in a 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 move downward under force, and the rubber bag sphere 23 shrinks. After the extrusion male mold 5 and the extrusion female mold 6 are separated, the rubber bag sphere 23 rebounds, and the top plate 22 pops the hollow rivet out of the female mold.

[0064] Optionally, in step 3, the unfolded blank 2 is laid on a cold structure of an extrusion die for extrusion forming, and the specific process is as follows:

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

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

[0067] Step 3-2: Expand blank 2 and position it

[0068] Place the expanded blank 2 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

[0070] The extrusion male die 5 moves downward, and after touching the extrusion female die 6, it clamps the expanded blank 2 with the extrusion female die 6, and applies pressure P to the expanded blank 2, so that the expanded blank 2 is plastically deformed in the ejector groove 16 of the female die body 12, and the expanded blank 2 flows downward along the gap between the male and female diaphragms, and abuts against the extrusion female die 6 to form the groove 15 of the groove body cavity to form the part;

[0071] Optionally, in step 4, the hollow rivet 1 with a net size after extrusion forming is automatically ejected, and the specific process is as follows:

[0072] During the extrusion forming process, the shank of the hollow rivet 1 grows, and the lower end of the shank exceeds the lower surface of the female mold body 12, so that the top plate 22 is stressed and the rubber bag sphere 23 shrinks; after the extrusion male mold 5 is separated from the extrusion female mold 6, the rubber bag sphere 23 rebounds, the top plate 22 moves up, and the hollow rivet 1 is ejected from the extrusion female mold 6.

Claims

1. A hollow rivet near-net cold extrusion forming die, characterized in that: include: An extrusion male die (5) and an extrusion female die (6); The extrusion male die (5) comprises: a male die body and a male die seat (10); The male mold body is fixed on the male mold base (10) and is an integrated structure, which comprises, from bottom to top, a male mold body (7), an extrusion ejector rod (8), and a reinforcing cone (9); The rod length of the extrusion ejector rod (8) is greater than the rod length of the hollow rivet (1), and the extrusion ejector rod forming surface of the extrusion ejector rod (8) is greater than the outer contour size of the unfolded blank (2); the unfolded blank (2) is annular, the inner hole diameter is equal to the diameter of the inner shaft (3) of the hollow rivet, the outer diameter is equal to the diameter of the flange surface (4) of the hollow rivet, and the weight of the unfolded blank (2) is consistent with the weight of the hollow rivet; The male mold body (7) comprises: a male mold body transition radius 2 (5), 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 surface 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 ejector (8) is R+δ, wherein R is the transition radius size 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 used to round 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 round male mold body cylindrical section (24); The extrusion female die (6) comprises: a female die body (12) and a female die seat (14), wherein the female die body (12) is fixed on the female die seat (14); The female mold body (12) is a trapezoidal structure, the outer contour is a cone, and the center is slotted. The slot body includes a forming slot (15) and a push rod slot (16). The forming slot (15) matches the outer surface of the hollow rivet (1) shank. The expanded blank (2) is arranged in the push rod slot (16). The push rod slot (16) matches the diameter of the extrusion push rod (8) to adopt a clearance-free fit. The push rod slot (16) has a depth H=δ+h, where h is the dimension from the lower surface of the male mold base (10) to the extrusion push rod forming surface (18).

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

3. The hollow rivet near-net cold extrusion forming die according to claim 2, characterized in that: A positioning groove (19) is arranged at the upper end of the ejector groove (16), the diameter of the positioning groove (19) being 1.2 times the outer contour diameter of the unfolded blank (2), and the connecting boss of the reinforced cone (9) and the extruded ejector rod (8) is matched with the positioning groove (19) without clearance.

4. The hollow rivet near-net cold extrusion forming die according to claim 1, characterized in that: The lower end of the forming groove (15) is connected to the female mold body (12) to form a trumpet-shaped groove (20), and the wall of the trumpet-shaped groove (20) is opened 2 degrees away from the vertical direction; The total length of the forming groove (15) needs to be 3 / 4 of the height of the hollow rivet (1) shank.

5. The hollow rivet near-net cold extrusion forming die according to claim 4, characterized in that: The female mold base (14) is slotted and connected to the lower end of the slot of the female mold body (12) for installing the rubber bag automatic unloading device (21); The rubber bag automatic unloading device (21) comprises: a top plate (22) and a rubber bag sphere (23). The top plate (22) is arranged above the rubber bag sphere (23). The rubber bag sphere (23) is a sphere in a free state. After the extrusion male die (5) and the extrusion female die (6) are molded together, the blank (2) is unfolded and deformed, so that the top plate (22) is forced to move downward, and the rubber bag sphere (23) shrinks. After the extrusion male die (5) and the extrusion female die (6) are separated, the rubber bag sphere (23) rebounds, and the top plate (22) ejects the hollow rivet out of the female die.

6. The hollow rivet near-net cold extrusion forming die according to claim 1, characterized in that: The male mold base (10) adopts a table structure, and the table is grooved and connected to the reinforcing cone (9).

7. The hollow rivet near-net cold extrusion forming die according to claim 1, characterized in that: The diameter of the extrusion ejector pin forming surface (18) is D=(1.05-1.15)×d; Wherein, d is the diameter of the hollow rivet flange surface 4.

8. The hollow rivet near-net cold extrusion forming die according to claim 1, characterized in that: The extrusion female die (6) further comprises: a pressing ring (13); The pressing ring (13) is a rectangular parallelepiped structure with a tapered hole, which matches the outer shape of the female mold body (12); the female mold base (14) adopts a table structure, and the table groove is connected and fixed to the pressing ring (13) by screws (17).

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