A multi-section special-shaped ring groove blind rivet shank one-time thread rolling forming die

Abstract

The present invention provides a multi-section special-shaped ring groove blind rivet shank one-time thread rolling forming die, including a one-time thread rolling forming die. The one-time thread rolling forming die includes a thread rolling die stationary mold M and a thread rolling die moving mold N. The thread rolling die stationary mold M and the thread rolling die moving mold N have the same structure. The thread rolling die stationary mold M and the thread rolling die moving mold N are used to process a target multi-section special-shaped ring groove blind rivet shank A into a multi-section special-shaped ring groove blind rivet shank blank B. The beneficial effects of the present invention are as follows: By applying the thread rolling die proposed by the present invention, multi-section special-shaped ring grooves such as straight ring grooves, snap ring grooves, locking grooves and broken neck grooves with a certain inclination angle of the blind rivet shank can be formed by one-time thread rolling, improving production efficiency.

Description

Technical Field

[0001] The invention belongs to the technical field of the processing of fastener blind rivets, and particularly relates to a one-time thread rolling forming die for the shank of a multi-segment special-shaped ring groove blind rivet. Background Art

[0002] For the rivet shank containing various ring groove structures, the commonly used processing methods include: lathe processing method, multi-pass rolling method, combined method of rolling and lathe processing, multi-pass thread rolling, and one-time thread rolling forming method. The neck-breaking groove of the blind rivet shank has a small opening and a large depth. The use of turning processing has low production efficiency and damages the metal fibers, resulting in a decline in the quality of the shank. The use of rolling processing or thread rolling forming often requires a separately designed neck-breaking groove processing die, resulting in low processing efficiency. The current processing methods are also difficult to achieve high-efficiency and precision processing of the neck-breaking groove with an inclination feature. Summary of the Invention

[0003] In view of this, the invention aims to provide a one-time thread rolling forming die for the shank of a multi-segment special-shaped ring groove blind rivet to achieve the high-efficiency and precise forming of multi-segment special-shaped ring grooves such as straight ring grooves, snap ring grooves, locking grooves, and neck-breaking grooves with a certain inclination angle on the rivet shank.

[0004] To achieve the above object, the technical solution of the invention is realized as follows:

[0005] A one-time thread rolling forming die for the shank of a multi-segment special-shaped ring groove blind rivet, including a one-time thread rolling forming die, the one-time thread rolling forming die includes a thread rolling die stationary mold M and a thread rolling die moving mold N, the thread rolling die stationary mold M and the thread rolling die moving mold N have the same structure, and the thread rolling die stationary mold M and the thread rolling die moving mold N are used to process a target multi-segment special-shaped ring groove blind rivet shank A into a multi-segment special-shaped ring groove blind rivet shank blank B;

[0006] The processing method of the one-time thread rolling forming die includes the following steps:

[0007] S1. Calculate the biting depth of each ring groove for processing the target multi-segment special-shaped ring groove blind rivet shank A into a multi-segment special-shaped ring groove blind rivet shank blank B;

[0008] S2. Segment the one-time thread rolling forming die according to each ring groove of the target multi-segment special-shaped ring groove blind rivet shank A, and set the length of the one-time thread rolling die;

[0009] S3. Calculate the parameters of each segment of the one-time thread rolling forming die after segmentation;

[0010] S4. Obtain the one-time thread rolling forming die.

[0011] Further, the stationary die M of the thread rolling die includes a stationary die body, a straight ring groove thread rolling die biting part, a snap ring groove thread rolling die biting part, a neck breaking groove thread rolling die biting part, a locking groove thread rolling die biting part, a neck breaking groove thread rolling die shaping part, a thread rolling die withdrawing part, and a rivet core rod head clamping part. The straight ring groove thread rolling die biting part, the snap ring groove thread rolling die biting part, the neck breaking groove thread rolling die biting part, and the locking groove thread rolling die biting part are sequentially arranged from bottom to top on the left side of the stationary die body. The rivet core rod head clamping part is arranged above the stationary die body. The neck breaking groove thread rolling die shaping part is arranged in the middle of the stationary die body. The thread rolling die withdrawing part is arranged on the right side of the stationary die body.

[0012] Further, in step S1, the target multi-segment special-shaped ring groove blind rivet core rod A is provided with a straight ring groove, a snap ring groove, a neck breaking groove, and a locking groove in sequence from left to right, and the locking groove has an inclination angle with respect to the radial direction of the rivet core rod of the target multi-segment special-shaped ring groove blind rivet core rod A.

[0013] Further, in step S1, the calculation of the biting depth of each ring groove includes the following steps:

[0014] S11: Overlap and place the multi-segment special-shaped ring groove blind rivet core rod blank B and the model of the target multi-segment special-shaped ring groove blind rivet core rod A.

[0015] S12: Calculate the biting depth h1 of the straight ring groove, the biting depth h2 of the snap ring groove, the biting depth h3 of the neck breaking groove, and the biting depth h4 of the locking groove respectively according to the minimum outer diameter d1 of the rivet core rod straight ring groove, the minimum outer diameter d2 of the rivet core rod snap ring groove, the minimum outer diameter d3 of the rivet core rod neck breaking groove, the minimum outer diameter d4 of the rivet core rod locking groove, the outer diameter D1 of the straight ring groove part of the rivet core rod blank, the outer diameter D2 of the snap ring groove part of the rivet core rod blank, the outer diameter D3 of the neck breaking groove part of the rivet core rod blank, and the outer diameter D4 of the locking groove part of the rivet core rod blank.

[0016] Further, the biting depth h1 of the straight ring groove = 0.5(d1 - D1), the biting depth h2 of the snap ring groove = 0.5(d2 - D2), the biting depth h3 of the neck breaking groove = 0.5(d3 - D3), and the biting depth h4 of the locking groove = 0.5(d4 - D4).

[0017] Further, in step S2, segmenting the primary thread rolling forming die according to each ring groove of the target multi-segment special-shaped ring groove blind rivet core rod A and setting the length of the primary thread rolling die includes the following steps:

[0018] S21: Open convex edges at the corresponding positions of the primary thread rolling die according to the straight ring groove, the snap ring groove, the neck breaking groove, and the locking groove.

[0019] S22. Divide the convex edges of the primary thread rolling die corresponding to the straight ring groove, snap ring groove, and locking groove into a biting section, a finishing section, and a withdrawing section respectively, and divide the convex edge of the primary thread rolling die corresponding to the neck-breaking groove into a biting section, a sizing section, a finishing section, and a withdrawing section;

[0020] S23. Set the length of the primary thread rolling die to the sum of the biting section length L1, the neck-breaking groove sizing section length L2, the finishing section length L3, and the withdrawing section length L4.

[0021] Furthermore, in step S3, calculate the parameters of each section of the formed and segmented primary thread rolling die respectively, including the following steps:

[0022] S31. Calculate the parameters of the biting section of the primary thread rolling die;

[0023] S32. Calculate the parameters of the withdrawing section of the primary thread rolling die;

[0024] S32. Set the neck-breaking groove sizing section length L2 of the primary thread rolling die ≥ πd2, and set the finishing section length L3 of the primary thread rolling die ≥ 4πd2.

[0025] Furthermore, in step S31, calculate the parameters of the biting section of the primary thread rolling die, including the following steps:

[0026] S311. Set that each section's biting angle α, biting depth h, and biting section length L1 satisfy tanα = h / L1, and set that each section's biting angle α is the same, and the biting angle α takes the minimum value of the calculated biting angles of each section;

[0027] S312. Set the biting part length L1-1 of the straight ring groove ≥ 2πd1, set the biting part length L1-2 of the snap ring groove ≥ 2πd2, set the biting part length L1-3 of the neck-breaking groove ≥ 2πd3, and set the biting part length L1-4 of the locking groove ≥ 2πd4.

[0028] Furthermore, in step S32, calculate the parameters of the withdrawing section of the primary thread rolling die, including the following steps:

[0029] S321. Set that each section's withdrawing angle β, biting depth h, and withdrawing section length L4 satisfy tanβ = h / L4, and set that each section's withdrawing angle β takes the minimum value of the calculated withdrawing angles of each section;

[0030] S322. Set the withdrawing section length L4 ≥ πd2.

[0031] Further, the length of the biting-in part of the straight ring groove thread rolling die is L1-1, the length of the biting-in part of the snap ring groove thread rolling die is L1-2, the length of the biting-in part of the neck-breaking groove thread rolling die is L1-3, the length of the biting-in part of the locking groove thread rolling die is L1-4, the length of the shape-correcting part of the neck-breaking groove thread rolling die is L2, the length of the withdrawing part of the thread rolling die is L4, the length of the finishing section is L3, and the length of the clamping part of the head of the rivet core rod is such that the length of the thread rolling die is equal to the sum of L1-3, L2, L3 and L4.

[0032] Compared with the prior art, the multi-section special-shaped ring groove blind rivet core rod one-time thread rolling forming die of the present invention has the following advantages:

[0033] By applying the thread rolling die proposed by the present invention, the multi-section special-shaped ring groove blind rivet core rod one-time thread rolling forming die of the present invention can realize the one-time thread rolling forming of multi-section special-shaped ring grooves such as straight ring grooves, snap ring grooves, locking grooves and neck-breaking grooves with a certain inclination angle of the blind rivet core rod, improving the production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0035] Figure 1 Schematic diagram of the multi-section special-shaped ring groove blind rivet core rod and blank according to the embodiment of the present invention;

[0036] Figure 2 Schematic diagram of the calculation of the biting-in depth of each ring groove according to the embodiment of the present invention;

[0037] Figure 3 Schematic diagram of the forming segmentation and angle calculation of the thread rolling die according to the embodiment of the present invention;

[0038] Figure 4 Schematic diagram of the multi-section special-shaped ring groove blind rivet core rod thread rolling die according to the embodiment of the present invention;

[0039] Figure 5 Schematic cross-sectional view of the biting-in section and shape-correcting section of each ring groove of the thread rolling die according to the embodiment of the present invention;

[0040] Figure 6 Schematic diagram of the starting state of thread rolling of the thread rolling die according to the embodiment of the present invention;

[0041] Figure 7 Schematic diagram of the ending state of thread rolling of the thread rolling die according to the embodiment of the present invention.

[0042] Description of the reference numerals:

[0043] 1. Straight ring groove; 2. Snap ring groove; 3. Neck-breaking groove; 4. Locking groove; 5. Biting part of the straight ring groove thread rolling die; 6. Biting part of the snap ring groove thread rolling die; 7. Biting part of the neck-breaking groove thread rolling die; 8. Biting part of the locking groove thread rolling die; 9. Shape-correcting part of the neck-breaking groove thread rolling die; 10. Withdrawal part of the thread rolling die; 11. Clamping part of the rivet core rod head; 12. Cross-sectional shape of the biting part of the snap ring groove thread rolling die; 13. Cross-sectional shape of the finishing part of the snap ring groove thread rolling die; 14. Cross-sectional shape of the biting part of the straight ring groove thread rolling die; 15. Cross-sectional shape of the finishing part of the straight ring groove thread rolling die; 16. Cross-sectional shape of the biting part of the neck-breaking groove thread rolling die; 17. Starting cross-sectional shape of the shape-correcting part of the neck-breaking groove thread rolling die; 18. Cross-sectional shape of the finishing part of the neck-breaking groove thread rolling die; 19. Cross-sectional shape of the biting part of the locking groove thread rolling die; 20. Cross-sectional shape of the finishing part of the locking groove thread rolling die. Detailed implementation mode

[0044] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0045] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, the meaning of "a plurality" is two or more.

[0046] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection", "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood through specific situations.

[0047] The present invention will be described in detail below with reference to the drawings and in combination with the embodiments.

[0048] As Figures 1 to 7As shown in the figure, a die for one-time thread rolling forming of a multi-segment special-shaped ring groove blind rivet shank calculates the final biting depths of the straight ring groove, snap ring groove, locking groove, and neck-breaking groove respectively according to the target multi-segment special-shaped ring groove blind rivet shank and the shape of its blank, and comprehensively designs the biting angle and the length of the biting section of the thread rolling die in combination with the diameters of the corresponding parts of the ring grooves of each section of the blank to ensure that the ring grooves of each section are bitten synchronously and the biting depths are the same during the thread rolling process. Based on the shape characteristics of the neck-breaking groove, the thread rolling grooves of the neck-breaking groove in the biting section and the finishing section are designed respectively to realize the forming of the inclined neck-breaking groove.

[0049] 1. Calculation of the biting depth of each ring groove: As Figure 1 shown, the target multi-segment special-shaped ring groove blind rivet shank A includes four types of ring grooves: straight ring groove 1, snap ring groove 2, neck-breaking groove 3, and locking groove 4. Among them, the locking groove 4 forms a certain inclination angle with the radial direction of the rivet shank. As Figure 2 shown, the models of the blank B and the multi-segment special-shaped ring groove blind rivet shank A are overlapped and placed. The biting depths h1, h2, h3, and h4 of the straight ring groove, snap ring groove, neck-breaking groove, and locking groove are calculated respectively according to the minimum outer diameter d1 of the straight ring groove of the rivet shank, the minimum outer diameter d2 of the snap ring groove of the rivet shank, the minimum outer diameter d3 of the neck-breaking groove of the rivet shank, the minimum outer diameter d4 of the locking groove of the rivet shank, the outer diameter D1 of the straight ring groove part of the rivet shank blank, the outer diameter D2 of the snap ring groove part of the rivet shank blank, the outer diameter D3 of the neck-breaking groove part of the rivet shank blank, and the outer diameter D4 of the locking groove part of the rivet shank blank. Among them, h1 = 0.5(d1 - D1), h2 = 0.5(d2 - D2), h3 = 0.5(d3 - D3), h4 = 0.5(d4 - D4).

[0050] 2. Schematic diagram of the forming segmentation and angle calculation of the thread rolling die for the multi-segment special-shaped ring groove blind rivet shank is as Figure 3 shown. Among them, the thread rolling dies for forming the straight ring groove 1, snap ring groove 2, and locking groove 4 are divided into a biting section, a finishing section, and an ejection section. The thread rolling die for forming the neck-breaking groove 3 with a certain inclination angle is divided into a biting section, a shape-correcting section, a finishing section, and an ejection section. The length of the thread rolling die is the sum of the length L1 of the biting section, the length L2 of the neck-breaking groove shape-correcting section, the length L3 of the finishing section, and the length L4 of the ejection section.

[0051] 3. Calculation of the parameters of the biting section of the thread rolling die for the multi-segment special-shaped ring groove blind rivet shank: As Figure 3 shown, the biting angle α of each section satisfies tanα = h / L1 with the biting depth h and the length L1 of the biting section. Among them, the length L1-1 of the biting part of the straight ring groove ≥ 2πd1, the length L1-2 of the biting part of the snap ring groove ≥ 2πd2, the length L1-3 of the biting part of the neck-breaking groove ≥ 2πd3, and the length L1-4 of the biting part of the locking groove ≥ 2πd4. To ensure that the ring grooves of each section are bitten synchronously and the biting depths per unit thread rolling length are the same, the biting angles of each section are the same, and the biting angle α takes the minimum value of the biting angles calculated for each section.

[0052] 4. Parameter calculation for the ejection section of the thread rolling die for the core rod of the multi-segment special-shaped ring groove blind rivet: The ejection angle β for each section, the bite-in depth h, and the ejection section length L4 satisfy tanβ = h / L4, where the ejection section length L4 ≥ πd2. The ejection angle β takes the minimum value of the calculated ejection angles for each section.

[0053] 5. The straightening section length L2 of the thread rolling die for the core rod of the multi-segment special-shaped ring groove blind rivet ≥ πd2, and the finishing section length L3 ≥ 4πd2.

[0054] 6. The thread rolling die for the core rod of the multi-segment special-shaped ring groove blind rivet is as Figure 4 shown. The length of the bite-in part 5 of the straight ring groove thread rolling die is L1-1, the length of the bite-in part 6 of the snap ring groove thread rolling die is L1-2, the length of the bite-in part 7 of the neck-breaking groove thread rolling die is L1-3, the length of the bite-in part 8 of the locking groove thread rolling die is L1-4, the length of the straightening part 9 of the neck-breaking groove thread rolling die is L2, the length of the ejection part 10 of the thread rolling die is L4, the length of the finishing section is L3, and the length of the clamping part 11 of the head of the rivet core rod is equal to the sum of L1-3, L2, L3, and L4, which is the length of the thread rolling die.

[0055] 7. The cross-sections of the bite-in sections and the straightening sections of each ring groove of the thread rolling die are as Figure 5 shown. The cross-sectional shapes 12 of the bite-in part of the snap ring groove thread rolling die, 14 of the bite-in part of the straight ring groove thread rolling die, and 19 of the bite-in part of the locking groove thread rolling die at the start of the bite-in section are the same as the cross-sectional shapes 13 of the finishing part of the snap ring groove thread rolling die, 15 of the finishing part of the straight ring groove thread rolling die, and 20 of the finishing part of the locking groove thread rolling die respectively. The cross-sectional shape 16 of the bite-in part of the neck-breaking groove thread rolling die is the same as the starting cross-sectional shape 17 of the straightening part of the neck-breaking groove thread rolling die. For the unformed negative angle part of the cross-section of the neck-breaking groove, the cross-sectional shape of the straightening part of the neck-breaking groove thread rolling die gradually transitions from the starting cross-sectional shape 17 to the finishing cross-sectional shape 18.

[0056] 8. The thread rolling die for the core rod of the multi-segment special-shaped ring groove blind rivet consists of a stationary die M and a moving die N of the thread rolling die with the same shape. The starting state of thread rolling of the thread rolling die is as Figure 6 shown, and the terminating state of thread rolling of the thread rolling die is as Figure 7 shown.

[0057] As Figures 1 - 7Among them, A is the core rod of a multi-section special-shaped ring groove blind rivet, B is the blank of the core rod of a multi-section special-shaped ring groove blind rivet, X1 is the partial enlarged view of the locking groove part of the rivet core rod and the blank, X1 is the partial enlarged view of the straight ring groove part of the rivet core rod and the blank, X2 is the partial enlarged view of the snap ring groove part of the rivet core rod and the blank, X3 is the partial enlarged view of the neck-breaking groove part of the rivet core rod and the blank, X4 is the partial enlarged view of the locking groove part of the rivet core rod and the blank, d1 is the minimum outer diameter of the straight ring groove of the rivet core rod, d2 is the minimum outer diameter of the snap ring groove of the rivet core rod, d3 is the minimum outer diameter of the neck-breaking groove of the rivet core rod, d4 is the minimum outer diameter of the locking groove of the rivet core rod, D1 is the outer diameter of the straight ring groove part of the rivet core rod blank, D2 is the outer diameter of the snap ring groove part of the rivet core rod blank, D3 is the outer diameter of the neck-breaking groove part of the rivet core rod blank, D4 is the outer diameter of the locking groove part of the rivet core rod blank, h1 is the biting depth of the straight ring groove, h2 is the biting depth of the snap ring groove, h3 is the biting depth of the neck-breaking groove, h4 is the biting depth of the locking groove, L1 is the length of the biting section, L2 is the length of the neck-breaking groove sizing section, L3 is the length of the finishing section, L4 is the length of the withdrawal section, α is the biting angle, β is the withdrawal angle, h is the biting depth, L1-1 is the length of the bitten part of the straight ring groove, L1-2 is the length of the bitten part of the snap ring groove, L1-3 is the length of the bitten part of the neck-breaking groove, L1-4 is the length of the bitten part of the locking groove, M is the stationary die of the thread rolling die, and N is the moving die of the thread rolling die.

[0058] Advantages of the present invention: By applying the thread rolling die proposed by the present invention, multi-section special-shaped ring grooves such as the straight ring groove, snap ring groove, locking groove and neck-breaking groove with a certain inclination angle of the core rod of the blind rivet can be formed by thread rolling at one time, improving production efficiency.

[0059] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A multi-segment special-shaped ring groove blind rivet mandrel one-time thread rolling forming die, characterized in that: Including a primary thread rolling forming die, the primary thread rolling forming die includes a static thread rolling die M and a moving thread rolling die N. The static thread rolling die M and the moving thread rolling die N have the same structure. The static thread rolling die M and the moving thread rolling die N are used to process a multi-section special-shaped ring groove blind rivet core rod blank B into a target multi-section special-shaped ring groove blind rivet core rod A; The processing method of the primary thread rolling forming die includes the following steps: S1. Calculate the biting depth of each ring groove for processing the multi-section special-shaped ring groove blind rivet core rod blank B into the target multi-section special-shaped ring groove blind rivet core rod A; S2. Segment the primary thread rolling forming die according to each ring groove of the target multi-section special-shaped ring groove blind rivet core rod A, and set the length of the primary thread rolling die; S3. Calculate the parameters of each segment of the primary thread rolling forming die after segmentation; S4. Obtain the primary thread rolling forming die; In step S1, the target multi-section special-shaped ring groove blind rivet core rod A is successively provided with a straight ring groove (1), a snap ring groove (2), a neck-breaking groove (3), and a locking groove (4) from left to right, and the locking groove (4) has an inclination angle with respect to the radial direction of the rivet core rod of the target multi-section special-shaped ring groove blind rivet core rod A; In step S1, the calculation of the biting depth of each ring groove includes the following steps: S11. Overlap the models of the multi-section special-shaped ring groove blind rivet core rod blank B and the target multi-section special-shaped ring groove blind rivet core rod A; S12. Calculate the straight ring groove biting depth h1, the snap ring groove biting depth h2, the neck-breaking groove biting depth h3, and the locking groove biting depth h4 respectively according to the minimum outer diameter d1 of the rivet core rod straight ring groove, the minimum outer diameter d2 of the rivet core rod snap ring groove, the minimum outer diameter d3 of the rivet core rod neck-breaking groove, the minimum outer diameter d4 of the rivet core rod locking groove, the outer diameter D1 of the straight ring groove part of the rivet core rod blank, the outer diameter D2 of the snap ring groove part of the rivet core rod blank, the outer diameter D3 of the neck-breaking groove part of the rivet core rod blank, and the outer diameter D4 of the locking groove part of the rivet core rod blank; In step S2, segmenting the primary thread rolling forming die according to each ring groove of the target multi-section special-shaped ring groove blind rivet core rod A and setting the length of the primary thread rolling die includes the following steps: S21. Open convex edges at the corresponding positions of the primary thread rolling die according to the straight ring groove (1), the snap ring groove (2), the neck-breaking groove (3), and the locking groove (4); S22. Divide the convex edges of the primary thread rolling die corresponding to the straight ring groove (1), the snap ring groove (2), and the locking groove (4) into a biting section, a finishing section, and an exit section respectively, and divide the convex edge of the primary thread rolling die corresponding to the neck-breaking groove into a biting section, a sizing section, a finishing section, and an exit section; S23. Set the length of the primary thread rolling die as the sum of the biting section length L1, the neck-breaking groove sizing section length L2, the finishing section length L3, and the exit section length L4; In step S3, calculating the parameters of each segment of the primary thread rolling forming die after segmentation includes the following steps: S31. Calculate the parameters of the biting section of the primary thread rolling die; S32. Calculate the parameters of the exit section of the primary thread rolling die; S32. Set the neck-breaking groove sizing section length L2 of the primary thread rolling die ≥ πd2, and set the finishing section length L3 of the primary thread rolling die ≥ 4πd2; In step S31, the calculation of the parameters of the biting section of the primary thread rolling die includes the following steps: S311. Set that the biting angles α of each section, the biting depths h and the length L1 of the biting section satisfy tanα = h / L1, and set that the biting angles α of each section are the same, and the biting angle α takes the minimum value of the calculated biting angles of each section; S312. Set that the length L1-1 of the biting part of the straight ring groove is ≥ 2πd1, the length L1-2 of the biting part of the snap ring groove is ≥ 2πd2, the length L1-3 of the biting part of the neck-breaking groove is ≥ 2πd3, and the length L1-4 of the biting part of the locking groove is ≥ 2πd4; In step S32, the calculation of the parameters of the exit section of the primary thread rolling die includes the following steps: S321. Set that the exit angles β of each section, the biting depth h and the length L4 of the exit section satisfy tanβ = h / L4, and set that the exit angles β of each section take the minimum value of the calculated exit angles of each section; S322. Set that the length L4 of the exit section is ≥ πd2; The length of the biting part (5) of the straight ring groove thread rolling die is L1-1, the length of the biting part (6) of the snap ring groove thread rolling die is L1-2, the length of the biting part (7) of the neck-breaking groove thread rolling die is L1-3, the length of the biting part (8) of the locking groove thread rolling die is L1-4, the length of the sizing part (9) of the neck-breaking groove thread rolling die is L2, the length of the exit part (10) of the thread rolling die is L4, the length of the finishing section is L3, and the length of the clamping part (11) of the head of the rivet core rod is equal to the sum of L1-3, L2, L3 and L4, which is the length of the thread rolling die.

2. The one-time thread rolling forming die for the core rod of a multi-segment special-shaped ring groove blind rivet according to claim 1, characterized in that: The stationary die M of the thread rolling die includes a stationary die body, a biting part (5) of the straight ring groove thread rolling die, a biting part (6) of the snap ring groove thread rolling die, a biting part (7) of the neck-breaking groove thread rolling die, a biting part (8) of the locking groove thread rolling die, a sizing part (9) of the neck-breaking groove thread rolling die, an exit part (10) of the thread rolling die, and a clamping part (11) of the head of the rivet core rod. The biting part (5) of the straight ring groove thread rolling die, the biting part (6) of the snap ring groove thread rolling die, the biting part (7) of the neck-breaking groove thread rolling die, and the biting part (8) of the locking groove thread rolling die are sequentially arranged from bottom to top on the left side of the stationary die body. The clamping part (11) of the head of the rivet core rod is arranged above the stationary die body. The sizing part (9) of the neck-breaking groove thread rolling die is arranged in the middle of the stationary die body. The exit part (10) of the thread rolling die is arranged on the right side of the stationary die body.

3. A multi-segment special-shaped ring groove blind rivet shank one-time thread rolling forming die according to claim 1, characterized in that: The biting depth h1 of the straight ring groove = 0.5(d1 - D1), the biting depth h2 of the snap ring groove = 0.5(d2 - D2), the biting depth h3 of the neck-breaking groove = 0.5(d3 - D3), and the biting depth h4 of the locking groove = 0.5(d4 - D4).

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