A mold and mold system for producing a high-toughness weather-resistant torsion bar

Abstract

The application discloses a kind of high tough weatherable torsion bar production mould and mould system, including five sets of mould with unified installation interface, and the workpiece of light pole is sequentially processed to form the each shaft section and working part of high tough weatherable torsion bar.The innovation core is in the fifth mould, the fixed mould of this mould is equipped with a limit sleeve and the multi-petal mould placed in its converging cavity.The multi-petal mould is composed of several limit blocks, which can be radially gathered under the action of converging cavity wall under the pressure of punch, to accurately clamp the second shaft section of workpiece, and together with fixed seat, reset seat to form closed cavity to cold upset forming third working part.After forming, the punch returns, and the reset seat pushes the multi-petal mould to reset under the action of butterfly spring, so that its positioning space expands, thereby realizing the lossless and smooth demoulding of the formed workpiece.The application solves the technical problem of difficult demoulding of stepped shaft parts through multi-petal mould design, and has the advantages of high forming precision and high automation degree.

Description

Technical Field

[0001] This invention belongs to the field of high-strength, toughness and weather-resistant torsion bar production technology, specifically relating to a mold for producing high-strength, toughness and weather-resistant torsion bars and a mold system including the mold. Background Technology

[0002] Torsion bars, as a key power transmission component, are widely used in automotive seats, seat belts, suspensions, stabilizer bars, and various mechanical structures. They are typically multi-step shaft parts, consisting of working sections and shaft segments of varying diameters arranged axially. Traditional manufacturing methods for these parts usually involve multiple passes of hot forging, machining, and subsequent heat treatment, resulting in long process flows, low material utilization, high production costs, and potential interference with material fiber flow. To improve production efficiency and material utilization, the industry is increasingly adopting minimal or no-machining processes such as cold heading and cold extrusion to manufacture high-strength, tough, and weather-resistant torsion bar parts.

[0003] However, the unique geometry of high-strength, tough, and weather-resistant torsion bars, especially their stepped structure where the working section diameter is larger than that of adjacent shaft sections, presents significant challenges to mold design and automated production. For stepped shafts with large-diameter working sections at one or both ends, the formed protrusions after cold heading can hinder the workpiece from axially ejecting from the mold. To address this issue, traditional molds often require complex transverse parting mechanisms or wedge ejection devices, resulting in complex mold structures, large sizes, high manufacturing costs, low operational reliability, and inconvenient maintenance. Another solution is to use a composite mold that operates from both sides of the workpiece, which not only increases equipment investment but also slows down the production pace, hindering efficient automated continuous production.

[0004] Therefore, there is an urgent need in this field for a new type of mold that can achieve rapid and precise molding and smooth demolding of stepped high-strength and weather-resistant torsion bars without damaging the machined surface of the workpiece, while also having the advantages of compact structure, easy automation integration and low maintenance cost. Summary of the Invention

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution.

[0006] A mold for producing a high-strength, tough, and weather-resistant torsion bar is used to process a third working part at one end of a workpiece. After processing, the workpiece includes a second working part, a second shaft segment, and a third working part in sequence along the axial direction. The diameters of the second and third working parts are larger than those of the second shaft segment. The mold includes a fixed mold and a punching mold.

[0007] The fixed mold includes a fixed mold sleeve, a limiting sleeve, a multi-lobed mold, a fixing base, a reset base, and a reset elastic element. The limiting sleeve is fitted inside the fixed mold sleeve, dividing the internal cavity of the fixed mold sleeve into a convergence cavity and an assembly cavity; the inner diameter of the convergence cavity gradually decreases towards the assembly cavity. The multi-lobed mold is placed inside the convergence cavity and has a frustum-shaped structure adapted to the convergence cavity; the side of the convergence cavity has an opening for the punch to extend into, and a retaining edge is provided to restrict the multi-lobed mold from exiting. The multi-lobed mold includes several limiting blocks arranged around a center, the limiting blocks being connected by elastic connectors, and a positioning space for positioning the second shaft segment is provided in the middle of the multi-lobed mold.

[0008] A fixed seat, a reset seat, and a reset elastic element are placed within the assembly cavity. The reset seat has a third forming groove, and the fixed seat extends into the third forming groove. The limiting sleeve has a channel in the middle, and the reset seat has a top abutment extending into the channel. The reset elastic element provides a reset elastic force to the reset seat. The multi-lobed mold has a forming surface facing the channel, and the forming surface of the multi-lobed mold, the end face of the fixed seat, and the inner wall of the third forming groove together define a cavity for forming the third working part.

[0009] The positioning space is configured such that when the die applies pressure, the limiting block is drawn together towards the center by the converging action of the converging cavity, thereby reducing the positioning space to limit the second shaft segment; when the die disengages, the reset seat, under the action of the reset elastic element, pushes the multi-lobed die through the top abutment to restore the limiting block to its original position, and the inner diameter of the positioning space expands to allow the third working part to pass through.

[0010] Under the pressure of the punch, the multi-lobed die automatically contracts radially, precisely clamping the second shaft segment of the workpiece. This ensures the positional accuracy of the third working part during cold heading. Simultaneously, its forming surface, together with the fixed seat, forms a closed cavity, guaranteeing the shape and dimensions of the third working part. After machining, under the action of the reset system, the multi-lobed die automatically expands radially, making the inner diameter of its positioning space larger than the diameter of the third working part. This achieves smooth, scratch-free demolding of the formed workpiece, effectively protecting the surface quality of the workpiece and the die itself.

[0011] In a preferred embodiment of a mold for producing high-strength, tough, and weather-resistant torsion bars, the limiting sleeve has a sloping surface on one side for forming the convergence cavity, the inclination of which varies gradually, and the side of the multi-lobed mold is adapted to the sloping surface. This structure provides a smooth transition, disperses stress, reduces impact and wear between the multi-lobed mold and the limiting sleeve, and improves the mold's service life and operational stability.

[0012] In a preferred embodiment of a mold for producing high-strength, tough, and weather-resistant torsion bars, the fixed mold further includes a fixed ejector rod, and the fixed base has a through hole extending axially into which the fixed ejector rod extends. The ejector rod is used to eject the finished workpiece and also to handle the problem of accidental jamming.

[0013] In a preferred embodiment of a mold for producing high-strength, tough, and weather-resistant torsion bars, a wear-resistant sleeve is fitted onto the reset seat, and the portion of the third forming groove used for forming the third working part is located on the wear-resistant sleeve. By placing the part bearing the greatest friction and forming force on the wear-resistant sleeve, when this part wears down due to long-term use, only the wear-resistant sleeve needs to be replaced, significantly reducing mold maintenance costs and time, and improving the overall service life and economy of the mold.

[0014] As a preferred embodiment of a mold for producing high-strength, tough, and weather-resistant torsion bars, the reset elastic element includes several butterfly springs arranged in an alternating reverse pattern. The butterfly springs provide a large and stable elastic force within a limited installation space. This arrangement effectively counteracts the eccentric load on the springs themselves, ensuring uniform force distribution and smooth reset of the reset seat and multi-lobed mold. Furthermore, the butterfly springs have the advantages of high load-bearing capacity and long service life.

[0015] In a preferred embodiment of a mold for producing high-strength, tough, and weather-resistant torsion bars, the die includes a die base with a punch for applying pressure to the multi-lobed mold. The punch has a receiving groove on its end face for accommodating the second working part. The design of the receiving groove effectively prevents axial movement or radial displacement of the workpiece during processing, further ensuring the coaxiality between the third and second working parts and improving forming accuracy.

[0016] As a preferred embodiment of a mold for producing high-strength, tough, and weather-resistant torsion bars, the die base is provided with an ejector rod that extends to the bottom of the receiving groove. This allows the workpiece that may adhere to the punch receiving groove to be actively ejected during the die return stroke, thus avoiding production interruption or equipment damage caused by the workpiece being carried into the die side and ensuring the reliability of continuous production.

[0017] In a preferred embodiment of a mold for producing high-strength, tough, and weather-resistant torsion bars, a mating sleeve is fitted on the punch, and the receiving groove is located on the mating sleeve. When the receiving groove wears or becomes out of tolerance, only the lower-cost mating sleeve needs to be replaced, instead of replacing the entire expensive punch, significantly reducing maintenance costs and shortening downtime.

[0018] A mold system for machining workpieces into high-strength, tough, and weather-resistant torsion bars includes a first mold, a second mold, a third mold, a fourth mold, and a fifth mold. The first mold is used to machine a first shaft segment with a diameter smaller than the workpiece body at one end of the bare workpiece, forming a rod structure in which the workpiece sequentially includes the first shaft segment and the second shaft segment along the axial direction. The second mold is used to machine a preliminary machining section at the connection between the first shaft segment and the second shaft segment. The third mold is used to machine a first working section at the end of the first shaft segment, and simultaneously machine the preliminary machining section into a transition section. The fourth mold is used to machine the transition section into a second working section. The fifth mold is the aforementioned mold for producing high-strength, tough, and weather-resistant torsion bars, used to machine a third working section at the end of the second shaft segment away from the second working section.

[0019] The first, second, third, fourth, and fifth molds all include a punch and a fixed die, with each punch having the same punch mounting slot and each fixed die having the same fixed die mounting slot. Because the punch and fixed dies of each mold have the same mounting interface, they can be quickly and easily installed on the same stamping equipment or at different stations on a production line, achieving production flexibility, facilitating rapid die changes according to production plans, and improving equipment utilization and production organization flexibility.

[0020] Compared with the prior art, this application has the following beneficial technical effects:

[0021] 1. By utilizing the radial convergence and resetting of the multi-lobed mold, the problem of traditional molds requiring operation from both sides or the use of complex ejection mechanisms is solved, enabling workpieces to smoothly enter and exit the mold from a single direction, simplifying the operation process and improving the degree of automation.

[0022] 2. The clamping, forming and resetting functions are highly integrated into a compact fixed mold unit, avoiding complex external mechanisms, making the mold structure simple and compact, significantly reducing manufacturing costs, and facilitating installation and maintenance. Attached Figure Description

[0023] Figure 1 This is a structural diagram of a high-strength, tough, and weather-resistant torsion bar.

[0024] Figure 2 This is a flowchart illustrating the molding process of a high-strength, tough, and weather-resistant torsion bar.

[0025] Figure 3 This is a sectional view of the structure of each mold in the mold system.

[0026] Figure 4 This is a structural cross-sectional view of the fifth mold.

[0027] Figure 5 This is a structural sectional view of the fifth mold die.

[0028] Figure 6 This is a sectional view of the structure of the fixed mold sleeve and the limiting sleeve in the fifth mold.

[0029] Figure 7 This is a cross-sectional view of the multi-lobed mold structure.

[0030] Figure 8 This is a stereoscopic view of a multi-lobed model.

[0031] Figure 9 A sectional view of the structure of the fixed seat and the reset seat assembly.

[0032] Figure 10 This is an axial view of the reset seat.

[0033] The following is an explanation of the reference numerals in the attached figures:

[0034] 100. Fixed mold; 110. Fixed mold sleeve; 120. Limiting sleeve; 121. Gathering cavity; 122. Assembly cavity; 123. Channel; 130. Multi-lobed mold; 131. Limiting block; 132. Elastic connector; 133. Positioning space; 134. Forming surface; 140. Fixed seat; 150. Reset seat; 151. Top stop; 152. Third forming through groove; 153. Wear-resistant sleeve; 160. Reset elastic element; 170. Fixed ejector rod;

[0035] 200. Die; 210. Die base; 211. Punch; 212. Receiving groove; 220. Mating sleeve; 230. Ejector pin;

[0036] 300, First mold; 400, Second mold; 500, Third mold; 600, Fourth mold; 700, Fifth mold; 800, Fixed mold mounting slot; 810, Punch die mounting slot;

[0037] 900. High-strength, tough, and weather-resistant torsion bar; 901. First working part; 902. First shaft section; 903. Second working part; 904. Second shaft section; 905. Third working part. Detailed Implementation

[0038] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0039] In the following embodiments, the same or similar reference numerals denote the same or similar components or components having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0040] In the description of this invention, it should be understood that terms such as center, longitudinal, transverse, length, width, thickness, upper, lower, front, rear, left, right, vertical, horizontal, top, bottom, inner, outer, clockwise, counterclockwise, etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing and simplifying the description of this invention; therefore, they should not be construed as limiting this invention. Furthermore, terms such as first, second, etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features shown. In the description of this invention, unless otherwise expressly specified and limited, terms such as installation, connection, linking, etc., should be interpreted broadly, and those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0041] refer to Figure 1 and Figure 2 A mold system for producing a high-strength, tough, and weather-resistant torsion bar 900 includes a first mold 300, a second mold, a third mold 500, a fourth mold 600, and a fifth mold 700. The mold system is used to process a bare bar workpiece into a high-strength, tough, and weather-resistant torsion bar 900 comprising, in sequence along the axial direction, a first working part 901, a first shaft segment 902, a second working part 903, a second shaft segment 904, and a third working part 905, wherein the diameters of the second working part 903 and the third working part 905 are larger than that of the second shaft segment 904.

[0042] The first mold 300 is used to machine a first shaft segment 902 with a diameter smaller than the workpiece body at one end of the workpiece; the second mold is used to machine a preliminary machining section at the connection between the first shaft segment 902 and the second shaft segment 904; the third mold 500 is used to machine a first working section at the end of the first shaft segment 902, and simultaneously machine the preliminary machining section into a transition section; the fourth mold 600 is used to machine the transition section into a second working section; and the fifth mold 700 is used to machine a third working section 905 at the end of the second shaft segment 904 away from the second working section 903. The second working section 903 and the third working section 905 have a staggered structure. The mold system described in this application can quickly machine this staggered structure, resulting in higher processing efficiency compared to traditional processes that require multiple cold heading.

[0043] The first mold 300, second mold, third mold 500, fourth mold 600, and fifth mold 700 all include a punch 200 and a fixed mold 100, with each punch 200 having the same punch mounting groove 810 and each fixed mold 100 having the same fixed mold mounting groove 800. By adopting a unified mounting interface structure, each mold can be quickly and conveniently installed at different stations on the same stamping equipment or production line, facilitating rapid mold changes according to production plans, thereby effectively improving equipment utilization and the flexibility of production organization. Since the structure of the first to fourth molds 600 is not the core content of this application, their specific construction will not be described in detail here.

[0044] refer to Figures 3 to 10 The fifth mold 700 includes a fixed mold 100 and a punch 200 (hereinafter, "punch 200" specifically refers to the punch 200 of the fifth mold 700). The fixed mold 100 includes a fixed mold sleeve 110, a limiting sleeve 120, a multi-lobed mold 130, a fixing seat 140, a reset seat 150, and a reset elastic element 160. The limiting sleeve 120 is assembled inside the fixed mold sleeve 110, dividing the internal cavity of the fixed mold sleeve 110 into a converging cavity 121 and an assembly cavity 122; the inner diameter of the converging cavity 121 gradually decreases towards the assembly cavity 122. The multi-lobed mold 130 is placed inside the converging cavity 121 and is a frustum-shaped structure adapted to the converging cavity 121. The side of the converging cavity 121 has an opening for the punch 200 to extend into, and a retaining edge is provided to restrict the multi-lobed mold 130 from disengaging. The multi-lobed mold 130 includes a plurality of limiting blocks 131 arranged around the center. The limiting blocks 131 are connected by elastic connectors 132, and the multi-lobed mold 130 has a positioning space 133 in the middle for positioning the second shaft segment 904.

[0045] The fixed seat 140, the reset seat 150, and the reset elastic element 160 are placed in the assembly cavity 122. The reset seat 150 has a third molding groove 152, and the fixed seat 140 extends into the third molding groove 152. The limiting sleeve 120 has a channel 123 in the middle, and the reset seat 150 has a top abutment 151 extending into the channel 123. The reset elastic element 160 is used to provide a reset elastic force for the reset seat 150. The multi-lobed mold 130 has a molding surface 134 facing the channel 123. The molding surface 134 of the multi-lobed mold 130, the end face of the fixed seat 140, and the inner wall of the third molding groove 152 together define a cavity for molding the third working part 905.

[0046] The positioning space 133 is configured such that when the die 200 applies pressure, the limiting block 131 is drawn together by the converging action of the converging cavity 121, causing the positioning space 133 to shrink to limit the second shaft segment 904; when the die 200 disengages, the reset seat 150, under the action of the reset elastic member 160, pushes the multi-lobed die 130 through the top abutment 151 to return the limiting block 131 to its original position, and the inner diameter of the positioning space 133 expands to allow the third working part 905 to pass through.

[0047] Based on the above structure, the multi-lobed mold 130 can automatically radially contract under the pressure of the punch 200, precisely clamping the second shaft segment 904 of the workpiece, thereby ensuring the positional accuracy of the third working part 905 during cold heading. Simultaneously, its forming surface 134, together with components such as the fixed seat 140, forms a closed cavity, effectively guaranteeing the shape and dimensional accuracy of the third working part 905. After processing, under the action of the reset system, the multi-lobed mold 130 automatically expands radially, making the inner diameter of the positioning space 133 larger than the diameter of the third working part 905, thereby achieving smooth, scratch-free demolding of the formed workpiece, which helps protect the surface quality of the workpiece and extends the service life of the mold.

[0048] In a preferred embodiment, the limiting sleeve 120 has a sloping surface on one side forming the receiving cavity 121, the inclination of which varies gradually, and the side of the multi-lobed mold 130 is adapted to the sloping surface. This structure provides a smooth transition, disperses stress, reduces impact and wear between the multi-lobed mold 130 and the limiting sleeve 120, and improves the service life and operational stability of the mold. The fixed mold 100 also includes a fixed ejector rod 170, and the fixed base 140 has a through hole extending axially for the fixed ejector rod 170 to enter. The ejector rod is used to eject the finished workpiece and also handles the problem of accidental jamming.

[0049] A wear-resistant sleeve 153 is fitted onto the reset seat 150, and the portion of the third forming groove 152 used for forming the third working part 905 is located on the wear-resistant sleeve 153. By placing the part bearing the greatest friction and forming force on the wear-resistant sleeve 153, when this part wears out due to long-term use, only the wear-resistant sleeve 153 needs to be replaced, significantly reducing mold maintenance costs and time, and improving the overall service life and economy of the mold. The reset elastic element 160 includes several butterfly springs, which are arranged in an alternating reverse pattern. The butterfly springs provide a large and stable elastic force within a limited installation space. This arrangement effectively counteracts the uneven load on the springs themselves, ensuring uniform force distribution and smooth reset of the reset seat 150 and the multi-lobed mold 130. Simultaneously, the butterfly springs have the advantages of high load-bearing capacity and long service life.

[0050] The die 200 includes a die base 210, on which a punch 211 is provided for applying pressure to the multi-lobed die 130. The end face of the punch 211 has a receiving groove 212 for accommodating the second working part 903. The design of the receiving groove 212 effectively prevents axial movement or radial displacement of the workpiece during processing, further ensuring the coaxiality between the third working part 905 and the second working part 903, and improving forming accuracy. The die base 210 is provided with an ejector rod 230, which extends to the bottom of the receiving groove 212. This allows the punch 200 to actively eject any workpieces that may adhere to the receiving groove 212 of the punch 211 during its return stroke, preventing production interruptions or equipment damage caused by workpieces being carried into the die 200 and ensuring the reliability of continuous production.

[0051] The punch 211 is fitted with a mating sleeve 220, and the receiving groove 212 is located on the mating sleeve 220. When the receiving groove 212 is worn or out of tolerance, only the lower-cost mating sleeve 220 needs to be replaced, instead of replacing the entire expensive punch 211, which significantly reduces maintenance costs and shortens downtime.

[0052] The scope of protection of this invention includes, but is not limited to, the above embodiments. The scope of protection of this invention is defined by the claims. Any substitutions, modifications, or improvements to this technology that are easily conceived by those skilled in the art fall within the scope of protection of this invention.

Claims

1. A mold for producing high-strength, tough, and weather-resistant torsion bars, characterized in that, The mold comprises a fixed mold (100) and a punch mold (200); The fixed mold (100) comprises: A fixed mold sleeve (110); A limiting sleeve (120) is assembled in the fixed mold sleeve (110), and the internal cavity of the fixed mold sleeve (110) is divided into a converging cavity (121) and an assembly cavity (122); the inner diameter of the converging cavity (121) gradually decreases towards the assembly cavity (122); A multi-petal mold (130) is arranged in the converging cavity (121) and has a circular truncated cone structure matched with the converging cavity (121); the side surface of the converging cavity (121) is provided with an opening for the punch mold (200) to extend into and is provided with a retaining edge to limit the multi-petal mold (130) from coming out; the multi-petal mold (130) comprises a plurality of limiting blocks (131) arranged around a center ring, the limiting blocks (131) are connected by elastic connecting members (132), and the middle of the multi-petal mold (130) is provided with a positioning space (133) for positioning the second shaft section (904); A fixing seat (140), a reset seat (150) and a reset elastic member (160) are arranged in the assembly cavity (122); the reset seat (150) is provided with a third forming through slot (152) therein, and the fixing seat (140) extends into the third forming through slot (152); the limiting sleeve (120) is provided with a passage (123) in the middle, the reset seat (150) has a top abutting portion (151) extending into the passage (123), and the reset elastic member (160) is used to provide a reset elastic force for the reset seat (150); the multi-petal mold (130) has a forming surface (134) facing the passage (123), and the forming surface (134) of the multi-petal mold (130), the end surface of the fixing seat (140) and the inner wall of the third forming through slot (152) jointly define a forming cavity for forming the third working part (905); The positioning space (133) is configured to: when the punch mold (200) applies pressure, the limiting blocks (131) are gathered in the middle under the converging action of the converging cavity (121), so that the positioning space (133) is reduced to limit the second shaft section (904); when the punch mold (200) is separated, the reset seat (150) pushes the multi-petal mold (130) through the top abutting portion (151) under the action of the reset elastic member (160) to restore the limiting blocks (131) to the original position, and the inner diameter of the positioning space (133) is expanded to allow the third working part (905) to pass through. The limiting sleeve (120) is used for forming a side of the converging cavity (121) with a slope surface, the slope of the slope surface changes in a gradient, and the side surface of the multi-petal die (130) is adapted to the slope surface; the reset seat (150) is equipped with a wear-resistant sleeve (153), and the third forming groove (152) is used for forming part of the third working part (905) on the wear-resistant sleeve (153).

2. The mold for producing a high-toughness weather-resistant torsion bar according to claim 1, characterized by The fixed die (100) further comprises a fixed ejector rod (170), and the fixed seat (140) is provided with a through hole penetrating in the axial direction and used for extending the fixed ejector rod (170) into the through hole.

3. The mold for producing a high-toughness weather-resistant torsion bar according to claim 1, characterized in that, The reset elastic member (160) comprises a plurality of butterfly springs, and the plurality of butterfly springs are arranged in an alternating reverse form.

4. The mold for producing a high-toughness weather-resistant torsion bar according to claim 1, wherein The punch (200) comprises a punch seat (210), and the punch seat (210) is provided with a punch (211) used for pressing the multi-petal die (130), and an end surface of the punch (211) is provided with an accommodation groove (212) used for accommodating the second working part (903).

5. The mold for producing a high-toughness weather-resistant torsion bar according to claim 4, wherein The punch seat (210) is provided with a punch ejector rod (230), and the punch ejector rod (230) penetrates to the bottom of the accommodation groove (212).

6. The mold for producing a high-toughness weather-resistant torsion bar according to claim 4, wherein The punch (211) is equipped with a matching sleeve (220), and the accommodation groove (212) is located on the matching sleeve (220).

7. A mold system for machining a workpiece into a high-toughness weather-resistant torsion bar (900), characterized by, Comprise: A first die (300) is used for machining a first shaft section (902) with a smaller diameter than a body of a workpiece on one end of the workpiece, so that the workpiece forms a rod body structure sequentially comprising the first shaft section (902) and a second shaft section (904) in the axial direction; A second die is used for machining a rough machining section at a connection between the first shaft section (902) and the second shaft section (904); A third die (500) is used for machining a first working section at an end of the first shaft section (902), and machining the rough machining section into a transition section; A fourth die (600) is used for machining the transition section into a second working section; A fifth die (700) is a die for producing a high-toughness weather-resistant torsion rod according to any one of claims 1 to 6, and is used for machining a third working section (905) at an end of the second shaft section (904) away from the second working part (903); The first die (300), the second die, the third die (500), the fourth die (600), and the fifth die (700) all comprise a punch (200) and a fixed die (100), and each of the punches (200) has the same punch mounting groove (810), and each of the fixed dies (100) has the same fixed die mounting groove (800).

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