Forming manufacturing process and device for hexagonal head bolts

Abstract

The application discloses a hexagonal ball head bolt forming manufacturing process and device, which is applied to the hexagonal ball head bolt forming technical field and has the technical scheme as follows: a feeding assembly, a fixed-length cutting assembly, a multi-station synchronous conveying assembly and six groups of cold heading dies which are fixedly arranged on a cold heading machine along a conveying direction are sequentially arranged; the multi-station synchronous conveying assembly is used for realizing synchronous conveying of the wire between the fixed-length cutting assembly and each group of cold heading dies; the cold heading die comprises a first die used for performing a shrinkage chamfer process, a second die used for performing a first two-end rod shrinkage process, a third die used for performing a pre-heading composite rod shrinkage process, a fourth die used for performing a head heading forming process, a fifth die used for performing a hexagonal push-cut forming process and a sixth die used for performing a ball head die forming process; the hexagonal ball head bolt forming manufacturing process and device have the technical effect that the forming precision is ensured, the forming efficiency of the bolt is improved, and the overall equipment cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of hexagonal ball head bolt forming technology, and particularly to a hexagonal ball head bolt forming manufacturing process and apparatus. Background Technology

[0002] As attached Figure 1 The hexagonal ball head bolt shown includes a chamfered portion, a reduced shank portion, a hexagonal head, and a ball head. As a key functional fastener in the automotive tailgate system, it is widely used in the connection and assembly of the electric tailgate strut. Its core function is to achieve the hinged fixation between the electric strut and the tailgate sheet metal structure. It needs to provide stable support and load-bearing capacity for the entire process of electric opening and closing of the tailgate, while also ensuring the flexible rotation of the hinged part within a set angle range. Therefore, the forming accuracy of this hexagonal ball head bolt directly determines the operational stability, smoothness of operation, and service life of the automotive tailgate system.

[0003] Currently, the industrial production of hexagonal ball head bolts primarily employs CNC machining or conventional multi-station cold heading processes. Among these, CNC machining... The cutting process requires multiple cutting steps to complete the shank diameter reduction, hexagonal head forming, and ball head surface forming. This not only results in high processing costs but also completely severs the internal metal fiber flow lines, significantly weakening the bolt's fatigue strength and structural mechanical properties. Furthermore, CNC cutting has poor production efficiency, making it difficult to meet the mass production requirements of automotive hexagonal ball head bolts for high volume, low cost, and high reliability. Existing conventional cold heading processes, for irregularly shaped bolts as shown in the attached diagram, which include a hexagonal structure at one end, a ball head structure at the other, and require multi-segment diameter reduction of the shank, generally suffer from unreasonable process layout: if a single large deformation reduction is used, it easily exceeds the cold heading deformation limit of the metal material, leading to defects such as cracking, folding, and forming instability in the shank. If multiple independent diameter reduction stations are used, it increases equipment investment and reduces forming efficiency. Additionally, existing processes suffer from rapid mold wear and low product yield. Therefore, it is necessary to improve the existing hexagonal ball head bolt forming manufacturing process to ensure forming accuracy while increasing bolt forming efficiency and reducing overall equipment costs. Summary of the Invention

[0004] The primary objective of this invention is to provide a manufacturing process for forming hexagonal ball head bolts, which has the advantages of ensuring forming accuracy while improving bolt forming efficiency and reducing overall equipment costs.

[0005] The above-mentioned technical objective of this invention is achieved through the following technical solution: a manufacturing process for forming hexagonal ball head bolts, comprising: S1. Chamfering process: The cut wire blank is chamfered at the end, and the coaxiality of the wire blank is straightened at the same time to establish the forming benchmark. S2, First two-end shrinking process: The two ends of the wire blank are simultaneously subjected to the first shrinking forming, and the deformation of a single shrinking is controlled within the allowable cold heading deformation limit of the material to obtain the semi-finished product of the pre-shrinked rod at both ends. S3, Pre-upsetting composite rod reduction process: Simultaneously complete the pre-upsetting of the head and the second reduction forming of the rod at both ends of the semi-finished product, and control the dimensional accuracy of the rod and the continuous direction of the metal fiber flow lines; S4. Head upsetting process: The head after pre-upsetting is finally upset to complete the basic outline of the bolt head, and the cylindricity and coaxiality of the shank are finely adjusted. S5, Hexagonal push-cut forming process: The semi-finished bolt is axially pushed by the punch die, and the pre-formed head of the semi-finished product is pushed into the hexagonal cutting edge cavity of the main mold to remove excess edge material and form a standard hexagonal head structure. S6. Ball head molding process: First, the non-formed part of the bolt is wrapped by a three-piece floating molding structure, and then the ball head structure is precision cold-forged by axial extrusion to obtain a hexagonal ball head bolt blank.

[0006] The present invention is further configured such that: in the first two-end shrinkage process of S2, the shrinkage deformation of the single-end rod is controlled at 30%-40%; in the pre-upsetting composite shrinkage process of S3, the shrinkage deformation of the single-end rod is controlled at 15%-25%, and the total deformation of the two shrinkage processes does not exceed 60%.

[0007] The present invention is further configured such that: in the S3 pre-forging composite shrinking rod process, the main mold is used to position and clamp the semi-finished rod part, and through the coordinated action of the punch and the main mold ejector pin, the pre-forging of the head metal aggregate and the axial extrusion shrinking of the rod parts at both ends are completed simultaneously within a single cold forging stroke.

[0008] The present invention is further configured such that: in the S5 hexagonal push-cut forming process, a progressive push-cut die with a shearing angle of 3°-5° is used, the push-cut process is continuous shearing forming, and after the push-cut is completed, the six sides of the hexagonal head are finely finished through the forming cavity. After forming, the tolerance of the side dimension of the hexagonal head is controlled within ±0.03mm, and the perpendicularity tolerance of the hexagonal surface to the axis of the rod is not greater than 0.02mm.

[0009] The present invention is further configured such that: in the S6 ball head precision forming process, 80% of the volume of ball head metal aggregate is pre-formed through a pre-forming cavity, and then the ball head surface is finally formed through a floating closed mirror cavity. After forming, the contour tolerance of the ball head surface is controlled within ±0.02mm, and the surface roughness Ra≤0.4μm.

[0010] The second objective of this invention is to provide a hexagonal ball head bolt forming and manufacturing apparatus, which has the advantages of ensuring forming accuracy while improving bolt forming efficiency and reducing overall equipment costs.

[0011] The above-mentioned technical objective of the present invention is achieved through the following technical solution: a hexagonal ball head bolt forming and manufacturing apparatus, used for a hexagonal ball head bolt forming and manufacturing process as described in any of the above technical solutions, comprising a feeding assembly, a fixed-length cutting assembly, a multi-station synchronous conveying assembly arranged in sequence, and six sets of cold heading dies fixedly arranged in sequence along the conveying direction on a cold heading machine. The multi-station synchronous conveying assembly is used to realize the synchronous transfer of wire between the fixed-length cutting assembly and each set of cold heading dies. The cold heading dies include: a first die for performing a chamfering process, a second die for performing a first two-end shrinking process, a third die for performing a pre-upsetting composite shrinking process, a fourth die for performing a head upsetting process, a fifth die for performing a hexagonal push-cut forming process, and a sixth die for performing a ball head closing forming process.

[0012] The present invention is further configured such that: the second mold includes a second main mold and a second punch that are arranged opposite to each other, and both the second main mold and the second punch are provided with a diameter reduction forming cavity; the second main mold ejector pin and the second punch ejector pin are respectively fixedly connected in the diameter reduction forming cavity along the axial direction of the wire; when the mold is closed, the second main mold ejector pin and the second punch ejector pin simultaneously complete the symmetrical diameter reduction forming of the rods at both ends of the wire.

[0013] The present invention is further configured such that: the third mold includes a third main mold and a third punch die arranged opposite to each other; the third main mold has a rod positioning cavity, a bidirectional diameter reduction forming cavity and a third main mold ejector pin; the third punch die has a head pre-upsetting forming cavity; and the head pre-upsetting and the secondary diameter reduction forming of the rods at both ends are completed simultaneously within a single mold closing stroke. The sixth mold includes a sixth punch, a sixth main mold, a three-piece mold assembly, a drive cone sleeve, and a nitrogen spring; The three-piece mold assembly includes three mold pieces evenly distributed circumferentially. The outer wall of the three mold pieces is provided with a driving slope. In the mold-opening state, the three mold pieces open radially, and in the mold-closed state, they radially close to form a closed cavity that wraps around the bolt rod. The driving cone sleeve is fitted on the outside of the three-piece mold, and its inner wall is provided with a cone surface that matches the driving inclined surface of the three-piece mold, which is used to drive the three-piece mold to radially close when the mold is closed. The nitrogen spring is fixed inside the sixth main mold, and its output end is connected to the drive cone sleeve. It is used to apply axial elastic force to the drive cone sleeve and transmit continuous radial tightening force to the three mold pieces through the cone surface fit. The end of the sixth die is provided with a ball head forming cavity, which is used to axially compress the end of the bolt when the die is closed, so as to complete the precision forming of the ball head structure.

[0014] The present invention is further configured such that: the fourth mold includes a fourth main mold and a fourth punch mold arranged opposite to each other; The fourth main mold includes an embedded fourth main mold core and a fourth main mold ejector pin that penetrates the fourth main mold core. The fourth main mold core has a rod shaping cavity and a head shaping cavity connected in sequence along the axial direction. The inner diameter of the rod shaping cavity matches the size of the finished bolt rod to perform final shaping of the coaxiality and cylindricity of the bolt rod. The fourth die includes an embedded fourth die core and a fourth die ejector pin that penetrates the fourth die core. When the die is closed, the fourth die core and the inner wall of the fourth main die core surround each other to form an open forming cavity, which allows the hexagonal head metal material to be compressed and deformed, achieving flash-free final upsetting.

[0015] The present invention is further configured such that: the fifth mold includes a fifth main mold and a fifth punch die arranged coaxially opposite to each other; The fifth die is equipped with an axial pushing mechanism for pushing the semi-finished bolts to move axially when the die is closed. The fifth main mold is provided with a hexagonal cutting edge cavity that matches the size of the finished hexagonal head. The entrance of the hexagonal cutting edge cavity is provided with a cutting edge with a shearing angle of 3°-5°, which is used to cut off excess edge material when the semi-finished product is pushed into the cavity to complete the hexagonal head forming.

[0016] In summary, the present invention has the following beneficial effects: 1. By dividing the rod shrinking process into two steps and setting the shrinkage deformation of the single-end rod in the first two-end shrinking process to 30%-40%, and the shrinkage deformation of the single-end rod in the pre-upsetting composite shrinking process to 15%-25%, the single-time shrinkage deformation is controlled within the allowable cold heading limit of the material. This solves the defects of easy cracking and folding of the rod in the conventional cold heading process, greatly improving the forming yield. At the same time, by completing the head pre-upsetting and the second-time shrinkage of the rod at both ends simultaneously in the pre-upsetting composite shrinking process within a single cold heading stroke, the number of independent processes is reduced to improve forming efficiency, while ensuring the coaxiality of the forming of the rod and the head. This ensures the dimensional accuracy of the subsequent hexagonal push cutting and ball head forming. Compared with the traditional CNC cutting process, the internal metal fiber flow lines of the bolt are completely preserved, which greatly improves the fatigue strength and structural mechanical properties of the bolt. 2. This invention eliminates the original mold-closing and pushing action by using a push-type hexagonal cutting structure in the fifth mold. The edge material is removed through the hexagonal cutting cavity built into the main mold, which fundamentally avoids defects such as head overload, burrs, and corner collapse caused by mold-closing and pushing. This significantly improves the forming accuracy and batch consistency of the hexagonal head, while reducing mold wear and extending mold life. Through the three-piece floating mold-closing structure of the sixth mold, combined with the continuous tightening force of the nitrogen spring, it achieves both closed precision forming of the ball head and facilitates product entry and exit through the large opening when the mold is opened. At the same time, it eliminates the expansion and deformation of the rod during the forming process of the ball head, completely preserving the metal fiber flow lines of the product. This significantly improves the fatigue strength and forming accuracy of the bolt, eliminating the need for subsequent additional machining processes and further reducing mass production costs. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the forming and manufacturing process of the hexagonal ball head bolt in Example 1; Figure 2 This is a schematic diagram of the molding and manufacturing apparatus of Example 2; Figure 3 This is a schematic diagram of the structure of the second mold in Example 2; Figure 4 This is a schematic diagram of the structure of the third mold in Example 2; Figure 5 This is a schematic diagram of the structure of the fourth mold in Example 2; Figure 6 This is a structural schematic diagram of the fifth mold in Example 2; Figure 7 This is a schematic diagram of the sixth mold in Example 2.

[0018] Reference numerals: 1. First mold; 2. Second mold; 21. Second main mold; 22. Second punch; 23. Reduction forming cavity; 24. Second main mold ejector pin; 25. Second punch ejector pin; 3. Third mold; 31. Third main mold; 32. Third punch; 33. Rod positioning cavity; 34. Bidirectional reduction forming cavity; 35. Third main mold ejector pin; 36. Head pre-upsetting forming cavity; 4. Fourth mold; 41. Fourth main mold; 42. Fourth punch; 43. Fourth main mold core ; 44. Fourth main mold ejector pin; 45. Rod shaping cavity; 46. Head shaping cavity; 47. Fourth punch core; 48. Fourth punch ejector pin; 49. Hexagonal final upset cavity; 5. Fifth mold; 51. Fifth main mold; 52. Fifth punch; 53. Hexagonal trimmed cavity; 6. Sixth mold; 61. Sixth main mold; 62. Sixth punch; 63. Three-piece mold assembly; 64. Drive cone sleeve; 65. Nitrogen spring; 66. Ball head forming cavity; 7. Hexagonal ball head bolt. Detailed Implementation

[0019] The present invention will be further described in detail below with reference to the accompanying drawings.

[0020] Example 1: refer to Figure 1 A manufacturing process for forming hexagonal ball head bolts, comprising: S1. Chamfering process: The cut wire blank is chamfered at the end, and the coaxiality of the wire blank is straightened at the same time to establish the forming benchmark. S2, First two-end shrinking process: The two ends of the wire blank are simultaneously subjected to the first shrinking forming, and the deformation of a single shrinking is controlled within the allowable cold heading deformation limit of the material to obtain the semi-finished product of the pre-shrinked rod at both ends. S3, Pre-upsetting composite rod reduction process: Simultaneously complete the pre-upsetting of the head and the second reduction forming of the rod at both ends of the semi-finished product, and control the dimensional accuracy of the rod and the continuous direction of the metal fiber flow lines; S4. Head upsetting process: The head after pre-upsetting is finally upset to complete the basic outline of the bolt head, and the cylindricity and coaxiality of the shank are finely adjusted. S5, Hexagonal push-cut forming process: The semi-finished bolt is axially pushed by the punch die, and the pre-formed head of the semi-finished product is pushed into the hexagonal cutting edge cavity of the main mold to remove excess edge material and form a standard hexagonal head structure. S6. Ball head molding process: First, the non-formed part of the bolt is wrapped by a three-piece floating molding structure, and then the ball head structure is precision cold-forged by axial extrusion to obtain the hexagonal ball head bolt blank.

[0021] Specifically, in the S2 initial double-end shrinkage process, the shrinkage deformation of a single-end rod is controlled at 30%-40%; in the S3 pre-forging composite shrinkage process, the shrinkage deformation of a single-end rod is controlled at 15%-25%, and the total deformation of the two shrinkage processes does not exceed 60%. This achieves the goal of controlling the single shrinkage deformation within the allowable cold forging limit of the material, thereby solving the defects such as easy cracking and folding of the rod in the conventional cold forging process and greatly improving the forming yield.

[0022] Specifically, in the S3 pre-forging composite shrinking rod process, the main mold is used to position and clamp the semi-finished rod. Through the coordinated action of the punch and the main mold ejector pin, the pre-forging of the head metal aggregate and the axial extrusion shrinking of the rod at both ends are completed simultaneously within a single cold forging stroke. This reduces the number of independent processes to improve forming efficiency while ensuring the coaxiality of the rod and the head forming, thereby ensuring the dimensional accuracy of the subsequent hexagonal push cutting and ball head forming.

[0023] Specifically, in the S5 hexagonal push-cut forming process, the semi-finished bolt is axially pushed by the die, and the pre-formed head of the semi-finished product is pushed into the hexagonal cutting edge cavity of the main mold. The cutting edge of the hexagonal cutting edge cavity of the main mold is set with a shearing angle of 3°-5°. The push-cut process is a continuous shearing forming. After removing the excess edge material, a standard hexagonal head structure is formed to achieve high-precision forming of the hexagonal head without burrs or collapsed corners. This ensures the perpendicularity of the hexagonal side dimension tolerance to the axis of the relative rod, while reducing the forming load and extending the service life of the mold. As a result, the side dimension tolerance of the formed hexagonal head is controlled within ±0.03mm, and the perpendicularity tolerance of the hexagonal surface to the axis of the rod is not greater than 0.02mm.

[0024] Specifically, in the S6 ball head precision forming process, the semi-finished bolt is first sent into the open three-piece mold cavity. When the mold is closed, the three pieces of the mold are radially closed by the conical surface, which wraps the non-formed part of the bolt and restricts its expansion and deformation. Then, the bolt end is axially squeezed by the punch, and the final forming of the ball head is completed in the closed cavity. After forming, the profile tolerance of the ball head surface is controlled within ±0.02mm, and the surface roughness Ra≤0.4μm.

[0025] Example 2: refer to Figure 2 A hexagonal ball head bolt forming and manufacturing apparatus is used for a hexagonal ball head bolt forming and manufacturing process as shown in Embodiment 1 above. It includes a feeding assembly, a fixed-length cutting assembly, a multi-station synchronous conveying assembly arranged sequentially, and six sets of cold heading dies fixed sequentially on a cold heading machine along the conveying direction. The multi-station synchronous conveying assembly is used to realize the synchronous transfer of wire between the fixed-length cutting assembly and each set of cold heading dies. The cold heading dies include: a first die 1 for performing a chamfering process, a second die 2 for performing a first two-end shrinking process, a third die 3 for performing a pre-upsetting composite shrinking process, a fourth die 4 for performing a head upsetting process, a fifth die 5 for performing a hexagonal push-cut forming process, and a sixth die 6 for performing a ball head closing forming process.

[0026] refer to Figure 3 Specifically, the second mold 2 includes a second main mold 21 and a second punch 22 arranged opposite to each other. Both the second main mold 21 and the second punch 22 are provided with a diameter reduction forming cavity 23. The second main mold 21 and the second punch 22 are respectively fixedly connected to the diameter reduction forming cavity 23 with a second main mold ejector pin 24 and a second punch ejector pin 25 arranged along the axial direction of the wire. When the mold is closed, the second main mold ejector pin 24 and the second punch ejector pin 25 simultaneously complete the symmetrical diameter reduction forming of the rods at both ends of the wire. The second mold 2 ensures the dimensional consistency of the diameter reduction of the rods at both ends by setting a symmetrical diameter reduction structure.

[0027] refer to Figure 4Specifically, the third mold 3 includes a third main mold 31 and a third punch 32 arranged opposite to each other. The third main mold 31 has a rod positioning cavity 33, a bidirectional diameter reduction forming cavity 34 and a third main mold ejector pin 35. The punch has a head pre-upsetting forming cavity 36. The head pre-upsetting and the secondary diameter reduction forming of the rods at both ends are completed simultaneously within a single mold closing stroke, thereby reducing the forming process, reducing the equipment usage cost and forming efficiency.

[0028] refer to Figure 5 Specifically, the fourth mold 4 includes a fourth main mold 41 and a fourth punch 42 that are arranged opposite to each other; The fourth main mold 41 includes an embedded fourth main mold core 43 and a fourth main mold ejector pin 44 that penetrates the fourth main mold core 43. The fourth main mold core 43 is provided with a rod shaping cavity 45 and a head shaping cavity 46 connected along the axial direction. The inner diameter of the rod shaping cavity 45 matches the size of the finished bolt rod to perform final shaping of the coaxiality and cylindricity of the bolt rod. The fourth die 42 includes an embedded fourth die core 47 and a fourth die ejector pin 48 penetrating the fourth die core 47. When the mold is closed, the fourth die core 47 and the inner wall of the cavity of the fourth main die core 43 close together to form an open forming cavity 49, which allows the hexagonal head metal material to be compressed and deformed, achieving flash-free final upsetting. When the mold is closed, the fourth punch 42 moves towards the fourth main mold 41 along with the slide block of the cold heading machine. The semi-finished bolt is first positioned in the fourth main mold core 43, the bolt shank enters the shank shaping cavity 45, and the pre-formed head enters the head shaping cavity 46 to complete the reference positioning. During the mold closing stroke, the shank shaping cavity 45 simultaneously performs fine straightening and adjustment on the coaxiality and cylindricity of the bolt shank. When the mold is closed, the fourth punch core 47 and the mold closing end face of the fourth main mold core 43 close together to form an open forming cavity 49, which allows the hexagonal head metal material to be compressed and deformed to complete the flashless final upsetting of the hexagonal head. Finally, after the mold is opened, the bolt is passed through the fourth main mold core 43. The four main mold ejector pins 44 eject the semi-finished product, which has completed the head shaping and rod finishing, from the main mold cavity. This achieves simultaneous completion of the flash-free final upsetting of the hexagonal head and the coaxiality and cylindricity finishing of the bolt rod within a single station and a single mold closing stroke. This reduces independent molding processes, improves production efficiency, and ensures the coaxiality of the bolt head and rod, providing a precise positioning reference for the subsequent hexagonal push-cutting process. At the same time, the closed molding structure completely preserves the metal fiber streamline of the head, improving the torsional strength and structural stability of the hexagonal head, and eliminating the need for subsequent deburring processing, further reducing processing costs.

[0029] refer to Figure 6 Specifically, the fifth mold 5 includes a fifth main mold 51 and a fifth punch 52 arranged coaxially opposite to each other; The fifth die 52 is provided with an axial pushing mechanism for pushing the semi-finished bolts to move axially when the die is closed. The fifth main mold 51 is provided with a hexagonal cutting edge cavity 53 that matches the size of the finished hexagonal head. The entrance of the hexagonal cutting edge cavity 53 is provided with a cutting edge with a shearing angle of 3°-5°, which is used to cut off excess edge material when the semi-finished product is pushed into the cavity to complete the hexagonal head forming. When the mold is closed, the axial pushing mechanism of the fifth punch 52 pushes the bolt semi-finished product to the fifth main mold 51. The pre-formed head of the semi-finished product is pushed into the hexagonal cutting edge cavity 53. The cutting edge continuously removes the excess edge material to complete the forming of the hexagonal head. There is no mold closing action at this station. The cutting edge is formed only by axial pushing, which avoids the problems of uneven load and burrs caused by mold closing and pushing, and ensures the forming accuracy of the hexagonal head.

[0030] refer to Figure 7 Specifically, the sixth mold 6 includes a sixth punch 62, a sixth main mold 61, a three-piece mold closing assembly 63, a drive cone sleeve 64, and a nitrogen spring 65; The three-piece mold assembly 63 includes three mold pieces evenly distributed along the circumference. The outer wall of the three mold pieces is provided with a driving slope. In the mold-opening state, the three mold pieces open radially, and in the mold-closed state, they close radially to form a closed cavity that wraps around the bolt rod. The drive cone sleeve 64 is fitted on the outside of the three-piece mold, and its inner wall is provided with a cone surface that matches the drive inclined surface of the three-piece mold, which is used to drive the three-piece mold to radially close when the mold is closed. Nitrogen spring 65 is fixed inside the sixth main mold 61. Its output end is connected to the drive cone sleeve 64 and is used to apply axial elastic force to the drive cone sleeve 64. Through the cone surface fit, it transmits continuous radial tightening force to the three mold pieces. The end of the sixth die 62 is provided with a ball head forming cavity 66, which is used to axially press the end of the bolt when the die is closed to complete the precision forming of the ball head structure. The ball head forming cavity 66 is provided with a mirror polishing layer. When the mold is closed, the sixth punch 62 moves downward with the slide of the cold heading machine, first pushing the drive cone sleeve 64 to move axially. Through the cone surface cooperation, the three-piece mold is radially closed, completely enclosing the non-formed rod part of the bolt. The nitrogen spring 65 transmits a continuous radial tightening force to the three-piece mold through the drive cone sleeve 64 to ensure that the rod part does not expand or deform during the forming process. The sixth punch 62 continues to move downward, axially pressing the end of the bolt, and completing the precision forming of the ball head in the closed cavity formed by the three-piece mold and the sixth punch 62. When the mold is opened, the sixth punch 62 moves upward, the nitrogen spring 65 pushes the drive cone sleeve 64 to reset, the three-piece mold opens radially, and the finished bolt is ejected from the cavity through the ejection mechanism, completing the mold forming of the ball head.

[0031] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make inventive modifications to this embodiment as needed, but as long as they are within the scope of the claims of the present invention, they are protected by patent law.

Claims

1. A manufacturing process for forming hexagonal ball head bolts, characterized in that, include: S1. Chamfering process: The cut wire blank is chamfered at the end, and the coaxiality of the wire blank is straightened at the same time to establish the forming benchmark. S2, First two-end shrinking process: The two ends of the wire blank are simultaneously subjected to the first shrinking forming, and the deformation of a single shrinking is controlled within the allowable cold heading deformation limit of the material to obtain the semi-finished product of the pre-shrinked rod at both ends. S3, Pre-upsetting composite rod reduction process: Simultaneously complete the pre-upsetting of the head and the second reduction forming of the rod at both ends of the semi-finished product, and control the dimensional accuracy of the rod and the continuous direction of the metal fiber flow lines; S4. Head upsetting process: The head after pre-upsetting is finally upset to complete the basic outline of the bolt head, and the cylindricity and coaxiality of the shank are finely adjusted. S5, Hexagonal push-cut forming process: The semi-finished bolt is axially pushed by the punch die, and the pre-formed head of the semi-finished product is pushed into the hexagonal cutting edge cavity of the main mold to remove excess edge material and form a standard hexagonal head structure. S6. Ball head molding process: First, the non-formed part of the bolt is wrapped by a three-piece floating molding structure, and then the ball head structure is precision cold-forged by axial extrusion to obtain a hexagonal ball head bolt blank.

2. The manufacturing process for forming a hexagonal ball head bolt according to claim 1, characterized in that, In the S2 initial two-end shrinkage process, the shrinkage deformation of a single-end rod is controlled at 30%-40%; in the S3 pre-upsetting composite shrinkage process, the shrinkage deformation of a single-end rod is controlled at 15%-25%, and the total deformation of the two shrinkage processes does not exceed 60%.

3. The manufacturing process for forming a hexagonal ball head bolt according to claim 1, characterized in that, In the S3 pre-forging composite shrinking rod process, the main mold is used to position and clamp the semi-finished rod. Through the coordinated action of the punch and the main mold ejector pin, the pre-forging of the head metal aggregate and the axial extrusion shrinking of the rod at both ends are completed simultaneously within a single cold forging stroke.

4. The manufacturing process for forming a hexagonal ball head bolt according to claim 1, characterized in that, In the S5 hexagonal push-cut forming process, a progressive push-cut die with a shearing angle of 3°-5° is used. The push-cut process is a continuous shearing forming. After the push-cut is completed, the six sides of the hexagonal head are finely finished through the forming cavity. After forming, the tolerance of the side dimension of the hexagonal head is controlled within ±0.03mm, and the perpendicularity tolerance of the hexagonal face to the axis of the rod is not greater than 0.02mm.

5. The manufacturing process for forming a hexagonal ball head bolt according to claim 1, characterized in that, In the S6 ball head molding process, the semi-finished bolt is first fed into the open three-piece mold cavity. When the mold is closed, the three pieces are driven to close radially by the conical surface, which wraps the non-formed part of the bolt and restricts its expansion and deformation. Then, the bolt end is axially squeezed by the die, and the final forming of the ball head is completed in the closed cavity. After forming, the profile tolerance of the ball head surface is controlled within ±0.02mm, and the surface roughness Ra≤0.4μm.

6. A hexagonal ball head bolt forming and manufacturing apparatus, used in a hexagonal ball head bolt forming and manufacturing process as described in any one of claims 1-5, comprising a feeding assembly, a fixed-length cutting assembly, a multi-station synchronous conveying assembly arranged in sequence, and six sets of cold heading dies fixedly arranged in sequence along the conveying direction on a cold heading machine, wherein the multi-station synchronous conveying assembly is used to realize the synchronous transfer of wire between the fixed-length cutting assembly and each set of cold heading dies; characterized in that, The cold heading mold includes: a first mold (1) for performing the chamfering process, a second mold (2) for performing the first two-end heading process, a third mold (3) for performing the pre-heading compound heading process, a fourth mold (4) for performing the head heading process, a fifth mold (5) for performing the hexagonal push-cut forming process, and a sixth mold (6) for performing the ball head closing forming process.

7. The hexagonal ball head bolt forming and manufacturing apparatus according to claim 6, characterized in that, The second mold (2) includes a second main mold (21) and a second punch (22) arranged opposite to each other. Both the second main mold (21) and the second punch (22) are provided with a diameter reduction forming cavity (23). The second main mold (21) and the second punch (22) are respectively fixedly connected with a second main mold ejector pin (24) and a second punch ejector pin (25) arranged along the axial direction of the wire in the diameter reduction forming cavity (23). When the mold is closed, the second main mold ejector pin (24) and the second punch ejector pin (25) simultaneously complete the symmetrical diameter reduction forming of the rods at both ends of the wire.

8. The hexagonal ball head bolt forming and manufacturing apparatus according to claim 6, characterized in that, The third mold (3) includes a third main mold (31) and a third punch (32) arranged opposite to each other. The third main mold (31) has a rod positioning cavity (33), a bidirectional diameter reduction forming cavity (34) and a third main mold ejector pin (35). The third punch (32) has a head pre-upsetting forming cavity (36). The head pre-upsetting and the secondary diameter reduction forming of the rods at both ends are completed simultaneously within a single mold closing stroke. The sixth mold (6) includes a sixth punch (62), a sixth main mold (61), a three-piece mold assembly (63), a drive cone sleeve (64), and a nitrogen spring (65); The three-piece mold assembly (63) includes three mold pieces evenly distributed along the circumference. The outer wall of the three mold pieces is provided with a driving slope. In the mold-opening state, the three mold pieces open radially, and in the mold-closed state, they close radially to form a closed cavity that wraps around the bolt rod. The driving cone sleeve (64) is sleeved on the outside of the three-piece mold, and its inner wall is provided with a cone surface that matches the driving inclined surface of the three-piece mold, which is used to drive the three-piece mold to radially close when the mold is closed. The nitrogen spring (65) is fixed inside the sixth main mold (61), and its output end is connected to the drive cone sleeve (64) to apply axial elastic force to the drive cone sleeve (64) and transmit continuous radial tightening force to the three mold pieces through the cone surface fit. The end of the sixth die (62) is provided with a ball head forming cavity (66) for axially pressing the end of the bolt when the die is closed, so as to complete the precision forming of the ball head structure.

9. The hexagonal ball head bolt forming and manufacturing apparatus according to claim 6, characterized in that, The fourth mold (4) includes a fourth main mold (41) and a fourth punch (42) arranged opposite to each other; The fourth main mold (41) includes an embedded fourth main mold core (43) and a fourth main mold ejector pin (44) that passes through the fourth main mold core (43). The fourth main mold core (43) has a rod shaping cavity (45) and a head shaping cavity (46) connected in sequence along the axial direction. The inner diameter of the rod shaping cavity (45) matches the size of the finished bolt rod to perform final shaping of the coaxiality and cylindricity of the bolt rod. The fourth die (42) includes an embedded fourth die core (47) and a fourth die ejector pin (48) that passes through the fourth die core (47). When the die is closed, the fourth die core (47) and the inner wall of the cavity of the fourth main die core (43) enclose each other to form an open forming cavity (49), which allows the hexagonal head metal material to be compressed and deformed, so as to achieve flash-free final upsetting.

10. The hexagonal ball head bolt forming and manufacturing apparatus according to claim 6, characterized in that, The fifth mold (5) includes a fifth main mold (51) and a fifth punch (52) arranged coaxially opposite each other; The fifth die (52) is provided with an axial pushing mechanism for pushing the semi-finished bolts to move axially when the die is closed. The fifth main mold (51) is provided with a hexagonal cutting edge cavity (53) that matches the size of the finished hexagonal head. The entrance of the hexagonal cutting edge cavity (53) is provided with a cutting edge with a shearing angle of 3°-5°, which is used to cut off excess edge material when the semi-finished product is pushed into the cavity to complete the hexagonal head forming.

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