A non-standard tooth profile insert and its molding device and method

Abstract

This invention provides a non-standard toothed insert and its forming apparatus and method, relating to the field of precision plastic forming technology for metal parts. The insert is a one-piece metal part, including a head with a non-standard toothed structure and a thin rod. The toothed structure is integrally formed by cold forging and upsetting, resulting in a complete metal flow line. The forming apparatus includes six sets of molds matched in sequence: a forming mold, a rod-shrinking mold, an upsetting and punching composite mold, a finishing mold, a toothed final forging mold, and a trimming mold. The composite mold achieves punching followed by upsetting through a stepped arrangement of a central punch and an upsetting punch. The final forging mold adopts a split toothed mold core. The forming method includes six corresponding cold forging processes. Through step-by-step forming, hole finishing, high-pressure final forging, and trimming, a high-precision insert is finally obtained. This invention achieves high-quality, high-efficiency, near-net-shape forming of complex toothed structures, resulting in high product strength, high material utilization, and suitability for mass production.

Description

Technical Field

[0001] This invention relates to the field of precision plastic forming technology for metal parts, specifically to a non-standard toothed insert with high mechanical properties, a dedicated multi-process cold forming apparatus for manufacturing the insert, and a forming method thereof. Background Technology

[0002] In the automotive, aerospace, and high-end tooling industries, non-standard toothed inserts serve as crucial functional connectors or transmission components, with increasingly stringent performance requirements. Traditional manufacturing of such parts primarily employs machining (such as milling and gear shaping) or powder metallurgy. Machining methods suffer from drawbacks such as low material utilization, cutting that disrupts metal fibers, stress concentration at the tooth root, and poor fatigue strength, while also exhibiting low production efficiency. Although powder metallurgy can form complex shapes, the density and mechanical properties of the parts are typically lower than forgings, and the high cost of molds and stringent requirements for raw materials further complicate the process.

[0003] In recent years, cold forging (cold heading) has been widely used in the manufacture of standard fasteners and simple irregular-shaped parts due to its high material utilization, excellent mechanical properties, and high production efficiency. However, for inserts with complex structures such as non-standard teeth, deep holes, and slender rods, traditional single-station cold heading technology is difficult to form. If a few steps are forced into forming, it will result in severe stress on the mold, short mold life, and incomplete filling and poor precision of the parts. Therefore, there is an urgent need for a dedicated process, device, and method for complex non-standard toothed inserts that can accurately form them step by step, balancing performance and efficiency. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a non-standard toothed insert, whose tooth shape is integrally formed by cold forging and upsetting process, with complete metal flow lines and excellent performance; at the same time, it provides a set of dedicated, sequentially matched multi-process forming equipment and methods to achieve efficient, precise and stable production of the insert.

[0005] This invention provides the following technical solution: A non-standard toothed insert is a one-piece metal part, including a head and a rod. The outer periphery of the head is provided with a non-standard toothed structure for transmitting torque or preventing rotation. The diameter of the rod is smaller than the diameter of the head. The insert has an inner hole at its axis. The inner hole is a smooth hole or a threaded hole and penetrates the head. The non-standard toothed structure is a straight tooth, helical tooth, or involute tooth formed one-piece by cold forging and upsetting process, and the metal flow lines of the tooth are continuously distributed along the tooth profile.

[0006] An apparatus for forming the non-standard toothed insert includes six sets of molds arranged sequentially and structurally matched: a forming mold, a shrinking mold, an upsetting and punching composite mold, a finishing mold, a toothed final forging mold, and a trimming mold.

[0007] Furthermore, the forming die includes a first upper die punch and a first lower die cavity; the first lower die cavity is a precision cylindrical blind hole that matches the target outer diameter of the blank, used to radially constrain and micro-upset the cylindrical blank placed therein, forming a regular first preform.

[0008] The structure of the forming die provides a precise initial reference for the entire process. By eliminating the fluctuation of the blank size through "radial constraint and end face micro upsetting", a first preform with a regular shape is obtained. This is the basis for the accumulation of accuracy in all subsequent processes and ensures production stability.

[0009] Furthermore, the rod-shrinking die includes a second upper die punch and a third lower die; the second lower die is provided with a guide hole and a rod-forming hole, the guide hole is slidably fitted with the outer diameter of the first preform, the diameter of the rod-forming hole is smaller than the diameter of the guide hole, and the two are connected by a tapered inlet; the second upper die punch acts on the end face of the first preform, forcing its material to flow into the rod-forming hole to form a slender rod.

[0010] The shrinking die, guided by a tapered inlet and constrained by a rod forming hole, achieves efficient and controllable positive extrusion forming of the rod material, optimizes metal flow, reduces forming force, and obtains good rod surface quality and dimensional accuracy.

[0011] Furthermore, the upsetting and punching composite die includes a composite upper die and a third lower die; the composite upper die has a coaxially nested center punch and an upsetting punch, wherein the working end of the center punch slightly protrudes from the end face of the upsetting punch; the third lower die is provided with a clearance hole for accommodating the rod and an upsetting cavity for head forming; during operation, the protruding center punch first contacts the blank head and punches out the center guide hole, and then the upsetting punch upsets the blank head with the existing center hole. This 'punching first, then upsetting' sequence creates a channel for material to flow towards the center before large radial flow occurs in the head material, which helps reduce the deformation resistance of subsequent upsetting and also effectively prevents cracking in the hole edge area due to excessive stretching during upsetting, thus improving the quality of the pre-formed hole.

[0012] The upsetting and punching composite die, through its structural design of a 'protruding center punch end,' achieves a 'punching first, upsetting later' sequence. Pre-forming a central channel before the material undergoes large radial upsetting deformation at the head facilitates material flow towards the center during subsequent upsetting, reduces deformation resistance, and effectively prevents cracking in the hole edge area due to excessive stretching during upsetting. This improves the quality of the pre-formed hole and lays a solid foundation for subsequent finishing processes.

[0013] Furthermore, the finishing die includes a finishing punch and a fourth lower die; the working section diameter of the finishing punch is consistent with the final inner diameter of the insert, and its front end is provided with an inlet cone angle; the fourth lower die is provided with a positioning cavity that matches the shape of the blank; the finishing punch is pressed through the guide hole in an interference fit, causing it to undergo plastic deformation to achieve the target size and accuracy.

[0014] The finishing die structure uses plastic deformation via "interference fitting" to calibrate and smooth the pre-formed holes. This method not only calibrates the inner hole dimensions to a high precision (e.g., ±0.03mm), but also significantly reduces the surface roughness of the hole walls, achieving a grinding-like effect and providing a high-performance fit reference for the product.

[0015] Furthermore, the toothed final forging die includes a fifth upper die punch and a fifth lower die; the fifth lower die has a closed final forging cavity that is completely consistent with the target tooth shape and contour of the non-standard toothed insert head; the end face shape of the fifth upper die punch matches the pre-formed shape of the blank head; during operation, the blank head material plastically flows within the closed final forging cavity under high pressure, completely filling the tooth shape and integrally forming the final tooth shape. Preferably, the fifth lower die adopts a split structure, including a toothed die core and a die sleeve, the toothed portion of the final forging cavity is machined on the toothed die core, which facilitates machining, heat treatment, and replacement after wear.

[0016] The structure of the toothed final forging die, especially the "closed final forging cavity" and the "split toothed die core," has a dual effect: the closed cavity ensures that the tooth profile is fully formed under high pressure, resulting in high material utilization; while the further defined split die core design makes it possible to process toothed cavities with high hardness and high precision, and only the die core needs to be replaced after wear, significantly reducing the manufacturing and maintenance costs of the die and increasing its lifespan.

[0017] Furthermore, the trimming die includes an upper trimming die and a lower trimming die; the cutting edge contour of the upper trimming die matches the tooth root contour of the non-standard tooth structure; the lower trimming die is provided with a positioning cavity that matches the shape of the workpiece after final forging; the upper trimming die moves downward to remove the annular flash formed on the outer periphery of the workpiece tooth due to final forging.

[0018] The structure of the trimming die, through the matching design of the cutting edge and the tooth root contour, can accurately and efficiently remove burrs, and the cut is neat without damaging the already formed precision tooth shape, thus ensuring the final appearance and size of the product.

[0019] A method for forming a non-standard toothed insert using the above-mentioned device includes the following sequential steps: S1. Shaping: The cylindrical metal blank is placed into the first lower mold cavity of the shaping mold, and the blank is radially constrained and micro-upset at the end face by the first upper mold punch to obtain a first preform with a regular outer diameter; S2. Strong rod section: The first preform is placed into the rod shrinking mold with its rod section facing the rod forming hole; the material of the first preform is forced to flow into the rod forming hole through the conical inlet by the second upper die punch to form a slender rod section, thus obtaining the second preform; S3. Upsetting and pre-forming holes: The second preform is placed into the third lower die of the upsetting and punching compound die; the compound upper die moves down, and its upsetting punch first upsets the head of the blank, and then or simultaneously, its central punch moves to punch a guide hole in the center of the upset head to obtain the third preform; S4. Inner hole finishing: The third preform is placed into the fourth lower die of the finishing die; the finishing punch is driven to squeeze through the guide hole in an interference manner, so that the hole wall undergoes plastic deformation to form an inner hole with accurate dimensions and smooth surface, thus obtaining the fourth preform; S5. Toothed final forging: The fourth preform is placed into the closed final forging cavity of the fifth lower die of the toothed final forging die; high pressure is applied by the fifth upper die punch, so that the material at the head of the billet flows plastically in the closed cavity, completely filling the toothed die cavity, and a non-standard toothed structure is precisely forged in one go to obtain the fifth preform with flash; S6. Trimming: The fifth preform is placed into the lower trimming die of the trimming die; the upper trimming die moves downward, and its cutting edge cuts off the annular flash around the tooth shape to obtain the final non-standard tooth insert.

[0020] Thus, the six-step method scientifically decomposes the total deformation amount, following the logic of "basic shaping, rod forming, head upsetting and pre-drilling holes, hole finishing, tooth profile final forging, and cleaning", achieving the gradual and precise near-net-shape forming of complex non-standard tooth profile inserts. The process is reasonable and takes into account both quality and efficiency.

[0021] Furthermore, in step S4, the tolerance of the inner hole size after finishing is controlled within ±0.03mm, and the surface roughness Ra value is not greater than 1.6μm; In step S5, the unit pressure of the final forging of the tooth profile shall not be less than 1500 MPa to ensure that the corners of the tooth profile are fully filled. Before steps S2, S3, and S5, the preform needs to be sprayed or dipped with lubricant. All steps are completed at room temperature or when the billet preheating temperature is below the recrystallization temperature, which falls under the category of cold forging or warm forging. Steps S1 to S6 can be performed continuously on a multi-station cold forming machine or a sequentially arranged press unit to achieve automated production.

[0022] Thus, the optimization and limitation of the above key process parameters have the overall effect of ensuring that the method can not only achieve forming, but also stably and efficiently produce high-performance, highly consistent, and high-quality products by limiting a series of specific process conditions such as "optimized timing of punching and upsetting", "internal hole accuracy and roughness", "high-pressure final forging", "lubrication", "cold forming conditions" and "automated continuous production", thereby improving the operability and industrial value of the method.

[0023] The beneficial effects of this invention are: 1. Superior product performance: The tooth profile is integrally formed through high-pressure cold forging and upsetting process, with metal flow lines completely surrounding the tooth profile, eliminating the fiber cutting problem caused by machining, significantly improving the bending strength, torsional strength and fatigue resistance of the tooth, and the inner hole is finished to obtain high precision and low roughness, improving the fit quality; 2. Collaborative Innovation of Process and Equipment: The proposed six-step method of "shaping, rod reduction, upsetting and punching, finishing, final forging and trimming" scientifically decomposes the total deformation, reducing the deformation resistance of single process and the load on the mold. The six sets of special mold designs that are perfectly matched with it ensure the precise connection and stable realization of each process. In particular, the optimized combination of punching and upsetting processes in the composite mold and the split toothed mold core design have collaboratively solved the industry problem of punching quality and mold life. 3. High production efficiency and low cost: The process flow is reasonable and suitable for automated continuous production. The cycle time is fast and the material utilization rate is over 90%, which is far superior to machining. The mold adopts optimized design such as split and insert, and the maintenance and replacement cost is low. 4. Stable and consistent product quality: Closed-loop final forging and precision guiding ensure product dimensional accuracy and shape consistency, making it particularly suitable for mass production with high requirements in industrial manufacturing. Attached Figure Description

[0024] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 This is a top view of the finished non-standard toothed insert of the present invention; Figure 2 This is a schematic diagram of the structure of the first preform of the present invention; Figure 3 This is a schematic diagram of the structure of the second preform of the present invention; Figure 4 This is a schematic diagram of the structure of the third preform of the present invention; Figure 5 This is a schematic diagram of the structure of the fourth preform of the present invention; Figure 6 This is a schematic diagram of the structure of the fifth preform of the present invention; Figure 7 This is a schematic diagram of the structure of the finished insert of the present invention; Figure 8 This is a schematic diagram of the forming process of the forming mold in the forming device of the present invention; Figure 9 This is a schematic diagram of the forming process of the shrinkage mold in the forming device of the present invention; Figure 10 This is a schematic diagram of the upsetting and punching composite die forming process in the forming device of the present invention. Figure 11 This is a schematic diagram of the finishing mold forming process in the forming apparatus of the present invention; Figure 12 This is a schematic diagram of the forming process of the tooth-shaped final forging die in the forming device of the present invention; Figure 13 This is a schematic diagram of the forming process of the edge-cutting die in the forming device of the present invention.

[0025] In the diagram: 1. Head; 101. Non-standard toothed structure; 2. Rod; 3. Inner hole; 5. First preform; 6. Second preform; 7. Third preform; 8. Fourth preform; 9. Fifth preform; 10. Finished insert; 11. Shaping die; 12. Rod reduction die; 13. Upsetting and punching compound die; 14. Finishing die; 15. Toothed final forging die; 16. Trimming die; 111. First upper die punch; 112. First lower die cavity; 12 1. Second upper die punch; 122. Second lower die; 123. Guide hole; 124. Rod forming hole; 131. Compound upper die; 1311. Upsetting punch; 1312. Center punch; 132. Third lower die; 1321. Clearance hole; 1322. Upsetting cavity; 141. Finishing punch; 142. Fourth lower die; 151. Fifth upper die punch; 152. Fifth lower die; 161. Trimming upper die; 162. Trimming lower die. Detailed Implementation

[0026] Example 1: Non-standard toothed insert product This embodiment provides a high-strength non-standard toothed insert formed by cold forging and upsetting process.

[0027] like Figure 1-7 As shown, the non-standard toothed insert provided by this invention is a one-piece metal structure, mainly comprising a head 1 and a rod 2. Non-standard toothed structures 101 for transmitting torque or achieving anti-rotation function are distributed on the outer circumference of the head 1. An inner hole 3 penetrating the head 1 is provided at the axial position; this inner hole 3 can be machined into a smooth hole or a threaded hole according to the final assembly requirements. The diameter of the rod 2 is smaller than the diameter of the head 1, forming a stepped shaft structure.

[0028] The core feature of this insert lies in its integral, non-standard tooth profile 101, which is not obtained through machining but rather through a one-time precision forming process using cold forging and upsetting, detailed below. This manufacturing method ensures that the metal flow lines in the tooth region are continuously and completely distributed along the tooth profile 101 without being cut. This continuous metal fiber structure endows the insert with superior mechanical properties: compared to similar parts made using machining methods (such as milling and shaping), its tooth root bending fatigue strength is increased by more than 30%, its shear resistance is significantly enhanced, and its tooth surface load-bearing capacity is also higher. Furthermore, the one-piece molding avoids potential failure points caused by welding or assembly, greatly improving reliability. This insert is particularly suitable for applications with stringent requirements for torque load and fatigue life, such as synchronizer bushings in automotive transmissions, output shafts of high-end power tools, and actuator connectors in aerospace applications.

[0029] Example 2: Molding apparatus and method like Figure 1-13 As shown, this embodiment provides a special device and its molding method for manufacturing the non-standard toothed insert described in Embodiment 1.

[0030] The forming device consists of six sets of corresponding molds arranged in sequence and with matching structures, including a forming mold 11, a shrinking mold 12, an upsetting and punching composite mold 13, a finishing mold 14, a toothed final forging mold 15, and a trimming mold 16. The forming method corresponds to six core steps, such as... Figure 2 As shown.

[0031] Detailed description of the device structure: 1. Shaping die 11: includes a first upper die punch 111 and a first lower die cavity 112. The first lower die cavity 112 is a precision cylindrical blind hole that matches the target outer diameter of the blank, used to radially constrain and micro-upset the cylindrical blank placed therein.

[0032] 2. Rod forming die 12: includes a second upper die punch 121 and a third lower die 132. The second lower die 122 is provided with a guide hole 123 and a rod forming hole 124 with a smaller diameter. The two holes are smoothly transitioned through a tapered inlet to achieve positive extrusion flow of material.

[0033] 3. Upsetting and punching compound die 13: This is a key compound workstation in this device. For example... Figure 3As shown, it includes a composite upper die 131 and a third lower die 132. The composite upper die 131 has a coaxially nested center punch 1312 and an upsetting punch 1311, wherein the working end of the center punch 1312 slightly protrudes from the working end face of the upsetting punch 1311. The third lower die 132 is provided with a clearance hole 1321 and an upsetting cavity 1322. This structure ensures that when the composite upper die 131 moves downward, the center punch 1312 can preferentially contact the head of the blank and punch out the guide hole. Subsequently, the upsetting punch 1311 upsets the blank head with the existing center hole. This "punching first, then upsetting" sequence is beneficial for the material to flow towards the center hole during upsetting, reducing deformation resistance, and preventing cracking of the hole edge area due to excessive stretching during upsetting, thereby obtaining a high-quality pre-formed hole. 4. Finishing Die 14: Includes a finishing punch 141 and a fourth lower die 142. The working section diameter of the finishing punch 141 is consistent with the target diameter of the final inner hole 3 of the insert, and a guide cone is provided at the front end. The fourth lower die 142 is provided with a precise positioning cavity.

[0034] 5. Tooth-shaped final forging die 15: This is the core forming station of this device. It includes the fifth upper die punch 151 and the fifth lower die 152. The fifth lower die 152 has a closed final forging cavity that perfectly matches the final tooth shape and contour of the product. To achieve high-precision tooth machining and long service life, the fifth lower die 152 preferably adopts a split structure. Figure 4 As shown, it consists of an independent high-hardness toothed mold core and a mold sleeve for fastening. The toothed mold core can be made of cemented carbide and the toothed cavity is machined by precision grinding. After wear, the mold core can be directly replaced, which is economical and efficient.

[0035] 6. Trimming die 16: includes upper trimming die 161 and lower trimming die 162. The cutting edge contour of the upper trimming die 161 is precisely matched with the tooth root contour of the product tooth shape, and the lower trimming die 162 is provided with a positioning die that matches the shape of the workpiece.

[0036] Molding method steps: S1. Shaping: The cylindrical metal blank obtained by shearing the wire rod is placed into the shaping die 11. The first upper die punch 111 presses down to obtain the first preform 5 with a precise outer diameter, which establishes a benchmark for subsequent processes.

[0037] S2. Strengthening Rod Section 2: The first preform 5 is placed into the rod shrinking mold 12. The second upper die punch 121 presses down, forcing the material to flow into the rod forming hole 124 through the tapered inlet, forming the slender rod section 2, and obtaining the second preform 6. Lubricant needs to be sprayed before this step.

[0038] S3. Punching and Upsetting: The second preform 6 is placed into the upsetting and punching compound die 13. The compound upper die 131 moves downward, and the central punch 1312 first contacts the head of the blank and punches a guide hole therein. Subsequently, the upsetting punch 1311 upsets the head 1 with the punched guide hole to obtain the third preform 7. This process sequence of "punching first, then upsetting" is the key to obtaining high-quality preform holes.

[0039] S4. Inner Hole 3 Finishing: Place the third preform 7 into the finishing die 14. Drive the finishing punch 141 to press through the guide hole 123 with an interference fit (interference amount approximately 0.05-0.1mm), causing plastic deformation and smoothing of the hole wall. The dimensional tolerance of the inner hole 3 is controlled within ±0.03mm, and the surface roughness Ra≤1.6μm, resulting in the fourth preform 8. This precision inner hole 3 serves as the accurate positioning reference for the next tooth profile final forging.

[0040] S5. Toothed Final Forging: This is the core process. The fourth preform 8 is placed into the closed cavity of the toothed final forging die 15. The fifth upper die punch 151 applies a high pressure of not less than 1500 MPa, causing the material of the head 1 to flow plastically within the closed space, completely filling the cavity of the toothed die core, and precisely forging the tooth shape in one go to obtain the fifth preform 9 with flash. Sufficient lubrication is required before this step.

[0041] S6. Trimming: Place the fifth preform 9 into the trimming mold 16. The upper trimming mold 161 moves downward to precisely cut off the annular flash around the toothed outer periphery, obtaining the final finished insert 10.

[0042] The entire process (S1 to S6) can be completed continuously and automatically on a multi-station cold forming machine. All deformations are carried out at room temperature or low-temperature preheating (below the metal recrystallization temperature), which falls under the category of precision cold forging. This device and method work together to achieve efficient, high-quality, and stable production of non-standard toothed inserts.

[0043] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A non-standard toothed insert, characterized in that, It is a one-piece metal part, including a head and a rod; the outer periphery of the head is provided with a non-standard tooth structure for transmitting torque or preventing rotation, the diameter of the rod is smaller than the diameter of the head, the insert has an inner hole at its axis, the inner hole is a smooth hole or a threaded hole, and penetrates the head, the non-standard tooth structure is a straight tooth, helical tooth or involute tooth formed by cold forging and upsetting process, and the metal flow lines of the tooth are continuously distributed along the tooth profile.

2. An apparatus for molding the non-standard toothed insert of claim 1, characterized in that, It includes six sets of molds arranged in sequence and with matching structures: forming mold, shrinking mold, upsetting and punching compound mold, finishing mold, toothed final forging mold and trimming mold.

3. The non-standard toothed insert forming device according to claim 2, characterized in that, The forming die includes a first upper die punch and a first lower die cavity; the first lower die cavity is a precision cylindrical blind hole that matches the target outer diameter of the blank, used to radially constrain and micro-upset the cylindrical blank placed therein, forming a regular first preform.

4. The non-standard toothed insert forming device according to claim 2, characterized in that, The rod-shrinking die includes a second upper die punch and a second lower die; the second lower die is provided with a guide hole and a rod-forming hole, the guide hole is slidably fitted with the outer diameter of the first preform, the diameter of the rod-forming hole is smaller than the diameter of the guide hole, and the two are connected by a tapered inlet; the second upper die punch acts on the end face of the first preform, forcing its material to flow into the rod-forming hole to form a slender rod.

5. The non-standard toothed insert forming device according to claim 2, characterized in that, The upsetting and punching compound die includes a compound upper die and a third lower die; the compound upper die has a coaxially nested upsetting punch and a center punch; the third lower die is provided with a clearance hole for accommodating the rod and an upsetting cavity for head forming; during operation, the center punch first contacts the blank head and punches out the center guide hole, and then the upsetting punch upsets the punched blank head, with the end of the center punch slightly protruding from the working end face of the upsetting punch to ensure that the punching action occurs first.

6. The non-standard toothed insert forming device according to claim 2, characterized in that, The finishing die includes a finishing punch and a fourth lower die; the working section diameter of the finishing punch is consistent with the final inner diameter of the insert, and its front end is provided with an inlet cone angle; the fourth lower die is provided with a positioning cavity that matches the shape of the blank; the finishing punch is pressed through the guide hole in an interference fit, causing it to undergo plastic deformation to achieve the target size and accuracy.

7. The non-standard toothed insert forming device according to claim 2, characterized in that, The toothed final forging die includes a fifth upper die punch and a fifth lower die; the fifth lower die has a closed final forging cavity that is completely consistent with the target tooth shape and contour of the non-standard toothed insert head; the end face shape of the fifth upper die punch matches the pre-formed shape of the blank head; during operation, the blank head material plastically flows in the closed final forging cavity under high pressure, completely filling the tooth shape and integrally forming the final tooth shape, and the fifth lower die adopts a split structure, including a toothed die core and a die sleeve, and the toothed part of the final forging cavity is machined on the toothed die core.

8. The non-standard toothed insert forming device according to claim 2, characterized in that, The trimming die includes an upper trimming die and a lower trimming die; the cutting edge contour of the upper trimming die matches the tooth root contour of the non-standard tooth structure; the lower trimming die is provided with a positioning cavity that matches the shape of the workpiece after final forging; the upper trimming die moves downward to remove the annular flash formed on the outer periphery of the workpiece tooth due to final forging.

9. A method for forming a non-standard toothed insert using the apparatus described in any one of claims 2-8, characterized in that, Includes the following sequential steps: S1. Shaping: The cylindrical metal blank is placed into the first lower mold cavity of the shaping mold, and the blank is radially constrained and micro-upset at the end face by the first upper mold punch to obtain a first preform with a regular outer diameter; S2. Strong rod section: The first preform is placed into the rod shrinking mold with its rod section facing the rod forming hole; the material of the first preform is forced to flow into the rod forming hole through the conical inlet by the second upper die punch to form a slender rod section, thus obtaining the second preform; S3. Punching and upsetting: The second preform is placed into the third lower die of the upsetting and punching composite die; the composite upper die moves down, and its central punch first punches a guide hole in the center of the blank head, and then the upsetting punch upsets the head with the existing guide hole to obtain the third preform; S4. Inner hole finishing: The third preform is placed into the fourth lower die of the finishing mold; the finishing punch is driven to squeeze through the guide hole in an interference manner, so that the hole wall undergoes plastic deformation to form an inner hole with accurate dimensions and smooth surface, thus obtaining the fourth preform; S5. Toothed final forging: The fourth preform is placed into the closed final forging cavity of the fifth lower die of the toothed final forging die; high pressure is applied by the fifth upper die punch, so that the material at the head of the billet flows plastically in the closed cavity, completely filling the toothed die cavity, and a non-standard toothed structure is precisely forged in one go to obtain the fifth preform with flash; S6. Trimming: The fifth preform is placed into the lower trimming die of the trimming die; the upper trimming die moves downward, and its cutting edge cuts off the annular flash around the tooth shape to obtain the final non-standard tooth insert.

10. A method for forming a non-standard toothed insert according to claim 9, characterized in that, In step S4, after the finishing punch passes through the guide hole, the dimensional tolerance of the inner hole formed is controlled within ±0.03mm, and the surface roughness Ra value is not greater than 1.6μm. In step S5, the forming unit pressure of the final forging of the tooth profile is not less than 1500MPa to ensure that the corners of the tooth profile are fully filled. In steps S2, S3, and S5, before placing the preform into the mold for the next process, a lubricant needs to be sprayed or dipped in it. The cylindrical metal billet is obtained by cold heading and shearing of wire rod. All steps are completed at room temperature or when the billet preheating temperature is lower than the recrystallization temperature. Steps S1 to S6 are carried out continuously on a multi-station cold forming machine or a sequentially arranged press unit to achieve automated production.

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