Cold extrusion die for cross-axis near-net shape molding

Abstract

This invention provides a cold extrusion die for cross-axis near-net-shape molding that can achieve cross-axis near-net-shape molding and prevent cracking due to mold expansion caused by weight errors of the supplied material during near-net-shape molding. [Solution] The present invention discloses a cold extrusion die for cross-axis near-net-shape forming relating to the technical field of cold extrusion dies, comprising an upper die, a lower die, and a positioning pin disposed between the upper die and the lower die, wherein the upper die is provided with an upper die core, the lower die is provided with a lower die core, and four shaft head cavities are provided on the outer circumference of a central cavity formed by the upper die core and the lower die core, the central cavity and each of the shaft head cavities constitute a near-net-shape forming cavity, the near-net-shape forming cavity has a finishing allowance based on the corresponding cavity of the finished product, and each of the shaft head cavities is provided with a free cavity extending outward at its distal end from the central cavity.

Description

Technical Field

[0001] The present invention relates to the technical field of cold extrusion dies, and particularly relates to a cold extrusion die for near-net-shape forming of cross shafts.

Background Art

[0002] A die is a tool for producing molded articles. It mainly realizes shape processing of objects by changing the physical state of molding materials, and is known as the "mother of industry". It is widely used in stamping, die forging, cold heading, extrusion, powder metallurgy pressing, pressure casting, and compression or injection molding processing of products such as engineering plastics, rubber, and ceramics. A die is a precision tool with a complex shape, and has high requirements for the expansion force, structural strength, rigidity, surface hardness, surface roughness, and processing accuracy of the blank. Therefore, the level of die design and manufacturing is one of the important indicators of the level of machine manufacturing.

[0003] The higher the accuracy of the die, the closer the molded article is to the delivery state of the finished product, the lower the subsequent processing cost, the less material required for molding, and the lower the manufacturing cost. Therefore, ensuring the accuracy of the die as much as possible is the best solution to reduce costs and improve the market competitiveness of molded articles. Hot forging dies have poor accuracy, large forging allowances, and large burrs on molded articles, which leads to material waste and increased subsequent processing costs. Therefore, in order to realize near-net-shape forming of molded articles, fully-enclosed cold extrusion forming dies are generally used.

[0004] Existing cold extrusion cruciate forming dies can achieve more precise dimensions than hot forging through sealed forming. However, to prevent cracking or bursting due to mold expansion caused by uneven weight distribution during material supply, the cavity size must be appropriately enlarged during die manufacturing. This prevents obtaining a blank size closer to the finished product, thus limiting the advantages of sealed cold extrusion forming, such as achieving a blank size closer to the finished product, reducing processing steps, shortening production cycles, saving materials, and lowering costs. This invention provides a cruciate cold extrusion die that achieves near-net-shape forming by modifying the die structure, thereby achieving the objectives of obtaining a near-net-shape blank and preventing cracking due to mold expansion. [Overview of the project] [Problems that the invention aims to solve]

[0005] The present invention aims to solve the problems of the prior art described above, to provide a cold extrusion die for cross-axis near-net-shape molding that can achieve cross-axis near-net-shape molding and prevent cracking due to mold expansion caused by weight errors of the supplied material during near-net-shape molding. [Means for solving the problem]

[0006] To achieve the above objective, the present invention provides the following solutions.

[0007] The present invention provides a cold extrusion die for cross-axis near-net-shape molding, comprising an upper die, a lower die, and a positioning pin positioned between them, wherein the upper die is provided with an upper die core, and the lower die is provided with a lower die core, and four shaft head cavities are provided on the outer circumference of a central cavity formed by the upper die core and the lower die core, the central cavity and each of the shaft head cavities constitute a near-net-shape molding cavity, the near-net-shape molding cavity has a finish allowance based on the corresponding cavity of the finished product, and each of the shaft head cavities has a free cavity extending outward at its distal end from the central cavity.

[0008] In one embodiment, the finishing allowance is 0.1 mm to 0.2 mm.

[0009] In one embodiment, the free cavity is a cylindrical cavity.

[0010] In one embodiment, the free cavity extends outward from the center of the end face of the shaft head cavity.

[0011] In one embodiment, the axis of the cylindrical cavity passes through the center of the central cavity.

[0012] In one embodiment, the upper mold core is provided with an upper half near-net-shape molding cavity, and the lower mold core is provided with a lower half near-net-shape molding cavity. When the molds are clamped, the upper half near-net-shape molding cavity and the lower half near-net-shape molding cavity form the near-net-shape molding cavity.

[0013] In one embodiment, the upper mold core is provided with an upper half free cavity, and the lower mold core is provided with a lower half free cavity. When the molds are clamped, the upper half free cavity and the lower half free cavity form the free cavity.

[0014] In one embodiment, ejector rod cavities are installed at the top and bottom of the central cavity, respectively.

[0015] In one embodiment, an ejector rod is provided in the ejector rod cavity, the ejector rod is fitted with clearance to the ejector rod cavity, and a plurality of grooves are evenly spaced around the ejector end of the ejector rod. In one embodiment, the groove includes four grooves. [Effects of the Invention]

[0016] Compared to conventional technology, the present invention achieves the following technical effects. The cold extrusion die for cross-axis near-net-shape forming provided by the present invention allows the size of the resulting blank to be close to that of the finished product due to the near-net-shape forming cavity, the blank size being only one size larger than the finished product size, and the blank after extrusion forming with the additional finishing allowance to improve the tolerance level of critical sizes, resulting in a finished product that meets requirements, reducing processing steps, saving material, and during extrusion forming, under conditions of mold resistance, excess material can flow into the surrounding free cavity, preventing cracking due to mold expansion and maximizing material savings. [Brief explanation of the drawing]

[0017] To more clearly illustrate embodiments of the present invention or technical solutions in the prior art, the drawings that need to be used in the embodiments are briefly described below. Obviously, the drawings in the following description are only a few embodiments of the present invention, and those skilled in the art can obtain other drawings based on these without any creative effort.

[0018] [Figure 1] This is a bottom view of the upper mold in an embodiment of the present invention. [Figure 2] This is a cross-sectional view AA in Figure 1. [Figure 3] This is a top view of the lower mold in an embodiment of the present invention. [Figure 4] Figure 3 is a cross-sectional view of BB. [Figure 5] This is a schematic diagram showing the process of clamping the upper mold in Figure 2 and the lower mold in Figure 4. [Figure 6] This is a schematic diagram of the ejector rod in an embodiment of the present invention. [Modes for carrying out the invention]

[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by a person of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0020] The present invention solves the problems existing in the above prior art, realizes near-net-shape forming of cross shafts, and can achieve burr-free forming of cross shaft blanks through closed forming of upper and lower dies. Since the formed cross shaft blank is close to the finished cross shaft product, the machining allowance is extremely small, materials are greatly saved, machining processes are reduced, the production cycle is shortened, and the present invention aims to provide a cold extrusion die for cross shaft near-net-shape forming that can prevent cracking caused by die expansion due to weight error of supplied materials during near-net-shape forming.

[0021] In order to make the above objects, features and advantages of the present invention more prominent and easy to understand, the present invention will be described in more detail below with reference to the drawings and the detailed description for carrying out the invention.

[0022] As shown in Figures 1 to 6, this embodiment provides a cold extrusion die for cross shaft near-net-shape forming, which includes an upper die 1, a lower die 2, and a positioning pin 3 arranged therebetween. The upper die 1 is provided with an upper die core 4, the lower die 2 is provided with a lower die core 5, and four shaft head cavities 7 are arranged on the outer periphery of the central cavity 6 formed by the upper die core 4 and the lower die core 5. The central cavity 6 and each shaft head cavity 7 constitute a near-net-shape forming cavity 8, which has a finishing allowance based on the corresponding cavity of the finished product, and the distal end of each shaft head cavity 7 away from the central cavity 6 is provided with a freely extending cavity 9 extending outward.

[0023] During cold extrusion, the near-net-shape forming cavity 8 ensures that the resulting blank size is close to the finished product size, with the blank size being only one size larger than the finished product size by a finishing allowance. After extrusion, the blank improves the tolerance level of critical sizes with the additional finishing allowance, resulting in a finished product that meets the requirements, reducing processing steps and processing costs, saving material, and during extrusion, under mold resistance conditions, excess material can flow into the surrounding free cavity 9, preventing cracking due to mold expansion and maximizing material savings. Using this cold extrusion die enables cross-axis near-net-shape forming, reducing processing steps, shortening production cycles, improving production efficiency, saving material, lowering production costs, and enhancing the market competitiveness of the product.

[0024] Of this, the finishing allowance will be 0.1mm to 0.2mm. This can be freely set according to the actual situation.

[0025] In this embodiment, the free cavity 9 extends outward from the center of the end face of the shaft head cavity 7. The free cavity 9 is a cylindrical cavity. The axis of the cylindrical cavity passes through the center of the central cavity 6. After obtaining the blank by extrusion molding, it is necessary to cut off the excess part formed in the free cavity 9.

[0026] In this embodiment, the upper mold core 4 is provided with an upper half near-net-shape molding cavity 10, and the lower mold core 5 is provided with a lower half near-net-shape molding cavity 11. When the mold is clamped, the upper half near-net-shape molding cavity 10 and the lower half near-net-shape molding cavity 11 form a near-net-shape molding cavity 8. The upper mold core 4 is provided with an upper half free cavity 12, and the lower mold core 5 is provided with a lower half free cavity 13. When the mold is clamped, the upper half free cavity 12 and the lower half free cavity 13 form a free cavity 9. The upper mold core 4 and the lower mold core 5 are arranged symmetrically to facilitate the manufacturing of the mold.

[0027] In this embodiment, ejector rod cavities 14 are installed at the top and bottom of the central cavity 6, respectively.

[0028] In this embodiment, an ejector rod 15 is provided in the ejector rod cavity 14, and the ejector rod 15 is fitted with clearance to the ejector rod cavity 14. Multiple grooves 16 are evenly spaced around the ejector end of the ejector rod 15. Specifically, there are four grooves 16. When the cross shaft is formed, the upper ejector rod 15 and the lower ejector rod 15 form a petal structure in the middle part of the cross shaft.

[0029] By removing redundant structures corresponding to the free cavity 9 from the cross shaft blank after petal positioning molding, symmetry errors between the four shaft head end faces can be minimized. Furthermore, the use of petal positioning allows for an appropriate increase in the radius of the central cavity of the cross shaft, thereby expanding the central body of the cross shaft and increasing its strength. For the same cross shaft length and to ensure the same shaft head machining size, using petal positioning saves the shaft head length required for shaft head positioning compared to machining the cross shaft using shaft head positioning. This length can be used to expand the intermediate body of the cross shaft, improving its strength.

[0030] This invention uses specific examples to illustrate the principles and embodiments of the present invention, and the above description of the embodiments is intended only to aid in understanding the methods and technical concept of the present invention. At the same time, those skilled in the art will know that the modes and scope of application for carrying out the invention will vary depending on the technical concept of the invention. In summary, the contents of this specification should not be understood as limiting the present invention. [Explanation of Symbols]

[0031] 1 Upper mold 2 Lower mold 3 Positioning pins 4 Upper core 5. Lower core 6. Center cavity 7 Axis head cavity 8 Near-net-shape molded cavities 9 Free Cavity 10. Upper half near-net-shape molded cavity 11. Lower half near-net-shape molded cavity 12. Upper half free cavity 13. Lower half free cavity 14 Ejector Rod Cavity 15 Ejector Rod 16 groove

Claims

1. A cold extrusion die for cross-axis near-net-shape molding includes an upper die, a lower die, and a positioning pin positioned between the upper and lower dies, wherein the upper die is provided with an upper die core, the lower die is provided with a lower die core, and four axial head cavities are provided on the outer circumference of the central cavity formed by the upper and lower die cores, A cold extrusion die for cross-axis near-net-shape molding, characterized in that the central cavity and each of the shaft head cavities constitute a near-net-shape molding cavity, the near-net-shape molding cavity has a finishing allowance based on the corresponding cavity of the finished product, and each of the shaft head cavities is provided with a free cavity extending outward at its distal end from the central cavity.

2. The cold extrusion die for cross-axis near-net-shape molding according to claim 1, characterized in that the aforementioned finishing allowance is 0.1 mm to 0.2 mm.

3. The cold extrusion die for cross-axis near-net-shape molding according to claim 1, characterized in that the free cavity is a cylindrical cavity.

4. The cold extrusion die for cross-axis near-net-shape molding according to claim 1, characterized in that the free cavity extends outward from the center of the end face of the shaft head cavity.

5. The cold extrusion die for cross-axis near-net-shape molding according to claim 3, characterized in that the axis of the cylindrical cavity passes through the center of the central cavity.

6. The upper mold core is provided with an upper half near-net-shape molding cavity, the lower mold core is provided with a lower half near-net-shape molding cavity, and when the mold is clamped, the upper half near-net-shape molding cavity and the lower half near-net-shape molding cavity constitute the near-net-shape molding cavity, characterized in that the cold extrusion mold for cross-axis near-net-shape molding according to claim 1.

7. The upper mold core is provided with an upper half free cavity, the lower mold core is provided with a lower half free cavity, and when the mold is clamped, the upper half free cavity and the lower half free cavity constitute the free cavity, characterized in that the cold extrusion mold for cross-axis near-net-shape molding according to claim 1.

8. The cold extrusion die for cross-axis near-net-shape molding according to claim 1, characterized in that ejector rod cavities are installed in the upper part of the central cavity and in the lower part of the central cavity, respectively.

9. The cold extrusion die for cross-axis near-net-shape molding according to claim 8, characterized in that an ejector rod is provided in the ejector rod cavity, the ejector rod is fitted with clearance to the ejector rod cavity, and a plurality of grooves are evenly provided around the extruded end of the ejector rod.

10. The cold extrusion die for cross-axis near-net-shape molding according to claim 9, characterized in that the plurality of grooves are four grooves.

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