Device for cold heading and flattening of core rod

Abstract

The utility model relates to the technical field of aviation part machining, and particularly discloses a core rod cold heading and flattening device which comprises a main die and a punching die which are coaxially arranged. The main die comprises a main die sleeve, a front die core and a die cushion, the front die core and the die cushion are detachably arranged in the main die sleeve, the front die core is arranged at the end, close to the stamping die, of the main die sleeve, the front die core is provided with a through first forming hole, the first forming hole comprises a round hole section, a contraction section and a flat hole section which are sequentially arranged, and the die cushion is provided with a rod hole allowing the main die rod to penetrate through. One end of the main mold rod penetrates through the rod hole and enters the first forming hole; the stamping die comprises a stamping die sleeve, a stamping rod and an inner pad, a second forming hole and a punched hole are sequentially formed in the end, close to the main die, of the stamping die sleeve, a containing cavity is formed in the end, away from the main die, of the stamping die sleeve, a through hole allowing the stamping rod to penetrate through is formed between the punched hole and the containing cavity, and the inner pad is installed in the containing cavity. The utility model aims to solve the problems that the existing processing tool for cold heading forming of the core rod is easy to damage and high in use cost.

Description

Technical Field

[0001] This utility model relates to the field of aerospace parts processing technology, and in particular to a device for cold heading and flattening of mandrels. Background Technology

[0002] Blind rivets, with their unique advantage of single-sided installation, play an indispensable role in the aerospace industry. In the manufacturing of aerospace vehicles, many compact and space-constrained areas, such as the wing-fuselage connection area and the fixing positions of some precision components inside aero engines, make double-sided fastener installation difficult. Blind rivets become the ideal choice in these situations. Their riveting principle involves applying a specific external force to the mandrel, causing plastic deformation of the ring and rivet body, thereby firmly connecting two or more components together and providing reliable mechanical connections for aerospace structures.

[0003] From a materials processing perspective, the conventional processing method for these types of mandrels is to first turn the rod section, machine the neck groove, grind, and thread roll, and then use wire EDM to cut both sides of the mandrel to obtain a flat rod section. This conventional material removal processing method has the following drawbacks when processing blind rivet mandrels: because it cuts the grain curve of the material, it damages the integrity of the internal microstructure, making it difficult for the product to meet the high strength requirements of aerospace components. Furthermore, it is prone to breakage during riveting before the riveting effect is achieved, leading to product scrap.

[0004] To address the aforementioned issues, some companies have designed machining fixtures for cold heading. For example, Chinese patent number "202211637576 X" discloses a core-forming device and method for blind rivet rods. This device includes an upper die, a lower die, a precision punch placed on the upper die, and an ejector pin placed on the lower die. The lower die consists of a die sleeve and a die core. To ensure the required strength during core rod forming, both the precision punch and the die core are made of cemented carbide, which is expensive, typically costing 700-800 yuan / kg. However, because the upper die is integrally formed, leaving only an upper cavity for the precision punch, the die core of the lower die is usually interference-fitted with the die core sleeve. During long-term use, the upper and lower molds are prone to damage due to the large impact force during the cold heading process. With the tooling structure of the above-mentioned patent, once the mold sleeve is damaged, the entire mold core and mold sleeve need to be replaced, or if a certain part of the upper mold is damaged, the entire mold needs to be replaced. This results in high tooling costs for processing the core rod. Utility Model Content

[0005] To address the shortcomings of existing technologies, the present invention provides a device for cold heading and flattening of mandrels, thus solving the problems of easy damage and high cost of existing cold heading processing fixtures for mandrels.

[0006] To solve the above problems, the technical solution adopted by this utility model is as follows: A device for cold heading and flattening of a core rod, comprising a main mold and a punch, the main mold and the punch being coaxially arranged; the main mold includes a main mold sleeve, and a front mold core and a mold pad detachably disposed within the main mold sleeve, the front mold core being disposed at the end of the main mold sleeve near the punch, the front mold core having a through first forming hole, the first forming hole including a circular hole segment, a shrinking segment and a flat hole segment arranged sequentially, the mold pad having a rod hole through which the main mold rod passes, one end of the main mold rod passing through the rod hole into the first forming hole; the punch includes a punch sleeve, a punch rod and an inner pad, the end of the punch sleeve near the main mold having a second forming hole and a punch hole arranged sequentially, the diameter of the second forming hole being larger than the diameter of the first forming hole and the diameter of the punch hole, the end away from the main mold having a receiving cavity, a through hole between the punch hole and the receiving cavity for the punch rod to pass through, the inner pad being installed within the receiving cavity.

[0007] The beneficial effects of this plan are:

[0008] 1. This solution breaks down the main mold into a main mold sleeve, mold core, mold pad, and main mold bar, and the punch into a punch sleeve, mold pad, and punch. Therefore, if any part of the main mold sleeve or mold core of the lower mold is damaged, only that part needs to be replaced, instead of replacing the entire lower mold, reducing tooling replacement costs. Similarly, during machining, the main stress-bearing parts of the upper mold are the punch and inner pad. If any part of the inner pad, punch sleeve, or punch is damaged, only the corresponding part needs to be replaced, without replacing the entire part, greatly reducing the cost of machining tooling. Furthermore, the components of the upper and lower molds are simple to assemble and quick to install and remove.

[0009] 2. By adjusting the position of the main mold rod, the tooling of this solution can process similar products with the same rod diameter but different length specifications. The flat parts that originally needed to be machined are extruded by the mold through extrusion deformation. After cold heading and flattening, work hardening occurs, the grains at the processed part become finer, the grain curve at the rod-flat joint is complete and continuous, the strength increases, and the desired effect can be achieved when the product is riveted.

[0010] Furthermore, an annular step for limiting the die core is fixed to the inner wall of the main die sleeve near the punch. The annular step limits the die core, preventing it from extending beyond the die sleeve and facilitating die core assembly.

[0011] Furthermore, a first forming cavity is provided around the first forming hole, and a second forming cavity is provided around the second forming hole and the punch. Both the first and second forming cavities contain cemented carbide. By using cemented carbide, the hardness of the material around the first forming hole, the second forming hole, and the punch is increased, making the first forming hole, the second forming hole, and the punch less prone to deformation and ensuring the mandrel forming process effect. The cemented carbide in the second forming cavity ensures the required material hardness around the second forming cavity during cold heading of the mandrel. Therefore, the punch in this solution does not need to be made of cemented carbide; it can be made of ordinary alloy, reducing processing costs.

[0012] Furthermore, a third forming cavity is provided around the rod hole at one end of the mold pad near the front mold core, and the third forming cavity contains cemented carbide. By setting the third forming cavity, the material hardness around the rod hole within the range of the third forming cavity is enhanced, so that the material strength around some rod holes can also meet the material hardness required for mandrel upsetting; the length range of the third forming cavity and the first forming cavity together constitute the adjustable mandrel length, thereby expanding the range of mandrel lengths that can be machined by the entire tooling.

[0013] Furthermore, the diameters of the first, second, and third forming cavities are equal, and the diameter of the third forming cavity is 4-6 mm larger than the head size of the core rod. Since the main mold of this design is composed of multiple modules, it is not necessary to replace the entire main mold if a part is damaged. Therefore, it is not necessary to apply a large area of ​​hard alloy to the mold core or mold pad to ensure material hardness and thus extend the service life of the equipment. By applying hard alloy in a small area, the processing requirements of the core rod can be met, while reducing the cost of processing tooling.

[0014] Furthermore, the combined length of the first forming cavity and the second forming cavity is 4-6 mm longer than the length of the mandrel formed within the forming cavity. Since the die in this design is composed of multiple modules, the entire die does not need to be replaced if one part is damaged. Therefore, it is unnecessary to apply a large area of ​​hard alloy to the die sleeve to ensure material hardness and extend the equipment's service life. By applying hard alloy in a smaller area, the processing requirements of the mandrel can be met while reducing processing tooling costs. Simultaneously, the most vulnerable punch is made of ordinary alloy, resulting in low replacement costs.

[0015] Furthermore, the length of the receiving cavity is greater than half the length of the die sleeve. The receiving cavity reduces the material required for the entire die sleeve, and, in conjunction with a replaceable inner shim, limits the movement of the punch during processing.

[0016] Furthermore, the punch includes a cylinder and a limiting ring fixed at one end of the cylinder. The structure is simple and easy to manufacture. Attached Figure Description

[0017] Figure 1A schematic diagram showing the cutting process of the mandrel to its final form;

[0018] Figure 2 This is a cross-sectional view of the core rod section;

[0019] Figure 3 This is a schematic diagram of the processing tooling for this utility model;

[0020] Figure 4 Schematic diagram of the main mold sleeve;

[0021] Figure 5 This is a schematic diagram of the front mold core and the shrinkage section of the forming hole;

[0022] Figure 6 This is a schematic diagram of the mold pad and the hole pattern of the rod.

[0023] Figure 7 This is a schematic diagram of a punching die sleeve;

[0024] Figure 8 This is a schematic diagram of the punch. Detailed Implementation

[0025] The following detailed description illustrates the specific implementation method:

[0026] The reference numerals in the accompanying drawings include: main mold sleeve 1, annular step 11, front mold core 2, first forming hole 21, first forming cavity 22, mold pad 3, bar hole 31, third forming cavity 32, main mold bar 4, punch sleeve 5, second forming hole 51, punch 52, second forming cavity 53, receiving cavity 54, inner pad 6, punch bar 7, and core rod 8.

[0027] The core rod of the blind rivet to be processed is 8, as shown. Figure 1 , Figure 2 As shown in the attached figure. The basic processing tooling of this utility model is as follows. Figure 3 As shown: A device for cold heading and flattening of a mandrel 8 includes a main die and a punch, the main die and the punch being coaxially arranged; as shown Figure 4 , Figure 5 , Figure 6As shown, the main mold includes a main mold sleeve 1, and a mold core and a mold pad 3 arranged sequentially from right to left within the main mold sleeve 1. A ring-shaped step 11 for positioning is fixed to the inner wall of the main mold sleeve 1 near its right end. The right end of the mold core is stepped to mate with the ring-shaped step 11. The inner wall of the left end of the main mold sleeve 1 has a chamfer to facilitate the loading and unloading of the mold pad 3 and the mold core. The main mold sleeve 1 is clearance-fitted with the front mold core 2 and the mold pad 3. The front mold core 2 has a through first forming hole 21, which includes a circular hole section, a shrinking section, and a flat hole section arranged sequentially from right to left. The shrinking section includes two parallel arc-shaped surfaces. The mold pad 3 is provided with a rod hole 31 through which the main mold rod 4 can pass, and the shape of the rod hole 31 is consistent with the flat hole section. The main mold rod 4 is a flat rod that fits with the flat hole section and the rod hole 31. One end of the main mold rod 4 passes through the rod hole 31 and enters the first forming hole 21. The first forming hole 21 is surrounded by a first forming cavity 22. The first forming cavity 22 and the third forming cavity 32 are both provided with hard alloy in an interference fit manner.

[0028] like Figure 7 , Figure 8 As shown, the die includes a die sleeve 5, a punch 7, and an inner pad 6. The die sleeve 5 has a second forming hole 51 and a punch 52 sequentially arranged at the end near the main die. The diameter of the second forming hole 51 is larger than the diameter of the first forming hole 21 and the diameter of the punch 52. The end away from the main die has a receiving cavity 54. A through hole for the punch 7 to pass through is provided between the punch 52 and the receiving cavity 54. The inner pad 6 is installed in the receiving cavity 54, and its right end is parallel to the right end of the die. A second forming cavity 53 is provided around the second forming hole 51 and the punch 52, and a hard alloy is provided inside the second forming cavity 53. The punch 7 includes a cylinder and a limiting ring fixed to one end of the cylinder. The main die 4, the first forming hole 21, the second forming hole 51, the third forming hole, and the punch 7 are located on the same axis.

[0029] The punch 7 is made of M42 or H55 material, and the main die sleeve 1, die pad 3, die core, punch sleeve 5, and inner pad 6 are made of H13 or SKD61.

[0030] The usage steps are as follows;

[0031] 1) Assemble each component in sequence as follows: Figure 1 As shown; 2) Install the assembled main mold into the main mold cavity of the existing cold heading equipment and lock it in place. Install the punch into the punch mold cavity of the cold heading equipment, insert the movable punch pin, and fix the punch to the punch mold cavity. Attach the punch end and inner pad 6 to the punch adjusting wedge of the equipment; 3) Adjust the threaded sleeve at the main mold end to position the main mold bar 4 to a suitable position, that is, to meet the length requirement of the flat rod after the core rod 8 is processed; 4) Adjust the punch adjusting wedge of the equipment so that the punch bar 7 of the punch is coaxial with the first forming hole 21; 5) The clamping mechanism of the existing equipment will be as follows: Figure 1The cut blank shown is fed into the mold to start the upsetting and extrusion of the product. Check whether the upset product meets the requirements of the drawing; 6) Repeat steps 3), 4), and 5) until the product is qualified.

[0032] The similarities between Example 2 and Example 1 will not be repeated here. The difference lies in that the diameters of the first forming cavity 22, the second forming cavity 53, and the third forming cavity 32 are equal, and the diameter of the third forming cavity 32 is 4-6 mm larger than the head size of the core rod 8, preferably 5 mm in this example. The length of the third forming cavity 32 is less than half the length of the die pad 3. The combined length of the first forming cavity 22 and the second forming cavity 53 is 4-6 mm greater than the length of the core rod formed in the forming cavity. Since the die in this design is composed of multiple modules, it is not necessary to replace the entire die when a part is damaged. Therefore, it is not necessary to set a large area of ​​hard alloy on the die sleeve 5 to ensure material hardness and thus extend the service life of the equipment. By setting a small area of ​​hard alloy, the processing requirements of the core rod 8 can be met, and the processing tooling cost is reduced. At the same time, the most easily damaged punch 7 is made of ordinary alloy, and the replacement cost is low.

[0033] The above descriptions are merely embodiments of this utility model, and common knowledge regarding specific structures and characteristics is not elaborated upon here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the structure of this utility model, and these should also be considered within the scope of protection of this utility model. These modifications will not affect the effectiveness of the implementation of this utility model or the practicality of the patent. The scope of protection claimed in this application shall be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. An apparatus for cold upsetting and ironing of a core rod, characterized in that: The device includes a main mold and a punch, which are coaxially arranged. The main mold includes a main mold sleeve, and a front mold core and a mold pad detachably disposed within the main mold sleeve. The front mold core is located at the end of the main mold sleeve near the punch and has a through first forming hole. The first forming hole includes a circular hole section, a shrinkage section, and a flat hole section arranged sequentially. The mold pad has a rod hole through which the main mold rod passes, and one end of the main mold rod passes through the rod hole into the first forming hole. The punch includes a punch sleeve, a punch rod, and an inner pad. The end of the punch sleeve near the main mold has a second forming hole and a punch hole arranged sequentially. The diameter of the second forming hole is larger than the diameter of the first forming hole and the diameter of the punch hole. The end away from the main mold has a receiving cavity. A through hole through which the punch rod passes is provided between the punch hole and the receiving cavity. The inner pad is installed in the receiving cavity.

2. A device for cold upsetting and ironing of a core pin according to claim 1, characterized in that: The inner wall of the main die sleeve near the punch is fixed with an annular step for limiting positioning.

3. A device for cold upsetting and ironing of a core pin according to claim 1, characterized in that: A first forming cavity is provided around the first forming hole, and a second forming cavity is provided around the second forming hole and the punch hole. Hard alloy is provided in both the first forming cavity and the second forming cavity.

4. A device for cold upsetting and ironing of a core pin according to claim 3, characterized in that: The mold pad has a third forming cavity around the rod hole at one end near the front mold core, and the third forming cavity contains hard alloy.

5. A device for cold upsetting and ironing of a core pin according to claim 4, characterized in that: The diameters of the first forming cavity, the second forming cavity, and the third forming cavity are equal, and the diameter of the third forming cavity is 4-6 mm larger than the head size of the core rod.

6. A device for cold upsetting and ironing of a core pin according to claim 3, characterized in that: The combined length of the first forming cavity and the second forming cavity is 4-6 mm longer than the length of the core rod formed in the forming cavity.

7. A device for cold upsetting and ironing of a core pin according to claim 1, characterized in that: The length of the receiving cavity is greater than half the length of the die sleeve.

8. A device for cold upsetting and ironing of a core pin according to claim 1, characterized in that: The punch includes a cylinder and a limiting ring fixed at one end of the cylinder.

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