A drawing die for a fender

Abstract

The utility model provides a kind of for fender's drawing die, it is related to the technical field of automobile stamping die, including lower die holder;Upper die holder is connected in the upper end of lower die holder;Lower drawing die, lower drawing die is connected in the upper end of lower die holder;Upper drawing die, upper drawing die is connected in the lower end of upper die holder;At least one set of clamping mechanism, clamping mechanism is respectively set between lower die holder and lower drawing die and upper die holder and upper drawing die, by setting cross groove and cross block, round groove and round block realize the quick positioning between upper and lower drawing die and die holder, cooperate the structure in clamping mechanism and clamping assembly, such as through slot, sliding rod, conical block, spring and triangular block, realize automatic locking when die is closed, effectively improve the connection stability and operating convenience, to significantly improve production efficiency.

Description

Technical Field

[0001] This utility model relates to the field of automotive stamping die technology, and in particular to a drawing die for a fender. Background Technology

[0002] In the automotive manufacturing industry, especially in the production of body panels, drawing dies are widely used to process sheet metal into parts of the required shape and size, such as fenders. These dies typically consist of an upper die holder, a lower die holder, and corresponding punches and dies, and the plastic deformation of the material is achieved through the relative movement between the upper and lower die holders.

[0003] Currently available drawing dies on the market are structurally designed to meet basic operational needs, but there is still room for improvement in some key aspects: Traditional drawing dies typically rely on guide pillars and bushings or simple planar fits for aligning the upper and lower dies. While these methods can guide die closure to some extent, positional deviations may occur with increased usage frequency and prolonged operation, affecting the overall operational process. Furthermore, existing locking devices mostly employ external bolts or other mechanical clamping methods, which not only increases operational complexity but may also limit the speed and efficiency of die opening and closing.

[0004] To address the aforementioned issues, a drawing die for fenders is now designed. Utility Model Content

[0005] To address the aforementioned technical problems, this utility model provides a drawing die for a fender, as described in this application embodiment, to solve the above-mentioned technical problems.

[0006] This utility model provides a drawing die for a fender, comprising:

[0007] Lower mold base;

[0008] An upper mold base, which is connected to the upper end of a lower mold base;

[0009] A drawing die, wherein the drawing die is connected to the upper end of the lower die base;

[0010] An upper drawing die, wherein the upper drawing die is connected to the lower end of the upper die holder;

[0011] At least one set of locking mechanisms is provided, which are respectively disposed between the lower die holder and the lower drawing die and the upper die holder and the upper drawing die. The locking mechanism includes a through groove, a first sliding rod, a first conical block, a second conical block, a second spring, a baffle, and a splitting assembly. The through groove is respectively opened at the upper and lower ends of each set of lower die holder and lower drawing die and upper die holder and upper drawing die. The first sliding rod is slidably connected in the through groove. The first conical block is slidably connected to the circumferential surface of the first sliding rod and matches the through groove. The second conical block is fixedly connected to the side end of the first conical block. The second spring is sleeved and connected to the circumferential surface of the first sliding rod and its side end is connected to the first conical block. The baffle is fixedly connected to the side end of the first sliding rod. The locking assembly is disposed at the side end of the locking mechanism to realize the splitting and joining of the lower die holder and the upper die holder.

[0012] Preferably, the engaging assembly includes a mounting groove, a second sliding rod, a third spring, a triangular block, and a convex block. The mounting groove is respectively opened on the side ends of the lower mold base and the upper mold base. The second sliding rod is slidably connected in the mounting groove. The third spring is sleeved and connected to the circumferential surface of the second sliding rod. The triangular block is fixedly connected to the side end of the second sliding rod. The convex block is fixedly connected to the other side end of the first sliding rod. The convex block matches the through groove. The triangular block matches the first conical block, the second conical block, and the convex block, respectively.

[0013] Preferably, a lower base is fixedly connected to the upper end of the lower mold base, and an upper base is fixedly connected to the upper end of the upper mold base. A slot is provided at the upper end of the upper base, and a locking block is engaged in the slot. A limiting plate is fixedly connected to the lower end of the locking block. A telescopic rod is connected between the limiting plate and the lower base, and a first spring is sleeved on the circumferential surface of the telescopic rod.

[0014] Preferably, the upper end of the lower drawing die has a notch, and the upper end of the upper drawing die has a protrusion, the protrusion matching the notch.

[0015] Preferably, the upper ends of the lower die holder and the upper die holder are respectively provided with a cross groove and a circular groove, and the upper ends of the lower drawing die and the upper drawing die are respectively fixedly connected with a cross block and a circular block, the cross groove matches the cross block, and the circular groove matches the circular block.

[0016] Preferably, the upper end of the upper drawing die is provided with a second vent hole, and the upper end of the lower drawing die is provided with a first vent hole, and the second vent hole matches the first vent hole.

[0017] Compared with related technologies, the drawing die for fenders provided by this utility model has the following advantages:

[0018] 1. This utility model achieves rapid positioning between the upper and lower drawing dies and the die base by designing structures such as cross grooves and cross blocks, and circular grooves and circular blocks. In addition, the locking mechanism includes a through groove, a first sliding rod, a first conical block, a second conical block, a second spring, a baffle, and a splitting assembly. The locking assembly includes a mounting groove, a second sliding rod, a third spring, a triangular block, and a convex block, which work together to automatically lock the die when it is closed. This design not only improves the connection stability of the upper and lower die bases in the closed state, but also simplifies the operation steps, enabling the die to complete the opening and closing action more quickly and improving production efficiency.

[0019] 2. In this solution, the lower drawing die and the upper drawing die are fixed by inserting the cross block and the round block at their bottom into the corresponding cross groove and round groove, respectively. This modular design facilitates quick disassembly and replacement of different models of dies. At the same time, the design of the notch and the protrusion further ensures quick alignment after each replacement, reducing the time for recalibration. In addition, the presence of the first vent and the second vent helps to expel the gas generated during the molding process, avoiding product defects caused by air bubbles, and also facilitates subsequent cleaning work, improving the maintainability of the equipment. Attached Figure Description

[0020] Figure 1 A three-dimensional structural schematic diagram provided for an embodiment of this application;

[0021] Figure 2 An exploded view diagram provided for an embodiment of this application;

[0022] Figure 3 Provided for the embodiments of this application Figure 2 Exploded 3D view of the lower mold base;

[0023] Figure 4 Provided for the embodiments of this application Figure 2 A three-dimensional structural cross-sectional view of the lower mold base;

[0024] Figure 5 Provided for the embodiments of this application Figure 4 Enlarged view of the three-dimensional structure at point A in the middle;

[0025] Figure 6 Provided for the embodiments of this application Figure 2 A three-dimensional structural cross-sectional view of the upper and middle mold base;

[0026] Figure 7 An exploded view of the three-dimensional structure provided in the embodiments of this application.

[0027] In the diagram: 1. Lower die base; 101. Lower base; 103. Lower drawing die; 104. Notch; 105. First vent hole; 2. Upper die base; 201. Upper base; 202. Clamp; 203. Upper drawing die; 204. Protrusion; 205. Second vent hole; 3. Telescopic rod; 301. Limiting plate; 302. Clamping block; 303. First spring; 4. Through groove; 401. First sliding rod; 402. First conical block; 403. Second conical block; 404. Second spring; 405. Baffle; 406. Mounting groove; 407. Second sliding rod; 408. Third spring; 409. Triangular block; 410. Protruding block; 5. Cross groove; 501. Circular groove; 502. Cross block; 503. Circular block. Detailed Implementation

[0028] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0029] Please refer to the following: Figures 1 to 7 A drawing die for a fender, comprising:

[0030] Lower mold base 1;

[0031] Upper mold base 2 is connected to the upper end of lower mold base 1;

[0032] The lower drawing die 103 is connected to the upper end of the lower die base 1;

[0033] Upper drawing die 203 is connected to the lower end of upper die holder 2;

[0034] At least one set of locking mechanisms is provided, which are respectively disposed between the lower die base 1 and the lower drawing die 103 and the upper die base 2 and the upper drawing die 203. The locking mechanism includes a through groove 4, a first sliding rod 401, a first conical block 402, a second conical block 403, a second spring 404, a baffle 405, and a splitting assembly. The through groove 4 is respectively opened at the upper and lower ends of each set of lower die base 1 and lower drawing die 103 and upper die base 2 and upper drawing die 203. The first sliding rod 401 is slidably connected to the through groove 4. Inside, the first conical block 402 is slidably connected to the circumferential surface of the first sliding rod 401, and the first conical block 402 matches the through groove 4. The second conical block 403 is fixedly connected to the side end of the first conical block 402. The second spring 404 is sleeved and connected to the circumferential surface of the first sliding rod 401, and its side end is connected to the first conical block 402. The baffle 405 is fixedly connected to the side end of the first sliding rod 401. The engaging assembly is set on the side end of the engaging mechanism to realize the separation and engagement of the lower mold base 1 and the upper mold base 2.

[0035] In the specific implementation process, when a drawing process is required, the metal sheet to be processed is first placed on the upper surface of the lower drawing die 103 and its position is ensured to be accurate; then the drive device is started to make the upper die holder 2 move downward, driving the upper drawing die 203 connected to it to press down synchronously, and gradually close with the lower drawing die 103.

[0036] In this way, the relative movement between the upper and lower mold bases causes the locking mechanism to function: the first sliding rod 401 in the through groove 4 slides into the groove under external pressure, and the first conical block 402 moves with the first sliding rod 401 and slides outward in the circumferential direction, contacting and engaging with the inner wall of the through groove 4, thus playing a guiding and locking role; at the same time, the second conical block 403 moves with the first conical block 402, and is linked with the splitting and engaging assembly through the baffle 405 to achieve positioning and locking between the upper mold base 2 and the lower mold base 1.

[0037] After the upper mold base 2 is fully pressed onto the lower mold base 1, the locking assembly further enhances the stability of the mold in the closed state: the second sliding rod 407 in the mounting groove 406 slides inward under pressure, the third spring 408 is compressed and stores energy, and the triangular block 409 moves accordingly and engages with the convex block 410, thereby preventing the mold from shifting or loosening during the drawing process and ensuring molding accuracy.

[0038] In this way, when the mold is in a fully closed state and the drawing process is completed, the control system sends an opening signal, and the drive device reverses its action to drive the upper mold base 2 to rise. At this time, each elastic element, such as the second spring 404 and the third spring 408, releases energy, pushes the sliding component to reset, and the locking mechanism and locking assembly disengage in sequence, so that the upper mold base 2 and the lower mold base 1 can be separated smoothly, making it easy to remove the formed fender part.

[0039] In this way, once the entire drawing process is completed, the mold returns to its initial open state, waiting for the start of the next processing cycle, thus achieving the goals of stable mold opening and closing control, rapid positioning and locking, and efficient continuous production.

[0040] refer to Figures 1 to 7 As shown, the engaging assembly includes a mounting groove 406, a second sliding rod 407, a third spring 408, a triangular block 409, and a convex block 410. The mounting groove 406 is respectively opened on the side ends of the lower mold base 1 and the upper mold base 2. The second sliding rod 407 is slidably connected in the mounting groove 406. The third spring 408 is sleeved and connected to the circumferential surface of the second sliding rod 407. The triangular block 409 is fixedly connected to the side end of the second sliding rod 407. The convex block 410 is fixedly connected to the other side end of the first sliding rod 401. The convex block 410 matches the through groove 4. The triangular block 409 matches the first conical block 402, the second conical block 403, and the convex block 410 respectively.

[0041] It should be noted that the locking assembly, as a key locking and linkage structure in the mold opening and closing process, achieves further locking and positioning of the upper mold base 2 and the lower mold base 1 in the closed state through the coordinated cooperation between the mounting groove 406, the second sliding rod 407, the third spring 408, the triangular block 409 and the convex block 410.

[0042] Specifically, when the upper mold base 2 moves downward and approaches the lower mold base 1 to close, the convex block 410 fixedly connected to the first sliding rod 401 gradually approaches the area of ​​the mounting groove 406 and forms contact with the triangular block 409; at this time, the second sliding rod 407 slides along the mounting groove 406 under the external force, compresses the third spring 408, and causes the triangular block 409 to move inward and contact the inclined surface of the convex block 410 and slide into its engaging position.

[0043] In this way, a stable mechanical engagement is formed between the triangular block 409 and the convex block 410. At the same time, the triangular block 409 also cooperates with the first conical block 402 and the second conical block 403 respectively, thereby linking the locking mechanism and the locking assembly, enhancing the stability and rigidity of the entire structure in the closed state, and preventing accidental mold opening or displacement caused by external force or vibration.

[0044] In this way, after the drawing is completed, the upper die holder 2 rises, the first sliding rod 401 drives the convex block 410 to disengage from the triangular block 409, the third spring 408 releases its elastic force to push the second sliding rod 407 to reset, thereby disengaging the triangular block 409 from the engagement state and realizing the smooth opening of the die.

[0045] refer to Figures 1 to 7 As shown, the upper end of the lower mold base 1 is fixedly connected to the lower base 1, and the upper end of the upper mold base 2 is fixedly connected to the upper base 201. The upper end of the upper base 201 is provided with a slot 202, and a locking block 302 is locked in the slot 202. The lower end of the locking block 302 is fixedly connected to the limiting plate 301. A telescopic rod 3 is connected between the limiting plate 301 and the lower base 101. A first spring 303 is sleeved and connected to the circumferential surface of the telescopic rod 3.

[0046] It should be noted that: before the mold starts working, the metal sheet to be processed is first placed on the surface of the lower drawing mold 103 on the lower mold base 1, and its position is adjusted to ensure forming accuracy; at this time, the upper mold base 2 is in the open state, the upper seat 201 connected to it is in the high position, the locking block 302 is embedded in the locking slot 202, the limiting plate 301 and the lower seat 101 are kept at a certain distance through the telescopic rod 3, and the first spring 303 is in the naturally extended state.

[0047] In this way, the entire guide and limit structure provides a stable initial position for the subsequent mold closing action. At the same time, through the cooperation of the telescopic rod 3 and the first spring 303, the limit plate 301 has a certain buffering capacity to prevent damage to the mold or workpiece due to excessive impact force.

[0048] When the upper mold base 2 begins to descend to perform the mold closing operation, the upper base 201 drives the locking block 302 to move down synchronously, and the limiting plate 301 moves closer to the lower base 101. The telescopic rod 3 is compressed, and the first spring 303 also begins to store energy, which plays the role of reducing impact and smoothing the transition.

[0049] In this way, when the mold is fully closed, the limiting plate 301 fits tightly with the lower seat 101, the telescopic rod 3 reaches the compression limit, and the first spring 303 releases some energy to help maintain stable contact pressure between the upper and lower mold seats, thereby improving the uniformity and consistency of the drawing process.

[0050] Thus, when the drawing process is completed, the control system drives the upper die holder 2 to rise, the clamping block 302 disengages from the clamping slot 202, and the limiting plate 301 resets with the telescopic rod 3 under the action of the first spring 303, returning to its initial height, making it easier to remove the finished product and prepare for the next processing cycle.

[0051] In this way, when the entire drawing cycle is completed and repeated, the limiting and buffering structure not only improves the stability and safety of the mold operation, but also effectively extends the mold's service life and improves production efficiency and product quality.

[0052] refer to Figures 1 to 7 As shown, the upper end of the lower drawing die 103 is provided with a notch 104, and the upper end of the upper drawing die 203 is provided with a protrusion 204, which matches the notch 104.

[0053] It should be noted that when the mold begins to close, the upper drawing mold 203 moves downward with the upper mold base 2, and the protrusion 204 on its top gradually approaches and inserts into the recess 104 on the lower drawing mold 103.

[0054] In this way, the cooperation between the protrusion 204 and the notch 104 plays a guiding and positioning role, preventing the upper and lower molds from shifting or misaligning during the closing process, and improving the repeatability accuracy of mold closing.

[0055] When the mold is fully closed, the protrusion 204 is fully embedded in the recess 104, forming a stable forming cavity structure, which helps to improve the dimensional accuracy and surface consistency of the fender drawing process.

[0056] In this way, after the drawing is completed, the upper die holder 2 drives the upper drawing die 203 to rise, and the protrusion 204 disengages from the recess 104, providing a smooth separation path for the mold opening action;

[0057] In this way, when the entire drawing cycle is repeated, the convex-concave mating structure not only enhances the positioning stability of the die, but also effectively improves production efficiency and part qualification rate.

[0058] refer to Figures 1 to 7 As shown, the upper ends of the lower die holder 1 and the upper die holder 2 are respectively provided with a cross groove 5 and a circular groove 501. The upper ends of the lower drawing die 103 and the upper drawing die 203 are respectively fixedly connected with a cross block 502 and a circular block 503. The cross groove 5 matches the cross block 502, and the circular groove 501 matches the circular block 503.

[0059] It should be noted that when preparing to install or replace the lower drawing die 103, first align the cross block 502 on the lower drawing die 103 with the cross groove 5 on the lower die base 1, and then perform the insertion operation.

[0060] In this way, the design of the cross groove 5 and the cross block 502 ensures the rapid positioning of the drawing die 103 in the horizontal direction. Furthermore, due to the unique shape of the cross, it can effectively prevent the die from rotating during operation, thus ensuring the forming accuracy.

[0061] After the installation of the lower drawing die 103 is completed, the circular block 503 of the upper drawing die 203 is aligned and inserted into the circular groove 501 of the upper die holder 2 in the same manner.

[0062] In this way, the cooperation between the circular groove 501 and the circular block 503 not only provides a quick positioning function, but also makes installation more convenient due to the natural properties of the circular design. At the same time, it can withstand a certain lateral force, which enhances the stability of the overall structure of the mold.

[0063] In this way, during the mold closing process, the upper and lower drawing dies achieve close cooperation through their respective positioning structures, namely the cross groove 5 and the cross block 502, and the circular groove 501 and the circular block 503, ensuring the high consistency and accuracy of the closing position each time, thereby improving the consistency and quality of the product.

[0064] In this way, once the entire drawing process cycle is completed, the positioning structure also provides convenient conditions for quick disassembly and mold replacement, greatly shortening downtime and improving production efficiency.

[0065] refer to Figures 1 to 7 As shown, the upper end of the upper drawing die 203 is provided with a second vent hole 205, and the upper end of the lower drawing die 103 is provided with a first vent hole 105. The second vent hole 205 matches the first vent hole 105.

[0066] It should be noted that when the mold begins to close, the upper mold base 2 drives the upper drawing mold 203 to move downward, so that the second vent 205 gradually approaches and aligns with and connects with the first vent 105 on the lower drawing mold 103.

[0067] In this way, during the mold closing process, the compressed air inside the cavity can be smoothly discharged through the channel formed by the first vent hole 105 and the second vent hole 205, avoiding air accumulation that could cause surface defects or incomplete molding of the product.

[0068] When the drawing is completed and the pressure holding stage is entered, the vent holes remain open to ensure that the material flows fully under pressure and conforms to the mold surface, thereby further improving the forming quality.

[0069] In this way, when the mold is opened, the upper and lower vents are separated, which facilitates cleaning and maintenance and prevents residual gas from affecting the next molding effect;

[0070] In this way, when the entire drawing process is repeated, the venting structure not only effectively improves the forming quality, but also enhances the production adaptability and stability of the mold, making it especially suitable for forming fender parts with complex curved surfaces or deep cavity structures.

[0071] The working principle of the drawing die for fenders provided by this utility model is as follows:

[0072] In use, firstly, the lower drawing die 103 is inserted into the cross groove 5 of the lower die base 1 through the cross block 502 at its bottom to complete the positioning; the upper drawing die 203 is inserted into the round groove 501 of the upper die base 2 through the round block 503 at its bottom to complete the positioning; ensure that both are installed in place to prevent displacement, and place the metal sheet on the working surface of the lower drawing die 103; adjust the position to ensure that the material covers the entire forming area; check the alignment of the notch 104 and the protrusion 204 to prepare for mold closing, and control the equipment to drive the upper die base 2 to move downward; the upper drawing die 203 is pressed down accordingly, and the protrusion 204 is embedded in the notch 104 to achieve rapid positioning; the locking mechanism starts to work: the first sliding rod 401 slides in the through groove 4, driving the first conical block 402 and the second conical block 403 to extend and contact the mold mating surface; the locking components move synchronously: the triangular block 409 engages with the protruding block 410 to enhance the closing stability; The first vent 105 is connected to the second vent 205 to expel air from the cavity; the limiting plate 301 compresses the first spring 303 along with the telescopic rod 3, which plays a role in shock absorption and buffering. After the mold is fully closed, hydraulic or mechanical pressure is applied between the upper and lower molds; the sheet metal undergoes plastic deformation under pressure, conforming to the mold surface to form a fender shape; the venting system continues to work to ensure uniform material filling; the locking mechanism and locking assembly remain locked to prevent mold misalignment; the buffer assembly maintains stable pressure and improves molding consistency; the upper mold base 2 rises, driving the upper drawing mold 203 to disengage from the lower mold; the first sliding rod 401 retracts under the action of elastic force; the triangular block 409 disengages under the action of the third spring 408; the first spring 303 pushes the limiting plate 301 back to the initial position; the venting channel is disconnected to facilitate subsequent cleaning and maintenance; the formed fender is removed from the lower drawing mold 103 by manual or automated devices.

[0073] The above description is merely an embodiment of this utility model and does not limit the patent scope of this utility model. Any equivalent structural or procedural transformations made based on the content of this utility model specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this utility model.

Claims

1. A drawing die for a fender, characterized in that, include: Lower mold base (1); Upper mold base (2), which is connected to the upper end of lower mold base (1); A lower drawing die (103) is connected to the upper end of the lower die base (1); Upper drawing die (203), the upper drawing die (203) is connected to the lower end of the upper die holder (2); At least one set of locking mechanisms are provided, which are respectively disposed between the lower die base (1) and the lower drawing die (103) and the upper die base (2) and the upper drawing die (203). The locking mechanism includes a through groove (4), a first sliding rod (401), a first conical block (402), a second conical block (403), a second spring (404), a baffle (405), and a splitting assembly. The through groove (4) is respectively opened at the upper and lower ends of each set of lower die base (1) and lower drawing die (103) and upper die base (2) and upper drawing die (203). The first sliding rod (401) is slidably connected to the through groove. Inside the groove (4), the first conical block (402) is slidably connected to the circumferential surface of the first sliding rod (401), and the first conical block (402) matches the through groove (4). The second conical block (403) is fixedly connected to the side end of the first conical block (402). The second spring (404) is sleeved and connected to the circumferential surface of the first sliding rod (401), and its side end is connected to the first conical block (402). The baffle (405) is fixedly connected to the side end of the first sliding rod (401). The engaging assembly is set on the side end of the engaging mechanism to realize the separation and engagement of the lower mold base (1) and the upper mold base (2).

2. The drawing die for a fender as described in claim 1, characterized in that: The engaging assembly includes a mounting groove (406), a second sliding rod (407), a third spring (408), a triangular block (409), and a convex block (410). The mounting groove (406) is respectively opened on the side ends of the lower mold base (1) and the upper mold base (2). The second sliding rod (407) is slidably connected in the mounting groove (406). The third spring (408) is sleeved and connected to the circumferential surface of the second sliding rod (407). The triangular block (409) is fixedly connected to the side end of the second sliding rod (407). The convex block (410) is fixedly connected to the other side end of the first sliding rod (401). The convex block (410) matches the through groove (4). The triangular block (409) matches the first conical block (402), the second conical block (403), and the convex block (410) respectively.

3. The drawing die for a fender as described in claim 2, characterized in that: The lower mold base (1) is fixedly connected to the upper end of the lower mold base (1), and the upper mold base (2) is fixedly connected to the upper end of the upper mold base (2). The upper end of the upper mold base (201) is provided with a slot (202), and a locking block (302) is locked in the slot (202). The lower end of the locking block (302) is fixedly connected to a limiting plate (301). A telescopic rod (3) is connected between the limiting plate (301) and the lower mold base (101). A first spring (303) is sleeved and connected to the circumferential surface of the telescopic rod (3).

4. The drawing die for a fender as described in claim 1, characterized in that: The upper end of the lower drawing die (103) is provided with a notch (104), and the upper end of the upper drawing die (203) is provided with a protrusion (204), the protrusion (204) matching the notch (104).

5. The drawing die for a fender as described in claim 1, characterized in that: The upper ends of the lower die holder (1) and the upper die holder (2) are respectively provided with a cross groove (5) and a circular groove (501). The upper ends of the lower drawing die (103) and the upper drawing die (203) are respectively fixedly connected with a cross block (502) and a circular block (503). The cross groove (5) matches the cross block (502), and the circular groove (501) matches the circular block (503).

6. The drawing die for a fender as described in claim 1, characterized in that: The upper end of the upper drawing die (203) is provided with a second vent hole (205), and the upper end of the lower drawing die (103) is provided with a first vent hole (105). The second vent hole (205) matches the first vent hole (105).

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