Punching die with pre-fixing function

Abstract

The invention provides a punching die with a pre-fixing function, and relates to the technical field of punching, the punching die comprises a bottom plate, four sets of guide columns are arranged on the upper end face of the bottom plate, and a mounting plate is arranged on the upper end faces of the guide columns; the punching device further comprises a punching mechanism which comprises a vertical hydraulic cylinder, the vertical hydraulic cylinder is arranged on the upper end face of the mounting plate, the telescopic end of the vertical hydraulic cylinder is connected with a lifting plate, the lifting plate is slidably connected with the guide columns, a punching plate is arranged on the lower end face of the lifting plate, and the lower end face of the punching plate is connected with a pre-pressing plate. And four sets of pre-compression springs are arranged on the lower end face of the punching plate, the other ends of the pre-compression springs are fixedly connected with the upper end face of a pre-compression plate, and a forming groove is formed in the surface of the pre-compression plate. The whole-course stable fixing and positioning control of the workpiece in the whole punching machining process is achieved.

Description

Technical Field

[0001] This invention relates to the field of punching technology, and more specifically, to a punching die with a pre-fixed design. Background Technology

[0002] In current punching processes, traditional punching equipment and its associated die fixing systems generally suffer from insufficient fixing timeliness and poor fixing force continuity. These defects affect the accuracy and stability of punching. Traditional die fixing devices typically only activate the fixing process at the moment the punch is about to contact the workpiece, applying temporary pressure to the workpiece through a basic pressure plate mechanism. This passive, instantaneous fixing method has significant time lag and uneven fixing force. Due to the lag in fixing timing, the workpiece is in a free or semi-free state for most of the punching process, unable to obtain a continuous and stable constraint force. This makes the workpiece susceptible to various external disturbances such as vibration, inertial force, and cutting reaction force, resulting in slight displacement.

[0003] During the entire movement of a workpiece from its initial position to the target position directly below the punch in a punching machine, the lack of an effective pre-fixation and continuous constraint mechanism makes it highly susceptible to various forms of positional shifts and posture changes. This instability in positioning has become a key bottleneck affecting punching quality and production efficiency. During workpiece movement, factors such as the starting and stopping acceleration of the conveyor mechanism, the clearance fit of the guide device, and environmental vibrations all interfere with the workpiece's spatial position. This is especially true for thin-plate, small-sized, or irregularly shaped workpieces, which are more prone to flipping, slipping, and skewing due to their poor rigidity and unstable center of gravity. Even with instantaneous fixation using traditional pressure plates when the workpiece finally reaches the punch, the positional deviations caused by the workpiece's movement during operation are still significant. Deviating from the predetermined standard position introduces errors in the initial conditions of the punching operation, directly causing key quality indicators such as punching hole position, cutting edge size, and shape contour to deviate from design requirements. The cumulative effect of this positional deviation is particularly prominent in mass production, resulting in significant dimensional differences and shape inconsistencies between different batches and even within the same batch. This affects product interchangeability and assembly accuracy. The punching position deviation caused by positional offset can also trigger a chain reaction, including abnormal wear of the punch and die, uneven distribution of punching force, and shortened die life. This not only increases equipment maintenance costs but also frequently leads to production interruptions such as downtime for adjustment and rework, reducing the effective operating time of the equipment and overall production efficiency, and directly and negatively impacting the company's economic benefits and market competitiveness. Summary of the Invention

[0004] (a) Technical problems to be solved

[0005] In view of the problems existing in the prior art, the present invention provides a punching die with pre-fixed features to solve the technical problems mentioned in the background art.

[0006] (II) Technical Solution

[0007] To achieve the above objectives, the present invention provides the following technical solution: a pre-fixed punching die, comprising a base plate, four sets of guide pillars on the upper surface of the base plate, and an mounting plate on the upper surface of each guide pillar; further comprising a punching mechanism, the punching mechanism comprising a vertical hydraulic cylinder, the upper surface of the mounting plate comprising a vertical hydraulic cylinder, a lifting plate connected to the telescopic end of the vertical hydraulic cylinder, the lifting plate being slidably connected to the guide pillars, a stamping plate on the lower surface of the lifting plate, a pre-pressing plate connected to the lower surface of the stamping plate, four sets of pre-compression springs on the lower surface of the stamping plate, the other end of each pre-compression spring being fixedly connected to the upper surface of the pre-compression plate, and a forming groove being formed on the surface of the pre-compression plate; further comprising a pre-fixing mechanism, the pre-fixing mechanism comprising two sets, including a follower tube, the follower tube being disposed at the bottom of the die, two sets of connecting tubes being provided on the side wall of the follower tube, the other end of each connecting tube being connected to a negative pressure tube, the negative pressure tube penetrating the die.

[0008] Preferably, the upper surface of the base plate is provided with a transverse hydraulic cylinder, the telescopic end of the transverse hydraulic cylinder is connected to a mold, and the upper surface of the base plate is provided with two sets of slide rails, the mold being slidably connected to the slide rails.

[0009] Preferably, a limiting groove is formed on the surface of the mold, and a discharge groove is formed on the surface of the limiting groove.

[0010] Preferably, the bottom of the negative pressure tube is provided with a bottom groove, the connecting tube is connected to the bottom groove, the negative pressure tube is provided with a central tube, one end of the central tube is provided with a suction cup, the other end is provided with a bottom spring, and the other end of the bottom spring is fixedly connected to the bottom of the bottom groove.

[0011] Preferably, the follower tube is provided with a first fixed plate and a second fixed plate.

[0012] Preferably, a top tube is slidably connected inside the follower tube, a sliding sleeve is slidably connected to the end of the top tube, a top spring is sleeved on the outer surface of the top tube, one end of the top spring is connected to the side wall of the sliding sleeve, and the other end is fixedly connected to the side wall of the top tube, and two sets of edge plates adapted to the top tube are provided at one end of the upper surface of the bottom plate.

[0013] Preferably, the top tube surface is provided with a first piston disc, a second piston disc and a third piston disc, the first piston disc, the second piston disc and the third piston disc are all located inside the follower tube, and a return spring is provided between the second piston disc and the third piston disc, one end of the return spring is connected to the side wall of the second piston disc and the other end is connected to the side wall of the third piston disc.

[0014] Preferably, the first piston disc, the second piston disc, and the third piston disc are provided with side strips on one side, and the side strips are provided with two sets of negative pressure holes and two sets of back pressure holes, and the top tube sidewall is provided with multiple sets of side holes.

[0015] Preferably, a return pipe is connected through the other side of the first piston disc, the second piston disc, and the third piston disc. A follower rod is provided on the side wall of the third piston disc. The follower rod is slidably connected to the side wall of the follower pipe. A threaded rod is threadedly connected to the side wall of the follower pipe. A damping rod is connected to the side wall of the threaded rod. The damping rod is adapted to the return pipe.

[0016] Preferably, a first oil chamber is formed between the first piston disc and one end sidewall of the follower tube, a second oil chamber is formed between the third piston disc and the other end sidewall of the follower tube, a first negative pressure chamber is formed between the first fixed disc and the second piston disc, and a second negative pressure chamber is formed between the second fixed disc and the third piston disc.

[0017] (III) Beneficial Effects

[0018] Compared with the prior art, the present invention provides a punching die with pre-fixation, which has the following advantages: the punching die with pre-fixation function achieves stable fixation and positioning control of the workpiece throughout the entire punching process through the synergistic effect of the pre-fixation mechanism, the negative pressure control system and the buffer damping adjustment device.

[0019] The core of this punching die lies in establishing a continuous pre-fixing mechanism throughout the entire workpiece processing process. This overcomes the limitations of traditional punching equipment, which can only perform simple platen fixation at the final moment. Through a negative pressure adsorption system, the workpiece receives continuous and stable fixing force throughout the entire process from placement to completion of punching, thereby improving processing accuracy. When the die advances and triggers the pre-fixing mechanism, the complex piston system within the follower tube begins to work in coordination. Through displacement control of the first, second, and third piston discs, the sealing of the negative pressure chamber and the precise adjustment of the vacuum level are achieved. This multi-stage piston hierarchical control design makes the generation and maintenance of negative pressure more stable and reliable, avoiding the pressure fluctuations and leakage problems that are prone to occur in single-chamber systems.

[0020] This punching die utilizes a damping adjustment mechanism to optimize parameters for different workpiece materials and processing requirements, enhancing the equipment's versatility and production adaptability. The design of the damping rod and return pipe leverages the flow resistance of hydraulic oil to control the piston system's reset speed. When the end of the return pipe contacts the damping rod, the hydraulic oil flow rate is controlled, thereby extending the return spring's rebound time and the negative pressure maintenance time. This fluid-damped time control mechanism is more stable and reliable than traditional mechanical or electronic delay systems, less susceptible to external factors such as ambient temperature and electromagnetic interference, ensuring the consistency and repeatability of the fixed time. By rotating the threaded rod, operators can easily replace damping rods of different specifications to adjust the damping coefficient and set the fixed time.

[0021] The dual-chamber hydraulic balancing system achieves smooth piston movement control through pressure balancing and flow regulation between the first and second chambers. During the application of the fixed force, the buffering effect of the hydraulic oil prevents mechanical impact damage to the workpiece and mold; during the release of the fixed force, the damping control of the hydraulic oil ensures a smooth transition in workpiece release, preventing the workpiece from bouncing or displacing due to sudden release. This hydraulic buffering mechanism not only protects the surface quality of the workpiece but also extends the service life of the mold and equipment.

[0022] The design of the buffer mechanism of the preload plate and preload spring further optimizes the application process of the punching force. When the preload plate abuts against the upper end face of the die, the buffering effect of the preload spring makes the transmission of the punching force more stable and gradual, avoiding the adverse effects of sudden impact on the internal stress distribution of the workpiece, reducing the incidence of processing defects such as cracks and tears. The slide rail guide system ensures the accuracy and stability of the die movement, reduces the vibration and noise of the equipment operation, and improves the working environment conditions.

[0023] In summary, this punching die with pre-fixing function successfully solves the problems of unreliable workpiece fixation and unstable processing accuracy in traditional punching equipment, providing an effective solution for technological upgrading and quality improvement in the punching processing industry. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the overall structure of a pre-fixed punching die in this invention;

[0025] Figure 2 This is a schematic diagram of the vertical hydraulic cylinder and the stamping plate in this invention;

[0026] Figure 3 This is a schematic diagram of the structure of the stamping plate and the pre-pressing plate in this invention;

[0027] Figure 4 This is a schematic diagram of the transverse hydraulic cylinder and the base plate in this invention;

[0028] Figure 5 This is a schematic diagram of the structure of the follower tube and the jacking tube in this invention;

[0029] Figure 6 This is a cross-sectional view of the negative pressure pipe and the central pipe in this invention;

[0030] Figure 7 This is a cross-sectional view of the follower pipe and the jacking pipe in this invention;

[0031] Figure 8 This is a cross-sectional view of the follower rod and the third piston disk in this invention.

[0032] Figure 9 This is a cross-sectional view of the second piston disc and the top tube in this invention.

[0033] Figure 10 This is a cross-sectional view of the follower tube and the first fixed disk in this invention;

[0034] Figure 11 This is a cross-sectional view of the jacking pipe and edge plate in this invention.

[0035] In the diagram: 11. Base plate; 12. Guide column; 13. Mounting plate; 21. Vertical hydraulic cylinder; 22. Lifting plate; 23. Stamping plate; 24. Pre-pressure plate; 25. Pre-pressure spring; 26. Forming groove; 27. Horizontal hydraulic cylinder; 28. Mold; 29. ​​Slide rail; 31. Follower pipe; 32. Connecting pipe; 33. Negative pressure pipe; 34. Bottom groove; 35. Center pipe; 36. Suction cup; 37. Bottom spring; 38. First fixed plate; 39. Second fixed plate; 210. Limiting groove; 211. Discharge groove; 310. Jacking pipe; 311. Sliding sleeve; 312. Top spring; 313. Edge plate; 314. First piston disc; 315. Second piston disc; 316. Return spring; 317. Side strip; 318. Negative pressure hole; 319. Back pressure hole; 320. Side hole; 321. Return pipe; 322. Follower rod; 323. Threaded rod; 324. Damping rod; 325. First oil chamber; 326. Second oil chamber; 327. First negative pressure chamber; 328. Second negative pressure chamber; 329. Third piston disc. Detailed Implementation

[0036] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0037] It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0038] In this invention, unless otherwise stated, the directional terms such as "up" and "down" generally refer to the directions shown in the accompanying drawings, or to the vertical, perpendicular, or gravitational direction; similarly, for ease of understanding and description, "left" and "right" generally refer to the left and right shown in the accompanying drawings; "inner" and "outer" refer to the inner and outer contours of each component itself, but the above directional terms are not intended to limit this invention.

[0039] Please see Figures 1 to 11 A pre-fixed punching die includes a base plate 11, with four sets of guide pillars 12 on the upper surface of the base plate 11, and a mounting plate 13 on the upper surface of the guide pillars 12; it also includes a punching mechanism, which includes a vertical hydraulic cylinder 21. The vertical hydraulic cylinder 21 is located on the upper surface of the mounting plate 13, and a lifting plate 22 is connected to the telescopic end of the vertical hydraulic cylinder 21. The lifting plate 22 is slidably connected to the guide pillars 12, and a stamping plate 23 is located on the lower surface of the lifting plate 22. A pre-pressing plate is connected to the lower surface of the stamping plate 23. 24. The lower end face of the stamping plate 23 is provided with four sets of pre-compression springs 25. The other end of the pre-compression spring 25 is fixedly connected to the upper end face of the pre-compression plate 24. The surface of the pre-compression plate 24 is provided with a forming groove 26. The upper end face of the base plate 11 is provided with a transverse hydraulic cylinder 27. The telescopic end of the transverse hydraulic cylinder 27 is connected to a mold 28. The upper end face of the base plate 11 is provided with two sets of slide rails 29. The mold 28 is slidably connected to the slide rails 29. The surface of the mold 28 is provided with a limit groove 210. The surface of the limit groove 210 is provided with a discharge groove 211.

[0040] It also includes a pre-fixing mechanism, which has two sets, including a follower tube 31. The follower tube 31 is located at the bottom of the mold 28. The side wall of the follower tube 31 has two sets of connecting tubes 32. The other end of the connecting tube 32 is connected to a negative pressure tube 33. The negative pressure tube 33 passes through the mold 28. A bottom groove 34 is opened at the bottom of the negative pressure tube 33. The connecting tube 32 is connected to the bottom groove 34. A central tube 35 is provided in the negative pressure tube 33. A suction cup 36 is provided at one end of the central tube 35. A bottom spring 37 is provided at the other end. The other end of the bottom spring 37 is fixedly connected to the bottom of the bottom groove 34. A first fixing plate 38 and a second fixing plate 38 are provided in the follower tube 31. A fixed plate 39 is attached to a follower tube 31, and a top tube 310 is slidably connected inside the follower tube 31. A sliding sleeve 311 is slidably connected to the end of the top tube 310. A top spring 312 is fitted on the outer surface of the top tube 310. One end of the top spring 312 is connected to the side wall of the sliding sleeve 311, and the other end is fixedly connected to the side wall of the top tube 310. Two sets of edge plates 313 adapted to the top tube 310 are provided at one end of the upper surface of the base plate 11. A first piston disc 314, a second piston disc 315, and a third piston disc 329 are provided on the surface of the top tube 310. The first piston disc 314, the second piston disc 315, and the third piston disc 329 are all located inside the follower tube 31. A return spring 316 is provided between the first piston disc 314 and the third piston disc 329. One end of the return spring 316 is connected to the side wall of the second piston disc 315, and the other end is connected to the side wall of the third piston disc 329. A side strip 317 is provided on one side of the first piston disc 314, the second piston disc 315, and the third piston disc 329. Two sets of negative pressure holes 318 and two sets of back pressure holes 319 are opened on the surface of the side strip 317. Multiple sets of side holes 320 are opened on the side wall of the top tube 310. A return pipe 321 is connected through the other side of the first piston disc 314, the second piston disc 315, and the third piston disc 329. A follower is provided on the side wall of the third piston disc 329. The moving rod 322 is slidably connected to the side wall of the following tube 31. The side wall of the following tube 31 is threadedly connected to a threaded rod 323. The side wall of the threaded rod 323 is connected to a damping rod 324. The damping rod 324 is adapted to the return tube 321. A first oil chamber 325 is formed between the first piston disc 314 and one end side wall of the following tube 31. A second oil chamber 326 is formed between the third piston disc 329 and the other end side wall of the following tube 31. A first negative pressure chamber 327 is formed between the first fixed disc 38 and the second piston disc 315. A second negative pressure chamber 328 is formed between the second fixed disc 39 and the third piston disc 329.

[0041] During punching, the vertical hydraulic cylinder 21 is activated, and the telescopic end of the vertical hydraulic cylinder 21 pushes the lifting plate 22 to move downward. The downward movement of the lifting plate 22 causes the stamping plate 23 and the pre-pressing plate 24 to move downward synchronously. When the pre-pressing plate 24 abuts against the upper surface of the mold 28, the vertical hydraulic cylinder 21 continues to push the lifting plate 22 and the stamping plate 23 downward. At this time, the pre-pressing spring 25 is compressed, and the stamping plate 23 continues to press down to punch the workpiece fixed in the limiting groove 210 through the forming groove 26. After punching, the telescopic end of the vertical hydraulic cylinder 21 retracts, causing the punching mechanism to move upward as a whole. The punched workpiece falls to the upper surface of the bottom plate 11 through the discharge groove 211.

[0042] After punching, the scrap material in the limiting groove 210 needs to be removed, and a new workpiece can be placed on it. Then, the transverse hydraulic cylinder 27 is activated. The telescopic end of the transverse hydraulic cylinder 27 pushes the mold 28 outward along the slide rail 29 until the sliding sleeve 311 abuts against the side wall of the edge plate 313. At this time, the transverse hydraulic cylinder 27 stops pushing. The scrap material in the limiting groove 210 is removed, and a new workpiece is placed on it. Then, the transverse hydraulic cylinder 27 continues to advance forward. At this time, the top spring 312 is compressed. As the follower tube 31 continues to move forward, the top tube 310 begins to slide into the follower tube 31. The top tube 310 drives the first piston plate 314, the second piston plate 315, and the third piston plate 329 to move synchronously into the follower tube 31. At this time, the back pressure hole 319 is released. Except when connected to the connecting pipe 32, a vacuum is formed in the first negative pressure chamber 327 and the second negative pressure chamber 328, generating negative pressure until the negative pressure hole 318 connects with the connecting pipe 32. The negative pressure in the first negative pressure chamber 327 and the second negative pressure chamber 328 is transmitted to the negative pressure pipe 33 through the connecting pipe 32. The generation of negative pressure causes the suction cup 36 to tightly suck up the workpiece above through the central pipe 35. At the same time, the central pipe 35 moves down against the elastic force of the bottom spring 37 due to the negative pressure, and then abuts against the upper end face of the negative pressure pipe 33, exerting a downward pulling force on the workpiece above. When the top pipe 310 slides inward, the return spring 316 is compressed, and the air in the cavity between the second piston plate 315 and the second fixed plate 39 passes through the side hole 320 on the top pipe 310 along the top pipe 310. 10 is discharged, and at the same time, the air in the cavity between the first piston disc 314 and the first fixed disc 38 is also discharged along the top tube 310 through the side hole 320 on the top tube 310; when the top tube 310 slides into the follower tube 31, the hydraulic oil in the second oil chamber 326 enters the first oil chamber 325 through the return pipe 321. When the end of the return pipe 321 contacts the damping rod 324, the flow speed of the hydraulic oil is blocked and slowed down; after the suction cup 36 picks up the workpiece above, the transverse hydraulic cylinder 27 begins to return, the sliding sleeve 311 releases the abutment state with the edge plate 313, after the thrust disappears, the return spring 316 begins to slowly rebound, and the setting of the damping rod 324 can make the hydraulic oil in the first oil chamber 325 flow back into the second oil chamber 326. The slow speed extends the return time of the return spring 316, thus ensuring that the suction cup 36 remains firmly attached to the new workpiece before it is punched. When the back pressure hole 319 connects to the connecting pipe 32, the negative pressure disappears, and the suction force of the suction cup 36 on the new workpiece is released, thereby releasing the workpiece from the limiting groove 210. During this process, the cavity between the first piston plate 314 and the first fixed plate 38, as well as the cavity between the second piston plate 315 and the second fixed plate 39, increases. Air is drawn in from the outside through the side hole 320 on the top pipe 310, and the hydraulic oil in the first oil chamber 325 gradually flows back to the second oil chamber 326 through the return pipe 321. At this time, the pre-fixation and release of the punched workpiece are completed.The damping rod 324 is threadedly connected to the follower tube 31 via a threaded rod 323. When it is necessary to change the resistance, the threaded rod 323 can be rotated to remove the damping rod 324, and then a suitable damping rod 324 can be replaced.

[0043] Of all the solutions mentioned above, those involving the connection between two components can be selected according to the actual situation, such as welding, bolt and nut connection, bolt or screw connection, or other known connection methods, which will not be elaborated here. For all the fixed connections mentioned above, welding is preferred. Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A punching die with a pre-fixed base plate (11), characterized in that: The base plate (11) has four sets of guide columns (12) on its upper surface, and a mounting plate (13) is provided on the upper surface of the guide columns (12); it also includes a punching mechanism, which includes a vertical hydraulic cylinder (21). The upper surface of the mounting plate (13) is provided with the vertical hydraulic cylinder (21), and the telescopic end of the vertical hydraulic cylinder (21) is connected to a lifting plate (22). The lifting plate (22) is slidably connected to the guide columns (12), and the lower surface of the lifting plate (22) is provided with a stamping plate (23). The lower surface of the stamping plate (23) is connected to a pre-pressing plate (24). The lower end face of the stamping plate (23) is provided with four sets of pre-compression springs (25), the other end of the pre-compression springs (25) is fixedly connected to the upper end face of the pre-compression plate (24), and the surface of the pre-compression plate (24) is provided with forming grooves (26); it also includes a pre-fixing mechanism, which is provided with two sets, including a follower tube (31), the follower tube (31) is provided at the bottom of the mold (28), the side wall of the follower tube (31) is provided with two sets of connecting tubes (32), the other end of the connecting tube (32) is connected to a negative pressure tube (33), and the negative pressure tube (33) penetrates the mold (28).

2. A pre-fixed punching die according to claim 1, characterized in that: The upper surface of the base plate (11) is provided with a transverse hydraulic cylinder (27), the telescopic end of the transverse hydraulic cylinder (27) is connected to a mold (28), the upper surface of the base plate (11) is provided with two sets of slide rails (29), and the mold (28) is slidably connected to the slide rails (29).

3. A pre-fixed punching die according to claim 2, characterized in that: The mold (28) has a limiting groove (210) on its surface, and the limiting groove (210) has a discharge groove (211) on its surface.

4. A pre-fixed punching die according to claim 1, characterized in that: The bottom of the negative pressure tube (33) is provided with a bottom groove (34), the connecting tube (32) is connected to the bottom groove (34), the negative pressure tube (33) is provided with a central tube (35), one end of the central tube (35) is provided with a suction cup (36), the other end is provided with a bottom spring (37), and the other end of the bottom spring (37) is fixedly connected to the bottom of the bottom groove (34).

5. A pre-fixed punching die according to claim 4, characterized in that: The follower tube (31) is provided with a first fixed plate (38) and a second fixed plate (39).

6. A pre-fixed punching die according to claim 5, characterized in that: The follower tube (31) is slidably connected to the top tube (310), and the end of the top tube (310) is slidably connected to the sliding sleeve (311). The outer surface of the top tube (310) is fitted with a top spring (312). One end of the top spring (312) is connected to the side wall of the sliding sleeve (311), and the other end is fixedly connected to the side wall of the top tube (310). The upper end of the base plate (11) is provided with two sets of edge plates (313) that are adapted to the top tube (310).

7. A pre-fixed punching die according to claim 6, characterized in that: The surface of the top tube (310) is provided with a first piston disc (314), a second piston disc (315) and a third piston disc (329). The first piston disc (314), the second piston disc (315) and the third piston disc (329) are all located in the follower tube (31). A return spring (316) is provided between the second piston disc (315) and the third piston disc (329). One end of the return spring (316) is connected to the side wall of the second piston disc (315) and the other end is connected to the side wall of the third piston disc (329).

8. A pre-fixed punching die according to claim 7, characterized in that: The first piston disc (314), the second piston disc (315) and the third piston disc (329) are provided with side strips (317) on one side. The side strips (317) have two sets of negative pressure holes (318) and two sets of back pressure holes (319) on their surface. The top pipe (310) has multiple sets of side holes (320) on its side wall.

9. A pre-fixed punching die according to claim 8, characterized in that: The first piston disc (314), the second piston disc (315) and the third piston disc (329) are connected to a return pipe (321) on the other side. The third piston disc (329) is provided with a follower rod (322) on its side wall. The follower rod (322) is slidably connected to the side wall of the follower pipe (31). The follower pipe (31) is threadedly connected to a threaded rod (323) on its side wall. The threaded rod (323) is connected to a damping rod (324) on its side wall. The damping rod (324) is adapted to the return pipe (321).

10. A pre-fixed punching die according to claim 9, characterized in that: A first oil chamber (325) is formed between the first piston disc (314) and one end sidewall of the follower tube (31), a second oil chamber (326) is formed between the third piston disc (329) and the other end sidewall of the follower tube (31), a first negative pressure chamber (327) is formed between the first fixed disc (38) and the second piston disc (315), and a second negative pressure chamber (328) is formed between the second fixed disc (39) and the third piston disc (329).

Images