A continuous tube reducing die and a tube reducing method

Abstract

The application discloses a continuous pipe shrinking die and a pipe shrinking method, and relates to the technical field of pipe shrinking, in particular to a pipe shrinking die and a pipe shrinking method. The pipe shrinking die comprises a pipe shrinking die assembly, a sliding block, a sliding block seat and a three-jaw chuck, the three-jaw chuck can clamp a pipe and move towards the pipe shrinking die assembly, the pipe shrinking die assembly is externally sleeved with the sliding block, and the pipe in the pipe shrinking die assembly can be shrunk in diameter for multiple times through multiple movements of the sliding block outside the pipe shrinking die assembly; and one side is provided with a rotary driving assembly capable of driving the pipe shrinking die assembly to rotate. The pipe shrinking die and the pipe shrinking method can be used for continuously and multiple times shrinking the pipe in diameter, and can prevent the pipe from being deformed due to one-time shrinking; meanwhile, the pipe can be rotated through the rotary driving assembly during the pipe shrinking process, so that the pipe can be prevented from being extruded by the pipe shrinking die assembly and from being provided with a flash defect.

Description

Technical Field

[0001] This invention relates to the field of metal pipe processing technology, specifically to a continuous tube shrinking mold and tube shrinking method. Background Technology

[0002] Tube reduction is a crucial process in the forming of metal tubes, widely used in industries such as automotive, aerospace, construction, and home appliances. Current tube reduction technologies typically employ segmented, multi-pass tube reduction or use multi-lobed tube reduction molds for one-time forming.

[0003] However, in actual production, the existing tube shrinking process still has the following technical defects:

[0004] 1. Complex process and low efficiency: Traditional pipe shrinking molds can only complete one shrinking process at a time. For pipe fittings that require multi-stage shrinking, multiple sets of molds must be used and the molds must be changed multiple times, resulting in long production preparation time and low processing efficiency.

[0005] 2. Poor surface quality: Due to the need for multiple clamping and mold changes, the pipe is prone to surface damage such as scratches and indentations during repeated clamping, which affects the appearance and performance of the finished product.

[0006] 3. Coaxiality is difficult to guarantee: Multiple clamping and the accumulation of positioning errors between different molds make it difficult for the coaxiality of each diameter reduction section after multi-stage tube shrinking to meet the design requirements, which has an adverse effect on the subsequent assembly accuracy.

[0007] 4. Prominent flash defects: When ordinary eight-lobed tube shrinking molds are closed, there are often gaps or incomplete closure between the lobes, which causes material to be squeezed into the gaps during tube shrinking, forming flash, increasing the subsequent finishing process, and affecting the quality of the tube ends.

[0008] 5. Difficulty in forming pipe fittings with large diameter changes: For pipes with large diameter changes (such as large single diameter reduction or diameter reduction ratio exceeding the material forming limit), if multiple pipe shrinking processes are used, the pipe wall is prone to instability, wrinkling or even cracking and other deformation defects, resulting in low yield.

[0009] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0010] The technical problem to be solved by this invention is: how to provide a mold that can achieve continuous tube shrinking of pipes with large diameter changes without multiple mold changes.

[0011] To solve the above-mentioned technical problems, the present invention provides the following technical solution: A continuous tube shrinking die includes a tube shrinking die assembly, a slider, a slider seat, and a three-jaw chuck. The three-jaw chuck can clamp the tube and move it toward the tube shrinking die assembly. The slider is sleeved on the outside of the tube shrinking die assembly and is connected to the slider seat through an elastic element. The slider can shrink the diameter of the tube inside the tube shrinking die assembly multiple times by moving it multiple times outside the tube shrinking die assembly. A rotary drive assembly capable of driving the tube to rotate is provided on one side.

[0012] This application, by setting up a tube shrinking die assembly, a slider assembly, and a three-jaw chuck, allows for multiple diameter reductions of the tube fitting inside the tube shrinking die assembly by adjusting the slider's multiple movements outside the assembly. This application employs continuous multiple diameter reduction to prevent problems such as tube deformation caused by a single diameter reduction. Simultaneously, during the diameter reduction process, the rotation drive assembly can drive the three-jaw chuck and the connected tube fitting to rotate, thereby reducing flash defects caused by the tube being squeezed by the tube shrinking die assembly. This application allows for multiple continuous diameter reductions of the tube fitting with a single mold, eliminating the need for mold changes, and the use of the three-jaw chuck to clamp and move the tube ensures coaxiality during multiple diameter reductions.

[0013] As a further aspect of the present invention: the rotary drive assembly includes a support frame, a chuck tail seat is mounted on one side of the support frame, wherein the chuck tail seat is connected to a three-jaw chuck on the other side of the support frame, and a drive component for driving the chuck tail seat to rotate is provided on the support frame.

[0014] As a further aspect of the present invention: the driving component includes a driving rod and an upper mold connector. The bottom of the upper mold connector is movably connected to the driving rod. The end of the driving rod can press the chuck locking block provided on the chuck tail seat and drive the chuck tail seat to rotate.

[0015] As a further aspect of the present invention: a plurality of chuck locking blocks are installed in a circular array on the chuck tailstock.

[0016] As a further aspect of the present invention: the tube shrinking die assembly includes a die tail seat, a die core fixing plate and a plurality of die segments, wherein the die core fixing plate is installed on the die tail seat, two adjacent die segments are connected by an elastic element two, and one end of each die segment is connected to the die tail seat through the die core fixing plate by an elastic element one.

[0017] As a further aspect of the present invention: a plurality of slots are arranged in a ring array on the mold core fixing plate, and a locking block is installed at one end of the concave mold piece, wherein the locking block can be locked into the slots on the mold core fixing plate, and the elastic element on the locking block is connected to the concave mold tail seat.

[0018] As a further aspect of the present invention: a die component formed by several die segments has a small opening diameter at the end near the die tail seat and a large opening diameter at the end away from the die tail seat.

[0019] As a further aspect of the present invention, it also includes an upper template, the bottom of which is provided with an upper die wedge, wherein the downward movement of the upper die wedge can drive the slider to move outside the shrinking die assembly.

[0020] As a further aspect of the present invention: a cylinder is installed on one side of the rotary drive assembly, which can drive the rotary drive assembly to move toward or away from the tube shrinking die assembly.

[0021] This invention also discloses a tube shrinking method using a continuous tube shrinking die, comprising the following steps: S1. In the natural state, a force to the left is generated by rotating the drive assembly, so that both ends of the tube to be shrunken are tightly attached to the three-jaw chuck and the inner wall of the tube shrinking die assembly, respectively. S2. The three-jaw chuck and pipe fitting are rotated 10-20° by the rotary drive assembly and then the rotation stops. S3. The rear drive slider moves within the slider seat, the slider extrudes and compresses the tube die assembly to shrink, and extrudes the tube opening to reduce its diameter. The diameter reduction of the tube opening is 1-3mm in one step. S4. The rear slider resets, the tube shrinking die assembly opens, and the tube continues to move to the left under the pulling force of the rotation drive assembly, once again pressing against the inner wall of the tube shrinking die assembly. S5. Subsequently, the three-jaw chuck and pipe fitting are rotated 10-20° again by the rotary drive assembly and then the rotation stops. S6. Then drive the slider to move within the slider seat. The distance the slider moves in this step is greater than the distance the slider moves in step S3. Subsequently, the slider squeezes the tube die assembly to shrink and squeezes the tube opening for secondary diameter reduction. The primary diameter reduction of the tube opening is 1-3mm. S7. Similarly, perform multiple diameter reductions until the required size is achieved. S8. When the final reduction is completed, the rotary drive assembly generates a force to the right, removing the tube from the tube reduction die assembly.

[0022] Compared with the prior art, the beneficial effects of the present invention are: Firstly, this application sets up a tube shrinking die assembly, a slider assembly, and a three-jaw chuck. By adjusting the slider to move multiple times outside the tube shrinking die assembly, the tube inside the tube shrinking die assembly can be reduced in diameter multiple times. This application adopts continuous multiple diameter reduction to prevent problems such as tube deformation caused by single diameter reduction. At the same time, during the diameter reduction process, the rotation drive assembly can drive the three-jaw chuck and the connected tube to rotate, thereby reducing the flash defects caused by the tube being squeezed by the tube shrinking die assembly. This application can realize multiple continuous diameter reduction of the tube with one set of molds without changing the mold, and the coaxiality of multiple diameter reductions is ensured by using the three-jaw chuck to hold and move the tube. Secondly, during each feeding and before extrusion, this application drives the chuck tail seat to rotate via the drive rod, thereby causing the tube to rotate 10-20° within the die. This design ensures that each area of ​​the tube is evenly stressed, preventing the gap between adjacent die segments from squeezing the tube and causing embossing. This design in this application can make the tube diameter reduction dimension uniform and the surface finish good. Finally, this application involves multiple consecutive diameter reductions of the pipe fitting, so the amount of pressure exerted by the die on the pipe fitting during each diameter reduction is less, thus preventing defects such as dents and flash from occurring during the diameter reduction process. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the continuous tube shrinking mold according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the upper template moving upwards in the continuous tube shrinking mold according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the rotary drive assembly and the three-jaw chuck according to an embodiment of the present invention; Figure 4 This is an exploded view of the tube shrinking die assembly according to an embodiment of the present invention; Figure 5 This is an exploded view of the continuous tube shrinking mold according to an embodiment of the present invention; Figure 6 This is a partial structural schematic diagram of the continuous tube shrinking mold according to an embodiment of the present invention; Explanation of reference numerals in the attached figures: 1. Download the template; 2. Tube shrinking die assembly; 21. Die tailstock; 22. Die core fixing plate; 23. Slot; 24. Die flap; 25. Block; 26. Elastic element one; 27. Elastic element two; 3. Slider; 4. Slider seat; 41. Elastic element three; 5. Upper template; 51. Upper mold wedge block; 6. Cylinder; 7. Rotary drive assembly; 71. Chuck locking block; 72. Drive rod; 73. Support frame; 74. Upper die connector; 75. Chuck tailstock; 8. Pipe fittings; 9. Three-jaw chuck; 10. Guide rails. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Example 1 Reference Figure 1 A continuous tube shrinking die includes a lower template 1 and a tube shrinking die assembly 2, a slider 3, a slider seat 4, a cylinder 6, a rotary drive assembly 7, a tube fitting 8, a three-jaw chuck 9, and a guide rail 10 mounted on the lower template 1. It also includes an upper template 5 located above the lower template 1, which can be driven to move toward the lower template 1 using a continuous punch press.

[0026] Reference Figure 1 , Figure 2 , Figure 4 and Figure 5 The shrinking die assembly 2 includes a die tail seat 21, a die core fixing plate 22, a slot 23, a die flap 24, a locking block 25, an elastic element 1 26, and an elastic element 27. The die tail seat 21 is fixed to the lower template 1 by bolts or pins. The die core fixing plate 22 is installed on the die tail seat 21 by bolts or pins. The die core fixing plate 22 is a disc-shaped structure with several slots 23 arranged in a ring array on it. The slots 23 can penetrate the die core fixing plate 22.

[0027] A die component is installed on the side of the die core fixing plate 22 away from the die tail seat 21. The die component includes several die segments 24. Adjacent die segments 24 are connected by an elastic element 27. Each die segment 24 has a locking block 25 at its end. An elastic element 26 is installed on the locking block 25. The locking block 25 at the end of the die segment 24 can be locked into the locking groove 23. The other end of the elastic element 26 passes through the locking groove 23 and is connected to the die tail seat 21. Both the elastic element 26 and the elastic element 27 can be springs.

[0028] It should be noted that the die part formed by several die segments 24 has a larger outer diameter and a smaller inner diameter at the end of the die part closer to the die tail 21; and a smaller outer diameter and a larger inner diameter at the end of the die part farther away from the die tail 21. Therefore, when the tube 8 is inserted into the die part, the more it moves to the left (i.e., closer to the die tail 21), the smaller its inner diameter becomes, thus achieving the diameter reduction treatment of the tube 8.

[0029] There is an installation gap between several die segments 24. When two adjacent die segments 24 are in close contact and there is no gap, the diameter of the tube opening inside the die is at its minimum. In order to adjust the diameter of the inner tube opening of the die, a slider 3 can be sleeved on the outside of the die, and the diameter of the inner tube opening can be adjusted by moving the slider 3.

[0030] For ease of understanding and description, Figure 4 The example of six concave mold petals 24 is used for illustration. It should be understood that this number is set only for the convenience of description and understanding, and should not be construed as a limitation of this application.

[0031] It should be noted that the number of concave mold segments 24 is the same as the number of slots 23 on the mold core fixing plate 22, and each concave mold segment 24 has a corresponding slot 23.

[0032] Reference Figure 1 and Figure 5 The slider seat 4 has an overall "U" shape structure. It is detachably mounted to the lower template 1 via bolts or pins. Grooves for placing the shrinking die assembly 2 are provided on both sides of the slider seat 4. The slider 3 is installed inside the slider seat 4, with one side connected to the slider seat 4 via an elastic element 41. A through hole is provided in the middle of the slider 3, which is fitted onto the outside of the shrinking die assembly 2. The side of the slider 3 facing away from the elastic element 41 is inclined, meaning the side of the slider 3 is narrower at the top and wider at the bottom. An upper die wedge 51 is provided at the bottom of the upper template 5, located directly above the slider seat 4. When the upper template 5 moves the upper die wedge 51 downwards, it engages the upper die wedge 51 between the slider 3 and the slider seat 4. During continuous descent, it continuously pushes the slider 3 towards the die tailstock 21 (i.e., to the left, see reference). Figure 1 As the die moves, the gap between two adjacent die lobes 24 continuously decreases, and the inner diameter of the die part also continuously decreases. In this process, the diameter reduction of the tube part 8 can be achieved.

[0033] Reference Figure 2 and Figure 3 The rotary drive assembly 7 includes a chuck locking block 71, a drive rod 72, a support frame 73, an upper mold connector 74, and a chuck tail seat 75. The bottom of the support frame 73 is slidably connected to the guide rail 10 provided on the lower mold plate 1. A cylinder 6 is also installed on the lower mold plate 1. The output end of the cylinder 6 is connected to the support frame 73. The cylinder 6 can drive the support frame 73 to move along the guide rail 10.

[0034] Reference Figure 3 A three-jaw chuck 9 is installed on the side of the support frame 73 facing the tube shrinking die assembly 2. The three-jaw chuck 9 is used to clamp the tube 8 and is a conventional clamping device in the field. Therefore, its principle and structure will not be described in detail in this application. A chuck tail seat 75 is installed on the other side of the support frame 73 away from the tube shrinking die assembly 2. The chuck tail seat 75 is connected to the three-jaw chuck 9 and rotates synchronously with the three-jaw chuck 9. Several chuck locking blocks 71 are installed in a circular array on the chuck tail seat 75. The number of chuck locking blocks 71 is not limited in this application and is determined according to actual needs.

[0035] To ensure coaxiality during multiple pipe diameter reductions, the three-jaw chuck 9, chuck tailstock 75, and die are coaxially arranged in this application.

[0036] A top mold connector 74 is provided on the top of the support frame 73 and is connected to the upper mold plate 5. The bottom of the upper mold connector 74 is movably connected to a drive rod 72. When the upper mold plate 5 moves down, it can first drive the upper mold connector 74 and the drive rod 72 to move down. During the downward movement, the drive rod 72 can push the chuck locking block 71 located directly below the drive rod 72, thereby driving the entire chuck tail seat 75 to rotate about 10-20°. Since the drive rod 72 is movably connected to the upper mold connector 74, when the upper mold plate 5 continues to move down, the drive rod 72 can be offset to the outside closest to the chuck locking block 71, thereby preventing it from affecting the continuous downward movement of the upper mold plate 5.

[0037] Example 2 This embodiment, based on Embodiment 1, claims protection for a tube-shrinking method using a continuous tube-shrinking die. The die in this application can be used on a continuous punch press; specifically, it includes the following steps: S1. Connect one end of the pipe fitting 8 to the three-jaw chuck 9. In the natural state, the cylinder 6 drives the three-jaw chuck 9 to generate a force to the left, so that the end of the pipe fitting 8 that needs to be shrunken is tightly attached to the inner wall of the shrunken die assembly 2. It should be noted that the left and right directions here are... Figure 1 Based on this, the direction is set for ease of description and should not be construed as a limitation of this application; S2. The upper template 5 moves downward under the action of the punch. At this time, the upper template 5 first contacts the upper die connector 74 and drives the drive rod 72 to move downward and push the chuck locking block 71, thereby driving the chuck tail seat 75 to rotate, and then driving the three-jaw chuck 9 and the pipe 8 to rotate 10-20° and then stop rotating. That is, pushing the chuck locking block 71 once, the chuck tail seat 75 rotates about 10-20°. During the extrusion and reduction of diameter, a raised mark will be generated at the gap between adjacent die segments 24. If the diameter is reduced multiple times, the raised mark will become larger and larger, thus affecting the quality of the end of the pipe fitting 8. To solve this problem, this application sets the chuck tail seat 75 to drive the pipe fitting 8 to rotate each time the diameter is reduced. Each rotation is about 10-20°, which can rotate the raised mark at the previous diameter reduction point into the die segment 24. Therefore, the raised mark generated at the gap between adjacent die segments 24 each time the diameter is reduced is not in the same place, which can prevent the raised mark from becoming larger and larger and affecting the quality of the pipe fitting 8. S3. The upper mold plate 5 continues to move down. At this time, the upper mold wedge block 51 moves between the slider 3 and the slider seat 4. As the upper mold wedge block 51 moves down along the slider 3, it will push the slider 3 to move to the left. When the slider 3 moves, it will squeeze and compress several concave mold petals 24 to shrink, thereby reducing the gap between adjacent concave mold petals 24, thus reducing the diameter of the pipe end of the pipe fitting 8. Each time the diameter is reduced, the diameter of the pipe end is reduced by 1-3mm. The size of each reduction should not be too large, so as to prevent deformation of the pipe end during one-time molding, which will also affect the quality of the pipe fitting. S4. After the first reduction is completed, the upper template 5 moves upward, the slider 3 is reset under the action of the elastic element 3 41, and the tube reduction die assembly 2 opens under the action of the elastic element 1 26 and the elastic element 27. Then, the tube 8 continues to move to the left under the pulling force of the rotation drive assembly 7, and once again closely adheres to the inner wall of the tube reduction die assembly 2. At this time, the distance to the left of the tube 8 is greater than the distance during the first reduction (step S1), so as to perform the second reduction.

[0038] S5. Subsequently, the upper template 5 moves down again under the action of the punch. At this time, the upper template 5 first contacts the upper die connector 74 and drives the drive rod 72 to move down and push the chuck locking block 71, thereby driving the chuck tail seat 75 to rotate, and then driving the three-jaw chuck 9 and the pipe 8 to rotate 10-20° and then stop rotating. That is, pushing the chuck locking block 71 once, the chuck tail seat 75 rotates about 10-20°. S6. Then the upper template 5 continues to move down. At this time, the upper mold wedge 51 moves between the slider 3 and the slider seat 4. As the upper mold wedge 51 moves down along the slider 3, it will push the slider 3 to move to the left. When the slider 3 moves, it will squeeze and compress several concave mold pieces 24 to shrink, thereby reducing the gap between adjacent concave mold pieces 24 and thus reducing the diameter of the pipe end of the tube 8. It should be noted that the distance that slider 3 moves in this step is greater than the distance that slider 3 moves in step S3; S7. Similarly, perform multiple diameter reductions until the required size is achieved. S8. When the final reduction is completed, the rotary drive assembly 7 generates a force to the right, removing the tube from the tube reduction die assembly 2. It should be noted that the number of times the pipe is reduced is generally set according to the pipe wall thickness, pipe diameter and reduction coefficient, and the frequency of each punching operation is set according to the number of times the pipe is reduced. For example, if the diameter of the pipe is reduced from 100mm to 80mm, it can be reduced ten times, each time by 2mm. Using a continuous punching machine, a single reduction can be completed in one second, which greatly saves the reduction time and ensures the quality of the reduction.

[0039] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A continuous tube shrinking die, characterized in that, The assembly includes a tube shrinking die assembly (2), a slider (3), a slider seat (4), and a three-jaw chuck (9). The three-jaw chuck (9) can clamp the tube and move it toward the tube shrinking die assembly (2). The slider (3) is sleeved on the outside of the tube shrinking die assembly (2), and the slider (3) is connected to the slider seat (4) through an elastic element (26). The slider (3) can shrink the tube inside the tube shrinking die assembly (2) multiple times by moving it outside the tube shrinking die assembly (2). A rotary drive assembly (7) that can drive the three-jaw chuck (9) to rotate is provided on one side.

2. The continuous tube shrinking die according to claim 1, characterized in that: The rotary drive assembly (7) includes a support frame (73), on one side of which a chuck tailstock (75) is mounted, wherein the chuck tailstock (75) is connected to a three-jaw chuck (9) on the other side of the support frame (73), and the support frame (73) is provided with a drive component for driving the chuck tailstock (75) to rotate.

3. A continuous tube shrinking die according to claim 2, characterized in that: The driving component includes a driving rod (72) and an upper mold connector (74). The bottom of the upper mold connector (74) is movably connected to the driving rod (72). The end of the driving rod (72) can press the chuck locking block (71) provided on the chuck tail seat (75) and drive the chuck tail seat (75) to rotate.

4. A continuous tube shrinking die according to claim 3, characterized in that: The chuck tailstock (75) is equipped with a number of chuck locking blocks (71) arranged in a ring array.

5. A continuous tube shrinking die according to claim 1, characterized in that: The shrinking die assembly (2) includes a die tail seat (21), a die core fixing plate (22) and a plurality of die segments (24), wherein the die core fixing plate (22) is installed on the die tail seat (21), two adjacent die segments (24) are connected by an elastic element two (27), and one end of each die segment (24) is connected to the die tail seat (21) through the die core fixing plate (22) via an elastic element one (26).

6. A continuous tube shrinking die according to claim 5, characterized in that: The mold core fixing plate (22) has several slots (23) arranged in a ring array. One end of the concave mold petal (24) is equipped with a locking block (25), wherein the locking block (25) can be locked into the slot (23) on the mold core fixing plate (22), and the elastic element (26) on the locking block (25) is connected to the concave mold tail seat (21).

7. A continuous tube shrinking die according to claim 5, characterized in that: The die part formed by several die segments (24) has a small opening diameter at the end near the die tail (21) and a large opening diameter at the end away from the die tail (21).

8. A continuous tube shrinking die according to claim 1, characterized in that: It also includes an upper template (5), the bottom of which is provided with an upper mold wedge (51), wherein the upper mold wedge (51) can drive the slider (3) to move outside the tube shrinking die assembly (2) when it moves down.

9. A continuous tube shrinking die according to claim 1, characterized in that: A cylinder (6) is installed on one side of the rotary drive assembly (7), which can drive the rotary drive assembly (7) to move toward or away from the tube shrinking die assembly (2).

10. A tube-shrinking method using a continuous tube-shrinking die as described in any one of claims 1-9, characterized in that, Includes the following steps: S1. In the natural state, the rotation drive assembly (7) generates a force to the left, so that the two ends of the tube to be shrunken are respectively pressed against the inner wall of the three-jaw chuck (9) and the tube shrinking die assembly (2); S2. The three-jaw chuck (9) is driven by the rotary drive assembly (7) to rotate the pipe fitting by 10-20° and then stops rotating. S3. The rear drive slider (3) moves in the slider seat (4). The slider (3) squeezes the compression tube die assembly (2) to shrink and squeezes the tube opening to reduce the diameter. The diameter of the tube opening is reduced by 1-3mm in one step. S4. The rear slider (3) is reset, the tube shrinking die assembly (2) opens, and the tube continues to move to the left under the pulling force of the rotation drive assembly (7), and once again closely adheres to the inner wall of the tube shrinking die assembly (2); S5. Subsequently, the three-jaw chuck (9) is driven by the rotary drive assembly (7) to rotate the pipe fitting by 10-20° and then stop rotating. S6. Then drive the slider (3) to move in the slider seat (4). The distance the slider (3) moves in this step is greater than the distance the slider moves in step S3. Then the slider (3) squeezes the concave die assembly (2) to shrink and squeezes the pipe opening to perform secondary diameter reduction. The first diameter reduction of the pipe opening is 1-3mm. S7. Similarly, perform multiple diameter reductions until the required size is achieved. S8. When the final reduction is completed, the rotary drive assembly (7) generates a force to the right to remove the tube from the tube reduction die assembly (2).

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