A mold and method for flanging the end of a thin tube

Abstract

The present invention discloses a mold and method for flanging the port of a thin pipe fitting. The present invention relates to the technical field of flanging the bottom port of a thin pipe fitting. The mold comprises an upper mold and a lower mold. The lower mold comprises a base, a lower pad, and a concave mold plate that are fixedly connected from bottom to top. A concave cavity is provided on the top surface of the concave mold plate. A first punch fixedly provided on the top surface of the lower pad is provided in the concave cavity. An arc-shaped groove is provided on the top surface of the first punch. An arc-shaped protrusion is fixedly provided at the bottom of the arc-shaped groove. The upper mold comprises an upper support, a connecting plate, and an upper pad that are fixedly connected from top to bottom. The top surface of the upper support is fixedly provided on the punching head of a punching machine. A limit plate and a discharge plate that are fixedly connected in sequence are provided below the upper pad. The beneficial effects of the present invention are: greatly improving the efficiency of flanging the bottom port of a thin pipe fitting and improving the quality of flanging the bottom port of a thin pipe fitting.

Description

Technical Field

[0001] The present invention relates to the technical field of flanging the bottom end of a thin tube, and in particular to a mold and a method for flanging the end of a thin tube. Background Art

[0002] The structure of a produced strip is as follows Figure 1~Figure 2 As shown, it includes a long thin plate 1, and a plurality of thin tubes 2 are formed on the bottom surface of the long thin plate 1 and spaced along its length. The thin tubes 2 are fixedly connected to the long thin plate 1. The bottom and top ports of the thin tubes 2 are both connected to the outside world. The length of the thin tubes 2 is 8mm, and the inner diameter of the thin tubes 2 is 1.5mm. The process requires that the bottom ends of each thin tube 2 on the strip are turned inward at a certain angle, and the flanging direction is as follows: Figure 2 As shown by the arrow in the middle, the bottom end of the thin tube 2 has a certain curvature, and the structure of the thin tube 2 after the inner flange is as follows Figure 3 As shown, the strip can only be provided to customers for use after all the thin tubes 2 on the strip are turned inward.

[0003] Because the length and inner diameter of the thin tubular members 2 are very small, it is impossible to perform inward bends on the bottom ends of the thin tubular members 2 using a fitter. [The reason is that the thin tubular members 2 are so small that there is no dedicated clamp to stably clamp them, and thus it is impossible to perform bends on the inner ends of the thin tubular members 2 using a dedicated tool.] Therefore, a mold and method are urgently needed to be able to perform inward bends on the bottom ends of each thin tubular member 2 on the strip. Summary of the Invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a mold and method for flanging the bottom end of a thin tube, which greatly improves the efficiency and quality of flanging the bottom end of the thin tube.

[0005] The objectives of the present invention are achieved through the following technical solutions: A mold for flanging the end of a thin tube, comprising an upper mold and a lower mold, wherein the lower mold comprises a base, a lower pad, and a concave mold plate that are integrally connected in sequence from bottom to top, wherein a concave cavity is formed on the top surface of the concave mold plate, wherein a first convex mold fixed to the top surface of the lower pad plate is disposed in the concave cavity, wherein an arc-shaped groove is formed on the top surface of the first convex mold, and an arc-shaped protrusion is fixed to the bottom of the arc-shaped groove;

[0006] A rectangular rod is fixedly provided in the concave cavity of the concave template and on its left and right side walls. Sliders are slidably sleeved on the two rectangular rods. The two slides are respectively located on the left and right sides of the first punch. A horizontal spring is sleeved on the two rectangular rods. The two ends of the horizontal spring are respectively fixed on the inner wall of the concave cavity and the slide. A semicircular hole located above the first punch is provided on the inner end surface of the two slides. An inclined surface is provided on the outer ends of the two slides. A first vertical spring is fixed in the base. The top end of the first vertical spring is fixedly connected to a first force transmission rod. The first force transmission rod passes through the lower pad and the concave template in sequence upward.

[0007] The upper die includes an upper support, a connecting plate, and an upper pad that are sequentially connected together from top to bottom. The top surface of the upper support is fixed to the punching head of the punching machine. A limit plate and a stripper plate that are sequentially connected together are provided below the upper pad. A gap A is formed between the limit plate and the upper pad. The stripper plate is fixed to the top end of the first force transmission rod. A gap B is formed between the bottom surface of the stripper plate and the top surface of the concave die plate.

[0008] Two inserting plates are fixed on the bottom surface of the connecting plate, and the two inserting plates sequentially penetrate the upper pad, the limit plate and the unloading plate downward, and the wedge-shaped surfaces of the two inserting plates are respectively located directly above the two inclined surfaces of the two sliders;

[0009] A fixing rod is fixed on the bottom surface of the connecting plate, which passes through the connecting plate, the upper pad and the limit plate in sequence and extends into the unloading plate. A second punch is fixed on the bottom surface of the fixing rod. A conical groove matching the arc-shaped protrusion is provided on the bottom surface of the second punch. The outer diameter of the second punch is equal to the inner diameter of the thin tube.

[0010] The lower pad and the base are detachably connected to each other via bolts.

[0011] The two slide blocks are arranged symmetrically with respect to the first punch.

[0012] A blind groove is provided in the outer end surface of the slider, and the blind groove of the slider is sleeved on the rectangular rod.

[0013] The diameter of the semicircular hole is equal to the outer diameter of the thin tube.

[0014] A pressing insert is fixed in the stripper plate, the bottom end of the fixing rod extends into the inner cavity of the pressing insert, and the second punch is located in the inner cavity of the pressing insert.

[0015] A method for flanging an end of a thin tube, comprising the following steps:

[0016] S1. The strip is pulled from front to back into the area surrounded by the unloading plate and the concave plate through the pulling mechanism, and it is ensured that the first thin tube on the strip is directly below the inner cavity of the press insert;

[0017] S2. Control the punching head of the punching machine to move downward, the punching head drives the upper support to move downward, the upper support drives the connecting plate and the upper pad to move downward synchronously, and then drives the fixed rod, the second punch and the two inserts to move downward synchronously relative to the stationary stripper plate, wherein the wedge-shaped surfaces of the two inserts move toward the inclined surfaces of the two sliders respectively, and the second punch gradually extends into the inner hole of the thin tube;

[0018] When the bottom surface of the upper pad contacts the top surface of the limit plate, the wedge-shaped surfaces of the two insert plates are located directly above the inclined surfaces of the two sliders. At the same time, the second punch just extends into the inner hole of the thin tube, and the distance between the bottom surface of the second punch and the bottom surface of the thin tube is 0.6 mm.

[0019] S3. As the punching head of the punching machine continues to move downward, the punch drives the upper support to continue to move downward, and the upper support drives the connecting plate, the upper pad, the limit plate and the stripper plate to move downward synchronously relative to the stationary concave plate, thereby driving the fixed rod, the second punch and the two insert plates to move downward synchronously relative to the stationary concave plate. The stripper plate also presses down the long thin plate and thin pipe with the material;

[0020] When the upper support moves downward for a certain distance, the wedge-shaped surfaces of the two inserting plates contact the inclined surfaces of the two sliders respectively, and at the same time, the lower end of the thin tube enters the area surrounded by the semicircular holes of the two sliders;

[0021] S4. As the punching head of the punching machine continues to move downward, the punch drives the upper support to continue to move downward, and the upper support drives the connecting plate, the upper pad, the limit plate and the stripper plate to move downward synchronously relative to the stationary concave plate, thereby driving the fixed rod, the second punch and the two insert plates to move downward synchronously relative to the stationary concave plate. The stripper plate continues to press the long thin plate and thin pipe with the material downward. At the same time, the two insert plates push the two sliders inward respectively, so that the semicircular holes of the two sliders move toward the thin pipe.

[0022] When the upper support moves downward for a certain distance, the inner end surfaces of the two inserting plates contact the inner end surfaces of the two sliders respectively. At the same time, the inner walls of the semicircular holes of the two sliders contact the outer wall of the thin tube to protect the outer wall of the thin tube.

[0023] S5. As the punching head of the punching machine continues to move downward, the punch drives the upper support to continue to move downward, and the upper support drives the connecting plate, the upper pad, the limit plate and the stripper plate to move downward synchronously relative to the stationary concave plate, thereby driving the fixing rod, the second punch and the two insert plates to move downward synchronously relative to the stationary concave plate, and the stripper plate continues to press the long thin plate and the thin tube with material downward, wherein, when the tapered groove of the second punch gradually matches with the arc-shaped protrusion of the first punch, the bottom end of the thin tube gradually turns inward, and when the tapered groove and the arc-shaped protrusion are fully matched, the bottom end of the thin tube is finally turned inward, thereby completing the inner turning of the bottom end of the thin tube;

[0024] S6. The worker repeats the operations of steps S2 to S5 to turn the bottom ends of all the thin tubes 2 on the strip inward.

[0025] The present invention has the following advantages: greatly improving the efficiency of flanging the bottom end of a thin tube piece and improving the quality of flanging the bottom end of the thin tube piece. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The structural diagram of a certain strip material;

[0027] Figure 2 for Figure 1 CC cross-sectional view;

[0028] Figure 3 This is a schematic diagram of the structure of the thin tube after inner flanging;

[0029] Figure 4 It is a structural schematic diagram of the present invention;

[0030] Figure 5 for Figure 4 A partial enlarged view of the D portion;

[0031] Figure 6 Schematic diagram of the structure of the first punch;

[0032] Figure 7 for Figure 6 A partial enlarged view of part E;

[0033] Figure 8 It is a structural diagram of the slider;

[0034] Figure 9 for Figure 8 A top view of

[0035] Figure 10 Schematic diagram of the connection between the fixed rod and the second punch;

[0036] Figure 11 for Figure 10 A partial enlarged view of part F;

[0037] Figure 12 Schematic diagram of the structure of the plugboard;

[0038] Figure 13 Schematic diagram of the structure of the press insert;

[0039] Figure 14 This is a schematic diagram showing that the first thin tube on the strip is located directly below the inner cavity of the press insert;

[0040] Figure 15 for Figure 14 A partial enlarged view of the G section;

[0041] Figure 16 is a schematic diagram of the second punch extending into the inner hole of the thin tube;

[0042] Figure 17 for Figure 16 A partial enlarged view of the H part;

[0043] Figure 18 A schematic diagram of the lower end of the thin tube entering the area surrounded by the semicircular holes of the two sliders;

[0044] Figure 19 for Figure 18 A partial enlarged view of the J part;

[0045] Figure 20 Schematic diagram showing that the inner walls of the semicircular holes of the two sliders are in contact with the outer wall of the thin tube;

[0046] Figure 21 for Figure 20 A partial enlarged view of the M part;

[0047] Figure 22 A schematic diagram of turning the bottom end of a thin tube inward;

[0048] Figure 23 for Figure 22 N partial enlarged views;

[0049] Figure 24 for Figure 23 A partial enlarged view of the P part;

[0050] In the picture:

[0051] 1-long thin plate, 2-thin tube;

[0052] 3-base, 4-lower plate, 5-concave template, 6-first punch, 7-arc groove, 8-arc protrusion, 9-rectangular rod, 10-slider, 11-horizontal spring, 12-semicircular hole, 13-inclined surface, 14-first vertical spring, 15-first force transmission rod;

[0053] 16-upper support, 17-upper pad, 18-limiting plate, 19-stripping plate, 20-inserting plate, 21-wedge surface, 22-fixing rod, 23-second punch, 24-tapered groove;

[0054] 25-blind groove, 26-press insert. DETAILED DESCRIPTION

[0055] The present invention will be further described below with reference to the accompanying drawings, and the protection scope of the present invention is not limited to the following:

[0056] like Figures 4 to 13 As shown, a mold for flanging the end of a thin tube includes an upper mold and a lower mold. The lower mold includes a base 3, a lower pad 4 and a concave mold plate 5 fixed together in sequence from bottom to top. The lower pad 4 and the base 3 are detachably connected to each other through bolts. A concave cavity is provided on the top surface of the concave mold plate 5. A first punch 6 fixed to the top surface of the lower pad 4 is provided in the concave cavity. An arc groove 7 is provided on the top surface of the first punch 6, and an arc protrusion 8 is fixed to the bottom of the arc groove 7.

[0057] Rectangular rods 9 are fixed within the cavity of the concave mold plate 5 and on its left and right side walls. Sliders 10 are slidably mounted on each of the two rectangular rods 9. The outer end surfaces of the slides 10 are provided with blind grooves 25, which are mounted on the rectangular rods 9. The two slides 10 are symmetrically arranged about the first punch 6, one on each side of the first punch 6. A horizontal spring 11 is mounted on each of the two rectangular rods 9. The ends of the horizontal spring 11 are fixed to the inner wall of the cavity and the slides 10, respectively. The inner end surfaces of the two slides 10 are provided with a semicircular hole 12 located above the first punch 6. The diameter of the semicircular hole 12 is equal to the outer diameter of the thin tube 2. The outer ends of the two slides 10 are provided with an inclined surface 13. A first vertical spring 14 is fixed within the base 3. The top end of the first vertical spring 14 is fixedly connected to a first force transmission rod 15. The first force transmission rod 15 extends upward and sequentially through the lower pad 4 and the concave mold plate 5.

[0058] The upper die includes an upper support 16, a connecting plate and an upper pad 17 which are fixed together in sequence from top to bottom. The top surface of the upper support 16 is fixed on the punching head of the punching machine. A limiting plate 18 and a stripping plate 19 which are fixed together in sequence are arranged below the upper pad 17. A gap A is formed between the limiting plate 18 and the upper pad 17. The stripping plate 19 is fixed to the top end of the first force transmission rod 15. A gap B is formed between the bottom surface of the stripping plate 19 and the top surface of the concave template 5.

[0059] Two insert plates 20 are fixed on the bottom surface of the connecting plate, and the two insert plates 20 sequentially penetrate the upper pad 17, the limit plate 18 and the stripping plate 19 downward, and the wedge-shaped surfaces 21 of the two insert plates 20 are respectively located directly above the two inclined surfaces 13 of the two sliders 10; a fixing rod 22 is fixed on the bottom surface of the connecting plate, which sequentially penetrates the connecting plate, the upper pad 17, the limit plate 18 downward and extends into the stripping plate 19, and a second punch 23 is fixed on the bottom surface of the fixing rod 22. A conical groove 24 that cooperates with the arc-shaped protrusion 8 is provided on the bottom surface of the second punch 23, and the outer diameter of the second punch 23 is equal to the inner diameter of the thin tube 2.

[0060] A pressing insert 26 is fixedly provided in the stripper plate 19 , the bottom end of the fixing rod 22 extends into the inner cavity of the pressing insert, and the second punch 23 is located in the inner cavity of the pressing insert 26 .

[0061] A method for flanging an end of a thin tube, comprising the following steps:

[0062] S1, through the pulling mechanism will Figure 1~Figure 2 The strip is pulled from front to back into the area surrounded by the stripper plate 19 and the concave plate 5, and ensure that the first thin tube 2 on the strip is directly below the inner cavity of the press insert 26, as shown in FIG. Figure 14-15 As shown;

[0063] S2. Control the punching head of the punching machine to move downward, and the punching head drives the upper support 16 to move downward. The upper support 16 drives the connecting plate and the upper pad 17 to move downward synchronously, thereby driving the fixing rod 22, the second punch 23 and the two insert plates 20 to move downward synchronously relative to the stationary stripper plate 19. The wedge-shaped surfaces 21 of the two insert plates 20 move toward the inclined surfaces 13 of the two sliders 10 respectively, and the second punch 23 gradually extends into the inner hole of the thin tube 2;

[0064] When the bottom surface of the upper pad 17 contacts the top surface of the limit plate 18, the wedge-shaped surfaces 21 of the two insert plates 20 are respectively located directly above the inclined surfaces 13 of the two sliders 10. At the same time, the second punch 23 just extends into the inner hole of the thin tube 2. Figure 16-17 As shown, the distance between the bottom surface of the second punch 23 and the bottom surface of the thin tube 2 is 0.6 mm;

[0065] S3. As the punching head of the punching machine continues to move downward, the punch drives the upper support 16 to continue to move downward, and the upper support 16 drives the connecting plate, the upper pad 17, the limit plate 18 and the stripper plate 19 to move downward synchronously relative to the stationary concave plate 5, thereby driving the fixing rod 22, the second punch 23 and the two insert plates 20 to move downward synchronously relative to the stationary concave plate 5. The stripper plate 19 also presses the long thin plate 1 and the thin tube 2 with the material downward;

[0066] When the upper support 16 moves downward to a certain distance, the wedge-shaped surfaces 21 of the two inserting plates 20 contact the inclined surfaces 13 of the two sliders 10 respectively. At the same time, the lower end of the thin tube 2 enters the area surrounded by the semicircular holes 12 of the two sliders 10. Figure 18-19 As shown;

[0067] S4. As the punching head of the punching machine continues to move downward, the punch drives the upper support 16 to continue to move downward, and the upper support 16 drives the connecting plate, the upper pad 17, the limit plate 18 and the stripper plate 19 to move downward synchronously relative to the stationary concave plate 5, thereby driving the fixing rod 22, the second punch 23 and the two insert plates 20 to move downward synchronously relative to the stationary concave plate 5. The stripper plate 19 continues to press the long thin plate 1 and the thin tube 2 with the material downward. At the same time, the two insert plates 20 push the two sliders 10 inward respectively, so that the semicircular holes 12 of the two sliders 10 move toward the thin tube 2 respectively.

[0068] When the upper support 16 moves downward to a certain distance, the inner end surfaces of the two inserting plates 20 are in contact with the inner end surfaces of the two sliders 10 respectively. At the same time, the inner walls of the semicircular holes 12 of the two sliders 10 are in contact with the outer wall of the thin tube 2 to protect the outer wall of the thin tube 2. Figure 20-21 As shown;

[0069] S5. As the punching head of the punching machine continues to move downward, the punch drives the upper support 16 to continue to move downward, and the upper support 16 drives the connecting plate, the upper pad 17, the limit plate 18 and the stripping plate 19 to move downward synchronously relative to the stationary concave plate 5, thereby driving the fixing rod 22, the second punch 23 and the two insert plates 20 to move downward synchronously relative to the stationary concave plate 5, and the stripping plate 19 continues to press the long thin plate 1 and the thin tube 2 with material downward, wherein, when the tapered groove 24 of the second punch 23 gradually matches with the arc-shaped protrusion 8 of the first punch 6, the bottom end of the thin tube 2 gradually turns inward, and when the tapered groove 24 is fully matched with the arc-shaped protrusion 8, the bottom end of the thin tube 2 is finally turned inward, as shown in FIG. Figures 22 to 24 As shown, the inner flange of the bottom end of the thin tube 2 is completed, and the structure of the thin tube 2 after flanged is as shown Figure 3 As shown;

[0070] S6. The worker repeats the operations of steps S2 to S5 to turn the bottom ends of all the thin tubes 2 on the strip inward.

[0071] Among them, it can be seen from steps S2 to S5 that, by controlling the punch head of the punching machine to move downward, the second punch 23 can be first extended into the inner hole of the thin tube 2, and then the outer wall of the thin tube 2 is protected by the semicircular holes 12 of the two sliders 10, and then the material around the bottom end of the thin tube 2 is pushed upward by the arc groove 7 and the arc protrusion 8 of the first punch 6, thereby finally completing the inner flanging of the bottom end of the thin tube 2. It can be seen that this mold can complete the inner flanging of the bottom end of the thin tube 2 with a length of only 8mm and an inner diameter of only 1.5mm through a downward movement of the punch head of the punching machine, thereby greatly improving the efficiency of flanging the bottom end of the thin tube 2, and also solving the technical problem that the existing technology cannot perform flanging on the thin tube 2 with a length of only 8mm and an inner diameter of only 1.5mm.

[0072] In addition, since the outer wall of the thin tube fitting 2 is protected by the semicircular holes 12 of the two sliders 10, and the second punch 23 protects the inside of the thin tube fitting 2, when the arc groove 7 and the arc protrusion 8 of the first punch 6 push up the material around the bottom end of the thin tube fitting 2, the thin tube fitting 2 will not bend or deform, thereby greatly improving the quality of the inner flanging of the bottom end of the thin tube fitting 2 and meeting customer needs.

[0073] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A mold for flanging the end of a thin tube, wherein the bottom end and the top end of the thin tube (2) are both connected to the outside, the length of the thin tube (2) is 8 mm, and the inner diameter of the thin tube (2) is 1.5 mm, characterized in that: It comprises an upper die and a lower die, wherein the lower die comprises a base (3), a lower pad (4) and a concave die plate (5) which are fixedly connected to each other in sequence from bottom to top, a concave cavity is provided on the top surface of the concave die plate (5), a first convex die (6) fixedly arranged on the top surface of the lower pad (4) is provided in the concave cavity, an arc-shaped groove (7) is provided on the top surface of the first convex die (6), and an arc-shaped protrusion (8) is fixedly arranged at the bottom of the arc-shaped groove (7); A rectangular rod (9) is fixedly provided in the concave cavity of the concave template (5) and on the left and right side walls thereof, and a slider (10) is slidably sleeved on the two rectangular rods (9), and the two sliders (10) are respectively located on the left and right sides of the first punch (6). A horizontal spring (11) is sleeved on the two rectangular rods (9), and the two ends of the horizontal spring (11) are respectively fixed on the inner wall of the concave cavity and the slider (10). The inner end surfaces of the two sliders (10) are provided with a semicircular hole (12) located above the first punch (6), and the outer ends of the two sliders (10) are provided with an inclined surface (13); a first vertical spring (14) is fixedly provided in the base (3), and the top end of the first vertical spring (14) is fixedly connected to a first force transmission rod (15), and the first force transmission rod (15) passes through the lower pad (4) and the concave template (5) in sequence upward; The upper die comprises an upper support (16), a connecting plate and an upper pad (17) which are fixedly connected in sequence from top to bottom. The top surface of the upper support (16) is fixedly mounted on the punch head of the punching machine. A limiting plate (18) and a stripping plate (19) which are fixedly connected in sequence are provided below the upper pad (17). A gap A is formed between the limiting plate (18) and the upper pad (17). The stripping plate (19) is fixedly connected to the top end of the first force transmission rod (15). A gap B is formed between the bottom surface of the stripping plate (19) and the top surface of the concave template (5). Two inserting plates (20) are fixedly provided on the bottom surface of the connecting plate, and the two inserting plates (20) are downwardly penetrated through the upper pad (17), the limit plate (18) and the discharge plate (19) in sequence, and the wedge-shaped surfaces (21) of the two inserting plates (20) are respectively located directly above the two inclined surfaces (13) of the two sliders (10); A fixing rod (22) is fixed on the bottom surface of the connecting plate and passes through the connecting plate, the upper pad (17), the limit plate (18) and the inner portion of the discharge plate (19) in sequence downward. A second punch (23) is fixed on the bottom surface of the fixing rod (22). A conical groove (24) is provided on the bottom surface of the second punch (23) and matches the arc-shaped protrusion (8). The outer diameter of the second punch (23) is equal to the inner diameter of the thin tube (2). A pressing insert (26) is fixedly provided in the stripping plate (19), the bottom end of the fixing rod (22) extends into the inner cavity of the pressing insert, and the second punch (23) is located in the inner cavity of the pressing insert (26); The method for flanging the end of a thin pipe with a mold includes the following steps: S1. Pull the strip from front to back into the area enclosed by the discharge plate (19) and the concave template (5) through the pulling mechanism, and ensure that the first thin tube (2) on the strip is directly below the inner cavity of the pressing insert (26); S2, controlling the punching head of the punching machine to move downward, the punching head drives the upper support (16) to move downward, the upper support (16) drives the connecting plate and the upper pad (17) to move downward synchronously, and then drives the fixed rod (22), the second punch (23) and the two insert plates (20) to move downward synchronously relative to the stationary unloading plate (19), wherein the wedge-shaped surfaces (21) of the two insert plates (20) move toward the inclined surfaces (13) of the two sliders (10) respectively, and the second punch (23) gradually extends into the inner hole of the thin tube (2); When the bottom surface of the upper pad (17) contacts the top surface of the limit plate (18), the wedge-shaped surfaces (21) of the two inserting plates (20) are respectively located directly above the inclined surfaces (13) of the two sliders (10), and at the same time, the second punch (23) just extends into the inner hole of the thin tube (2), and the distance between the bottom surface of the second punch (23) and the bottom surface of the thin tube (2) is 0.6 mm; S3. As the punching head of the punching machine continues to move downward, the punch drives the upper support (16) to continue to move downward, and the upper support (16) drives the connecting plate, the upper pad (17), the limit plate (18) and the stripper plate (19) to move downward synchronously relative to the stationary concave plate (5), thereby driving the fixed rod (22), the second punch (23) and the two insert plates (20) to move downward synchronously relative to the stationary concave plate (5), and the stripper plate (19) also presses the long thin plate (1) and the thin tube (2) with the material downward; When the upper support (16) moves downward for a certain distance, the wedge-shaped surfaces (21) of the two inserting plates (20) respectively contact the inclined surfaces (13) of the two sliders (10), and at the same time, the lower end of the thin tube (2) enters the area surrounded by the semicircular holes (12) of the two sliders (10); S4. As the punching head of the punching machine continues to move downward, the punch drives the upper support (16) to continue to move downward, and the upper support (16) drives the connecting plate, the upper pad (17), the limit plate (18) and the unloading plate (19) to move downward synchronously relative to the stationary concave plate (5), thereby driving the fixed rod (22), the second punch (23) and the two insert plates (20) to move downward synchronously relative to the stationary concave plate (5), and the unloading plate (19) continues to press the long thin plate (1) and the thin tube (2) with the material downward. At the same time, the two insert plates (20) respectively push the two sliders (10) inward, so that the semicircular small holes (12) of the two sliders (10) respectively move toward the thin tube (2); When the upper support (16) moves downward to a certain distance, the inner end surfaces of the two inserting plates (20) respectively contact the inner end surfaces of the two sliders (10), and at the same time, the inner walls of the semicircular holes (12) of the two sliders (10) contact the outer wall of the thin tube (2) to protect the outer wall of the thin tube (2); S5. As the punching head of the punching machine continues to move downward, the punch drives the upper support (16) to continue to move downward, and the upper support (16) drives the connecting plate, the upper pad (17), the limit plate (18) and the unloading plate (19) to move downward synchronously relative to the stationary concave template (5), thereby driving the fixing rod (22), the second punch (23) and the two insert plates (20) to move downward synchronously relative to the stationary concave template (5), and the unloading plate (19) continues to press the long thin plate (1) and the thin tube (2) with the material downward, wherein, when the tapered groove (24) of the second punch (23) and the arc-shaped protrusion (8) of the first punch (6) are gradually matched, the bottom end of the thin tube (2) gradually turns inward, and when the tapered groove (24) and the arc-shaped protrusion (8) are completely matched, the bottom end of the thin tube (2) is finally turned inward, thereby completing the inner turning of the bottom end of the thin tube (2); S6. The worker repeats the operations of steps S2 to S5 to turn the bottom ends of all the thin tubes (2) on the strip inward.

2. A die for flanging the end of a thin tube according to claim 1, characterized in that: The lower pad (4) and the base (3) are detachably connected to each other via bolts.

3. A die for flanging the end of a thin tube according to claim 2, characterized in that: The two sliders (10) are arranged symmetrically with respect to the first punch (6).

4. A die for flanging the end of a thin tube according to claim 3, characterized in that: A blind groove (25) is provided in the outer end surface of the slider (10), and the blind groove (25) of the slider (10) is sleeved on the rectangular rod (9).

5. A die for flanging the end of a thin tube according to claim 4, characterized in that: The diameter of the semicircular small hole (12) is equal to the outer diameter of the thin tube (2).

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