Low-friction rotary necking forming method

Abstract

According to the low-friction rotary necking forming method, a clamping mechanism, a necking die and the like are included, the clamping mechanism comprises a square limiting block, a rotary disc, a screw rod, a driven gear, a driving gear, an outer clamp, an inner clamp, a base and a rotary rod, a cavity is formed in the necking die, and a die inlet is formed in the cavity and used for allowing a pipe blank to be axially placed into the cavity; the diameter of the cavity is gradually reduced from the die inlet to the inside, a plurality of rollers are distributed on the inner wall of the cavity and are in rolling friction fit with the outer surface of the pipe blank, the pipe blank rotates under clamping of the clamping mechanism, the necking die moves downwards, and when the upper end of the pipe blank makes contact with the first circle of roller of the necking die, the rollers are driven by the pipe blank to rotate in a driven mode; and the rollers synchronously extrude the pipe blank to start reducing deformation, along with descending of the necking die, the contact area of the pipe blank and the rollers is gradually increased, more rollers rotate in a driven mode, and the deformation amount of the material is larger and larger till necking is completed. According to the method, the risk of buckling instability of a force transfer area of the pipe blank in the forming process can be reduced, the forming difficulty is reduced, and the forming efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of plastic processing of light metal materials, in particular to a low-friction rotary shrinking forming method. Background Art

[0002] Radial shrinking forming equipment is a processing machine designed for metal pipes and similar circular cross-section materials. Its working principle is based on strong compression technology in the radial direction, aiming to accurately reduce the diameter size of the material end. This process is often accompanied by a moderate increase in the thickness of the pipe wall. Therefore, as an important tool in the fields of metal processing and automobile manufacturing, radial shrinking forming equipment is constantly promoting the manufacturing industry to a higher level and higher quality with its unique processing capabilities, advanced CNC technology, wide adaptability and environmentally friendly production concept.

[0003] Traditional shrinking forming technology includes die shrinking forming. Die shrinking forming refers to a forming process that uses a die to reduce the diameter of the mouth of a cylindrical or tubular part. It is one of the basic stamping processes. The advantages of this process are simple die structure, high forming efficiency, easy mechanization, and both local forming and overall forming can be achieved. According to product requirements, products with straight or curved busbars can be formed. According to whether there is support during the shrinking process, it can be divided into three forming methods: internal support, external support, and no support. According to whether it is heated, it can be divided into normal temperature shrinking and heated shrinking. Although a variety of forming methods have been derived on the basis of die shrinking, there is still a problem of a large limit shrinking coefficient when using die shrinking forming.

[0004] The shrinkage coefficient k is the minimum diameter after deformation. d Original blank diameter d 0, the formula is The size of the shrinkage coefficient directly affects the difficulty of shrinkage. For example, the maximum shrinkage coefficient of aluminum alloy components without support is about 0.8. In the case of external support, the shrinkage coefficient is about 0.62. Under the premise of internal and external support, the shrinkage coefficient can be reduced to about 0.5. The maximum shrinkage coefficient of steel components is larger than that of aluminum. It can be seen that the smaller the shrinkage coefficient, the greater the difficulty of forming.

[0005] Although existing technologies can form conical or quasi-conical components with large diameter differences and difficult-to-deform materials with high quality, the forming process is still cumbersome and the shrinkage coefficient of one-step forming is greatly limited. These technologies usually rely on multi-step forming processes, resulting in low production efficiency and high requirements for equipment and operators. This not only increases production costs, but may also lead to instability in forming quality, especially when dealing with complex shapes or high-strength materials. Summary of the invention

[0006] The object of the present invention is to provide a low-friction rotary shrinking forming method, which can manufacture conical or quasi-conical components with large diameter difference and difficult-to-deform materials in a short process and with high efficiency.

[0007] To achieve the above-mentioned object, the present invention provides the following technical solutions: a low-friction rotary shrinking forming method, the method relates to a low-friction rotary shrinking forming mold, the mold comprising an upper mold plate, a rotary worktable, a clamping mechanism and a shrinking mold; The clamping mechanism includes a square limit block, a rotating disk, a screw, a driven gear, a driving gear, an outer clamp, an inner clamp, a base, and a rotating rod; The turntable and the base are coaxially arranged one above and one below, and the plurality of inner clamps are evenly distributed on the base in a ring-shaped manner with the center of the base as the center, and the plurality of inner clamps are respectively slidably arranged along the radial direction of the base, and the plurality of outer clamps are fixedly arranged on the base and correspondingly located on the outer sides of the plurality of inner clamps, and a clamping space is reserved between adjacent inner clamps and outer clamps for placing the tube blank; The rotating disk is provided with an arc-shaped through groove at a position corresponding to the inner clamp, wherein one end of the arc-shaped through groove is inclined in an arc shape in the radial direction relative to the other end, and a screw rod is axially passed through each arc-shaped through groove, one end of each screw rod is fixedly connected to an inner clamp, and the other end of the screw rod passes through the arc-shaped through groove and is tightened by a nut; The plurality of driven gears and a driving gear are evenly distributed on the base in a circular manner with the center of the base as the center. The base is provided with a plurality of recessed grooves for the driven gears and the driving gears to be respectively embedded and pivotally connected therein. The rotating rod is cooperatively connected with the driving gear to drive the driving gear to rotate in the recessed groove. The end surface of the rotating disk is provided with gear teeth at positions corresponding to the driven gears and the driving gears. The gear teeth mesh with the driven gears and the driving gears to make the rotating disk rotate around its own center. When the rotating disk rotates, the screw rod slides along the arc-shaped through groove, driving the inner clamp to slide radially closer to or away from the outer clamp to control the size of the clamping space. The turntable and the base are coaxially provided with a square limiting hole. When the square limiting holes of the two coincide with each other, the square limiting block is matched and placed in the square limiting hole to limit the relative rotation of the turntable and the base. The upper template is connected to the axial feeding mechanism, the base is fixedly installed on the rotating worktable, the tube blank is clamped between the upper template and the rotating worktable through the clamping mechanism, the upper template is installed with the shrinking die, the shrinking die is provided with a cavity, the cavity is provided with a die inlet for the tube blank to be axially placed in the cavity, the cavity gradually decreases in diameter from the die inlet to the inside, a plurality of rollers are distributed on the inner wall of the cavity, and the rollers are in rolling friction cooperation with the outer surface of the tube blank; The method comprises the following steps: S1 clamping: First, place the tube blank in the clamping space between the inner clamp and the outer clamp, then rotate the rotating rod. The rotation of the rotating rod will drive the rotation of the driving gear, and then drive the turntable to rotate through the meshing with the gear teeth. The turntable with an arc-shaped through groove drives the screw to move outward, and at the same time drives the inner clamp to move outward, so that the inner clamp and the outer clamp clamp the tube blank together. At this time, the square limit holes of the turntable and the base overlap, and the square limit block is placed in the square limit hole to limit the relative rotation of the turntable and the base; S2 Shrinking: First, the rotary table drive is started, and the clamped tube billet is driven to rotate through the base, and then the upper template drives the shrinking die to feed axially. When the upper end of the tube billet contacts the first circle of rollers at the inlet of the shrinking die, the rollers are driven to rotate under the drive of the tube billet, and the rollers synchronously extrude the tube billet to start shrinking and deforming. As the shrinking die moves downward, the contact area between the tube billet and the rollers gradually increases, more rollers are driven to rotate, and the deformation of the material becomes larger and larger until the shrinking is completed.

[0008] Preferably, the method further comprises step S3 of demoulding: the tube blank continues to rotate, the shrinking die returns, and then the square limit block is removed using an auxiliary tooling, and then the rotating rod is rotated in the opposite direction, the inner clamp is released, and finally the tube blank is removed, and demoulding is completed.

[0009] Preferably, the distribution of the rollers on the inner wall of the cavity of the necking mold is as follows: a plurality of evenly spaced roller belts are provided on the inner wall of the cavity of the necking mold from the mold inlet to the inside, and each roller belt is composed of a plurality of rollers continuously combined into a row.

[0010] The inner wall of the cavity of the shrinking mold is designed with multiple semi-cylindrical roller grooves and roller shaft grooves. The roller is a cylinder with a center hole, and the roller is built-in the center hole. The roller is half-fitted in the roller groove, and a screw hole is provided in the roller groove. The roller shaft is pivotally connected in the roller groove. The rollers extend out of both ends of the roller shaft, and the extended parts are milled with planes, and shaft holes are provided on the planes. Set screws are passed through the shaft holes. The set screws lock the two ends of the roller shaft in the screw holes, so that the roller is fixed in the roller groove and semi-protrudes out of the inner wall surface of the cavity.

[0011] Preferably, both ends of the roller are provided with arc-shaped transition angles.

[0012] Preferably, the base has an inverted T-shaped slide groove at the position of the inner clamp, the inverted T-shaped slide groove is radially opened along the base, an inverted T-shaped slide table is convexly arranged on the inner surface of the inner clamp to slide in cooperation with the inverted T-shaped slide groove, a fixing hole is opened on the inverted T-shaped slide table, and one end of each screw rod is screwed into the fixing hole of the inverted T-shaped slide table of the corresponding inner clamp.

[0013] Preferably, a gear shaft is passed through the middle of the driven gear, and the gear shaft is pivotally connected in the groove; different from the driven gear, the middle of the driving gear is a through hole with a slot, and a clamping platform is provided at the end of the rotating rod, which passes through the slot and is connected to the through hole of the driving gear, and the clamping platform cooperates with the slot.

[0014] Preferably, the number of the inner clamps and the number of the outer clamps are four respectively, and they are evenly distributed in a ring shape with the center of the base as the center.

[0015] Preferably, the inner clamp and the outer clamp are both arc-shaped.

[0016] Preferably, the inner wall surface of the outer clamp and the outer wall surface of the inner clamp are both designed with anti-slip patterns.

[0017] Compared with the prior art, the beneficial effects of the present invention are: 1. Reducing the risk of buckling instability in the force transmission area of ​​the tube blank during the forming process. In the traditional die shrinking process, the friction force generated by the large-area contact between the tube blank and the shrinking die is transmitted to the undeformed area, reaching the support limit and buckling instability. The low-friction rotary shrinking forming method proposed by the present invention, on the one hand, greatly reduces the contact area between the tube blank and the roller, and the friction force is also reduced accordingly. On the other hand, the tube blank drives the roller to rotate in real time to change the direction of the friction force, so that the axial pressure transmitted to the undeformed area of ​​the tube blank is reduced, thereby reducing the risk of shrinking instability; 2. Reduce the height difference. In the traditional die shrinking process, the friction force is unevenly applied due to the uneven application of lubricants, resulting in a large difference in the height of the shrinking parts. However, the tube blank and the roller of the present invention are basically in line contact during the deformation process, and are less affected by friction. In the actual forming process, no lubricant needs to be applied or a small amount of lubricant can be applied, thereby reducing the impact of uneven application and reducing the height difference of the shrinking parts; 3. Reduce the risk of mouth deformation and wrinkling. In the process of forming, the traditional die compression mouth is prone to material accumulation and wrinkling due to the large amount of deformation of the material in the mouth area and the lack of time to deform. In the process of forming, the roller and the tube blank are locally deformed in contact, which reduces the amount of material deformation, thereby reducing the risk of deformation and wrinkling at the mouth; ④ Breaking through the limit shrinkage coefficient. The buckling instability of the tube blank in the undeformed area during the shrinkage forming process is the main factor limiting the shrinkage coefficient. The present invention reduces the risk of instability in the undeformed area and wrinkling at the mouth, so it can break through the limit shrinkage coefficient of the traditional die compression mouth. For example, using the traditional die compression mouth technology at home and abroad, the limit shrinkage coefficient of the tube blank made of aluminum alloy is 0.8 when there is no support inside and outside, but the low-friction rotary shrinkage forming proposed by the present invention can reduce the shrinkage coefficient to 0.45, improving the forming limit; ⑤ Both local shrinkage and overall shrinkage can be achieved, and it is only necessary to design the arrangement and number of rollers according to the product busbar form; ⑥ Reduce the difficulty of forming, one-time forming, improve the forming efficiency, short time, and can form conical or quasi-conical components with large diameter differences and difficult-to-deform materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the overall structure of the mold of the present invention; Figure 2 It is an exploded schematic diagram of the clamping mechanism of the present invention; Figure 3It is a schematic diagram of the top surface structure of the turntable of the present invention; Figure 4 It is a schematic diagram of the back structure of the turntable of the present invention; Figure 5 It is a structural schematic diagram of the driven gear of the present invention; Figure 6 It is a structural schematic diagram of the driving gear of the present invention; Figure 7 It is a schematic diagram of the structure of the outer clamp of the present invention; Figure 8 It is a schematic diagram of the structure of the inner clamp of the present invention; Fig. 9 It is a structural schematic diagram of the base of the present invention; Fig.10 It is a structural schematic diagram of the rotating rod of the present invention; Fig.11 It is a schematic diagram of the changing process of the clamping mechanism of the present invention; Fig.12 It is a schematic diagram of the internal structure of the necking die of the present invention; Fig.13 for Fig.12 Enlarged view of part A in the middle; Fig.14 It is a structural schematic diagram of the roller of the present invention; Fig.15 It is a cross-sectional schematic diagram of the assembly of the roller of the present invention in the roller groove; Fig.16 It is a schematic diagram of the forming process of the tube blank of the present invention under the action of the necking die.

[0019] In the figure: 1. square limit block; 2. turntable; 3. screw rod; 4. driven gear; 5. driving gear; 6. outer clamp; 7. inner clamp; 8. base; 9. turn rod; 10. inverted T-shaped slide; 11. inverted T-shaped slide; 12. arc-shaped through groove; 13. nut; 14. sink groove; 15. gear shaft; 16. clamping groove; 17. through hole; 18. clamping table; 19. gear teeth; 20. anti-slip pattern; 21. square limit hole; 22. lifting ring; 23. cavity; 24. mold inlet; 25. roller; 26. tube blank; 27. roller groove; 28. roller groove; 29. ​​roller; 30. screw hole; 31. shaft hole; 32. set screw; 100. upper template; 200. rotating worktable; 300. clamping mechanism; 400. shrinking mold; DETAILED DESCRIPTION The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] See also Figure 1-Figure 16 The present invention relates to a low-friction rotary shrinking forming die, comprising an upper die plate 100, a rotary worktable 200, a clamping mechanism 300 and a shrinking die 400; like Figure 2 As shown, the clamping mechanism 300 includes a square limit block 1, a rotating disk 2, a screw rod 3, a driven gear 4, a driving gear 5, an outer clamp 6, an inner clamp 7, a base 8, and a rotating rod 9; The turntable 2 and the base 8 are coaxially arranged one above and one below. The base 8 is designed with a mounting hole and a keyway on the back. The rotating worktable 200 is designed with corresponding key positioning. The base 8 and the rotating worktable 200 are fixed through the mounting holes. Since this is a common design of the mold, it will not be repeated here.

[0021] The plurality of inner clamps 7 are evenly distributed on the base 8 in a circular manner with the center of the base 8 as the center, and the plurality of inner clamps 7 are respectively arranged to slide radially along the base 8. The specific structure is as follows: the base 8 is provided with an inverted T-shaped slide 10 at the position of the inner clamp 7, and the inverted T-shaped slide 10 is radially provided along the base 8. An inverted T-shaped slide 11 is convexly provided on the inner surface of the inner clamp 7 to slide with the inverted T-shaped slide 10. An assembly gap is reserved between the inverted T-shaped slide 10 and the inverted T-shaped slide 11 to ensure that the inner clamp 7 can slide back and forth along the inverted T-shaped slide 10. The plurality of outer clamps 6 are fixedly arranged on the base 8 (specifically, a fixing hole can be designed at the bottom of the outer clamps 6 and fixed with screws), and are correspondingly located on the outer sides of the plurality of inner clamps 7, and a clamping space is reserved between adjacent inner clamps 7 and outer clamps 6 for placing the tube blank 26; the inner clamps 7 and the outer clamps 6 are both arc-shaped, and the outer diameter of the inner clamps 7 is the same as the inner diameter of the tube blank 26, but the inner diameter of the outer clamps 6 is about 5 mm larger than the outer diameter of the tube blank 26, so as to facilitate the placement of the tube blank 26 in the preparation stage; An arc-shaped through groove 12 is provided at the position corresponding to the inner clamp 7 of the turntable 2. The arc-shaped through groove 12 is a through groove with one end radially inclined in an arc shape relative to the other end. A screw 3 is axially arranged in each arc-shaped through groove 12, and one end of each screw 3 is fixedly connected to an inner clamp 7. Specifically, a fixing hole is provided on the inverted T-shaped slide 11 of the inner clamp 7. One end of each screw 3 is screwed into the fixing hole of the inverted T-shaped slide 11 of the corresponding inner clamp 7. The other end of the screw 3 passes through the arc-shaped through groove 12 and is tightened by a nut 13. The number of the inner clamp 7 and the outer clamp 6 is not limited. In the preferred embodiment, the number of the inner clamp 7 and the outer clamp 6 are four respectively, and they are evenly distributed in a ring shape with the center of the base 8 as the center. The four designs provide more stable and balanced clamping.

[0022] The plurality of driven gears 4 and a driving gear 5 are evenly distributed on the base 8 in a circular shape with the center of the base 8 as the center. Similarly, the preferred embodiment designs three driven gears 4, and a plurality of recessed grooves 14 are provided on the base 8 for the driven gears 4 and the driving gear 5 to be respectively embedded and pivoted therein. Specifically, a gear shaft 15 is passed through the middle of the three driven gears 4, and the gear shaft 15 is pivotally connected in the recessed groove 14; unlike the driven gear 4, the middle of the driving gear 5 is a through hole 17 with a slot 16, and a retaining plate 18 is provided at the end of the rotating rod 9, and the end of the rotating rod 9 passes through the recessed groove 14 and is connected to the through hole 17 of the driving gear 5, and the retaining plate 18 cooperates with the slot 16, and the rotating rod 9 cooperates with the driving gear 5 to drive the driving gear 5 to rotate in the recessed groove 14. The end surface of the turntable 2 is provided with gear teeth 19 at positions corresponding to the driven gear 4 and the driving gear 5. Specifically, the gear teeth 19 are designed in the interval area of ​​the arc-shaped through groove 12. The gear teeth 19 are meshed with the driven gear 4 and the driving gear 5 to make the turntable 2 rotate around its own center of circle. While the turntable 2 rotates, the four screws 3 slide along the arc-shaped through groove 12, driving the inner clamp 7 to slide radially closer to or away from the outer clamp 6 to control the size of the clamping space. The inner wall surface of the outer clamp 6 and the outer wall surface of the inner clamp 7 are both designed with anti-slip patterns 20. The anti-slip patterns 20 can specifically be cross twill patterns, which can have a good anti-slip effect.

[0023] The turntable 2 and the base 8 are coaxially provided with square limiting holes 21 of the same size, preferably designed at the center of the turntable 2 and the base 8. When the square limiting holes 21 of the two coincide, the square limiting block 1 is matched and placed in the square limiting hole 21 to limit the relative rotation of the turntable 2 and the base 8. In order to facilitate mechanized operation, a hanging ring 22 is provided on the top of the square limiting block 1.

[0024] The upper template 100 is connected to the axial feeding mechanism, and the tube blank 26 is clamped between the upper template 100 and the rotating worktable 200 through the clamping mechanism 300. The upper template 100 is installed with the shrinking die 400. The upper template 100 and the shrinking die 400 are fixed with bolts and cylindrical pins, driving the shrinking die 400 to complete vertical up and down movement.

[0025] The shrinking die 400 opens a cavity 23, and the cavity 23 is provided with a die inlet 24 for the tube blank 26 to be axially placed into the cavity 23. The cavity 23 gradually decreases in diameter from the die inlet 24 to the inside. A plurality of rollers 25 are distributed on the inner wall of the cavity 23, and the rollers 25 are in rolling and frictional engagement with the outer surface of the tube blank 26.

[0026] In a preferred embodiment, the distribution of the rollers 25 on the inner wall of the cavity 23 of the shrinking mold 400 is as follows: a plurality of evenly spaced roller belts are provided on the inner wall of the cavity 23 of the shrinking mold 400 from the mold inlet 24 to the inside, and each roller belt is composed of a plurality of rollers 25 continuously combined into a row. The inner wall of the cavity 23 of the shrinking mold 400 is designed with multiple semi-cylindrical roller grooves 27 and roller grooves 28. The roller 25 is a cylinder with a center hole, and a roller 29 is built in the center hole. The roller 25 has arc-shaped transition angles at both ends to facilitate the entry of the tube blank 26 into the mold and the transition between two adjacent rollers 25 during the shrinking process. The roller 25 is semi-fitted in the roller groove 27, and a screw hole 30 is provided in the roller groove 27. The roller 29 is pivotally connected to the roller groove 28. Both ends of the roller 29 extend out of the roller 25. The protruding parts are milled with planes, and an axial hole 31 is provided on the plane. A set screw 32 is passed through the axial hole 31. The set screw 32 locks both ends of the roller 29 in the screw hole 30, so that the roller 25 is fixed in the roller groove 27 and semi-protrudes out of the inner wall surface of the cavity 23.

[0027] like Fig.15 As shown, in order to ensure that the profile formed by each row of rollers 25 conforms to the product generatrix, it is necessary to ensure that the tangent of the outer contour generatrix of the tube blank 26 is parallel to the axis of the roller 25, and the perpendicular line of the tangent at the tangent point is perpendicular to the axis of the roller 25. The number of rollers 25 in the circumferential and axial directions can be designed according to the characteristics of the material. For example, if the material is soft, the number of rollers 25 can be appropriately reduced, and vice versa. However, regardless of the axial and circumferential directions, the interval between the rollers 25 should not be too large to prevent the tube blank 26 from being deformed between the two rollers 25 due to the material being too soft during the necking process.

[0028] The present invention provides a low-friction rotary shrinking forming method, comprising the following steps: S1 clamping: see Fig.11 First, place the tube blank 26 in the clamping space between the inner clamp 7 and the outer clamp 6, and then rotate the rotating rod 9. The rotation of the rotating rod 9 will drive the rotation of the driving gear 5, and then drive the turntable 2 to rotate through the meshing with the gear teeth 19. The turntable 2 designed with an arc-shaped through groove 12 drives the screw rod 3 to move outward, and at the same time drives the inner clamp 7 to move outward, so that the inner clamp 7 and the outer clamp 6 clamp the tube blank 26 together. At this time, the square limiting holes 21 of the turntable 2 and the base 8 overlap, and the square limiting block 1 is placed in the square limiting hole 21 to achieve the purpose of locking. Since the inner diameter of the outer clamp 6 is larger than the outer diameter of the tube blank 26, the outer clamp 6 can cause a slight deformation of the tube blank 26 when it is combined, thereby clamping the tube blank 26, and the outer surface of the inner clamp 7 and the inner surface of the outer clamp 6 are designed with cross twill, which can prevent slipping; S2 Narrowing: First, the rotary table 200 is driven to start, and the clamped tube blank 26 is driven to rotate through the base 8, and then the upper mold plate 100 drives the shrinking die 400 to feed axially. When the upper end of the tube blank 26 contacts the first circle of rollers 25 of the die inlet 24 of the shrinking die 400, the rollers 25 are driven to rotate under the drive of the tube blank 26, and the rollers 25 synchronously extrude the tube blank 26 to start shrinking and deforming. As the shrinking die 400 moves downward, the contact area between the tube blank 26 and the rollers 25 gradually increases, more rollers 25 are driven to rotate, and the deformation of the material becomes larger and larger until the shrinking is completed; S3 demoulding: the tube blank 26 continues to rotate, the shrinking die 400 returns, and then the square limit block 1 is removed using the auxiliary tooling, and then the rotating rod 9 is rotated in the opposite direction, the inner clamp 7 is released, and finally the tube blank 26 is removed, and demoulding is completed. The shrinking die 400 structure with rollers 25 also avoids the problem of difficult demoulding. The tube blank 26 can be heated or not according to the material characteristics. Cold or hot blanks will not change the mold structure, but the rollers 25 and rollers 29 of hot blanks need to choose a more heat-resistant mold material.

[0029] The technical advantages of the clamping mechanism proposed in the present invention are: ① The diameter of the inner circle of the outer clamp is about 5 mm larger than the outer diameter of the tube blank, so that the tube blank will produce slight deformation when clamped, thereby ensuring the clamping of the tube blank; ② By rotating the rotating rod, the inner clamps in four directions move simultaneously and the movement distance is consistent, thereby ensuring that the four inner clamps clamp the tube blank with the same tightness, avoiding the generation of additional stress inside the tube blank during the necking forming process due to different tightness; ③ The square limit hole and the square limit block can prevent the occurrence of problems such as clamp loosening caused by vibration during necking deformation, thereby improving safety; ④ The gear transmission structure has high torque output efficiency, and is safe and reliable.

[0030] The above description is only a preferred embodiment of the present invention and is not a limitation on the design of this case. Any equivalent changes made based on the design key of this case shall fall within the protection scope of this case.

Claims

1. A low-friction rotary necking forming method, characterized in that: The method relates to a low-friction rotary shrinking forming die, which comprises an upper die plate, a rotary worktable, a clamping mechanism and a shrinking die; The clamping mechanism includes a square limit block, a rotating disk, a screw, a driven gear, a driving gear, an outer clamp, an inner clamp, a base, and a rotating rod; The turntable and the base are coaxially arranged one above and one below, and the plurality of inner clamps are evenly distributed on the base in a ring-shaped manner with the center of the base as the center, and the plurality of inner clamps are respectively slidably arranged along the radial direction of the base, and the plurality of outer clamps are fixedly arranged on the base and correspondingly located on the outer sides of the plurality of inner clamps, and a clamping space is reserved between adjacent inner clamps and outer clamps for placing the tube blank; The rotating disk is provided with an arc-shaped through groove at a position corresponding to the inner clamp, wherein one end of the arc-shaped through groove is inclined in an arc shape in the radial direction relative to the other end, and a screw rod is axially passed through each arc-shaped through groove, one end of each screw rod is fixedly connected to an inner clamp, and the other end of the screw rod passes through the arc-shaped through groove and is tightened by a nut; The plurality of driven gears and a driving gear are evenly distributed on the base in a circular manner with the center of the base as the center. The base is provided with a plurality of recessed grooves for the driven gears and the driving gears to be respectively embedded and pivotally connected therein. The rotating rod is cooperatively connected with the driving gear to drive the driving gear to rotate in the recessed groove. The end surface of the rotating disk is provided with gear teeth at positions corresponding to the driven gears and the driving gears. The gear teeth mesh with the driven gears and the driving gears to make the rotating disk rotate around its own center. When the rotating disk rotates, the screw rod slides along the arc-shaped through groove, driving the inner clamp to slide radially closer to or away from the outer clamp to control the size of the clamping space. The turntable and the base are coaxially provided with a square limiting hole. When the square limiting holes of the two coincide with each other, the square limiting block is matched and placed in the square limiting hole to limit the relative rotation of the turntable and the base. The upper template is connected to the axial feeding mechanism, the base is fixedly installed on the rotating worktable, the tube blank is clamped between the upper template and the rotating worktable through the clamping mechanism, the upper template is installed with the shrinking die, the shrinking die is provided with a cavity, the cavity is provided with a die inlet for the tube blank to be axially placed in the cavity, the cavity gradually decreases in diameter from the die inlet to the inside, a plurality of rollers are distributed on the inner wall of the cavity, and the rollers are in rolling friction cooperation with the outer surface of the tube blank; The method comprises the following steps: S1 clamping: First, place the tube blank in the clamping space between the inner clamp and the outer clamp, then rotate the rotating rod. The rotation of the rotating rod will drive the rotation of the driving gear, and then drive the turntable to rotate through the meshing with the gear teeth. The turntable with an arc-shaped through groove drives the screw to move outward, and at the same time drives the inner clamp to move outward, so that the inner clamp and the outer clamp clamp the tube blank together. At this time, the square limit holes of the turntable and the base overlap, and the square limit block is placed in the square limit hole to limit the relative rotation of the turntable and the base; S2 Shrinking: First, the rotary table drive is started, and the clamped tube billet is driven to rotate through the base, and then the upper template drives the shrinking die to feed axially. When the upper end of the tube billet contacts the first circle of rollers at the inlet of the shrinking die, the rollers are driven to rotate under the drive of the tube billet, and the rollers synchronously extrude the tube billet to start shrinking and deforming. As the shrinking die moves downward, the contact area between the tube billet and the rollers gradually increases, more rollers are driven to rotate, and the deformation of the material becomes larger and larger until the shrinking is completed.

2. A low-friction rotary shrinking forming method according to claim 1, characterized in that: The method also includes step S3 demoulding: the tube blank continues to rotate, the shrinking die returns, and then the square limit block is removed using an auxiliary tooling, and then the rotating rod is rotated in the opposite direction, the inner clamp is released, and finally the tube blank is removed, and demoulding is completed.

3. A low-friction rotary shrinking forming method according to claim 1, characterized in that: The rollers are distributed on the inner wall of the cavity of the shrinking mold as follows: a plurality of roller belts with even intervals are arranged on the inner wall of the cavity of the shrinking mold from the mold inlet to the inside, and each roller belt is composed of a plurality of rollers continuously combined into a row.

4. A low-friction rotary shrinking forming method according to claim 1, characterized in that: The inner wall of the cavity of the shrinking mold is designed with multiple semi-cylindrical roller grooves and roller shaft grooves. The roller is a cylinder with a center hole, and the roller is built-in the center hole. The roller is half-fitted in the roller groove, and a screw hole is provided in the roller groove. The roller shaft is pivotally connected in the roller groove. The rollers extend out of both ends of the roller shaft, and the extended parts are milled with planes, and shaft holes are provided on the planes. Set screws are passed through the shaft holes. The set screws lock the two ends of the roller shaft in the screw holes, so that the roller is fixed in the roller groove and semi-protrudes out of the inner wall surface of the cavity.

5. A low-friction rotary shrinking forming method according to claim 1, characterized in that: The two ends of the roller are provided with arc-shaped transition bevels.

6. A low-friction rotary shrinking forming method according to claim 1, characterized in that: The base has an inverted T-shaped slide groove at the position of the inner clamp, the inverted T-shaped slide groove is radially opened along the base, the inner surface of the inner clamp is convexly provided with an inverted T-shaped slide table that slides in cooperation with the inverted T-shaped slide groove, a fixing hole is opened on the inverted T-shaped slide table, and one end of each screw is screwed into the fixing hole of the inverted T-shaped slide table of the corresponding inner clamp.

7. A low-friction rotary shrinking forming method according to claim 1, characterized in that: A gear shaft is passed through the middle of the driven gear, and the gear shaft is pivotally connected in the groove; unlike the driven gear, the driving gear has a through hole with a slot in the middle, and a clamping platform is provided at the end of the rotating rod. The end of the rotating rod passes through the groove and is connected to the through hole of the driving gear, and the clamping platform cooperates with the slot.

8. A low-friction rotary shrinking forming method according to claim 1, characterized in that: The number of the inner clamps and the number of the outer clamps are four respectively, and they are evenly distributed in a ring shape with the center of the base as the center.

9. A low-friction rotary shrinking forming method according to claim 1, characterized in that: The inner clamp and the outer clamp are both arc-shaped.

10. A low-friction rotary shrinking forming method according to claim 1, characterized in that: The inner wall surface of the outer clamp and the outer wall surface of the inner clamp are both designed with anti-slip patterns.

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