A method for forming an inner and outer different variable cross-section pipe

Abstract

The application discloses a forming method of a pipe with different variable cross sections inside and outside, which comprises the following steps: confirming the specification of an initial blank cylindrical hollow pipe, analyzing the distribution of the wall thickness increase of the initial blank cylindrical hollow pipe after diameter reduction, inversely obtaining the thickness that needs to be reduced in the corresponding area of the initial blank cylindrical hollow pipe according to the thickness increase in different areas, and obtaining a reduced-thickness blank cylindrical hollow pipe; placing the reduced-thickness blank cylindrical hollow pipe in a variable-wall-thickness pipe diameter processing die to obtain a variable-wall-thickness pipe with the same outer diameter and different wall thicknesses; placing the variable-wall-thickness pipe in a variable cross section processing die, synchronously inserting a core rod supporting die into the pipe core of the variable-wall-thickness pipe, and synchronously processing the outer surface and the inner surface of the variable-wall-thickness pipe when the variable cross section processing die works, so as to finally obtain a finished pipe with different variable cross sections inside and outside and uniform wall thickness distribution in all areas. The forming method of the pipe with different variable cross sections inside and outside can improve the processing precision.

Description

Technical Field

[0001] This invention relates to the field of mold technology, specifically to a method for forming tubes with different internal and external cross-sections. Background Technology

[0002] With the increasing popularity of lightweighting in automotive chassis and body structures, the widespread use of aluminum alloys is becoming a trend. Since the mechanical properties of aluminum alloys are far inferior to those of steel, structural design is particularly crucial to ensure good strength and sufficient thickness. They are often designed as complex tubular structures with different inner and outer cross-sections.

[0003] like Figure 1 The aluminum alloy tubes shown are tapered, with a large circumference in the middle and smaller at both ends. The inner surface has a regular, equidistant circumferentially distributed strip-shaped groove structure, and the wall thickness is uniformly distributed throughout. To meet the requirements for manufacturing aluminum tubes with this structure, conventional low-cost methods include spinning or stamping in two halves. Higher-cost methods include casting or high-pressure die casting, with different tapered shapes for the outer surface. However, these traditional manufacturing methods have various drawbacks, as explained below.

[0004] I. Defects of using spinning, extrusion, or stamping compression tube processes:

[0005] 1. Low processing efficiency

[0006] Because the product is reduced in size, it is impossible to process it in one go, whether by spinning, extrusion or punching. The pipe diameter needs to be reduced in several separate processes, which is very inefficient.

[0007] 2. Poor processing quality

[0008] Because it requires multiple separate processing steps and has inherent processing defects, the extrusion marks on the surface of the spun product are very obvious. It is difficult to achieve a large conical surface and a large reduction ratio when extruding and compressing. Wrinkling defects are prone to occur after reduction, and severe mold marks are also prone to occur when stamping and compressing tubes. These appearance defects cannot be eliminated at all.

[0009] 3. Internal dimensions cannot be guaranteed.

[0010] Spinning, extrusion, or stamping can only process the outer surface of tubes, while the interior cannot be processed at all. The inner surface can only be extruded to the required size from the raw material, but since tube shrinking will cause changes in wall thickness, the internal dimensions cannot be guaranteed.

[0011] II. Defects in manufacturing processes using casting or high-pressure die-casting:

[0012] 1. Poor appearance and low pass rate

[0013] Due to inherent defects in the casting or high-pressure die casting processes, the products produced often have flash or sprue marks, resulting in a very low pass rate for finished products with high dimensional accuracy requirements.

[0014] 2. Successful processing and manufacturing.

[0015] Whether using casting or high-pressure die casting, the manufacturing process is difficult and has a low pass rate. To meet the dimensional requirements of the sample delivery state, subsequent CNC machining is still required, resulting in high manufacturing costs.

[0016] 3. Uneven internal grain structure, resulting in substandard finished product performance.

[0017] Whether it is casting or high-pressure casting, the process involves melting aluminum into a liquid, pouring it into the mold runner, and then rapidly flowing it into each cavity of the mold under pressure. Finally, it is cooled and removed. Therefore, the grain structure of each region will be uneven during the product formation process. Even with subsequent solution treatment and aging, the performance of different regions will vary.

[0018] In summary, traditional processes are cumbersome and costly to produce aluminum tube products that meet the requirements. They also bring varying degrees of quality risks and appearance defects. More importantly, they cannot ensure that the performance of all areas of the product is uniformly controlled within the required range.

[0019] Existing technology, patent publication number CN115090774A, discloses an equal-wall-thickness tube shrinking mold and tube shrinking process, comprising a single-element unit and a binary unit, the maximum distance between which forms a sliding advance distance. The mold pushes forward to shrink the tube by a large proportion, and then retracts to pull the mandrel to ensure equal wall thickness. The binary structure enables smooth entry of the tube blank into the mold for shrinking and the retraction of the mandrel to adjust the tube blank wall thickness. The opening and closing of the advance distance is mainly reflected in the position change of the working position of the mandrel head. When the advance distance closes, the mandrel head moves forward to the mold entry flare, ensuring sufficient clearance for the tube blank to enter the mold. When the mold retracts, the advance distance opens, and the mandrel head moves backward to the straight section of the mold core, ensuring that the tube blank maintains its original wall thickness after shrinking. However, the initial tube blank in the prior art is directly pre-formed, and then equal-wall-thickness tube shrinking is performed using the single-element unit and the binary unit. Summary of the Invention

[0020] The technical problem to be solved by the present invention is to provide a forming method for an aluminum product with an outer surface that is conical with a large cross-section in the middle and small at both ends, an inner surface that has a regular circumferentially distributed strip groove structure, and a uniform wall thickness distribution in all areas.

[0021] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0022] A method for forming a pipe with different cross-sections inside and out includes the following steps:

[0023] S100. Confirm the specifications of the initial blank cylindrical hollow tube (110);

[0024] S200. Analyze the distribution of the wall thickness increase after the initial blank cylindrical hollow tube (110) is reduced in diameter after the specifications are confirmed. Based on the thickening results in different areas, reverse the process to obtain the thickness that needs to be reduced in the corresponding area of ​​the initial blank cylindrical hollow tube (110) and obtain the thinned blank cylindrical hollow tube (120).

[0025] S300. Place the thinned blank cylindrical hollow tube (120) in the variable wall thickness tube diameter processing mold (200) to obtain a variable wall thickness tube (130) with the same outer diameter but different wall thickness.

[0026] S400. Place the variable wall thickness pipe (130) in the variable cross-section processing mold (300), and simultaneously insert a mandrel support mold (400) into the core of the variable wall thickness pipe (130). When the variable cross-section processing mold (300) is working, simultaneously process the outer and inner surfaces of the variable wall thickness pipe (130) to finally obtain a finished pipe with different inner and outer surfaces and a variable cross-section and uniform wall thickness distribution in all areas.

[0027] Advantages: It can process complex variable cross-section outer diameters that meet the requirements in one go, with high processing efficiency, low cost, and better appearance quality. By calculating the range of wall thickness increase during conventional diameter reduction, the internal wall thickness distribution can be effectively controlled by reducing the wall thickness in the opposite direction. It can be used as an effective method for processing products with extremely high lightweight requirements. The variable wall thickness pipe diameter processing mold can be used to process more aluminum parts with different circular outer cross-sections. The processed products can also be used as key process parts in hydroforming to process more complex cross-section products. In conjunction with external processing, the mold can be supported by a shrinkable and deformable mandrel to process more products with a large middle and small ends, effectively controlling the internal dimensions of the product and ensuring synchronous and precise control of internal and external dimensions.

[0028] In one embodiment of the present invention, the variable wall thickness pipe diameter processing mold (200) includes a variable wall thickness pipe diameter lower mold (210), a variable wall thickness pipe diameter upper mold (220), a variable wall thickness pipe diameter left mandrel (230), and a variable wall thickness pipe diameter left mandrel (240).

[0029] In use, the thinned blank cylindrical hollow tube (120) is placed inside the variable wall thickness tube diameter lower mold (210); after the variable wall thickness tube diameter lower mold (210) and the variable wall thickness tube diameter upper mold (220) are closed, the variable wall thickness tube diameter left mandrel (230) and the variable wall thickness tube diameter left mandrel (240) move towards or away from each other between the variable wall thickness tube diameter lower mold (210) and the variable wall thickness tube diameter upper mold (220) to squeeze the thinned blank cylindrical hollow tube (120) and obtain the variable wall thickness tube (130).

[0030] In one embodiment of the present invention, the variable cross-section processing mold (300) includes a power device (310), a base and guide device (320), a lever device (330), and a variable cross-section mold body (340); the base and guide device (320) is fixedly connected to the power device (310); the variable cross-section mold body (340) is located inside the base and guide device (320); one end of the lever device (330) is connected to the variable cross-section mold body (340), and the other end is connected to the power device (310); when the power device (310) rotates, it can drive the base and guide device (320), the lever device (330), and the variable cross-section mold body (340) to rotate synchronously; when the power device (310) performs telescopic movement, it can cause the lever device (330) to drive the variable cross-section mold body (340) to perform axial reciprocating motion inside the base and guide device (320).

[0031] In one embodiment of the present invention, the power unit (310) includes a hydraulic cylinder (311), a driven gear (312), a motor, and a driving gear; a tapered joint (3111) is fixed to the rear end of the output shaft of the hydraulic cylinder (311) after passing through the driven gear (312), and the tapered joint (3111) is rotatable relative to the output shaft of the hydraulic cylinder (311); the output shaft of the motor is coaxially connected to the driving gear, the driving gear meshes with the driven gear (312), and when the motor rotates, the driving gear drives the driven gear (312) to rotate.

[0032] In one embodiment of the present invention, the base and guide device (320) includes a first rotating shaft seat (321), a second rotating shaft seat (322), a push rod bracket (323), and a guide connecting frame (324); the driven gear (312), the first rotating shaft seat (321), and the second rotating shaft seat (322) are arranged coaxially in sequence; the two ends of the push rod bracket (323) are respectively connected to the first rotating shaft seat (321) and the driven gear (312), and the two ends of the guide connecting frame (324) are respectively fixedly connected to the first rotating shaft seat (321) and the second rotating shaft seat (322).

[0033] In one embodiment of the present invention, a cross-shaped hollow space (3211) is provided at the center of both the first rotating shaft seat (321) and the second rotating shaft seat (322); and around the center of the first rotating shaft seat (321), a plurality of equally angularly distributed opening slots (3212) are provided at the edge of the first rotating shaft seat (321), the depth direction of the opening slots (3212) facing the four corners of the cross-shaped hollow space (3211); and the opening slots (3212) and the cross-shaped hollow space (3211) are not connected, and an installation space (3213) is provided between them;

[0034] Multiple push rod supports (323) are distributed in equal-angle circles around the center of the first rotating shaft seat (321). One end is connected to the first rotating shaft seat (321) at the installation space (3213), and the other end is connected to the driven gear (312). The conical joint (3111) is located between the multiple push rod supports (323).

[0035] In one embodiment of the present invention, the two ends of the plurality of guide connecting brackets (324) are respectively fixed to the first rotating shaft seat (321) and the second rotating shaft seat (322) between two adjacent corners of the cross-shaped hollow space (3211) of the first rotating shaft seat (321) and the second rotating shaft seat (322). The interval between two adjacent guide connecting brackets (324) is connected to the four corners of the two cross-shaped hollow spaces (3211) to form a guide space (3221). The variable cross-section mold body (340) is located in the guide space (3221).

[0036] In one embodiment of the present invention, the lever device (330) includes a lever support (331), a movable lever (332), and an inclined push rod (333); the lever support (331) is connected to two adjacent guide connecting frames (324) near the first rotating shaft seat (321); the movable lever (332) is pin-connected to the lever support (331), and one end passes through the opening slot (3212) and is hinged to the inclined push rod (333), and the other end is hinged to the variable cross-section mold body (340); the inclined push rod (333) passes through the push rod support (323) and is connected to the conical joint (3111) in a dovetail groove manner.

[0037] In one embodiment of the present invention, the variable cross-section mold body (340) includes a diameter reduction component (341) and a movable connecting component (342); one end face of the diameter reduction component (341) is connected to the movable connecting component (342), and the movable connecting component (342) is hinged to the other end of the movable lever (332); the other end face of the diameter reduction component (341) is a processing and forming cavity area; the variable wall thickness pipe (130) is located inside the diameter reduction component (341), and the variable cross-section mold body (340) reciprocates in the guide space (3221) to reduce the outer diameter of the variable wall thickness pipe (130).

[0038] In one embodiment of the present invention, the diameter reduction assembly (341) includes a plurality of diameter reduction mold bodies (3411), and the plurality of diameter reduction mold bodies (3411) are circumferentially distributed. Each diameter reduction mold body (3411) is connected to a corresponding movable connector (342). The plurality of diameter reduction mold bodies (3411) are respectively located in the guide space (3221), and when the plurality of diameter reduction mold bodies (3411) are enclosed, they form a complete processing and forming cavity area.

[0039] In one embodiment of the present invention, the movable connecting assembly (342) includes a movable block (3421), a linear guide block (3424), and a mold locking block (3425); one of the four sides of the movable block (3421) is provided with a dovetail fixing groove (3422), and the slide bar (3412) of the diameter-reducing mold body (3411) is engaged in the dovetail fixing groove (3422); the side opposite to the dovetail fixing groove (3422) is provided with a lug (3). 423), the lug (3423) is hinged to the other end of the movable lever (332); the linear guide block (3424) is fixedly located on the other two sides of the movable block (3421), and the linear guide block (3424) contacts the inner wall of the guide space (3221); the mold locking block (3425) is detachably connected to the front end of the movable block (3421), and the front end of the movable block (3421) faces the second rotating shaft seat (322).

[0040] In one embodiment of the present invention, the mandrel support mold (400) includes a mandrel support strip main body assembly (410), a movable support strip assembly (420), and a movable push rod (430); the movable support strip assembly (420) is located inside the mandrel support strip main body assembly (410), the movable support strip assembly (420) has the same size as the concave rib inside the finished pipe, the spacing and distribution between two adjacent mandrel support strips (4121) in the mandrel support strip main body assembly (410) correspond one-to-one with the convex rib inside the finished pipe; and the movable support strip assembly (420) can slide along the mandrel support strip main body assembly (410); the movable push rod (430) is slidably fitted with the movable support strip assembly (420); after the mandrel support mold (400) is opened, its outer contour is the molded imprint of the internal strip groove of the finished pipe.

[0041] In one embodiment of the present invention, during processing, the movable push rod (430) is inserted into the main body assembly (410) of the mandrel support strip, pushing the movable support strip assembly (420) to slide along the main body assembly (410) of the mandrel support strip and abut against the movable push rod (430), thus opening the main body assembly (410). When the variable cross-section processing mold (300) is working, the inner surface of the variable wall thickness pipe (130) is processed simultaneously. After processing is completed, the movable push rod (430) is withdrawn from the main body assembly (410), and the main body assembly (410) of the mandrel support strip loses its support. The opened main body assembly (410) of the mandrel support strip contracts and is taken out from the core of the finished pipe.

[0042] Compared with the prior art, the beneficial effects of the present invention are as follows: For traditional processing technology, processing aluminum products with complex structures such as a conical outer surface with a large cross-section in the middle and small at both ends, an inner surface with a regular circumferentially distributed strip groove structure, and uniform wall thickness distribution in all areas suffers from low processing efficiency, high cost, poor processing quality, low pass rate, inability to guarantee internal dimensions, and uneven internal grain structure. By using the method in the present invention, products with more cost advantages can be processed efficiently and accurately.

[0043] The variable cross-section mold body designed in this invention combines a rotary diameter reduction mechanism and a shrinkable deformation mechanism, with precise control both internally and externally. It is suitable for processing more complex products with a circular variable cross-section on the outer surface, regular shapes with equal-angle circular distribution inside, and high requirements for wall thickness distribution. At the same time, the products made can be processed into more complex product structures through methods such as hydroforming technology, covering a wider range of technical fields. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of an existing aluminum alloy tube.

[0045] Figure 2 This is a flowchart illustrating a method for forming pipes with different internal and external cross-sections according to an embodiment of the present invention.

[0046] Figure 3 This is a schematic diagram of the initial blank cylindrical hollow tube according to an embodiment of the present invention.

[0047] Figure 4 This is a schematic diagram illustrating the thickening of the pipe fitting after diameter reduction, as shown in the simulation analysis of an embodiment of the present invention.

[0048] Figure 5 This is a schematic diagram of the initial blank cylindrical hollow tube being thinned according to an embodiment of the present invention.

[0049] Figure 6 This is a schematic diagram of a variable wall thickness pipe diameter processing mold according to an embodiment of the present invention.

[0050] Figure 7 This is a schematic diagram of the working process of the variable wall thickness pipe diameter processing mold according to an embodiment of the present invention.

[0051] Figures 8 to 10 This is a schematic diagram of a variable cross-section machining mold according to an embodiment of the present invention.

[0052] Figure 11 This is a schematic diagram of the base and guide device according to an embodiment of the present invention.

[0053] Figure 12 and Figure 13 This is a schematic diagram of the diameter reduction component according to an embodiment of the present invention.

[0054] Figure 14 This is a schematic diagram of the active connection component according to an embodiment of the present invention.

[0055] Figure 15 This is a schematic diagram of the lever device and the variable cross-section mold body according to an embodiment of the present invention.

[0056] Figures 16 to 20 This is a schematic diagram of the working process of the variable cross-section machining mold according to an embodiment of the present invention.

[0057] Figures 16 to 20 This is a schematic diagram of the working process of the variable cross-section machining mold according to an embodiment of the present invention.

[0058] Figure 21 This is a schematic diagram of the mandrel support mold according to an embodiment of the present invention.

[0059] Figure 22 This is a schematic diagram of the main component of the mandrel support strip according to an embodiment of the present invention.

[0060] Figure 23 This is a schematic diagram of the main support bar assembly and the movable support bar assembly according to an embodiment of the present invention.

[0061] Figure 24 This is a schematic diagram of the movable support bar assembly and movable push rod according to an embodiment of the present invention.

[0062] Figure 25 and Figure 26 This is a schematic diagram of the working process of the mandrel support mold according to an embodiment of the present invention.

[0063] Figures 27 to 29 This is a schematic diagram of the types of pipes suitable for processing according to the present invention. Detailed Implementation

[0064] Please see Figure 2 As shown, the present invention provides a method for forming a pipe with different internal and external cross-sections, including the following steps:

[0065] S100. Confirm the specifications of the initial blank cylindrical hollow tube 110.

[0066] Please see Figure 2 and Figure 3 As shown, in one embodiment of the present invention, aluminum tubes are classified into two types: welded tubes and seamless tubes. The method of differentiation is to cut the end face of the tube flat, soak it in alkaline water for about 5 minutes, and then observe the cut surface. If obvious white spots appear, it is a welded tube; otherwise, it is a seamless tube. The tube manufacturing processes of the two types of tubes are completely different, and the former has a cost advantage. In this embodiment, the lower-cost welded tube is selected.

[0067] When selecting the specifications of the initial blank cylindrical hollow tube 110, the diameter of the circle equivalent to the maximum cross-sectional circumference of the product is used as the basis for selecting the tube diameter of the initial blank cylindrical hollow tube 110, and the wall thickness of the thickest area of ​​the product is used as the basis for selecting the wall thickness of the initial blank cylindrical hollow tube 110.

[0068] The commonly used processing states for aluminum alloy materials are T1 or T4. In this embodiment, in order to better achieve uniform flow distribution of the material during extrusion, the tube-making state selected is F, that is, during the tube-making process, the extruded tube does not require air cooling, water cooling or gas protection cooling.

[0069] S200. Analyze and confirm the distribution of the wall thickness increase of the initial blank cylindrical hollow tube 110 after diameter reduction. Based on the thickness increase results of different regions, reverse the process to obtain the thickness that needs to be reduced in the corresponding region of the initial blank cylindrical hollow tube 110, and obtain the thinned blank cylindrical hollow tube 120.

[0070] Please see Figures 2 to 5As shown, in one embodiment of the present invention, since the wall thickness will increase accordingly when the pipe diameter is reduced, but the finished product requires uniform wall thickness, it is necessary to perform a variable wall thickness pretreatment on the original straight pipe with equal thickness before pipe reduction, that is, to obtain a pipe with equal outer diameter and variable wall thickness, and to pre-thin the area where the wall thickness increases after diameter reduction.

[0071] First, CAE (Computer-Aided Engineering) simulation analysis was used to determine the magnitude and distribution of the increase in wall thickness after the pipe diameter reduction, such as... Figure 4 The simulation analysis shows the thickness increase of the pipe fitting after diameter reduction. Based on the thickness increase results in different areas, the required thickness reduction for the corresponding area of ​​the initial blank cylindrical hollow pipe 110 is calculated in reverse, as follows: Figure 5 This is to meet the dimensional requirement of reducing the wall thickness of the initial blank cylindrical hollow tube 110.

[0072] S300. Place the thinned blank cylindrical hollow tube 120 in the variable wall thickness tube diameter processing mold 200 to obtain a variable wall thickness tube 130 with the same outer diameter but different wall thickness.

[0073] Please see Figures 2 to 6 As shown, in one embodiment of the present invention, the variable wall thickness pipe diameter processing mold 200 includes a variable wall thickness pipe diameter lower mold 210, a variable wall thickness pipe diameter upper mold 220, a variable wall thickness pipe diameter left mandrel 230, and a variable wall thickness pipe diameter left mandrel 240.

[0074] As shown in Figure 7, during use, the thinned blank cylindrical hollow tube 120 is placed inside the variable wall thickness tube diameter lower die 210. After the variable wall thickness tube diameter lower die 210 and the variable wall thickness tube diameter upper die 220 are closed, the variable wall thickness tube diameter left mandrel 230 and the variable wall thickness tube diameter left mandrel 240 move towards or away from each other between the variable wall thickness tube diameter lower die 210 and the variable wall thickness tube diameter upper die 220 to extrude the thinned blank cylindrical hollow tube 120 and obtain the variable wall thickness tube 130.

[0075] At both ends of the pipe fitting placement area of ​​the variable wall thickness pipe diameter lower mold 210, adjustment grooves 211 are respectively provided, and a fixed block 212, an adjustment spring 213, and a movable stop block 214 are provided in the adjustment grooves 211. The two ends of the adjustment spring 213 are fixedly connected to the fixed block 212 and the movable stop block 214 respectively. The fixed block 212 is engaged and fixed with the adjustment groove 211. The movable stop block 214 is used to abut against the thinned blank cylindrical hollow pipe 120. When the thinned blank cylindrical hollow pipe 120 is processed, when the axial dimension increases, it can extend into the area of ​​the two adjustment grooves 211, so that the movable stop block 214 moves closer to the fixed block 212 and compresses the adjustment spring 213.

[0076] S400: Place the variable wall thickness pipe 130 in the variable cross-section processing mold 300, and simultaneously insert a mandrel support mold 400 into the core of the variable wall thickness pipe 130. When the variable cross-section processing mold 300 is working, the outer and inner surfaces of the variable wall thickness pipe 130 are processed simultaneously to finally obtain a finished pipe with different inner and outer surfaces, variable cross-section, and uniform wall thickness distribution in all areas.

[0077] Please see Figures 2 to 20 As shown, in one embodiment of the present invention, the variable cross-section processing mold 300 includes a power unit 310, a base and guide device 320, a lever device 330, and a variable cross-section mold body 340. The base and guide device 320 is fixedly connected to the power unit 310, the variable cross-section mold body 340 is located within the base and guide device 320, one end of the lever device 330 is connected to the variable cross-section mold body 340, and the other end is connected to the power unit 310. When the power unit 310 rotates, it can drive the base and guide device 320, the lever device 330, and the variable cross-section mold body 340 to rotate synchronously. When the power unit 310 performs telescopic movements, it can cause the lever device 330 to drive the variable cross-section mold body 340 to perform axial reciprocating motion within the base and guide device 320.

[0078] The power unit 310 includes a hydraulic cylinder 311, a driven gear 312, a motor (not shown in the figure), and a driving gear (not shown in the figure). A tapered joint 3111 is fixed to the end of the output shaft of the hydraulic cylinder 311 after passing through the driven gear 312. The tapered joint 3111 can rotate relative to the output shaft of the hydraulic cylinder 311, preventing the oil pipe from being twisted or damaged when the rotating gear drives the hydraulic cylinder 311 to rotate. The output shaft of the motor is coaxially connected to the driving gear, and the driving gear meshes with the driven gear 312. When the motor rotates, the driven gear drives the driven gear 312 to rotate.

[0079] The base and guide device 320 includes a first rotating shaft seat 321, a second rotating shaft seat 322, a push rod bracket 323, and a guide connecting frame 324. The driven gear 312, the first rotating shaft seat 321, and the second rotating shaft seat 322 are arranged coaxially in sequence. The two ends of the push rod bracket 323 are respectively connected to the first rotating shaft seat 321 and the driven gear 312, and the two ends of the guide connecting frame 324 are respectively fixedly connected to the first rotating shaft seat 321 and the second rotating shaft seat 322.

[0080] A cross-shaped hollow space 3211 is provided at the center of both the first rotating shaft seat 321 and the second rotating shaft seat 322. Around the center of the first rotating shaft seat 321, a plurality of equally angularly distributed opening slots 3212 are provided at the edge of the first rotating shaft seat 321. The depth direction of the opening slots 3212 faces the four corners of the cross-shaped hollow space 3211. The opening slots 3212 and the cross-shaped hollow space 3211 are not connected, and an installation space 3213 is provided between them.

[0081] Multiple push rod supports 323 are distributed in equal-angle circles around the center of the first rotating shaft seat 321. One end is connected to the first rotating shaft seat 321 at the installation space 3213, and the other end is connected to the driven gear 312. The conical joint 3111 is located between the multiple push rod supports 323.

[0082] The two ends of the multiple guide connecting frames 324 are respectively between two adjacent corners of the cross-shaped hollow space 3211 of the first rotating shaft seat 321 and the second rotating shaft seat 322, and are fixedly connected to the first rotating shaft seat 321 and the second rotating shaft seat 322. The interval between two adjacent guide connecting frames 324 is connected to the four corners of the two cross-shaped hollow spaces 3211 to form a guide space 3221. The variable cross-section mold body 340 is located in the guide space 3221.

[0083] The lever device 330 includes a lever support 331, a movable lever 332, and a slanted push rod 333. The lever support 331 is connected to two adjacent guide connecting frames 324 near the first rotating shaft seat 321. The movable lever 332 is pin-connected to the lever support 331, with one end passing through the opening slot 3212 and hinged to the slanted push rod 333, and the other end hinged to the variable cross-section mold body 340. The slanted push rod 333 passes through the push rod support 323 and is connected to the conical joint 3111 in a dovetail groove configuration.

[0084] The variable cross-section mold body 340 includes a diameter reduction component 341 and a movable connecting component 342. One end face of the diameter reduction component 341 is connected to the movable connecting component 342, and the movable connecting component 342 is hinged to the other end of the movable lever 332. The other end face of the diameter reduction component 341 is the processing and forming cavity area. The variable wall thickness pipe 130 is located inside the diameter reduction component 341. The variable cross-section mold body 340 reciprocates within the guide space 3221 to reduce the outer diameter of the variable wall thickness pipe 130.

[0085] The diameter reduction assembly 341 includes multiple diameter reduction mold bodies 3411, which are circumferentially distributed. Each diameter reduction mold body 3411 is connected to a corresponding movable connector 342. The multiple diameter reduction mold bodies 3411 are located within a guide space 3221, and when the multiple diameter reduction mold bodies 3411 are enclosed, they form a complete processing and forming cavity area. Among the four sides of each diameter reduction mold body 3411, one side is provided with a slide bar 3412, the side opposite the slide bar 3412 is a partial processing and forming cavity area 3413, and the other two sides are provided with lubricating blocks 3414. The partial processing and forming cavity area 3413 includes a partial processing and forming cavity area body 34131 and a limiting contact surface 34132 and a clearance surface 34133 that respectively contact the two sides of the partial processing and forming cavity area body 34131. In the partially machined forming cavity area 3413, 80% of the surface is designed to match the required dimensions of the final product, i.e., the main body of the forming cavity area 34131. However, the cavity near the limiting contact surface 34132 is intentionally designed with a certain angle of clearance, i.e., clearance surface 34133. The purpose is to guide and compress the straight tube well during the diameter reduction process, avoiding edge biting. Only 30% of the main body of the forming cavity area 34131 is designed for effective contact and limiting; the remaining part is for effective clearance. This is because it is difficult to guarantee the machining accuracy of a large area of ​​inclined surface. If the accuracy of even a small area of ​​the inclined surface exceeds the tolerance, the entire mold set will not fit well. To prevent overheating or wear caused by prolonged friction with the equipment contact surface, a lubricating block 3414 with good lubrication and fast heat dissipation is designed and installed.

[0086] The movable connection assembly 342 includes a movable block 3421, a linear guide block 3424, and a mold locking block 3425. One side of the movable block 3421 has a dovetail retaining groove 3422, into which the slide bar 3412 of the reduced-diameter mold body 3411 engages. The side opposite the dovetail retaining groove 3422 has a lug 3423, which is hinged to the other end of the movable lever 332. The linear guide block 3424 is fixedly located on the other two sides of the movable block 3421 and contacts the inner wall of the guide space 3221. The mold locking block 3425 is detachably connected to the front end of the movable block 3421, with the front end of the movable block 3421 facing the second rotating shaft seat 322.

[0087] When the variable wall thickness pipe 130 is placed inside the variable cross-section mold body 340, and a mandrel is simultaneously inserted into the core of the variable wall thickness pipe 130 to support the mold 400, the variable cross-section processing mold 300, when in use, includes telescopic and rotational movements. During the telescopic movement:

[0088] S411, the cylinder 311 extends and moves forward, pushing the inclined push rod 333 upward. After the inclined push rod 333 is pushed upward, it drives the movable lever 332 to swing. The movable lever 332 connected to the variable cross-section mold body 340 first presses down on the variable cross-section mold body 340, closing the variable cross-section mold body 340. Then, it pushes the variable cross-section mold body 340 to slide forward axially in the guide space 3221, extruding the variable wall thickness pipe 130.

[0089] In the initial state, the hydraulic cylinder 311 does not apply any thrust and is in the retracted state, at which time the mold is in the open state.

[0090] S412, the cylinder 311 retracts and moves backward, the inclined push rod 333 is pulled down, and after the inclined push rod 333 pushes down, it drives the movable lever 332 to swing. The movable lever 332 connected to the variable cross-section mold body 340 first opens the closed variable cross-section mold body 340, and then pushes the variable cross-section mold body 340 to slide backward axially in the guide space 3221, releasing the variable wall thickness pipe 130.

[0091] S413, by repeatedly extending and retracting the hydraulic cylinder 311, the variable cross-section mold body 340 can repeatedly perform the "extrusion-retraction-extrusion" action to reduce the outer diameter of the variable wall thickness pipe 130, and at the same time complete the concave and convex shaping of the inner wall of the variable wall thickness pipe 130.

[0092] During rotational motion:

[0093] S414 The motor rotates, driving the drive gear and driven gear 312 to mesh, synchronously driving the base and guide device 320, lever device 330, variable cross-section mold body 340, variable wall thickness pipe 130 and mandrel support mold 400 to rotate synchronously, realizing multi-angle rapid diameter reduction.

[0094] Combining the above two actions, the high-efficiency hydraulic cylinder 311 achieves rapid and regular forward and backward movements under hydraulic pressure. Through the lever device 330, it drives the variable cross-section mold body 340 to simultaneously achieve a closed and opened cycle. By repeatedly performing the "extrusion-retraction-extrusion" action of the variable cross-section mold body 340, the outer diameter of the variable wall thickness pipe 130 can be reduced. At the same time, the variable cross-section mold body 340 will also rotate together with the base and guide device 320 to achieve rapid diameter reduction of the workpiece from multiple angles. After the product is fixed at the center of rotation, it is continuously pushed inward to ensure that the conical surface is extruded sequentially until it is pushed to the limit block. This process not only produces the product that meets the dimensions but also better avoids mold marks on the outer surface.

[0095] Please see Figures 1 to 26As shown, in one embodiment of the present invention, the mandrel support mold 400 includes a mandrel support strip main body assembly 410, a movable support strip assembly 420, and a movable push rod 430. The movable support strip assembly 420 is located inside the mandrel support strip main body assembly 410, and the size of the movable support strip assembly 420 is consistent with the concave ribs inside the finished pipe. The spacing and distribution between two adjacent mandrel support strips 4121 in the mandrel support strip main body assembly 410 correspond one-to-one with the convex ribs inside the finished pipe. The movable support strip assembly 420 can slide along the mandrel support strip main body assembly 410, and the movable push rod 430 slides with the movable support strip assembly 420. After the mandrel support mold 400 is opened, its outer contour is the molded imprint of the internal strip groove of the finished pipe.

[0096] During processing, the movable push rod 430 is inserted into the main body assembly 410 of the mandrel support strip, pushing the movable support strip assembly 420 to slide along the main body assembly 410 of the mandrel support strip and abut against the movable push rod 430, thus opening the main body assembly 410 of the mandrel support strip. When the variable cross-section processing mold 300 is working, the inner surface of the variable wall thickness pipe 130 is processed simultaneously. After processing is completed, the movable push rod 430 is withdrawn from the main body assembly 410 of the mandrel support strip, and the main body assembly 410 of the mandrel support strip loses its support. The opened main body assembly 410 of the mandrel support strip retracts and is removed from the core of the finished pipe.

[0097] The outer surface can be processed using the methods described above, while the dimensional control of the inner surface's concave and convex shape needs to be ensured by the mandrel support strip main assembly 410. The mandrel support strip main assembly 410 can be inserted into the product before diameter reduction and its front and rear positions can be fixed. Once the diameter is reduced, the product will have a structure that is larger in the middle and smaller at both ends. It is crucial to remove the mandrel without affecting the internal and external dimensions of the product. In fact, according to the above method, even without using any internal support, the inner wall of the product after diameter reduction will be a regular circle. The circle size is related to the control of the wall thickness and range in step S200. Therefore, the mandrel support strip main assembly 410 only needs to control the shape dimensions of the inner groove.

[0098] In one embodiment of the present invention, the mandrel support strip main body assembly 410 includes a tapered section 411, a slot section 412, and a locking section 413 connected in sequence. The size of the tapered section 411 is consistent with the inner shape of the smallest diameter end of the product. In the slot section 412 located in the middle, the spacing between two adjacent mandrel support strips 4121 is used to install and restrict the movable support strip assembly 420. That is, the movable support strips 421 in the movable support strip assembly 420 and the mandrel support strips 4121 in the slot section 412 are alternately arranged in sequence. In the retracted state, the outer diameters of both the slot section 412 and the locking section 413 are smaller than the inner diameter of the other end of the product.

[0099] A groove 4122 and multiple retraction springs 4123 are provided on the mandrel support bar 4121. The two ends of the movable support bar 421 can slide along the groove 4122. When the main body assembly 410 of the mandrel support bar is opened, the retraction springs 4123 are compressed and abut against the movable support bar 421. The function of the retraction springs 4123 is to ensure that the movable support bar assembly 420 is opened after the main body assembly 410 of the mandrel support bar loses its thrust, that is, to allow the movable support bar assembly 420 to retract into the main body assembly 410 of the mandrel support bar.

[0100] The movable push rod 430 includes a tapered end 431 and a guide groove end 432. When the movable push rod 430 pushes the movable support bar assembly 420, the guide groove end 432 can slide and engage with the movable support bar 421. The front end of the movable push rod 430 is a tapered end 431, ensuring that the movable push rod 430 matches the movable support bar assembly 420 step by step when it is pushed.

[0101] When the movable push rod 430 slides forward, the tapered end 431 pushes the movable support bar assembly 420 outward. When pushed to the front end, all the movable support bar assemblies 420 and the mandrel support bar main body assembly 410 are supported outward to the position that meets the size requirements. In this way, it can play a good internal support role when the diameter is reduced. Conversely, when the movable push rod 430 is pushed back, the mandrel support bar main body assembly 410 loses the thrust and retracts into the mandrel support bar main body assembly 410 under the thrust of the compression spring 4123. In this way, the entire mandrel support mold 400 can be easily removed.

[0102] Please see Figure 27 As shown in one embodiment of the present invention, for aluminum alloy tubes with an outer surface that is conical with a large cross-section in the middle and small at both ends, and an inner surface with a regular, equiangularly distributed circumferential groove structure and uniform wall thickness in all areas, spinning or bi-half stamping forming methods are used to meet product manufacturing requirements. However, this method suffers from low processing efficiency, poor processing quality, and inability to guarantee internal dimensions. Casting or high-pressure die casting methods, on the other hand, suffer from defects such as poor appearance, low yield, high processing costs, uneven internal grain structure, and substandard finished product performance. To address the various drawbacks of traditional manufacturing methods and meet product processing requirements, a faster, more efficient, and lower-cost method is needed to manufacture the product.

[0103] This invention is applicable to processing aluminum products with various variable cross-sectional outer diameters, regular shapes with different internal shape and size requirements, all shapes being distributed in a uniformly angled circular pattern around the product's internal circumference, and requiring high wall thickness. The following... Figure 28 This section explains the product's external structure and internal design.

[0104] Furthermore, the aluminum tubes with different cross-sections and special internal shapes obtained by this invention can also be used for other processing techniques. For example, they can be used as process parts in hydroforming. More complex aluminum products can be manufactured using internal high-pressure forming processes on this structure, such as... Figure 29 Aluminum alloy hydraulic hoses with different structures.

Claims

1. A method for forming a pipe with different internal and external cross-sections, characterized in that, Includes the following steps: S100. Confirm the specifications of the initial blank cylindrical hollow tube (110); S200. Analyze the distribution of the wall thickness increase after the initial blank cylindrical hollow tube (110) is reduced in diameter after the specifications are confirmed. Based on the thickening results in different areas, reverse the thickness that needs to be reduced in the corresponding area of ​​the initial blank cylindrical hollow tube (110) and obtain the thinned blank cylindrical hollow tube (120). S300. Place the thinned blank cylindrical hollow tube (120) in the variable wall thickness tube diameter processing mold (200) to obtain a variable wall thickness tube (130) with the same outer diameter but different wall thickness. S400, Place the variable wall thickness pipe (130) in the variable cross-section processing mold (300), and simultaneously insert the mandrel support mold (400) into the core of the variable wall thickness pipe (130). When the variable cross-section processing mold (300) is working, the outer and inner surfaces of the variable wall thickness pipe (130) are processed simultaneously to finally obtain finished pipes with different inner and outer surfaces and variable cross-sections and uniform wall thickness distribution in all areas. The variable cross-section processing mold (300) includes a power unit (310), a base and guide device (320), a lever device (330), and a variable cross-section mold body (340). The base and guide device (320) is fixedly connected to the power unit (310). The variable cross-section mold body (340) is located inside the base and guide device (320). One end of the lever device (330) is connected to the variable cross-section mold body (340), and the other end is connected to the power unit (310). When the power unit (310) rotates, it can drive the base and guide device (320), the lever device (330), and the variable cross-section mold body (340) to rotate synchronously. When the power unit (310) performs telescopic movements, it can enable the lever device (330) to drive the variable cross-section mold body (340) to perform axial reciprocating movements inside the base and guide device (320).

2. The forming method for pipes with different internal and external cross-sections according to claim 1, characterized in that, The variable wall thickness pipe diameter processing mold (200) includes a variable wall thickness pipe diameter lower mold (210), a variable wall thickness pipe diameter upper mold (220), a variable wall thickness pipe diameter left mandrel (230) and a variable wall thickness pipe diameter left mandrel (240). In use, the thinned blank cylindrical hollow tube (120) is placed in the variable wall thickness tube diameter lower mold (210); after the variable wall thickness tube diameter lower mold (210) and the variable wall thickness tube diameter upper mold (220) are closed, the variable wall thickness tube diameter left mandrel (230) and the variable wall thickness tube diameter left mandrel (240) move towards each other or away from each other between the variable wall thickness tube diameter lower mold (210) and the variable wall thickness tube diameter upper mold (220) to extrude the thinned blank cylindrical hollow tube (120) and obtain the variable wall thickness tube (130).

3. The forming method for pipes with different internal and external cross-sections according to claim 1, characterized in that, The power unit (310) includes a hydraulic cylinder (311), a driven gear (312), a motor, and a driving gear; the output shaft of the hydraulic cylinder (311) passes through the driven gear (312) and a tapered joint (3111) is fixed at its rear end, and the tapered joint (3111) can rotate relative to the output shaft of the hydraulic cylinder (311); the output shaft of the motor is coaxially connected to the driving gear, and the driving gear meshes with the driven gear (312). When the motor rotates, the driving gear drives the driven gear (312) to rotate.

4. The forming method for pipes with different internal and external cross-sections according to claim 3, characterized in that, The base and guide device (320) includes a first rotating shaft seat (321), a second rotating shaft seat (322), a push rod bracket (323), and a guide connecting frame (324); the driven gear (312), the first rotating shaft seat (321), and the second rotating shaft seat (322) are arranged coaxially in sequence; the two ends of the push rod bracket (323) are respectively connected to the first rotating shaft seat (321) and the driven gear (312), and the two ends of the guide connecting frame (324) are respectively fixedly connected to the first rotating shaft seat (321) and the second rotating shaft seat (322).

5. The forming method for pipes with different internal and external cross-sections according to claim 4, characterized in that, A cross-shaped hollow space (3211) is provided at the center of both the first rotating shaft seat (321) and the second rotating shaft seat (322); and around the center of the first rotating shaft seat (321), a plurality of equally angularly distributed opening slots (3212) are provided at the edge of the first rotating shaft seat (321), with the depth direction of the opening slots (3212) facing the four corners of the cross-shaped hollow space (3211); and the opening slots (3212) and the cross-shaped hollow space (3211) are not connected, and an installation space (3213) is provided between them. Multiple push rod supports (323) are distributed in equal-angle circles around the center of the first rotating shaft seat (321). One end is connected to the first rotating shaft seat (321) at the installation space (3213), and the other end is connected to the driven gear (312). The conical joint (3111) is located between the multiple push rod supports (323).

6. The forming method for pipes with different internal and external cross-sections according to claim 5, characterized in that, The two ends of multiple guide connecting frames (324) are respectively between two adjacent corners of the cross-shaped hollow space (3211) of the first rotating shaft seat (321) and the second rotating shaft seat (322), and are fixedly connected to the first rotating shaft seat (321) and the second rotating shaft seat (322). The interval between two adjacent guide connecting frames (324) is connected to the four corners of the two cross-shaped hollow spaces (3211) to form a guide space (3221). The variable cross section mold body (340) is located in the guide space (3221).

7. The forming method for pipes with different internal and external cross-sections according to claim 6, characterized in that, The lever device (330) includes a lever bracket (331), a movable lever (332), and an inclined push rod (333); the lever bracket (331) is connected to two adjacent guide connecting frames (324) near the first rotating shaft seat (321); the movable lever (332) is pin connected to the lever bracket (331), and one end passes through the opening slot (3212) and is hinged to the inclined push rod (333), and the other end is hinged to the variable cross-section mold body (340); the inclined push rod (333) passes through the push rod bracket (323) and is connected to the dovetail joint (3111) in a dovetail groove manner.

8. The method for forming tubular materials with different internal and external cross-sections according to claim 7, characterized in that, The variable cross-section mold body (340) includes a diameter reduction component (341) and a movable connecting component (342); one end face of the diameter reduction component (341) is connected to the movable connecting component (342), and the other end of the movable connecting component (342) is hinged to the movable lever (332); the other end face of the diameter reduction component (341) is the processing and forming cavity area; the variable wall thickness pipe (130) is located inside the diameter reduction component (341), and the variable cross-section mold body (340) reciprocates in the guide space (3221) to reduce the outer diameter of the variable wall thickness pipe (130).

9. The forming method for pipes with different internal and external cross-sections according to claim 8, characterized in that, The diameter reduction assembly (341) includes multiple diameter reduction mold bodies (3411), and the multiple diameter reduction mold bodies (3411) are circumferentially distributed. Each diameter reduction mold body (3411) has a corresponding movable connector (342) for connection. The multiple diameter reduction mold bodies (3411) are located in the guide space (3221) respectively. When the multiple diameter reduction mold bodies (3411) are enclosed, they form a complete processing and forming cavity area.

10. The forming method of pipes with different internal and external cross-sections according to claim 9, characterized in that, The movable connection assembly (342) includes a movable block (3421), a linear guide block (3424), and a mold locking block (3425). One of the four sides of the movable block (3421) is provided with a dovetail fixing groove (3422), and the slide bar (3412) of the reduced diameter mold body (3411) is engaged in the dovetail fixing groove (3422). The side opposite to the dovetail fixing groove (3422) is provided with a lug (3423), and the lug (3423) is hinged to the other end of the movable lever (332). The linear guide block (3424) is fixedly located on the other two sides of the movable block (3421), and the linear guide block (3424) contacts the inner wall of the guide space (3221). The mold locking block (3425) is detachably connected to the front end of the movable block (3421), and the front end of the movable block (3421) faces the second rotating shaft seat (322).

11. The forming method for pipes with different internal and external cross-sections according to claim 1, characterized in that, The mandrel support mold (400) includes a mandrel support strip main body assembly (410), a movable support strip assembly (420), and a movable push rod (430); the movable support strip assembly (420) is located inside the mandrel support strip main body assembly (410), and the size of the movable support strip assembly (420) is consistent with the concave rib inside the finished pipe. The spacing and distribution between two adjacent mandrel support strips (4121) in the mandrel support strip main body assembly (410) correspond one-to-one with the convex rib inside the finished pipe; and the movable support strip assembly (420) can slide along the mandrel support strip main body assembly (410). The movable push rod (430) and the movable support bar assembly (420) slide together; after the mandrel support mold (400) is opened, its outer contour is the molded imprint of the internal strip groove of the finished pipe.

12. The forming method for pipes with different internal and external cross-sections according to claim 11, characterized in that, During processing, the movable push rod (430) is inserted into the main body assembly (410) of the mandrel support bar, pushing the movable support bar assembly (420) to slide along the main body assembly (410) of the mandrel support bar and abut against the movable push rod (430), thus opening the main body assembly (410). When the variable cross-section processing mold (300) is working, the inner surface of the variable wall thickness pipe (130) is processed simultaneously. After processing is completed, the movable push rod (430) is withdrawn from the main body assembly (410), and the main body assembly (410) of the mandrel support bar loses its support. The opened main body assembly (410) of the mandrel support bar retracts and is taken out from the core of the finished pipe.

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