Method and device for forming a multi-ribbed or bossed cylindrical part by inside-expanding and outside-rotating composite extrusion

Abstract

The application discloses a method and device for multi-inner-ring-rib or boss inner-expanding outer-rotating composite extrusion forming of a cylindrical part, and the device comprises an inner-expanding mechanism, an axial loading mechanism, a radial loading mechanism and a rotating loading mechanism; the inner-expanding mechanism comprises a split die set composed of alternately arranged first split dies and second split dies; the first split die is provided with an inner inclined surface matched with an inclined surface of a wedge block and a side inclined surface matched with a surface of the second split die; and the bottom of the split die set is slidably connected with a T-shaped groove of a base through a T-shaped hanging table. The method comprises the following steps: starting the axial loading mechanism to drive the wedge block to move downward, so that the split die set is synchronously expanded radially to extrude the inner wall of a blank and preliminarily form the inner ring rib or boss; starting the rotating loading mechanism to drive the inner-expanding mechanism and the blank to rotate, and simultaneously starting the radial loading mechanism to drive a conical roller to continuously roll the outer wall of the blank, so that the final forming is completed.

Description

Technical Field

[0001] This invention belongs to the field of plastic processing technology of light metal materials, and specifically relates to an internal expansion-external rotation composite extrusion forming method and apparatus for manufacturing cylindrical parts with internal ring ribs or internal bosses. Background Technology

[0002] like Figure 1 As shown, thin-walled cylindrical parts with high inner ring ribs or discontinuous bosses are in high demand in high-end equipment fields such as aerospace due to their small internal space, numerous characteristic structures, and rib height to wall thickness ratios that can be more than 3 times. However, they are extremely difficult to form. Currently, the traditional manufacturing processes for this type of product have the following limitations:

[0003] Direct casting: It can directly form complex structures. Although it eliminates forging and extrusion processes and has a high material utilization rate, the internal grain structure of the product is coarse, which is prone to defects such as porosity, inclusions and gas, making it difficult to meet high performance requirements.

[0004] Extrusion + machining: such as Figure 2 As shown, extrusion can refine grains, but subsequent machining will severely damage the metal flow lines, and the material utilization rate is low, resulting in high production costs.

[0005] Traditional rotary extrusion molding: such as Figure 3 As shown, the downward movement of the intermediate wedge expands the segmented mold, generating radial compression on the cylindrical blank. Combined with the rotation of the blank driven by the die, this is achieved through patents from North China University (CN201910969784, CN201910969785) that disclose related molds and methods. While this technology has achieved good results in forming inner ring ribs, a problem exists: it requires a strict height of the segmented mold. When forming one or two inner ring ribs, a lower mold height provides greater rigidity during forming, resulting in less flexural deformation. Furthermore, with fewer inner ring ribs, the radial loading force is smaller, and the equipment requirements are lower. However, forming components with high height and a large number of inner ring ribs, as proposed in this invention, presents significant challenges. This is because the segmented mold is relatively high and requires heating to 400-500℃, leading to severe flexural deformation during the forming process (e.g., Figure 3As shown in the diagram, this results in the formation of the inner ring ribs near the opening, but the inner ring ribs in the middle cannot be formed. Furthermore, the die cannot be restored after deformation. Alternatively, due to the large number of ribs formed in one operation, the radial loading force is insufficient, resulting in the formed inner ring ribs being too low. Therefore, traditional rotary extrusion forming has significant limitations and cannot be applied to the manufacture of large-sized cylindrical parts with multiple inner ring ribs. It is particularly important to note that this method is only suitable for forming cylindrical parts with continuous inner ring ribs. If used to manufacture parts with discontinuous boss structures, a complete rotating component must first be formed, and then excess material must be removed through machining. This process not only causes serious waste of raw materials but also disrupts the extruded product flow line, compromising mechanical properties.

[0006] Spin forming: This process can integrally form complex internal structures through continuous local deformation, significantly improving the overall rigidity and strength of parts, while also offering good material utilization and high forming accuracy. However, this process also presents several drawbacks and challenges. First, the forming process involves relatively many steps, making process control complex. More significantly, workpieces are prone to cracking during spinning, placing stringent demands on material properties, process parameters, and mold design. Its most significant technical limitation lies in the severely restricted height of the formed ribs; theoretically, the maximum rib height in a single forming operation is roughly equivalent to the radial feed of the spinning rollers. Furthermore, behind the roller's movement path, insufficient plastic flow can easily lead to material accumulation, such as... Figure 4 As shown, this kind of material accumulation can lead to incomplete filling of the ribs, unclear outlines, or uneven wall thickness, which directly affects the quality and dimensional accuracy of the parts and is a key problem that needs to be solved in process control. Summary of the Invention

[0007] The purpose of this invention is to provide an internal expansion-external rotation composite extrusion forming method and apparatus. This technology overcomes the problem that traditional methods cannot form inner ring high ribs and discontinuous bosses, ensuring the product extrusion streamline, reducing forming defects, and improving material utilization.

[0008] To achieve the above objectives, the solution of the present invention is: a method for compound extrusion forming of cylindrical parts with multiple inner ring ribs or bosses, comprising an inner expansion and outer rotation mechanism, wherein:

[0009] The internal expansion mechanism includes at least a segmented module and a wedge; the segmented module consists of at least three first segmented modules and an equal number of second segmented modules, with the first and second segmented modules spaced apart.

[0010] The first segmented die has three inclined surfaces: a left inclined surface, a right inclined surface, and an inner inclined surface. The inner inclined surface mates with the inclined surface of the wedge block. The inner surface of the second segmented die is an inner plane, which mates with either the left or right inclined surface of the first segmented die. The outer surfaces of both the first and second segmented dies are ribbed structures. The contact area between the ribbed structure of the first segmented die and the blank is smaller than that between the ribbed structure of the second segmented die and the blank.

[0011] The wedge has an inverted pyramidal structure, with a first inclined surface and a second inclined surface on its outer surface. The first inclined surface mates with the first segmented mold, while the second inclined surface does not contact the second segmented mold.

[0012] The forming method includes at least the following steps:

[0013] Step 1: Blank Installation

[0014] The cylindrical blank is fitted onto the outside of the segmented module; before the inner expansion forming, the segmented module has a small-diameter, near-circular structure.

[0015] Step 2: Internal Expansion Shaping

[0016] The axial loading mechanism is activated, driving the wedge block downwards. The first inclined surface of the wedge block pushes the first segmented mold to move radially outwards, while the first segmented mold pushes the second segmented mold to expand radially in sync. At the same time, it squeezes the inner wall of the blank, causing the blank to flow towards the rib and groove structure on the segmented mold assembly. When the wedge block descends to the designated position, the segmented mold assembly changes from a small-diameter near-circular structure to a complete large-diameter circular structure, the inward expansion forming is completed, and the inner ring rib or discontinuous boss structure is initially formed.

[0017] Step 3: External rotary roll forming:

[0018] The rotary loading mechanism is activated, driving the inner expansion mechanism and the billet to rotate synchronously. At the same time, the radial loading mechanism is activated, with the vertical drive unit and the horizontal drive unit driving the conical rollers to perform axial and radial feed respectively. The conical rollers continuously roll the outer wall of the rotating billet from bottom to top, forcing the billet to flow further into the rib structure and fill it, thus completing the final forming.

[0019] Furthermore, steps two and three include at least the following two combinations:

[0020] Method 1, Expansion followed by rotation: After the internal expansion forming in step 2 is completed, the external rotation roll forming in step 3 is then carried out.

[0021] Method 2, Synchronous Expansion and Rotation: The internal expansion forming in step 2 and the external rotation rolling forming in step 3 overlap at least partially in time. Specifically, the conical rollers begin rolling during the process of the wedges opening up the segmented modules.

[0022] Further, the split module is composed of four first split dies and four second split dies; the outer surface of the wedge block correspondingly has four first inclined surfaces and four second inclined surfaces.

[0023] Further, the split module is movably arranged on the base. Specifically: there are T-shaped grooves distributed annularly on the base, and the number of T-shaped grooves is the same as the number of split dies. A T-shaped hanging platform is correspondingly arranged at the bottom of each split die. The T-shaped hanging platform of the split die cooperates with the T-shaped groove of the base to ensure that the paths of the internal expansion mechanism during radial movement are consistent; the bottom of the base is fixed to the rotating workbench of the rotary loading mechanism to play a role in transmitting torque.

[0024] Further, during the internal expansion forming process in step two, the second split dies gradually separate, but at the same time, the first split dies will gradually block the gaps between adjacent second split dies, and finally form a large-diameter and complete circular structure.

[0025] Further, the axial loading mechanism includes a hydraulic press slider, a main shaft, a rotating sleeve, and a thrust bearing arranged between the two. The bottom of the rotating sleeve is connected to the wedge block;

[0026] In step two, the axial loading mechanism is started, driving the hydraulic press slider to move downward, and driving the wedge block to move downward through the main shaft and the rotating sleeve; under the action of external driving, the wedge block drives the rotating sleeve to generate a circumferential rotational movement.

[0027] Further, in step three, the radial loading mechanism is started. Its vertical driving unit drives the auxiliary slider to perform axial movement, and the horizontal driving unit drives the roller frame to perform radial movement, thereby making the conical rollers installed on the roller frame roll press the outer wall of the blank.

[0028] Further, the cross-section of the conical roller is an isosceles trapezoid structure with a narrow upper part and a wide lower part;

[0029] When forming the inner ring ribs, the axial height H of the conical roller satisfies: h < H < h1 + h2 + h, where h is the axial height of a single groove of the rib groove structure, and h1 and h2 are the axial heights of adjacent ribs of the rib groove structure;

[0030] When forming discontinuous bosses, the axial height H of the conical roller satisfies: 1.5h < H < 2h, where h is the axial height of a single groove of the rib groove structure.

[0031] A cylindrical part multi-inner ring rib or boss internal expansion and external rotation composite extrusion forming device, which is applied to the above-mentioned cylindrical part multi-inner ring rib or boss internal expansion and external rotation composite extrusion forming method, includes the following mechanisms:

[0032] The internal expansion mechanism includes at least a segmented module and a wedge. The segmented module consists of at least three first segmented modules and an equal number of second segmented modules, with the first and second segmented modules spaced apart. The first segmented module has three inclined surfaces: a left inclined surface, a right inclined surface, and an inner inclined surface, with the inner inclined surface engaging with the inclined surface of the wedge. The inner surface of the second segmented module is an inner plane, which engages with either the left or right inclined surface of the first segmented module. The outer surfaces of both the first and second segmented modules are grooved structures, with the contact area between the grooved structure of the first segmented module and the blank being smaller than that of the grooved structure of the second segmented module. The wedge has an inverted pyramidal structure and is used to drive the radial movement of the segmented modules. Its outer surface has a first inclined surface and a second inclined surface, with the first inclined surface engaging with the first segmented module and the second inclined surface not engaging with the second segmented module.

[0033] An axial loading mechanism is used to drive the wedge block to move axially.

[0034] The radial loading mechanism is used to drive the tapered rollers to perform axial and radial feed, so that the tapered rollers continuously roll the outer wall of the rotating billet from bottom to top;

[0035] A rotary loading mechanism is used to drive the internal expansion mechanism and the billet.

[0036] Furthermore, the axial loading mechanism includes a hydraulic press slider, a main shaft, and a rotating sleeve; the upper end of the main shaft is fixedly connected to the hydraulic press slider, the lower end of the main shaft is movably connected to the rotating sleeve, and the bottom of the rotating sleeve is connected to the wedge block by bolts and keys to transmit axial force and torque; the interior of the rotating sleeve is connected to the main shaft by two sets of thrust bearings, and the top of the rotating sleeve is sealed and axially positioned by a cover plate;

[0037] The radial loading mechanism includes a vertical drive unit, a secondary slider driven by the vertical drive unit, a horizontal drive unit mounted on the secondary slider, and a roller frame driven by the horizontal drive unit, wherein a tapered roller for rolling the outer wall of the blank is mounted on the roller frame.

[0038] After adopting the above solution, the beneficial effects of the present invention are as follows:

[0039] (1) The inner expansion-outer rotation composite extrusion forming method of the present invention can achieve precise forming of cylindrical parts with inner ring high ribs or discontinuous bosses by the coordinated loading of inner expansion of the segmented module and outer rotation of the conical roller.

[0040] Compared to traditional spinning processes, this method employs two paths: "expansion followed by spinning" or "simultaneous expansion and spinning," combining a reverse extrusion and forward extrusion mechanism to significantly improve the filling efficiency of the rib grooves from the billet. The height of the ring ribs or bosses formed by this method can reach twice the radial feed amount of the conical roller, and it effectively avoids billet accumulation and folding defects, improving mechanical properties and billet utilization while ensuring the integrity of the part's streamline.

[0041] (2) The forming device of the present invention adopts a multi-directional coupling loading structure, including: an axial loading mechanism integrating a main shaft, a thrust bearing and a rotating sleeve to achieve stable transmission of large axial loads under the condition of die rotation; a radial loading mechanism is jointly controlled by vertical and horizontal hydraulic cylinders to support the axial-radial multi-degree-of-freedom feeding of conical rollers; the inner expansion mechanism adopts a split die combined structure and a T-shaped hanging platform guide to ensure synchronous and gapless radial movement, solving the technical problem of easy material overflow in traditional split die groups. The whole machine has high rigidity, high synchronism and high reliability, providing reliable equipment support for the composite forming process.

[0042] (3) The present invention optimizes the parameter range of conical rollers: when forming inner ring ribs, the suitable range of the axial height H of the conical roller needs to satisfy h < H < (h1 + h2 + h); when forming discontinuous bosses, the suitable range of the axial height H of the conical roller needs to satisfy 1.5h < H < 2h to balance the forming force and the billet fluidity; the inclination angle of the conical roller is maintained at 3° < α < 5°, effectively guiding the billet flow direction and suppressing agglomeration. This method shows remarkable performance in aspects such as increasing the feature height, improving the forming uniformity, and reducing the defect rate, and is applicable to the manufacturing requirements of high-precision and high-performance components in fields such as aerospace and high-end equipment, having important engineering application value. Description of the Drawings

[0043] Figure 1 is a schematic structural diagram of a thin-walled cylindrical part with high inner ring ribs or discontinuous bosses;

[0044] Figure 2 is a schematic diagram of the extrusion + machining forming method;

[0045] Figure 3 is a schematic diagram of the rotary extrusion forming method;

[0046] Figure 4 is a schematic diagram of the spinning forming method;

[0047] Figure 5 is a three-dimensional view of the inner expansion - external rotation composite extrusion forming device of the present invention;

[0048] Figure 6 is a sectional view of the inner expansion - external rotation composite extrusion forming device of the present invention (including the machine tool);

[0049] Figure 7 is a schematic structural diagram of the first split die and the second split die of the present invention;

[0050] Figure 8 is a schematic structural diagram of the wedge block of the present invention;

[0051] Figure 9 is a schematic structural diagram of the split die group and the base of the present invention;

[0052] Figure 10 This is a schematic diagram of the base and rotating worktable structure of the present invention;

[0053] Figure 11 This is a schematic diagram (top view) of the movement mode of the internal expansion mechanism of the present invention;

[0054] Figure 12 This is a schematic diagram (front view) of the movement mode of the internal expansion mechanism of the present invention;

[0055] Figure 13 This is a comparison diagram of traditional internal expansion forming and the internal expansion forming of this invention;

[0056] Figure 14 This is a cross-sectional view of the axial loading device of the present invention;

[0057] Figure 15 This is a cross-sectional view of the radial loading device of the present invention;

[0058] Figure 16 This is a cross-sectional view (excluding the machine tool) of the internal expansion-external rotation composite extrusion forming device of the present invention.

[0059] Figure 17 This is a schematic diagram of the expansion-then-rotation forming method of the present invention;

[0060] Figure 18 This is a schematic diagram of the synchronous expansion and spinning forming method of the present invention;

[0061] Figure 19 This is a schematic diagram of the material flow during the internal expansion forming and external rotation roll forming processes of the present invention;

[0062] Figure 20 A comparison diagram of the material flow and forming effect between the method of this invention and the traditional spinning forming method.

[0063] Label Explanation:

[0064] 1. Machine tools;

[0065] 2. Internal expansion mechanism; 21. First segmented mold; 211. Left inclined surface; 212. Right inclined surface; 213. Inner inclined surface; 22. Second segmented mold; 221. Inner plane; 23. Rib groove structure; 24. Wedge block; 241. First inclined surface; 242. Second inclined surface; 25. Base; 251. T-slot; 26. T-shaped hanging platform;

[0066] 3. Axial loading mechanism; 31. Hydraulic press slide block; 32. Main shaft; 33. Rotary sleeve; 34. Thrust bearing; 35. Cover plate;

[0067] 4. Radial loading mechanism; 41. Vertical drive unit; 42. Secondary slider; 43. Horizontal drive unit; 44. Roller frame; 45. Conical roller;

[0068] 5. Rotary loading mechanism; 51. Rotary worktable; 6. Ejection mechanism; 7. Billet. Detailed Implementation

[0069] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0070] This invention provides a composite extrusion forming device for cylindrical parts with multiple inner ring ribs or bosses, such as... Figures 5 to 20 As shown, it includes a machine tool 1, an internal expansion mechanism 2, an axial loading mechanism 3, a radial loading mechanism 4, and a rotary loading mechanism 5.

[0071] <Internal Expansion Organization 2>

[0072] like Figure 7 and Figure 9 As shown, the inner expansion mechanism 2 includes a segmented module, a wedge block 24, and a base 25. The segmented module consists of four first segmented modules 21 and four second segmented modules 22, which are spaced apart to form a near-circular structure with a variable diameter.

[0073] like Figure 11 As shown, the first segmented mold 21 has three inclined surfaces: the left and right sides are left inclined surface 211 and right inclined surface 212, respectively, and are symmetrically arranged; the inner side is an inner inclined surface 213, which mates with the inclined surface of the wedge block 24. The inner side of the second segmented mold 22 is an inner plane 221, which mates with either the left inclined surface 211 or the right inclined surface 212 of the first segmented mold 21.

[0074] like Figure 7 As shown, the outer sides of both the first segmented mold 21 and the second segmented mold 22 are ribbed structures 23. The ribbed structure 23 includes several raised ribs protruding from the outer surfaces of the first segmented mold 21 and the second segmented mold 22, with inner grooves between adjacent raised ribs. The grooves are used to form inner ring ribs or boss structures on the inner wall of the cylindrical blank 7.

[0075] The contact area between the rib groove structure 23 of the first segmented mold 21 and the blank 7 is much smaller than that between the rib groove structure 23 of the second segmented mold 22 and the blank 7. Figure 11 It can also be seen that the arc length of the outer side of the first segmented mold 21 is much smaller than the arc length of the outer side of the second segmented mold 22.

[0076] like Figure 8 and Figure 11 As shown, the wedge block 24 has an overall inverted pyramidal structure, with four first inclined surfaces 241 and four second inclined surfaces 242 on its outer surface, which are spaced apart. The first inclined surfaces 241 engage with the first segmented mold 21, while the second inclined surfaces 242 do not contact the second segmented mold 22.

[0077] like Figure 9 and Figure 10 As shown, the segmented module is movably mounted on the base 25. Specifically, there are eight T-shaped grooves 251 distributed in a ring on the base 25. Each segmented module has a corresponding T-shaped mounting platform 26 at its bottom. The T-shaped mounting platforms 26 of the eight segmented modules cooperate with the eight T-shaped grooves 251 of the base 25. This design ensures that the inner expansion mechanism 2 moves along the same path in the radial direction.

[0078] like Figure 10 As shown, the bottom of the base 25 is fixed to the rotating worktable 51 of the rotating loading mechanism 5 by bolts and keys to transmit torque. This is a common design and will not be described in detail in this invention.

[0079] The movement of wedge 24 and the segmented module is as follows:

[0080] like Figure 11 -① and Figure 12 As shown in ①, the wedge 24 descends, and its first inclined surface 241 pushes the first segmented mold 21 to move radially along the designated path of the T-slot 251. At this time, the left inclined surface 211 and the right inclined surface 212 of the first segmented mold 21 are completely in contact with the inner plane 221 of the adjacent second segmented mold 22, thereby pushing the second segmented mold 22 to also move along the radial path to generate radial outward extrusion on the inner wall of the blank 7. When the wedge 24 descends to the designated position, as... Figure 11 -② and Figure 12 As shown in ②, the internal expansion forming is complete. At this point, the eight segmented molds form a large-diameter, complete circular structure.

[0081] In traditional segmented modules, the gap between adjacent segmented modules gradually increases during outward expansion, such as... Figure 13 As shown at point a in ①, severe overflow occurs at the gap. However, before the outer expansion forming of the segmented module of this invention, the outer periphery of the inner expansion mechanism 2 is formed by the second segmented mold 22 into a small-diameter near-circular structure (e.g., Figure 13 As shown in ②, during the inward expansion forming process, the second segmented mold 22 gradually separates, but at the same time, the first segmented mold 21 gradually seals the gap between adjacent second segmented molds 22. This results in the eight segmented molds forming a complete circular structure larger than the initial circle at the end of the forming process, ensuring that the rib structure 23 on the outer side of the inward expansion mechanism 2 completely fits the inner wall of the blank 7 without any gaps. (See Figure ②) Figure 13 At point a. In this way, no blank 7 will overflow during the internal expansion forming process, avoiding the problem of traditional segmented mold structures requiring rotational loading to eliminate overflow.

[0082] It should be noted that the aforementioned inner expansion mechanism 2, as an independent core component of this invention, is not limited to its application in conjunction with the axial loading mechanism 3, radial loading mechanism 4, and rotary loading mechanism 5 described in this specific embodiment. The inner expansion mechanism 2 can be used as an independent mold unit in other types of extrusion forming equipment or processes, such as in conjunction with conventional hydraulic presses, mechanical presses, or other rotary forming equipment, to achieve the forming of cylindrical parts with inner ring ribs or inner boss structures.

[0083] <Axial Loading Mechanism 3>

[0084] like Figure 14 As shown, the axial loading mechanism 3 includes a hydraulic press slider 31, a main shaft 32, a rotating sleeve 33, and a thrust bearing 34 disposed between the two. The specific structure is as follows;

[0085] The upper end of the main shaft 32 is fixedly connected to the hydraulic press slider 31, and the lower end of the main shaft 32 is movably connected to the rotating sleeve 33. The bottom of the rotating sleeve 33 is connected to the wedge block 24 by bolts and keys to transmit axial force and torque. When the axial loading mechanism 3 is activated, it drives the hydraulic press slider 31 to move downward, which in turn drives the wedge block 24 downward through the main shaft 32 and the rotating sleeve 33.

[0086] Furthermore, the rotating sleeve 33 is internally connected to the main shaft 32 via two sets of thrust bearings 34, and its top is sealed and axially positioned by a cover plate 35. The configured thrust bearings 34 can meet the requirements of large axial load transmission. The main shaft 32, rotating sleeve 33, and thrust bearings 34 adopt a tight-fit structure design to ensure that the main shaft 32 remains stable and fixed when a large axial load is applied. At the same time, it can effectively reduce the impact of assembly clearance on loading accuracy.

[0087] Under external driving force, the wedge block 24 drives the rotating sleeve 33 to generate circumferential rotation, thereby realizing a composite motion path of axial loading and circumferential rotation coupling, providing stable and reliable loading conditions for the forming process under complex stress conditions.

[0088] Radial loading mechanism 4

[0089] like Figure 15 As shown, the radial loading mechanism 4 includes a vertical drive unit 41, a secondary slider 42 driven by the vertical drive unit 41, a horizontal drive unit 43 mounted on the secondary slider 42, and a roller frame 44 driven by the horizontal drive unit 43. The roller frame 44 is equipped with a tapered roller 45 for rolling the outer wall of the blank 7.

[0090] In this embodiment, the vertical drive unit 41 is a vertical hydraulic cylinder, whose piston rod is rigidly connected to the auxiliary slider 42. Guided by the machine tool column 1, the vertical hydraulic cylinder drives the auxiliary slider 42 to achieve precise axial movement, thereby ensuring motion stability and guiding accuracy during loading. The horizontal drive unit 43 is a horizontal hydraulic cylinder, whose piston rod is connected to the roller frame 44. The tapered roller 45 is mounted on the roller frame 44, and the horizontal hydraulic cylinder drives the tapered roller 45 to feed radially.

[0091] By coordinating the control of vertical and horizontal hydraulic cylinders, a 45-axis-radial composite loading motion path for the conical roller can be realized, thereby constructing a multi-degree-of-freedom loading system to adapt to the differentiated requirements of loading paths for different component geometric features and forming process parameters, and to provide stable and controllable radial loading conditions for the precise plastic forming of complex structural parts.

[0092] Regarding the resetting of the segmented mold of the present invention, additional tooling is required to assist in the process after the material forming is completed.

[0093] <Rotary Loading Mechanism 5>

[0094] like Figure 5 and Figure 16 As shown, the rotary loading mechanism 5 is connected to the base 25 of the inner expansion mechanism 2, and is used to drive the inner expansion mechanism 2, the billet 7, and the rotary sleeve 33 to rotate as a whole. This application does not limit the specific structure of the rotary loading mechanism 5; any mechanism that can achieve the above-mentioned rotary driving function is applicable to this application.

[0095] In this embodiment, the rotary loading mechanism 5 adopts the rotary module of the multi-directional loading rotary extruder independently developed and designed by North China University of Technology.

[0096] <Ejection Mechanism 6>

[0097] like Figure 16 As shown, the device may also include an ejector mechanism 6, located below the base 25. After molding is completed, the ejector mechanism 6 pushes the wedge block 24 upwards. After the wedge block 24 is removed, other auxiliary tools are used to disassemble and assemble the segmented mold. The ejector mechanism 6 can be driven by a hydraulic cylinder or a pneumatic cylinder. Its specific structure is conventional technology in the field and will not be described in detail here.

[0098] The present invention provides a method for compound extrusion forming of cylindrical parts with multiple inner ring ribs or bosses, comprising the following steps:

[0099] Step 1, Installation of billet 7:

[0100] The cylindrical blank 7 is fitted onto the outside of the segmented module of the inner expansion mechanism 2; before the inner expansion is formed, the outer periphery of the inner expansion mechanism 2 is surrounded by the second segmented module 22 to form a small-diameter near-circular structure.

[0101] Step 2: Internal Expansion Shaping

[0102] The axial loading mechanism 3 is activated, driving the hydraulic press slider 31 to move downwards. This drives the wedge block 24 downwards via the main shaft 32 and rotating sleeve 33. The first inclined surface 241 of the wedge block 24 pushes the first segmented mold 21 to move radially outwards. The first segmented mold 21 then pushes the second segmented mold 22 to expand radially in sync, simultaneously compressing the inner wall of the cylindrical blank 7 and causing the metal blank 7 to flow towards the rib structure 23 on the segmented mold assembly. When the wedge block 24 reaches the designated position, the segmented mold assembly transforms from a small-diameter near-circular structure into a complete large-diameter circular structure, completing the inward expansion forming and initially forming an inner ring rib or discontinuous boss structure.

[0103] Step 3: External rotary roll forming:

[0104] The rotary loading mechanism 5 is started, which drives the inner expansion mechanism 2, the blank 7 and the rotary sleeve 33 to rotate synchronously. Specifically, the rotary loading mechanism 5 is started, which drives the base 25 and the split mold on it to rotate. The split mold transmits the torque to the blank 7 and the wedge block 24, and the wedge block 24 further transmits the torque to the rotary sleeve 33.

[0105] At the same time, the radial loading mechanism 4 is activated, the vertical hydraulic cylinder drives the auxiliary slider 42 to move axially, and the horizontal hydraulic cylinder drives the roller frame 44 to feed radially, so that the conical roller 45 on it continuously rolls the outer wall of the rotating blank 7 from bottom to top, forcing the blank 7 to flow and fill into the rib structure 23, and complete the final forming.

[0106] Based on the thickness of the blank 7 and the height requirements of the characteristic structure, the tapered roller 45 can perform multiple rolling passes to achieve precise forming of the ring ribs and bosses.

[0107] The forming process of this invention combines internal extrusion and external rolling, and various forming paths can be achieved by adjusting the coordination of the internal and external movements. Several typical combined motion modes are listed below:

[0108] Movement Method 1: First expand, then rotate (e.g.) Figure 17 (As shown)

[0109] After the inner expansion forming in step two is completed, the outer rotation roll forming in step three is performed. That is, after the wedge block 24 moves down and completely expands the segmented module into a complete circular structure, the outer rotation roll forming is then performed.

[0110] The advantage of the pre-expansion and post-rotation forming method is that after the wedge block 24 moves downward and the segmented module is fully expanded to the predetermined size, the inner wall of the tube blank has been fully expanded and a preliminary characteristic structural outline has been formed, that is, the outline of the inner ring rib or discontinuous boss has been initially formed. This pre-forming lays the foundation for subsequent roll forming.

[0111] On the one hand, the billet 7 achieves overall plastic flow during the internal support stage, resulting in a more uniform stress distribution. This effectively avoids local stress concentration and allows for more thorough pre-filling of the rib grooves, which is beneficial for the complete forming of the feature structure and reduces the risk of defects such as folds and cracks.

[0112] On the other hand, the phased process design allows for independent and precise control of the diameter expansion and rolling parameters, reducing mutual interference between processes and improving process stability and repeatability, which is especially suitable for the manufacturing of thin-walled or high-strength billet products.

[0113] Movement mode 2: Synchronous expansion and rotation (e.g.) Figure 18 (As shown)

[0114] The inner expansion forming in step two and the outer rotation roll forming in step three overlap in time at least partially, that is, while the wedge block 24 is spreading the segmented module, the conical roller 45 begins to roll.

[0115] The advantage of the synchronous expansion and rotation forming method lies in the fact that, through the synergistic effect of internal expansion and external rotation, the rolling process begins simultaneously with the gradual opening of the segmented module by the wedge block 24, ensuring that the blank 7 is always under bidirectional force. This design can improve forming efficiency, merging the traditional step-by-step process into a continuous process, effectively shortening the overall forming cycle. At the same time, the bidirectional force mode continuously promotes the radial flow of the blank 7 towards the mold cavity area, which is especially suitable for more complex feature structures, enabling full filling and precise forming of the mold cavity within a shorter number of steps.

[0116] The following is combined with Figure 19 This is to illustrate the flow behavior of the billet 7 during the internal expansion forming and external rotation roll forming processes of the present invention.

[0117] The flow path of billet 7 during the internal expansion stage (e.g.) Figure 19 -① shown):

[0118] Under the radial expansion of the segmented module, the billet 7 undergoes expansion deformation and flows radially outward. Simultaneously, part of the billet 7, guided by the inner expansion mechanism 2, fills the groove area of ​​the rib structure 23, forming a preliminary characteristic structural outline. The deformation of the billet 7 in this stage has obvious radial outward movement and local groove filling characteristics, and its mechanical mode is similar to that of reverse extrusion forming.

[0119] The flow of billet 7 during the outer spinning stage (e.g.) Figure 19 -② shown):

[0120] Under the combined action of radial feed and axial movement of the conical roller 45, the billet 7 flows further into the groove of the rib structure 23, accompanied by significant axial extension, resulting in an increase in the height of the billet. This deformation mechanism is closer to positive extrusion forming.

[0121] In summary, the motion mode 1 (first expand and then rotate) is essentially to first perform inverse extrusion forming and then transfer to the forward extrusion process; while the motion mode 2 (simultaneous expansion and rotation) is manifested as a compound extrusion mode in which inverse extrusion and forward extrusion are carried out simultaneously. The combination and timing arrangement of different extrusion methods can be flexibly designed and regulated according to specific forming objectives to achieve precise control of the flow path of the blank 7 and the final characteristic structure.

[0122] Next, in combination with Figure 20 it will be explained the comparison between the internal expansion-external rotation composite forming method of the present invention and the traditional spinning forming technology in terms of the flow and forming effect of the blank 7.

[0123] As Figure 20 shown in -①, obvious accumulation of the blank 7 will occur behind the roller in the traditional spinning process, while no obvious accumulation of the blank 7 will occur behind the conical roller 45 in the present invention. This is because the present invention adopts an optimized conical roller 45. As Figure 20 shown in -② and ③, the cross-section of the conical roller 45 is an isosceles trapezoid structure, specifically an isosceles trapezoid structure with a narrow upper part and a wide lower part. This structure can effectively disperse local stress, promote the diversion of the blank 7, so that the deformation process is more stable and prevent the generation of defects such as folding. In addition, due to the large contact area between the conical roller 45 and the blank 7, more blanks 7 are driven to flow into the mold cavity in the form of forward extrusion or forward and reverse composite extrusion during the forming process, so that the filling efficiency of the inner ring rib and the discontinuous boss is significantly improved, and the height of the characteristic structure is further increased.

[0124] Quantitative analysis shows that when the method of the present invention is adopted, the height of the characteristic structure can reach twice the radial feed of the conical roller 45; while in the traditional spinning process, the height of the characteristic structure is usually only close to or even lower than the radial feed of the conical roller 45.

[0125] In addition, based on the previous research accumulation, the reasonable setting of the geometric parameters of the conical roller 45 has an important impact on the forming quality. When forming the inner ring rib, the axial height H of the conical roller 45 satisfies: h < H < (h1 + h2 + h), where h is the axial height of a single groove of the rib groove structure 23, and h1 and h2 are the axial heights of the adjacent ribs of the rib groove structure 23. When forming the discontinuous boss, the axial height H of the conical roller 45 satisfies: 1.5h < H < 2h, where h is the axial height of a single groove of the rib groove structure 23. If H is too large, it is easy to cause a significant increase in the radial forming force, aggravating the force-bearing burden of the mold and equipment; on the contrary, if H is too small, the flow of the blank 7 is restricted, not only reducing the forming efficiency, but also restricting the limit height that the characteristic structure can reach.

[0126] Meanwhile, the inclination angle α of the conical roller 45 should be controlled within the range of 3° < α < 5°. Within this range, the conical roller 45 can effectively guide the billet 7 to flow into the mold groove, significantly alleviate the bulging defects caused by the accumulation of billet 7 behind the conical roller 45, and help improve forming stability and surface quality.

[0127] In summary, the internal expansion-external rotation composite forming method proposed in this paper shows significant advantages in terms of increasing rib height, improving billet flowability, and suppressing defect formation. It features high forming efficiency, stable process, and reliable finished product quality, and is suitable for manufacturing precision components with high requirements for rib dimensions and forming consistency.

[0128] To further illustrate the various embodiments, the present invention provides accompanying drawings. These drawings are part of the disclosure of the present invention, primarily used to illustrate the embodiments and to explain the operating principles of the embodiments in conjunction with the relevant descriptions in the specification. With reference to these drawings, those skilled in the art should be able to understand other possible implementations and the advantages of the present invention. Components in the drawings are not drawn to scale, and similar component symbols are generally used to represent similar components.

[0129] Furthermore, the directions such as front, back, left, and right mentioned in this embodiment are only for reference and do not represent the actual directions in use. In addition, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0130] The above description is only a preferred embodiment of the present invention and is not intended to limit the design of this case. All equivalent changes made based on the key design features of this case shall fall within the protection scope of this case.

Claims

1. A method for compound extrusion forming of a cylindrical part with multiple inner ring ribs or bosses, characterized in that, The forming method at least includes the following steps: Step 1, blank installation: A cylindrical blank is sleeved outside the split module of the inner expansion mechanism. The split module is composed of at least three first split dies and the same number of second split dies arranged at intervals. The outer sides of the first split die and the second split die are both rib-groove structures; before inner expansion forming, the split module is in a small-diameter circular-like structure. Step 2, inner expansion forming: Start the axial loading mechanism to drive the wedge block of the inner expansion mechanism to move downward: The axial loading mechanism includes a hydraulic press slider, a main shaft, a rotating sleeve, and a thrust bearing arranged between the two. The bottom of the rotating sleeve is connected to the wedge block; when the axial loading mechanism is started, it drives the hydraulic press slider to move downward, and drives the wedge block to move downward through the main shaft and the rotating sleeve; the wedge block has an inverted pyramid structure, and its outer surface has a first inclined surface and a second inclined surface. The first inclined surface of the wedge block cooperates with the first split die, and the second inclined surface does not contact the second split die; the downward movement of the wedge block pushes the first split die to move radially outward, and the first split die pushes the second split die to expand radially synchronously, and at the same time squeezes the inner wall of the blank, prompting the blank to flow towards the rib-groove structure on the split module. During the inner expansion forming process, the second split die gradually separates, but at the same time the first split die will gradually block the gap between adjacent second split dies. When the wedge block moves downward to a specified position, the split module changes from a small-diameter circular-like structure to a complete large-diameter circular structure, and the inner expansion forming ends, initially forming an inner ring rib or a discontinuous boss structure. Step 3, external rotary roll forming: Start the rotary loading mechanism to drive the inner expansion mechanism and the blank to rotate synchronously; at the same time, start the radial loading mechanism, and drive the conical roller to perform axial feeding and radial feeding respectively by a vertical driving unit and a horizontal driving unit, so that the conical roller continuously rolls the outer wall of the rotating blank from bottom to top, forcing the blank to further flow and fill into the rib-groove structure to complete the final forming; the cross-section of the conical roller is an isosceles trapezoid structure with a narrow upper part and a wide lower part. When forming an inner ring rib, the axial height H of the conical roller satisfies: h < H < h1 + h2 + h, where h is the axial height of a single groove of the rib-groove structure, and h1 and h2 are the axial heights of adjacent ribs of the rib-groove structure. When forming a discontinuous boss, the axial height H of the conical roller satisfies: 1.5h < H < 2h, where h is the axial height of a single groove of the rib-groove structure.

2. The method for compound extrusion forming of cylindrical parts with multiple inner ring ribs or bosses expanding inward and rotating outward as described in claim 1, characterized in that: The above Step 2 and Step 3 at least include the following two cooperation methods: Method 1, expand first and then rotate: After the inner expansion forming in Step 2 is completed, then perform the external rotary roll forming in Step 3. Method 2, synchronous expansion and rotation: The inner expansion forming in Step 2 and the external rotary roll forming in Step 3 at least partially overlap in time. Specifically, during the process of the wedge block expanding the split module, the conical roller starts to roll.

3. The method for compound extrusion forming of cylindrical parts with multiple inner ring ribs or bosses expanding inward and rotating outward as described in claim 1, characterized in that: The first split die has three inclined surfaces, namely a left inclined surface, a right inclined surface, and an inner inclined surface. The inner inclined surface cooperates with the inclined surface of the wedge block; the inner side surface of the second split die is an inner flat surface, and its inner flat surface cooperates with the left inclined surface or the right inclined surface of the first split die.

4. The method for compound extrusion forming of cylindrical parts with multiple inner ring ribs or bosses expanding inward and rotating outward as described in claim 1, characterized in that: The segmented module is movably mounted on the base. Specifically, the base has a ring of T-slots, the same number as the number of segmented modules. Each segmented module has a corresponding T-shaped mounting platform at its bottom. The T-shaped mounting platform of the segmented module cooperates with the T-slots of the base to ensure that the inner expansion mechanism moves along the same path in the radial direction. The bottom of the base is fixed to the rotating worktable of the rotating loading mechanism to transmit torque.

5. The method for compound extrusion forming of cylindrical parts with multiple inner ring ribs or bosses expanding inward and rotating outward as described in claim 1, characterized in that: In step three, the radial loading mechanism is activated. Its vertical drive unit drives the auxiliary slider to move axially, and its horizontal drive unit drives the roller frame to move radially, thereby causing the conical rollers mounted on the roller frame to roll and press the outer wall of the blank.

6. A composite extrusion forming device for cylindrical parts with multiple inner ring ribs or bosses, characterized in that: The method for compound extrusion forming of a cylindrical part with multiple inner ring ribs or bosses, as described in any one of claims 1 to 5, includes the following mechanism: The internal expansion mechanism includes at least a segmented module and a wedge. The segmented module consists of at least three first segmented modules and an equal number of second segmented modules, with the first and second segmented modules spaced apart. The first segmented module has three inclined surfaces: a left inclined surface, a right inclined surface, and an inner inclined surface, with the inner inclined surface engaging with the inclined surface of the wedge. The inner surface of the second segmented module is an inner plane, which engages with either the left or right inclined surface of the first segmented module. The outer surfaces of both the first and second segmented modules are grooved structures, with the contact area between the grooved structure of the first segmented module and the blank being smaller than that of the grooved structure of the second segmented module. The wedge has an inverted pyramidal structure and is used to drive the radial movement of the segmented modules. Its outer surface has a first inclined surface and a second inclined surface. The first inclined surface mates with the first segmented mold, while the second inclined surface does not contact the second segmented mold. An axial loading mechanism is used to drive the wedge block to move axially. The radial loading mechanism is used to drive the tapered rollers to perform axial and radial feed, so that the tapered rollers continuously roll the outer wall of the rotating billet from bottom to top; A rotary loading mechanism is used to drive the internal expansion mechanism and the billet; The axial loading mechanism includes a hydraulic press slider, a main shaft, and a rotating sleeve; the upper end of the main shaft is fixedly connected to the hydraulic press slider, the lower end of the main shaft is movably connected to the rotating sleeve, and the bottom of the rotating sleeve is connected to the wedge block by bolts and keys to transmit axial force and torque; the inside of the rotating sleeve is connected to the main shaft through two sets of thrust bearings, and the top of the rotating sleeve is sealed and axially positioned by a cover plate. The radial loading mechanism includes a vertical drive unit, a secondary slider driven by the vertical drive unit, a horizontal drive unit mounted on the secondary slider, and a roller frame driven by the horizontal drive unit, wherein a tapered roller for rolling the outer wall of the blank is mounted on the roller frame.

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