CN113600634A

CN113600634A - Extrusion forming method for cylindrical part with boss in shape

Info

Publication number: CN113600634A
Application number: CN202110890383.4A
Authority: CN
Inventors: 张宝红; 何金文; 魏增; 宁生鹏; 李成龙; 方敏; 杨勇彪
Original assignee: North University of China
Current assignee: North University of China
Priority date: 2021-08-04
Filing date: 2021-08-04
Publication date: 2021-11-05
Anticipated expiration: 2041-08-04
Also published as: CN113600634B

Abstract

The invention discloses an extrusion forming method of a cylindrical part with a boss in the shape, wherein a prestressed ring falls into the bottom of a slideway, a left-flap female die and a right-flap female die are spliced and pressed in a conical hole, so that the left-flap female die, the right-flap female die and the conical hole are self-locked, a push rod is positioned in a forming channel and forms a variable forming cavity with the forming channel, at least one layer of groove is exposed in the variable forming cavity, and a blank is placed in the variable forming cavity; the forming process comprises two stages, namely, the male die descends to extrude the blank in the variable forming cavity, and the blank flows to fill the current variable forming cavity; secondly, the male die is continuously pressed down, the blank flows upwards along the side wall of the forming channel, the blank slides upwards through the groove belt-hanging female die assembly, and then the blank is continuously filled in the subsequently exposed variable forming cavity and the grooves of each layer; and (4) withdrawing the male die from the variable forming cavity, separating the left-segment female die from the right-segment female die after the prestressed ring is separated, and taking out the processed blank. The invention realizes the one-step forming of the cylindrical part with the boss.

Description

Extrusion forming method for cylindrical part with boss in shape

Technical Field

The invention relates to the technical field of extrusion forming methods of cylindrical parts, in particular to an extrusion forming method of a cylindrical part with a boss in the shape.

Background

The cylinder part has wide application in the fields of automobile manufacturing, high-speed trains, aerospace, military industry and the like. At present, the boss forming of the cylindrical part with the boss is the technical bottleneck of plastic forming of the thin-wall cylindrical part.

At present, the forming of a common cylindrical part is combined with the mode operation of multiple modes such as machining, extrusion forming, spinning forming, casting and the like, the forming methods of the cylindrical part with the boss are mainly four, and the forming methods are two in common, wherein one method is to machine the cylindrical part with the boss through a thick-wall circular tube machine, reserve a large machining allowance, remove redundant materials and reserve a required boss part; the other method is to prepare an outer longitudinal rib cylindrical part by extrusion molding, namely, an entire outer rib is firstly formed, and then bosses are processed one by one through numerical control; and casting and liquid die forging forming methods.

The first method does not need die sinking, has high degree of freedom, can adopt numerical control operation, automatic detection and monitoring devices, is beneficial to improving the stability of workpieces, but generates a large amount of scraps in the machining process, has serious environmental pollution and higher production cost, and in addition, the geometric external shape directly machined inevitably cuts off the metal streamline at the part, destroys the metal fiber tissue, damages the integrity of the metal fiber tissue, greatly reduces the strength and causes the reduction of the service performance of the part. The second method adopts a direct plastic forming method to replace the traditional mechanical cutting processing, not only improves the mechanical property of the cylinder part, improves the strength and the toughness of the cylinder part, but also improves the production efficiency, the material utilization rate and the service performance of the product, has simpler die design and high process operability, shortens the production period, but still damages the metal longitudinal flow line. The third method has the advantages that the application range of the casting is wide, the production cost is low, parts with complex shapes can be produced, but due to the existence of the lug bosses, the casting has a plurality of hot spots, the tendency of generating shrinkage cavity and shrinkage porosity defects is large, and the mechanical property of the cast product is low; the casting is easy to deform due to the fact that large stress is generated due to the fact that the temperature field is not uniform, and therefore the mechanical property and the precision of the casting are difficult to meet the requirements of high-performance parts such as aerospace, weapons and the like. The fourth liquid forging is to pour the metal in a liquid state and solidify the metal under certain pressure, so that a product with a compact structure can be obtained, the mechanical property of the product is higher than that of a casting, the metal compactness of the liquid forging needs to be restrained, a male die needs to be designed more complexly, the control cost is increased, and the strength of the product is lower than that of a formed part prepared by an extrusion forming process; therefore, the extrusion forming preparation of the outer longitudinal rib cylindrical part has better advantages in all aspects, and only needs subsequent machining treatment, thereby damaging axial flow lines and reducing the material utilization rate.

At present, a small amount of extrusion forming molds with cylindrical parts with bosses in the shapes exist, and mechanism design for difficult demolding of boss structures is also provided, such as an inclined guide pillar core-pulling push tube demolding method, but in actual engineering, subsequent machining is mostly needed after extrusion forming, a formed part and a female die need to be pushed out at the same time, and manual splitting is carried out to take out the formed part, so that a mold and a corresponding method for forming the cylindrical parts with the bosses in the shapes at one time are lacked at present.

Disclosure of Invention

The present invention has been made in view of the above problems. The invention aims to provide an extrusion forming method of a cylindrical part with a boss in the shape, which overcomes the defects and realizes the one-step forming of the cylindrical part with the boss in the shape.

In order to achieve the above purpose, the solution of the invention is: a method for extruding and forming a cylindrical part with a boss on the appearance relates to an extruding and forming die for the cylindrical part with the boss on the appearance, and the die comprises the following steps: the lower die assembly comprises a locating ring, a female die assembly and a push rod, the locating ring is fixed on the lower die plate and is longitudinally provided with a slide, the female die assembly comprises a left-flap female die, a right-flap female die and a prestressed ring, the splicing part of the left-flap female die and the right-flap female die is a parting surface, the prestressed ring is arranged in the slide in a sliding mode, a conical hole which is inwards folded is formed in the prestressed ring, the outline of the left-flap female die and the outline of the right-flap female die are matched with the semi-conical surface of the conical hole, the left-flap female die and the right-flap female die are spliced in the conical hole along the radial direction of the parting surface to form a forming channel, the forming channel is arranged at the periphery of the push rod in a sliding mode, and multiple layers of grooves are arranged on the side wall of the forming channel along the axial direction, and the method specifically comprises the following steps of:

the first step is as follows: preparing before forming, dropping the prestress ring into the bottom of the slideway, splicing and pressing a left-flap female die and a right-flap female die in the tapered hole, enabling the left-flap female die, the right-flap female die and the tapered hole to be self-locked, enabling a push rod to be located in the forming channel, forming a variable forming cavity with the forming channel, enabling at least one layer of groove to be exposed in the variable forming cavity, placing a blank in the variable forming cavity, and aligning a male die to the variable forming cavity from the upper part;

the second step is that: the forming process comprises two stages, namely, the male die descends to extrude the blank in the variable forming cavity, and the blank flows to fill the current variable forming cavity; secondly, the male die continues to be pressed downwards, the blank flows upwards along the side wall of the forming channel, the blank is hung on the female die assembly through the groove to slide upwards, so that the variable forming cavity is prolonged, and the blank continues to fill the subsequently exposed variable forming cavity and the grooves of each layer;

the third step: and after the forming is finished, the male die is withdrawn from the variable forming cavity, the prestressed ring is separated from the left-segment female die and the right-segment female die, then the left-segment female die and the right-segment female die are separated, and the processed blank is taken out.

Furthermore, the die also comprises an inverted triangular bolt, wherein inverted triangular holes are spliced on the parting surface of the left-petal female die and the right-petal female die, and the inverted triangular holes are symmetrical along the parting surface; after the prestressed ring is separated from the left-petal female die and the right-petal female die, the inverted triangular bolt is inserted into the inverted triangular hole, the position of the inverted triangular bolt is fixed, the push rod moves upwards to drive the left-petal female die, the right-petal female die and the blank to move upwards, and then the inverted triangular bolt separates the left-petal female die from the right-petal female die.

Further, after the left-flap female die and the right-flap female die are separated, the push rod continues to move upwards to eject the workpiece above the left-flap female die and the right-flap female die.

The mould further comprises a second hollow pipe, an elongated slot transversely penetrates through the side wall of the push rod, the upper end of the elongated slot is higher than the lower surfaces of the left-flap female die and the right-flap female die when the female die assembly slides up to the highest height, a plane pin vertically slides in the elongated slot and is detachably inserted into the elongated slot, and two ends of the plane pin extend out of the elongated slot; after the male die is withdrawn from the forming cavity, the push rod drives the female die assembly and the blank to move upwards, the plane pin is inserted into the elongated slot, the push rod drives the female die assembly, the blank and the plane pin to fall down, the plane pin slides upwards along the elongated slot after contacting with the lower die plate to support the left-flap female die and the right-flap female die, the second hollow tube is supported between the upper die plate and the prestress ring, and the upper die plate moves downwards to separate the prestress ring from the left-flap female die and the right-flap female die.

Furthermore, the die also comprises a first hollow pipe, an upper die plate is used for propping the upper part of the first hollow pipe, a left-section female die and a right-section female die are propped under the first hollow pipe, and the upper die plate descends to press the left-section female die and the right-section female die in the conical hole in a splicing manner.

After the scheme is adopted, the invention has the beneficial effects that: the prestress ring falls into the bottom of the slideway, a left-segment concave die and a right-segment concave die are spliced and pressed in the conical hole, the left-segment concave die, the right-segment concave die and the conical hole are self-locked, a push rod is positioned in the forming channel and forms a variable forming cavity with the forming channel, and a blank is placed in the variable forming cavity, so that the invention can splice a forming cavity structure with an irregular shape and can be detached to take out the formed blank; at least one layer of groove is exposed in the variable forming cavity, the male die is continuously pressed downwards, the blank flows upwards along the side wall of the forming channel, the blank is hung on the female die assembly through the groove to slide upwards, the variable forming cavity is prolonged, the blank is further continuously filled in the subsequently exposed variable forming cavity, the variable forming cavity gradually extends in the length direction of the preformed cylindrical part along with the filling of the blank in the forming process, and the grooves are filled layer by layer, so that the blank can be more sufficient in the forming cavity, the outline is attached to the inner wall of the forming cavity, the insufficient filling under the traditional extrusion is reduced, the filling of each step of groove is ensured by layer, the full cavity can be filled, the forming accuracy is ensured, the one-step forming problem of the cylindrical part with the lug boss in the shape is solved, and a plurality of lugs with different heights can be formed on the outer wall of the cylindrical part.

Drawings

FIG. 1 is a schematic view of a first hollow tube pressing a left-segment female die and a right-segment female die;

FIG. 2 is a schematic view of a male descending extrusion blank of the present invention;

FIG. 3 is a schematic view of the die assembly of the present invention raised;

FIG. 4 is a schematic view of the punch of the present invention pulling a blank upward;

FIG. 5 is a schematic view of the mounting plane pin of the present invention;

FIG. 6 is a schematic view of a second hollow tube lower prestressed ring of the present invention;

FIG. 7 is a schematic view of the triangular plug of the present invention inserted into a triangular hole;

FIG. 8 is a schematic view of the separation of the left-lobe female die from the right-lobe female die and workpiece ejection according to the present invention;

FIG. 9 is a schematic view of a partially exploded structure of the present invention;

fig. 10 is a schematic diagram of a structure for separating a left-flap female die from a right-flap female die according to the present invention.

Description of reference numerals: 1-upper die plate, 2-male die, 3-lower die plate, 4-lower die assembly, 5-positioning ring, 6-female die assembly, 7-push rod, 8-slide way, 9-forming channel, 10-groove, 11-blank, 12-variable forming cavity, 13-left-flap female die, 14-right-flap female die, 15-prestressing ring, 16-parting surface, 17-conical hole, 18-triangular bolt, 19-inverted triangular hole, 20-elongated slot, 21-plane pin, 22-slide way, 23-prestressing ring slide way, 24-conical hole slide way, 25-left-flap female die slide way, 26-right-flap female die slide way, 27-first hollow tube, 28-second hollow tube, 29-left-flap female die groove, 30-right-flap female die groove, 31-stripper plate, 32-through hole, 33-lower backing plate, 34-upper backing plate, 35-countersunk screw, 36-guide groove, 37-avoiding hole, 38-rectangular hole, 39-rectangular section and 40-retaining shoulder.

Detailed Description

The invention is described in detail below with reference to the accompanying drawings and specific embodiments.

The invention relates to an extrusion forming method of a cylindrical part with a boss in the shape, which uses an extrusion forming die of the cylindrical part with the boss in the shape, and is mainly combined with a drawing 1, the extrusion forming die comprises a male die 2 fixed with an upper template 1 and a lower die assembly 4 fixed with a lower template 3, the upper template 1 is fixed on a press slide block, the lower template 3 is fixed on a press workbench, the press slide block moves up and down above the press workbench, the press is the prior art, the specific structure is not explained any more, so that the upper template 1 moves up and down above the lower template 3, and the male die 2 is driven to move up and down, in the embodiment, the male die 2 is in a vertically extending column shape; the lower die assembly 4 comprises a locating ring 5, a female die assembly 6 and a push rod 7, the locating ring 5 is fixed on the lower die plate 3, the lower die plate 1 in the embodiment comprises a lower backing plate 33 and an upper backing plate 34 which are sequentially stacked in the upward direction, the locating ring 5 is arranged above the upper backing plate 34, a plurality of countersunk screws 35 sequentially penetrate through the lower die plate 1, the lower backing plate 33 and the upper backing plate 34 from bottom to top and are in threaded connection with the locating ring 5, so that the assemblies are fixed, the lower backing plate 33 and the upper backing plate 34 support the assemblies, a slide way 8 is longitudinally arranged on the locating ring 5, the female die assembly 6 is slidably arranged in the slide way 8, a forming channel 9 longitudinally penetrates through the female die assembly 6, a plurality of layers of grooves 10 are axially arranged on the side wall of the forming channel 9, the push rod 7 penetrates through the lower die plate 1, the lower backing plate 33 and the upper backing plate 34 and is inserted into the forming channel 9 from bottom to top, the push rod 7 is plugged at the lower section of the forming channel 9, the push rod 7 and the forming channel 9 are spliced to form a variable forming cavity 12 for placing a blank 11, the male die 2 is inserted into the variable forming cavity 12 in a downward sliding mode, the blank 11 expands and fills at least one exposed layer of groove 10, the blank 11 is hung on the female die assembly 6 through the groove 10 to slide upwards, the female die assembly 6 ascends, meanwhile, the blank 11 continues to flow and fill each subsequent layer of exposed groove 10, the grooves 10 are filled layer by layer, and a preformed cylindrical part with a boss in the shape is formed in one step.

It is shown with an important point in conjunction with fig. 8 that the female die assembly 6 includes a left-petal female die 13, a right-petal female die 14, and a pre-stressed ring 15, where the joint of the left-petal female die 13 and the right-petal female die 14 is a parting surface 16, the pre-stressed ring 15 is slidably disposed in the slide 8, in this embodiment, the slide 8 is a vertically disposed hole channel, the outer contour of the pre-stressed ring 15 is correspondingly matched with the slide 8, a tapered hole 17 which is inwardly folded is formed in the pre-stressed ring 15, the outer contours of the left-petal female die 13 and the right-petal female die 14 are matched with a semi-conical surface of the tapered hole 17, the left-petal female die 13 and the right-petal female die 14 are radially movably joined along the parting surface 16 in the tapered hole 17 to form the forming channel 9, and the forming channel 9 is symmetrically disposed on both sides of the parting surface 16.

As shown in fig. 6, 7 and 8, the die further comprises an inverted triangle bolt 18, the left-half die 13 and the right-half die 14 are spliced with inverted triangle holes 19 at the splitting surface 16, the inverted triangle holes 19 are symmetrical along the splitting surface 16, the inverted triangle bolt 18 is fixed in longitudinal position and is horizontally slidably inserted into or pulled out of the inverted triangle holes 19, a plurality of inverted triangle bolts 18 and the inverted triangle holes 19 are arranged and are symmetrically arranged along the axis of the forming channel 9, in this embodiment, a guide groove 36 horizontally penetrates through the side wall of the positioning ring 5, the cross section of the guide groove 36 corresponds to the cross section of the inverted triangle bolt 18, the inverted triangle bolt 18 penetrates into the guide groove 36, the guide groove 36 limits the position of the triangle bolt 18, so that the inverted triangle bolt 18 can only horizontally slide along the guide groove 36, the pre-stressed ring 15 is provided with a position-avoiding hole 37 for the triangle bolt 18 to penetrate, the triangle bolt 18 further penetrates through the position-avoiding hole 37, the inverted triangular hole 19 is inserted or pulled out in a horizontal sliding mode.

It is emphasized that as shown in fig. 7, a long groove 20 is transversely penetrated through a side wall of the push rod 7, when an upper end of the long groove 20 is higher than lower surfaces of the left-flap female die 13 and the right-flap female die 14 when the female die assembly 6 slides up to the highest height, a flat pin 21 is vertically and detachably inserted in the long groove 20, in this embodiment, one end of the flat pin 21 is provided with a shoulder 40, a width of the shoulder 40 is larger than a width of the long groove 20, after the flat pin 21 is inserted into the long groove 20, the shoulder 40 abuts against an outer wall of the push rod 7 to limit horizontal displacement of the flat pin 21, so as to facilitate insertion of the flat pin 21, two ends of the flat pin 21 extend out of the long groove 20 to support the left-flap female die 13 and the right-flap female die 14 in a sliding manner, the height of the upper end of the long groove 20 ensures that the flat pin 21 can fully contact lower surfaces of the left-flap female die 13 and the right-flap female die 14, and when the flat pin 21 slides to a lower end of the long groove 20, the upper end of the plane pin 21 is spaced from the lower surfaces of the left-flap female die 13 and the right-flap female die 14, so that the plane pin 21 can be inserted more easily.

It is shown with the important combination of fig. 5, 9 that the vertical extension in slide 8 surface has slide rail 22, prestressing force circle 15 is provided with the cooperation prestressing force circle spout 23 of slide rail 22, vertical extension has bell mouth slide rail 24 in prestressing force circle 15's the bell mouth 17, left lamella die 13, right lamella die 14 are provided with the cooperation respectively left lamella die spout 25, right lamella die spout 26 of bell mouth slide rail 24, lower bolster 3 is equipped with rectangular hole 38, push rod 7 be provided with rectangular hole 38 sliding fit's rectangle section 39, and then the restriction push rod 7 is rotatory around the axis to prescribe a limit to position circle 5, prestressing force circle 15, left lamella die 13, right lamella die 14, push rod 7 circumferential position.

As shown in fig. 1, the male die further comprises a first hollow pipe 27, the first hollow pipe 27 is detachably sleeved outside the male die 2, the upper end of the first hollow pipe 27 is abutted to the upper die plate 1, the lower end of the first hollow pipe is abutted to the left valve female die 13 and the right valve female die 14, and then the left valve female die 13 and the right valve female die 14 are pressed down through the upper die plate 1 so as to be in stress fit with the tapered hole 17.

As shown in fig. 6, a second hollow pipe 28, the second hollow pipe 28 is sleeved outside the male die 2, the upper side of the second hollow pipe 28 is abutted to the upper die plate 1, the lower side of the second hollow pipe 28 is abutted to the prestressed ring 15, and the prestressed ring 15 can be pushed downwards through the second hollow pipe 28 to be separated from the left-flap female die 13 and the right-flap female die 14.

As shown in fig. 3, each layer of groove 10 at least includes a left half concave groove 29 and a right half concave groove 30, the left half concave groove 29 is disposed on the left half concave die 13, the right half concave groove 30 is disposed on the right half concave die 14, after the left half concave die 13 and the right half concave die 14 are spliced, each layer of the left half concave groove 29 and the right half concave die groove 30 on the groove 10 are separated from each other, so as to form a convex structure on the blank 11, but not limit the separation of the left half concave die groove 29 and the right half concave die groove 30, the left half concave die groove 29 and the right half concave die groove 30 can be also spliced into a ring-shaped groove structure.

As shown in fig. 3, the lower die assembly 4 is closed and opened at the upper part thereof with a stripper plate 31 for abutting against the blank, a through hole 32 corresponding to the position of the forming channel 9 is formed in the stripper plate 31, and the male die 2 is inserted into the variable forming chamber 12 through the through hole 32.

The extrusion forming method of the cylindrical part with the boss, which is used for forming the workpiece by using the extrusion forming die with the cylindrical part with the boss, comprises the following steps:

the first step is as follows: with particular reference to fig. 1 and 2, before preparation for forming, the prestressed ring 15 is dropped into the bottom of the slideway 8, the left-flap female die 13 and the right-flap female die 14 are spliced and pressed in the tapered hole 17, so that the left-flap female die 13, the right-flap female die 14 and the tapered hole 17 are self-locked, in this embodiment, the first hollow tube 27 is sleeved outside the punch 2, the upper template 1 is abutted against the upper part of the first hollow tube 27, the first hollow tube 27 is abutted against the left-flap female die 13 and the right-flap female die 14, the press slide moves downwards to drive the upper template 1 and the first hollow tube 27 to move downwards, the left-flap female die 13 and the right-flap female die 14 are spliced and pressed in the tapered hole 17, then the first hollow tube 27 is taken down, the push rod 7 and the forming channel 9 form a variable forming cavity 12, at least one layer of grooves 10 are exposed in the variable forming cavity 12, placing a blank 11 inside said variable forming chamber 12, with the punch 2 aligned from above with said variable forming chamber 12;

the second step is that: with particular reference to fig. 3, the forming process includes two stages, namely, the male die 2 descends to extrude the blank 11 in the variable forming cavity 12, and the blank 11 flows to fill the current variable forming cavity 12; secondly, the male die 2 is continuously pressed downwards, the blank 11 flows upwards along the side wall of the forming channel 9, the blank 11 is hung on the female die assembly 6 through the groove 10 to slide upwards, so that the variable forming cavity 12 is prolonged, and the blank 11 is further continuously filled in the subsequently exposed variable forming cavity 12 and the grooves 10 of each layer until the forming of the blank 11 is finished;

the third step: after the forming is finished, referring to fig. 4, 5, 6, 7, 8 and 10, withdrawing the punch 2 from the variable forming cavity 12, after the punch 2 is withdrawn from the variable forming cavity 12, the push rod 7 drives the die assembly 6 and the blank 11 to move upwards, then the plane pin 21 is inserted into the elongated slot 20, then the push rod 7 drives the die assembly 6, the blank 11 and the plane pin 21 to fall down, the plane pin 21 contacts with the lower die plate 3 and slides upwards along the elongated slot 20 to support the left-flap die 13 and the right-flap die 14, the second hollow tube 28 is sleeved outside the punch 2 and is supported between the upper die plate 1 and the pre-stress ring 15, the press slide moves downwards to drive the upper die plate 1 and the second hollow tube 28 to move downwards, so that the pre-stress ring 15 is separated from the left-flap die 13 and the right-flap die 14, the second hollow tube 28 is removed, and then the left-flap die 13 and the right die 14 are separated, specifically, after the prestressed ring 15 is separated from the left-half female die 13 and the right-half female die 14, the inverted triangular bolt 18 passes through the guide groove 36 and the avoiding hole 37 and is inserted into the inverted triangular hole 19, the position of the inverted triangular bolt 18 is fixed after being inserted, then the push rod 7 moves upwards to drive the left-half female die 13, the right-half female die 14 and the blank 11 to move upwards, further the inverted triangular bolt 18 separates the left-half female die 13 and the right-half female die 14 along the parting surface 16 and supports the left-half female die 13 and the right-half female die 14, after the left-half female die 13 and the right-half female die 14 are separated, the push rod 7 continues to move upwards to eject the blank 11 above the left-half female die 13 and the right-half female die 14, the processed blank 11 is taken out, then the plane pin 21 is detached from the long groove 20, the push rod 7 moves downwards to return, the inverted triangular bolt 18 returns, the left-half female die 13 and the right-half female die 14 are spliced, and the steps are repeated when the next blank 11 is formed, and then realized having reduced the time cost that the tradition was artifical to take out the die and is carried out the die sinking and get the piece, guaranteed production line efficiency, realized automated production.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the design of the present invention, and all equivalent changes made in the design key point of the present invention fall within the protection scope of the present invention.

Claims

1. A method for extruding and forming a cylindrical part with a boss in the shape is characterized in that: the method relates to an extrusion forming die of a cylindrical part with a boss on the appearance, which comprises the following steps: terrace die (2) fixed with cope match-plate pattern (1), lower mould subassembly (4) fixed with lower bolster (3), lower mould subassembly (4) are including position circle (5), die subassembly (6), push rod (7), position circle (5) are fixed on lower bolster (3), and vertically are equipped with slide (8), die subassembly (6) are including left lamella die (13), right lamella die (14), prestressing force circle (15), left lamella die (13), right lamella die (14) amalgamation department are fractal face (16), prestressing force circle (15) slide and set up in slide (8), be formed with bell mouth (17) of adduction down in prestressing force circle (15), left lamella die (13) and right lamella die (14) outline are for the cooperation the half cone face of bell mouth (17), left side die (13) and right lamella die (14) are in bell mouth (17) along the radial activity amalgamation formation of fractal face (16) and take shape The forming channel (9) is arranged on the periphery of the push rod (7) in a sliding mode, a plurality of layers of grooves (10) are arranged on the side wall of the forming channel (9) along the axial direction, and the method specifically comprises the following steps:

the first step is as follows: preparing before forming, dropping the prestressed ring (15) into the bottom of the slideway (8), splicing and pressing a left-flap female die (13) and a right-flap female die (14) in the tapered hole (17), enabling the left-flap female die (13), the right-flap female die (14) and the tapered hole (17) to be self-locked, enabling a push rod (7) and a forming channel (9) to form a variable forming cavity (12), enabling at least one layer of groove (10) to be exposed in the variable forming cavity (12), placing a blank (11) in the variable forming cavity (12), and aligning a male die (2) to the variable forming cavity (12) from the upper part;

the second step is that: the forming process comprises two stages, namely, the male die (2) descends to extrude the blank (11) in the variable forming cavity (12), and the blank (11) flows to fill the current variable forming cavity (12); secondly, the male die (2) is continuously pressed downwards, the blank (11) flows upwards along the side wall of the forming channel (9), the blank (11) is hung on the female die component (6) through the groove (10) to slide upwards, so that the variable forming cavity (12) is prolonged, and the blank (11) is further filled with the subsequently exposed variable forming cavity (12) and the grooves (10) of each layer;

the third step: and (3) after the forming is finished, withdrawing the male die (2) from the variable forming cavity (12), separating the prestressed ring (15) from the left-segment female die (13) and the right-segment female die (14), separating the left-segment female die (13) and the right-segment female die (14), and taking out the processed blank (11).

2. A method of extrusion forming a contoured convex barrel according to claim 1, wherein: the die is characterized by further comprising an inverted triangular bolt (18), inverted triangular holes (19) are spliced on the parting surface (16) of the left-petal female die (13) and the right-petal female die (14), and the inverted triangular holes (19) are symmetrical along the parting surface (16); after the prestressed ring (15) is separated from the left-petal female die (13) and the right-petal female die (14), the inverted triangular bolt (18) is inserted into the inverted triangular hole (19), the position of the inverted triangular bolt (18) is fixed, then the push rod (7) moves upwards to drive the left-petal female die (13), the right-petal female die (14) and the blank (11) to move upwards, and then the inverted triangular bolt (18) separates the left-petal female die (13) and the right-petal female die (14).

3. A method of extrusion forming a contoured convex barrel according to claim 2, wherein: after the left-flap female die (13) and the right-flap female die (14) are separated, the push rod (7) continues to move upwards to eject the blank (11) to the upper parts of the left-flap female die (13) and the right-flap female die (14).

4. A method of extrusion forming a contoured convex barrel according to claim 1, wherein: the die assembly is characterized by further comprising a second hollow pipe (28), an elongated groove (20) transversely penetrates through the side wall of the push rod (7), the upper end of the elongated groove (20) is higher than the lower surfaces of the left-flap female die (13) and the right-flap female die (14) when the female die assembly (6) slides up to the highest height, a plane pin (21) vertically slides in the elongated groove (20) and is detachably inserted into the elongated groove, and two ends of the plane pin (21) extend out of the elongated groove (20); after the male die (2) is withdrawn from the variable forming cavity (12), the push rod (7) drives the female die assembly (6) and the blank (11) to move upwards, the plane pin (21) is inserted into the long groove (20), then the push rod (7) drives the female die assembly (6), the blank (11) and the plane pin (21) to fall down, the plane pin (21) is contacted with the lower die plate (3) and then slides upwards along the long groove (20) to support the left-flap female die (13) and the right-flap female die (14), the second hollow tube (28) is supported between the upper die plate (1) and the prestress ring (15), and the upper die plate (1) moves downwards to separate the prestress ring (15) from the left-flap female die (13) and the right-flap female die (14).

5. A method of extrusion forming a contoured convex barrel according to claim 1, wherein: still include first hollow tube (27), support first hollow tube (27) top with cope match-plate pattern (1), support left lamella die (13) and right lamella die (14) under first hollow tube (27), cope match-plate pattern (1) descends and compresses tightly left lamella die (13) and right lamella die (14) amalgamation in bell mouth (17).