Forming forging die for hub axle tube of stepped structure

Abstract

The utility model discloses a forming forging die for a hub axle tube with a stepped structure, which belongs to the technical field of axle tube forging dies and comprises a base, an overturning mounting frame is rotatably mounted at the top of the base, and a rotating screw is rotatably mounted between the centers of two sides of the inner wall of the base. According to the forming forging die for the hub axle tube of the stepped structure, the rotating screw rod, the moving seat, the top frames and the overturning mounting frame are arranged, the top frames on the two sides of the moving seat rotate between the first rotating frame and the second rotating frame which correspond to each other, and therefore one side of the overturning mounting frame is jacked up, and the overturning mounting frame is obliquely overturned at the top of the base; the first forming die, the second forming die and the third forming die on the top of the overturning mounting frame are inclined synchronously, upsetting blanks, forming blanks and reverse extrusion blanks which are formed through forging in the first forming die, the second forming die and the third forming die can be taken out conveniently, and forging machining can be conducted by replacing the machining positions of the upsetting blanks, the forming blanks and the reverse extrusion blanks.

Description

Technical Field

[0001] The utility model belongs to the technical field of axle tube forging dies, in particular to a forming forging die for a wheel hub axle tube with a stepped structure. Background Art

[0002] The automotive wheel hub is a crucial component of any vehicle. One of its primary components is the hub axle, which is primarily used in the stamped and welded axle housings of various trucks and buses, as well as the wheel supports at both ends of the drive axles of construction machinery. The hub axle is welded to each end of the axle housing, with the axle shaft passing through the middle of the hub. During vehicle operation, the hub axle not only bears the weight of the vehicle and its cargo, but also the complex and variable stresses generated by road conditions. The quality of the hub axle affects the vehicle's smoothness and safety. The forging process produces high-quality forgings with axially distributed metal streamlines, a dense metal structure, and excellent mechanical properties.

[0003] At present, domestic manufacturers usually use seamless steel pipes for local heating of this type of stepped shaft tube, and then rough extrusion molding. In actual applications, this process is difficult to form ideal metal streamlines and the inner hole is uneven. At the same time, the metal density and intrinsic quality of the deformed part are improved, while the metal structure of the non-deformed part remains in the raw material state, resulting in differences in the intrinsic quality of the same blank.

[0004] The prior art discloses an automobile hub axle tube forming die with application number CN201120188741.9. The die uses medium-frequency heating of solid bar stock, performs a primary pressing in a primary pressing die, and presses the solid bar stock into the finished product dimensions. The pressed blank is then transferred to a secondary extrusion forming die. The extrusion of the punch and the secondary extrusion forming die causes the metal structure to extend in the reverse direction, lengthening the overall length of the product. This allows the hub axle tube to form an axial full-fiber metal streamline structure and a dense metal structure, greatly improving the mechanical properties of the hub axle tube. This process can ensure the metal streamline structure and physical properties of the axle tube, but it increases the machining allowance at one end of the blank, resulting in a waste of raw materials, increased tool wear and machining time, and greatly increasing the production cost of the stepped structure axle tube.

[0005] The existing forming forging die of the stepped structure wheel hub shaft tube needs to control the top plate to lift the roughing punch, forming punch and counter-extrusion punch to a higher position when taking out the roughing blank, forming blank and counter-extrusion blank from the corresponding forming die one, forming die two and forming die three. It is not convenient to take out and replace the roughing blank, forming blank and counter-extrusion blank, so it is necessary to improve it. Utility Model Content

[0006] In order to overcome the above-mentioned defects, the utility model provides a forming forging die for a stepped structure wheel hub axle tube, which solves the problem that the existing forming forging die for a stepped structure wheel hub axle tube needs to control the top plate to lift the roughing head, forming punch and counter-extrusion punch to a higher position when taking out the roughing blank, forming blank and counter-extrusion blank from the corresponding forming die one, forming die two and forming die three, which makes it inconvenient to take out and replace the roughing blank, forming blank and counter-extrusion blank.

[0007] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a forming forging die for a stepped structure wheel hub shaft tube, comprising a base, a flip mounting frame rotatably mounted on the top of the base, a mounting seat 1, a mounting seat 2 and a mounting seat 3 fixedly mounted on the bottom of the flip mounting frame, a forming die 1, a forming die 2 and a forming die 3 fixedly mounted on the top of the flip mounting frame located on the top of the mounting seat 1, the mounting seat 2 and the mounting seat 3, respectively, a roughing blank, a forming blank and a back-extrusion blank are respectively provided inside the forming die 1, the roughing blank and the forming die 3, a roughing head, a forming punch and a back-extrusion punch are respectively provided on the top of the forming die 1, the roughing blank and the forming die 3.

[0008] As a further solution of the present invention: a top plate is fixedly installed on the top of the roughing punch, forming punch and reverse extrusion punch, side plates are symmetrically fixedly installed on the bottom of both sides of the base, and two groups of telescopic sliding rods are fixedly installed between the two sides of the bottom of the top plate and the two groups of side plates.

[0009] As a further solution of the present utility model: a rotating screw is rotatably installed between the central positions on both sides of the inner wall of the base, and one end of the rotating screw passes through the base and is fixedly installed with a bevel gear, and a rotating motor is fixedly installed on one side of the base, and a bevel gear is fixedly installed on the output end of the rotating motor, and the two sets of bevel gears mesh with each other. Limit slide bars are symmetrically fixedly installed on both sides of the rotating screw inside the base, and a moving seat is slidably installed on one side of the surface of the rotating screw and the two sets of limit slide bars, and a rotating frame 1 is symmetrically fixedly installed on both ends of one side of the moving seat, and a top frame is rotatably installed on the top of the rotating frame 1, and a rotating frame 2 is rotatably installed on the end of the top frame away from the rotating frame 1, and the rotating frame 2 is fixedly connected to the bottom of the flip mounting frame.

[0010] As a further solution of the present invention: four groups of limiting slide grooves are provided at equal angles on the inner wall of the mounting seat, an electric push rod is fixedly installed on the inner bottom of the mounting seat, a push rod seat is fixedly installed on the top of the electric push rod, and four groups of limiting protrusions are fixedly installed at equal angles on the bottom of the surface of the push rod seat, and the limiting protrusions correspond to the positions of the limiting slide grooves.

[0011] As a further solution of the present invention: the structures of the mounting seat 1, the mounting seat 2 and the mounting seat 3 are the same, and the shapes of the mounting seat 1, the mounting seat 2 and the mounting seat 3 correspond to the forming mold 1, the forming mold 2 and the forming mold 3 respectively.

[0012] As a further solution of the present invention: the upsetting pressure head corresponds to the top of the upsetting blank and has the same shape as that of the upsetting blank, and the upsetting blank has the same shape as that of the inner wall of the forming die.

[0013] As a further solution of the present invention: the surface of the top of the forming punch is symmetrically provided with air holes, an inner punch is slidably installed on the bottom of the forming punch, and the gap between the forming punch and the inner punch is the same as the shape of the top of the forming blank, and the forming blank corresponds to the inner wall of the forming mold 2.

[0014] As a further solution of the present invention: the bottom of the reverse extrusion punch corresponds to the top of the reverse extrusion blank in position and has the same shape, and the reverse extrusion blank corresponds to the inner wall of the forming die three.

[0015] Compared with the prior art, the beneficial effects of the present invention are:

[0016] 1. The forming forging die of the step-structured hub shaft tube is provided with a rotating screw, a movable seat, a top frame and a flip mounting frame, and the rotating motor is controlled to drive the bevel gear to rotate. The rotating screw is controlled to rotate synchronously through the meshing of the two sets of bevel gears, so that the movable seat slides toward one side of the base on the surface of the rotating screw and the two sets of limit slide bars, and the top frames on both sides of the movable seat rotate between the corresponding rotating frame 1 and rotating frame 2, thereby lifting one side of the flip mounting frame, so that the flip mounting frame tilts and flips on the top of the base, and the forming die 1, forming die 2 and forming die 3 on the top of the flip mounting frame are tilted synchronously, so that the rough blanks, forming blanks and back-extruded blanks formed in the forming die 1, forming die 2 and forming die 3 are taken out, and the processing positions of the rough blanks, forming blanks and back-extruded blanks are replaced for forging.

[0017] 2. The forming forging die of the stepped structure wheel hub shaft tube is provided with a mounting seat 1, an electric push rod, a push rod seat and a limiting protrusion. After the flip mounting frame is tilted at a certain angle on the top of the base, the electric push rod is controlled to extend to push the push rod seat out from the inside of the mounting seat 1, driving the limiting protrusion on the surface of the push rod seat to slide inside the limiting slide groove corresponding to the inner wall of the mounting seat 1, ensuring that the push rod seat will not deflect inside the mounting seat 1, and at the same time, the rough blank is pushed out from the inside of the forming die 1, and the mounting seat 2 and the mounting seat 3 are controlled to synchronously push the forming blank and the back-extruded blank out from the inside of the forming die 2 and the forming die 3, so as to facilitate the removal of the rough blank, the forming blank and the back-extruded blank.

[0018] 3. The forming forging die of the stepped structure hub shaft tube is provided with forming die one, forming die two, a roughing ram and a forming punch. The roughing ram is controlled to roughen the bar blank inside the forming die one to form a roughed blank of corresponding shape. The formed roughed blank is then placed inside the forming die two. The forming punch and the inner punch are controlled to extrude the roughed blank inside the forming die two to forge an ideal forming blank. There is a gap between the inner cavity of the forming punch and the outer circle of the upper part of the forming blank, which avoids the stress on the inner cavity of the forming punch during forming in the prior art. The forming blank fills the inner cavity of the forming punch, causing the forming blank and the forming die two to lock, resulting in the forming blank being difficult to demold. Finally, the forming blank is placed inside the forming die three, and the reverse extrusion punch is controlled to reversely extrude the forming blank. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of the expanded cross-sectional structure of the utility model;

[0020] Figure 2 This is a schematic cross-sectional view of the base, rotating screw and movable seat of the utility model;

[0021] Figure 3 This is a schematic cross-sectional view of the mounting base 1, the push rod base and the limiting protrusion of the utility model;

[0022] Figure 4 This is a schematic cross-sectional view of the matching structure of the roughing head, forming die 1 and roughing blank of the utility model;

[0023] Figure 5 This is a schematic diagram of the cross-sectional structure of the forming punch, inner punch, forming die 2 and forming blank of the utility model;

[0024] Figure 6 This is a schematic diagram of the cross-sectional structure of the reverse extrusion punch, the forming die 3 and the reverse extrusion blank of the utility model;

[0025] In the figure: 1. Base; 101. Rotating screw; 102. Bevel gear; 103. Rotating motor; 104. Limiting slide; 105. Moving seat; 106. Rotating frame 1; 107. Top frame; 108. Rotating frame 2; 2. Side plate; 3. Telescopic slide; 4. Top plate; 5. Roughing head; 6. Forming punch; 601. Air vent; 7. Inner punch; 8. Back-extrusion punch; 9. Flip mounting frame; 10. Mounting seat 1; 1001. Limiting slide; 1002. Electric push rod; 1003. Top rod seat; 1004. Limiting bump; 11. Mounting seat 2; 12. Mounting seat 3; 13. Forming die 1; 14. Roughing blank; 15. Forming die 2; 16. Forming blank; 17. Forming die 3; 18. Back-extrusion blank. DETAILED DESCRIPTION

[0026] The technical solution of this patent is further described in detail below in conjunction with specific implementation methods.

[0027] like Figure 1-6 As shown, the utility model provides a technical solution: a forming forging die for a stepped structure wheel hub shaft tube, comprising a base 1, a rotating screw 101 is rotatably installed between the central positions on both sides of the inner wall of the base 1, and one end of the rotating screw 101 passes through the base 1 and is fixedly installed with a bevel gear 102, a rotating motor 103 is fixedly installed on one side of the base 1, and the output end of the rotating motor 103 is fixedly installed with a bevel gear 102, by providing a rotating motor 103, the rotating motor 103 is controlled to rotate forward and reverse, and through the engagement of the two sets of bevel gears 102, the forward and reverse rotation of the rotating motor 103 is transmitted to the rotating screw 101, thereby controlling the rotating screw 101 to rotate forward and reverse, so that the moving seat 105 moves on the surface of the rotating screw 101;

[0028] The two sets of bevel gears 102 are meshed with each other. The inner part of the base 1 is symmetrically fixed on both sides of the rotating screw 101. A moving seat 105 is slidably installed on one side of the surface of the rotating screw 101 and the two sets of limiting slides 104. Due to the provision of the limiting slides 104, when the moving seat 105 slides on the surface of the two sets of limiting slides 104, it is ensured that the moving seat 105 will not tilt or deflect during the movement;

[0029] The two ends of one side of the moving seat 105 are symmetrically fixedly installed with rotating frames 106, and a top frame 107 is rotatably installed on the top of the rotating frame 106. The end of the top frame 107 away from the rotating frame 106 is rotatably installed with a rotating frame 2 108, and the rotating frame 2 108 is fixedly connected to the bottom of the flip mounting frame 9. Due to the provision of the top frame 107, when the moving seat 105 moves inside the base 1, the top frame 107 rotates between the rotating frame 106 and the rotating frame 2 108, thereby lifting one side of the flip mounting frame 9 and tilting the flip mounting frame 9 at a certain angle on the top of the base 1.

[0030] A flip mounting frame 9 is rotatably installed on the top of the base 1, and a mounting seat 10, a mounting seat 2 11 and a mounting seat 3 12 are fixedly installed on the bottom of the flip mounting frame 9. The structures of the mounting seat 10, the mounting seat 2 11 and the mounting seat 3 12 are the same, and the shapes of the mounting seat 10, the mounting seat 2 11 and the mounting seat 3 12 correspond to the forming mold 1 13, the forming mold 2 15 and the forming mold 3 17 respectively. Four groups of limiting slides 1001 are provided at equal angles on the inner wall of the mounting seat 10, an electric push rod 1002 is fixedly installed at the bottom of the mounting seat 10, and a push rod seat 1003 is fixedly installed on the top of the electric push rod 1002. By providing the electric push rod 1002, the electric push rod 1002 is controlled to extend and retract to make the push rod seat 1003 move up and down inside the mounting seat 10, thereby ejecting the roughened blank 14 inside the forming die 13 at the top of the mounting seat 10, and at the same time, the inside of the mounting seat 2 11 and the mounting seat 3 12 are synchronously extended and retracted to eject the forming blank 16 and the back-extruded blank 18 inside the forming die 2 15 and the forming die 3 17;

[0031] Four sets of limiting protrusions 1004 are fixedly installed at equal angles on the bottom of the surface of the push rod seat 1003, and the limiting protrusions 1004 correspond to the positions of the limiting slides 1001. Due to the presence of the limiting protrusions 1004, when the push rod seat 1003 moves up and down inside the mounting seat 10, the limiting protrusions 1004 slide inside the corresponding limiting slides 1001, ensuring that the push rod seat 1003 does not rotate when moving inside the mounting seat 10.

[0032] The top of the flip mounting frame 9 is located on the top of the mounting seat 10, the mounting seat 2 11 and the mounting seat 3 12, and the forming die 13, the forming die 2 15 and the forming die 3 17 are fixedly installed respectively. The forming die 13, the forming die 2 15 and the forming die 3 17 are respectively provided with the roughing blank 14, the forming blank 16 and the back-extrusion blank 18. The top of the forming die 13, the roughing blank 14 and the forming die 3 17 are respectively provided with the roughing ram 5, the forming punch 6 and the back-extrusion punch 8. The top of the roughing ram 5, the forming punch 6 and the back-extrusion punch 8 is fixedly installed with the top plate 4. By providing the top plate 4, the top plate 4 is connected to the forging device. When the forging device is controlled to drive the top plate 4 up and down, the roughing ram 5, the forming punch 6 and the back-extrusion punch 8 can move synchronously.

[0033] The side panels 2 are symmetrically fixedly installed on the bottom of both sides of the base 1, and two groups of telescopic slide rods 3 are fixedly installed on both sides of the bottom of the top plate 4 and between the two groups of side panels 2. Because of the telescopic slide rods 3, when the top plate 4 is controlled to move up and down on the top of the flip mounting frame 9, it is ensured that the position between the top plate 4 and the base 1 will not be offset, so that the roughing punch 5, forming punch 6 and back-extrusion punch 8 can correspond to the positions of forming die 1 13, forming die 2 15 and forming die 3 17 without offset.

[0034] The upsetting ram 5 corresponds to the top position of the upsetting blank 14 and has the same shape as that of the inner wall of the forming die 13. By providing the upsetting ram 5, the heated bar is placed into the forming die 13, and the upsetting ram 5 is controlled to press the bar into the forming die 13, thereby forging the heated bar into the upsetting blank 14.

[0035] The surface of the top of the forming punch 6 is symmetrically provided with air holes 601, and an inner punch 7 is slidably installed on the bottom of the forming punch 6, and the gap between the forming punch 6 and the inner punch 7 is the same as the shape of the top of the forming blank 16. The forming blank 16 corresponds to the inner wall of the forming die 2 15. Because the forming punch 6 and the inner punch 7 are provided, after the rough blank 14 is placed into the inside of the forming die 2 15, the forming punch 6 and the inner punch 7 are controlled to be pressed into the inside of the forming die 2 15, thereby forging the rough blank 14 into the forming blank 16.

[0036] The bottom of the back-extrusion punch 8 corresponds to the top position of the back-extrusion blank 18 and has the same shape. The back-extrusion blank 18 corresponds to the inner wall of the forming die three 17. Because the back-extrusion punch 8 is provided, the forming blank 16 is placed inside the forming die three 17, and the back-extrusion punch 8 is controlled to be pressed into the forming die three 17, so that the forming blank 16 is forged into the back-extrusion blank 18.

[0037] The working principle of this utility model is:

[0038] After the base 1 is installed in the forging device, the top plate 4 is fixedly connected to the forging working position of the forging device, the top plate 4 is controlled to move upward to drive the roughing punch 5, the forming punch 6 and the reverse extrusion punch 8 to move upward away from the flip mounting frame 9, and the rotating motor 103 is controlled to rotate to rotate the rotating screw 101 synchronously, so that the movable seat 105 moves inside the base 1 toward the rotating motor 103, and the top frame 107 rotates between the rotating frame 106 and the rotating frame 2 108 to lift one side of the flip mounting frame 9 until the flip mounting frame 9 is tilted at a certain angle on the top of the base 1, and the heated The bar stock, the roughing blank 14 and the forming blank 16 are placed in the forming die 13, the forming die 2 15 and the forming die 3 17 respectively, and the rotating motor 103 is controlled to flip, so that the top frame 107 pulls the flip mounting frame 9 to rotate on the top of the base 1 until the flip mounting frame 9 is close to the top of the base 1, and the forging working position of the forging device is controlled to be pressed down, driving the top plate 4 to move down, so that the roughing punch 5, the forming punch 6 and the counter-extrusion punch 8 are pressed into the corresponding forming die 13, the forming die 2 15 and the forming die 3 17, and the heated bar stock, the roughing blank 14 and the forming blank 16 are forged.

[0039] After the forging is completed, the forging working position of the forging device is controlled to move upward, driving the top plate 4 to move upward, so that the roughing punch 5, the forming punch 6 and the counter-extrusion punch 8 are pulled out from the corresponding forming die 13, the forming die 2 15 and the forming die 3 17, and the rotating motor 103 is controlled to rotate to drive the rotating screw 101 to rotate, and the top frame 107 is controlled to lift one side of the flip mounting frame 9, so that the top of the forming die 13, the forming die 2 15 and the forming die 3 17 are away from the roughing punch 5, The bottom of the forming punch 6 and the back-extrusion punch 8 controls the electric push rod 1002 to extend, and the rough blank 14 forged and formed inside the forming die 13 is ejected from the forming die 13. At the same time, the forming blank 16 and the back-extrusion blank 18 inside the forming die 2 15 and the forming die 3 17 are controlled to be ejected, and the ejected rough blank 14, forming blank 16 and back-extrusion blank 18 are replaced in position. The steps are repeated until the bar is forged into the back-extrusion blank 18 and taken out from the forming die 3 17.

[0040] In the description of this utility model, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections, electrical connections; direct connections, indirect connections through an intermediate medium, and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in this utility model based on specific circumstances.

[0041] The above describes in detail the preferred embodiments of this patent, but this patent is not limited to the above embodiments. Various changes can be made within the scope of knowledge possessed by ordinary technicians in this field without departing from the purpose of this patent.

Claims

1. A forming forging die for a stepped hub shaft tube, comprising a base (1), characterized in that: A flip mounting frame (9) is rotatably mounted on the top of the base (1), and a mounting seat 1 (10), a mounting seat 2 (11) and a mounting seat 3 (12) are fixedly mounted on the bottom of the flip mounting frame (9). A forming die 1 (13), a forming die 2 (15) and a forming die 3 (17) are fixedly mounted on the top of the flip mounting frame (9) located on the top of the mounting seat 1 (10), the mounting seat 2 (11) and the mounting seat 3 (12). A roughing blank (14), a forming blank (16) and a reverse extrusion blank (18) are respectively arranged inside the forming die 1 (13), the forming blank (14) and the forming die 3 (17). A roughing press head (5), a forming punch (6) and a reverse extrusion punch (8) are respectively correspondingly arranged on the top of the forming die 1 (13), the roughing blank (14) and the forming die 3 (17).

2. The forming forging die for a stepped hub axle tube according to claim 1, characterized in that: A top plate (4) is fixedly mounted on the top of the roughing punch (5), the forming punch (6) and the reverse extrusion punch (8); side plates (2) are symmetrically fixedly mounted on the bottom of both sides of the base (1); and two groups of telescopic slide rods (3) are fixedly mounted between the two sides of the bottom of the top plate (4) and the two groups of side plates (2).

3. The forming forging die for a stepped hub axle tube according to claim 1, characterized in that: A rotating screw (101) is rotatably mounted between the central positions on both sides of the inner wall of the base (1), and one end of the rotating screw (101) passes through the base (1) and is fixedly mounted with a bevel gear (102). A rotating motor (103) is fixedly mounted on one side of the base (1), and a bevel gear (102) is fixedly mounted on the output end of the rotating motor (103). The two sets of bevel gears (102) are meshed with each other. A limiting slide bar ( 104), a moving seat (105) is slidably installed on one side of the surface of the rotating screw (101) and the two sets of limiting slide bars (104), and a rotating frame (106) is symmetrically fixedly installed at both ends of one side of the moving seat (105), and a top frame (107) is rotatably installed on the top of the rotating frame (106), and a rotating frame (108) is rotatably installed on the end of the top frame (107) away from the rotating frame (106), and the rotating frame (108) is fixedly connected to the bottom of the flip mounting frame (9).

4. The forming forging die for a stepped hub axle tube according to claim 1, characterized in that: Four groups of limiting slide grooves (1001) are provided at equal angles on the inner wall of the mounting seat (10), an electric push rod (1002) is fixedly installed on the bottom of the inner wall of the mounting seat (10), a push rod seat (1003) is fixedly installed on the top of the electric push rod (1002), and four groups of limiting protrusions (1004) are fixedly installed at equal angles on the bottom of the surface of the push rod seat (1003), and the positions of the limiting protrusions (1004) correspond to those of the limiting slide grooves (1001).

5. The forming forging die for a stepped hub axle tube according to claim 1, characterized in that: The structures of the mounting seat 1 (10), the mounting seat 2 (11) and the mounting seat 3 (12) are the same, and the shapes of the mounting seat 1 (10), the mounting seat 2 (11) and the mounting seat 3 (12) respectively correspond to the forming mold 1 (13), the forming mold 2 (15) and the forming mold 3 (17).

6. The forming forging die for a stepped hub axle tube according to claim 1, characterized in that: The roughing head (5) corresponds to the top position of the roughing blank (14) and has the same shape as the roughing blank (14), and the roughing blank (14) has the same shape as the inner wall of the forming die (13).

7. The forming forging die for a stepped hub axle tube according to claim 1, characterized in that: The surface of the top of the forming punch (6) is symmetrically provided with air holes (601), and an inner punch (7) is slidably installed on the bottom of the forming punch (6), and the gap between the forming punch (6) and the inner punch (7) is the same as the shape of the top of the forming blank (16), and the forming blank (16) corresponds to the inner wall of the second forming die (15).

8. The forming forging die for a stepped hub axle tube according to claim 1, characterized in that: The bottom of the reverse extrusion punch (8) corresponds to the top of the reverse extrusion blank (18) and has the same shape, and the reverse extrusion blank (18) corresponds to the inner wall of the forming die three (17).

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