CN217070372U

CN217070372U - Hub punching and deburring device

Info

Publication number: CN217070372U
Application number: CN202123407329.4U
Authority: CN
Inventors: 章可泽
Original assignee: Ningbo Runcheng Intelligent Technology Co ltd
Current assignee: Ningbo Runcheng Intelligent Technology Co ltd
Priority date: 2021-12-30
Filing date: 2021-12-30
Publication date: 2022-07-29
Anticipated expiration: 2031-12-30

Abstract

The utility model relates to the technical field of stamping dies, and discloses a hub punching and deburring device, which comprises a lower die for placing a workpiece to be machined, an upper die arranged above the lower die in a reciprocating lifting way, and a punch head which is arranged on the upper die and used for punching the workpiece to be machined when descending or separating from the workpiece to be machined when ascending, wherein a deburring structure for leveling and smoothing the hole is arranged on the punch head, the deburring structure comprises an annular accommodating groove which is concavely arranged on the outer annular wall of one side of the punch head close to the workpiece to be machined and an annular rolling ring which is rotationally arranged in the annular accommodating groove, the cross section of the annular rolling ring is circularly arranged, the outer diameter of the annular rolling ring is larger than or equal to the diameter of the punch head, the rotation of the annular rolling ring is controlled by the friction force between the annular rolling ring and the hole side wall when the punch head is lifted, the punching and deburring device reduces the resistance between the deburring device and the burr by replacing sliding and extruding through the rolling and extruding, reduce the damage to burring device, increase of service life.

Description

Hub punching and deburring device

Technical Field

The utility model relates to a stamping die technical field specifically is a wheel hub burring device that punches a hole.

Background

Generally, burrs are formed on the edge or the side wall of the hole after punching, and therefore, a deburring process is required after punching, the operation is complicated, and a burr-free punching die is formed.

Chinese patent with application number CN201721187023.3 discloses a burr-free punching die, which comprises a punching device and a deburring device, wherein the punching device punches a punched product, the deburring device comprises a punch and an arc part, and the deburring device further comprises a cutting part.

This no burr cut-out press is when the burr is too long, and the cutting part cuts off the burr of overlength, and rethread circular arc portion flattens, makes the burr that depends on at the hole lateral wall reduce as far as possible, but circular arc portion and burr are through the flattening of the extrusion cooperation realization to the burr that slides, and the resistance between burr and the circular arc portion is great, and consequently the damage to circular arc portion is great, leads to the life-span of drift shorter.

SUMMERY OF THE UTILITY MODEL

An object of the utility model is to provide a wheel hub burring device that punches a hole replaces the extrusion of sliding through the roll extrusion to reduce the resistance between burring device and the burr, reduces the damage to burring device, increase of service life.

In order to achieve the above object, the utility model provides a following technical scheme: the utility model provides a wheel hub burring device that punches a hole, including placing the lower mould of treating the machined part, treat the upper die that the reciprocating lift set up in lower mould top and treat the machined part when descending that sets up on last mould and punch a hole or break away from the drift of treating the machined part when ascending, be provided with on the drift and make the hole level and smooth burring structure, burring structure includes the annular storage tank of setting up and the annular rolling circle of rotation setting in the annular storage tank of the outer rampart upper concave near treating machined part one side of drift, the cross section of annular rolling circle is circular setting, and the external diameter of annular rolling circle is greater than or equal to the diameter of drift, the rotation of annular rolling circle is controlled by the frictional force of annular rolling circle and hole lateral wall when the drift goes up and down.

By adopting the scheme, compared with the prior art that the flattening of the burrs is realized by the sliding extrusion fit of the arc part and the burrs, the resistance between the burrs and the arc part is larger, so that the damage to the arc part is larger, the service life of the punch is shorter, the deburring structure is arranged in the scheme, when the punch descends along with an upper die to punch a hole on a workpiece to be processed, because the annular rolling ring is in rotating fit with the annular accommodating groove, because the outer diameter of the annular rolling ring is larger than or equal to the diameter of the punch, the friction force generated by the butt joint of the outer surface of the annular rolling ring and the side wall or the edge of the hole drives the annular rolling ring to rotate, the annular rolling ring is in rolling extrusion fit with the side wall or the edge of the hole to flatten the burrs on the side wall or the edge of the hole, the conventional sliding extrusion is changed into rolling extrusion by the annular rolling ring, the flattening of the burrs is ensured, and the resistance between the annular rolling ring and the burrs is reduced, the damage to the annular rolling ring is reduced, the service life of the annular rolling ring is prolonged, and meanwhile, the resistance is reduced, so that the punch is easier to lift in the hole, the damage to the punch is reduced, and the service life of the punch is prolonged.

Further, the annular accommodating groove is arc-shaped and is matched with the annular rolling ring.

By adopting the scheme, the annular accommodating groove and the annular rolling ring are matched, so that the annular rolling ring is prevented from shaking or moving relative to the punch except for rotation, the extrusion force of the annular rolling ring on burrs is ensured, and the stability of the punch and the annular rolling ring during operation is ensured.

Further, the annular groove, the annular rolling ring and the punch are concentrically arranged.

By adopting the scheme, the consistency of the extrusion pressure degree of the annular rolling ring on the side wall of the hole is ensured by concentric arrangement, the smoothness of the hole is ensured, and the stability of the punch and the annular rolling ring during operation is further improved.

Furthermore, one side of the punch close to the workpiece to be machined is recessed upwards to form an annular impact part.

By adopting the scheme, the contact surface of the annular impact part and the workpiece to be machined is changed from a plane to an annular contact surface, so that the contact area of the annular impact part and the workpiece to be machined is greatly reduced, namely, the stress area of the workpiece to be machined is reduced, under the same external force application, the pressure from the annular impact part on the workpiece to be machined reaches the strength required by punching by reducing the stress area, the requirement on equipment is reduced, the loss on the equipment and the consumption on energy are reduced, the production cost is reduced, and meanwhile, the generation of burrs on the side wall of the hole can be reduced due to the reduction of the stress area.

Further, the side of the annular impact portion away from the punch is provided in the shape of a blade with the tip facing outward.

By adopting the scheme, the contact area between the annular impact part and the workpiece to be machined is reduced to the minimum value in the blade shape, the pressure intensity is maximum at the moment, the punching efficiency is greatly improved, meanwhile, the blade shape can also cut off overlong burrs, the burrs are flattened through the annular rolling ring, and the deburring efficiency is improved.

Furthermore, be provided with the demoulding structure who is convenient for the drift to deviate from treating the machined part after punching a hole on the mould, demoulding structure includes the material returned mould that can follow the drift axial and remove for the drift that sets up in last mould below, the elastic construction that the direction limit structure that drives material returned mould rectilinear motion and restriction material returned mould and break away from last mould that sets up between material returned mould and the last mould and control material returned mould and remove that sets up between last mould and material returned mould, the distance that the distance between the bottom surface under the material returned mould and treating the machined part was less than the annular impact portion bottom surface and treating between the machined part when material returned mould and treating the machined part contactless.

By adopting the scheme, the material returning die is firstly abutted with the workpiece to be machined in the process that the upper die moves downwards to be close to the workpiece to be machined, the distance between the upper die and the material returning die is gradually reduced in the process that the upper die continues to move downwards, the material returning die is pre-pressed on the workpiece to be machined under the action of the elastic structure, the workpiece to be machined is prevented from moving, and meanwhile, the punch head is contacted with the workpiece to be machined along with the descending of the upper die to punch; after punching, the upper die is upwards far away from the workpiece to be machined, the punch moves upwards along with the punch, the material returning die is still pressed on the workpiece to be machined due to the existence of the elastic structure, the punch can be guaranteed to be smoothly separated from the workpiece to be machined due to relative displacement generated between the punch and the material returning die, the upper die continues to rise until the elastic structure is restored to the initial state, the material returning die can be driven to be separated from the workpiece to be machined, the guide limiting structure drives the material returning die to move linearly relative to the punch when the displacement is generated, the material returning die can be limited to be separated from the upper die, and the stability and the accuracy in operation are guaranteed.

Furthermore, the elastic structure comprises a spring, and two ends of the spring are respectively abutted or fixedly connected with the material returning die and the upper die.

By adopting the scheme, the distance between the upper die and the material returning die is gradually reduced, and the spring is extruded to generate elasticity to drive the material returning die to press the workpiece to be processed, so that the workpiece to be processed is prevented from moving; after the punching is finished, when the upper die moves upwards to enable the punch head to be separated from the workpiece to be machined, the spring is still in a compressed state, and the material returning die is still pressed on the workpiece to be machined, so that relative displacement is generated between the punch head and the material returning die, and the punch head is enabled to be smoothly separated from the workpiece to be machined.

Furthermore, the guiding and limiting structure comprises a guide sleeve which is arranged on the upper die downwards and used for the material returning die to move linearly along the axial direction of the punch, an annular limiting block which is arranged on the inner annular wall of one side, away from the upper die, of the guide sleeve in an inward protruding mode, and an annular abutting block which is arranged between the upper die and the annular limiting block and is arranged on the outer annular wall of the material returning die in an outward protruding mode, wherein the outer diameter of the annular abutting block is larger than the inner diameter of the annular limiting block.

Adopt above-mentioned scheme, because elastic construction can't guarantee that the material returned mould is sharp along the axial removal of drift, can take place to rock, stability and accuracy when the influence punches a hole, and the material returned mould also can't guarantee with treating machined part butt position, consequently through setting up the guide pin bushing, the material returned mould is reducible or avoid rocking of material returned mould along drift axial displacement in the guide pin bushing, increase stability, through the setting of annular stopper and annular butt piece, the restriction material returned mould breaks away from the guide pin bushing, the material returned mould is located the mould all the time promptly.

Furthermore, the outer ring wall of the annular abutting block is attached to or in clearance fit with the inner ring wall of the guide sleeve, and the inner ring wall of the annular limiting block is attached to or in clearance fit with the outer ring wall of the material returning mold.

By adopting the scheme, because the guide sleeve is fixedly arranged, the material returning die is attached to the guide sleeve or is in clearance fit with the guide sleeve to further limit the shaking of the material returning die, so that the material returning die can move more stably along the axial direction of the punch and can be guaranteed to move linearly.

Further, the guide sleeve, the material returning die, the annular limiting block and the annular abutting block are concentrically arranged with the punch, and a through groove for the punch to penetrate through is formed in the material returning die.

By adopting the scheme, the concentric arrangement ensures the balanced stress on the workpiece to be processed, and is more favorable for the punch head to be separated from the workpiece to be processed without causing the deformation of the hole.

Compared with the prior art, the utility model discloses the beneficial effect who reaches is:

1. through setting up the annular rolling circle, it punches a hole to treat the machined part along with last mould decline when the drift, because be normal running fit between annular rolling circle and the annular storage tank, the annular rolling circle is because the external diameter is greater than or equal to the diameter of drift, frictional force that its surface and the lateral wall or the marginal butt of hole produced orders about the annular rolling circle and rotates, consequently, the annular rolling circle rolls extrusion fit with the lateral wall or the marginal roll in hole, flatten the burr on hole lateral wall or the edge, the annular rolling circle changes traditional extrusion of sliding into more roll extrusion, when guaranteeing to flatten the burr, reduce the resistance between annular rolling circle and the burr, reduce the damage to the annular rolling circle, prolong its life, simultaneously because reduced the resistance makes the drift lift more easily in the hole, reduce the damage to the drift, prolong the life of drift.

2. The contact surface of annular impact portion and treating the machined part becomes annular contact surface from a plane, the area of contact between them has been reduced greatly, reduce the lifting surface area of treating the machined part promptly, under the same external force is exerted, make the pressure that comes from annular impact portion on treating the machined part reach the required intensity that punches a hole through reducing lifting surface area, reduce the requirement to equipment, reduce the loss to equipment and the consumption to the energy, reduction in production cost, meanwhile, the reduction of lifting surface area still can reduce the production of hole lateral wall burr, through above-mentioned 2 advantages, reduce the resistance between burring device and the burr, reduce the damage to burring device, increase of service life.

Drawings

The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention, and together with the description serve to explain the invention and not to limit the invention. In the drawings:

FIG. 1 is a schematic half-sectional view of a hub punching and deburring device in an embodiment;

fig. 2 is an enlarged view at a in fig. 1.

In the figure: 1. a workpiece to be processed; 2. a lower die; 3. an upper die; 4. a punch; 5. an annular accommodating groove; 6. an annular rolling ring; 7. a groove; 8. an annular impact portion; 9. returning the material mould; 10. a spring; 11. a guide sleeve; 12. an annular stop block; 13. an annular abutment block; 14. a through groove.

Detailed Description

The technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

Examples

A hub punching and deburring device comprises a lower die 2 for placing a workpiece 1 to be machined, the workpiece 1 to be machined in the embodiment is a hub, the contact surface of the lower die 2 and the hub is adaptive and fitted to ensure the strength and uniformity of the hub under the supporting force of the lower die 2, so as to avoid the deformation of the hub during punching, an upper die 3 is arranged above the lower die 2 in a reciprocating lifting manner and can be continuously close to or away from the hub, a punch 4 is arranged on the upper die 3, the punch 4 descends along with the upper die 3 when the upper die 3 descends to punch the hub, the punch 4 ascends along with the upper die 3 to separate from the hub, a deburring structure is arranged on the punch 4, burrs in a hole punching process and hole separating process of the punch 4 from the hole are cut and flattened to ensure the flatness and smoothness of the hole, the deburring structure comprises an annular accommodating groove 5 concavely arranged on the outer ring wall of one side, close to the hub, of the punch 4, an annular rolling ring 6 is rotationally arranged in the annular accommodating groove 5, the cross section of the annular rolling ring 6 is in a circular arrangement, the outer diameter of the annular rolling ring 6 is larger than or equal to the diameter of the punch 4, the rotation of the annular rolling ring 6 is controlled by the friction force between the annular rolling ring 6 and the side wall of the hole when the punch 4 is lifted, when the punch 4 descends along with the upper die 3 to punch the hole on the hub, because the annular rolling ring 6 is in rotating fit with the annular accommodating groove 5, because the outer diameter of the annular rolling ring 6 is larger than or equal to the diameter of the punch 4, the friction force generated by the abutting of the outer surface of the annular rolling ring 6 and the side wall or the edge of the hole drives the annular rolling ring 6 to rotate, therefore, the annular rolling ring 6 is in rolling and extruding fit with the side wall or the edge of the hole to flatten burrs on the side wall or the edge of the hole, the annular rolling ring 6 changes the traditional sliding and extruding into rolling extrusion, and ensures that the burrs are flattened, reduce the resistance between annular rolling circle 6 and the burr, reduce the damage to annular rolling circle 6, prolong its life, simultaneously because reduced the resistance and made drift 4 go up and down in the hole more easily, reduce the damage to drift 4, prolong the life of drift 4, annular storage tank 5 sets up to circular-arc and with annular rolling circle 6 adaptation, avoid annular rolling circle 6 to carry out rocking or moving except that rotating for drift 4, thereby guarantee the extrusion dynamics of annular rolling circle 6 to the burr, and guarantee the stationarity when drift 4 and annular rolling circle 6 move, annular groove 7, annular rolling circle 6 and drift 4 are concentric to be set up, guarantee the uniformity of annular rolling circle 6 to the extrusion dynamics of hole lateral wall, guarantee the level and smooth in hole, and concentric still can further promote the stationarity when drift 4 and annular rolling circle 6 move.

One side of the punch 4 close to the hub is recessed upwards to form an annular impact part 8, the contact surface of the annular impact part 8 and the hub is changed from a plane to an annular contact surface, the contact area of the annular impact part 8 and the hub is greatly reduced, namely, the stress area of the hub is reduced, under the same external force, the stress area is reduced, so that the pressure intensity from the annular impact part 8 on the hub reaches the strength required by punching, the requirement on equipment is reduced, the loss of the equipment and the consumption of energy are reduced, the production cost is reduced, meanwhile, the reduction of the stress area can also reduce the generation of burrs on the side wall of the hole, one side of the annular impact part 8, far away from the punch 4, is arranged to be in a blade shape, the contact area between the annular impact part 8 and the hub is reduced to the minimum value by the blade shape, the pressure intensity is maximum at the moment, the punching efficiency is greatly improved, and meanwhile, the excessively long blade shape can also cut off the burrs, and then the annular rolling ring 6 is used for flattening, so that the deburring efficiency is improved.

In order to avoid that the punch 4 is clamped on the hub after punching and deburring are finished to cause demoulding failure, a demoulding structure is arranged on the upper die 3, the punch 4 is convenient to be separated from the hub, the demoulding structure comprises a material returning die 9 arranged below the upper die 3, the material returning die 9 can move relative to the punch 4 along the axial direction of the punch 4, an elastic structure is arranged between the upper die 3 and the material returning die 9 to control the material returning die 9 to move, the elastic structure is a spring 10, when the material returning die 9 is not in contact with the hub, the distance between the lower bottom surface of the material returning die 9 and the hub is smaller than the distance between the lower bottom surface of the annular impact part 8 and the hub, so that the material returning die 9 is firstly abutted against the hub and is finally separated from the hub, and because the spring 10 cannot ensure that the material returning die 9 moves linearly along the axial direction of the punch 4, shaking can occur to influence the stability and the accuracy in operation, a guiding limit structure is arranged between the material returning die 9 and the upper die 3, the material returning die 9 is driven to move linearly, the material returning die 9 is limited to be separated from the upper die 3, the guiding and limiting structure comprises a guide sleeve 11 which is arranged on the upper die 3 downwards, the guide sleeve 11 is used for enabling the material returning die 9 to move linearly along the axial direction of the punch 4, the shaking of the material returning die 9 is reduced or avoided, the stability is improved, the accuracy is improved, an annular limiting block 12 is arranged on the inner annular wall, away from the upper die 3, of the guide sleeve 11 in an inward protruding mode, an annular abutting block 13 is arranged between the upper die 3 and the annular limiting block 12 in an outward protruding mode on the outer annular wall of the material returning die 9, the outer diameter of the annular abutting block 13 is larger than the inner diameter of the annular limiting block 12, the material returning die 9 is limited to be separated from the guide sleeve 11, namely the material returning die 9 is always located on the upper die 3, the outer annular abutting block 13 is in fit or clearance fit with the inner annular wall of the guide sleeve 11, the inner annular limiting block 12 is in fit or clearance fit with the outer annular wall of the material returning die 9, in the embodiment, the fitting arrangement is adopted, have restricted material returned mould 9's rocking completely, make material returned mould 9 along 4 axial removal of drift more steady and guarantee to be rectilinear movement, and in order to guarantee material returned mould 9's smooth removal, add between guide pin bushing 11 and the material returned mould 9 and have lubricating oil, guide pin bushing 11, material returned mould 9, annular stopper 12 and annular butt piece 13 set up with drift 4 is concentric, set up the logical groove 14 that supplies drift 4 to pass on the material returned mould 9, it is balanced to concentric the atress that sets up on the assurance wheel hub, more be favorable to drift 4 to break away from wheel hub and do not make the deformation of pore-forming, and because the limiting displacement of annular butt piece 13 and annular stopper 12, the both ends of spring 10 respectively with material returned mould 9 and last mould 3 butt or fixed connection, adopt fixed connection in this embodiment, guarantee intensity.

In the process that the upper die 3 moves downwards to be close to the hub, the material returning die 9 is firstly abutted with the hub, in the process that the upper die 3 continues to move downwards, the distance between the upper die 3 and the material returning die 9 is gradually reduced, the spring 10 is extruded to generate elastic force to drive the material returning die 9 to press the hub, the hub is prevented from moving, meanwhile, after the punch 4 descends along with the upper die 3 and moves relative to the material returning die 9, the annular impact part 8 is contacted with the hub to punch holes, the punch 4 continues to descend after punching, the blade-shaped end part of the annular impact part 8 is contacted with a longer burr to cut, the outer surface of the annular rolling ring 6 is abutted with the side wall or edge of the hole to generate friction force to drive the annular rolling ring 6 to rotate and is in rolling extrusion fit with the side wall or edge of the hole, and burrs on the side wall or edge of the hole are flattened; after punching a hole, go up mould 3 and upwards keep away from wheel hub, drift 4 goes upward along with it, because spring 10 still is in compression state, still press material returned mould 9 on wheel hub, consequently produce relative displacement between drift 4 and the material returned mould 9, guarantee drift 4 and break away from smoothly from wheel hub, break away from in-process annular rolling circle 6 and roll the extrusion with the hole once more, further order about the edge or the lateral wall in hole and level and smooth, go up mould 3 and continue to rise until annular butt piece 13 and annular stopper 12 butt, can drive material returned mould 9 and break away from wheel hub.

Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that modifications may be made to the embodiments described in the foregoing embodiments, or equivalents may be substituted for elements thereof. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. The utility model provides a wheel hub burring device that punches a hole, including place lower mould (2) of treating machined part (1), last mould (3) that sets up in the reciprocal lift of lower mould (2) top and treat machined part (1) when going up the decline that sets up on mould (3) and punch a hole or break away from drift (4) of treating machined part (1) when rising, its characterized in that: the deburring structure for flattening and smoothing the hole is arranged on the punch (4), the deburring structure comprises an annular containing groove (5) which is concavely arranged on the outer annular wall of one side, close to the workpiece to be machined (1), of the punch (4) and an annular rolling ring (6) which is rotatably arranged in the annular containing groove (5), the cross section of the annular rolling ring (6) is circularly arranged, the outer diameter of the annular rolling ring (6) is larger than or equal to the diameter of the punch (4), and the rotation of the annular rolling ring (6) is controlled by the friction force between the annular rolling ring (6) and the side wall of the hole when the punch (4) is lifted.

2. A hub punching and deburring device according to claim 1, characterized in that: the annular accommodating groove (5) is arc-shaped and is matched with the annular rolling ring (6).

3. A hub punching and deburring device according to claim 1, characterized in that: the annular groove (7), the annular rolling ring (6) and the punch (4) are arranged concentrically.

4. The hub punching and deburring device of claim 1, wherein: one side of the punch (4) close to the workpiece (1) to be machined is recessed upwards to form a groove (7) and then forms an annular impact part (8).

5. A hub punching and deburring device according to claim 4, characterized in that: the side of the annular impact part (8) far away from the punch (4) is provided with an edge with the tip outwards.

6. A hub punching and deburring device according to claim 1, characterized in that: the upper die (3) is provided with a demoulding structure which is convenient for the punch (4) to be separated from the workpiece to be machined (1) after punching is completed, the demoulding structure comprises a material returning die (9) which is arranged below the upper die (3) and can move relative to the punch (4) along the axial direction of the punch (4), a guide limiting structure which is arranged between the material returning die (9) and the upper die (3) and drives the material returning die (9) to move linearly and limits the material returning die (9) to be separated from the upper die (3), and an elastic structure which is arranged between the upper die (3) and the material returning die (9) and controls the material returning die (9) to move, and the distance between the lower bottom surface of the material returning die (9) and the workpiece to be machined (1) when the material returning die (9) is not in contact with the workpiece to be machined (1) is smaller than the distance between the lower bottom surface of the annular impact part (8) and the workpiece to be machined (1).

7. A hub punching and deburring device according to claim 6, characterized in that: the elastic structure comprises a spring (10) with two ends respectively connected with the material returning die (9) and the upper die (3) in an abutting or fixed mode.

8. A hub punching and deburring device according to claim 6, characterized in that: the guide limiting structure comprises a guide sleeve (11) which is arranged on an upper die (3) downwards and used for a material returning die (9) to move linearly along the axial direction of a punch (4), an annular limiting block (12) which is arranged on an inner annular wall of one side of the upper die (3) and far away from the guide sleeve (11), and an annular abutting block (13) which is arranged between the upper die (3) and the annular limiting block (12) and is arranged on an outer annular wall of the material returning die (9) in an outwards protruding mode, wherein the outer diameter of the annular abutting block (13) is larger than the inner diameter of the annular limiting block (12).

9. The hub punching and deburring device of claim 8, wherein: the outer ring wall of the annular abutting block (13) is attached to or in clearance fit with the inner ring wall of the guide sleeve (11), and the inner ring wall of the annular limiting block (12) is attached to or in clearance fit with the outer ring wall of the material returning mold (9).

10. A hub punch deburring apparatus as claimed in claim 9 wherein: the guide sleeve (11), the material returning die (9), the annular limiting block (12) and the annular abutting block (13) are arranged concentrically with the punch (4), and a through groove (14) for the punch (4) to penetrate is formed in the material returning die (9).