EXTRUSION PRESS, IN PARTICULAR A SHORT STROKE EXTRUSION PRESS, FOR PRODUCING METAL EXTRUDATES BY EXTRUDING A BILLET

Abstract

An extrusion press for producing metal extrudates by extruding a billet, the extrusion press comprising: a punch holder crosspiece which carries a punch and is adapted to be translated in two opposite senses of translation along a first extrusion direction; a billet holder loader adapted to be alternately positioned between a resting position and a loading position; wherein said punch holder crosspiece is translatable along a second direction, perpendicular to said first extrusion direction, between a first position thereof and a second position thereof; wherein when the billet holder loader is in said resting position and said punch holder crosspiece is in the first position thereof, the translation of the punch holder crosspiece along said first extrusion direction in a first sense of translation, or sense of extrusion, causes a push by said punch against said billet and the extrusion of said billet; characterized in that said extrusion press comprises restraining means adapted to mutually restrain said punch holder crosspiece and said billet holder loader; and in that when the punch holder crosspiece is in the first position, it is restrained to the billet holder loader by means of said restraining means so that the translation of said punch holder crosspiece from the first position to the second position causes the movement of the billet holder loader from said resting position to said loading position.

Claims

1. An extrusion press for producing metal extrudates by extruding a billet, the extrusion press comprising: a punch holder crosspiece which carries a punch and is adapted to be translated in two opposite senses of translation along a first extrusion direction; a billet holder loader adapted to be alternately positioned between a resting position and a loading position, the loading position in particular being a position wherein the billet is arranged on the billet holder loader along the first extrusion direction; wherein said punch holder crosspiece is translatable along a second direction, perpendicular to said first extrusion direction, between a first position thereof and a second position thereof; wherein when the billet holder loader is in said resting position and said punch holder crosspiece is in the first position thereof, the translation of the punch holder crosspiece along said first extrusion direction in a first sense of translation, or sense of extrusion, causes a push by said punch against said billet and the extrusion of said billet; wherein said extrusion press comprises restraining means adapted to mutually restrain said punch holder crosspiece and said billet holder loader; wherein when the punch holder crosspiece is in the first position, it is restrained to the billet holder loader by means of said restraining means so that the translation of said punch holder crosspiece from the first position to the second position causes the movement of the billet holder loader from said resting position to said loading position; wherein when said billet holder loader is in said resting position, the translation of said punch holder crosspiece along said first extrusion direction in said sense of extrusion, in particular to extrude the billet, causes the mutual release of said punch holder crosspiece and said billet holder loader.

2. The press according to claim 1, wherein the punch holder crosspiece can take on a third position wherein the punch is at least partially inserted into a container adapted to at least partially contain said billet during the extrusion of said billet; and wherein by passing from the first position to the third position, the punch holder crosspiece (20) is released from the billet holder loader.

3. The press according to claim 1, configured so that the billet holder loader moves from the resting position to the loading position by being dragged by the punch holder crosspiece which moves from the first position thereof to the second position thereof.

4. The press according to claim 1, wherein when the punch holder crosspiece is in the second position, it is restrained to the billet holder loader by means of said restraining means so that the translation of said punch holder crosspiece from the second position to first position causes the movement of the billet holder loader from said loading position to said resting position; the extrusion press in particular being configured so that the billet holder loader moves from the loading position to the resting position by being pushed by the punch holder crosspiece which moves from the second position thereof to the first position thereof.

5. The press according to claim 1, configured so that when said billet holder loader is in said resting position, a translation of said punch holder crosspiece along said first extrusion direction in sense opposite to said sense of extrusion causes the mutual restraint of said punch holder crosspiece-and said billet holder loader.

6. The press according to claim 1, comprising a container adapted to at least partially contain said billet during the extrusion of said billet; in particular wherein the press is configured so that when the punch is outside the container, the punch holder crosspiece and the billet holder loader (24) are restrained to each other by means of said restraining means.

7. The press according to claim 1, wherein, in particular in use, said punch holder crosspiece and said billet holder loader are restrainable to each other by means of said restraining means and are releasable from each other according to the position along the extrusion direction of the punch holder crosspiece.

8. The press according to claim 1, wherein said restraining means comprise a first restraining element which is integral with said punch holder crosspiece, and a second restraining element which is integral with said billet holder loader.

9. The press according to claim 8, wherein said restraining means are configured, in use, to restrain and release said punch holder crosspiece and said billet holder loader to/from each other when the punch holder crosspiece is translated along the extrusion direction.

10. The press according to claim 8, wherein said first restraining element comprises a first surface and second surface distinct from each other, and the second restraining element comprises a first surface and second surface distinct from each other, the first surface of the first restraining element facing the first surface of the second restraining element, and the second surface of the first restraining element facing the second surface of the second restraining element when the first restraining element and the second restraining element are restrained to each other.

11. The press according to claim 8, wherein said first restraining element is a hook or is hook-shaped, and said second restraining element is a tooth.

12. An extrusion plant for producing metal extrudates by extruding a billet, comprising an extrusion press according to claim 1.

13. An extrusion method for producing metal extrudates by extruding a billet by means of an extrusion press according to claim 1, wherein there is provided a step in which the punch holder crosspiece is translated from the first position to the second position, and wherein the translation of said punch holder crosspiece from the first position to the second position causes the movement of the billet holder loader from said resting position to said loading position; in particular, wherein the billet holder loader is moved from the resting position to the loading position by being dragged by the punch holder crosspiece which moves from the first position thereof to the second position thereof; wherein there is provided a step in which the punch holder crosspiece and the billet holder loader are released from each other by translating the punch holder crosspiece along said first extrusion direction in the sense of extrusion.

14. The method according to claim 13, wherein there is provided a step in which the punch holder crosspiece is translated from the second position to the first position, and wherein the translation of said punch holder crosspiece from the second position to the first position causes the movement of the billet holder loader from said loading position to said resting position; in particular wherein the billet holder loader moves from the loading position to the resting position by being pushed by the punch holder crosspiece-which moves from the second position thereof to the first position thereof.

15. The method according to claim 13, wherein there is provided a mutual restraining step between the billet holder loader and the punch holder crosspiece by means of said restraining means; in particular wherein said restraining step provides the translation of the punch holder crosspiece along said first extrusion direction in sense opposite to the sense of extrusion.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0053] In the description of the invention, reference is made to the accompanying drawings, which are provided by way of non-limiting example, in which:

[0054] FIG. 1 shows a diagrammatic view of an extrusion press according to the prior art;

[0055] FIGS. 2 to 9 each show a sectional side view of a press according to an embodiment, in different moments, in particular in different moments of the extrusion process;

[0056] FIG. 10 shows a front view of another side of the press shown in FIGS. 2 to 9;

[0057] FIG. 11 shows detail A in FIG. 10.

[0058] The same elements or components have the same reference numerals.

DESCRIPTION OF EXPLANATORY EMBODIMENTS OF THE INVENTION

[0059] The present invention is particularly advantageous in the case of extrusion presses with a short stroke, this therefore being the reason for which the present invention is described below with particular reference to the applications thereof to a short stroke press, by way of exemplary and non-limiting example.

[0060] With reference to FIGS. 2 to 11, an example of extrusion press according to the invention is described.

[0061] The press comprises a punch holder crosspiece 20 which rigidly carries a relative punch 21; a container 22 adapted to at least partially contain the billet 27 during the extrusion of the billet 27; an extrusion die 23; and a billet holder loader 24.

[0062] The extrusion press in particular comprises actuation means 8 adapted to translate the punch holder crosspiece 20 (and therefore, also the punch 21) along the extrusion direction X, in particular both in the sense of extrusion and in the sense opposite to the sense of extrusion. Said actuation means 8 comprise one or more cylinder-piston systems, for example.

[0063] The billet holder loader 24 in particular comprises a seat 25 which preferably is formed by a cradle-shaped portion adapted to receive (i.e., to be loaded with) a billet 27. The billet holder loader 24 comprises thrust means 26, a pusher 26, for example. The thrust means 26 are adapted to be translated in the sense of extrusion so as to apply a push on billet 27, translating it in the sense of extrusion, in particular to insert it into container 22.

[0064] The punch holder crosspiece 20 is adapted to be translated, in particular by means of the aforesaid actuation means 8, along an extrusion direction X, or extrusion axis. In particular, the extrusion direction X is rectilinear. The punch holder crosspiece 20 can be translated along the extrusion direction X in two opposite senses of translation. In particular, one of the senses of translation is the sense of extrusion (from right to left in the drawings). The sense opposite to the sense of extrusion is also called sense of recovery.

[0065] The translation in the sense of extrusion results in a push by punch 21 against the billet 27 (which is in the extrusion position) and therefore, in the extrusion of billet 27 through the extrusion die 23.

[0066] As is apparent in particular in FIGS. 4 and 5, the punch holder crosspiece 20 is translatable transversely with respect to the extrusion direction X. In particular, the punch holder crosspiece 20 is translatable transversely with respect to the extrusion direction X, parallel to axis Y drawn in some drawings; said axis Y being in particular perpendicular to the extrusion direction X.

[0067] The punch holder crosspiece 20 is repositionable between a first position thereof, also called extrusion position (FIG. 4) and a second position thereof. In the first position (extrusion position), punch 21 is positioned along the extrusion axis X, in particular punch 21 is aligned with container 22 and therefore, in position adapted to start the extrusion step. In particular, in the first position, punch 21 is outside container 22, preferably completely outside container 22. In the second position, the punch holder crosspiece 20 and the relative punch 21 are spaced apart from the extrusion axis X, in particular so that punch 21 is not along the extrusion axis X. The punch holder crosspiece 20 in particular may be moved from the extrusion position to the side position, and vice versa, by means of actuation means which preferably act on the punch holder crosspiece 20.

[0068] The billet holder loader 24 is also translatable transversely with respect to the extrusion direction X and therefore, repositionable between a resting position thereof (FIG. 4) and a loading position thereof (FIG. 5) in which the billet 27 loaded on the billet holder loader 24 is positioned along the extrusion axis X, in particular aligned with container 22, and therefore in a position adapted to be inserted into container 22 by pusher 26 and then subjected to pushing by punch 21 (when the punch holder crosspiece 20 is in said extrusion position).

[0069] In the resting position, seat 25 for billet 27 is spaced apart from the extrusion axis X; in other words, when the billet holder loader 24 is in the resting position, a billet 27 arranged thereon is not arranged along the extrusion axis X.

[0070] The punch holder crosspiece 20 and the billet holder loader 24 are restrained to each other by means of the restraining means 40, 41 both when the punch holder crosspiece 20 is in the first position and when it is in the second position.

[0071] The punch holder crosspiece 20 can also take on a third position (see FIG. 9, for example), in which punch 21 is positioned along the extrusion axis X, and in which the punch holder crosspiece 20 (and therefore also punch 21) is more advanced, in the sense of extrusion, with respect to the first position. For example, the third position is a position in which punch 21 is partially or completely inserted in container 22. In order to pass from the first position to the third position, the punch holder crosspiece 20 translates along the extrusion axis X in the sense of extrusion.

[0072] In particular, in the third position, the punch holder crosspiece 20 is released from the billet holder loader 24, in particular the punch holder crosspiece 20 is not restrained to the billet holder loader 24 by means of the restraining means 40, 41.

[0073] In particular, in passing from the first position to the third position, the punch holder crosspiece 20 advantageously is released from the billet holder loader 24.

[0074] More generally, the first position is a retracted position of the punch holder crosspiece 20, and the third position is an advanced position of the punch holder crosspiece 20, and punch 21 is along the extrusion axis X in both positions.

[0075] The expressions retracted and advanced are used with reference to the sense of extrusion.

[0076] Numeral 30 in FIG. 10 identifies a movement element or member 30, which preferably is provided, translatable transversely both with respect to the extrusion direction X and with respect to the translation direction or axis Y of the billet holder loader 24 and of the punch holder crosspiece 20 (and therefore, along a translation direction which is substantially vertical with reference to FIG. 10); it should also be noted that the repositioning methods and the translation direction of member 30 are not fundamental for the purposes of the present invention, given that for example, solutions are possible according to which the movement member 30 can be repositioned by rotation and/or roto-translation according to translation directions other than those above. In any case, the movement member 30 is repositionable between a position in which it is loaded with a billet 27 (for example, picked from a depot or storage area) and a position in which billet 27 is deposited in seat 25 of the billet holder loader 24.

[0077] The extrusion methods of a billet 27 by means of a press according to the embodiment shown in the drawings may be summarized as follows.

[0078] As a first operation, which may be defined as preliminary to the actual extrusion (about at the end of the preceding extrusion), billet 27 is positioned, for example by means of the movement member 30, in seat 25 of the billet holder loader 24, the latter being positioned in the resting position.

[0079] The punch holder crosspiece 20 preferably is retracted (FIG. 2), i.e., translated in sense opposite to the sense of extrusion, preferably substantially simultaneously to the depositing of billet 27 on the billet holder loader 24; the retraction of the punch holder crosspiece 20 preferably is, for a stretch, simultaneous to a corresponding retraction of container 22, with detachment of container 22 from the extrusion die 23 (FIG. 3). Then, container 22 is advanced in the sense of extrusion up to being positioned again in contact with the extrusion die 23 (FIG. 4).

[0080] In particular, the above steps of retraction of the punch holder crosspiece 20 and retraction and successive advancement of container 22 result in the positioning of punch 21 outside container 22 (FIG. 4).

[0081] The successive steps provide repositioning the punch holder crosspiece 20 in the second position thereof (FIG. 5) and simultaneously repositioning the punch holder loader 24 from the resting position (FIG. 4) to the loading position (FIG. 5) in which billet 27 is positioned aligned with container 22 and therefore, in a position adapted to be introduced into container 22 and then extruded.

[0082] The following steps indeed provide the introduction of billet 27 into container 22 (FIG. 6) by means of pushing by pusher 26 during the translation thereof in the sense of extrusion. The push is performed by a dedicated actuator, a hydraulic or electric or pneumatic actuator, for example. Pusher 26 is also translatable in opposite sense, and therefore in retraction with respect to container 22.

[0083] The billet holder loader 24 (which at this point is unloaded) is then moved into the resting position, in particular laterally with respect to the press body, and therefore in a position adapted to receive a new billet; advantageously, the movement of the billet holder loader 24 occurs because the latter is pushed by the punch holder crosspiece 20 which is repositioned in the first position thereof in which punch 21 is aligned with container 22 (FIG. 7). At this point, the actual extrusion step may start with a push of billet 27 through the extrusion die 23 (FIGS. 8 and 9) by means of punch 21.

[0084] As mentioned, one of the peculiarities of the press according to the present invention relates to the fact that the repositioning of the billet holder loader 24 between the resting position and the loading position, and vice versa, does not occur by means of a dedicated actuator designed for the purpose (hydraulic or electric or pneumatic, for example), as it does in the case of presses according to the prior art. Instead, the press advantageously is configured so that the billet holder loader 24 passes from the resting position to the loading position, and vice versa, by virtue of the action of the punch holder crosspiece 20 on the billet holder loader 24. In particular, the press advantageously is configured so that during the repositioning of the punch holder crosspiece 20 from the first position thereof (FIG. 4) into the second position thereof (FIG. 5), the billet holder loader 24 is dragged by the punch holder crosspiece 20 from the resting position (FIG. 4) to the loading position (FIG. 5) in which billet 27 is positioned aligned with container 22. Moreover, the press advantageously is configured so that the billet holder loader 24 passes from the loading position to the resting position by being pushed by the punch holder crosspiece 20, while the latter passes from the second position thereof to the first position thereof (extrusion position).

[0085] In other words, in order to pass from the resting position to the loading position, and vice versa, the press is configured so that the billet holder loader 24 is moved by the punch holder crosspiece 20, in particular moving integrally therewith along direction Y.

[0086] Advantageously, the press is configured so that the punch holder crosspiece 20 and the billet holder loader 24 can be restrained to each other by means of the restraining means 40, 41 so that a translation of the punch holder crosspiece 20 parallel to axis Y corresponds to a translation of the billet holder loader 24 parallel to axis Y. In particular, said restraining means 40, 41 are shaped so as to allow a movement of the billet holder loader 24 integrally with the punch holder crosspiece 20 along said second direction Y.

[0087] When the punch holder crosspiece 20 and the billet holder loader 24 are restrained to each other by means of the restraining means 40, 41, the punch holder crosspiece 20 can translate along the extrusion axis X in the sense of extrusion, releasing itself from the billet holder loader 24. In particular, the restraining means 40, 41 are shaped or configured so that the punch holder crosspiece 20, moving in the sense of extrusion, is released from the billet holder loader 24, in particular without causing a movement of the billet holder loader 24.

[0088] Preferably, the press is configured so that when punch 21 is extracted, in particular completely extracted, from container 22, the punch holder crosspiece 20 and the billet holder loader 24 are restrained to each other by means of said restraining means 40, 41.

[0089] Advantageously, the press is configured so that when the punch holder crosspiece 20 translates in the sense of extrusion, in particular to extrude billet 27, in particular starting from said first position, it causes the release between the punch holder crosspiece 20 and the billet holder loader 24, preferably while punch 21 is inserted in container 22. In particular, only the translation of the punch holder crosspiece 20 along the extrusion direction in the sense of extrusion causes the mutual release between the punch holder crosspiece 20 and the billet holder loader 24; i.e., in other words, said translation is sufficient to cause said release.

[0090] Preferably, the restraining means 40, 41 comprise, or consist of, a first restraining element 40 which is integral with said punch holder crosspiece 20, and a second restraining element 41, preferably a tooth, which is integral with said billet holder loader 24.

[0091] By mere way of example, the first restraining element 40 preferably is a hook or is hook-shaped, and the second restraining element preferably is a tooth; or vice versa, for example.

[0092] As mentioned above, said restraining means 40, 41 are configured (or shaped) to restrain and release, in use, said punch holder crosspiece 20 and said billet holder loader 24 to/from each other when the punch holder crosspiece 20 is translated along the extrusion direction X.

[0093] With particular reference to FIG. 11, the punch holder crosspiece 20 is equipped with a hook 40, for example. Hook 40 may be formed by a portion of the punch holder crosspiece 20, for example. In particular, hook 40 extends from crosspiece 20 in direction distal from punch 21 (towards the billet holder loader 24 when the latter is in the resting position). The billet holder loader 24 is equipped with tooth 41, which extends towards the punch holder crosspiece 20. Hook 40 and tooth 41 are rigidly restrained to crosspiece 20 and to the billet holder loader 24, respectively. In particular, tooth 41 forms a corresponding abutment with hook 40.

[0094] Hook 40 defines a downwards facing abutment surface 42, while tooth 41, or corresponding abutment, is shaped so as to define an upwards facing abutment surface 43. The abutment surface 43 in particular corresponds with the abutment surface 42 of hook 40.

[0095] Surface 42 and surface 43 preferably are parallel to each other.

[0096] Surface 42 and surface 43 preferably are flat.

[0097] Surface 42 and surface 43 preferably extend parallel to the extrusion axis X.

[0098] By way of non-limiting example, surface 42 and surface 43 are vertical or substantially vertical.

[0099] When hook 40 is restrained with tooth 41, surface 42 and surface 43 are facing each other.

[0100] Surface 42 is adapted to abut with surface 43 so that the punch holder crosspiece 20 may drag the billet holder loader 24.

[0101] Hook 40 in particular also comprises a surface 45; the distance between surface 45 and punch 21 preferably is less than the distance between surface 42 and punch 21. Surface 45 preferably is lower with respect to surface 42.

[0102] Tooth 41 in particular also comprises a surface 46; the distance between surface 46 and punch 21 preferably is less than the distance between surface 43 and punch 21. Surface 45 and surface 46 preferably are parallel to each other.

[0103] Surface 45 and surface 46 preferably are flat. Surface 45 and surface 46 preferably extend parallel to the extrusion axis X.

[0104] Surface 46 preferably is lower with respect to surface 45.

[0105] By way of non-limiting example, surface 45 and surface 46 are vertical or substantially vertical.

[0106] When hook 40 is restrained with tooth 41, surface 45 and surface 46 are facing each other. Surface 46 is adapted to abut with surface 45 so that the punch holder crosspiece 20 can push the billet holder loader 24. The surfaces 42 and 43 preferably are such whereby with tooth 41 in position below hook 40, the mutual positioning of surface 42 and surface 43 results in the mutual restraint of hook 40 and tooth 41, and therefore of the punch holder crosspiece 20 and the billet holder loader 24.

[0107] With the billet holder loader 24 in resting position (FIG. 4), the retraction of the punch holder crosspiece 20 in sense opposite to the sense of extrusion results in the positioning of hook 40 in position above tooth 41, and therefore in the mutual restraint of the punch holder crosspiece 20 and the billet holder loader 24; contrarily, with the billet holder loader 24 in the resting position (FIG. 4), the advancement of the punch holder crosspiece 20 in the sense of extrusion results in the mutual release of hook 40 and tooth 41, and therefore of the punch holder crosspiece 20 and billet holder loader 24 (see FIG. 9 in particular).

[0108] Thus, it has been shown that with crosspiece 20 and loader 24 mutually restrained by means of the mutual restraint of hook 40 and tooth 41 as described above, the repositioning of crosspiece 20 from the first position into the second position results in a dragging of loader 24 by the punch holder crosspiece 20, and therefore in the resulting repositioning of the billet holder loader 24 from the resting position (FIG. 4) into the loading position (with billet 27 aligned with container 22). In particular, as mentioned, the surface 42 of hook 40 abuts against the surface 43 of tooth 41, whereby the punch holder crosspiece 20 drags the billet holder loader 24.

[0109] Contrarily, with the punch holder crosspiece 20 in the second position and the billet holder loader 24 in the loading position (but unloaded at this point), the repositioning of the punch holder crosspiece 20 from the second position into the first position (with punch 21 aligned with container 22) results in a push on the billet holder loader 24 by the punch holder crosspiece 20, and therefore in the resulting repositioning of the billet holder loader 24 from the loading position (FIG. 4) into the resting position (ready to receive the next billet).

[0110] In particular, when the punch holder crosspiece 20 moves from the second position to the first position, surface 45 pushes against surface 46, thus causing a movement of the billet holder loader 24.

[0111] When the punch holder crosspiece 20 and the billet holder loader 24 are not restrained to each other, hook 40 and tooth 41 are not restrained to each other. In particular, surface 42 and surface 43 are not facing each other, and surface 45 and surface 46 are not facing each other.

[0112] It has therefore been shown that a press according to the invention is capable of ensuring the desired results of overcoming, or at least limiting, the drawbacks encountered in the prior art. In particular, the present invention provides an extrusion press, for example, but not only, of the short stroke type, which does not require the use of additional dedicated actuators for moving the billet holder loader and therefore positioning the billet in extrusion position. Thereby, it is possible to make the press with curbed costs compatible with the needs of the market, avoid or at least limit the need to plan and implement regular, and also in this case dedicated, maintenance operations, and therefore again with subsequent increase in the press management costs, and also avoid or at least reduce the risks of accidental interference of the movable press components (the punch holder crosspiece and billet holder loader in particular), for example in the event of erroneous synchronism between the respective movements, therefore preventing the risk of also serious damage to said movable components, and therefore lengthy machine downtime and/or lengthy and costly repair operations. Moreover, the costs associated with moving the punch holder crosspiece are reduced.

[0113] The invention also relates to an extrusion method for producing metal extrudates by extruding a billet 27 by means of an extrusion press according to the invention, wherein a step is provided in which the punch holder crosspiece 20 is translated from the first position to the second position, and in which the translation of said punch holder crosspiece 20 from the first position to the second position causes the movement of the billet holder loader 24 from said resting position to said loading position; in particular, in which the billet holder loader 24 is moved from the resting position to the loading position by being dragged by the punch holder crosspiece 20 which moves from the first position thereof to the second position thereof.

[0114] A step in particular is provided in which the punch holder crosspiece 20 is translated from the second position to the first position, and in which the translation of said punch holder crosspiece 20 from the second position to the first position causes the movement of the billet holder loader 24 from said loading position to said resting position; in particular in which the billet holder loader 24 moves from the loading position to the resting position by being pushed by the punch holder crosspiece 20 which moves from the second position thereof to the first position thereof.

[0115] Advantageously, there is provided a mutual restraining step between the billet holder loader 24 and the punch holder crosspiece 20 by means of said restraining means 40, 41, in particular so that the billet holder loader 24 can be moved from said resting position to said loading position, and vice versa; in particular in which said restraining step provides the translation of the punch holder crosspiece 20 along said first extrusion direction X in sense opposite to the sense of extrusion, in particular after extruding billet 27.

[0116] In particular, the mutual restraining step is performed starting from a condition in which the punch holder crosspiece 20 and the billet holder loader 24 are released from each other, in particular completely released from each other; for example, when the punch holder crosspiece 20 is in the aforesaid third position.

[0117] Advantageously, there is provided a step in which the punch holder crosspiece 20 and the billet holder loader 24 are released from each other by translating the punch holder crosspiece 20 (i.e., by translating the punch holder crosspiece 20) along said first extrusion direction X in the sense of extrusion, in particular to extrude billet 27. Thus, advantageously, the translation of the punch holder crosspiece 20 along the extrusion direction in the sense of extrusion to extrude billet 27 causes the release between the punch holder crosspiece 20 and the billet holder loader 24.

[0118] It should be clear that the present description is provided only by way of non-limiting example. The scope of protection of the present invention is thus defined by the claims.