DEVICE FOR STAMPING BY MAGNETIC FORMING AND ASSOCIATED METHOD

Abstract

A device for stamping a blank in order to produce a stamped part. The device includes a punch including a bearing surface, an anvil, and magnetic field generator. The stamping device has an initial position where the bearing surface of the punch receives a portion of a first surface of the blank, the anvil and the magnetic field generator are arranged on either side of another portion of the blank, with the anvil facing the first surface, and the magnetic field generator facing a second surface opposite the first surface. The magnetic field generator applies a pressure on the blank in a direction towards the anvil. The stamping device is also configured to move the punch relative to the magnetic field generator in a direction away from the anvil.

Claims

1. A Device for stamping a blank in order to produce a stamped part comprising: a punch comprising a bearing surface, an anvil, means for generating a magnetic field, said device for stamping being configured, in an initial position, in such a way that: the bearing surface of the punch is intended for receiving a portion of a first surface of the blank, the anvil and the means for generating a magnetic field are intended for being arranged on either side of another portion of the blank, with the anvil facing the first surface, and the means for generating a magnetic field facing a second surface, opposite the first surface, at a distance from said second surface, said means for generating a magnetic field being intended and configured to apply a pressure on the blank towards the anvil, in a direction ZZ, thrusting said blank on said anvil, the device for stamping comprising movement means arranged to move the punch, relative to the means for generating a magnetic field, in a direction opposite the direction ZZ.

2. The device for stamping according to claim 1, wherein the movement means comprise a linear actuator.

3. The device for stamping according to claim 1, comprising adjusting means configured to adjust the space between the anvil and the means for generating a magnetic field.

4. The device for stamping according to claim 1, comprising a blank-holder configured to impose a retaining pressure on the movement of the blank, against the punch.

5. A method for stamping by magnetic pulse a blank in order to produce a stamped part, using a device for stamping in accordance with claim 1, comprising: a) positioning the blank in the device for stamping, b) subjecting the blank to a magnetic field caused by the means for generating a magnetic field in such a way that a pressure is exerted on the second surface of the blank in a direction ZZ and thrusts said blank against the anvil, and c) moving the punch by the movement means in a direction opposite the direction ZZ, with the steps b) and c) being repeated until the desired shape is obtained for the finished stamped part.

6. The method for stamping according to claim 5, wherein as the punch moves, a radial pressure is exerted on the blank in the direction of said punch, thrusting said blank on said punch.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0047] The present disclosure shall be better understood when reading the description hereinafter, given as an example that is in no way limiting, and given in reference to the figures which show:

[0048] FIGS. 1 to 4 illustrate schematic cross-section views of an aspect of a device for stamping according to the present disclosure showing the successive steps of stamping of a blank,

[0049] FIG. 5 is a schematic view equivalent to FIG. 1 showing a particular embodiment of the device for stamping with a blank-holder.

[0050] In these figures, identical references from one figure to another designate identical or similar elements. For reasons of clarity, the elements shown are not shown to scale, unless mentioned otherwise.

DETAILED DESCRIPTION

[0051] A device for stamping 10, such as shown in FIGS. 1 to 4, is intended for the stamping of blanks 50, for the purpose of producing stamped parts, in particular deep-drawn parts.

[0052] In an aspects of the present disclosure, the blanks 50 are made of a metallic material, such as steel.

[0053] The blank 50 has a first surface 51 and a second surface 52, opposite the first.

[0054] In a preferred non-limiting aspect of the present disclosure, the device for stamping 10, such as shown as a cross-section in FIGS. 1 to 4, is adapted to the production of cups. The term cup means a stamped part having a hollow cylindrical shape.

[0055] Those skilled in the art will easily understand that the teaching of this present disclosure can be transposed to other aspects.

[0056] In this description, the terms such as upper, lower, top, bottom, left, right are used with a concern for simplicity, in reference to the orientation of the various elements shown in FIGS. 1 to 4. However, unless mentioned otherwise, these terms characterise only the relative arrangement of these elements, after a possible imaginary rotation in relation to the effective orientation of the whole in space.

[0057] The device for stamping 10 comprises a first frame 20 and a second frame 30. The first frame 20 can represent an upper portion of the device for stamping and the second frame 30, a lower portion, such as shown in figures. As an alternative, and without leaving the scope of the present disclosure, the first frame 20 can represent a lower portion, left or right, of the device for stamping and the second frame 30, respectively an upper portion, right or left.

First Frame

[0058] The first frame 20 carries a punch 21, preferably central.

[0059] Said punch comprises a bearing surface 211 and lateral walls 212.

[0060] In the particular example wherein the final stamped part is a cup, the punch has the form of a cylindrical body, preferably full.

[0061] According to the present disclosure, the blank 50 is intended to conform to the shape of an outer surface of the punch 21.

[0062] Thus, the punch 21 has, on said outer surface, an imprint that corresponds to the shape of the final part, once stamped.

[0063] The punch 21 is mobile in translation, according to a vertical axis, thanks to movement means 23 that can move the punch between a retracted position and a deployed position.

[0064] In the example of FIG. 4, the punch 21 is shown in deployed position.

[0065] The movement means 23 are actuated manually or automatically.

[0066] In an aspect of the present disclosure, the movement means 23 comprise at least one linear, hydraulic or pneumatic, actuator, such as a cylinder operating between the first frame 20 and the punch 21. In this embodiment, preferably, the fixed portion of the linear actuatorfor example the body of the cylinderis housed in a recess (not shown) made in the first frame 20. The mobile portion of the linear actuator, for example the piston of the cylinder, is able to be moved out of the recess in order to deploy the punch 21 and able to be moved to the recess in order to return the punch 21 to its initial position. Particularly advantageously, the movement of the punch 21 is controlled by control means.

[0067] In an alternative aspect of the present disclosure, the movement means 23 have the form of a support carrying a pressure screw able to cooperate with the punch 21 in order to move it in translation.

[0068] The first frame 20 further comprises an anvil 22.

[0069] Said anvil is arranged around lateral walls 212 of the punch 21, when said punch is in its retracted position.

[0070] The anvil and the punch are spaced apart from one another by a predetermined distance.

[0071] In an aspect of the present disclosure, when the punch 21 has the form of a cylindrical body, the anvil 22 has the form of an annular body surrounding the punch.

[0072] In an aspect of the present disclosure, the anvil 22 can form the first frame 20.

[0073] The punch, on its bearing surface, and the anvil, on a free end 221, are at separate heights.

Second Frame

[0074] The second frame 30 comprises a hollow body that delimits an open cavity 33.

[0075] As shown in FIGS. 1 to 4, the hollow body is formed from an upper portion 31 and of lateral sides 32.

[0076] The second frame 30 is arranged with respect to the first frame 20 in such a way that: [0077] the open cavity 33 of the hollow body is intended to receive the punch 21, when the latter is moved vertically, in a direction ZZ, to its deployed position, [0078] the free ends 321 of the lateral sides 32 of the hollow body are substantially facing the anvil 22.

[0079] The free ends 321 of the lateral sides 32 of the hollow body of the second frame are substantially facing the free end of the anvil 22.

[0080] The hollow body and the punch 21 have dimensions such that the punch 21 can be moved freely in the open cavity 33 with, between their respective surfaces, a non-negligible space for the passing of the blank 50, in its thickness.

[0081] In a non-limited aspect of the present disclosure, when the punch 21 has the form of a cylindrical body, the open cavity 33 has the form of an annular body surrounding the punch.

[0082] In an aspect of the present disclosure, the outer surface of the punch 21 and the inner wall of the hollow cavity 33 are of practically the same shape, to the nearest thickness of the final stamped part and an operating clearance.

[0083] The second frame 30 further comprises means for generating a magnetic field 34.

[0084] The means for generating a magnetic field 34 are arranged, on free ends 321 of the lateral sides 32 of the hollow body, facing the anvil 22.

[0085] As shown in FIGS. 1 to 4, the elements that form the device for stamping, namely the punch, the anvil and the means for generating a magnetic field 34 are arranged with respect to one another in such a way that: [0086] in an initial position of the device for stamping (FIG. 1), i.e. before the beginning of the method for stamping, the blank 50 is positioned flat between the various elements, [0087] in a final position of the device for stamping (FIG. 4), i.e. at the end of the method for stamping, the blank 50 is thrust around the punch 21, forming the stamped part.

[0088] More precisely, regarding the initial position of the device for stamping shown in FIG. 1, the punch 21 is positioned in such a way that its bearing surface 211, in a retracted or intermediate position, is intended to receive a central portion of the first surface 51 of the blank 50. The blank 50 rests on the bearing surface of the punch. The anvil is positioned facing the first surface 51 of the blank 50, on a peripheral part of said blank and the means for generating a magnetic field 34 are positioned facing the second surface 52 of the blank, also on the peripheral portion of said blank. The first surface 51 of the blank is arranged at a distance from the free end 221 of the anvil 22.

[0089] The means for generating a magnetic field 34 are configured for and intended to create a magnetic field concentrated in a delimited space and over a very short period.

[0090] Preferably, such as shown in FIGS. 1 to 4, the means for generating a magnetic field 34, such as positioned, are thus able and intended to imprint on the blank 50 a pressure in the direction of the anvil 22, in a direction ZZ. The pressure exerted partially thrusts the blank against the anvil 22, causing a deformation of said blank.

[0091] In an aspect of the present disclosure, the means for generating a magnetic field 34 are a coil.

[0092] The means for generating a magnetic field are more preferably an integral part of a set that further comprises an electrical energy storage unit and one or several switches (not shown).

[0093] The electrical energy storage unit is configured for and intended to store a moderate energy, for example of about a few kilojoules to a few tens of kilojoules (kJ).

[0094] In a preferred aspect of the present disclosure, the storage unit is a discharge capacitor battery.

[0095] The first frame 20, the second frame 30, the anvil 22 and the punch 21 are preferably made from a metallic metal, for example steel, so as to have a structural resistance that makes it possible to contain the high pressures generated by the impact of the blank 50 on the anvil 22, during the method for stamping which shall be described hereinafter.

[0096] In an aspect of the present disclosure, the device for stamping 10 comprises adjusting means (not shown) arranged to move the anvil 22 vertically, in translation. Such means make it possible to reduce or to increase the space e that separates the anvil from the means for generating a magnetic field 34. The sizing of the space e is according in particular to the material and the geometric shape of the punch, as well as the pulse of the current. The sizing of the space e is maximised in order to reduce the number of discharges and consequently the forming time.

[0097] In aspects of the present disclosure, the adjusting means are a linear, hydraulic or pneumatic actuator.

[0098] In an aspect of the present disclosure, shown in FIG. 5, the device for stamping 10 comprises a blank-holder 60. The blank-holder is housed in the open cavity 33. It is configured to exert a pressure between the blank 50 and the punch 21, when said blank is in position on the punch. The adjusting of this pressure will condition the feeding of the blank during the forming thereof.

[0099] In an aspect of the present disclosure, the blank-holder is maintained thrust against the second surface 52 of the blank 50 by means of compression 61.

[0100] In aspects of the present disclosure, the means of compression are a spring or a linear, hydraulic or pneumatic actuator, such as a cylinder, operating between the blank-holder and an inner surface 311 of the second frame 30.

[0101] An example of the method for stamping from such a device for stamping is now described.

[0102] In a prior step, the blank 50 is cut, to the desired dimensions (length and width, or diameter, and thickness), in a sheet metal.

[0103] In a first step, referred to as step a), the blank 50 is positioned in the device for stamping 10.

[0104] The blank 50, of substantially flat shape, is positioned between the first frame 20 and the second frame 30, as shown in FIG. 1.

[0105] In an aspect of the present disclosure, the blank 50 is arranged on the one hand on its central portion on the punch 21. The blank 50 is arranged in such a way that its first surface 51 bears against the bearing surface 211 of the punch.

[0106] When the device for stamping comprises a blank-holder 60, the blank 50 is maintained bearing against the bearing surface 211 of the punch 21 by said blank-holder.

[0107] The blank 50 is arranged on the other hand, on its peripheral portion, between the means for generating a magnetic field 34 and the anvil 22. The first surface 51 of the blank is arranged facing the anvil 22, at a distance from the latter. The second face 52 of the blank is arranged facing the means for generating a magnetic field 34.

[0108] The blank bears against the bearing surface 211 of the punch 21. The blank does not bear against the anvil 22.

[0109] In an aspect of the present disclosure, when the blank 50 has been placed on the punch, the punch 21 is moved, from its retracted position, in translation along the direction ZZ, in order to offset the blank 50 in such a way that the second surface 52 of said blank, on the peripheral portion of the blank, is placed in immediate proximity, for example of about a millimetre, from the means for generating a magnetic field 34.

[0110] The method then comprises a second step, referred to as step b), of deforming the blank 50 via magnetic forming.

[0111] The ends of the blank 50, located in the vicinity of the means for generating a magnetic field 34, are subjected to a magnetic field coming from the means for generating a magnetic field 34 in such a way that a pressure, axial, is exerted against the second surface 52 of the blank 50, and tightly thrusts said blank against the anvil 22. The arrow shown in FIG. 2 shows the axial pressure exerted on the blank 50.

[0112] The blank 50 is consequently deformed to bear against the anvil 22.

[0113] During this step b) shown in FIG. 2, the means for generating a magnetic field 34 progressively deforms the peripheral portion of the blank 50 so as to obtained a first stamp with a depth P1, less than a depth P of the final stamp sought.

[0114] At the end of this step b), the blank 50 is deformed and has a first stamp.

[0115] In a third step, referred to as step c), the punch 21 is moved.

[0116] The punch 21 is translated by the movement means 23, in the direction ZZ, in such a way as to drive in its movement the blank 50, by moving away the peripheral portion of the blank 50 from the anvil 22, as shown in FIG. 3.

[0117] The movement of the punch 21, and consequently that of the blank 50, is carried out in the direction opposite the direction of the movement of the blank 50 during the step b).

[0118] In an aspect of this third step, the punch 21 is moved in the direction ZZ by a height that is sufficient for the second surface 52 of the blank 50 to return to the immediate vicinity of the means for generating a magnetic field 34.

[0119] In an aspect of the present disclosure, the relative movement of the punch 21 with respect to the means for generating a magnetic field 34 and to the anvil 22 is carried out incrementally.

[0120] In an aspect of the present disclosure, the relative movement of the punch with respect to the means for generating a magnetic field and to the anvil is carried out continuously. The forming of the blank 50 by the means for generating a magnetic field 34 can be considered as instantaneous with respect to the movement of the punch. Indeed, the duration of the movement of the punch is generally very slow (of about one second) with respect to the duration of the magnetic pulse generated by the means for generating a magnetic field 34 (of about one microsecond). In the particular case of this embodiment, the second and third steps are carried out simultaneously without modifying the result of said steps.

[0121] In a fourth step, the steps b) and c) are reproduced sequentially.

[0122] The steps b) and c) are reproduced until the obtaining of the depth P of the final stamped part that is sought to be obtained.

[0123] As the relative movement of the punch 21 takes place with respect to the means for generating a magnetic field 34, said means for generating a magnetic field 34 advantageously exert an axial pressure on the blank 50 in the direction of the anvil 22, thrusting said blank on said anvil. Said means for generating a magnetic field 34 also exert a radial pressure on the blank 50 in the direction of the punch 21, thrusting said blank on said punch. This radial pressure of the blank 50 against the punch 21 advantageously allows said blank to perfectly match the shape of the outer surface of the punch 21.

[0124] The number of iterations of the steps b) and c) depends in particular on the material comprising the blank, on the desired depth of the stamped part.

[0125] This present disclosure is not limited to the preferred embodiments described hereinabove as non-limiting examples and to the alternatives mentioned. It also relates to the alternative embodiments within the scope of those skilled in the art.

[0126] The description hereinabove clearly shows that through its various characteristics and their advantages, this present disclosure achieves the objectives that were set for it. In particular, it proposes a device for stamping suitable for the production of stamped parts, in particular of deep-drawn parts, without generating folds or tears on the part. Such a device for stamping and of the associated method for stamping can make it possible to work on the part mainly in compression but also in expansion. In addition, as the high speeds tends to minimise the appearance of folds, the present disclosure advantageously makes it possible to produce turned out edges.