Integration of a magnetic signature into a ferromagnetic object manufactured by additive manufacturing

Abstract

Integration of a magnetic signature into a ferromagnetic object manufactured by additive manufacturing. Additive manufacturing process for a first ferromagnetic object (9), characterized in that it comprises a step of varying at least one parameter of the manufacturing process to locally modify a magnetic permeability of said first object, in order to integrate a magnetic signature into said first object. Figure for the abstract: Figure 1

Description

Title of the invention: Integration of a magnetic signature into a ferromagnetic object manufactured by additive manufacturing Technical field of the invention

[0001] The invention relates to a method for additively manufacturing a ferromagnetic object. The invention also relates to a ferromagnetic object obtained by such a manufacturing method. The invention also relates to a method for identifying such an object. State of the prior art

[0002] Additive manufacturing has revolutionized the manufacturing paradigm in recent years by offering the possibility of creating parts with very complex shapes, even impossible to obtain using conventional processes, without tools and in very short timeframes. Among the different additive manufacturing techniques, we find the wire arc technologies or WAAM (from the Anglicism "Wire Arc Additive Manufacturing") which belongs to the family of direct energy deposition (DED). According to the ASTM F 279-12A standard (Standard Terminology for Additive Manufacturing Technologies), these processes are defined as the combination of an electric arc used as a heat source and a wire used as a raw material supply.

[0003] Objects manufactured by additive manufacturing can be used in any type of industry. Since the manufacture of these objects does not require any specific tooling, they are relatively easy to reproduce by any manufacturer with an additive manufacturing device. However, the quality of objects manufactured by additive manufacturing can vary greatly. This depends in particular on the manufacturer's mastery of the various parameters and the quality of the materials used.

[0004] In this context, it appears desirable to guarantee the origin and improve the traceability of objects manufactured by additive manufacturing. To this end, a manufacturer can engrave an identification number on the part. This means of identification is nevertheless too easily falsified. In addition, the integration of an identification number on the object requires specific operations, as well as a free surface on which to affix this number, which is not always possible. Presentation of the invention

[0005] The aim of the invention is to provide an additive manufacturing method and a ferromagnetic object obtained by such a method overcoming the above drawbacks and improving the methods and objects manufactured by additive manufacturing known from the prior art.

[0006] The aim of the invention is in particular to provide a method for the additive manufacturing of an object making it possible to obtain reliable identification and authentication of said object. object. Summary of the invention

[0007] The invention relates to a method for additive manufacturing of a first ferromagnetic object, the method comprising a step of varying at least one parameter of the manufacturing method to locally modify a magnetic permeability of said first object, to integrate a magnetic signature into said first object.

[0008] Said additive manufacturing process may be of the arc-wire type.

[0009] Said variations of at least one parameter may comprise: - a variation in the deposition temperature of a ferromagnetic material, and / or - a variation in the deposition speed of a ferromagnetic material, and / or - a variation in the deposition flow rate of a ferromagnetic material, and / or - a variation in the deposition trajectory of a ferromagnetic material, and / or - the projection of a cooling fluid.

[0010] The manufacturing method may comprise a variation in the deposition speed and a variation in the deposition flow rate of a ferromagnetic material, the deposition speed and the deposition flow rate being synchronized at each instant so as to obtain a constant deposition quantity.

[0011] Said first object can be manufactured by additive manufacturing on a support comprising a first zone and a second zone, the first zone having different thermal properties from the second zone.

[0012] The manufacturing method may then comprise a step of smoothing one face of said first object, said face comprising areas having different magnetic permeabilities.

[0013] The invention also relates to a method for additive manufacturing of a set of objects comprising a first object and at least one second object, each object of the set of objects being manufactured by a manufacturing method as defined previously, each object of the set of objects comprising an identical geometric shape, at least one parameter of the manufacturing method of the second object being different from a manufacturing parameter of the first object so that the magnetic signature of the second object is different from the magnetic signature of the first object.

[0014] The invention also relates to a ferromagnetic object manufactured by an additive manufacturing method as defined above, said object comprising local variations in magnetic permeability forming a magnetic signature of said object.

[0015] The invention also relates to a set of objects manufactured by an additive manufacturing method as defined above, each object of the set of objects including a different magnetic signature.

[0016] The invention also relates to a method for identifying an object manufactured by additive manufacturing as defined above, the identification method comprising the detection of local variations in magnetic permeability forming the magnetic signature of the object by means of a probe.

[0017] The identification method may comprise calculating a function establishing a link between a phase variation of an impedance of the probe as a function of an excitation frequency.

[0018] Said probe may comprise a coil provided with a magnetic core.

[0019] Said probe may further comprise a magnet attached to the coil.

[0020] The invention also relates to a method for authenticating an object comprising: - the manufacture by a manufacturer of said object by an additive manufacturing process as defined above, said object comprising local variations in magnetic permeability forming a magnetic signature of the object, and - communicating a location of the magnetic signature on said object and / or a procedure for reading the magnetic signature of the first person to a second person, then - the implementation of the method of identifying said object as defined previously. Presentation of figures

[0021] These objects, characteristics and advantages of the present invention will be explained in detail in the following description of a particular embodiment made without limitation in relation to the attached figures among which:

[0022] [Fig.l] is a schematic view of an additive manufacturing device according to one embodiment of the invention.

[0023] [Fig.2] is a schematic view of an object manufactured by additive manufacturing according to an embodiment of the invention and of a probe configured to identify said object.

[0024] [Fig. 3] is a block diagram of the manufacture of an object according to one embodiment of the invention.

[0025] [Fig.4] is a view of an equivalent electrical diagram of said object and said probe.

[0026] [Fig.5] is a schematic view of a second object manufactured by additive manufacturing according to an embodiment of the invention, a magnetic signature of the second object being different from the magnetic signature of the object of [Fig.2].

[0027] [Fig.6] is a block diagram of the identification of an object according to one embodiment of the invention. Detailed description

[0028] [Fig.l] illustrates a device 1 for additive manufacturing by direct energy deposition (DED). The device 1 comprises on the one hand a means for supplying a ferromagnetic material, in particular in the form of a wire of ferromagnetic material, and on the other hand an energy source capable of melting the ferromagnetic material, to gradually deposit it on a support. The ferromagnetic material intended to form an object may be iron-based, in particular steel. Alternatively, the ferromagnetic material could also be nickel-based and / or cobalt-based.

[0029] More specifically, the device 1 is an arc-wire type additive manufacturing device. The device 1 comprises a robot 2 equipped with a torch 3 enabling additive manufacturing on a support 4. The support 4 is arranged on a movement means 5 enabling the position of the support 4 in space to be controlled. The robot 2 is connected to a generator 6, which is itself connected to a gas tank 7. Finally, the device 1 comprises a control unit 8 configured to control the torch 3 and the movement means 5.

[0030] The control unit 8 thus makes it possible to control various parameters of the manufacturing process, including: - the deposition temperature, or in other words the temperature to which the ferromagnetic material wire is brought to melt it, and / or - the deposition rate, i.e. the quantity of ferromagnetic material deposited per unit of time, and / or - the deposition trajectory, i.e. the direction in which the support 4 moves thanks to the movement means 5, and / or - the deposition speed, i.e. the speed of movement of the support 4 relative to the torch 3.

[0031] In addition, the device 1 may also comprise a means for projecting a cooling fluid such as air or oil to cool the temperature of the material after it has been deposited on the object being manufactured. Advantageously, the control unit also makes it possible to control the fluid projection means.

[0032] According to the invention, at least one parameter of the manufacturing process is varied so as to create a magnetic signature integrated into the manufactured object. Indeed, it has been discovered that the modification of certain parameters of the manufacturing process, in particular the parameter(s) which impact the temperature of the ferromagnetic material at the moment when it is deposited on the manufactured object, leads to a modification of the microstructure of the material, and therefore to a local modification of the permeability magnetic (expressed in Henry per meter) of the object. It is thus possible to manufacture an object comprising different zones, each comprising a given magnetic permeability. These different zones thus form an invisible code which makes it possible to identify the object.

[0033] These different zones can be distributed along a given direction of the object, thus forming a unidirectional code, such as a bar code. These different zones can also be distributed over a given surface of the object, thus forming a matrix code.

[0034] This gives a magnetic signature integrated into the object which is completely invisible. This magnetic signature can then be detected by a suitable probe, so as to decode the code integrated into the object.

[0035] The object thus comprises at least one zone whose magnetic permeability is modified through the use of specific manufacturing parameters. Preferably, the object comprises at least two such distinct zones, or even an even greater number of zones.

[0036] The local modification of the magnetic permeability of the material is obtained without inserting an element or component specifically provided for this purpose. Thus, the manufacturing process remains simple. The strength and / or dimensions of the object thus produced are not significantly impacted.

[0037] These zones can be grouped on the same face or the same region of the object. It may be chosen to group these zones in an easily accessible region and / or in a region intended to withstand less mechanical stress. Indeed, the mechanical stresses possibly supported by the object are likely to modify, or even erase, its mechanical signature. The different zones of the object in which the magnetic permeability is modified can also be kept secret so as to make any attempt to reproduce the magnetic signature even more difficult.

[0038] Advantageously, during the manufacturing process, the deposition speed (expressed in unit of distance per unit of time) and the deposition flow rate (expressed in mass deposited per unit of time) can be varied simultaneously so as to obtain a constant mass deposited per unit of distance. Thus, the variations in the process do not induce any geometric modification of the object, that is to say that the variations in the manufacturing process do not disturb the dimensions of the manufactured object.

[0039] According to one embodiment, it is also possible to modify and / or accentuate the magnetic signature of the object by adapting the support 4 on which the object is formed. In particular, it is possible to provide a support having different portions with different thermal properties. The thermal properties can be, for example, a temperature, a thermal conductivity or even a thermal inertia. The support 4 can thus locally have different thicknesses and / or different heating means and / or materials.

[0040] These thermal properties of the support 4 impact the local cooling kinematics of the ferromagnetic material after it has been deposited, which also modifies its magnetic permeability. For example, a first portion of the support may have a higher temperature and a second portion of the support may have a lower temperature. The areas of the object manufactured above the first portion and above the second portion will thus have different magnetic permeability. It is possible to provide different supports to manufacture objects of identical appearance, so that they have different magnetic signatures.

[0041] According to another aspect of the invention, it is also possible to provide a step of smoothing a face of the object after it has been synthesized using the device 1. This face then comprises different zones, each having specific magnetic permeabilities. This smoothing can be obtained, for example, by milling a face of the object. The probe is intended to be applied against this face to detect local differences in magnetic permeability of the object. The advantage of smoothing a face of the object is that the probe can more easily be brought into contact with the object to read the magnetic signature. This eliminates the air effect and the disturbances linked to a potentially degraded surface state of the object, in particular linked to the superposition of different cords.

[0042] [Fig.2] illustrates, as an example, an object 9 of simple geometry manufactured by a additive manufacturing method according to the invention. During the manufacture of this object 9, different cords 10A, 10B, 10C were deposited successively while varying the process parameters as indicated above. Each cord forms an area of ​​the object 9 having a given magnetic permeability. For example, pauses of a few seconds during which the flow rate of ferromagnetic material was zero were planned during the manufacture of the object 9.

[0043] [Fig. 3] illustrates by way of example a block diagram of the manufacture of the object 9 according to a embodiment of the invention. In a first step El 1, a code is defined intended to form a magnetic signature of an object. Then, in a second step El2, said code is converted into process parameters for each zone zl, z2, ... zn of the object. Then, in a third step E13, the object is manufactured by additive manufacturing using the device 1 previously described by applying the process parameters defined during step El2. Step El3 comprises a number n of sub-steps E13.1 E13.2, ... E13.n each corresponding to the manufacture of a zone zl, z2, ... zn with the previously defined process parameters. Then, in a fourth step E14, a part of the object comprising the n zones zl, z2, ... zn to make it easier for a probe to read the code.

[0044] A probe 11 is intended to detect the local magnetic permeability of the object 9. The probe 11 comprises a coil 12 inside which a magnetic core 13 is arranged. Advantageously, the coil 12 and the core 13 are integrated into a small measuring head, of the order of a few millimeters in diameter, to carry out a magnetic permeability measurement with a high spatial resolution, for example a spatial resolution of the order of 1 mm. The probe 11 may further comprise a magnet 14 attached to the coil 12 to further improve the spatial resolution.

[0045] [Fig.4] illustrates an equivalent electrical diagram corresponding to the couple formed by the object 9 and the probe 11. The probe 11 can be modeled by three branches mounted in parallel. A first branch comprises a first capacitor CL. A second branch comprises a second capacitor C2. A third branch comprises a first impedance ZI and a first coil L1 assembled in series. Such an electrical assembly is intended to resonate for a given excitation frequency. Each zone of the object 9 can be modeled as an electrical assembly comprising a second coil L2 and a second impedance Z2 mounted in parallel.

[0046] To identify the object 9 by means of the probe 11, the probe 11 can be moved over the surface of the object. If necessary, the probe 11 can be moved along the smoothed surface so as to avoid an air effect. Then, for each area of ​​the object, for example for each cord of the object, a given magnetic permeability can be determined by means of the probe 11.

[0047] The determination of the magnetic permeability may comprise the calculation of a function establishing a link between a phase variation of the impedance Z2 of the probe 11 as a function of an excitation frequency.

[0048] The probe 11 thus makes it possible to reconstruct a magnetic code integrated into the part, and invisible to the naked eye. Once the part has been identified, it can be authenticated and traced.

[0049] Alternatively or in addition, the probe 11 can also be used for purposes other than the identification of the object 9. In particular, the probe 11 can be used to control the quality of the object 9. Indeed, since variations in the manufacturing process induce local modifications in the magnetic permeability of the object, said probe 11 can also be used to verify that the magnetic permeability of the object is indeed homogeneous, and therefore that the object has been manufactured without significant variation in the process parameters, in particular without interruption. This quality control can possibly be limited to the most sensitive areas of the object, for example to the areas of the object intended to undergo the greatest mechanical stresses.

[0050] Then, after identification of the object, it may be desirable to erase the signature magnetic field integrated into the object. This can be achieved for example by placing said object 9 in a sufficiently powerful magnetic field, and / or by heating said object 9, and / or by placing said object under mechanical stress. The invention therefore also makes it possible to provide an object whose identification code can be easily erased.

[0051] [Fig. 5] illustrates a second object 9' of geometric shape identical to the geometric shape of the object 9 previously described, called the first object 9, and shown schematically in [Fig. 2]. The second object 9' was also manufactured by additive manufacturing using the same additive manufacturing device 1 as the first object 9. The two objects 9 and 9' are therefore indistinguishable from each other to the naked eye. However, the object 9' was manufactured by applying manufacturing parameters different from those used for the manufacture of the first object 9.For example, the cords 10A', 10B', and 10C have different magnetic permeabilities than the cords 10A, 10B, 10C of the object 9. As a result, the magnetic signature of the second object 9' is different from the magnetic signature of the first object 9. Each of the two objects can thus be distinguished from the other object by identifying the magnetic signature using the probe 11.

[0052] [Fig.6] illustrates by way of example a block diagram for authentication of the object 9 according to an embodiment of the invention. In a first step E21, the object 9 is manufactured by a manufacturer according to the method previously described so as to integrate a magnetic signature into the object 9. In a second step E22, the manufacturer communicates a reference code as well as the location and / or a procedure for reading the magnetic signature of the object 9 to a recipient. This communication can be carried out before, after, or in parallel with the first step E21. Preferably, this communication is carried out independently of the dispatch of said object 9 from the manufacturer to the recipient. In a third step E23, the recipient identifies the object 9 by determining its magnetic signature. This third step comprises a number n of sub-steps E23.1, E23.2,... E23.n each corresponding to the measurement of the magnetic permeability of a zone z1, z2,... zn.In each sub-step, the probe 11 is positioned against the object 9 opposite the area under consideration based on the location and / or the reading procedure communicated by the manufacturer. Then, in a fourth step E24, the previously measured magnetic permeability values ​​are converted into a code. This code corresponds to the identification of the object. Then, in a fifth step E25, the detected code can be compared to the reference code provided by the manufacturer of the object to confirm the authenticity of the object.

Claims

Claims

1. Method for additive manufacturing of a first ferromagnetic object (9), characterized in that it comprises a step of varying at least one parameter of the manufacturing method to locally modify a magnetic permeability of said first object, to integrate a magnetic signature into said first object.

2. Manufacturing method according to the preceding claim, characterized in that said additive manufacturing method is of the arc-wire type.

3. Manufacturing method according to one of the preceding claims, characterized in that said variations of at least one parameter comprise: - a variation in the deposition temperature of a ferromagnetic material, and / or - a variation in the deposition speed of a ferromagnetic material, and / or - a variation in the deposition flow rate of a ferromagnetic material, and / or - a variation in the deposition trajectory of a ferromagnetic material, and / or - the projection of a cooling fluid.

4. Manufacturing method according to one of the preceding claims, characterized in that it comprises a variation in deposition speed and a variation in deposition flow rate of a ferromagnetic material, the deposition speed and the deposition flow rate being synchronized at each instant so as to obtain a constant deposit quantity.

5. Manufacturing method according to one of the preceding claims, characterized in that said first object (9) is manufactured by additive manufacturing on a support (4) comprising a first zone (10A) and a second zone (10B), the first zone having thermal properties different from the second zone.

6. Manufacturing method according to one of the preceding claims, characterized in that it then comprises a step of smoothing one face of said first object, said face comprising zones having different magnetic permeabilities.

7. A method of additive manufacturing a set of objects comprising a first object and at least one second object, each object of the set of objects being manufactured by a manufacturing method according to one of the preceding claims, each object of the set of objects comprising an identical geometric shape, at least one parameter of the manufacturing process of the second object being different from a manufacturing parameter of the first object so that the magnetic signature of the second object is different from the magnetic signature of the first object.

8. Ferromagnetic object (9) manufactured by an additive manufacturing method according to one of claims 1 to 6, said object comprising local variations in magnetic permeability forming a magnetic signature of said object.

9. A set of objects manufactured by an additive manufacturing method according to claim 7, each object of the set of objects comprising a different magnetic signature.

10. A method of identifying an object (9) manufactured by additive manufacturing according to claim 8, the identification method comprising the detection of local variations in magnetic permeability forming the magnetic signature of the object by means of a probe.

11. Identification method according to the preceding claim, characterized in that it comprises the calculation of a function establishing a link between a phase variation of an impedance of the probe as a function of an excitation frequency.

12. Identification method according to one of claims 10 or 11 characterized in that said probe (11) comprises a coil (12) provided with a magnetic core (13).

13. Identification method according to the preceding claim, characterized in that said probe (11) further comprises a magnet (14) attached to the coil (12).

14. Method for authenticating an object (9) comprising: - the manufacture by a manufacturer of said object by an additive manufacturing method according to one of claims 1 to 6, said object comprising local variations in magnetic permeability forming a magnetic signature of the object, and - the communication of a location of the magnetic signature on said object and / or of a procedure for reading the magnetic signature of the first person to a second person, then - the implementation of the method for identifying said object according to one of claims 10 to 13.

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