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 the additive manufacturing of a ferromagnetic object. The invention also relates to a ferromagnetic object obtained by such a manufacturing method. The invention further relates to a method for identifying such an object. Prior art

[0002] Additive manufacturing has revolutionized the manufacturing paradigm in recent years by offering the possibility of creating parts with highly complex shapes, even those impossible to obtain using conventional processes, without tooling and in very short lead times. Among the various additive manufacturing techniques are wire arc additive manufacturing (WAAM), which belongs to the family of direct energy deposition (DED). According to ASTM F 279-12A (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 material feed.

[0003] Objects manufactured by additive manufacturing can be used in all types of industries. Since manufacturing 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 considerably. This depends in particular on the manufacturer's control 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. However, this means of identification is too easily falsified. Moreover, integrating an identification number onto 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 object of the invention is to provide an additive manufacturing process and a ferromagnetic object obtained by such a process which remedies the above disadvantages and improves the processes and objects manufactured by additive manufacturing known in the prior art.

[0006] The object of the invention is in particular to provide an additive manufacturing process for an object enabling reliable identification and authentication of said object. Summary of the invention

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

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

[0009] Said variations of at least one parameter may include: - a variation in the deposition temperature of a ferromagnetic material, and / or - a variation in the deposition rate of a ferromagnetic material, and / or - a variation in the deposition 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 process may include a variation in the deposition speed and a variation in the deposition rate of a ferromagnetic material, the deposition speed and the deposition rate being synchronized at every instant so as to obtain a constant quantity of deposit.

[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 thermal properties different from the second zone.

[0012] The manufacturing process may then include a step of smoothing one face of said first object, said face comprising areas exhibiting different magnetic permeabilities.

[0013] The invention also relates to an additive manufacturing process for a set of objects comprising a first object and at least one second object, each object in the set of objects being manufactured by a manufacturing process as defined above, each object in 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.

[0014] The invention also relates to a ferromagnetic object manufactured by an additive manufacturing process 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 process as defined above, each object in the set of objects comprising 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 include calculating a function establishing a link between a phase variation of a probe impedance as a function of an excitation frequency.

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

[0019] Said probe may further include 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 - the communication of 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 identification process for said object as defined previously. Presentation of the figures

[0021] These objects, features and advantages of the present invention will be described in detail in the following description of a particular embodiment, given by way of non-limiting example, with reference to the accompanying figures, among which:

[0022] Fig. 1 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] The [Fig.3] is a synoptic diagram of the manufacture of an object according to an embodiment of the invention.

[0025] Fig. 4 is a view of an equivalent electrical diagram of said object and of 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 in Fig. 2.

[0027] The [Fig.6] is a synoptic diagram for identifying an object according to an embodiment of the invention. Detailed description

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

[0029] More specifically, device 1 is a wire-arc type additive manufacturing device. Device 1 comprises a robot 2 equipped with a torch 3 for additive manufacturing on a support 4. The support 4 is mounted on a movement means 5 for controlling the position of the support 4 in space. The robot 2 is connected to a generator 6, which is itself connected to a gas reservoir 7. Finally, 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 wire is heated to melt it, and / or - the deposition rate, that is to say the quantity of ferromagnetic material deposited per unit of time, and / or - the deposition trajectory, that is to say the direction in which the support 4 moves thanks to the means of movement 5, and / or - the deposition speed, that is to say the speed of movement of the support 4 relative to the torch 3.

[0031] In addition, the device 1 may also include a means for projecting a cooling fluid such as air or oil to cool the temperature of the material after it has been deposited onto the object being manufactured. Advantageously, the control unit also allows control of 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 modifying certain parameters of the manufacturing process, particularly the parameter(s) affecting the temperature of the ferromagnetic material at the moment it is deposited onto the manufactured object, leads to a modification of the material's microstructure, and therefore to a local modification of the magnetic permeability (expressed in Henrys per meter) of said object. It is thus possible to manufacture an object comprising different zones, each with a specific magnetic permeability. These different zones form an invisible code that allows the object to be identified.

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

[0034] This results in a magnetic signature integrated into the object that 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 a greater number of zones.

[0036] The local modification of the material's magnetic permeability is achieved without the insertion of any element or component specifically designed for this purpose. Thus, the manufacturing process remains simple. The strength and / or dimensions of the object produced are not significantly affected.

[0037] These zones can be grouped on the same face or in the same region of the object. These zones can be grouped in an easily accessible region and / or in a region designed to withstand less mechanical stress. Indeed, any mechanical stress the object may be subjected to could modify, or even erase, its mechanical signature. The different areas of the object where magnetic permeability is modified can also be kept secret to make any attempt to reproduce the magnetic signature even more difficult.

[0038] Advantageously, during the manufacturing process, the deposition rate (expressed in units of distance per unit of time) and the deposition 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, variations in the process do not induce any geometric modification of the object; that is, variations in the manufacturing process do not disrupt the dimensions of the manufactured object.

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

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

[0041] According to another aspect of the invention, a smoothing step can also be provided for one face of the object after it has been synthesized using device 1. This face then comprises different zones, each with specific magnetic permeabilities. This smoothing can be achieved, for example, by milling one face of the object. The probe is intended to be applied against this face to detect local differences in the object's magnetic permeability. The advantage of smoothing one 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 gap effect and disturbances related to a potentially degraded surface condition of the object, particularly those caused by the superposition of different cords.

[0042] Figure 2 illustrates, by way of example, an object 9 of simple geometry manufactured by a Additive manufacturing process according to the invention. During the fabrication of this object 9, different beads 10A, 10B, 10C were deposited successively while varying process parameters as described above. Each bead forms an area of ​​the object 9 with a given magnetic permeability. For example, pauses of a few seconds during which the flow of ferromagnetic material was zero were scheduled during the fabrication of the object 9.

[0043] Figure 3 illustrates, by way of example, a synoptic diagram of the manufacture of object 9 according to a embodiment of the invention. In a first step E1, a code is defined to form a magnetic signature of an object. Then, in a second step E12, said code is converted into process parameters for each zone z1, z2,... zn of the object. Then, in a third step E13, the object is manufactured by Additive manufacturing is performed using the device 1 described previously, applying the process parameters defined in step El2. Step El3 comprises n substeps E13.1, E13.2, ..., E13.n, each corresponding to the fabrication of a zone z1, z2, ..., zn with the previously defined process parameters. Then, in a fourth step E14, a portion of the object, including the n zones z1, z2, ..., zn, can be smoothed to facilitate code reading by a probe.

[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, on the order of a few millimeters in diameter, to perform a magnetic permeability measurement with high spatial resolution, for example, a spatial resolution on 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] Figure 4 illustrates an equivalent electrical diagram corresponding to the torque formed by object 9 and probe 11. Probe 11 can be modeled by three branches connected in parallel. The first branch comprises a first capacitor CL. The second branch comprises a second capacitor C2. The third branch comprises a first impedance Z1 and a first inductor L1 connected in series. Such an electrical circuit is designed to resonate at a given excitation frequency. Each area of ​​object 9 can be modeled as an electrical circuit comprising a second inductor L2 and a second impedance Z2 connected in parallel.

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

[0047] The determination of magnetic permeability may include 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 is identified, it can be authenticated and traced.

[0049] Alternatively or in addition, the probe 11 can also be used for purposes other than identifying the object 9. In particular, the probe 11 can be used to check the quality of the object 9. Indeed, since variations in the manufacturing process induce local changes in the magnetic permeability of the object, the probe 11 can also be used to verify that the permeability The magnetic field of the object is homogeneous, indicating that the object was manufactured without significant variations in process parameters, particularly without interruptions. This quality control can potentially be limited to the most sensitive areas of the object, for example, those areas intended to withstand the greatest mechanical stresses.

[0050] Next, after the object has been identified, it may be desirable to erase the magnetic signature embedded in the object. This can be achieved, for example, by placing said object 9 in a sufficiently strong magnetic field, and / or by heating said object 9, and / or by subjecting said object to mechanical stress. The invention therefore also makes it possible to provide an object whose identification code can be easily erased.

[0051] Figure 5 illustrates a second object 9' with the same geometric shape as the previously described object 9, referred to as the first object 9, and shown schematically in Figure 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, object 9' was manufactured using different manufacturing parameters than those used to manufacture the first object 9. For example, cords 10A', 10B', and 10C have different magnetic permeabilities than cords 10A, 10B, and 10C of 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 therefore be distinguished from the other by identifying the magnetic signature using probe 11.

[0052] Figure 6 illustrates, by way of example, a flowchart for authenticating object 9 according to one embodiment of the invention. In a first step E21, object 9 is manufactured by a manufacturer according to the previously described process so as to integrate a magnetic signature into 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 object 9 to a recipient. This communication may be carried out before, after, or in parallel with the first step E21. Preferably, this communication is carried out independently of the shipment of said object 9 from the manufacturer to the recipient. In a third step E23, the recipient identifies object 9 by determining its magnetic signature. This third step comprises n substeps E23.1, E23.2, ... E23.n, each corresponding to the measurement of the magnetic permeability of a zone z1, z2, ... zn.During each sub-step, the probe 11 is positioned against the object 9 opposite the area under consideration, based on the location and / or reading procedure provided 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 object's identification. Next, in a fifth step E25, the detected code can be compared to the reference code provided by the object's manufacturer to confirm the object's authenticity.

Claims

Demands

1. Additive manufacturing process of 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, to integrate a magnetic signature into said first object, said variations of at least one parameter comprising: - a variation of the deposition temperature of a ferromagnetic material, and / or - a variation of the deposition speed of a ferromagnetic material, and / or - a variation of the deposition rate of a ferromagnetic material, and / or - a variation of the deposition trajectory of a ferromagnetic material, and / or - the projection of a cooling fluid.

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

3. A manufacturing method according to any one of the preceding claims, characterized in that it comprises a variation in the deposition speed and a variation in the deposition rate of a ferromagnetic material, the deposition speed and the deposition rate being synchronized at every instant so as to obtain a constant quantity of deposit.

4. A manufacturing method according to any 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.

5. A manufacturing method according to any one of the preceding claims, characterized in that it then comprises a step of smoothing one face of said first object, said face comprising areas having different magnetic permeabilities.

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

7. Ferromagnetic object (9) manufactured by an additive manufacturing process according to any one of claims 1 to 5, said object comprising local variations in magnetic permeability forming a magnetic signature of said object.

8. Set of objects manufactured by an additive manufacturing process according to claim 6, each object in the set of objects comprising a different magnetic signature.

9. Method for identifying an object (9) manufactured by additive manufacturing according to claim 7, the identification method comprising the detection of local variations in magnetic permeability forming the magnetic signature of the object by means of a probe.

10. 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 a probe impedance as a function of an excitation frequency.

11. Identification method according to any one of claims 9 or 10 characterized in that said probe (11) comprises a coil (12) provided with a magnetic core (13).

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

13. A method for authenticating an object (9) comprising: - the manufacture by a manufacturer of said object by an additive manufacturing process according to any one of claims 1 to 5, 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, and then - the implementation of the method for identifying said object according to any one of claims 9 to 12.

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