Additive manufacturing method

Abstract

Method for additive manufacturing by laser fusion of a powder jet onto a substrate, the powder jet comprising at least a first material (A) and a second material (B) according to a set total composition by weight.

Description

Description Title: ADDITIVE MANUFACTURING PROCESS technical field

[0001] This description relates to an additive manufacturing process and an additive manufacturing device. Previous technique

[0002] In this text, "additive manufacturing process" means both an initial manufacturing of part 40, and a repair of part 40 already manufactured (by any technique whatsoever) and of which an area is rebuilt by "additive manufacturing", that is to say by an addition of material from metal powder which can be carried out by a laser melting process of a powder jet or "LMD" as below.

[0003] An additive manufacturing process such as Laser Metal Deposition (LMD) involves manufacturing a three-dimensional part 40 using a device 10 shown in Figure 1. The device 10 comprises a nozzle 20 from which a jet of metal powder is ejected, and a laser beam to fuse the powder onto a substrate. A succession of metal layers can thus be formed and bonded to the substrate.

[0004] The device 10 may include one or more reservoirs, each containing a metal powder. In the example shown in Figure 1, the device 10 includes a first reservoir 12 containing a metal powder of a first material A and a second reservoir 14 containing a metal powder of a second material B different from the first material A.

[0005] The powder jet can therefore consist of either a single powder from one of the reservoirs or a mixture of powders from several reservoirs. Thus, each metallic layer can comprise 100% of the first material A, 100% of the second material B, or a mixture of the first material A and the second material B.

[0006] As shown in Figure 2a, the manufacturing process can be of the "multi-material" type in that the part 40 obtained comprises a first part 42 adjacent to a second part 44, the first part 42 comprising 100% of the first material A and the second part 44 comprising 100% of the second material B. Alternatively, as shown in Figure 2b, the manufacturing process can be of the "gradient material" type in that the part 40 obtained comprises a first part 42 comprising 100% of the first material A and a second part 44 comprising 100% of the second material B and an intermediate part 46 between the first part 42 and the second part 44 which comprises a mixture of the first material A and the second material B. In particular, the intermediate part 46 includes a composition gradient between the first material A and the second material B (or, in other words, the intermediate part 46 can form a "gradual" transition between the first part 42 and the second part 44).

[0007] The current manufacturing process, as described above, has the drawback of not allowing for the detection of any discrepancy between the composition of the powder from the mixer and the desired composition. Such a discrepancy is indeed detrimental because the resulting part 40 is not made from the desired alloy grade. However, the thermal and mechanical performance of the resulting part 40 depends directly on the composition of the material from which the part 40 is made.

[0008] Furthermore, when the powder composition from the mixer does not match the desired composition, the manufacturing parameters, such as the laser power or the nozzle travel speed 20, may not be suitable for the desired part 40. This can result in manufacturing defects such as unstable deposition, increased porosity in the resulting part 40, or incorrect dimensions of the part 40.

[0009] Finally, a poor composition of the material in which part 40 is made is difficult to identify once part 40 is manufactured. Summary

[0010] An additive manufacturing process is proposed by melting a powder jet onto a substrate, the powder jet comprising at least a first material and a second material with a specified total mass composition, the process comprising a manufacturing phase which includes the following steps: - deliver at least a first powder of the first material into a mixer according to a first mass flow rate; - deliver at least a second powder of the second material into the mixer according to a second mass flow rate; - mix the first powder and the second powder in the mixer; - convey the mixture of the first powder and the second powder to a deposition nozzle; - take a portion of the mixture of the first powder and the second powder which is conveyed to the deposition nozzle; - determine a mass proportion of the first material and the second material in the mixture; - compare the mass proportion of the first material and the second material in the mixture relative to the total mass composition setpoint of the powder jet; - modify at least one of the first mass flow rate and the second mass flow rate in case of a discrepancy between the mass proportion of the first material and the second material in the mixture and the total mass composition setpoint of the powder jet.

[0011] This process allows for the detection of the mass composition of the mixture (i.e., the mass proportion of the first and second materials in the mixture), its comparison to the target total mass composition of the powder stream, and, if necessary, the adjustment of the mass flow rate of the first and second powders in the mixer to obtain a defined mass composition of the mixture. Thus, the process makes it possible to limit, or even prevent, the production of a part in an undesired alloy grade. Consequently, the manufactured part exhibits improved quality and performance.

[0012] Furthermore, determining the mass proportion of the first and second materials after mixing the first and second powders allows for the detection of any deviation in mass composition. This deviation could be due to an anomaly during the introduction of the first and / or second powders into the mixer, as well as an anomaly during the mixing process within the mixer. Thus, the process ensures that the mixture arriving at the dispensing nozzle has the target total mass composition, especially since the sources of variation in mass composition between the mixer and the dispensing nozzle are limited.

[0013] Finally, the mass composition of the mixture is checked and corrected during the part manufacturing process. This means that the mass composition is checked and corrected concurrently, thus avoiding any reduction in process productivity.

[0014] Powder jet melting can be achieved using a (high energy) laser or an electron beam (also known as "Electron Beam Melting" or EBM).

[0015] A delay in the construction process can also be implemented when a discrepancy is detected between the mass composition of the mixture and the target total mass composition. This delay allows the adjusted mass flow rates of the first and second materials to stabilize and the mixture to be re-homogenized in the mixer before production continues.

[0016] Determining the mass proportion of the first material and the second material in the mixture may include: - measure the mass flow rate of the portion of the mixture sampled through a measuring orifice which has a predetermined diameter; - identify the mass proportion of the first material and the second material in the mixture from a comparison with a database which includes mass flow values ​​through an orifice of the same diameter as the measuring orifice for a powder comprising the first material and the second material whose mass composition varies between 100% first material and 100% second material.

[0017] This method for determining the mass proportions of the first and second materials in a mixture has the advantage of being compatible with a wide range of materials. Furthermore, it allows for a rapid determination of these mass proportions. Finally, the measurement of the mass flow rate of the sampled portion of the mixture through the measuring orifice and the identification of the mass proportions of the first and second materials in the mixture in a database can be performed automatically, for example, by a programmable logic controller (PLC).

[0018] The database may include the mass flow rate value through an orifice of the same diameter as the measuring orifice for a powder comprising the first material and the second material for each mass composition comprising x% of first material and (100-x)% of second material with x between 0 and 100 in increments of 10%, preferably 5%, preferably still 1%.

[0019] The process may include a calibration phase to establish the database, the calibration phase comprising the steps: i° providing a calibration powder comprising at least the first material and the second material in a known mass composition of the first material and the second material; ii° measuring a mass flow rate of the calibration powder through a calibration orifice which has a diameter identical to that of the measurement orifice; iii° repeating steps i° and ii° varying the mass composition of the calibration powder between 100% of the first material and 100% of the second material.

[0020] Steps i° and ii° can be repeated for each mass composition of the calibration powder comprising x% of first material and (100-x)% of second material with x between 0 and 100 in increments of 10%, preferably 5%, preferably 1%.

[0021] The diameter of the calibration orifice and the diameter of the measuring orifice can be adapted to the density of the mixed materials. The diameter of the calibration orifice and The diameter of the measuring orifice can be chosen so that the relative difference between the mass flow rate of the calibration powder whose mass composition comprises 100% of the first powder and the mass flow rate of the calibration powder whose mass composition comprises 100% of the second powder is greater than or equal to 10%. This allows for a more precise and faster determination of the mass proportion of the first and second materials in the mixture during the manufacturing phase.

[0022] The first mass flow rate and / or the second mass flow rate can be modified so as to maintain a constant mass flow rate of the powder jet.

[0023] The mixture can be conveyed to the deposition nozzle via a transport gas stream and wherein the process includes a step which includes the separation of the portion taken from the mixture from the transport gas.

[0024] From another perspective, an additive manufacturing system is proposed, comprising: - a first reservoir containing a first powder of a first material; - a second reservoir containing a second powder of a second material; - a mixer in communication with the first tank and the second tank, the mixer being adapted to form a mixture of the first powder and the second powder; - means to control the supply of first powder and second powder respectively according to a first mass flow rate and a second mass flow rate in the mixer; - a main conduit connecting the mixer to a deposition nozzle and through which the mixture is conveyed to the deposition nozzle; - a sampling conduit in communication with the main conduit, the sampling conduit being adapted to sample a portion of the mixture conveyed to the deposition nozzle; - means of determination to measure the mass proportion of the first material and the second material in the part taken from the mixture; - means of comparison to compare the mass proportion of first material and second material in the mixture to a set total mass composition and means of modification to modify the first mass flow rate and / or the second mass flow rate in case of deviation between the mass proportion of first material and second material in the mixture and the set total mass composition.

[0025] The means for determining the mass proportion of the first material and the second material in the mixture may include means for measuring a mass flow rate of the portion taken from the mixture through a measuring orifice which has a predetermined diameter and a database which includes the mass flow rate values ​​through an orifice of the same diameter as the measuring orifice for a powder comprising the first material and the second material whose mass composition varies between 100% first material and 100% second material.

[0026] The means for measuring the mass flow rate of the portion taken from the mixture through the measuring orifice may include an element comprising the measuring orifice through which the portion taken from the mixture can flow and a weighing system.

[0027] The device may include means for generating and / or managing a flow of transport gas to convey the mixture from the mixer to the deposition nozzle, the device further including means for separating the portion taken from the mixture from the transport gas. Brief description of the drawings

[0028] Other features, details, and advantages will become apparent upon reading the detailed description below and analyzing the attached drawings, on which:

[0029] Figure 1 schematically represents an additive manufacturing device according to the state of the art;

[0030] Figure 2 includes figures 2a and 2b, each schematically representing a multi-material or material gradient part manufactured by the device in figure 1;

[0031] Figure 3 is a functional diagram of a manufacturing phase of an additive manufacturing process according to the present description;

[0032] Figure 4 schematically represents a manufacturing device for implementing the process of Figure 3.

[0033] Figure 5 is a functional diagram of a calibration phase of the process in Figure 3;

[0034] Figure 6 is a graph which represents the mass flow rate evolution through an orifice of predetermined diameter of a powder comprising a first material and a second material whose mass composition varies between 100% of the first material and 100% of the second material;

[0035] [Fig. 7] is a graph that represents the evolution of the mass flow rate through an orifice of a powder comprising a first material and a second material according to different known mass compositions as a function of the diameter of the orifice. Description of the implementation methods

[0036] Reference is now made to Figures 3 and 4. Figure 3 shows a functional diagram of a manufacturing phase 100 of an additive manufacturing process involving the fusion of a powder jet onto a substrate. Figure 4 schematically represents an additive manufacturing device 10 adapted for implementing manufacturing phase 100 of the process shown in Figure 3.

[0037] The powder bed process here comprises a first material A and a second material B according to a specified total mass composition. This specified total mass composition corresponds to the desired alloy grade from which the part is to be manufactured. Generally, the powder bed can comprise k materials, where k is an integer greater than or equal to 2. Thus, according to undescribed alternatives, the powder bed can comprise more than two materials; for example, it can comprise three or four materials. Therefore, the process can be of the "multi-material" type or of the "material gradient" type, as described above.

[0038] Manufacturing phase 100 comprises a first step 110. The first step 110 of manufacturing phase 100 involves adding a first powder of the first material A to a mixer 16 at a first mass flow rate Q1. In other words, the first powder has a mass composition comprising 100% of the first material A. The first step 110 also involves adding a second powder of the second material B to the mixer 16 at a second mass flow rate Q2. In other words, the second powder has a mass composition comprising 100% of the second material B. The addition of the first and second powders can be carried out simultaneously in the mixer 16. The first mass flow rate Q1 and the second mass flow rate Q2 are determined to obtain the target total mass composition.

[0039] To this end, the device 10 includes a first reservoir 12 containing the first powder of the first material A and a second reservoir 14 containing the second powder of the second material B. Generally, the device 10 can include k reservoirs, where k is an integer greater than or equal to 2, with each reservoir containing a specific material. The device 10 also includes the mixer 16, which is in (fluid) communication with the first reservoir 12 and the second reservoir 14. Furthermore, the device 10 includes control means for controlling the supply of the first powder. powder and second powder respectively according to the first mass flow rate Q1 and the second mass flow rate Q2.

[0040] Manufacturing phase 100 includes a second step 120. The second step 120 of manufacturing phase 100 includes the mixing of the first powder and the second powder in the mixer 16. For this purpose, the mixer 16 is adapted to form a mixture, preferably homogeneous, of the first powder and the second powder.

[0041] The manufacturing phase 100 includes a third step 130. This third step 130 of the manufacturing phase 100 comprises conveying the mixture of the first and second powders to a dispensing nozzle 20 of the device 10. For this purpose, the device 10 includes a main conduit 18 connecting the mixer 16 to the dispensing nozzle 20, through which the mixture is conveyed to the dispensing nozzle 20. In particular, the mixture can be conveyed to the dispensing nozzle 20 via a transport gas flow. The device 10 may therefore further include means for generating the transport gas flow in the main conduit 18. The gas flow can, for example, be generated in the main conduit 18 directly downstream of the mixer. In other words, the gas flow can for example be generated in an end portion of the main conduit 18 which is connected to the mixer 16. The deposition nozzle 20 generates the powder jet from the mixture.The nozzle 20 also incorporates a laser to heat the substrate and generate a localized melt pool. The powder is directly injected into the melt pool, where it melts and bonds to the substrate. The nozzle can also be moved, allowing for the formation of successive layers comprising the first material A and / or the second material B.

[0042] The manufacturing phase 100 includes a fourth step 140. This fourth step 140 of the manufacturing phase 100 involves sampling a portion of the mixture of the first and second powders, which is conveyed to the deposition nozzle 20. In other words, the mixture is sampled at the main conduit. To this end, the device 10 includes a sampling conduit 22 in (fluid) communication with the main conduit 18, the sampling conduit 22 being adapted to sample a portion of the mixture conveyed to the deposition nozzle 20. The fourth step 140 may also include separating the sampled portion of the mixture from the transport gas by means of separation 24. Preferably, as shown in Figure 4, the sampling can be carried out as close as possible to, or even in the immediate vicinity of, the deposition nozzle 20.The communication between the sampling line 22 and the main line 18 can therefore be closer to the dispensing nozzle 20 than to the mixer 16. For example, the sampling line 22 can be connected to a portion of the end of the main line 18 that is connected to the dispensing nozzle. Indeed, some. Variations in the mass proportions of the different materials in the mixture may occur between the outlet of the mixer 16 and the dispensing nozzle 20. Therefore, by sampling the mixture as close as possible to the dispensing nozzle 20, it is ensured that the steps described below are carried out based on the mixture as it is ejected from the dispensing head. The main conduit 18 may have an orifice into which one end of the sampling conduit is inserted. The orifice in the main conduit may have dimensions, preferably adjustable, adapted to sample a predetermined quantity or a predetermined flow rate of the mixture passing through the main conduit 18.

[0043] Manufacturing phase 100 includes a fifth step 150. This fifth step 150 of manufacturing phase 100 involves determining the mass proportion of the first material A and the second material B in the mixture. The device 10 includes means 26 for determining the mass proportion of the first material A and the second material B in the portion taken from the mixture.

[0044] First, determining the mass proportion of the first material A and the second material B in the mixture involves measuring the mass flow rate of the portion of the mixture drawn through a measuring orifice of a predetermined diameter. For this purpose, the determination means 26 include means for measuring the mass flow rate of the portion of the mixture drawn through the measuring orifice. These means comprise an element presenting the measuring orifice through which the portion of the mixture can flow, and a weighing system. Thus, measuring the mass of the portion of the mixture that has flowed (under the effect of gravity) through the measuring orifice over a known period of time allows the mass flow rate of the portion of the mixture drawn through the measuring orifice to be determined.

[0045] Next, determining the mass proportion of the first material A and the second material B in the mixture involves identifying their mass proportions from a database (or nomogram) of determination methods. The database includes mass flow rate values ​​through an orifice with the same diameter as the measuring orifice for a powder comprising the first material A and the second material B, with a mass composition ranging from 100% first material A to 100% second material B. This method for determining the mass proportion of the first material A and the second material B in the mixture has the advantage of being compatible with a wide range of materials. Furthermore, it allows for a rapid determination of the mass proportion of the first material A and the second material B in the mixture.Finally, the mass flow rate of the portion of the mixture sampled through the measuring orifice was measured, and the mass proportion of the first material A and the other material was identified. second material B in the mixture in the database can be done automatically, i.e. by a machine for example.

[0046] The database can include the mass flow rate value through an orifice of the same diameter as the measuring orifice for a powder comprising first material A and second material B for each mass composition comprising x% of first material A and (100-x)% of second material B, with x ranging from 0 to 100 in increments of 10%, preferably 5%, and preferably 1%. In particular, the smaller the percentage increment of the database, the more accurate the determination of the mass proportions of first material A and second material B in the mixture.

[0047] Figure 6 is a graph illustrating the database which includes the mass flow rate value through an orifice of the same diameter as the measuring orifice of a powder comprising the first material A and the second material B for each mass composition comprising x% of first material A and (100-x)% of second material B with x varying between 0 and 100 in an increment of 10%, i.e. for the following mass compositions: 100%A; 90%A-10%B; 80%A-20%B; 70%A-30%B; 40%A-60%B; 50%A-50%B; 40%A-60%B; 30%A-70%B; 20%A-80%B; 10%A-90%B; 100%B. In the example shown in Figure 6, the mass flow rate changes linearly for a variation in mass composition between 100%A and 100%B. However, it is possible that the mass flow rate may change non-linearly for a variation in mass composition between 100%A and 100%B.

[0048] The process also includes a calibration phase 200 during which the database is established. Figure 5 shows a functional diagram of the calibration phase 200 of the process.

[0049] The calibration phase 200 includes a first step 210. The first step 210 of the calibration phase 200 includes the provision of a calibration powder comprising at least the first material A and the second material B according to a known mass composition of the first material A and the second material B.

[0050] The calibration phase 200 includes a second step 220. The second step 220 of the calibration phase 200 includes the measurement of a mass flow rate of the calibration powder through a calibration orifice which has a diameter identical to that of the measurement orifice.

[0051] The first step 210 and the second step 220 are then repeated, varying the mass composition of the calibration powder between 100% of the first material A and 100% of the second material B. The first step 210 and the second step 220 can be repeated for each mass composition of the calibration powder comprising x% of first material A and (100-x)% of second material B, with x varying between 0 and 100 in increments of 10%, preferably 5%, and preferably 1%. In the database example represented by the graph in Figure 6, the first step 210 and the second step 220 are repeated 10 times.

[0052] Referring to Figure 7, the diameter of the calibration orifice and the diameter of the measuring orifice can be chosen to be greater than or equal to a threshold diameter Ds for which the relative difference between the mass flow rate of the calibration powder whose mass composition comprises 100% of the first powder and the mass flow rate of the calibration powder whose mass composition comprises 100% of the second powder is greater than or equal to 10%. This allows for a more precise and faster determination of the mass proportion of first material A and second material B in the mixture during manufacturing step 100.

[0053] Manufacturing phase 100 includes a sixth step 160. The sixth step 160 of manufacturing phase 100 includes comparing the mass proportion of the first material A and the second material B in the mixture with the set total mass composition of the powder jet and modifying at least one of the first mass flow rate Q1 and the second mass flow rate Q2 in case of a deviation between the mass proportion of the first material A and the second material B in the mixture and the set total mass composition of the powder jet.

[0054] To this end, the device 10 includes comparison means 28 for comparing the mass proportions of first material A and second material B in the mixture to the set total mass composition, and modification means 30 for modifying the first mass flow rate Q1 and / or the second mass flow rate Q2 in case of a deviation between the mass proportions of first material A and second material B in the mixture and the set total mass composition. The comparison means 28 and modification means 30 may, in particular, communicate with the control means. The comparison means 28 and modification means 30 may communicate with the determination means 26. Any wired or wireless (i.e., remote) communication method may be used.The comparison means 28 and modification means 30 can receive data or a signal indicating the mass proportion of first material A and second material B in the mixture determined by the determination means 26. The comparison means 28 and modification means 30 can send a control signal to the control means.

[0055] This process allows for the detection of a mixture mass composition that does not correspond to the target total mass composition of the powder jet, and for the adjustment of the mass flow rates of the first and second powders in the mixer 16 to obtain the correct mixture mass composition. Thus, the process makes it possible to limit, or even prevent, the production of a part in an undesired alloy grade. Consequently, the manufactured part exhibits improved quality and performance.

[0056] Furthermore, determining the mass proportion of the first material A and the second material B after mixing the first and second powders makes it possible to detect a deviation in mass composition that would be due to an anomaly during the introduction of the first and / or second powders into the mixer 16, but also to an anomaly during the mixing in the mixer 16. Thus, the process makes it possible to ensure that the mixture arriving at the deposition nozzle 20 has the total mass composition set, especially since the sources of variations in mass composition between the mixer 16 and the deposition nozzle 20 are limited, or even non-existent.

[0057] Finally, the mass composition of the mixture is checked and corrected during the part manufacturing process. This means that the mass composition is checked and corrected concurrently, thus avoiding any reduction in process productivity.

[0058] Preferably, in the event of a change in the first mass flow rate Q1 and / or the second mass flow rate Q2, the first mass flow rate Q1 and / or the second mass flow rate Q2 can be changed so as to maintain a constant total mass flow rate of the powder jet.

[0059] In a particular embodiment, a temporary shutdown of the laser can also be provided in response to a change in the first mass flow rate Q1 and / or the second mass flow rate Q2 if a discrepancy is detected between the mass composition of the mixture and the target total mass composition. This allows the mixture to be re-homogenized in the mixer 16 before manufacturing continues. The laser can then be reactivated.

Claims

Claims

1. Additive manufacturing method by melting a powder jet onto a substrate, the powder jet comprising at least a first material (A) and a second material (B) according to a set total mass composition, the method comprising a manufacturing phase (100) which comprises the steps: - delivering at least a first powder of the first material (A) into a mixer (16) according to a first mass flow rate (Q1); - delivering at least a second powder of the second material (B) into the mixer (16) according to a second mass flow rate (Q2); - mixing the first powder and the second powder in the mixer (16); - conveying the mixture of the first powder and the second powder to a deposition nozzle (20); - taking a portion of the mixture of the first powder and the second powder which is conveyed to the deposition nozzle (20); - determine a mass proportion of the first material (A) and the second material (B) in the mixture; - compare the mass proportion of the first material (A) and the second material (B) in the mixture with respect to the total mass composition setpoint of the powder jet; - modify at least one of the first mass flow rate (Q1) and the second mass flow rate (Q2) in the event of a difference between the mass proportion of the first material (A) and the second material (B) in the mixture and the total mass composition setpoint of the powder jet.

2. Additive manufacturing method according to the preceding claim, in which the determination of the mass proportion of the first material (A) and the second material (B) in the mixture comprises: - measure the mass flow rate of the sampled portion of the mixture through a measuring orifice which has a predetermined diameter; - identifying the mass proportion of the first material (A) and the second material (B) in the mixture from a comparison with a database which includes the mass flow rate values ​​through an orifice of diameter identical to that of the measuring orifice for a powder comprising the first material (A) and the second material (B) whose mass composition varies between 100% of first material (A) and 100% of second material (B).

3. Additive manufacturing method according to the preceding claim, the method comprising a calibration phase (200) for establishing the database, the calibration phase (200) comprising the steps: i° providing a calibration powder comprising at least the first material (A) and the second material (B) according to a known mass composition of the first material (A) and the second material (B); ii° measuring a mass flow rate of a flow of the calibration powder through a calibration orifice which has a diameter identical to that of the measuring orifice; iii° repeating steps i° and ii° by varying the mass composition of the calibration powder between 100% of first material (A) and 100% of second material (B).

4. A method according to any preceding claim, wherein the first mass flow rate (A) and / or the second mass flow rate (B) are varied so as to maintain a constant total mass flow rate of the powder jet.

5. A manufacturing method according to any preceding claim, wherein the mixture is supplied to the deposition nozzle (20) via a transport gas stream and wherein the method comprises a step which comprises separating the withdrawn portion of the mixture from the transport gas.

6. Additive manufacturing device (10) comprising: - a first reservoir (12) comprising a first powder of a first material (A); - a second reservoir (14) comprising a second powder of a second material (B); - a mixer (16) in communication with the first reservoir (12) and the second reservoir (14), the mixer being adapted to form a mixture of the first powder and the second powder; - control means for controlling a supply of first powder and second powder respectively according to a first mass flow rate (Q1) and a second mass flow rate (Q2) in the mixer (16); - a main conduit (18) connecting the mixer (16) to a deposition nozzle (20) and through which the mixture is conveyed to the deposition nozzle (20); - a sampling conduit (22) in communication with the main conduit (18), the sampling conduit (22) being adapted to sample a portion of the mixture conveyed to the deposition nozzle (20); - determination means (26) for determining a mass proportion of the first material and the second material in the sampled part of the mixture; - comparison means (28) for comparing the mass proportion of first material and second material in the mixture with a set total mass composition and modification means (30) for modifying the first mass flow rate and / or the second mass flow rate in the event of a difference between the mass proportion of first material and second material in the mixture and the set total mass composition.

7. Device (10) according to the preceding claim, wherein the determining means (26) for determining a mass proportion of the first material (A) and the second material (B) in the mixture comprise means for measuring a mass flow rate of the sampled portion of the mixture through a measuring orifice which has a predetermined diameter and a database which comprises the mass flow rate values ​​through an orifice of diameter identical to that of the measuring orifice for a powder comprising the first material (A) and the second material (B) whose mass composition varies between 100% of first material (A) and 100% of second material (B).

8. A device (10) according to claim 6 or 7, the device comprising means for generating a flow of transport gas for conveying the mixture from the mixer to the deposition nozzle (20), the device further comprising separation means (24) for separating the withdrawn portion of the mixture from the transport gas.

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