Improved device for additively manufacturing a part by means of powder bed fusion

Abstract

The invention relates to a device (1) for additively manufacturing a part by means of powder bed fusion, the device comprising: a build plate (10) which is capable of supporting the part during manufacturing thereof; a spreading device (20) which is capable of spreading the powder, in successive layers, on the build plate (10); and at least one laser or electron beam generator (30) which is capable of melting the successive layers of powder in a localised manner, the spreading device (20) comprising a plurality of movable spreading tools (22) which are arranged one behind the other in a circular train, each of the spreading tools (22) being capable of spreading the powder and of moving together with the other spreading tools (22) of the plurality of spreading tools (22), of diffusing a shielding gas and of recovering the shielding gas diffused by at least one of the other spreading tools (22) of the plurality of spreading tools (22).

Description

Description Title of the invention: improved device for the additive manufacturing of parts by powder bed fusion Technical Field

[0001] This presentation relates to a device for the additive manufacturing of parts, in particular by powder bed fusion, and a method using such a device. Prior art

[0002] It is now known, particularly in the aeronautics field, to use additive manufacturing methods for the production of certain parts with fine or complex geometry.

[0003] A classic example of additive manufacturing is the melting or sintering of powder particles using a high-energy beam. Examples of high-energy beams include laser beams and electron beams.

[0004] By "selective laser melting" (SLM), also known as the "Laser Beam Melting" (LBM) process, we mean a process whose main characteristics are recalled below, with reference to Figure 1 illustrating a conventional device for manufacturing parts by selective melting or selective sintering of powder beds using a laser beam.

[0005] A first layer 100a of powder of a material is deposited, for example using a spreading tool 200 (for example a roller or a scraper), on a construction plate 210 (this may be a plate alone or surmounted by a solid support, a part of another part or a support grid used to facilitate the construction of certain parts).

[0006] This powder is transferred from a feed bin 220 during a forward movement of the roller 200 then it is scraped, and possibly slightly compacted, during one (or more) return movement(s) of the roller 200. The powder is composed of metallic particles 110, for example comprising a nickel alloy. Excess powder is recovered in a recycling bin 230 located adjacent to the build bin 240 in which the build plate 210 moves vertically.

[0007] A generator 300 of a laser beam 310 is also used, and a control system 320 capable of directing this beam 310 onto any region of the construction plate 210 so as to scan any region of a previously deposited powder layer. The shaping of the laser beam 310 and the variation of its diameter on the focal plane are carried out respectively by means of a beam dilator or focusing system 330 and a “Beam Expander” 340, the assembly constituting the optical system.

[0008] Then, a region of this first layer 100a of powder is brought, by scanning with a laser beam 310, to a temperature higher than the melting temperature of this powder.

[0009] This type of additive manufacturing process can use any high-energy beam in place of the laser beam 310, including an electron beam, as long as the beam is energetic enough to melt the powder particles and some of the material the particles are resting on.

[0010] This beam scanning is carried out for example by a galvanometric head forming part of a control system 320. For example, this control system comprises at least one orientable mirror 350 on which the laser beam 310 is reflected before reaching a layer of powder, each point of the surface of which is always located at the same height relative to the focusing lens, contained in the focusing system 340, the angular position of this mirror being controlled by a galvanometric head so that the laser beam scans at least one region of the first layer of powder, and thus follows a pre-established part profile. To do this, the galvanometric head is controlled according to the information contained in the database of the computer tool used for the computer-aided design and manufacturing of the part to be manufactured.

[0011] Thus, the powder particles 110 of this region of the first layer 100a are melted and form a first element 120a in one piece, integral with the construction plate 210. At this stage, it is also possible to scan with the laser beam several independent regions of this first layer to form, after melting and solidification of the material, several first elements 120a separate from each other.

[0012] The build plate 210 is lowered by a height corresponding to the thickness of the first layer of powder 100a (20 to 100 μm and generally 30 to 50 μm).

[0013] A second layer 100b of powder is then deposited on the first layer 100a and on this first single-piece or consolidated element 120a, then a region of the second layer 10b which is located partially or completely above this first single-piece or consolidated element 120a in the case illustrated in FIG. 1 is heated by exposure to the laser beam 310, such that the powder particles of this region of the second layer 100b are melted with at least a portion of the element 120a and form a second single-piece or consolidated element 120b, the assembly of these two elements 120a and 120b forming, in the case illustrated in FIG. 1, a single-piece block.

[0014] Such an additive manufacturing technique therefore ensures excellent control of the geometry of the part to be manufactured and makes it possible to produce parts with great complexity.

[0015] In parallel with the layer-by-layer manufacturing of the part described above, a protective gas such as argon can be diffused over the layers of powder during melting, via a device that is independent and separate from the device described above. Such a gas makes it possible to protect the powder against the harmful action of compounds in the ambient air, and in particular to limit oxidation of the powder, which can harm the quality of the final part.

[0016] However, for the production of large parts, involving for example fusion surfaces greater than 1500 cm 2 , the performance of existing additive manufacturing devices may be limited. Furthermore, the fact Increasing the size of the build plate makes it more difficult, especially in the case of annular parts, to manage the flow of shielding gas, which further limits productivity.

[0017] There is therefore a real need for a device that can at least partially overcome the aforementioned drawbacks. Statement of the invention

[0018] The present disclosure relates to a device for the additive manufacturing of parts by powder bed fusion, comprising a construction plate capable of supporting the part during its manufacture, a spreading device capable of spreading the powder, in successive layers, on the construction plate, and at least one laser beam or electron generator capable of melting the successive layers of powder in a localized manner, the spreading device comprising a plurality of mobile spreading tools arranged one behind the other in a circular train, each of the spreading tools being capable of spreading the powder and moving jointly with the other spreading tools of the plurality of spreading tools, diffusing a protective gas, and recovering the protective gas diffused by at least one of the other spreading tools of the plurality of spreading tools.

[0019] It is understood that the spreading tools are arranged one behind the other such that each spreading tool is arranged between two other spreading tools. Furthermore, by “move jointly with the other tools” it is understood that each spreading tool moves at the same time as the other spreading tools of the plurality of spreading tools, that is to say following the same trajectory and preferably going at the same speed. It will be noted, however, that the spreading tools may not go at the same speed, this speed being able to vary.

[0020] Thus, during operation of the spreading device, each spreading tool moves jointly with the spreading tool preceding it and the spreading tool succeeding it, according to the direction of movement of the spreading tools.

[0021] Given this arrangement, it is possible to reduce the time interval between the spreading of two successive layers of powder on the plate construction. Furthermore, over a given time interval, the spreading device can spread a larger area of ​​powder, which is particularly advantageous for large parts. The circular train arrangement is also particularly suitable for large annular parts, involving, for example, an additive manufacturing device and an annular-shaped build plate. It is thus possible to efficiently manufacture such parts continuously. In other words, the device of the invention makes it possible to improve the yield and productivity during the additive manufacturing of parts by powder bed fusion.

[0022] Furthermore, the spreading device, and in particular the spreading tools, perform not only the spreading function, but also the function of managing the shielding gases, in particular the diffusion and recovery of these gases. This configuration makes it possible to control the shielding gas flows more efficiently, which is particularly advantageous in the context of the manufacture of large parts involving also large devices, and thus further improve the productivity and the quality of the material of the manufactured part.

[0023] In some embodiments, each of the spreading tools is capable of moving along a closed-loop trajectory.

[0024] In other words, each spreading tool returns to its starting point after completing its trajectory. This allows for continuous zone-based spreading of powder layers without downtime and without the need for return movements of the spreading tools, thus further improving productivity.

[0025] In some embodiments, the shielding gas comprises a neutral gas.

[0026] In some embodiments, the neutral gas is argon.

[0027] In some embodiments, each spreading tool includes at least one outlet nozzle for diffusing the shielding gas, and at least one inlet nozzle for recovering the shielding gas, the outlet nozzle of each spreading tool being oriented towards the inlet nozzle of the spreading tool arranged downstream, according to a direction of movement of the spreading tools.

[0028] In other words, each spreading tool can both inject a shielding gas towards the spreading tool arranged downstream of said spreading tool, and also recover the shielding gas injected by the spreading tool arranged upstream of said spreading tool. The presence of an outlet nozzle and an inlet nozzle on each spreading tool, oriented respectively towards the outlet nozzle and the inlet nozzle of the adjacent spreading tool, thus makes it possible to target and localize the diffusion zone of the shielding gas by each spreading tool, thereby improving the control of the shielding gas flows.

[0029] In some embodiments, each spreading tool is a scraper, a first face of the scraper comprising a plurality of outlet nozzles distributed along said first face, and a second face opposite the first face and comprising a plurality of inlet nozzles distributed along said second face.

[0030] The outlet and inlet nozzles are preferably distributed at regular intervals along the first and second faces of the scraper respectively. This arrangement makes it possible on the one hand to improve the efficiency of the diffusion of the protective gases on the powder layers, and on the other hand to facilitate the recovery of the gases diffused by a spreading tool, by the following spreading tool.

[0031] In some embodiments, the spreading device comprises N spreading tools, where N>2, the spreading tool N being capable of diffusing a shielding gas towards the spreading tool N+1, and of capturing a shielding gas diffused by the spreading tool N-1.

[0032] In other words, each spreading tool performs the same function, diffusing the shielding gases towards the spreading tool which follows it according to the direction of movement of the spreading tools, and recovering the shielding gases diffused by the spreading tool which precedes it.

[0033] In some embodiments, the spreading device comprises between six and twenty spreading tools, preferably twelve spreading tools.

[0034] In some embodiments, the part to be manufactured is an annular casing of an aircraft engine, such as an airplane or a helicopter.

[0035] The present disclosure also relates to a method for additive manufacturing of a part by powder bed fusion using a device according to any one of the preceding embodiments, the method comprising the steps of: - provision of a digital model of the part to be manufactured, - the manufacturing of the part layer by layer on the basis of the digital model, comprising the spreading of successive layers of powder by the spreading device on the construction plate, the local melting of said layers of powder by the laser beam or electron generator - the diffusion of a shielding gas, and the capture of said shielding gas, by means of the spreading tools of the spreading device. Brief description of the drawings

[0036] The invention and its advantages will be better understood upon reading the detailed description given below of different embodiments of the invention given as non-limiting examples. This description refers to the appended pages of figures, in which:

[0037] [Fig. 1] Figure 1 represents an overview of an additive manufacturing device by selective fusion of powder beds according to the prior art,

[0038] [Fig. 2] Figure 2 schematically represents a device for the additive manufacturing of parts by powder bed fusion according to a first embodiment of the invention,

[0039] [Fig. 3] Figure 3 schematically represents, in a top view, a spreading device of the device of Figure 2,

[0040] [Fig. 4] Figure 4 schematically represents a detailed and partial view of the spreading device of Figure 3, Description of the embodiments

[0041] An embodiment of the invention will be described in the remainder of the description with reference to Figures 2 to 4.

[0042] Figure 2 schematically represents a device 1 for additive manufacturing of parts by powder bed fusion. The elements common to the device according to the prior art described previously with reference to Figure 1 are not shown and will not be described again.

[0043] The device 1 comprises a construction plate 10 shown in a top view. The construction plate 10 has, in this example, an axisymmetric annular shape around a central axis A, suitable for manufacturing parts such as turbine rings or any annular parts such as annular casings, bearing supports or flanges. The construction plate 10 is virtually divided into several sectors 12, in this example twelve sectors 12, corresponding to the sectors in which portions of the part are manufactured, that is to say sectors in which the successive layers of powder are melted.

[0044] The device 1 also comprises a spreading device 20 for spreading the successive layers of powder on the build plate 10. The spreading device 20 comprises a gas diffusion means 21 and a plurality of spreading tools 22 (schematically represented in FIG. 1 by an assembly 22 and described in detail below), the gas diffusion means 21 making it possible to supply the spreading tools 22 with protective gas intended to protect the layers of powder during their melting.

[0045] The device 1 further comprises a laser beam generator 30. In this embodiment, the laser beam generator 30 is configured so as to generate a plurality of laser beams 31, preferably as many laser beams as sectors 12 of the build plate 10, in this example twelve laser beams 31 (only two beams 31 are shown in FIG. 2). It is therefore understood that a laser beam 31 is allocated to each sector 12 and intended to locally melt the successive layers of powder in this sector. Alternatively, the laser beams 31 may be electron beams.

[0046] Figure 3 schematically represents, in detail, the spreading device 20, in a top view. The spreading device 20 comprises a plurality of spreading tools 22, in this example twelve. The spreading tools 22 are typically longitudinal scrapers of square section. This shape is however not limiting, the scrapers can be longitudinal of rectangular, polygonal or even circular section.

[0047] The scrapers 22 are arranged one behind the other in a circle. In other words, each scraper 22 forms a predetermined angle with the adjacent scraper 22, such that the scrapers 22 are distributed at regular intervals around the central axis A.

[0048] The scrapers 22 are thus arranged so as to form a circular train, concentric with the construction plate 10, and moving as a unit around the central axis A in a given direction, for example in the counterclockwise direction represented by the curved arrows in Figure 3.

[0049] By "moving as a unit" is meant that each scraper 22 moves together with the scraper 22 that precedes or succeeds it, that is, preferably at the same speed and along the same trajectory. This trajectory is circular, so as to form a closed-loop trajectory. In other words, a given scraper 22 returns to its initial position after completing one complete revolution. It should be noted, however, that the scrapers 22 may not move at the same speed as each other. For example, the speed of movement of each scraper 22 may oscillate, such that two adjacent scrapers 22 may move towards each other temporarily and then move away, and so on.

[0050] The scrapers 22 of the spreading device 20 are arranged above the construction plate 10, such that during the additive manufacturing of the part, each scraper 22 is able to spread a layer of powder in a given sector 12, then in the following sector 12 after rotation of the spreading device 20, and so on.

[0051] It will be noted that the device 1 may also comprise feed trays (not shown) adjacent to each sector 12, such that each scraper 22 transfers the powder from the feed tray to the sector 12 and then spreads the powder over said sector 12, in the manner described previously with reference to FIG. 1.

[0052] Thus, over a given time interval, a layer of powder can be spread jointly over all sectors 12 of the build plate 10 by all of the scrapers 22, which makes it possible to improve yield and productivity.

[0053] Furthermore, after the passage of a scraper 22 over a given sector 12, and before the arrival of the next scraper 22, the laser beam 31 dedicated to said sector 12 carries out a scan in the area of ​​said sector 12, in order to melt in a localized manner the layer of powder which has just been spread by the scraper 22.

[0054] Furthermore, during the rotation of the spreading device 20, each scraper 22 is capable of diffusing a protective gas, intended to protect the layer of powder during its melting on a given sector 12. Such a protective gas typically comprises argon, and makes it possible to protect the material constituting the powder against oxidation. The gas flow lines G are represented by arrows in Figures 3 and 4.

[0055] Figure 4 shows a detailed view of the spreading device 20 of Figure 3, in which only three scrapers 22 are shown. Each scraper 22 includes a plurality of outlet nozzles 24 and inlet nozzles 26.

[0056] The outlet nozzles 24 (in this non-limiting example, six outlet nozzles 24) are distributed longitudinally along a first face 22a of the scraper 22, preferably at regular intervals. Each outlet nozzle 24 makes it possible to deliver a gas flow G in the direction of the following scraper 22, according to the direction of movement of the scrapers 22, the gas flow G diffusing over the powder bed of the corresponding sector 12.

[0057] The inlet nozzles 26 (in this non-limiting example, six inlet nozzles 26) are distributed longitudinally along a second face 22b of the scraper 22, opposite the first face 22a and preferably at regular intervals. Each inlet nozzle 26 makes it possible to capture and recover the gas flow G coming from the previous scraper 22 after its passage over the corresponding sector 12.

[0058] Although the outlet nozzles 24 and the inlet nozzles 26 are shown in relief in Figure 4, this shape is not limiting, the nozzles inlet and outlet which may be simple orifices formed on the faces 22a, 22b of each scraper 22.

[0059] Given this arrangement, the outlet nozzles 24 of each scraper 22 are oriented towards the inlet nozzles 26 of the following scraper 22, according to the direction of movement of the scrapers 22. Conversely, the inlet nozzles 26 of each scraper 22 are oriented towards the outlet nozzles 24 of the preceding scraper 22, according to the direction of movement of the scrapers 22.

[0060] Thus, a scraper 22 (N) diffuses gas flows G towards the following scraper 22 (N+1), the latter recovering said gas flows G coming from the scraper 22 (N). Similarly, the scraper 22N recovers the gas flows G coming from the previous scraper 22 (N-1). It will be noted that in this example comprising twelve scrapers 22, and taking into account the closed-loop arrangement of the scrapers 22, the scraper numbered “12” is arranged between the scraper numbered “11” and the scraper numbered “1”.

[0061] Preferably, the first faces 22a, and therefore the outlet nozzles 24, are oriented so as to inject the gas flows G in a direction opposite to the direction of rotation of the spreading device 20. In other words, on each scraper 22, the first face 22a comprising the outlet nozzles 24 is a downstream face in the direction of movement of the scraper 22, and the second face 22b comprising the inlet nozzles 26 is an upstream face.

[0062] Thus, in Figure 3 and Figure 4, the spreading device 20 rotates counterclockwise, and the gas flows G are oriented clockwise (arrows G in the figures). Each scraper 22 thus leaves in its wake the protective gas diffused by the outlet nozzles 24. This configuration makes it possible to take advantage of the inertia effect of the scrapers 22, and to improve the efficiency of the diffusion of the protective gas on the powder layers, while facilitating the recovery of the gas. It will be noted, however, that this arrangement is not limiting, the position of the outlet nozzles 24 and the inlet nozzles 26 being able to be reversed, without departing from the scope of the invention, so that the gas flows G are ejected in the direction of rotation of the spreading device 20.

[0063] Each scraper 22 being capable of both diffusing and capturing a protective gas, it is thus possible to diffuse the protective gas over local and targeted areas, corresponding to each sector 12.

[0064] Preferably, each scraper 22 comprises internal circuits (not shown) for the flow of the protective gas, these internal circuits being supplied by the gas diffusion means 21. In particular, each scraper 22 may comprise an inlet circuit and a return circuit distinct from each other. The gas diffusion means 21 supplies the inlet circuit with protective gas, the latter then being ejected by the outlet nozzles 24. The return circuit collects the protective gas recovered by the inlet nozzles 26, the collected gas then being able to be rerouted to the gas diffusion means 21.

[0065] Figures 2 to 4 represent an embodiment in which the scrapers are arranged so as to form a circular train. This arrangement is however not limiting, other types of arrangement of the scrapers 22 can be envisaged without departing from the scope of the invention.

[0066] A method of additive manufacturing of a part by powder bed fusion using a device 1 as described above comprises on the one hand the provision of a digital model of the part to be manufactured, and on the other hand the actual manufacturing of the part layer by layer on the basis of the digital model.

[0067] The digital model may be a digital production file produced using suitable software. This file typically includes a division into slices of given thickness produced by CAD (computer-aided design) of an object. The production file also includes all the necessary instructions, such as the trajectories of the laser beams 31, so that the device 1 can manufacture the object, slice by slice.

[0068] Furthermore, the actual manufacturing of the part comprises the spreading of successive layers of powder by the spreading device 20, and the local and targeted melting of said layers of powder by the laser or electron beam generator 30. In particular, the laser beams 31 selectively scan certain areas of the powder bed in each sector 12, corresponding to a slice of the part to be manufactured. The circular zones F in broken lines in figure 2 represent the local zones covered by each of the laser beams 31.

[0069] The scanning pattern of each laser beam 31, as well as all the parameters linked to the scanning of the laser, in particular the power of the laser, the scanning speed, the spacing between two passes of the laser, are dictated to the device 1 by the aforementioned production file.

[0070] The actual manufacturing further comprises the diffusion of the protective gas, and the capture of said protective gas, by means of the gas diffusion means 21 and the scrapers 22 of the spreading device 20.

[0071] Although the present invention has been described with reference to specific exemplary embodiments, it is obvious that modifications and changes may be made to these examples without departing from the general scope of the invention as defined by the claims. In particular, individual features of the various illustrated / mentioned embodiments may be combined in additional embodiments. Therefore, the description and drawings should be considered in an illustrative rather than restrictive sense.

[0072] It is also obvious that all the characteristics described with reference to a method are transposable, alone or in combination, to a device, and conversely, all the characteristics described with reference to a device are transposable, alone or in combination, to a method.

Claims

Claims

1. Device (1) for the additive manufacturing of a part by powder bed fusion, comprising a construction plate (10) capable of supporting the part during its manufacture, a spreading device (20) capable of spreading the powder, in successive layers, on the construction plate (10), and at least one laser beam or electron generator (30) capable of melting the successive layers of powder in a localized manner, the spreading device (20) comprising a plurality of mobile spreading tools (22) arranged one behind the other in a circular train, each of the spreading tools (22) being capable of spreading the powder and moving jointly with the other spreading tools (22) of the plurality of spreading tools (22), diffusing a protective gas, and recovering the protective gas diffused by at least one of the other spreading tools (22) of the plurality of spreading tools (22).

2. Device (1) according to claim 1, wherein each of the spreading tools (22) is capable of moving along a closed-loop trajectory.

3. Device (1) according to claim 1 or 2, wherein the shielding gas comprises a neutral gas.

4. Device (1) according to claim 3, wherein the neutral gas is argon.

5. Device (1) according to any one of claims 1 to 4, wherein each spreading tool (22) comprises at least one outlet nozzle (24) for diffusing the shielding gas, and at least one inlet nozzle (26) for recovering the shielding gas, the outlet nozzle (24) of each spreading tool (22) being oriented towards the inlet nozzle (26) of the tool spreading (22) arranged downstream, in a direction of movement of the spreading tools.

6. Device (1) according to claim 5, wherein each spreading tool (22) is a scraper, a first face (22a) of the scraper comprising a plurality of outlet nozzles (24) distributed along said first face (22a), and a second face (22b) opposite the first face (22a) and comprising a plurality of inlet nozzles (26) distributed along said second face (22b).

7. Device (1) according to any one of claims 1 to 6, wherein the spreading device (20) comprises N spreading tools (22), where N>2, the spreading tool (22) N being capable of diffusing a protective gas towards the spreading tool (22) N+1, and of capturing a protective gas diffused by the spreading tool (22) N1.

8. Device (1) according to any one of claims 1 to 7, wherein the spreading device (20) comprises between six and twenty spreading tools (22), preferably twelve spreading tools (22).

9. A method of additive manufacturing of a part by powder bed fusion using a device (1) according to any one of the preceding claims, the method comprising the steps of: - provision of a digital model of the part to be manufactured, - manufacturing the part layer by layer on the basis of the digital model, comprising spreading successive layers of powder by the spreading device (1) on the construction plate (10), local melting of said layers of powder by the laser beam or electron generator (30), - the diffusion of a protective gas, and the capture of said protective gas, by means of the spreading tools (22) of the spreading device (20).

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