Method for depowdering a part obtained by additive manufacturing, and device for implementing same

Abstract

Disclosed is a method for depowdering a part (3) produced by additive manufacturing, the part comprising a cavity (15) to be depowdered, the cavity comprising a first opening (151), the method comprising steps of: a) pressurising the cavity by injecting a gas up to a predetermined maximum pressure through the first opening; b) suddenly releasing the pressure within the cavity by quickly switching from the predetermined maximum pressure to a purge pressure.

Description

DESCRIPTION TITLE: METHOD FOR DEPRECIATING DUST FROM A PART OBTAINED BY ADDITIVE MANUFACTURING AND IMPLEMENTATION DEVICE TECHNICAL FIELD OF THE INVENTION

[0001] The invention relates to the field of cleaning parts produced by additive manufacturing. In particular, the invention relates to a method for depowdering such a part thus obtained. PRIOR TECHNOLOGY

[0002] Depowdering involves removing material powder inevitably contained in one or more cavities of a part produced by an additive manufacturing process using a powder bed, such as the LBM process (Laser Beam Melting). This process is also known as Selective Laser Melting (or SLM).

[0003] Currently, a depowdering process for removing or evacuating residual powder from the cavities of the resulting part involves inverting the part while vibrating it using various vibration modes / systems or shock devices. In most cases, this depowdering process allows the residual powder to essentially "flow" out of the part by gravity.

[0004] However, this method is insufficient for removing powder from more complex parts manufactured using additive manufacturing, such as parts containing long, thin channels running within them. These parts only partially remove powder, resulting in plugs of material powder that are impossible to clear, even with repeated blowing or rinsing through the channel inlets and outlets. This is the case, for example, with an aluminum heat exchanger manufactured using additive manufacturing that includes multiple small-diameter (4 mm) pipes. 2 for example) and long (1000 mm for example). Another possible case is the presence of a blind pipe (a single opening) which does not allow for the creation of a gas flow through it.

[0005] Documents JP 2003225948 and US 2020 / 376766 describe methods and devices for depowdering residual powder within the cavities of parts produced by a powder bed additive manufacturing process. STATEMENT OF INVENTION

[0006] One object of the invention is to provide a method, as well as an implementation device, for efficiently depowdering such a part obtained by additive manufacturing and having a cavity.

[0007] To this end, the invention provides a method for depowdering a part made by additive manufacturing, the part having a cavity to be depowdered, the cavity having a first opening, the method comprising the steps of: a) Pressurizing the cavity by injecting a gas up to a predetermined maximum pressure through the first opening; b) Rapidly releasing the pressure within the cavity by a quick change from the predetermined maximum pressure to a purge pressure.

[0008] Advantageously, but optionally, the depowdering process according to the invention has at least one of the following technical characteristics: steps a) and b) are repeated until the cavity is completely depowdered; the pressurization is quasi-static; the cavity forms a circuit within the part; the purge pressure is equal to, slightly above, or slightly below ambient pressure; the cavity is blind; the cavity includes a second opening distinct from the first opening.

[0009] The invention also provides for a device for depowdering a part made by additive manufacturing, the part having a cavity to be depowdered, in which the device includes an interface with the cavity, a gas injection pump in fluidic connection with the interface and a purge in fluidic connection with the interface, the device being arranged so as to implement a depowdering process having at least one of the preceding technical characteristics.

[0010] Advantageously, but optionally, the dust removal device for a part according to the invention has at least one of the following technical features: the device includes a flow regulator between the pump and the interface; the pump and the purge are in fluidic communication with the first opening; the pump is in fluidic communication with the first opening, and the purge is in fluidic communication with the second opening; the purge includes a purge body, a piston mounted to slide within the purge body between purge closed and purge open positions, a return spring mounted between the piston and the purge body, and a magnet arranged to move the piston within the purge body.The purge mechanism comprises a purge body, a piston mounted to slide within the purge body between purge closed and purge open positions, a return spring mounted between the piston and the purge body, and a pneumatic control arranged to move the piston within the purge body. The return spring is calibrated to maintain the piston in the purge closed position under the purge pressure. Since the part has at least two cavities to be depowdered, the interface is arranged to communicate with at least two cavities simultaneously. BRIEF DESCRIPTION OF THE FIGURES

[0011] Other features and advantages of the invention will become apparent from the following description of an embodiment of the invention. See the attached drawings:

[0012] [Fig.1] is a perspective and schematic view of an additive manufacturing installation for producing a part to be depowdered by a depowdering process according to the invention;

[0013] [Fig.2] is a schematic view of a first embodiment of a dust removal device according to the invention interfaced with a blind cavity of a part made by additive manufacturing;

[0014] [Fig. 3] is a schematic view of a second embodiment of a powder removal device according to the invention interfaced with a through-cavity of a part produced by additive manufacturing; and,

[0015] [Fig.4] a chronogram illustrating the use of a depowdering process according to the invention which can be implemented by the depowdering devices of figures 2 and 3;

[0016] [Fig. 5] is a schematic view of an embodiment of purging the dust removal devices of Figures 2 and 3; and,

[0017] [Fig. 6] is a schematic view of the second embodiment of a depowdering device according to the invention interfaced with several through cavities of a part made by additive manufacturing.

[0018] For clarity, identical or similar elements are identified by the same reference symbols throughout the figures. DETAILED DESCRIPTION OF AN IMPLEMENTATION METHOD

[0019] With reference to figure 1, we will describe an installation 30 enabling the production of a part 3 comprising a cavity by an additive manufacturing process on a powder bed already known in itself.

[0020] As a reminder, the additive manufacturing process consists of creating complex three-dimensional parts by fusing layers of powder. Various additive manufacturing techniques are possible. In the context of this invention, additive manufacturing is selected from the group comprising selective laser melting (SLM), electron beam melting (EBM), direct laser additive construction (CLAD), electron beam additive manufacturing (EBAM), and laser metal deposition (LMD).

[0021] In particular, powder bed additive manufacturing is carried out using the selective laser melting (SLM) technique. This involves spreading powder layer by layer using a scraper that determines the required amount and thickness of powder. A laser then fuses each layer of powder to form the part.

[0022] Powder bed fusion of part 3 is performed using a setup 30 as shown in Figure 1. This setup is a selective laser melting (SLM) setup. The setup 30 includes a first feed tank 31 containing a powder 32 of material and a build platform 33 on which part 3 is produced. The setup 30 also includes a scanning element 34 for transferring a quantity of powder 32 from the first feed tank 31 onto the build platform 33. The scanning element 34 also determines the quantity and thickness of the powder according to a control signal. Advantageously, but not exclusively, the build platform 33 is movable along a vertical translation Z within a second tank 35 and forms the movable bottom of this second tank 35.The first feed tank 31 also includes a movable bottom 36 moving vertically upwards along the Z-axis as the powder 32 is transferred onto the manufacturing support 33. The installation 30. The system also includes a laser beam generation element 37 for melting the powder used to produce part 3. This laser beam generation element 37 is coupled to means 38 for directing the laser beam 40, particularly towards the build platform 33. The means 38 for directing the laser beam 40 generated by the generation element 37 include first and second mirrors. The system 30 further includes a third recycling tank 39 for recycling unused or unmelted powder. The process consists of manufacturing part 3 by layering powder from the first feed tank 31, which is transferred to the build platform 33. These powder layers are then melted one after another by the laser beam 40 moving across the surface of each layer.

[0023] Such a manufacturing process makes it possible to produce complex parts which may include cavities of more or less complex shapes in which powder may be present and difficult to remove by current depowdering techniques.

[0024] We will now describe, with reference to Figure 2, a first embodiment of a dust removal device 1 according to the invention. Part 3, produced by an additive manufacturing technique as previously described, has a cavity 15, which is blind in this instance. The cavity 15 has a first opening 151 and extends to a bottom 152. By way of illustration, the cavity 15 is here a long, narrow-section conduit forming a circuit within part 3. This type of cavity is found in parts 3 that form the heat exchanger.

[0025] To remove dust from the blind cavity 15, the dust removal device 1 according to the invention comprises an interface 13 arranged to cooperate fluidly with the first opening 151 of the cavity 15, in a sealed manner. The dust removal device 1 according to the invention further comprises a gas injection pump 10 in fluidic connection with the interface 13. The injection pump 10 allows the injection (F1) of a gas, for example ambient air or another gas, into the cavity 15. The dust removal device 1 according to the invention comprises A flow regulator 11 is positioned between the injection pump 10 and the interface 13. The flow regulator 11 controls the gas injection supplied by the injection pump 10, up to a predetermined maximum pressure Pmax. Furthermore, the dust removal device 1 according to the invention includes a purge valve 12 in fluidic connection with the interface 13. The purge valve 12 allows the gas injected up to the maximum pressure Pmax to be evacuated (F2) into the cavity 15. The injection (F1) and evacuation (F2) of the injected gas are carried out here through the first opening 151 of the blind cavity 15.

[0026] With reference to Figure 3, we will describe a second embodiment of the dust removal device 1' according to the invention. Here, the dust removal device 1' according to the invention is an adaptation of the dust removal device 1 according to the invention previously described for a cavity 16 of part 3 having a first 151 and a second 162 opening. The cavity 16 is a through cavity within part 3, extending between the first opening 151 and the second opening 162, forming a circuit within part 3. To remove dust from the cavity 16, the dust removal device 1' according to the invention includes a first interface 13a cooperating fluidically with the first opening 151, preferably in a sealed manner. The dust removal device 1' according to the invention includes the injection pump 10 in fluidic connection to the first interface 13a.The dust removal device 1' according to the invention further comprises the flow regulator 11 positioned between the injection pump 10 and the first interface 13a. At the level of the second opening 162, the dust removal device 1' according to the invention comprises a second interface 13b cooperating fluidly with said second opening 162 of the cavity 16.

[0027] In the case where part 3 has several cavities 15', 16', as illustrated in Figure 6, the first interface 13a cooperates fluidly with the first openings 151 of the cavities 15', 16'. Similarly, the second interface 13b cooperates fluidly with the second openings 162 of the cavities 15' and 16'. Thus, the dust removal device 1' according to the invention can remove dust from both cavities 15' and 16' simultaneously. By extension, the dust removal device 1' according to the invention can remove dust from more than two cavities simultaneously, if part 3 has more than two cavities, by adapting the interfaces 13a and 13b. applies, mutatis mutandis, to multiple blind cavities and to interface 13 of the dust removal device 1.

[0028] The dust removal device 1 according to the invention and the dust removal device 1' according to the invention can form a single dust removal device. Furthermore, the dust removal device 1 according to the invention and the dust removal device 1' according to the invention each comprise a control unit 2 for controlling the injection pump 10 and / or the flow regulator 11 and / or the purge 12.

[0029] Now, with reference to Figure 5, we will describe an embodiment of the purge 12 equipping the dust removal device 1 according to the invention or the dust removal device l' according to the invention which have just been previously described.

[0030] The purge 12 comprises a purge body 121 having at one lower end an opening 123 allowing a fluidic connection with the interface 13, 13b of the dust removal device according to the invention. The purge body 121 further includes discharge ports 124. Within the purge body 121, the purge valve 12 includes a piston 122 that slides freely between a closed position, where the head of the piston 122 rests against a sealing gasket 128 mounted inside the purge body 121 around the opening 123 to seal the latter, and an open position, where the head of the piston 122 is away from the opening 123. The purge valve 12 includes an internal magnet 125 mounted integrally on the head of the piston 122, and an external magnet 126 mounted integrally on a rod of the piston 122, outside the purge body 121.At one end, here the upper end, the bleed valve 12 includes a control magnet 127 arranged to cooperate magnetically with the internal magnet 125 and the external magnet 126. Furthermore, the bleed valve 12 includes a return spring 129 for the piston 122 to its closed position. In an alternative embodiment, the external magnet 126, the internal magnet 125, and the control magnet 127 are replaced by a pneumatic control to move the piston head 122 between the open and closed positions.

[0031] We will now describe a powder removal process 20 according to the invention for optimally removing powder from parts 3 having cavities 15, 16, 15', 16' and manufactured by a powder bed additive manufacturing process. The description of the powder removal process 20 according to the invention will be given with reference to Figure 4.

[0032] In a first step, the depowdering process according to the invention pressurizes the cavity 15, 16, 15', 16' of the part 3 by injecting a gas through the first opening 151 until a predetermined maximum pressure Pmax is reached within the cavity 15, 16, 15', 16'. This pressurization 21 by gas injection is a quasi-static pressurization: it is carried out slowly so as not to displace any powder 31 present within the cavity 15, 16, 15', 16'.

[0033] In a second step, the depowdering process according to the invention performs a sudden pressure release 22 within the cavity 15, 16, 15', 16' of the part 3 by rapidly reducing the pressure from the predetermined maximum pressure Pmax to a purge pressure P1. The purge pressure P1 is, for example, equal to or slightly higher than the ambient pressure Patm. In an alternative embodiment, the purge pressure P1 is slightly lower than the ambient pressure Patm in order to create a vacuum within the cavity 15, 16, 15', 16' to increase the efficiency of the depowdering process according to the invention. A "sudden pressure release" is understood to mean a pressure release that occurs in a very short period of time compared to the time taken for the pressure increase 21 in the preceding step.Such a sudden release 22 allows for the production of a violent movement of gas then under pressure within the cavity 15,16,15',16' and thus carries away any powder residue 31 possibly present in said cavity 15,16,15',16'. .

[0034] The two previous steps are repeated until the depowdering of cavity 15,16,15',16' is complete.

[0035] In one embodiment, the depowdering process according to the invention has an "alternating" operation. Once the second step described above has been carried out, the depowdering process according to The invention involves aspirating gas from the cavity 15, 16, 15', 16' at a slow flow rate to avoid drawing in any remaining powder 31 present within the cavity. The depowdering process according to the invention then resumes at the first step, as described in the preceding paragraph. This allows for savings in the amount of gas used for depowdering.

[0036] In view of the chronogram of figure 4 and a pressure curve 25 shown, the pressurization 21 starts from the purge pressure P1, at point A. The quasi-static pressure rise takes place up to points B, C where the pressure within the cavity 15,16 is equal to a predetermined maximum pressure Pmax.

[0037] Once point C is reached, the depowdering process 20 according to the invention performs the sudden release 22. During this sudden release 22, the pressure within the cavity 15,16 drops abruptly (point D) then slows down (point E) until the pressure within the cavity 15,16 returns to the purge pressure P1 (point F).

[0038] Then the depowdering process 20 according to the invention repeats steps 21,22 according to the same chronogram.

[0039] In parallel, Figure 4 shows an inlet flow curve 26 and an outlet flow curve 27. The inlet flow curve 26 corresponds to the evolution of the injection (F1) when the depowdering process 20 according to the invention is implemented. Similarly, the outlet flow curve 27 corresponds to the evolution of the discharge (F2). Compared to the pressure curve 25, the flow curve 26 shows a relatively low flow rate controlled by the flow regulator 11, allowing for a quasi-static pressure increase. As for the outlet flow curve 27, it appears when the vent 12 is opened and illustrates the sudden pressure drop 22. The discharge flow rate starts from 0 when the vent 12 is opened, rises very rapidly to a high maximum flow rate vertically above point D on the pressure curve 25, and then falls back to 0 when the vent 12 is closed, vertically above point F.It should be noted that a low incoming flow rate continues, as pump 10 continues to operate. This high flow rate obtained during the sudden expansion 22 allows for the production of a violent movement of gas then under pressure within. the cavity 15,16 and thus carried away the powder residues 31 possibly present in said cavity 15,16.

[0040] The illustrative timing diagram in Figure 4 is obtained with a purge 12 of Figure 5 described previously. At point A, as described previously, pressurization 21 begins by gas injection and slow pressure increase (up to point B) because the piston 122 is in contact with the sealing gasket 128, blocking the orifice 123, the external magnet 126 being magnetically attracted by the control magnet 127 and thus locking the purge 12.

[0041] At point B, the maximum pressure Pmax is reached within cavity 15,16.

[0042] At point C, the sudden release 22 begins by triggering the purge 12 the pressure within the cavity 15,16 exceeds a holding force of the external magnet 126 magnetically attracted by the control magnet 127.

[0043] At point C, a significant flow F2 of gas suddenly escapes through the opening 123 and then the purge ports 124 of the purge 12, with a maximum purge flow rate being reached at point D, when the purge 12 is fully opened with the piston 122 held in the open position by the internal magnet 125 which is magnetically attracted by the control magnet 127.

[0044] From point E, the piston 122 returns to the closed position by means of the return spring 129 until the purge pressure P1, the external magnet 126 again magnetically attracted by the control magnet 127, locks the cavity 15,16 (point F) and allows a new pressurization 21.

[0045] In an alternative embodiment of the purge valve 12, the internal magnet 125, external magnet 126, and control magnet 127 are replaced by a pneumatic control that moves the piston head 122 between the open and closed positions. The previous operation remains valid, mutatis mutandis.

[0046] The depowdering process 20 according to the invention, as well as the depowdering devices 1,1' according to the invention previously described, apply to the depowdering of parts 3 such as a turbomachine element, including a heat exchanger or a turbine blade or injectors, hydraulic blocks, nozzles.

[0047] Naturally, the invention described above is by way of example. It is understood that a person skilled in the art is capable of carrying out different embodiments of the invention without departing from its scope.

[0048] It is emphasized that all features, as they are apparent to a person skilled in the art from this description, the drawings and the attached claims, even if in practice they have only been described in relation to other specific features, both individually and in any combinations, may be combined with other features or groups of features disclosed herein, provided that this has not been expressly excluded or that technical circumstances render such combinations impossible or meaningless.

Claims

CLAIMS 1. A method for depowdering a part (3) produced by additive manufacturing, the part having a cavity (15, 16, 15', 16') to be depowdered, the cavity having a first opening (151), the method comprising the steps of: a) Quasi-static pressurization of the cavity by injecting a gas to a predetermined maximum pressure through the first opening, the pressurization being slow so as not to displace any powder within the cavity; b) Abrupt pressure release within the cavity by a rapid change from the predetermined maximum pressure to a purge pressure.

2. A method according to claim 1, wherein steps a) and b) are repeated until the cavity is completely depowdered.

3. A method according to any one of claims 1 to 2, wherein the cavity forms a circuit within the part. 4.A method according to any one of claims 1 to 3, wherein the purge pressure is equal to ambient pressure or slightly above or slightly below ambient pressure.

5. A method according to any one of claims 1 to 4, wherein the cavity (15) is blind.

6. A method according to any one of claims 1 to 4, wherein the cavity comprises a second opening (162) distinct from the first opening.

7. A device for depowdering (1, 1') a part (3) produced by additive manufacturing, the part having a cavity (15, 16, 15', 16') to be depowdered, wherein the device comprises an interface (13, 13a, 13b) with the cavity, a gas injection pump (10) in fluidic connection with the interface, and a 8. Device according to claim 7, wherein the device comprises a flow regulator (11) between the pump and the interface.

9. Device according to any one of claims 7 to 8 and method according to any one of claims 1 to 5, wherein the pump and the purge are in fluidic communication with the first opening.

10. Device according to any one of claims 7 to 8 and method according to claim 6, wherein the pump is in fluidic communication with the first opening, and the purge is in fluidic communication with the second opening. 11.A device according to any one of claims 7 to 10, wherein the purge comprises a purge body (121), a piston (122) mounted to slide within the purge body between purge closed and purge open positions, a return spring (129) mounted between the piston and the purge body, and a magnet (125, 126, 127) arranged to move the piston within the purge body.

12. A device according to any one of claims 7 to 10, wherein the purge comprises a purge body, a piston mounted to slide within the purge body between purge closed and purge open positions, a return spring mounted between the piston and the purge body, and a pneumatic control arranged to move the piston within the purge body.

13. A device according to any one of claims 11 to 12, wherein the return spring is calibrated to maintain the piston in the purge closed position under the purge pressure.

14. Device according to any one of claims 7 to 13, wherein, the part having at least two cavities (15',16') to be depowdered, the interface (13,13a,13b) is arranged so as to communicate with the at least two cavities concomitantly.

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