Powder removal process for a part obtained by additive manufacturing and implementation device

Abstract

A method for removing powder from a part (3) produced by additive manufacturing, the part having a cavity (15) to be depowdered, the cavity having a first opening (151), 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 quickly reducing the pressure from the predetermined maximum to a purge pressure. Figure for the abbreviation: [Fig.2]

Description

Title of the invention: Method for depowdering 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 art

[0002] Depowdering consists of extracting material powder inevitably contained in one or more cavities of a part produced by an additive manufacturing process using a powder bed of material, such as the LBM process (an English acronym for "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 consists of inverting the part to be depowdered while vibrating it using various vibration modes / systems or shock devices. In the vast majority of cases, such a depowdering process allows the residual powder to "flow" by gravity out of the part.

[0004] However, this does not allow for the removal of powder from more complex parts manufactured by additive manufacturing, such as parts containing long, thin channels running within them. Indeed, these parts only partially remove the powder. This causes plugs of material powder that cannot be removed even by repeatedly blowing or rinsing through the inlet / outlet openings of these channels. This is, for example, the case with an aluminum heat exchanger manufactured by additive manufacturing that includes multiple small-diameter (4 mm², for example) and long (1000 mm, for example) pipes. Another possible scenario is the presence of a blind channel (a single opening), which prevents the creation of a gas flow through it. Description of the invention

[0005] An 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.

[0006] To this end, the invention provides a method for depowdering a part produced by additive manufacturing, the part having a cavity to be depowdered, the cavity having a first opening, the method comprising the following steps: a. Pressurizing the cavity by injecting a gas up to a predetermined maximum pressure through the first opening; b. Sudden release of pressure within the cavity by a rapid transition from the predetermined maximum pressure to a purge pressure.

[0007] 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 free of dust. • the pressurization is a quasi-static pressurization. • the cavity forms a circuit within the room. • The purge pressure is equal to ambient pressure or slightly higher than or slightly lower than ambient pressure. • the cavity is blind. • the cavity includes a second opening distinct from the first opening.

[0008] According to the invention, a device for depowdering a part made by additive manufacturing is also provided, 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.

[0009] Advantageously, but optionally, the dust removal device for a part according to the invention has at least one of the following technical characteristics: • 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 consists of 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 includes a purge body, a piston mounted to slide within the purge body between purge closure and purge opening 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 closing position under the purge pressure. • the part having at least two cavities to be depowdered, the interface is arranged so as to communicate with at least two cavities simultaneously. Brief description of the figures

[0010] Other features and advantages of the invention will become apparent from the following description of an embodiment of the invention. See the accompanying drawings:

[0011] [Fig-1] is a perspective and schematic view of a manufacturing installation additive for producing a part to be depowdered by a depowdering process according to the invention;

[0012] [Fig.2] is a schematic view of a first embodiment of a device powder removal according to the invention interfaced with a blind cavity of a part produced by additive manufacturing;

[0013] [Fig.3] is a schematic view of a second embodiment of a device a dust removal system according to the invention interfaced with a through-cavity of a part produced by additive manufacturing; and,

[0014] [Fig.4] a chronogram illustrating the use of a depowdering process according to the invention can be implemented by the dust removal devices of figures 2 and 3;

[0015] [Fig. 5] is a schematic view of an embodiment of purging devices of dusting figures 2 and 3; and,

[0016] [Fig.6] is a schematic view of the second embodiment of a device powder removal according to the invention interfaced with several through cavities of a part made by additive manufacturing.

[0017] For clarity, identical or similar elements are identified by identical reference signs throughout the figures. Detailed description of an implementation method

[0018] With reference to [Fig.1], we will describe an installation 30 for producing a part 3 having a cavity by an additive manufacturing process on a powder bed already known per se.

[0019] 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 the invention, additive manufacturing is selected from the group comprising selective laser melting (SLM) and electron beam melting (EBM). "According to Anglo-Saxon terminology, direct laser additive construction, abbreviated CLAD for "Direct Laser Additive Construction", according to Anglo-Saxon terminology, electron beam additive manufacturing, abbreviated EBAM for "Electron Beam Additive Manufacturing", according to Anglo-Saxon terminology, laser metal deposition, abbreviated LMD for "Laser Metal Deposition", according to Anglo-Saxon terminology.

[0020] In particular, powder bed additive manufacturing is carried out using the selective laser melting (SLM) technique, which involves spreading powder layer by layer using a scraper that determines a set quantity and thickness of powder. A laser then fuses each layer of powder to form the part.

[0021] Powder bed fusion additive manufacturing of part 3 is carried out using a setup 30 as shown in [Fig. 1]. This setup is a selective laser melting (SLM) setup. The setup 30 comprises a first feed tank 31 containing a powder 32 of material and a build platform 33 on which part 3 is manufactured. 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 of powder and the powder thickness 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 constitutes the movable bottom of this second tank 35.The first feed tank 31 also includes a movable bottom 36 that moves vertically upwards along the Z-axis as the powder 32 is transferred onto the build platform 33. The installation 30 also includes a laser beam generation element 37 for melting the powder intended for the 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 installation 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 reservoir 31, which is transferred onto the manufacturing support 33. These powder layers are then melted one after the other by means of the laser beam 40 moving over the surface of each layer.

[0022] Such a manufacturing process makes it possible to produce complex parts 3 which may include cavities of more or less complex shapes in which powder 32 may be present and difficult to remove by current depowdering techniques.

[0023] We will now describe, with reference to [Fig. 2], a first embodiment of a dust removal device 1 according to the invention. The 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 the part 3. This type of cavity is found in parts 3 forming the heat exchanger.

[0024] 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 (Fi) 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 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. On the other hand, the dust removal device 1 according to the invention includes a purge 12 in fluidic connection with the interface 13.The purge 12 allows the gas that has been injected up to the maximum pressure Pmax in the cavity 15 to be evacuated (F2). The injection (F1) and evacuation (F2) of the injected gas takes place here through the first opening 151 of the blind cavity 15.

[0025] With reference to [Fig. 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 the part 3 having a first 151 and a second 162 opening. The cavity 16 is a through cavity within the part 3, in that it extends between the first opening 151 and the second opening 162, forming a circuit within the part 3. To remove the dust from the cavity 16, the dust removal device 1' according to the invention comprises 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 includes a second interface 13b cooperating fluidly with said second opening 162 of the cavity 16.

[0026] In the case where part 3 has several cavities 15', 16', as illustrated in [Fig. 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. This applies, mutatis mutandis, to multiple blind cavities and to the interface 13 of the dust removal device 1.

[0027] The dusting device 1 according to the invention and the dusting device 1' according to the invention can form a single dusting device.

[0028] Now, with reference to [Fig.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 1' according to the invention which have just been previously described.

[0029] The purge 12 comprises a purge body 121 including 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, internal magnet 125, and control magnet 127 are replaced by a pneumatic control to move the piston head 122 between the open and closed positions.

[0030] We will now describe a depowdering process 20 according to the invention for optimally depowdering parts 3 having cavities 15, 16, 15', 16' and produced by a powder bed addition manufacturing process. The description of the depowdering process 20 according to the invention will be given with reference to [Fig. 4],

[0031] 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 within the cavity 15, 16, 15', 16'.

[0032] 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 PI. The purge pressure PI is, for example, equal to or slightly higher than the ambient pressure Patm. In an alternative embodiment, the purge pressure PI 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'. .

[0033] The two previous steps are repeated until the depowdering of cavity 15,16,15',16' is complete.

[0034] In one embodiment, the depowdering process according to the invention operates in an "alternating" manner. Once the second step described above has been carried out, the depowdering process according to the invention draws gas from the cavity 15, 16, 15', 16' at a slow flow rate so as not to draw away any powder 31 still present in the cavity 15, 16, 15', 16'. Then the depowdering process according to the invention resumes at the first step, as indicated in the preceding paragraph. This allows for savings in the gas used to perform the depowdering.

[0035] With regard to the timing diagram of [Fig.4] and a pressure curve 25 shown, the pressurization 21 starts from the purge pressure PI, 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.

[0036] 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 PI (point F).

[0037] Then the depowdering process 20 according to the invention repeats steps 21,22 according to the same chronogram.

[0038] In parallel, in [Fig. 4], an inlet flow curve 26 and an outlet flow curve 27 are shown. 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, which allows for a quasi-static pressure increase. As for the outgoing flow curve 27, it appears when the purge 12 is open and illustrates the sudden release 22. The evacuation flow starts from 0 at the opening of the purge 12 to rise very quickly to a high maximum flow vertically at point D of the pressure curve 25 then falls back to 0 at the closing of the purge 12, vertically at point F.It should be noted that a low incoming flow rate continues, as the pump 10 continues to operate. This high flow rate obtained during the sudden expansion 22 makes it possible to produce a violent movement of gas then under pressure within the cavity 15,16 and thus carry away any powder residue 31 that may be present in said cavity 15,16.

[0039] The illustrative timing diagram of [Fig.4] is obtained with a purge 12 of [Fig.5] previously described. 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, closing the orifice 123, the external magnet 126 being magnetically attracted by the control magnet 127 and thus locking the purge 12.

[0040] At point B, the maximum pressure Pmax is reached within the cavity 15,16.

[0041] 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.

[0042] 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.

[0043] From point E, the piston 122 returns to the closed position by means of the return spring 129 until the purge pressure PI, 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.

[0044] In an alternative embodiment of the purge 12, the internal magnet 125, external magnet 126 and control magnet 127 are replaced by a pneumatic control allowing to move the piston head 122 between the open and closed positions. The previous operation remains valid, mutatis mutandis.

[0045] The depowdering process 20 according to the invention and the depowdering devices 1,1' according to the invention previously described apply to the depowdering of parts 3 such as an element of a turbomachine, in particular a heat exchanger or a turbine blade or injectors, hydraulic blocks, nozzles.

[0046] Naturally, the invention is described above by way of example. It is understood that a person skilled in the art is able to carry out different embodiments of the invention without departing from the scope of the invention.

[0047] It is emphasized that all features, as they appear 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, can be combined with other features or groups of features disclosed herein, provided that this has not been expressly excluded or that technical circumstances make such combinations impossible or meaningless.

Claims

Demands

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. 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 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 pressurization is a quasi-static pressurization.

4. A method according to any one of claims 1 to 3, wherein the cavity forms a circuit within the part.

5. A method according to any one of claims 1 to 4, wherein the purge pressure is equal to ambient pressure or slightly above or slightly below ambient pressure.

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

7. A method according to any one of claims 1 to 5, wherein the cavity comprises a second opening (162) distinct from the first opening.

8. A powder removal device (1,1') for 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 purge (12) in fluidic connection with the interface, the device being arranged to implement a powder removal process according to any one of claims 1 to 7

9. Device according to claim 8, wherein the device comprises a flow regulator (11) between the pump and the interface.

10. Device according to any one of claims 8 to 9 and method according to any one of claims 1 to 6, wherein the pump and the purge are in fluidic communication with the first opening.

11. Device according to any one of claims 8 to 9 and method according to claim 7, wherein the pump is in fluidic communication with the first opening, and the purge is in fluidic communication with the second opening.

12. Device according to any one of claims 8 to 11, wherein the purge comprises a purge body (121), a piston (122) mounted to slide in the purge body between purge closing and purge opening 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.

13. Device according to any one of claims 8 to 11, wherein the purge comprises a purge body, a piston mounted to slide in 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.

14. Device according to any one of claims 12 to 13, wherein the return spring is calibrated so as to maintain the piston in the purge closing position under the purge pressure.

15. Device according to any one of claims 8 to 14, 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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