Device and method for additive manufacturing with a protective gas flow for an optical access window.

Abstract

Additive manufacturing device (20) comprising: - a chamber (7) configured to contain powder (6) and to produce an exhaust gas flow (15) against the powder (6), - a laser source (1) configured to produce a laser beam and expose the powder (6) to the laser beam through a window (2) in the chamber (7), - a blow nozzle (3) and a suction nozzle (8) configured to produce a protective gas flow (18) in the chamber (7) against the window (2). Figure for abbreviation: Fig. 1

Description

Title of the invention: Device and method for additive manufacturing with a protective gas flow for an optical access window. FIELD OF INVENTION

[0001] The invention relates to additive manufacturing, and in particular to additive manufacturing in which the additive manufacturing powder is consolidated by a laser beam. The optical access window is the window that allows the passage of the laser beam. PRIOR TECHNOLOGY

[0002] In additive manufacturing, the additive manufacturing powder is consolidated by a laser beam. The chamber containing the powder has an optical access window to allow the laser beam to enter the chamber. Exposure of the powder to the beam generates a fusion plasma. Laser fumes may be produced within the chamber. These fumes can be deposited on the optical access window. To limit this contamination, a gas flow can be implemented along the window, but it is difficult to adjust this flow to protect the window without disrupting the fluid circulation within the chamber. This adjustment becomes increasingly difficult as the size of the optical access window increases.

[0003] There is a need to protect the optical access window from laser fumes more effectively and simply without disrupting the circulation of fluids in the enclosure. Description of the invention

[0004] An object of the invention is to propose a device and an additive manufacturing method to protect the optical access window from laser fumes more effectively and simply without disturbing the circulation of fluids in the enclosure.

[0005] The objective is achieved within the framework of the present invention by means of an additive manufacturing device comprising:

[0006] - an enclosure configured to contain powder and to produce a flow gaseous evacuation system against powder,

[0007] - a laser source configured to produce a laser beam and expose the powder to laser beam through a window of the enclosure,

[0008] - a blowing nozzle and a suction nozzle configured to produce a protective gas flow in the enclosure against the window.

[0009] Such a device is advantageously and optionally complemented by the following various features, taken alone or in combination: - the exhaust gas flow is centered on an exhaust plane parallel to a powder spreading plane distant from the discharge plane; - the protective gas flow is centered on a protective plane parallel to the window, distant from the protective plane, the protective plane being advantageously separated from the window by a distance less than or equal to 30 mm; - the blowing nozzle is configured to blow a blowing flow rate and the suction nozzle is configured to suction a suction flow rate, the blowing flow rate being strictly greater than the suction flow rate, a ratio of the blowing flow rate to the suction flow rate being advantageously greater than or equal to 1.3 and less than or equal to 3.0; - the blow nozzle is configured to blow a blowing flow rate at a speed greater than or equal to one meter per second and at a pressure greater than an average pressure in the enclosure; - the suction nozzle is configured to suction a flow rate at a speed less than or equal to half a meter per second, and at a pressure lower than an average pressure in the enclosure; - a filtration system configured to filter a fluid drawn in by the suction nozzle and to supply the blowing nozzle with the filtered fluid; - the window extends over a first width in one direction, the suction nozzle and the blowing nozzle are configured to produce the protective flow over a second width in the direction, the second width being greater than or equal to the first width; - the suction nozzle and the blowing nozzle are configured so that the protective gas flow has a uniform flow rate over the second width, with a relative flow rate difference between any two points on the second width being less than or equal to 5%; and - the suction nozzle and the blowing nozzle are configured so that the protective gas flow has a flow rate that increases as one moves away from a center of the window.

[0010] The invention also relates to an additive manufacturing process comprising the following steps:

[0011] - production of an exhaust gas flow against the powder contained in a speaker,

[0012] - exposure of the powder to a laser beam produced by a laser source the beam passing through a window of the enclosure,

[0013] - production of a protective gas flow within the enclosure against the window, the flow being produced by a blower nozzle and a suction nozzle.

[0014] Such a process is advantageously and optionally complemented by - the blowing nozzle blows a blowing flow rate and the suction nozzle draws in a suction flow rate, the blowing flow rate being strictly greater than the suction flow rate, a ratio of the blowing flow rate to the suction flow rate being advantageously greater than or equal to 1.3 and less than or equal to 3.0, preferably the blowing nozzle blows the blowing flow rate at a blowing speed greater than or equal to one meter per second, and at a pressure greater than an average pressure in the enclosure, and preferably the suction nozzle draws in a suction flow rate at a suction speed less than or equal to half a meter per second, and at a pressure less than an average pressure in the enclosure; - a filtration step of a fluid aspirated by the suction nozzle, and a blowing step of the filtered fluid by the blowing nozzle; - the window extends over a first width in one direction, the protective gas flow exhibiting a uniform flow rate over a second width in the same direction, the second width being greater than or equal to the first width, with a relative flow rate difference between two points on the third width being less than or equal to 5%; and - the window extends over a first width in one direction, the protective gas flow presenting a flow rate over a second width in the direction, the second width being greater than or equal to the first width, the flow rate increasing as one moves away from a center of the window. DESCRIPTION OF THE FIGURES

[0015] Other features and advantages of the invention will become apparent from the following description, which is purely illustrative and not limiting, and should be read in conjunction with the accompanying drawings on which:

[0016] [Fig.1]

[0017] [Fig.2]

[0018] Figures 1 and 2 are schematic representations of an additive manufacturing device according to an embodiment of the invention. DETAILED DESCRIPTION OF THE INVENTION Additive manufacturing device

[0019] With reference to Figures 1 and 2, an additive manufacturing device 20 comprises an enclosure 7 configured to contain additive manufacturing powder 6. The enclosure 7 is a sealed enclosure in which a gaseous environment is controlled. In particular, the gaseous environment may consist of an inert gas. In this way, the gaseous environment in contact with the powder 6 does not alter the powder 6.

[0020] The powder 6 is composed of a powdery material (metallic powder, powder of ceramics, etc.) intended to be consolidated layer by layer by total or partial selective melting. The powder 6 can be spread according to a spreading plane 17 which is preferably horizontal and located in a lower part of the enclosure 7.

[0021] With reference to Figures 1 and 2, the horizontal plane corresponds to the plane defined by the x and y axes. The vertical direction is given by the z axis, which is oriented upwards in these figures.

[0022] The fusion is carried out with a power source, which in this case is a laser source 1 configured to produce a laser beam and expose the powder 6 to the laser beam through a window 2 in the enclosure 7. The laser source allows for the selective consolidation of areas of the powder exposed to the laser beam. The laser source 1, included in the additive manufacturing device 20, is located outside the enclosure 7 and opposite a window 2 situated on one of the walls of the enclosure 7. The laser source 1 can emit a laser beam 4, or several laser sources can emit several laser beams simultaneously.

[0023] Window 2 is transparent to the wavelength of the laser beam 4. In this way, little or no energy from the laser beam 4 is lost when passing through window 2.

[0024] The window 2 is preferably rectangular in shape, horizontal and located in the upper part of the enclosure 7 opposite the powder 6.

[0025] The enclosure 7 is configured to produce an exhaust gas flow 15 against the powder 6. This gas flow is intended to evacuate lasage fumes produced during the melting of the powder. For example, the exhaust flow 15 is a laminar flow of inert gas generated inside the enclosure 7 against the powder 6. In particular, the exhaust flow 15 flows above the powder 6 and has a flow rate strong enough to carry away lasage fumes produced during the melting of the powder and weak enough not to displace the powder 6. The gas flow 15 has, for example, a thickness of 5 mm above the powder at a speed of 1 to 2 meters per second. Two nozzles 13 and 14, located inside the enclosure, can, for example, be used to produce the gas flow 15.

[0026] Advantageously, the exhaust gas flow 15 is centered on an exhaust plane Pe parallel to a powder spreading plane 17. When the spreading plane 17 is horizontal, the exhaust plane Pe is also horizontal.

[0027] The spreading plane 17 is distant from the discharge plane Pe. The discharge flow 15 extends in a direction orthogonal to the discharge plane Pe such that the maximum flow rate is reached in the discharge plane or at least in an area surrounding the discharge plane Pe. As one moves away from the discharge plane Pe along the orthogonal direction, the flow rate The evacuation area 15 decreases. The distance separating the spreading plane 17 and the evacuation plane Pe is advantageously less than or equal to 4 millimeters. The distance may be between 1 and 4 millimeters and more advantageously between 2 and 3 millimeters.

[0028] The additive manufacturing device 20 further includes a blow nozzle 3 and a suction nozzle 8 configured to produce a protective gas flow 18 in the enclosure 7 against the window 2.

[0029] The blow nozzle 3 is understood herein as a device that blows a gas, such as an inert gas. For example, the blow nozzle 3 can be connected via a blow manifold 5 to a blow fan 10.

[0030] The suction nozzle 8 is understood here as a device that suctions a gas, such as an inert gas. For example, the suction nozzle 8 can be connected via a suction manifold 9 to a suction fan 11.

[0031] The main direction of the protective gas flow 18 is directed from the blow nozzle 3 to the suction nozzle 8. The protective gas flow 18 is preferably a laminar flow of inert gas. The blow nozzle 3 is located inside the enclosure on one side of the window, and the suction nozzle 8 is located inside the enclosure on the other side of the window, so that the two nozzles are inside the enclosure 7 and opposite each other.

[0032] Between these two nozzles, the protective gas flow 18 flows against the window inside the enclosure 7.

[0033] Compared to the prior art, the use of the blow nozzle 3 and the suction nozzle 8 makes it easier to control the characteristics of the protective gas flow, and the window can be protected more effectively from laser fumes. In particular, it is possible to produce a laminar gas flow capable of protecting larger windows than in the prior art. It is also possible to protect the window with a flow rate lower than the disturbance flow rate. The disturbance flow rate is a flow rate at which the protective flow disrupts the gas circulation in the gaseous environment of the enclosure 7, such as the diffusion of laser fumes into the enclosure 7 or the exhaust flow 15 flowing against the powder 6.

[0034] Advantageously, the protective gas flow 18 is centered on a protective plane Pp parallel to the window 2. When the window 2 is horizontal, the protective plane Pp is also horizontal, the blowing nozzle 3 and the suction nozzle 8 are separated by a horizontal distance, for example along the x-axis.

[0035] The window 2 is separated from the protective plane Pp. The protective flow 18 extends in a direction orthogonal to the protective plane Pp so that the maximum flow rate is reached in the protective plane Pp or at least in an area surrounding the protective plane Pp. As one moves away from the protective plane Pp along the orthogonal direction, the flow rate of the protective flow Pp decreases. The distance between the protective plane Pp and the window 2 is advantageously less than or equal to 30 millimeters. The distance can be between 5 and 25 millimeters, and more advantageously between 7 and 15 millimeters. The closer the nozzles 3, 8 are placed to the window 2, the easier it is to obtain a laminar flow of the protective flow 18: lower flow rates of the protective flow allow for laminar flow of the protective flow 18. The window can thus be protected from laser fumes with flow rates even further from the disturbance flow rate.

[0036] The blowing nozzle 3 is configured to blow a flow rate ds and the suction nozzle 8 is configured to suction a flow rate da. The blowing flow rate ds is advantageously chosen to be strictly greater than the suction flow rate da. This prevents the suction nozzle from drawing in laser fumes from the laser fusion process. In this situation, only a portion of the flow blown by the blowing nozzle is drawn in by the suction nozzle. Part of the blown flow moves away from the area, and in particular from the window. Therefore, there is a component of the protective flow 18 that pushes the laser fumes further away from the window.

[0037] Another fluid circulation system in the enclosure 7 can draw air into the enclosure so that the part of the flow blown by the blow nozzle that is not drawn in by the suction nozzle does not disturb the average pressure inside the enclosure and more generally the circulation of gases in the enclosure.

[0038] When the blowing flow rate ds is chosen to be greater than the suction flow rate da, a ratio ds / da of the blowing flow rate to the suction flow rate advantageously greater than or equal to 1.3 and less than or equal to 3.0 is chosen. The ratio can in particular be adjusted according to the geometry of the window and the length separating the blowing nozzle 3 and the suction nozzle 8: if this length increases, a lower ds / da ratio can be chosen.

[0039] As an option concerning the blowing nozzle, the fluid blown by the blowing nozzle can be blown at a speed greater than or equal to one meter per second and at a pressure greater than the average pressure in the enclosure. For this purpose, the blowing nozzle 3 can be connected to the blowing manifold 5, the pressure of which is greater than the pressure prevailing in the enclosure 7 and allowing a blowing speed greater than or equal to 1 m / s.

[0040] As an option concerning the suction nozzle, the fluid drawn in by the suction nozzle can be drawn at a suction speed less than or equal to half a meter per second and at a pressure lower than the average pressure in the enclosure. For this purpose, the suction nozzle 8 can be connected to the suction manifold 9, the pressure is lower than the pressure prevailing in enclosure 7 and allowing the aspiration speed less than or equal to 0.5 m / s.

[0041] In one embodiment, the device 20 includes a filtration system 12. The filtration system 12 is configured to filter the fluid drawn in by the suction nozzle and to supply the blowing nozzle with the filtered fluid. In other words, the filtration system 12 enables a recirculation loop of the protective flow gas 18. The gas drawn in by the suction nozzle 8 is, once filtered, recirculated to the blowing nozzle 3, which blows it back against the window 2.

[0042] To achieve this embodiment, one can use: - the blower fan 10 which, as previously shown, is fluidly connected to the blower nozzle 3 via the blower manifold 5 and - the suction fan 11 which, as previously shown, is fluidly connected to the suction nozzle 8 via the suction manifold 9.

[0043] In this case, the blower fan 10 can be fluidly connected to an outlet of the filtration system 12 and the suction fan 11 to an inlet of the filtration system 12.

[0044] A main fan 21 can also be added to ensure a minimum flow rate in the gas circulation loop of the protective flow 18. For example, the main fan is fluidly connected to the outlet of the filtration system 12.

[0045] According to a configuration illustrated in [Fig. 1], the filtration system 12 can also be configured to filter the fluid from the exhaust gas flow 15 that flows against the powder 6. To this end, the two nozzles 13 and 14 that produce the exhaust gas flow 15 are then fluidly connected to the filtration system 12. One of the nozzles 13 and 14 is fluidly connected to the inlet of the filtration system 12, and the other of the nozzles 13 and 14 is fluidly connected to the outlet of the filtration system 12. If the system includes a main fan 21 fluidly connected to the outlet of the filtration system 12, the outlet of the main fan 21 can be fluidly connected on one side to the blow nozzle 3 via the blow manifold and on the other side to one of the nozzles 13 and 14 that produce the exhaust gas flow 15.

[0046] The window 2 can extend over a first width in one direction, the suction nozzle and the blowing nozzle are configured to produce a protective flow over a second width in the direction, the second width being greater than or equal to the first width.

[0047] The direction mentioned above can be described as a transverse direction, that is to say said orthogonal to the main direction of the protective flow. The main flow direction is the direction in which the blow nozzle 3 and the suction nozzle 8 are opposite each other.

[0048] Preferably, the window 2 is rectangular and the transverse direction and the main flow direction correspond to the directions of the sides of the rectangle formed by the window.

[0049] When the window 2 is horizontal, the transverse direction is a horizontal direction. If the blowing nozzle 3 and the suction nozzle 8 are separated by a horizontal distance along the x-axis, then the transverse direction is parallel to the y-axis, as shown in [Fig.2].

[0050] In order for the second width along the direction to be greater than or equal to the first width, one can for example choose a suction nozzle and a blowing nozzle which extend in the transverse direction with a third width greater than the first width of the window.

[0051] In a first embodiment, the flow rate of the protective gas flow is uniform over the second width. In other words, when a segment directed along the transverse direction that crosses the protective gas flow is chosen, the flow rate at each point of this segment remains constant or substantially constant. Here, constant or substantially constant means a relative difference in flow rate between two points of the second width of less than or equal to 5%.

[0052] In a second embodiment, the flow rate of the protective gas flow is variable over the second width, and more precisely, the flow rate increases as one moves away from a center of the window. In other words, when a segment directed along the transverse direction that crosses the protective gas flow is chosen, the flow rate at each point of this segment varies along the segment. The flow rate is minimum at a central point of the segment that corresponds to the center of the window. The flow rate increases on either side of this central point. Here, the center of the window is understood to be a central direction of the window oriented along the principal flow direction and orthogonal to the transverse direction. The central direction passes through the center of the window. For example, and in relation to [Fig.[2], when window 2 is rectangular, the central direction De passes through the center of the rectangle and is parallel to two of the sides of the rectangle: this is one of the axes of symmetry of the rectangle. Additive manufacturing process

[0053] An additive manufacturing device 20 as just presented allows an additive manufacturing process to be implemented comprising the following steps.

[0054] In a first step, an evacuation gas flow 15 is produced against the powder 6 contained in the enclosure 7. This flow is intended to evacuate the lasing fumes produced during the melting of the powder 6.

[0055] In a second step, the powder 6 is exposed to a laser beam produced by the laser source 1 through the window 2 of the enclosure 7. This step provides the powder 6 with sufficient energy to cause it to solidify. Laser fumes may be emitted by the powder 6, and these are then carried away by the exhaust gas flow 15. However, the exhaust flow 15 does not remove all the laser fumes from the enclosure.

[0056] In a third step, a protective gas flow 18 is produced in the enclosure 7 against the window 2, the flow being produced by the blow nozzle 3 and the suction nozzle 8. The protective flow 18 flows against the window 2 and makes it possible to keep away from the window 2 the laser fumes which would not be removed from the enclosure by the protective gas flow.

[0057] The terms first step, second step, and third step are used here to describe actions carried out during the process, but without being limited to a particular chronological order between them. In particular, these steps can be carried out simultaneously.

[0058] Optionally, the blowing nozzle 3 blows a blowing flow rate ds and the suction nozzle 8 draws in a suction flow rate da, the blowing flow rate being strictly greater than the suction flow rate.

[0059] A ratio ds / da of the blowing flow rate to the suction flow rate can advantageously be chosen greater than or equal to 1.3 and less than or equal to 3.0.

[0060] Preferably the blow nozzle 3 blows the blowing flow at a blowing speed greater than or equal to one meter per second, and at a pressure greater than an average pressure in the enclosure.

[0061] Preferably, the suction nozzle 8 draws in a suction flow at a suction speed less than or equal to half a meter per second, and at a pressure lower than the average pressure in the enclosure

[0062] In one embodiment, the process includes a step of filtering a fluid aspirated by the suction nozzle 8, and a step of blowing the filtered fluid by the blowing nozzle 3. The device 20 then includes the filtration system 12 as described above.

[0063] In a first variant, as described above, the window 2 extends over a first width in one direction, the gas flow having a uniform flow rate over a second width in the direction, the second width being greater than or equal to the first width, a relative difference in flow rate between two points of the third width being less than or equal to 5%.

[0064] In a second embodiment, as described above, the window extends over a first width in one direction, the gas flow having a flow rate over a second width in the direction, the second width being greater than or equal to the first width, the flow rate increasing as one moves away from a center of the window.

Claims

Claims

1. Additive manufacturing device (20) comprising: - an enclosure (7) configured to contain powder (6) and to produce an exhaust gas flow (15) against the powder (6), - a laser source (1) configured to produce a laser beam and expose the powder (6) to the laser beam through a window (2) of the enclosure (7), - a blowing nozzle (3) and a suction nozzle (8) configured to produce a shielding gas flow (18) in the enclosure (7) against the window (2), the blowing nozzle (3) being configured to blow a blowing flow rate and the suction nozzle (8) is configured to suck a suction flow rate, the blowing flow rate being strictly greater than the suction flow rate.

2. Device according to claim 1 in which the evacuation gas flow (15) is centered on an evacuation plane parallel to a spreading plane (17) of the powder (6) distant from the evacuation plane (Pe).

3. Device according to any one of claims 1 to 2 in which the protective gas flow (18) is centered on a protection plane (Pp) parallel to the window (2) distant from the protection plane (Pp), the protection plane (Pp) being advantageously separated from the window (2) by a distance less than or equal to 30 mm.

4. A device according to any one of claims 1 to 3 wherein a ratio of the blowing flow rate to the suction flow rate is greater than or equal to 1.3 and less than or equal to 3.

0.

5. Device according to any one of claims 1 to 4 in which the blowing nozzle (3) is configured to blow a blowing flow - at a speed greater than or equal to one meter per second and, - at a pressure greater than an average pressure in the enclosure (7).

6. Device according to any one of claims 1 to 5 wherein the suction nozzle (8) is configured to suck a suction flow rate - at a speed less than or equal to half a meter per second, and - at a pressure lower than an average pressure in the enclosure (7).

7. Device according to any one of claims 1 to 6 comprising a filtration system (12) configured to filter a fluid sucked by the suction nozzle (8) and to supply the blowing nozzle (3) with the filtered fluid.

8. Device according to any one of claims 1 to 7 wherein the window (2) extends over a first width in a direction (y), the suction nozzle (3) and the blowing nozzle (8) are configured to produce the protective flow (18) over a second width in the direction (y), the second width being greater than or equal to the first width.

9. Device according to claim 8 wherein the suction nozzle (3) and the blowing nozzle (8) are configured so that the protective gas flow (18) has a uniform flow rate over the second width, a relative difference in flow rate between two points of the second width being less than or equal to 5%.

10. Device according to claim 8 in which the suction nozzle (3) and the blowing nozzle (8) are configured so that the protective gas flow (18) has a flow rate which increases as one moves away from a center of the window (2).

11. Additive manufacturing method comprising the following steps: - producing an exhaust gas flow (15) against powder (6) contained in an enclosure (7), - exposing the powder (6) to a laser beam produced by a laser source (1), the beam passing through a window (2) of the enclosure (7), - producing a shielding gas flow (18) in the enclosure (7) against the window (2), the flow being produced by a blowing nozzle (3) and a suction nozzle (8), the blowing nozzle (3) blowing a blowing flow rate and the suction nozzle (8) sucking a suction flow rate, the blowing flow rate being strictly greater than the suction flow rate.

12. A method according to claim 11 wherein a ratio of the blowing flow rate to the suction flow rate is greater than or equal to 1.3 and less than or equal to 3.0, preferably the blowing nozzle (3) blows the blowing flow rate at a blowing speed greater than or equal to one meter per second, and at a pressure greater than an average pressure in the enclosure (7), and preferably the suction nozzle (8) sucks a suction flow rate at a suction speed less than or equal to half a meter per second, and at a pressure less than an average pressure in the enclosure (7).

13. A method according to any one of claims 11 to 12 comprising a step of filtering a fluid sucked by the suction nozzle (8), and a step of blowing the filtered fluid by the blowing nozzle (3).

14. A method according to any one of claims 11 to 13 wherein the window (2) extends over a first width in a direction (y), the shielding gas flow (18) having a uniform flow rate over a second width in the direction (y), the second width being greater than or equal to the first width, a relative difference in flow rate between two points of the third width being less than or equal to 5%.

15. A method according to any one of claims 11 to 13 wherein the window (2) extends over a first width in a direction (y), the shielding gas flow (18) having a flow rate over a second width in the direction (y), the second width being greater than or equal to the first width, the flow rate increasing with distance from a center of the window (2).

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