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

Abstract

The invention relates to an additive manufacturing device (20) comprising: - an enclosure (7) configured to contain powder (6) and to produce a discharge 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 protective gas flow (18) in the enclosure (7) against the window (2).

Description

[0001] Device and method for additive manufacturing with a protective gas flow of an optical access window

[0002] FIELD OF THE INVENTION

[0003] The invention relates to additive manufacturing and in particular to additive manufacturing in which the additive manufacturing powder is consolidated by laser beam. The optical access window is the window which allows the passage of the laser beam.

[0004] STATE OF THE ART

[0005] In additive manufacturing, the additive manufacturing powder is consolidated by a laser beam. The enclosure containing the powder has an optical access window to allow the laser beam to enter the enclosure. Exposure of the powder to the beam generates a fusion plasma. Laser fumes can be produced in the enclosure. These can be deposited on the optical access window. To limit this pollution, a gas flow can be implemented along the window, but it is difficult to adjust this flow so that it protects the window without disturbing the circulation of fluids in the enclosure. The adjustment becomes even more difficult to achieve as the size of the optical access window increases.

[0006] 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.

[0007] STATEMENT OF THE INVENTION

[0008] An aim 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 more simply without disturbing the circulation of fluids in the enclosure.

[0009] The aim is achieved within the framework of the present invention thanks to an additive manufacturing device comprising:

[0010] - an enclosure configured to contain powder and to produce an exhaust gas flow against the powder,

[0011] - a laser source configured to produce a laser beam and expose the powder to the laser beam through a window of the enclosure,

[0012] - a blowing nozzle and a suction nozzle configured to produce a protective gas flow in the enclosure against the window. Such a device is advantageously and optionally supplemented by the following various characteristics taken alone or in combination:

[0013] - the evacuation gas flow is centered on an evacuation plane parallel to a powder spreading plane distant from the evacuation plane;

[0014] - the protective gas flow is centered on a protection plane parallel to the window distant from the protection plane, the protection plane being advantageously separated from the window by a distance less than or equal to 30 mm;

[0015] - the blowing nozzle is configured to blow a blowing flow rate and the suction nozzle is configured to suck 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;

[0016] - the blowing nozzle 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;

[0017] - the suction nozzle is configured to draw a suction flow at a speed less than or equal to half a meter per second, and at a pressure less than an average pressure in the enclosure;

[0018] - a filtration system configured to filter a fluid sucked by the suction nozzle and to supply the blowing nozzle with the filtered fluid;

[0019] - 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;

[0020] - the suction nozzle and the blowing nozzle are configured so that the protective gas flow 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%; and

[0021] - 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.

[0022] The invention also relates to an additive manufacturing method comprising the following steps:

[0023] - production of an exhaust gas flow against powder contained in an enclosure, - exposure of the powder to a laser beam produced by a laser source, the beam passing through a window of the enclosure,

[0024] - production of a protective gas flow in the enclosure against the window, the flow being produced by a blowing nozzle and a suction nozzle.

[0025] Such a process is advantageously and optionally supplemented by

[0026] - the blowing nozzle blows a blowing flow and the suction nozzle sucks in a suction flow, the blowing flow being strictly greater than the suction flow, a ratio of the blowing flow to the suction flow 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 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 sucks in a suction flow 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;

[0027] - a step of filtering a fluid sucked in by the suction nozzle, and a step of blowing the filtered fluid by the blowing nozzle;

[0028] - the window extends over a first width in one direction, the shielding 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%; and

[0029] - the window extends over a first width in one direction, the shielding 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.

[0030] DESCRIPTION OF FIGURES

[0031] Other characteristics and advantages of the invention will emerge from the following description, which is purely illustrative and non-limiting, and must be read in conjunction with the appended drawings in which:

[0032] - Figures 1 and 2 are schematic representations of an additive manufacturing device according to one embodiment of the invention. DETAILED DESCRIPTION OF THE INVENTION

[0033] 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 be composed of an inert gas. In this way, the gaseous environment in contact with the powder 6 does not alter the powder 6.

[0034] The powder 6 is composed of a powdery material (metal powder, ceramic powder, etc.) intended to be consolidated layer by layer, by total or partial selective fusion. 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.

[0035] Referring 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.

[0036] The fusion is carried out with a power source which is here 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. The laser source makes it possible to selectively consolidate 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 located 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.

[0037] Window 2 is transparent to the wavelength of laser beam 4. In this way, little or no energy from laser beam 4 is lost when passing through window 2.

[0038] The window 2 is preferably rectangular in shape, horizontal and located in the upper part of the enclosure 7 opposite the powder 6.

[0039] The enclosure 7 is configured to produce an evacuation gas flow 15 against the powder 6. This gas flow is intended to evacuate lasing fumes produced during the melting of the powder. For example, the evacuation flow 15 is a laminar flow of inert gas generated inside the enclosure 7 against the powder 6. In particular, the evacuation flow 15 flows above the powder 6 and has a flow rate that is strong enough to carry away lasing 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 high above the powder at a speed of 1 to 2 meters per second. Two nozzles 13 and 14, placed inside the enclosure, can for example be used to produce the gas flow 15.

[0040] Advantageously, the evacuation gas flow 15 is centered on an evacuation plane Pe parallel to a spreading plane 17 of the powder. When the spreading plane 17 is horizontal, the evacuation plane Pe is also horizontal.

[0041] 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 so 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 in the orthogonal direction, the flow rate of the discharge flow 15 decreases. The distance separating the spreading plane 17 and the discharge 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.

[0042] The additive manufacturing device 20 further comprises a blowing nozzle 3 and a suction nozzle 8 configured to produce a protective gas flow 18 in the enclosure 7 against the window 2.

[0043] The blowing nozzle 3 is understood here as a device which blows a gas such as for example an inert gas. For example, the blowing nozzle 3 can be connected via a blowing manifold 5 to a blowing fan 10.

[0044] The suction nozzle 8 is understood here as a device that sucks in a gas such as, for example, an inert gas. For example, the suction nozzle 8 can be connected via a suction manifold 9 to a suction fan 11.

[0045] The main direction of shielding gas flow 18 is directed from the blowing nozzle 3 to the suction nozzle 8. The shielding gas flow 18 is preferably a laminar flow of inert gas. The blowing 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.

[0046] Between these two nozzles, the protective gas flow 18 flows against the window inside the enclosure 7.

[0047] Compared with the prior art, the use of the blowing nozzle 3 and the suction nozzle 8 makes it easier to control the characteristics of the shielding gas flow, and the window can be more effectively protected from lasing fumes. In particular, it is possible to produce a laminar gas flow capable of protecting windows of a larger size than in the prior art. It is also possible to protect the window with a flow rate lower than a disturbance flow rate. The disturbance flow rate is a flow rate from which the shielding flow disturbs the circulation of gases in the gaseous environment of the enclosure 7, such as for example the diffusion of the lasing fumes in the enclosure 7 or the exhaust flow 15 which flows against the powder 6.

[0048] Advantageously, the protective gas flow 18 is centered on a protection plane Pp parallel to the window 2. When the window 2 is horizontal, the protection 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.

[0049] Window 2 is separated from the protection plane Pp. The protection flow 18 extends in a direction orthogonal to the protection plane Pp so that the maximum flow rate of the flow is reached in the protection plane Pp or at least in an area surrounding the protection plane Pp. As one moves away from the protection plane Pp in the orthogonal direction, the flow rate of the protection flow Pp decreases. The distance separating the protection plane Pp and window 2 is advantageously less than or equal to 30 millimeters. The distance may be between 5 and 25 millimeters and more advantageously between 7 and 15 millimeters. The closer one chooses to place the nozzles 3, 8 to the window 2, the easier it is to obtain a laminar flow of the protection flow 18: lower flow rates of the protection flow make it possible to obtain a laminar flow of the protection flow 18.This allows the window to be protected from laser fumes with flow rates even further away from the disturbance flow rate.

[0050] The blowing nozzle 3 is configured to blow a blowing flow rate ds and the suction nozzle 8 is configured to suck a suction 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 sucking in laser fumes from the laser melting process. In this situation, only a portion of the flow blown by the blowing nozzle is sucked in by the suction nozzle. A portion of the blown flow moves away from the area and in particular from the window. There is therefore a component of the protective flow 18 which pushes the laser fumes further away from the window.

[0051] Another fluid circulation system in the enclosure 7 can draw air into the enclosure so that the part of the flow blown by the blowing nozzle which is not drawn by the suction nozzle does not disturb the average pressure inside the enclosure and more generally the circulation of gases in the enclosure.

[0052] 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 is chosen which is advantageously greater than or equal to 1.3 and less than or equal to 3.0. 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 ratio ds / da can be chosen.

[0053] As an option for the blowing nozzle, the fluid blown by the blowing nozzle can be blown 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. For this purpose, the blowing nozzle 3 can be connected to the blowing manifold 5 whose pressure is greater than the pressure prevailing in the enclosure 7 and allowing the blowing speed greater than or equal to 1 m / s.

[0054] As an option for the suction nozzle, the fluid sucked by the suction nozzle can be sucked at a suction speed less than or equal to half a meter per second and at a pressure lower than an average pressure in the enclosure. For this purpose, the suction nozzle 8 can be connected to the suction manifold 9 whose pressure is lower than the pressure prevailing in the enclosure 7 and allowing the suction speed less than or equal to 0.5 m / s.

[0055] In one embodiment, the device 20 comprises a filtration system 12. The filtration system 12 is configured to filter the fluid sucked in by the suction nozzle and to supply the blowing nozzle with the filtered fluid. In other words, the filtration system 12 makes it possible to create a circulation loop for the gas of the protective flow 18. The gas sucked in by the suction nozzle 8 is, once filtered, recirculated to the blowing nozzle 3 which blows it back against the window 2.

[0056] To achieve this method, you can use:

[0057] - the blowing fan 10 which, as presented previously, is fluidically connected to the blowing nozzle 3 via the blowing manifold 5 and

[0058] - the suction fan 11 which, as previously presented, is fluidically connected to the suction nozzle 8 via the suction manifold 9.

[0059] In this case, the blower fan can be fluidly connected

[0060] 10 to an outlet of the filtration system 12 and the suction fan

[0061] 11 to an inlet of the filtration system 12.

[0062] A main fan 21 may also be added to ensure a minimum flow rate in the gas circulation loop of the shield flow 18. For example, the main fan is fluidly connected to the outlet of the filtration system 12. According to a configuration illustrated in FIG. 1, the filtration system 12 may also be configured to filter the fluid of the exhaust gas flow 15 which flows against the powder 6. For this purpose, the two nozzles 13 and 14 which 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 comprises 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 the one hand to the blowing nozzle 3 via the blowing manifold and on the other hand to one of the nozzles 13 and 14 which produce the exhaust gas flow 15.

[0063] The window 2 may 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.

[0064] The direction mentioned above can be described as a transverse direction, i.e. orthogonal to the main direction of the protective flow. The main flow direction is the direction in which the blowing nozzle 3 and the suction nozzle 8 are opposite each other.

[0065] 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.

[0066] When 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 Figure 2.

[0067] To make the second width in the direction 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 according to a third width greater than the first width of the window.

[0068] In a first variant, the flow rate of the protective gas flow is uniform over the second width. In other words, when a segment directed in the transverse direction which 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 is understood to mean a relative difference in flow rate between two points of the second width less than or equal to 5%.

[0069] In a second variant, the flow rate of the shielding 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 in the transverse direction which crosses the shielding 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 which 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 mean a central direction of the window oriented in the main direction of flow and orthogonal to the transverse direction. The central direction passes through the center of the window.For example, and in relation to Figure 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.

[0070] Additive manufacturing process

[0071] An additive manufacturing device 20 as just presented makes it possible to implement an additive manufacturing method comprising the following steps.

[0072] During 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.

[0073] During 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 makes it possible to provide the powder 6 with sufficient energy to cause its consolidation. Laser fumes may be emitted by the powder 6 and these are then carried away by the exhaust gas flow 15. The exhaust flow 15 does not, however, make it possible to remove all the laser fumes from the enclosure.

[0074] During a third step, a protective gas flow 18 is produced in the enclosure 7 against the window 2, the flow being produced by the blowing nozzle 3 and the suction nozzle 8. The protective flow 18 flows against the window 2 and makes it possible to keep the laser fumes that would not be removed from the enclosure by the protective gas flow away from the window 2.

[0075] The terms first step, second step and third step are used here to describe actions performed during the process, but are not limited to any particular chronological order between them. In particular, these steps can be performed at the same time.

[0076] Optionally, the blowing nozzle 3 blows a blowing flow rate ds and the suction nozzle 8 sucks a suction flow rate da, the blowing flow rate being strictly greater than the suction flow rate. 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.

[0077] Preferably, the blowing 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.

[0078] Preferably, the suction nozzle 8 draws a suction flow at a suction speed less than or equal to half a meter per second, and at a pressure lower than an average pressure in the enclosure.

[0079] In one embodiment, the method comprises a step of filtering a fluid sucked in by the suction nozzle 8, and a step of blowing the filtered fluid by the blowing nozzle 3. The device 20 then comprises the filtration system 12 as described previously.

[0080] In a first variant, as described previously, 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%.

[0081] In a second variation, as previously described, 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 with distance 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 protective 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. Device according to any one of claims 1 to 3 in which 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 wherein 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 higher 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 - 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 wherein 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 process comprising the following steps: - production of an evacuation gas flow (15) against powder (6) contained in an enclosure (7), - exposure of the powder (6) to a laser beam produced by a laser source (1), the beam passing through a window (2) of the enclosure (7), - production of a protective 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. Method according to claim 11 in which 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. Method according to any one of claims 11 to 12 comprising a step of filtering a fluid sucked in by the suction nozzle (8), and a step of blowing the filtered fluid by the blowing nozzle (3).

14. Method according to any one of claims 11 to 13 in which 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 as one moves away from a center of the window (2).

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