Apparatus and method for additive manufacturing using protective gas flow to protect optical access windows

Abstract

The present invention provides an additive manufacturing apparatus (20), comprising: an enclosure (7) configured to contain a powder (6) and to generate an exhaust gas flow (15) relative to the powder (6); a laser source (1) configured to generate a laser beam and expose the powder (6) to the laser beam through a window (2) in an enclosure (7); - an additive manufacturing device (20) comprising a spray nozzle (3) and a suction nozzle (8) configured to generate a protective gas flow (18) within an enclosure (7) relative to a window (2).

Description

[Technical Field]

[0001] The present invention relates to additive manufacturing, and in particular to additive manufacturing where additive manufacturing powder is consolidated by a laser beam. An optical access window is a window through which a laser beam passes. [Background technology]

[0002] When 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. Exposing the powder to the beam generates a fusion plasma. Laser fumes can be generated within the enclosure, which can deposit on the optical access window. To limit this contamination, a gas flow can be implemented along the window, but adjusting this flow to protect the window without interfering with the fluid flow within the enclosure is difficult. Adjustment becomes more difficult as the size of the optical access window increases.

[0003] There is a need for a more effective and simpler way to protect the optical access window from laser fumes without impeding the flow of fluid within the enclosure. Summary of the Invention

[0004] One object of the present invention is to provide an additive manufacturing apparatus and method for more effectively and simply protecting optical access windows from laser fumes without impeding fluid flow within the enclosure.

[0005] This object is achieved within the scope of the present invention by an additive manufacturing device, which comprises an enclosure configured to contain the powder and to generate an exhaust gas flow relative to the powder; a laser source configured to generate a laser beam and expose the powder to the laser beam through a window in the enclosure; a blowing nozzle and a suction nozzle configured to generate a protective gas flow within the enclosure against the window.

[0006] Such a device may have the following various features, either alone or in combination: the discharge gas flow is centered on the discharge plane parallel to the powder distribution plane away from the discharge plane; the protective gas flow is parallel to the window and centred on the protective surface, which is advantageously spaced from the window by a distance of not more than 30 millimetres; the spray nozzle is configured to spray a spray flow rate and the suction nozzle is configured to aspirate a suction flow rate, the spray flow rate being strictly greater than the suction flow rate, the ratio of the spray flow rate to the suction flow rate advantageously being greater than or equal to 1.3 and less than or equal to 3.0; the spray nozzle is configured to spray the spray flow rate at a velocity of at least 1 meter / second and at a pressure greater than the average pressure in the enclosure; the suction nozzle is configured to draw a suction flow rate at a velocity of 0.5 meters / second or less and at a pressure less than the average pressure in the enclosure; the filtration system is configured to filter the fluid drawn in by the suction nozzle and to supply the filtered fluid to the spray nozzle; the window extends over a first width in one direction, and the suction nozzle and the blowing nozzle are configured to generate a protective flow over a second width in that direction, the second width being equal to or greater than the first width; the suction nozzle and the spray nozzle are configured such that the protective gas flow has a uniform flow rate across the second width, and the relative difference in flow rate between two points on the second width is no more than 5%; The suction nozzle and the spray nozzle are advantageously and optionally completed by being configured so that the protective gas flow has a flow rate that increases with the distance from the center of the window.

[0007] The present invention also provides an additive manufacturing method comprising: - generating an exhaust gas flow relative to a powder contained in an enclosure; - exposing the powder to a laser beam generated by a laser source, the beam passing through a window in the enclosure; generating a protective gas flow within the enclosure relative to the window, the flow being generated by a spray nozzle and a suction nozzle.

[0008] Such a method is the spray nozzle sprays a spray flow rate and the suction nozzle draws in a suction flow rate, the spray flow rate being strictly greater than the suction flow rate, the ratio of the spray flow rate to the suction flow rate advantageously being greater than or equal to 1.3 and less than or equal to 3.0, preferably the spray nozzle sprays the spray flow rate at a spray speed of at least 1 meter / s and at a pressure higher than the average pressure in the enclosure, and preferably the suction nozzle draws in a suction flow rate at a suction speed of not more than 0.5 meters / s and at a pressure lower than the average pressure in the enclosure; - filtering the fluid drawn in through the suction nozzle and spraying the filtered fluid through the spray nozzle; the window extends over a first width in one direction, the protective gas flow has a uniform flow rate over a second width in that direction, the second width being equal to or greater than the first width, and the relative difference in flow rate between two points of a third width being 5% or less; Advantageously and optionally completed by the window extending over a first width in one direction and the protective gas flow having a flow rate over a second width in that direction, the second width being equal to or greater than the first width, the flow rate increasing with distance from the center of the window. [Brief explanation of the drawings]

[0009] Further characteristics and advantages of the invention will become apparent from the following description, which is purely illustrative and non-limiting, and which should be read in conjunction with the accompanying drawings, in which:

[0010] [Figure 1]FIG. 1 is a schematic diagram of an additive manufacturing apparatus according to an embodiment of the present invention. [Figure 2] FIG. 1 is a schematic diagram of an additive manufacturing apparatus according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] Additive Manufacturing Equipment 1 and 2, additive manufacturing apparatus 20 comprises an enclosure 7 configured to contain additive manufacturing powder 6. Enclosure 7 is a sealed enclosure in which the gas environment is controlled. In particular, the gas environment can consist of an inert gas. In this way, the gas environment in contact with powder 6 does not alter powder 6.

[0012] The powder 6 consists of a powder material (metal powder, ceramic powder, etc.) intended to be consolidated layer by layer by total or partial selective melting. The powder 6 can be spread along a spreading surface 17, which is preferably horizontal and located at the bottom of the enclosure 7.

[0013] 1 and 2, the horizontal plane corresponds to the plane defined by the x-axis and the y-axis, and the vertical direction is given by the z-axis, which is oriented upwards in these figures.

[0014] Melting is carried out using a power source, in this case a laser source 1 configured to generate a laser beam and expose the powder 6 to the laser beam through a window 2 in the enclosure 7. The laser source is used to selectively consolidate areas of the powder exposed to the laser beam. The laser source 1 included in the additive manufacturing apparatus 20 is located outside the enclosure 7, facing a window 2 located in one of the walls of the enclosure 7. The laser source 1 can emit a single laser beam 4, or several laser sources can emit several laser beams simultaneously.

[0015] The window 2 is transparent to the wavelength of the laser beam 4. In this way, little or no energy is lost from the laser beam 4 as it passes through the window 2.

[0016] The window 2 is preferably rectangular and horizontal and is located at the top of the enclosure 7 facing the powder 6 .

[0017] The enclosure 7 is configured to generate an exhaust gas flow 15 over the powder 6. This gas flow is designed to exhaust laser fumes generated during powder melting. For example, the exhaust flow 15 is a laminar flow of inert gas generated inside the enclosure 7 over the powder 6. In particular, the exhaust flow 15 flows over the powder 6 and has a flow rate high enough to carry away laser fumes generated during powder melting, but low enough not to displace the powder 6. The gas flow 15 has a thickness of, for example, 5 millimeters above the powder at a velocity of 1 to 2 meters per second. For example, the gas flow 15 can be generated using two nozzles 13 and 14 arranged inside the enclosure.

[0018] Advantageously, the discharge gas flow 15 is centred on a discharge plane Pe parallel to the powder distribution plane 17. If the distribution plane 17 is horizontal, then the discharge plane Pe is also horizontal.

[0019] The distribution surface 17 is spaced apart from the discharge surface Pe. The discharge flow 15 extends in a direction perpendicular to the discharge surface Pe and reaches a maximum flow rate at the discharge surface or at least in the area surrounding the discharge surface Pe. The flow rate of the discharge flow 15 decreases with increasing distance from the discharge surface Pe in the perpendicular direction. The distance between the distribution surface 17 and the discharge surface Pe is advantageously equal to or less than 4 millimeters. This distance may be between 1 and 4 millimeters, more advantageously between 2 and 3 millimeters.

[0020] The additive manufacturing apparatus 20 further comprises a blowing nozzle 3 and a suction nozzle 8 configured to generate a protective gas flow 18 within the enclosure 7 relative to the window 2 .

[0021] A spray nozzle 3 is understood here as a device for spraying a gas, such as an inert gas. For example, the spray nozzle 3 can be connected to a spray manifold 10 via a spray fan 5.

[0022] The suction nozzle 8 is understood here as a device for drawing in a gas, such as an inert gas. For example, the suction nozzle 8 can be connected to a suction manifold 11 via a suction fan 9.

[0023] The main direction of the protective gas flow 18 is from the blowing nozzle 3 to the suction nozzle 8. The protective gas flow 18 is preferably a laminar flow of inert gas. The blowing nozzle 3 is inside the enclosure on one side of the window and the suction nozzle 8 is inside the enclosure on the other side of the window, so that both nozzles are inside the enclosure 7 and facing each other.

[0024] Between these two nozzles, a protective gas flow 18 flows against a window inside the enclosure 7 .

[0025] Compared to the prior art, the use of the spray nozzle 3 and the suction nozzle 8 makes it easier to control the characteristics of the protective gas flow, and the window can be more effectively protected from laser fumes. In particular, it is possible to generate a laminar gas flow that can protect larger windows than the prior art. It is also possible to protect the window at a flow rate that is less than the disturbance flow rate. The disturbance flow rate is the flow rate at which the protective flow interferes with the flow of gas within the gas environment of the enclosure 7, such as the diffusion of laser fumes within the enclosure 7 or the exhaust flow 15 flowing against the powder 6.

[0026] 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 and the spray nozzle 3 and the suction nozzle 8 are separated by a horizontal distance, for example along the x-axis.

[0027] The window 2 is located away from the protective surface Pp. The protective flow 18 extends perpendicular to the protective surface Pp and reaches its maximum flow rate within the protective surface Pp, or at least within the area surrounding the protective surface Pp. The flow rate of the protective flow Pp decreases with increasing perpendicular distance from the protective surface Pp. The distance between the protective surface Pp and the window 2 is preferably 30 millimeters or less. This distance may be 5 to 25 millimeters, more preferably 7 to 15 millimeters. The closer the nozzles 3 and 8 are positioned to the window 2, the easier it is to achieve a laminar flow of the protective flow 18. The lower the protective flow rate, the more laminar the protective flow 18 becomes. In this way, the window can be protected from laser fumes at a flow rate further away from the disturbance flow rate.

[0028] The blowing nozzle 3 is configured to blow a blowing flow rate ds, and the suction nozzle 8 is configured to draw in a suction flow rate da. Advantageously, the blowing flow rate ds is selected to be strictly greater than the suction flow rate da. This prevents the suction nozzle from drawing in laser fumes from the laser melting process. In this situation, only a portion of the flow blown by the blowing nozzle is drawn in by the suction nozzle. A portion of the blown air flow leaves the area, in particular the window. Thus, there is a component of a protective flow 18 that further pushes the laser fumes away from the window.

[0029] A further fluid circulation system within the enclosure 7 can draw air into the enclosure so that the part of the flow sprayed by the spray nozzle that is not drawn in by the suction nozzle does not interfere with the average pressure inside the enclosure and, more generally, with the circulation of gas within the enclosure.

[0030] If the spray flow rate ds is selected to be greater than the suction flow rate da, the ratio ds / da of the spray flow rate to the suction flow rate is advantageously selected to be greater than or equal to 1.3 and less than or equal to 3.0. In particular, the ratio can be adjusted according to the shape of the window and the length separating the spray nozzle 3 and the suction nozzle 8; if this length increases, a lower ratio ds / da can be selected.

[0031] As an option for the spray nozzle, the fluid sprayed through the spray nozzle can be sprayed at a spray velocity of 1 meter / s or more and at a pressure higher than the average pressure in the enclosure. For this purpose, the spray nozzle 3 can be connected to a spray manifold 5, the pressure of which is higher than the pressure prevailing in the enclosure 7 and allows a spray velocity of 1 meter / s or more.

[0032] As an alternative to the suction nozzle, the fluid drawn in by the suction nozzle may be drawn in at a suction speed of 0.5 meters / second or less and at a pressure lower than the average pressure in the enclosure. To this end, the suction nozzle 8 may be connected to a suction manifold 9, the pressure of which is lower than the pressure prevailing in the enclosure 7 and which allows a suction speed of 0.5 meters / second or less.

[0033] In one embodiment, the apparatus 20 includes a filtration system 12 configured to filter the fluid drawn in by the suction nozzle and supply the filtered fluid to the spray nozzle. In other words, the filtration system 12 forms a gas circulation loop for the protection flow 18. After being filtered, the gas drawn in by the suction nozzle 8 is recirculated to the spray nozzle 3, which sprays the gas against the window 2.

[0034] In this embodiment, a blowing fan 10 fluidly connected to the blowing nozzles 3 via a blowing manifold 5, as previously described; As mentioned above, a suction fan 11 fluidly connected to the suction nozzle 8 via a suction manifold 9 may be used.

[0035] In this case, the blowing fan 10 may be fluidly connected to the outlet of the filtration system 12 and the suction fan 11 may be fluidly connected to the inlet of the filtration system 12 .

[0036] A primary fan 21 may also be added to ensure a minimum flow rate within the gas circulation loop of the protection flow 18. For example, the primary fan is fluidly connected to the outlet of the filtration system 12.

[0037] 1 , the filtration system 12 can also be configured to filter fluid from the exhaust gas stream 15 flowing against the powder 6. For this, two nozzles 13 and 14 generating the exhaust gas stream 15 are fluidly connected to the filtration system 12. One of the nozzles 13 and 14 is fluidly connected to an inlet of the filtration system 12, and the other of the nozzles 13 and 14 is fluidly connected to an 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 spray nozzle 3 via a spray manifold and, on the other hand, to one of the nozzles 13 and 14 generating the exhaust gas stream 15.

[0038] The window 2 can extend over a first width in one direction, and the suction nozzle and the blowing nozzle are configured to generate a protective flow over a second width in that direction, the second width being equal to or greater than the first width.

[0039] The above-mentioned directions can be described as transverse directions, i.e. directions perpendicular to the main direction of the protective flow, in which the spray nozzle 3 and the suction nozzle 8 face each other.

[0040] Preferably, the window 2 is rectangular, with the cross flow direction and the main flow direction corresponding to the sides of the rectangle formed by the window.

[0041] When the window 2 is horizontal, the transverse direction is horizontal. When the spray nozzle 3 and the suction nozzle 8 are separated by a horizontal distance along the x-axis, the transverse direction is parallel to the y-axis, as shown in FIG.

[0042] To ensure that the second width is greater than or equal to the first width, it is possible, for example, to select suction nozzles and spray nozzles that extend transversely along a third width that is greater than the first width of the window.

[0043] In a first variant, the flow rate of the protective gas flow is uniform across the second width. In other words, when a transversely directed segment is selected through the protective gas flow, the flow rate at each point of this segment remains constant or substantially constant. Constant or substantially constant is intended to mean that the relative difference in flow rate between two points of the second width is 5% or less.

[0044] In the second variant, the flow rate of the protective gas flow is variable across the second width; more precisely, the flow rate increases with distance from the center of the window. In other words, when a transversely oriented segment through the protective gas flow is selected, the flow rate at each point on this segment varies along the segment. The flow rate is smallest at the center point of the segment, which corresponds to the center of the window. The flow rate increases on both sides of this center point. The center of the window is understood to mean the central direction of the window, which is oriented along the main flow direction and perpendicular to the transverse direction. The central direction passes through the center of the window. For example, with reference to FIG. 2, if window 2 is rectangular, the central direction Dc passes through the center of the rectangle and is parallel to two of the rectangle's sides, which is one of the rectangle's axes of symmetry.

[0045] Additive Manufacturing Methods An additive manufacturing apparatus 20 of the type described above can be used to implement an additive manufacturing method comprising the following steps:

[0046] In a first step, an exhaust gas flow 15 is generated over the powder 6 contained in the enclosure 7. This flow is intended to exhaust the laser fumes generated during the melting of the powder 6.

[0047] In a second step, the powder 6 is exposed to a laser beam generated by the laser source 1 through the window 2 in the enclosure 7. This step provides the powder 6 with enough energy to cause it to consolidate. Laser fumes may be emitted from the powder 6, which are then carried away by the exhaust gas flow 15. However, the exhaust flow 15 cannot remove all of the laser fumes from the enclosure.

[0048] In a third step, a protective gas flow 18 is generated within the enclosure 7 against the window 2, this flow being generated by the spray nozzle 3 and the suction nozzle 8. The protective gas flow 18 flows against the window 2 and keeps away from the window 2 any laser fumes that are not removed from the enclosure by the protective gas flow.

[0049] The terms first step, second step, and third step are used herein to describe actions performed during a method, but are not limited to any particular time sequence between them. In particular, these steps may be performed simultaneously.

[0050] Optionally, the spray nozzle 3 sprays a spray flow rate ds and the suction nozzle 8 draws in a suction flow rate da, the spray flow rate being strictly greater than the suction flow rate.

[0051] The ratio ds / da of the spray flow rate to the suction flow rate can be selected to be 1.3 or more and 3.0 or less.

[0052] Preferably, the spray nozzle 3 sprays the spray flow rate at a spray velocity of 1 meter / second or greater and at a pressure higher than the average pressure within the enclosure.

[0053] Preferably, the suction nozzle 8 draws a suction flow at a velocity of 0.5 meters / second or less and at a pressure less than the average pressure within the enclosure.

[0054] In one embodiment, the method includes filtering fluid drawn through the suction nozzle 8 and spraying the filtered fluid through the spray nozzle 3. The apparatus 20 includes a filtration system 12 as described above.

[0055] In a first variant, as described above, the window 2 extends over a first width in one direction, the gas flow has a uniform flow rate over a second width in that direction, the second width being equal to or greater than the first width, and the relative difference in flow rate between two points in a third width being 5% or less.

[0056] In a second variation, as described above, the window extends over a first width in one direction, and the gas flow has a flow rate over a second width in that direction, the second width being equal to or greater than the first width, and the flow rate increasing with distance from the center of the window.

Claims

1. An additive manufacturing apparatus (20), comprising: an enclosure (7) configured to contain a powder (6) and to generate an exhaust gas flow (15) relative to said powder (6); a laser source (1) configured to generate a laser beam and expose said powder (6) to said laser beam through a window (2) of said enclosure (7); - a blowing nozzle (3) and a suction nozzle (8) configured to generate a protective gas flow (18) inside the enclosure (7) against the window (2), An additive manufacturing apparatus (20), wherein the spray nozzle (3) is configured to spray a spray flow rate and the suction nozzle (8) is configured to draw a suction flow rate, the spray flow rate being strictly greater than the suction flow rate.

2. 2. The device according to claim 1, wherein the discharge gas flow (15) is centered on a discharge plane (Pe) parallel to a distribution plane (17) of the powder (6) remote from the discharge plane (Pe).

3. 3. The device according to claim 1 or 2, wherein the protective gas flow (18) is parallel to the window (2) and is centered on a protective surface (Pp) at a distance from the protective surface (Pp), the protective surface (Pp) being advantageously spaced from the window (2) by a distance of 30 millimeters or less.

4. 4. The device according to claim 1, wherein the ratio of the spray flow rate to the suction flow rate is 1.3 or more and 3.0 or less.

5. The spray nozzle (3) is - at a speed of 1 meter / s or more, 5. The device according to claim 1, wherein the device is configured to deliver a blast flow at a pressure higher than the average pressure in the enclosure (7).

6. The suction nozzle (8) - at a speed of 0.5 meters per second or less, 6. The device according to any one of claims 1 to 5, wherein the device is configured to draw an aspiration flow at a pressure lower than the average pressure in the enclosure (7).

7. 7. The device according to any one of claims 1 to 6, comprising a filtration system (12) configured to filter the fluid drawn in by the suction nozzle (8) and to supply the filtered fluid to the spray nozzle (3).

8. 8. The device according to claim 1, wherein the window (2) extends over a first width in one direction (y), and the suction nozzle (3) and the blowing nozzle (8) are configured to generate the protection flow (18) over a second width in said direction (y), the second width being equal to or greater than the first width.

9. 9. The device according to claim 8, wherein the suction nozzle (3) and the spray nozzle (8) are configured so that the protective gas flow (18) has a uniform flow rate across the second width, and the relative difference in flow rate between two points on the second width is not more than 5%.

10. 9. The device according to claim 8, wherein the suction nozzle (3) and the spray nozzle (8) are configured such that the protective gas flow (18) has a flow rate that increases with distance from the center of the window (2).

11. 1. An additive manufacturing method comprising: - generating an exhaust gas flow (15) over a powder (6) contained in an enclosure (7); - exposing said powder (6) to a laser beam generated by a laser source (1), said beam passing through a window (2) in said enclosure (7); - generating a protective gas flow (18) in the enclosure (7) against the window (2), said flow being generated by a spray nozzle (3) and a suction nozzle (8), said spray nozzle (3) spraying a spray flow rate and said suction nozzle (8) drawing in a suction flow rate, said spray flow rate being strictly greater than said suction flow rate.

12. 12. The method according to claim 11, wherein the ratio of the spray flow rate to the suction flow rate is 1.3 to 3.0, and preferably the spray nozzle (3) sprays the spray flow rate with a spray velocity of 1 meter / s or more and at a pressure higher than the average pressure in the enclosure (7), and preferably the suction nozzle (8) draws in the suction flow rate with a suction velocity of 0.5 meters / s or less and at a pressure lower than the average pressure in the enclosure (7).

13. 13. A method according to claim 11 or 12, comprising the steps of filtering the fluid drawn through the suction nozzle (8) and spraying the filtered fluid through the spray nozzle (3).

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

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

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