METHODS AND MULTI-PURPOSE POWDER REMOVAL FEATURES FOR ADDITIVE MANUFACTURING

Abstract

The present disclosure generally relates to methods for additive manufacturing (AM) for fabricating multi-walled structures. A multi-walled structure includes a first wall having a first surface and a second wall having a second surface facing the first surface to define a passage having a width between the first surface and the second surface in a first direction. The multi-walled structure also includes an enlarged powder removal feature connecting the first wall and the second wall. The enlarged powder removal feature has an inner dimension greater than the width in the first direction and at least one open end in a direction transverse to the first width.

Claims

1. A method for fabricating an object, comprising: (a) irradiating a layer of powder in a powder bed with an energy beam in a series of scan lines to form a fused region; (b) providing a subsequent layer of powder over the powder bed by passing a recoater arm over the powder bed from a first side of the powder bed to a second side of the powder bed; and (c) repeating steps (a) and (b) until the object is formed in the powder bed, wherein the object includes: a first wall having a first surface, a second wall having a second surface facing the first surface to define a passage having a width between the first surface and the second surface in a first direction, and an enlarged powder removal feature connecting the first wall and the second wall, the enlarged powder removal feature having an inner dimension greater than the width in the first direction and at least one open end in a direction transverse to the first width.

2. The method of claim 1, further comprising: (d) removing unfused powder from the passage via the at least one open end.

3. The method of claim 2, further comprising: (e) passing an elongated object through the powder removal feature.

4. The method of claim 1, wherein the powder removal feature connects a first end of the first wall to a first end of the second wall.

5. The method of claim 4, wherein the object further includes a second enlarged powder removal feature connecting a second end of the first wall to a second end of the second wall.

6. The method of claim 1, wherein the width is substantially constant across the first surface and the second surface.

7. The method of claim 1, wherein the object includes a plurality of regularly spaced powder removal features.

8. The method of claim 1, wherein the powder removal feature is a hollow column defined by a semi-annular wall, wherein the hollow column is in fluid communication with the passage.

9. The method of claim 1, wherein the at least one open end is located at a longitudinal end of the hollow column.

10. The method of claim 1, wherein the object is annular, the first wall is an outer wall of an arcuate portion of the object, and the second wall is an inner wall of the arcuate portion of the object.

11. The method of claim 1, wherein the powder removal feature is a non-linear tube defined by a semi-annular wall connected to the first wall and the second wall.

12. An engine component, comprising: a first wall having a first surface; a second wall having a second surface facing the first surface to define a passage having a width between the first surface and the second surface in a first direction, and an enlarged powder removal feature connecting the first wall and the second wall, the enlarged powder removal feature having an inner dimension greater than the width in the first direction and at least one open end in a direction transverse to the first width.

13. The engine component of claim 12, wherein the powder removal feature connects a first end of the first wall to a first end of the second wall.

14. The engine component of claim 13, further comprising a second enlarged powder removal feature connecting a second end of the first wall to a second end of the second wall.

15. The engine component of claim 12, wherein the width is substantially constant across the first surface and the second surface.

16. The engine component of claim 12, wherein the engine component includes a plurality of regularly spaced powder removal features.

17. The engine component of claim 12, wherein the powder removal feature is a hollow column defined by a semi-annular wall, wherein the hollow column is in fluid communication with the passage.

18. The engine component of claim 12, wherein the at least one open end is located at a longitudinal end of the hollow column.

19. The engine component of claim 12, wherein the engine component is annular, the first wall is an outer wall of an arcuate portion of the engine component, and the second wall is an inner wall of the arcuate portion of the engine component.

20. The engine component of claim 12, wherein the powder removal feature is a non-linear tube defined by a semi-annular wall connected to the first wall and the second wall.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIG. 1 is schematic diagram showing an example of a conventional apparatus for additive manufacturing.

[0012] FIG. 2 illustrates an example of a multi-walled structure without powder removal features.

[0013] FIG. 3 illustrates an example of a multi-walled structure with powder removal holes.

[0014] FIG. 4 illustrates a plan view of an example of a multi-walled structure with powder removal features according to an aspect of the present disclosure.

[0015] FIG. 5 illustrates a cross-sectional view of the multi-walled structure of FIG. 4.

[0016] FIG. 6 illustrates another example of a multi-walled structure with powder removal features according to an aspect of the present disclosure

[0017] FIG. 7 illustrates an example of an annular multi-walled structure with powder removal features according to an aspect of the present disclosure.

[0018] FIG. 8 illustrates an example of an annular multi-walled structure with non-linear powder removal features according to an aspect of the present disclosure.

[0019] FIG. 9 illustrates a cross-sectional view of the annular multi-walled structure of FIG. 8.

DETAILED DESCRIPTION

[0020] The detailed description set forth below in connection with the appended drawings is intended as a description of various configurations and is not intended to represent the only configurations in which the concepts described herein may be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. In some instances, well known components are shown in block diagram form in order to avoid obscuring such concepts.

[0021] FIGS. 2 illustrates a multi-walled structure 200 including a first wall 210 and a second wall 220 that define a passage 230 between the first wall 210 and the second wall 220. The multiple walls provide various advantages over a single solid wall. Generally, the multi-walled structure 200 has lower weight than a similar solid structure due to the passage 230 between the walls 210, 220 while having similar strength and rigidity characteristics. Moreover, the passage 230 provides a degree of insulation from heat and vibration applied to one of the walls 210, 220. Further, the passage 230 may be used as a flow passage for a fluid in some components.

[0022] The multi-walled structure 200 may pose some problems for fabrication using additive manufacturing. The passage 230 may retain unfused powder that may be difficult to remove. In some cases, the passage 230 may be completely enclosed preventing removal of the unfused powder. In other cases, the relatively narrow shape of the passage 230 may allow unfused powder to resist extraction techniques (e.g., pressurized air, vacuum, solvents, etc.).

[0023] FIG. 3 illustrates a multi-walled structure 300 including powder removal holes 340. The multi-walled structure 300 may be similar to the multi-walled structure 200 with wall 310 corresponding to wall 210, wall 320 corresponding to wall 220, and passage 330 corresponding to passage 230. The powder removal holes 340 may be located in a surface of one of walls 310, 320. The powder removal holes 340 provide one approach to removing powder from the passage 330. The powder removal holes 340 may be built into the multi-walled structure 300 during the additive manufacturing process, or machined using a subtractive manufacturing process (e.g., drilling). The powder removal holes 340 allow removal of unfused powder, for example, by providing a passage for the unfused powder to exit the passage 330. The powder removal holes 340 also provide a point to inject pressurized air or a solvent to facilitate removal of the unfused powder. The powder removal holes 340, however, may also result in undesirable effects. For example, the powder removal holes 340 may be located in a surface of the wall 320. The powder removal holes 340 may weaken the structure of the wall 320. The powder removal holes 340 may be filled (e.g., using weld filling or welding a plug within the powder removal holes 340. Such techniques, however, may be time consuming or result in undesirable component properties (e.g., uneven finish). Additionally, in some cases, powder removal holes 340 may be ineffective for multi-walled structures where there is no direct access to a passage 330.

[0024] FIGS. 4 and 5 illustrate a multi-walled structure 400 according to an aspect of the present disclosure. FIG. 4 illustrates an end view of the multi-walled structure 400. FIG. 5 illustrates a cross-section of the multi-walled structure 400 along the line A-A. The multi-walled structure 400 may be, for example, an engine component, a structural member for a vehicle, a medical device, or a solid structure for another use. The multi-walled structure 400 includes a wall 410 and a wall 420 defining a passage 430 between the walls 410, 420. In an aspect, the multi-walled structure 400 is an annular structure and the wall 410 and the wall 420 are substantially concentric arc shaped walls. The wall 410 includes a surface 412. The wall 420 includes a surface 422. As illustrated, the surface 412 is a radially inward surface of the wall 410 and the surface 422 is a radially outward surface of the wall 420. The passage 430 extends between the surface 412 and the surface 422. The passage 430 has a width 432 that is substantially constant. That is, the surface 412 conforms to the surface 422 such that the width 432 measured along any line normal to the surfaces 412, 422 is substantially the same (e.g., within 10 percent) for a majority of the surfaces 412, 422.

[0025] The multi-walled structure 400 also includes a powder removal feature 440. The powder removal feature 440 is a region adjacent the walls 410, 420 having an expanded inner dimension 442. The powder removal feature 440 is in fluid communication with the passage 430. As illustrated in FIG. 4, a semi-annular wall 444 of the powder removal feature 440 defines a hollow cylindrical column filled with unfused powder. The inner dimension 442 is an inner diameter of the semi-annular wall 444. The semi-annular wall 444 connects the wall 410 and the wall 420. Although illustrated as semi-annular, it should be appreciated that different shapes may be used to connect the wall 410 and the wall 420 wall. As best seen in FIG. 5, the inner dimension 442 is greater than the width 432. For example, the inner dimension 442 may be twice the width 432. The inner dimension 442 may also be sized to accommodate an elongated object such as a tool, tube, wire, or cable passing through the powder removal feature 440 during post processing or operation of the multi-walled structure 400. The semi-annular wall 444 forms a bulge 446 that extends beyond the wall 420. The bulge 446 provides additional structural support and rigidity for the multi-walled structure 400 by increasing the outer diameter of the powder removal feature 440. As illustrated in FIG. 4, the bulge 446 extends radially inward from the wall 420.

[0026] In an aspect, the use of additive manufacturing allows the multi-walled structure 400 to be fabricated with relatively more precision than prior art manufacturing methods (e.g., casting). For example, the walls 410, 420 may be less than 0.050 inches thick, and even approximately 0.020 inches thick. The width 432 may be selected based on design needs for the multi-walled structure 400. The width 432 may be a small as 0.005 inches. Generally, the smaller the width 432, the larger the inner diameter of the powder removal feature 440 is selected to allow powder removal from the passage 430. The powder removal feature 440 has a longitudinal axis. During fabrication, the longitudinal axis may be aligned with the build direction (e.g., up) such that the powder removal feature is supported by lower layers of the powder removal feature without overhanging edges. In cases where the multi-walled structure is shaped such that the powder removal feature does not have a straight longitudinal axis, the multi-walled structure may be oriented to minimize overhanging edges, or support structures may be added.

[0027] FIG. 6 illustrates another multi-walled structure 600. The multi-walled structure 600 is part of an annular component. The multi-walled structure 600 includes multiple powder removal features 640 that divide the annular component into several arc shaped segments 602. Each arc shaped segment 602 has a powder removal feature 640 at each end such that a pair of powder removal features 640 are located adjacent each other between the arc shaped segments 602. In an aspect, the number, spacing, and dimensions of the powder removal features are selected to facilitate powder removal and meet strength and rigidity parameters. The use of multiple powder removal features 640 limits the length of the passages 630 such that powder can be removed via the powder removal features 640. Additionally, as illustrated in FIG. 6, the bulges 646 protrude radially outward from the wall 610 in contrast to the radially inward bulges 446 in FIG. 4. The inner wall 620 extends across several of the arc shaped segments, while each arc shaped segment has a separate outer wall 610. The bulges may also protrude from both of the walls 610, 620.

[0028] FIG. 7 illustrates another multi-walled structure 700. The multi-walled structure 700 includes concentric arc shaped walls 710, 720, and 730. First spaces 740 are located between walls 710 and walls 720. Second spaces 750 are located between walls 720 and 730. Powder removal features 760 are located at the ends of the first spaces 740. The powder removal features 760 connect a wall 710 to a wall 720. The powder removal features 760 extend radially outward beyond the walls 710. Powder removal features 770 are located at the ends of the second spaces 750. The powder removal features 770 connect a wall 720 to a wall 730. The powder removal features 770 extend radially inward beyond the wall 730. The powder removal features 770 are offset from the powder removal features 760.

[0029] FIGS. 8 and 9 illustrate a multi-walled structure 800 having non-linear powder removal features 840. FIG. 8 is a perspective view. FIG. 9 is a radial cross-section along the line B-B. The multi-walled structure 800 includes an outer wall 810, an inner wall 820, and a space 830 between the outer wall 810 and the inner wall 820. The outer wall 810 includes a curved portion 812, which extends radially outward from the rest of outer wall 810. The inner wall 820 includes a similar curved portion 822 conforming to the shape of the curved portion 812. The non-linear powder removal feature 840 is a tube formed by a semi-annular wall 844 that connects the outer wall 810 and the inner wall 820. The non-linear powder removal feature 840 may include a linear portion and a curved portion. The non-linear powder removal feature 840 has a substantially constant inner dimension 842, which is greater than a width 832 of the space 830. For example, the inner dimension (e.g., a diameter) may vary by up to 10% over the length of the powder removal feature.

[0030] Upon completion of the AM process, the multi-walled structure 400/600/700/800 may be removed from the powder bed. Unfused powder is then removed from the multi-walled structure 400/600/700/800. In an aspect, the multi-walled structure 400/600/700/800 is attached to the build plate and may be detached from the build plate before or after powder removal. At least one end of the powder removal features 440/640/760/770/840 is exposed. The powder removal features 440/640/760/770/840 facilitate removal of unfused powder from the respective multi-walled structure 400/600/700/800. For example, during a powder removal procedure, the multi-walled structure 400/600/700/800 is placed on a vibration table and vibrated. The vibrations loosen compacted powder to facilitate removal via powder removal features 440/640/760/770/840. The multi-walled structure 400/600/700 may be also rotated during vibration such that gravity draws the unfused powder toward one of the powder removal features 440/640/760/770/840. For example, the multi-walled structure 800 may be rotated such that the unfused powder follows the path of the non-linear powder removal feature 840. Additionally, compressed gas and/or vacuum may be used to remove the loose powder. For example, compressed gas may be supplied at a powder removal feature 440/640/760/770 at one end of a passage 430/630/740/750/830 and vacuum may be applied at the powder removal feature 440/640/760/770/840 located at the other end of the passage. Accordingly, the combination of compressed gas and vacuum may urge the unfused powder toward one of the powder removal features.

[0031] Additionally, the powder removal features 440/640/760/770/840 provide a conduit through the multi-walled structures 400/600/700/800 in operation. For example, when the multi-walled structure 400 is an aircraft component, the powder removal feature 440 and passage 430 may be used to route a flow of air to another component. Further, the powder removal feature 440 may be used to route an elongated object that may not fit within the passage 430. For example, a wire, fuel hose, or cable may be passed through the powder removal feature 440.

[0032] This written description uses examples to disclose the invention, including the preferred embodiments, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims. Aspects from the various embodiments described, as well as other known equivalents for each such aspect, can be mixed and matched by one of ordinary skill in the art to construct additional embodiments and techniques in accordance with principles of this application.