WO2021138275A1

WO2021138275A1 - Additive manufacturing with an electron beam array

Info

Publication number: WO2021138275A1
Application number: PCT/US2020/067196
Authority: WO
Inventors: Michael James HOGANSON; Andrius Juozas RAULINAITIS; Eric Yang
Original assignee: Divergent Technologies, Inc.
Priority date: 2019-12-31
Filing date: 2020-12-28
Publication date: 2021-07-08
Also published as: CN115190839A; EP4084945A4; EP4084945A1

Abstract

Aspects are provided for a plurality of electron beam sources for powder bed fusion (PBF) systems. A PBF apparatus may include a structure that supports a layer of feedstock, and a plurality of electron beam sources that each generate an electron beam to fuse one or more areas of the layer of feedstock. The PBF apparatus may also include a plurality of deflectors that individually steer the electron beams to concurrently fuse multiple areas of the layer of feedstock. The plurality of electron beam sources may be scalable to accommodate structures of different sizes.

Description

ADDITIVE MANUFACTURING WITH AN ELECTRON BEAM ARRAY

CROSS REFERENCE TO RELATED APPLICATION(S)

[0001] This application claims the benefit of U.S. Provisional Application Serial No.

62/955,778, entitled “ADDITIVE MANUFACTURING WITH AN ELECTRON BEAM ARRAY” and filed on December 31, 2019, which is expressly incorporated by reference herein in its entirety.

BACKGROUND

Field

[0002] The present disclosure relates generally to powder-bed fusion (PBF) systems, and more particularly, to arrays of energy beam sources in PBF systems.

Background

[0003] PBF systems can produce structures, referred to as build pieces, with geometrically complex shapes, including some shapes that are difficult or impossible to create with conventional manufacturing processes. PBF systems create build pieces layer by layer. Each layer or ‘slice’ is formed by depositing a layer of powder and exposing portions of the layer to an energy beam. The energy beam is applied to melt areas of the powder layer that coincide with the cross-section of the build piece in the layer. The melted powder cools and fuses to form a slice of the build piece. Each layer is deposited on top of the previous layer. The resulting structure is a build piece assembled slice-by-slice from the ground up.

SUMMARY

[0004] Several aspects of apparatuses for PBF systems including a plurality of electron beam sources will be described more fully hereinafter.

[0005] In various aspects, an apparatus for powder-bed fusion may include a structure that supports a layer of feedstock, and a plurality of electron beam sources that each generate an electron beam to fuse one or more areas of the layer of feedstock.

[0006] In various aspects, an apparatus for powder-bed fusion may include a structure that supports a layer of feedstock, a plurality of electron beam sources that each generate an electron beam, and a plurality of deflectors that individually steer the electron beams to concurrently fuse multiple areas of the layer of feedstock.

[0007] In various aspects, an apparatus for powder-bed fusion may include a structure that supports a layer of feedstock, an array of electron beam sources that each generate an electron beam, and an array of deflectors that steer the electron beams to fuse one or more areas of the layer of feedstock, where the plurality of electron beam sources is scalable to accommodate structures of different sizes.

[0008] Other aspects will become readily apparent to those skilled in the art from the following detailed description, wherein is shown and described only several embodiments by way of illustration. As will be realized by those skilled in the art, concepts herein are capable of other and different embodiments, and several details are capable of modification in various other respects, all without departing from the present disclosure. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not as restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Various aspects of will now be presented in the detailed description by way of example, and not by way of limitation, in the accompanying drawings, wherein:

[0010] FIGs. 1A-1D illustrate an example PBF system including a plurality of energy beam sources during different stages of operation.

[0011] FIG. 2 illustrates an example energy beam source and deflector system for one of the plurality of energy beam sources of FIGs. 1A-1D.

[0012] FIG. 3 illustrates a perspective view of an example PBF system including arrays of energy beam sources and deflectors.

[0013] FIGs. 4A-4B illustrate diagrams of example polygonal shape layouts for the PBF system of FIG. 3.

DETAILED DESCRIPTION

[0014] The detailed description set forth below in connection with the appended drawings is intended to provide a description of various exemplary embodiments of the concepts disclosed herein and is not intended to represent the only embodiments in which the disclosure may be practiced. The term “exemplary” used in this disclosure means “serving as an example, instance, or illustration,” and should not necessarily be construed as preferred or advantageous over other embodiments presented in this disclosure. The detailed description includes specific details for the purpose of providing a thorough and complete disclosure that fully conveys the scope of the concepts to those skilled in the art. However, the disclosure may be practiced without these specific details. In some instances, well-known structures and components may be shown in block diagram form, or omitted entirely, in order to avoid obscuring the various concepts presented throughout this disclosure.

[0015] In a PBF system, a single energy beam source may additively manufacture a build piece by emitting an energy beam to melt various areas of a powder layer. The melted areas corresponding to a cross-section of the build piece are allowed to cool, and the energy beam source repeats the process layer-by-layer until the build piece is additively manufactured.

[0016] However, the efficiency of the additive manufacturing process may be limited by the single energy beam source. For example, using a single energy beam source may only allow one part to be built at a time. A single energy beam source may also have a limited work envelope ( e.g . a range of movement of the energy beam) and/or cause the PBF system to have a limited build envelope (e.g. a maximum print volume corresponding to a size of the build plate). Thus, typically only parts that fit within this limited work envelope or build envelope (e.g. small parts) may be built at one time. As a result, in order to build a large part such as a subassembly for a vehicle using a single energy beam source, typically a number of small parts fitting within the build volume must be defined, individually printed at different times, and joined to form the larger part or subassembly. Such additive manufacturing process may result in significant cycle time for completion of larger parts.

[0017] To increase the build envelope (and work envelope) and improve the cycle time, the present disclosure provides a PBF system which includes a plurality of energy beam sources that may concurrently generate energy beams to additively manufacture one or more parts of an object. The plurality of energy beam sources may emit individually controllable energy beams, for example, electron beams, which may be steered by deflectors to fuse one or more areas of a layer of a powder bed on a structure (e.g. the build plate). For example, the deflectors may each provide an electromagnetic field which steers a respective electron beam to separate areas of the powder bed to concurrently build separate parts, and/or to a common area of the powder bed to concurrently build a single part. The energy beam sources may be arranged in a two-dimensional (2D) group (or array) a common distance away from the structure in order to process the material across the entire powder bed into the part(s). The energy beam sources may be scalable ( e.g . to include any number of energy beam sources, subject to physical power limitations), thereby allowing the energy beam sources to accommodate any size of work envelope or build envelope for the PBF system.

[0018] FIGs. 1A-1D illustrate an example PBF system 100 including a plurality of energy beam sources during different stages of operation. PBF system 100 can include a depositor 101 that can deposit each layer of metal powder, a plurality of energy beam sources 103 that can each generate an energy beam, a plurality of deflectors 105 that can individually apply the energy beam to fuse the powder material, and a build plate 107 that can support one or more build pieces, such as the build pieces 109a, 109b, 109c. PBF system 100 can also include a build floor 111 positioned within a powder bed receptacle. The walls of the powder bed receptacle are shown as powder bed receptacle walls 112. Build floor 111 can lower build plate 107 so that depositor 101 can deposit a next layer and a chamber 113 that can enclose the other components. Depositor 101 can include a hopper 115 that contains a powder 117, such as a metal powder, and a level er 119 that can level the top of each layer of powder.

[0019] Referring specifically to FIG. 1A, this figure shows PBF system 100 after a slice of build pieces 109a, 109b, 109c have each been fused, but before the next layer of powder has been deposited. In fact, FIG. 1A illustrates a time at which PBF system 100 has already deposited and fused slices in multiple layers, e.g., 50 layers, to form the current state of build pieces 109a, 109b, 109c, e.g., each formed of 50 slices. The multiple layers already deposited have created a powder bed 121, which includes powder that was deposited but not fused. PBF system 100 can include a temperature sensor 122 that can sense the temperature in areas of the work area, such as the surface of powder bed, build pieces 109a, 109b, 109c, etc. For example, temperature sensor 122 can include a thermal camera directed toward the work area, thermocouples attached to areas near the powder bed, etc.

[0020] FIG. IB shows PBF system 100 at a stage in which build floor 111 can lower by a powder layer thickness 123. The lowering of build floor 111 causes build pieces 109a, 109b, 109c and powder bed 121 to drop by powder layer thickness 123, so that the top of the build pieces and powder bed are lower than the top of powder bed receptacle wall 112 by the powder layer thickness. In this way, for example, a space with a consistent thickness equal to powder layer thickness 123 can be created over the tops of the build pieces and powder bed 121.

[0021] FIG. 1C shows PBF system 100 at a stage in which depositor 101 can deposit powder 117 in the space created over the top of build pieces 109a, 109b, 109c and powder bed 121. In this example, depositor 101 can cross over the space while releasing powder 117 from hopper 115. Leveler 119 can level the released powder to form a powder layer 125 that has a thickness of powder layer thickness 123. It should be noted, that elements of FIGs. 1A-1D and the other figures in this disclosure are not necessarily drawn to scale, but may be drawn larger or smaller for the purpose of better illustration of concepts described herein. For example, the illustrated thickness of powder layer 125 (i.e., powder layer thickness 123) is greater than an actual thickness used for the example 50 previously-deposited layers.

[0022] FIG. ID shows PBF system 100 at a stage in which energy beam sources 103 can generate energy beams 127 and deflectors 105 can individually apply or steer the energy beams to separately fuse the next slice in build pieces 109a, 109b, 109c. For example, energy beam sources 103 may each be an electron beam source, energy beams 127 may each be an electron beam, and deflectors 105 can each include deflection plates that can generate an electromagnetic field that deflects the respective electron beams to scan across areas to be fused. In another example, energy beam sources 103 may each be a laser beam source, energy beams 127 may each be a laser beam, and deflectors 105 may each include an optical system ( e.g . mirrors, prisms, etc.) that can reflect and/or refract the laser beams to scan across areas to be fused. In other examples, energy beam sources 103 and/or deflectors 105 can each modulate the energy beams, e.g., squeeze or narrow the energy beams, expand or widen the energy beams, angle the energy beams, and/or turn the energy beams on and off as the deflectors scan so that the energy beams are applied only in the appropriate areas of the powder layer. For example, in various embodiments, the energy beams can be separately modulated by a digital signal processor (DSP).

[0023] FIG. 2 illustrates an example energy beam source and deflector system, which may correspond to one of the pairs of energy beam sources 103 and deflectors 105 in FIGs. 1A-1D. In this example, the energy beam is an electron beam. The energy beam source can include an electron grid 201, an electron grid modulator 203, and a focus 205. A controller 206 can control electron grid 201 and electron grid modulator 203 to generate an electron beam 207 and can control focus 205 to focus electron beam 207 into a focused electron beam 209. To provide a clearer view in the figure, connections between controller 206 and other components are not shown. Focused electron beam 209 can be scanned across a powder layer 211 within the bounds of an electron beam cone 212 by a deflector 213. Deflector 213 can include two x-deflection plates 215 and two y-deflection plates 217, one of which is obscured in FIG. 2. Controller 206 can control deflector 213 to generate an electric field between x-deflection plates 215 to deflect or steer focused electron beam 209 within electron beam cone 212 along the x-direction and to generate an electric field between y-deflection plates 217 to deflect or steer the focused electron beam along the y-direction. In various embodiments, a deflector can include one or more magnetic coils to deflect the focused electron beam.

[0024] A beam sensor 219 can sense the amount of deflection of focused electron beam 209 and can send this information to controller 206. Controller 206 can use this information to adjust the strength of the electric fields in order to achieve the desired amount of deflection of the focused electron beam. For example, the controller 206 may adjust the position ( e.g . x-deflection and/or y-deflection) and/or size or shape (e.g. narrower or wider) of the focused electron beam using the deflector. The focused electron beam can be applied to powder layer 211 by scanning the focused electron beam to melt loose powder 221, thus forming fused powder 223.

[0025] The energy beam source and deflector system of FIG. 2 may correspond to individual pairs of energy beam sources 103 and deflectors 105 in the example PBF system of FIGs. 1A-1D. For example, a PBF system with nine energy beam sources and deflectors may include nine of the electron grids, electron grid modulators, electron beams, deflectors, beam sensors, electron beam cones, and other components of FIG. 2. Controller 206 may individually control the electron grids and electron grid modulators to generate separate electron beams 207, and the controller can individually control the deflectors to adjust the electron beams into different positions, sizes or shapes. Alternatively, separate controllers may be used to generate and deflect the various electron beams.

[0026] FIG. 3 illustrates a perspective view of a PBF system 300 including an array of electron beam sources 302 which generate electron beams 304 and an array of deflectors 306 which steer the electron beams within the bounds of the electron beam cones shown in the figure to fuse areas 308a, 308b, 308c of a layer of feedstock (e.g. powder) on a structure 310 (e.g. a build plate). A controller (not shown) may control the electron beam sources to generate the electron beams and the deflectors to steer the electron beams. For example, referring to FIGs. 1A-1D and 2, the array of electron beam sources may correspond to energy beam sources 103 and individually to electron grid 201 with electron grid modulator 203, the array of deflectors may correspond to deflectors 105 and individually to deflectors 213, the electron beam cones may individually correspond to electron beam cone 212, the layer of feedstock being fused may correspond to powder layer 125, and the structure may correspond to build plate 107. The array of electron beam sources and the array of deflectors are scalable; that is, although FIG. 3 illustrates nine different electron beam sources and deflectors, the arrays may include any number of electron beam sources and deflectors to accommodate structures (e.g. structure 310) or printers of any size. For example, the PBF system 300 may allow any number of electron beam sources and deflectors to be added to or subtracted from the array.

[0027] Array of electron beam sources 302 may be arranged across from the structure 310 in a 2D arrangement. For example, as illustrated in FIG. 3, the arrays of electron beam sources may be arranged at a common distance 312 across from structure 310. The common distance 312 may be configured based on the size of the work envelope or build envelope required. For example, as electrons in an electron beam repel a greater distance from each other the farther away they travel from their source (e.g. thus forming an electron beam cone), the cross-sectional area of the base of each electron beam cone may increase proportionally to the distance of the electron beam source from the structure. Thus, common distance 312 may be selected to be a minimum height at which point the cross-sectional areas of the generated electron beam cones may together encompass the entirety of structure 310 (thereby maximizing work envelope and build envelope). However, the resolution and energy density of the electron beam may also decrease the farther away the electron beam source is located from the structure. Depending on whether fine or coarse powders are used for the feedstock, or the type or area of the part to be printed, the resolution or energy density may need to be adjusted. Therefore, the common distance 312 of the electron beam sources may also be selected to be a maximum height for encompassing the entirety of structure 310 while also accommodating the resolution or energy density required. The common distance 312 may be preconfigured or fixed, or the controller may dynamically adjust common distance 312, based on the work envelope or build envelope, the part or the area to be fused, and/or the feedstock type as described above.

[0028] To maximize the work envelope and build envelope of the energy beam sources, the controller may control the magnetic fields of the deflectors to steer the energy beams such that they overlap at fused areas to prevent gaps between the areas. For example, as illustrated in FIG. 3, the deflectors may steer electron beams 304 such that the electron beam cones encompass all fused areas 308a, 308b, 308c with overlap to prevent gaps when forming the part(s). The controller may also similarly control the energy beam sources, for example, by adjusting the common distance 312 or turning off or on energy beam sources, to control overlap of the electron beam cones and prevent gaps between the areas. However, unlike laser beams where photons do not interact with each other, electron beams may interact due to magnetic field effects between separate deflectors and electron repulsion between separate electron beams. Therefore, the electron beam sources or deflectors may be controlled to limit interaction of the magnetic fields and/or minimize overlap of the electron beam cones. For example, the positioning of the electron beam sources or deflectors may be statically configured or dynamically moved by the controller to reduce magnetic field interaction. In another example, magnetic shielding may be incorporated into the deflectors ( e.g . statically or dynamically by the controller). Additionally, the controller may adjust certain deflectors to alter the shape or orientation of respective electron beams to reduce electron repulsion between beams.

[0029] The electron beam sources may also be distributed across structure 310 to concurrently fuse multiple areas of the layer of feedstock. For example, as illustrated in FIG. 3, array of electron beam sources 302 and array of deflectors 306 may be distributed above the build plate such that electron beams 304 concurrently fuse areas 308a, 308b, and 308c of the layer of powder on the build plate. The controller may control the deflectors to steer the respective energy beams to simultaneously fuse the different areas to form separate parts (e.g. as illustrated in FIGs. 1A-1D). For instance, one part (e.g. build piece 109a) may be built in area 308a, another part (e.g. build piece 109b) may be built in area 308b, and another part (e.g. build piece 109c) may be built in area 308c. Alternatively, the controller may control the deflectors to steer the respective energy beams to simultaneously fuse the different areas to form a single part which spans across areas 308a-c. Additionally, the controller may control the deflectors to steer the respective energy beams to simultaneously fuse a common area of the layer of feedstock. For example, the controller may control at least a subset of the deflectors, or even all of the deflectors, to steer the respective energy beams to fuse only a subset of the areas 308a, 308b, 308c (for example, to all fuse only area 308b).

[0030] FIGs. 4A and 4B illustrate top views of example layouts for printing parts using the example PBF system of FIG. 3. Specifically, FIG. 4A illustrates a portion of a layout 400 in which square areas 402 of a powder layer are concurrently fused by electron beams scanning within electron beam cones 404a, 404b from separate energy beam sources, while FIG. 4B illustrates a portion of a layout 450 in which hexagonal areas 452 of a powder layer are concurrently fused by scanning of electron beams within electron beam cones 454a, 454b from separate energy beam sources. Each square area 402 and hexagonal area 452 may individually correspond to areas 308a, 308b, 308c of FIG. 3. While FIGs. 4A and 4B illustrate specific examples of polygonal areas ( e.g . squares and hexagons), other polygonal shape layouts may be used for printing.

[0031] The array of deflectors may be controlled to steer energy beams within the electron beam cones to fuse areas into polygonal shapes, with each polygonal shape being fully contained within a cross-section of each energy beam cone. For example, as illustrated in FIGs. 4A and 4B, electron beams scanning in electron beam cones 404a, b and 454a, b may concurrently fuse square areas 402 or hexagonal areas 452 respectively into their corresponding shape. The controller may control the electron beams such that their respective cone cross-sections 406a, 406b and 456a, 456b fully contain each inscribed or printed polygonal shape. For instance, the deflectors may steer the electron beams such that only the vertices of each square area 402 or hexagonal area 452 intersect with the perimeter of the respective cross-sections, as illustrated in FIGs. 4A and 4B. In this way, the work envelope and build envelope may be maximized (e.g. since all polygonal areas may be fully encompassed by electron beams), while interference may be minimized (e.g. due to limited overlap 408, 458 between the electron beam cones).

[0032] As a result, the present disclosure improves productivity of the additive manufacturing process with increased build envelope or work envelope capability. As the plurality of energy beam sources may be individually and concurrently controlled to fuse separate areas of a powder bed to build separate parts on a single build piece, the printing time may be reduced. Similarly, as the plurality of energy beam sources may be individually and concurrently controlled to fuse a common area of the powder bed to build a single part (rather than separate parts which must be joined), the joining process may be omitted and the cycle time may be further reduced. Additionally, as the plurality of energy beam sources are scalable, the work envelope may effectively be increased (based on the combined movement of all of the energy beams) and the build envelope may accommodate printing of larger parts.

[0033] The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these exemplary embodiments presented throughout this disclosure will be readily apparent to those skilled in the art. Thus, the claims are not intended to be limited to the exemplary embodiments presented throughout the disclosure, but are to be accorded the full scope consistent with the language claims. All structural and functional equivalents to the elements of the exemplary embodiments described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed under the provisions of 35 U.S.C. §112(f), or analogous law in applicable jurisdictions, unless the element is expressly recited using the phrase “means for” or, in the case of a method claim, the element is recited using the phrase “step for.”

Claims

WHAT IS CLAIMED IS:

1. An apparatus for powder-bed fusion, comprising: a structure that supports a layer of feedstock; and a plurality of electron beam sources that each generate an energy beam to fuse one or more areas of the layer of feedstock.

2. The apparatus of claim 1, wherein the plurality of electron beam sources comprises one or arrays.

3. The apparatus of claim 1, wherein the plurality of electron beam sources is scalable to accommodate structures of different sizes.

4. The apparatus of claim 1, wherein the plurality of electron beam sources is two- dimensionally (2D) arranged at a common distance across from the structure.

5. The apparatus of claim 1, wherein the plurality of electron beam sources is distributed across the structure to concurrently fuse multiple areas of the layer of feedstock.

6. The apparatus of claim 1, further comprising a plurality of deflectors that steer the respective electron beams.

7. The apparatus of claim 6, wherein a subset of the plurality of deflectors is configured to steer the electron beams from a subset of the plurality of electron beam sources to fuse one or more common areas of the layer of feedstock.

8. The apparatus of claim 6, wherein the plurality of deflectors is configured to steer the electron beams to fuse multiple areas of layers of feedstock for forming separate parts or a single part.

9. The apparatus of claim 6, wherein the electron beams are configured to overlap at the one or more fused areas to prevent gaps.

10. The apparatus of claim 6, wherein the plurality of deflectors comprises magnetic fields, and the plurality of deflectors are configured to limit interaction of the magnetic fields.

11. The apparatus of claim 6, wherein the plurality of deflectors is configured to steer the electron beams within one or more electron beam cones to fuse the one or more areas into polygonal shapes, each polygonal shape being fully contained within a cross- section of each electron beam cone.

12. An apparatus for powder-bed fusion, comprising: a structure that supports a layer of feedstock; a plurality of electron beam sources that each generate an electron beam; and a plurality of deflectors that individually steer the electron beams to concurrently fuse multiple areas of the layer of feedstock.

13. The apparatus of claim 12, wherein the plurality of electron beam sources comprises one or more arrays.

14. The apparatus of claim 12, wherein the plurality of electron beam sources is scalable to accommodate structures of different sizes.

15. The apparatus of claim 12, wherein the plurality of electron beam sources is two-dimensionally (2D) arranged at a common distance across from the structure.

16. The apparatus of claim 12, wherein a subset of the plurality of deflectors is configured to steer the electron beams from a subset of the plurality of electron beam sources to fuse one or more common areas of the layer of feedstock.

17. The apparatus of claim 12, wherein the plurality of deflectors is configured to steer the electron beams to fuse multiple areas of layers of feedstock for forming separate parts or a single part.

18. The apparatus of claim 12, wherein the electron beams are configured to overlap at the multiple fused areas to prevent gaps.

19. The apparatus of claim 12, wherein the plurality of deflectors comprises magnetic fields, and the plurality of deflectors are configured to limit interaction of the magnetic fields.

20. The apparatus of claim 12, wherein the plurality of deflectors is configured to steer the electron beams within electron beam cones to fuse the multiple areas into polygonal shapes, each polygonal shape being fully contained within a cross-section of each electron beam cone.

21. An apparatus for powder-bed fusion, comprising: a structure that supports a layer of feedstock; an array of electron beam sources that each generate an electron beam; and an array of deflectors that steer the electron beams to fuse one or more areas of the layer of feedstock; wherein the array of electron beam sources is scalable to accommodate structures of different sizes.