Patent Description:
Recently, additive manufacturing methods for making metal alloy components have emerged as alternatives to casting and machining methods. Additive manufacturing is also referred to as "layered manufacturing," "reverse machining," and "<NUM>-D printing. " On a basic level, additive manufacturing technologies are based on the concept of building up material in a cross-sectional layer-by-layer to form a 3D component. Common to additive manufacturing technologies is the use of a 3D modeling software (Computer Aided Design or CAD), machine equipment, and layering material. Once a CAD sketch is produced, the machine equipment reads in data from the CAD file and adds successive layers of a desired material to fabricate the 3D component.

Some specific additive manufacturing processes employ a powder bed fusion technique to fuse metal alloy powder in additive steps to produce a component. For example, some additive manufacturing processes utilize a beam of energy that is scanned across a powder bed to fuse a layer of metal alloy powder in the powder bed in additive steps. Some examples of such powder bed additive manufacturing processes include direct metal laser sintering/fusion (DMLS)/(DMLF), selective laser sintering/fusion (SLS)/(SLF), and electron beam melting (EBM). In these processes, a layer of metal alloy powder in the powder bed is fused to an underlying partially-formed component (or a seed component) to add a new layer to the component. A new layer of metal alloy powder is deposited into the powder bed and over the previously formed layer of the partially-formed component, and the new layer of metal alloy powder is similarly fused to the component. The depositing-and-fusing procedure is repeated a number of times to produce a plurality of layers on the partially formed component to, ultimately, form the metal alloy component.

From the document <CIT> an apparatus for additively manufacturing three-dimensional objects is known, wherein a model of said three dimensional article is provided and a first energy beam is directed over a work table causing said first powder layer to fuse in first selected locations according to said model to form a first cross section of said three-dimensional article, wherein a second energy beam is directed over said work table causing said first powder layer to fuse in second selected locations according to said model to form the first cross section of said three-dimensional article, wherein said first and second locations of said first powder layer are at least partially overlapping each other. The document <CIT> discloses an additive manufacturing system with several electron beams. The document <CIT> teaches a method for forming a three-dimensional article through successively depositing individual layers of powder material that are fused together so as to form the article, the method comprising the step of heating a first portion of a support surface while depositing a layer of powder material on a second portion of the support surface.

Shortcomings of the prior art are overcome and additional advantages are provided through the provision, in one embodiment, of a system for adaptively forming three-dimensional components from a plurality of deposited layers of metallic powder. The system includes a build chamber, a plurality electron beam sources, and a controller. The build chamber includes a housing, a build platform disposed in the build chamber, and an actuator for moving the build platform in the build chamber. The plurality of electron beam sources are operable for directing a plurality of electron beams into the build chamber and onto the plurality of deposited layers of metallic powder disposed on the build platform. The controller is operable for simultaneously controlling the actuator and the plurality of electron beam sources to direct the plurality of electron beams onto the plurality of deposited layers of metallic powder on the build platform to sequentially consolidate patterned portions of the plurality of deposited metallic powder layers to adaptively form the three-dimensional components. The controller is operable to divide the plurality of layers of metallic powder into a plurality of regions; direct each of the plurality of electron beams onto a different region of the plurality of deposited layers of metallic powder; focus each of the plurality of electron beams onto a portion of each of the different regions; and randomly move the focused electron beams within the different regions.

In another embodiment, a method for adaptively forming a three-dimensional component includes providing a plurality of electron beam sources, and simultaneously controlling the plurality of electron beam sources to direct a plurality of electron beams onto a plurality of deposited layers of metallic powder to sequentially consolidate patterned portions of the plurality of deposited metallic powder layers to adaptively form the three-dimensional component. The controlling comprises: dividing the plurality of layers of metallic powder into a plurality of regions; directing each of the plurality of electron beams onto a different region of the plurality of deposited layers of metallic powder; focusing each of the plurality of electron beams onto a portion of each of the different regions; and randomly moving the focused electron beams within the different regions.

The foregoing and other objects, features, and advantages of the present disclosure are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:.

Embodiments of the present disclosure and certain features, advantages, and details thereof, are explained more fully below with reference to the non-limiting examples illustrated in the accompanying drawings. Descriptions of well-known materials, processing techniques, etc., are omitted so as not to unnecessarily obscure the disclosure in detail.

<FIG> diagrammatically illustrates a system <NUM> in accordance with an embodiment of the present invention as defined by claim <NUM> for adaptively forming three-dimensional components from a plurality of deposited layers of metallic powder. System <NUM> includes a build chamber <NUM>, a plurality of electron beam sources 200A through 200N, and a controller <NUM>. Build chamber <NUM> includes a housing <NUM> defining a vacuum chamber, a build platform <NUM> disposed in the build chamber, an actuator <NUM> for moving the build platform in the build chamber, one or more powder hoppers <NUM>, and a powder distributor <NUM>. Plurality of electron beam sources <NUM> includes a plurality of electron beam guns or sources (one of which being shown in <FIG>) for directing a plurality of electron beams 210A through 210N into the build chamber and onto a plurality of deposited layers of metallic powder disposed on the build platform. While <FIG> illustrates a linear row of a plurality of electron beams, it is appreciated that electron beam source <NUM> may include a plurality of adjacent linear rows of plurality of electron beams operable to define a two-dimensional array of emitted election beams. Controller <NUM> is operable for simultaneously controlling actuator <NUM> and the plurality of electron beam sources to direct the plurality of electron beams onto a plurality of deposited layers of metallic powder on the build platform to sequentially consolidate patterned portions of the plurality of deposited metallic powder layers to adaptively form three-dimensional component <NUM>.

As will be appreciated from the present description below, the technique of the present disclosure may improve build speed and decrease planar damage thereby enabling the application of additive manufacturing to additional materials and geometries. For example, a linear or two-dimensional array of electron beam guns or sources may serve a portion of the powder bed, leveraging electrostatic focusing, current modulation, and deflection to heat a patterned layer of the powder bed for solidification. Additive manufacturing systems, in one or more embodiments, may include about <NUM> by about <NUM> electron beam sources with each electron beam source serving a region of about <NUM> millimeters (about <NUM> inch) by about <NUM> millimeters (about <NUM> inch) of the powder bed leveraging electrostatic focusing, current modulation, and deflection to heat a sub-millimeter patterned region or layer of the powder bed for solidification. Additionally, the technique of the present disclosure may improve or reduce the processing time of a single layer and in the part build times for forming three-dimensional components, and may be limited due to the powder spreading time required. As will be appreciated, the present technique may overcome the problems associated with a single electron beam additive system that cannot maintain mechanical integrity across a large area.

With reference still to <FIG>, powder hoppers <NUM> may hold powder material which is provided on a start plate <NUM>. The powder material may be pure metals or metal alloys such as titanium, titanium alloys, aluminum, aluminum alloys, stainless steel, Co--Cr--W alloy, etc. A first powder layer may be provided by distributing powder evenly over the start plate or a solidified patterned layer. For example, material deposited from hoppers <NUM> may be distributed by powder distributor <NUM> such as a rake system. The rake may be moved to distribute the powder over the start plate or a solidified patterned layer. The distance between a lower part of the rake and the upper part of the start plate or solidified patterned layer may determine a thickness of distributed powder layer. The powder layer thickness may be easily be adjusted by adjusting the height of the build platform via the actuator.

At least a portion of the plurality of electron beam guns or sources may be provided in or in fluid communication with a vacuum in the build chamber <NUM>. Build chamber <NUM> may be operable for maintaining a vacuum environment by means of a vacuum system <NUM>, which vacuum system may comprise a turbo-molecular pump, a scroll pump, an ion pump, and one or more valves which are well known to a skilled person in the art. Vacuum system <NUM> may be controlled by controller <NUM>.

Three-dimensional component <NUM> is formed through successive fusion of parts of a powder bed, which component corresponds to successive cross-sections of the three-dimensional component, and include a step of providing a model of the three dimensional component. The model may be generated via a CAD (Computer Aided Design) tool.

<FIG> illustrates one embodiment of electron beam gun or source <NUM> for producing electron beam <NUM>. For example, the electron beam gun or source may generally include a cathode <NUM>, a grid <NUM>, and an anode <NUM>, which is used to generate and accelerate a primary electron beam. A magnetic focusing coil <NUM> and deflection coil <NUM> may be used for controlling the way in which the electron beam impinges on the powder layer <NUM> being processed. In operation, cathode may be a source of thermally-emitted electrons that are both accelerated and shaped into a collimated beam by the electrostatic field geometry established by grid <NUM> and anode <NUM>. The electron beam then emerges through an exit hole in anode <NUM> with, for example, an energy equal to the value of the negative high voltage being applied to the cathode. After exiting the anode, the beam passes through electromagnetic focusing coil <NUM> and deflection coil <NUM>. The focusing coil is used for producing either a focused or defocused beam spot on patterned layer <NUM>, while the deflection coil is used to either position the beam spot on a stationary location or move the spot over a region of the patterned layer <NUM>. It will be appreciated that other types of electron beam guns or sources and/or additional components may be suitably employed.

With reference again to <FIG>, the plurality of electron beam guns or sources 200A through 200N generates a plurality of electron beams 210A through 210N which is used for melting or fusing together powder material or patterned layer <NUM> (<FIG>). During a work cycle or additive build, build platform <NUM> is lowered successively in relation to the plurality of electron beam sources <NUM> after each added layer of powder material. For example, build platform <NUM> may be movable in a vertical direction, i.e., in the direction of double-headed arrow P. Build platform <NUM> may be disposed in an initial position, in which a first powder material layer of desired thickness has been laid down on start plate <NUM>. The build platform is thereafter lowered in connection with laying down a new powder material layer for the formation of a new cross-section of a three-dimensional component. The actuator or means for lowering the build platform <NUM> may include a servo motor equipped with a gear, adjusting screws, etc..

Controller <NUM> is used for controlling, among other things, the plurality of electron beam sources, the actuator, powder distributor <NUM>, and vacuum pressure in the build chamber. For example, controller <NUM> is operable for controlling and managing the positon or location of the plurality of electron beams impinging on a patterned layer during the time for heating the power layer. Control unit <NUM> includes instructions for controlling each electron beam for each layer of the three-dimensional component to be formed.

<FIG> illustrates a top plan view of a portion of powder layer <NUM> for use in forming a three-dimensional component employing additive manufacturing system <NUM> <FIG>). The portion of powder layer <NUM> is illustrated in broken lines as being divided into a plurality of regions or areas 144A through 144N. Each of the electron beam guns or sources 200A through 200N (<FIG>) corresponding to a different one of plurality of regions or areas 144A through 144N. In addition, illustrated in each of the regions is an electron beam thermal spot 230A through 230N covering a portion of respective regions 144A through 144N generated by electron beams 210A through 210N at a point in time, t1. At t2 to tN, the electron beam thermal spots may be moved to another locations in the sub-region.

For example, in one or more embodiment, adaptive manufacturing system <NUM> (<FIG>) may include a two-dimensional array of electron beam sources which are operable to process a two-dimensional powdered layer having a width of about <NUM> millimeters (about <NUM> inches) and a length of about <NUM> millimeters (about <NUM> inches). Each electron beam gun or source may be operable to cover a different two-dimensional region having a width of about <NUM> millimeters (about <NUM> inch) and a length of about <NUM> millimeters (<NUM> inch). Each electron beam gun or source may provide a two-dimensional electron beam thermal spot of having a width of about <NUM> millimeter and a length of about <NUM> millimeter. Each two-dimensional region (e.g., about <NUM> millimeters by about <NUM> millimeters region) may include about <NUM>,<NUM> sub-regions (e.g., different about <NUM> millimeter by about <NUM> millimeter sub-regions).

It this illustrated embodiment, each patterned power layer may be heated by the plurality of electron beams for about <NUM> milliseconds (corresponding, for example, to t0 to tN) to operably melt the powdered layer. For example, in this embodiment, each of the <NUM>,<NUM> sub-regions will be exposed to the electron beam having an electro beam power of about <NUM> kW (about <NUM> J/mm3) for a period of about <NUM> nanoseconds, e.g., <NUM> nanoseconds dwell time per sub-region. It will be appreciated that if fewer electron beam guns or sources is provided, power may need to be increased while dwell time may need to be decreased. The targeting deposited energy may be about <NUM> J/mm3 at a depth is about <NUM> microns. In addition, the plurality of electron beams may be pulsed electron beams operably provided by switching on and off the generation of the electrons in the electron beam gun or source such as via control by the controller. The frequency of the switching may correspond to and be timed to the different thermal heating spots to be applied to the sub-regions.

With reference again to <FIG>, a fist powder layer is disposed on the start build <NUM> (<FIG>). The plurality of electron beams may be directed over start plate <NUM> (<FIG>) causing a first powder layer to fuse in selected locations to form a first cross-section of the three-dimensional component. Control unit <NUM> is operable for directing the location or position the plurality of electron beams engaging the first powder layer. After a first layer is formed, a second powder layer is provided on top of the first solidified layer. After distribution of the second powder layer, the plurality of electron beams is directed onto the second powder layer causing the second powder layer to fuse in selected locations to form a second cross-section of the three-dimensional component. Fused portions in the second layer may be bonded to fused portions of the first layer. The fused portions in the first and second layer may be melted together by melting not only the powder in the uppermost layers but also remelting at least a fraction of a thickness of a layer directly below the uppermost layer.

The application of the plurality of electron beams results in the electron beams forming a thermal heat spot directed on and which is moved over the corresponding sub-region of the powder layer. The movement of the thermal heat spots are controlled by the controller to be randomly moved over the sub-regions.

In one or more embodiments of the present disclosure, the electron beam guns or sources may generate a plurality of focusable electron beams with an accelerating voltage of about <NUM> kV and with a beam power in the range of about <NUM> kW to about <NUM> kW, about <NUM> kW to about <NUM> kW, about <NUM> kW to about <NUM> kW, or about <NUM> kW.

In one or more embodiments, the three-dimensional component may be a turbine component such as a turbine airfoil or blade. In one or more embodiments, the three-dimensional component may be a turbine component repair. For repair of a turbine blade, an array of electron beam sources may include a linear array of <NUM> by <NUM> electron beam guns or sources.

<FIG> illustrates a flowchart of a method <NUM> for adaptively forming a three-dimensional component including steps in accordance with the present invention. The method in accordance with the invention is fully defined in the appended claim <NUM>. Method <NUM> includes at <NUM>, providing a plurality of electron beam sources, and at <NUM>, simultaneously controlling the plurality of electron beam sources to direct a plurality of electron beams onto a plurality of deposited layers of metallic powder to sequentially consolidate patterned portions of the plurality of deposited metallic powder layers to adaptively form the three-dimensional component.

<FIG> is a block diagram of controller <NUM> in accordance with one embodiment of the present disclosure. Controller <NUM> is suitable for storing and/or executing program code, such as program code for performing the processes described above, and includes at least one processor <NUM> coupled directly or indirectly to memory <NUM> through, a bus <NUM>. In operation, processor(s) <NUM> obtains from memory <NUM> one or more instructions for execution by the processors. Memory <NUM> may include local memory employed during actual execution of the program code, bulk storage, and cache memories which provide temporary storage of at least some program code in order to reduce the number of times code must be retrieved from bulk storage during program code execution. A non-limiting list of examples of memory <NUM> includes a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. Memory <NUM> includes an operating system <NUM> and one or more computer programs <NUM>, performing the processes described above in connection with the additive manufacturing system.

Input/Output (I/O) devices <NUM> and <NUM> (include but not limited to keyboards, displays, pointing devices, etc.) may be coupled to the system either directly or through I/O controllers <NUM>.

Network adapters <NUM> may also be coupled to the system to enable the data processing system to become coupled to other data processing systems through intervening private or public networks. Modems, cable modem and Ethernet cards are just a few of the currently available types of network adapters <NUM>. In one example, network adapters <NUM> and/or input devices <NUM> facilitate obtaining images of a build process in which a three-dimensional component is formed.

Controller <NUM> may be coupled to storage <NUM> (e.g., a non-volatile storage area, such as magnetic disk drives, optical disk drives, a tape drive, etc.), having one or more databases. Storage <NUM> may include an internal storage device or an attached or network accessible storage. Computer programs in storage <NUM> may be loaded into memory <NUM> and executed by a processor <NUM> in a manner known in the art.

Controller <NUM> may include fewer components than illustrated, additional components not illustrated herein, or some combination of the components illustrated and additional components. Controller <NUM> may include any computing device known in the art, such as a mainframe, server, personal computer, workstation, laptop, handheld computer, telephony device, network appliance, virtualization device, storage controller, etc. In addition, processes described above may be performed by multiple controllers <NUM>, working as part of a clustered computing environment.

In some embodiments, aspects of the present invention may take the form of a computer program product embodied in one or more computer readable medium(s). The one or more computer readable medium(s) may have embodied thereon computer readable program code. Various computer readable medium(s) or combinations thereof may be utilized. For instance, the computer readable medium(s) may comprise a computer readable storage medium, examples of which include (but are not limited to) one or more electronic, magnetic, optical, or semiconductor systems, apparatuses, or devices, or any suitable combination of the foregoing. Example computer readable storage medium(s) include, for instance: an electrical connection having one or more wires, a portable computer diskette, a hard disk or mass-storage device, a random access memory (RAM), read-only memory (ROM), and/or erasable-programmable read-only memory such as EPROM or Flash memory, an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device (including a tape device), or any suitable combination of the above. A computer readable storage medium is defined to comprise a tangible medium that can contain or store program code for use by or in connection with an instruction execution system, apparatus, or device, such as a processor. The program code stored in/on the computer readable medium therefore produces an article of manufacture (such as a "computer program product") including program code. The scope of the various embodiments should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. In the appended claims, the terms "including" and "in which" are used as the plain-English equivalents of the respective terms "comprising" and "wherein. " Moreover, in the following claims, the terms "first," "second," and "third," etc. are used merely as labels, and are not intended to impose numerical requirements on their objects. Also, the term "operably" in conjunction with terms such as coupled, connected, joined, sealed or the like is used herein to refer to both connections resulting from separate, distinct components being directly or indirectly coupled and components being integrally formed (i.e., one-piece, integral or monolithic).

Claim 1:
A system (<NUM>) for adaptively forming three-dimensional components from a plurality of deposited layers of metallic powder, said system (<NUM>) comprising;
a build chamber (<NUM>) comprising:
a housing (<NUM>);
a build platform (<NUM>) disposed in said build chamber (<NUM>); and
an actuator (<NUM>) for moving said build platform in said build chamber;
a plurality of electron beam sources (<NUM>) for directing a plurality of electron beams into said build chamber (<NUM>) and onto the plurality of deposited layers of metallic powder disposed on said build platform (<NUM>); and
a controller (<NUM>) for simultaneously controlling said actuator (<NUM>) and said plurality of electron beam sources to direct the plurality of electron beams onto the plurality of deposited layers of metallic powder on said build platform (<NUM>) to sequentially consolidate patterned portions of the plurality of deposited layers of metallic powder to adaptively form the three-dimensional components;
wherein said controller (<NUM>) is operable to:
divide the plurality of layers (<NUM>) of metallic powder into a plurality of regions (144A-144N);
direct each of the plurality of electron beams onto a different region (144A-144N) of the plurality of deposited layers (<NUM>) of metallic powder;
focus each of the plurality of electron beams onto a portion of each of the different regions (144A-144N); and
randomly move the focused electron beams within the different regions (144A-144N).