Patent Description:
Additive manufacturing (AM) processes generally involve the buildup of one or more materials to make a net or near-net shape object, in contrast to subtractive manufacturing methods, which selectively remove material from an initial form to fabricate an object. Though "additive manufacturing" is an industry standard term (ASTM F2792), it encompasses various manufacturing and prototyping techniques known under a variety of names, including freeform fabrication, 3D printing, and rapid prototyping/tooling. A particular type of AM process uses a focused energy source (e.g., an electron beam, a laser beam) to sinter or melt a powder material deposited on a build platform within a chamber, creating a solid three-dimensional object in which particles of the powder material are bonded together.

Laser sintering/melting, as used in Direct Laser Sintering (DLS) and/or Direct Laser Melting (DLM), is a common industry term used to refer to a method of producing three-dimensional (3D) objects by using a laser beam to sinter or melt a fine powder. In particular, laser sintering/melting techniques often entail projecting a laser beam onto a controlled amount of powder (e.g., a powder bed) on a substrate, so as to form a layer of fused particles or molten material thereon. When the laser beam interacts with the powder at a powder bed, smoke and/or a particulate matter (e.g., condensate, spatter) is produced within the chamber. The smoke and/or the particular matter may be detrimental to the quality of the resulting object. As an example, the suspended smoke and/or particular matter within the chamber can interfere with the laser beam and reduce the energy or intensity of the laser beam before it reaches the powder bed. As another example, the smoke and/or the particular matter may deposit onto the powder bed and may become incorporated into the resulting object.

In certain laser sintering/melting (or DLS/DLM) systems, a gas flow is introduced in an upper portion of the chamber (e.g., toward the top of the chamber in the z-direction and away from the build platform) to flow generally parallel to the build platform in an effort to remove the smoke and/or particulate matter and prevent deposition. However, this upper gas flow may not efficiently remove the smoke and/or particulate matter in the lower portion of the chamber (e.g., toward the build platform and away from the top of the chamber in the z-direction). Accordingly, particulate matter may become trapped or deposited within the lower portion of the chamber, which can lower the quality of the resulting object of the DLS/DLM processes.

<CIT> discloses a process chamber for an additive manufacturing apparatus.

<CIT>, which is a prior art document under Art. <NUM> (<NUM>) EPC, discloses a process chamber for an additive manufacturing apparatus.

The invention is defined by the subject-matter of the appended claims. In one embodiment, an additive manufacturing system includes a housing defining a chamber, a build platform disposed in a lower portion of the chamber at a first elevation with respect to the chamber, and a lower gas inlet disposed proximate an upstream end portion of the chamber, where the lower gas inlet is disposed at a second elevation with respect to the chamber and is configured to supply a lower gas flow. The additive manufacturing system also includes a contoured surface extending between the lower gas inlet and the build platform. The contoured surface is configured to direct the lower gas flow from the second elevation at the lower gas inlet to the first elevation at the build platform and discharge the lower gas flow in a direction substantially parallel to the build platform. The additive manufacturing system also includes one or more gas delivery devices coupled to the lower gas inlet configured to regulate one or more flow characteristics of the lower gas flow, and a gas outlet disposed in a downstream end portion of the chamber, where the gas outlet is configured to discharge the lower gas flow from the chamber.

In another embodiment, a method of operating an additive manufacturing system includes depositing a bed of a powder material on a build platform positioned at a first elevation within a chamber, supplying a lower gas flow into a lower portion of the chamber at a second elevation, and directing the lower gas flow along a contoured surface via a fluid guiding effect from the second elevation to the first elevation, and then toward the build platform along a direction parallel to the build platform. The method also includes applying a focused energy beam to at least a portion of the bed of the powder material deposited on the build platform to form a solidified layer.

In the following specification and the claims, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. As used herein, the term "or" is not meant to be exclusive and refers to at least one of the referenced components being present and includes instances in which a combination of the referenced components may be present, unless the context clearly dictates otherwise. The term "uniform gas flow", as used herein, means that the flow velocity of a gas flow does not significantly vary across a width and/or a length of a path of the gas flow. As used herein, the term "additive manufacturing", or "AM", relates to any suitable laser sintering/melting additive manufacturing technique, including, but not limited to: Direct Metal Laser Melting, Direct Metal Laser Sintering, Direct Metal Laser Deposition, Laser Engineered Net Shaping, Selective Laser Sintering, Selective Laser Melting, Selective Heat Sintering, Fused Deposition Modeling, Hybrid Systems, or combinations thereof.

The present disclosure generally encompasses systems and methods for fabricating objects using a laser sintering/melting-based method of additive manufacturing. As noted above, for such additive manufacturing techniques, when the laser beam sinters or melts the powder bed within an enclosed manufacturing chamber, smoke and/or particulate matter (e.g., condensate, spatter) can accumulate within the chamber. As mentioned, this smoke and/or the particulate matter may interact with the laser beam and/or the object being printed and interfere with the fabrication process. As such, it may be desirable to remove the smoke and/or the particulate matter from the chamber to improve the manufacturing process and/or the quality of the resulting object.

As discussed in detail below, embodiments of the present disclosure include additive manufacturing (AM) systems and methods that employ a combination of an upper gas flow in an upper portion of the chamber and a lower gas flow in a lower portion of the chamber, where the lower gas flow is generally directed parallel to a build platform of the chamber. The lower gas flow is supplied to the chamber via a lower gas inlet disposed above or beneath (e.g., with respect to the z-direction) the build platform. A contoured surface extends tangentially between the lower gas inlet and the build platform, or a surface adjacent the build platform. Accordingly, the contoured surface extends from an elevation of the lower gas inlet (e.g., an elevation above or below the build platform) to an elevation of the build platform. For clarity, the term "elevation", as used herein, refers to a distance at which a component of interest (e.g., the lower gas inlet, the build platform) is disposed vertically above a lower end portion of the AM system. The contoured surface is configured to receive the lower gas flow from the lower gas inlet and direct the lower gas flow to the elevation of the build platform. As described in greater detail herein, the contoured surface is configured to induce a fluid guiding effect that directs the lower gas flow from the elevation of the lower gas inlet to the elevation of the build platform. As used herein, the term "fluid guiding effect" includes the Coanda effect (e.g., the tendency of a flow of fluid to adhere to an adjacent flat or curved surface) or any other fluid dynamic effect that may influence a flow trajectory of a fluid along a surface. The fluid guiding effect enables the contoured surface to discharge (e.g., steer, point, direct) the lower gas flow in a direction parallel to the build platform.

The addition of the lower gas flow may advantageously overcome the above noted shortcomings of an AM system having only the upper gas flow by more efficiently removing the smoke and/or particulate matter from the chamber, as well as suppressing recirculation of the smoke and/or the particulate matter inside the chamber of the AM system. As such, the stagnation and/or deposition of the smoke and/or particulate matter on various locations inside the chamber may be substantially reduced or eliminated, enabling improved quality of the resulting object of the AM process. In some embodiments, certain flow characteristics of the lower gas flow may be controlled or tuned to desirable levels that are favorable to generate, for example, the Coanda effect, and facilitate removing the smoke and/or particular matter from within the chamber. The flow characteristics may include, but are not limited to, flow rate (e.g., mass flow rate, volume flow rate), flow velocity (e.g., in meters per second (m/s)), flow direction or angle, flow temperature, or any combination thereof. These and other features will be described below with reference to the drawings.

<FIG> illustrates an example embodiment of an AM system <NUM> (e.g., a laser sintering/melting AM system <NUM>) for producing an article or object using a focused energy source (e.g., a laser) or beam. To facilitate discussion, the AM system <NUM> and its components will be described with reference to an x-axis or direction <NUM>, a y-axis or direction <NUM>, and a z-axis or direction <NUM>. In the illustrated embodiment, the AM system <NUM> includes a controller <NUM> having memory circuitry <NUM> that stores instructions (e.g., software, applications), as well as processing circuitry <NUM> configured to execute these instructions to control various components of the AM system <NUM>. The AM system <NUM> includes a housing <NUM> defining a manufacturing chamber <NUM> (also referred to herein as chamber <NUM>) that defines an interior volume <NUM>. The chamber <NUM> is sealed to contain an inert atmosphere and to protect the build process from an ambient atmosphere <NUM> outside of the chamber <NUM>. The AM system <NUM> includes a build platform <NUM> disposed inside the chamber <NUM> on a bottom surface or bottom wall <NUM> of the housing <NUM>. Accordingly, the illustrated build platform <NUM> is oriented substantially parallel to the bottom wall <NUM> of the housing <NUM>. For example, an angle between the build platform <NUM> and the bottom wall <NUM> may be less than <NUM> degrees (°), less than <NUM>°, or less than <NUM>°. In some embodiments, the build platform <NUM> may have a working area (e.g., the top surface of the build platform <NUM>) in a range between about <NUM> square meters (m<NUM>) and about <NUM><NUM>. The article or object of the AM process is fabricated on the build platform <NUM>, as discussed below.

The AM system <NUM> includes a powder application device <NUM>, which may be arranged inside the chamber <NUM> to repeatedly deposit a quantity (e.g., a layer or bed) of a powder material onto the build platform <NUM>. The powder material deposited on the build platform <NUM> generally forms a powder bed <NUM>. The powder material may include, but is not limited to, polymers, plastics, metals, ceramics, sand, glass, waxes, fibers, biological matter, composites, or hybrids of these materials. These materials may be used in a variety of forms as appropriate for a given material and method, including, for example, solids, powders, sheets, foils, tapes, filaments, pellets, wires, atomized, and combinations of these forms.

The AM system <NUM> includes an energy generating system <NUM>, which may be arranged inside or outside the chamber <NUM> for generating and selectively directing a focused energy beam <NUM>, such as laser, onto at least a portion of the powder bed <NUM> disposed on the build platform <NUM>. For the embodiment illustrated in <FIG>, the energy generating system <NUM> is arranged outside the chamber <NUM> in proximity to a top surface or a top wall <NUM> of the housing <NUM>, opposite to the bottom surface or the bottom wall <NUM>. The focused energy beam <NUM> enters the chamber <NUM> through a window <NUM> disposed within the top wall <NUM>. The powder bed <NUM> disposed on the build platform <NUM> is subjected to the focused energy beam <NUM> in a selective manner as controlled by the controller <NUM>, depending on the desired geometry of the article. In some embodiments, the energy generating system <NUM> includes a focused energy source for generating the focused energy beam <NUM>. In some embodiments, the focused energy source includes a laser source and the focused energy beam <NUM> is a laser beam. In some embodiments, the laser source includes a pulsed laser source that generates a pulsed laser beam. The pulsed laser beam is not emitted continuously, in contrast with a continuous laser radiation, but is emitted in a pulsed manner (e.g., in time limited pulses with interval). In some embodiments, the energy generating system <NUM> includes a plurality of focused energy sources that is configured to selectively irradiate the powder bed <NUM> using the focused energy beam <NUM>.

The AM system <NUM> includes a positioning system <NUM> (e.g., a gantry or other suitable positioning system), which may be arranged inside the chamber <NUM>. The positioning system <NUM> may be any multidimensional positioning system, such as a delta robot, cable robot, robot arm, or another suitable positioning system. The positioning system <NUM> may be operatively coupled to the powder application device <NUM>, the energy generating system <NUM>, the build platform <NUM>, or a combination thereof. The positioning system <NUM> may move the powder application device <NUM>, the energy generating system <NUM>, the build platform <NUM>, or a combination thereof, relatively to one another, in any of the x-, y-, and z- directions <NUM>, <NUM>, <NUM>, or a combination thereof.

The AM system <NUM> is further configured to supply an upper gas flow and a lower gas flow into the chamber <NUM>, as well as discharge a gas flow from the chamber <NUM>, as will be discussed in <FIG>. The gas flow being discharged or exhausted from the chamber <NUM> includes the upper gas flow, the lower gas flow, as well as a substantial portion of any smoke and/or particulate matter that is generated on application of the focused energy beam <NUM> to selectively melt or sinter the powder bed <NUM> during formation of the desired article. By employing a combination of the upper and lower gas flows as set forth herein, recirculation of the smoke and/or particulate matter within the chamber may be substantially reduced or eliminated, thus substantially improving the quality of the build process and/or the article being printed.

<FIG> is a schematic perspective view illustrating an embodiment of the chamber <NUM> of the AM system <NUM>, in accordance with the present approach. As illustrated, the AM system <NUM> includes a plenum <NUM> that is defined by a plenum side wall <NUM> and a plenum dividing wall <NUM>, which each extend in the y-direction <NUM> from a side wall <NUM> to a side wall <NUM> of the housing <NUM>, along an entire width <NUM> of the chamber <NUM>. Accordingly, the plenum dividing wall <NUM> and the plenum side wall <NUM> enclose a portion of the interior volume <NUM> of the chamber <NUM> between a rear wall <NUM> and the top wall <NUM> of the chamber <NUM>. The enclosed volume is separate from the remaining volume of the chamber <NUM>, and will be referred to herein as a plenum chamber <NUM>. In the illustrated embodiment, the plenum chamber <NUM> is disposed within an upper portion <NUM> of the chamber <NUM>, which includes any portion, or portions of the chamber <NUM> disposed vertically above (e.g., with respect to the z-direction <NUM>) the plenum dividing wall <NUM>. For example, in some embodiments, a height <NUM> of the plenum <NUM> (e.g., a distance between the top wall <NUM> and the plenum dividing wall <NUM>) may include <NUM>%, <NUM>%, <NUM>%, or <NUM>%, of a total height <NUM> of the chamber <NUM>. Accordingly, the upper portion <NUM> of the chamber <NUM> may include an upper <NUM>%, upper <NUM>%, upper <NUM>%, or an upper <NUM>% of the chamber <NUM>, depending on the vertical position of the plenum dividing wall <NUM> in different embodiments.

In the illustrated embodiment, the plenum chamber <NUM> is fluidly coupled to an upper gas delivery device <NUM> via an aperture <NUM> defined within the rear wall <NUM> of the housing <NUM>. As shown in the illustrated embodiment, the aperture <NUM> is defined within a portion of the rear wall <NUM> that is vertically above the plenum dividing wall <NUM>. The upper gas delivery device <NUM> may be coupled to a gas supply line or any other suitable gas source, which enables the upper gas delivery device <NUM> to supply a gas flow to the plenum chamber <NUM> and, in some cases, pressurize the plenum chamber <NUM> (e.g., with respect to an ambient pressure within the chamber <NUM>). As described in greater detail herein, the upper gas delivery device <NUM> may include an upper flow generating device <NUM> that includes one or more suitable conveying devices such as one or more fluid valves, one or more pumps or blowers, or a combination thereof, which generate and/or regulate a flow rate and/or a pressure of the gas flow entering the plenum chamber <NUM>. The upper gas delivery device <NUM>, the upper flow generating device <NUM>, and the plenum <NUM> collectively form an upper gas delivery system <NUM>, which is configured to supply an upper gas flow <NUM> into the chamber <NUM>.

For example, as illustrated, the plenum <NUM> includes a plurality of openings <NUM> defined within the plenum side wall <NUM>, which collectively define an upper gas inlet <NUM> into the chamber <NUM>. The plurality of openings <NUM> thus enable pressurized gas within the plenum chamber <NUM> to flow through the plenum side wall <NUM> and into the chamber <NUM>. The plurality of openings <NUM> may include an array of openings that enable the upper gas flow <NUM> to flow substantially uniformly along the x-direction <NUM> (e.g., parallel to a top surface <NUM> of the build platform <NUM>, perpendicular to the z-direction <NUM>). The plurality of openings <NUM> may be sized to regulate certain flow characteristics of the upper gas flow <NUM>, such as a flow distribution, a flow rate (e.g., a mass flow rate, a volumetric flow rate), a flow velocity (e.g., in meters per second (m/s)), a flow direction or angle, or any combination thereof. For example, in some embodiments, the plurality of openings <NUM> may be sized to facilitate substantially laminar flow of the upper gas flow <NUM> along the upper portion <NUM> of the chamber <NUM>. In certain embodiments, the plurality of openings <NUM> may be in the form of circular holes, as illustrated in <FIG>. However, in other embodiments, the plurality of openings <NUM> may be arranged and shaped in a honeycomb-like structure, a sponge-like structure, or any other suitable geometric arrangement to facilitate generating the desired flow characteristics of the upper gas flow <NUM>. In yet further embodiments, the plurality of openings <NUM> may include a single opening that, for example, extends along a portion of the width <NUM>, or substantially all of the width <NUM> of the chamber <NUM>.

It should be noted that although the upper gas inlet <NUM> is defined within the plenum side wall <NUM> in the illustrated embodiment shown in <FIG>, in other embodiments, the upper gas inlet <NUM> may be defined within any other suitable portion of the chamber <NUM> or portions of the chamber <NUM>. For example, in some embodiments, the plurality of openings <NUM> is defined within the top wall <NUM>, the side wall <NUM>, the side wall <NUM>, a front wall <NUM> of the housing <NUM>, or a combination thereof, in addition to, or in lieu of, the plenum side wall <NUM>. Accordingly, in certain embodiments, the upper gas inlet <NUM> may supply the upper gas flow <NUM> into the chamber <NUM> at an angle relative to the x-direction <NUM>. In such embodiments, the AM system <NUM> may include one or more flow directing elements that are disposed within the chamber <NUM> and configured to receive the upper gas flow <NUM> from the plurality of openings <NUM> and redirect the upper gas flow <NUM> in a direction generally parallel to the x-direction <NUM>. The flow directing elements may include one or more winglets, one or more airfoils, or any other suitable flow directing system configured (e.g., shaped oriented) to redirect a flow direction of the upper gas flow <NUM>. In certain embodiments, the plenum <NUM> may be omitted from the AM system <NUM>, such that the plurality of openings <NUM> is defined within the rear wall <NUM> of the housing <NUM>, rather than the plenum side wall <NUM> of the plenum <NUM>. In such embodiments, the upper gas delivery device <NUM> may be fluidly coupled directly to the plurality of openings <NUM>, thereby enabling supply of the upper gas flow <NUM> through the plurality of openings <NUM>. As described in greater detail herein, in yet further embodiments of the AM system <NUM>, the upper gas delivery system <NUM> may be omitted from the AM system <NUM> entirely. In such embodiments, the AM system <NUM> does not include the upper gas flow <NUM>.

The embodiment of the AM system <NUM> shown in <FIG> also includes a lower gas delivery system <NUM> having a lower gas delivery device <NUM> that includes a lower flow generating device <NUM>. The lower flow generating device <NUM> may be disposed within the lower gas delivery device <NUM> and/or form a part of the lower gas delivery device <NUM>. The lower flow generating device <NUM> includes any suitable conveying device or conveying devices (e.g., one or more fluid valves, one or more pumps or blowers, or a combination thereof) that generate and/or regulate a flow rate of a gas flow and/or a pressure of a gas flow supplied by a suitable gas source, such as the gas supply line. The lower gas delivery device <NUM> fluidly couples to a lower gas inlet <NUM> defined within the rear wall <NUM> of the chamber <NUM>, proximate to an upstream end portion <NUM> of the chamber <NUM>. The AM system <NUM> includes a base plate <NUM> that extends along a length <NUM> of the chamber <NUM>. The base plate <NUM> is defined by the bottom wall <NUM> of the chamber <NUM> and a lower end portion <NUM> of the housing <NUM>. A channel <NUM> is defined within the base plate <NUM> and fluidly couples the lower gas inlet <NUM> to a channel outlet <NUM> defined within the bottom wall <NUM>. As shown in the illustrated embodiment, the channel <NUM> extends along a length <NUM> from the lower gas inlet <NUM> to the channel outlet <NUM>. Accordingly, the lower gas inlet <NUM> may receive a lower gas flow <NUM> from the lower gas delivery device <NUM> and supply the lower gas flow <NUM> to the chamber <NUM>.

The channel <NUM> is defined in part by a contoured surface <NUM> (e.g., a curved surface or an 's'-shaped surface) that extends tangentially between the lower gas inlet <NUM> and the bottom wall <NUM> adjacent the channel outlet <NUM>. As described in greater detail herein, the contoured surface <NUM> is configured to induce a fluid guiding effect, such as the Coanda effect, in the lower gas flow <NUM>, which facilitates discharging the lower gas flow <NUM> from the channel outlet <NUM> in the x-direction <NUM> (e.g., substantially parallel to the build platform <NUM>, substantially parallel to the top surface <NUM> of the build platform <NUM>), or in a direction substantially parallel to the x-direction <NUM> (e.g., in a direction ± <NUM> degrees with respect to the x-direction <NUM>). As noted above, the Coanda effect is the tendency of a flow of fluid to adhere to an adjacent flat or curved surface. Accordingly, the Coanda effect causes the lower gas flow <NUM> to adhere to the contoured surface <NUM> and flow along a length of the contoured surface <NUM>. However, the fluid guiding effect may also include any other guiding forces configured to redirect a flow trajectory of a fluid, such as static pressure differentials and/or dynamic pressure differentials along a length and/or a width of the fluid flow.

As shown in the illustrated embodiment, the lower gas inlet <NUM> is oriented cross-wise (e.g., perpendicular) to the channel outlet <NUM>. For example, because the lower gas inlet <NUM> is defined within the rear wall <NUM>, the lower gas inlet <NUM> is disposed within a plane formed by the y- and z- axes <NUM>, <NUM>. Accordingly, the lower gas inlet <NUM> is oriented parallel to the rear wall <NUM>, such the lower gas inlet <NUM> is configured to receive the lower gas flow <NUM> in the x-direction <NUM>. The channel outlet <NUM> is defined within the bottom wall <NUM>, and thus, is disposed within a plane formed by the x- and y- axes <NUM>, <NUM>, and is oriented in the z-direction <NUM>. As shown in the illustrated embodiment, the rear wall <NUM> extends perpendicular, or cross-wise to the bottom wall <NUM>. Accordingly, the lower gas inlet <NUM> is oriented perpendicular to, or cross-wise to the channel outlet <NUM>. The fluid guiding effect enables the lower gas flow <NUM> to flow along the contoured surface <NUM> (which extends tangentially from the lower gas inlet <NUM> to the bottom wall <NUM>) and discharge from the channel outlet <NUM> in the x-direction <NUM>, substantially parallel to the build platform <NUM>, even though the channel outlet <NUM> is oriented in the z-direction <NUM> (e.g., a direction substantially perpendicular to the build platform <NUM>). More specifically, the fluid guiding effect enables the lower gas flow <NUM> to follow a curvature of the contoured surface <NUM>, and thus, discharge from the channel outlet <NUM> in a flow direction that is substantially parallel to the x-direction <NUM> (e.g., in a direction oriented ± <NUM> degrees with respect to the x-direction <NUM>). It should be noted that in other embodiments, an angle between the rear wall <NUM> and the bottom wall <NUM> may be greater than, or less than <NUM> degrees. For example, an angle between the rear wall <NUM> and the bottom wall <NUM> may be between about <NUM> degrees and about <NUM> degrees. Accordingly, an angle between the lower gas inlet <NUM> and the channel outlet <NUM> may be between about <NUM> degrees and about <NUM> degrees depending on an orientation of the rear wall <NUM> relative to the bottom wall <NUM>.

After discharging from the channel outlet <NUM>, the lower gas flow <NUM> is directed along a lower portion <NUM> of the chamber <NUM> and flows across the build platform <NUM>. For clarity, it should be noted that the lower portion <NUM> of the chamber <NUM> includes any portion of the chamber <NUM>, or portions of the chamber <NUM> disposed vertically below (e.g., with respect the z-axis <NUM>) the plenum dividing wall <NUM>. For example, in some embodiments, the lower portion <NUM> may include a lower <NUM>%, lower <NUM>%, lower <NUM>%, or a lower <NUM>% of the chamber <NUM>, depending on a position of the plenum dividing wall <NUM> with respect to the z-axis <NUM>. Regardless, directing the lower gas flow <NUM> across the build platform <NUM> in a direction parallel to the build platform <NUM> (e.g., in the x-direction <NUM>) may mitigate, or substantially eliminate undesirable interaction between the lower gas flow <NUM> and the powder bed <NUM> disposed on the build platform <NUM>. For example, because the lower gas flow <NUM> is directed parallel across the build platform <NUM>, rather than at an angle toward the build platform <NUM>, the lower gas flow <NUM> may not disturb the powder bed <NUM> through vortices and/or pressure fluctuations that may be generated by the lower gas flow <NUM>.

As shown in the illustrated embodiment of <FIG>, the lower gas inlet <NUM> and the channel outlet <NUM> each include a generally rectangular shape that extends along a first width <NUM> and a second width <NUM>, respectively. The first width <NUM> and the second width <NUM> may each include a portion of the width <NUM> of the chamber <NUM>, or substantially all of the width <NUM> of the chamber <NUM> in different embodiments. While the first width <NUM> and the second width <NUM> are shown as equal in the illustrated embodiment, it should be noted that the first width <NUM> may be greater than, or less than the second width <NUM> in certain embodiments of the AM system <NUM>. For example, in some embodiments, the first width <NUM> of the lower gas inlet <NUM> may be relatively small, while the second width <NUM> of the channel outlet <NUM> is relatively large. In such embodiments, a width of the channel <NUM> may diverge in a downstream direction (e.g., in the x-direction <NUM>) from the lower gas inlet <NUM> to the channel outlet <NUM>.

One or more flow directing elements, such as fins, air foils, or the like, may be disposed within the channel <NUM> and configured to facilitate even distribution of the lower gas flow <NUM> along the second width <NUM> of the channel outlet <NUM>. Accordingly, the flow distribution elements may ensure that that a flow rate and/or a flow velocity of the lower gas flow <NUM> is substantially uniform across the width <NUM>, or a designated portion of the width <NUM> of the chamber <NUM>. Although the lower gas inlet <NUM> and the channel outlet <NUM> are each shown as a single opening that is generally rectangular in the illustrated embodiment, it should be noted that the lower gas inlet <NUM> and the channel outlet <NUM> may include any suitable quantity of separate openings. Moreover, the openings may each have a similar cross-sectional shape or a different cross-sectional shape in certain embodiments of the AM system <NUM>. For example, the channel outlet <NUM> may include a plurality of individual openings that are configured to regulate certain flow parameters of the lower gas flow <NUM>, similar to the plurality of openings <NUM> of the upper gas inlet <NUM> discussed above. The channel outlet <NUM> may include a plurality of circular openings, perforations, and/or slots, or a plurality of openings having any other suitable geometric shape, which extend along the second width <NUM> of the channel outlet <NUM>.

In further embodiments, the channel <NUM> may include a plurality of individual channels that extend between a respective inlet of the lower gas inlet <NUM> and a respective outlet of the channel outlet <NUM>. In other words, the channel <NUM> may include a plurality of fluidly independent channels disposed adjacent to one another that extend between the lower gas inlet <NUM> and the channel outlet <NUM>. The plurality of channels may fluidly couple to the lower flow generating device <NUM> using a common manifold or distribution chamber. Accordingly, the lower flow generating device <NUM> may supply the lower gas flow <NUM> to each channel of the plurality of channels. In some embodiments, one or more flow regulating elements such as orifice plates, valves, or the like, may be used to facilitate generating a velocity gradient (e.g., a gradient in terms of flow velocity or flow rate) across the lower gas flow <NUM> (e.g., across the width <NUM> of the chamber <NUM>). In such embodiments, each channel may be associated with a respective flow regulating element that is configured to enable a predetermined flow rate and/or a predetermined flow velocity of gas to enter that particular channel.

As a non-limiting example, flow regulating elements associated with channels disposed proximate to the side walls <NUM>, <NUM> of the chamber <NUM> may be adjusted such that these channels supply the lower gas flow <NUM> into the chamber <NUM> at a first flow velocity and/or a first flow rate. Flow regulating elements associated with channels disposed proximate to a central portion <NUM> of the chamber <NUM> (e.g., a portion of the chamber <NUM> extending along the x-direction <NUM> near a midpoint of the width <NUM>) may be adjusted such that these channels supply the lower gas flow <NUM> into the chamber <NUM> at a second flow velocity and/or a second flow rate. The first flow velocity and/or the first flow rate may be greater than or less that the second flow velocity and/or the second flow rate in different embodiments. Accordingly, for such embodiments, the flow regulating elements enable the AM system <NUM> to generate a velocity gradient across the lower gas flow <NUM> (e.g., along the width <NUM> of the chamber <NUM>) using a single flow generating device, such as the lower flow generating device <NUM>. In some embodiments, the AM system <NUM> may include a plurality of lower flow generating devices, where each lower flow generating device of the plurality of lower flow generating devices is coupled to a respective channel of the plurality of channels. Accordingly, each lower flow generating device may be configured to supply a predetermined flow rate and/or a predetermined flow velocity of the lower gas flow <NUM> to a particular channel of the plurality of channels. The plurality of lower flow generating devices may thus be used in addition to, or in lieu, of the flow regulating elements to generate the velocity gradient across the lower gas flow <NUM>.

The AM system <NUM> also includes a gas outlet <NUM> disposed in a downstream end portion <NUM> of the chamber <NUM> for discharging a gas flow <NUM> from the chamber <NUM>. The discharged gas flow <NUM> includes the upper gas flow <NUM>, the lower gas flow <NUM>, as well as a substantial portion of any smoke and/or particulate matter that is generated during the AM process. In the illustrated embodiment, the gas outlet <NUM> is arranged in the front wall <NUM> of the housing <NUM>, opposing the rear wall <NUM>. The gas outlet <NUM> may be arranged toward the lower portion <NUM> of the chamber <NUM>, such that the lower gas flow <NUM> travels tangentially above the build platform <NUM> and through the gas outlet <NUM>. However, in other embodiments, the gas outlet <NUM> may be disposed within the upper portion <NUM> of the chamber <NUM>. While the gas outlet <NUM> is illustrated as being rectangular in shape in <FIG> for simplicity, the gas outlet <NUM> can be of any suitable shape (e.g., circular, polygon, oval) that enables sufficient discharging of the gas flow <NUM> in other embodiments.

In some embodiments, the gas outlet <NUM> may include a plurality of openings within the front wall <NUM> of the housing <NUM>, which may be disposed near the upper portion <NUM> of the chamber <NUM>, the lower portion <NUM> of the chamber <NUM>, or both. The gas outlet <NUM> may be coupled to a suction mechanism to draw and discharge the gas flow <NUM> from the chamber <NUM>. In some embodiments, the suction mechanism may also include a filtration system that is configured to filter the gas flow <NUM>, for example, by removing any smoke and/or particulate matter suspended within the gas flow <NUM> that has been removed from the chamber <NUM>. After filtration, the gas flow <NUM> may be directed toward the upper gas delivery device <NUM> and/or the lower gas delivery device <NUM> for reuse in the upper and lower gas delivery systems <NUM>, <NUM>. It should be noted that the upper and lower gas flows <NUM>, <NUM> may include inert gasses, such as argon or nitrogen, but may additionally include any other suitable gas configured to facilitate removal of the smoke and/or particulate matter generated during operation of the AM system <NUM> from the chamber <NUM>.

As shown in the illustrated embodiment, the powder application device <NUM> is disposed near a rearward portion <NUM> of the chamber <NUM>, proximate the side wall <NUM>. Accordingly, interaction between the lower gas flow <NUM> and the powder application device <NUM> may be substantially reduced, thereby mitigating vortices that may be generated when the lower gas flow <NUM> impinges upon the powder application device <NUM>. In some embodiments, the AM system <NUM> includes an additional chamber or compartment disposed adjacent the rearward portion <NUM> of the chamber <NUM>, which receives and houses the powder application device <NUM> during inactive periods of the powder application device <NUM> (e.g., time periods during which the powder application device <NUM> does not deposit powder material onto the build platform <NUM>). In such embodiments, the powder application device <NUM> is disposed laterally behind the side wall <NUM> (e.g., with respect to the y-direction <NUM>) during such inactive periods, such that the powder application device <NUM> does not protrude into the interior volume <NUM> of the chamber <NUM>. During a deposition period of the powder application device <NUM> (e.g., a time period during which the powder application device <NUM> deposits powder material onto the build platform <NUM>), the powder application device <NUM> translates or extends out of the additional chamber and into the chamber <NUM> (e.g., via an aperture defined within the side wall <NUM>). Accordingly, the powder application device <NUM> may successively deposits layers of the powder material onto the build platform <NUM>. That is, the powder application device <NUM> translates along the y-direction <NUM> to deposit successive layers of the powder material. However, as noted above, the powder application <NUM> device may also traverse the chamber <NUM> in the x-direction <NUM>, the z-direction <NUM>, or a combination of the x-direction <NUM>, the y-direction <NUM>, and/or the z-direction <NUM>, while depositing the powder material. Regardless, after the deposition period is complete, the powder application device <NUM> may return to the additional chamber, thus removing the powder application device <NUM> from the interior volume <NUM> of the chamber <NUM>.

<FIG> is a schematic cross-sectional view illustrating an embodiment of the chamber <NUM> of the AM system <NUM>, in accordance with present embodiments. In the illustrated embodiment, an upper conduit <NUM> extends between the upper flow generating device <NUM> and the plenum <NUM>, such that the upper flow generating device <NUM> may direct a gas <NUM> (e.g., a gas forming the upper gas flow <NUM>) from the upper gas delivery device <NUM> to the plenum chamber <NUM> (e.g., through the aperture <NUM> disposed within the rear wall <NUM>). In certain embodiments, the upper flow generating device <NUM> may modulate a flow rate of the gas <NUM> supplied to the plenum chamber <NUM> and/or a pressure of the gas <NUM> within the plenum chamber <NUM>, which may affect certain flow characteristics of the upper gas flow <NUM>. Accordingly, the upper flow generating device <NUM> may be used to adjust the flow characteristics of the upper gas flow <NUM> in addition to, or in lieu of, the plurality of openings <NUM>.

For example, a target pressure of the gas <NUM> within the plenum chamber <NUM> may correspond to a predetermined flow rate and/or a predetermined flow velocity of the upper gas flow <NUM>. Accordingly, the target pressure within the plenum chamber <NUM> may be adjusted to achieve a desired flow rate and/or a desired flow velocity of the upper gas flow <NUM>. A magnitude of the target pressure corresponding to the desired flow rate and/or the desired flow velocity of the upper gas flow <NUM> may be previously determined using computer modeling simulations (e.g., via computational fluid dynamics software) and/or empirical tests. For the illustrated embodiment, AM system <NUM> includes one or more sensors <NUM> (e.g., sensors 144a, sensors 144b) configured to measure various operational parameters of the AM system <NUM>. For example, as illustrated, the plenum <NUM> includes the sensors 144a disposed within the plenum chamber <NUM>, which are configured to measure parameters indicative of a pressure of the gas <NUM>. The sensors 144a may include pressure transducers, pressure gauges, or any other suitable pressure measuring instruments. The upper flow generating device <NUM> and the sensors 144a are communicatively coupled to the controller <NUM> via one or more control transfer devices, such as wires, cables, wireless communication devices, and the like. Accordingly, the controller <NUM> may receive feedback from the sensors 144a indicative of an actual pressure of the gas <NUM>. In some embodiments, the controller <NUM> compares the actual pressure to the target pressure (e.g., a target pressure previously stored in the memory circuitry <NUM>) and instructs the upper flow generating device <NUM> to increase or decrease a flow rate of the gas <NUM> delivered to the plenum chamber <NUM> (e.g., by increasing or decreasing an operational speed of the upper flow generating device <NUM>) when the actual pressure deviates from the target pressure by a threshold amount. The controller <NUM> may thus ensure that a flowrate and/or a flow velocity of the upper gas flow <NUM> discharging from the plurality of openings <NUM> remains substantially similar to a target flow rate and/or a target flow velocity of the upper gas flow <NUM>. For example, in some embodiments, the target flow rate may be between about <NUM> and <NUM> cubic meters per minute (m<NUM>/min), between about <NUM><NUM>/min and <NUM><NUM>/min, or between about <NUM><NUM>/min and <NUM><NUM>/min, and the target flow velocity may be between <NUM> meters per second (m/s) and about <NUM>/s, between about <NUM>/s and about <NUM>/s, or between about <NUM>/s and about <NUM>/s.

It should be noted that the sensors 144a are not limited to pressure sensors, but may include any suitable types of sensors or sensors arrays that enable the controller <NUM> to monitor and adjust flow characteristics of the upper gas flow <NUM>. For example, the sensors 144a may additionally or alternatively include flow rate sensors, temperature sensors, mass flow sensors, or any other suitable sensors configured to provide the controller <NUM> with feedback indicative of flow characteristics of the upper gas flow <NUM>. In certain embodiments, the sensors 144a may be disposed externally with respect to the plenum chamber <NUM>, such as within the chamber <NUM>, near the plurality of openings <NUM>, or within a suitable portion of the upper gas delivery device <NUM>. The controller <NUM> may use the feedback acquired by the sensors 144a in accordance with the techniques discussed above to control operation of the upper flow generating device <NUM>. In addition, it should be noted that while the illustrated embodiment of <FIG> shows a single flow generating device (e.g., the upper flow generating device <NUM>) fluidly coupled to the plenum chamber <NUM>, the AM system <NUM> may include two or more flow generating devices that are each configured to facilitate the flow of gas <NUM> from the upper gas delivery device <NUM> into the plenum chamber <NUM> of the plenum <NUM>.

In certain embodiments, the housing <NUM> of the AM system <NUM> includes a chamfered portion <NUM> that extends between the top wall <NUM> and the front wall <NUM>. The chamfered portion <NUM> may facilitate directing the upper gas flow <NUM> toward the lower portion <NUM> of the chamber <NUM> (e.g., after the upper gas flow <NUM> flows across the build platform <NUM>), such that the upper gas flow <NUM> may be exhausted through the gas outlet <NUM> of the chamber <NUM>. Accordingly, the chamfered portion <NUM> may mitigate the generation of vortices in the upper gas flow <NUM> and/or a recirculation of the upper gas flow <NUM> within the chamber <NUM>, which may occur if the upper gas flow <NUM> impinges directly onto the front wall <NUM>. Although the chamfered portion <NUM> is shown as a linear section of the housing <NUM> in the illustrated embodiment, it should be noted that the chamfered portion <NUM> may include a sloped profile or a curved profile that extends between the top wall <NUM> and the front wall <NUM> in other embodiments of the AM system <NUM>. Further, it should be noted that an angle between the chamfered portion <NUM> and the front wall <NUM> (or an angle between the chamfered portion <NUM> and the top wall <NUM>) may be greater than <NUM> degrees (°) or less than <NUM>° in certain embodiments of the AM system <NUM>.

The AM system <NUM> also includes a lower conduit <NUM> that fluidly couples the lower flow generating device <NUM> to the lower gas inlet <NUM>. As described in greater detail herein, the lower flow generating device <NUM> may adjust certain flow parameters of the lower gas flow <NUM> to facilitate directing the lower gas flow <NUM> across the build platform <NUM> of the AM system <NUM>. It should be noted that upper flow generating device <NUM> and the lower flow generating device <NUM> may include a common flow generating device in certain embodiments of the AM system <NUM>, which is configured to supply gas to both the plenum chamber <NUM> and the lower gas inlet <NUM>. In such embodiments, one or more flow regulating elements (e.g., orifice plates, valves, baffles, louvers, etc.) may be used to direct gas to the plenum chamber <NUM> and the lower gas inlet <NUM> at respective target flow rates. Accordingly, the gas supplied by the common gas flow generating device may be used to generate both the upper gas flow <NUM> and the lower gas flow <NUM>. As noted above, in certain embodiments, the AM system <NUM> does not include the upper gas delivery system <NUM>. Accordingly, in such embodiments, the AM system <NUM> includes only the lower flow generating device <NUM>, or a plurality of lower flow generating devices, which are associated with the lower gas inlet <NUM>.

As shown in the illustrated embodiment, the build platform <NUM> is disposed at a first elevation <NUM> with respect to the chamber <NUM>, while the lower gas inlet <NUM> is disposed at a second elevation <NUM> with respect to the chamber <NUM>. The lower gas inlet <NUM> is disposed below the build platform <NUM> (e.g., with respect to a position along the z-axis <NUM>), such that the second elevation <NUM> of the lower gas inlet <NUM> is less than the first elevation <NUM> of the build platform <NUM>. In other words, a distance <NUM> between the lower end portion <NUM> of the housing <NUM> and the lower gas inlet <NUM> is less than a distance <NUM> between the lower end portion <NUM> and the build platform <NUM> in the illustrated embodiment of <FIG>. Therefore, the lower gas inlet <NUM> is below the build platform <NUM> by a distance <NUM>. The contoured surface <NUM> of the channel <NUM> is configured to receive the lower gas flow <NUM> at the second elevation <NUM> (at the lower gas inlet <NUM>), and discharge the lower gas flow <NUM> at the first elevation <NUM> (at the build platform <NUM>).

For example, the contoured surface <NUM> includes a concave portion <NUM> disposed downstream (e.g., with respect to a flow direction of the lower gas flow <NUM>) of the lower gas inlet <NUM>, which is followed by a convex portion <NUM> disposed downstream of the concave portion <NUM>. The concave portion <NUM> is configured to receive the lower gas flow <NUM> in the x-direction <NUM> from the lower gas inlet <NUM>. The concave portion <NUM> redirects the lower gas flow <NUM> in an intermediate direction, at an angle <NUM> relative to the lower end portion <NUM> of the housing <NUM> and the build platform <NUM>. In some embodiments, the angle <NUM> may be between about <NUM> degrees (°) and about <NUM>°, between about <NUM>° and about <NUM>° (e.g., ± <NUM>°). The contoured surface <NUM> may include an intermediate portion <NUM> that is linear and extends tangentially between the concave portion <NUM> and the convex portion <NUM> at the angle <NUM>. Accordingly, the lower gas flow <NUM> is directed along the intermediate portion <NUM> from the second elevation <NUM> toward the first elevation <NUM>. As shown in the illustrated embodiment, the convex portion <NUM> extends tangentially between the intermediate portion <NUM> and the build platform <NUM>. The fluid guiding effect causes the lower gas flow <NUM> to follow a profile of the convex portion <NUM>, such that the lower gas flow <NUM> is redirected from the intermediate direction to the x-direction <NUM>. The lower gas flow <NUM> thus discharges from the contoured surface <NUM> in the x-direction <NUM> and flows toward the build platform <NUM>.

In some embodiments, a radius of curvature <NUM> of the concave portion <NUM> and a radius of curvature <NUM> of the convex portion <NUM> are constant. For example, the radius of curvature <NUM> of the concave portion <NUM> and the radius of curvature <NUM> of the convex portion <NUM> may include a percentage of the width <NUM> of the chamber <NUM>, a percentage of the height <NUM> of the chamber <NUM>, a percentage of the length <NUM> of the chamber <NUM>, or a percentage of any other suitable dimension of the AM system <NUM>. For example, the radius of curvatures <NUM>, <NUM> may include between about <NUM>% and about <NUM>% of the length <NUM> of the chamber <NUM>, between about <NUM>% and about <NUM>% of the length <NUM> of the chamber <NUM>, between about <NUM>% and about <NUM>% of the length <NUM> of the chamber <NUM>, or between about <NUM>% and about <NUM>% of the length <NUM> of the chamber <NUM>. As a non-limiting example, in some embodiments, the radius of curvature <NUM> of the concave portion <NUM> and the radius of curvature <NUM> of the convex portion <NUM> may each be between about <NUM> centimeters (cm) and about <NUM>, between about <NUM> and about <NUM>, or about <NUM>. It should be noted that in certain embodiments, the radius of curvature <NUM> of the concave portion <NUM> may be greater than, or less than the radius of curvature <NUM> of the convex portion <NUM>. For example, the radius of curvature <NUM> of the convex portion <NUM> may be relatively large (e.g., larger than the radius of curvature <NUM> at the concave portion <NUM>), which may facilitate directing the lower gas flow <NUM> along the convex portion <NUM> via the fluid guiding effect. In yet further embodiments, a radius of curvature of the concave portion <NUM>, the convex portion <NUM>, or both, may be nonlinear, such that a slope of the concave portion <NUM> and/or a slope of the convex portion <NUM> changes along the length of the contoured surface <NUM>. In general, the contoured surface <NUM> is configured to receive the lower gas flow <NUM> in the x-direction <NUM> and at the second elevation <NUM>, direct the lower gas flow <NUM> in the intermediate direction, and utilize the fluid guiding effect to redirect the lower gas flow <NUM> from the intermediate direction to the x-direction <NUM>. Accordingly, the lower gas flow <NUM> may discharge from the contoured surface <NUM> at the first elevation <NUM>.

As noted above, the contoured surface <NUM> may extend the entire distance between the lower gas inlet <NUM> and the build platform <NUM> in certain embodiments of the AM system <NUM>. In such embodiments, a downstream end portion <NUM> of the contoured surface <NUM> may abut an upstream end portion <NUM> of the build platform <NUM>. It should be noted that a height of the build platform <NUM> may be negligible, such that an elevation of the downstream end portion <NUM> of the contoured surface <NUM> is substantially equal to an elevation (e.g., the first elevation <NUM>) of the top surface <NUM> of the build platform <NUM>. Accordingly, the lower gas flow <NUM> may discharge from the convex portion <NUM> and flow across the build platform <NUM> with no substantial hindrance. In other embodiments, the build platform <NUM> may be disposed in a flush position <NUM>, in which the build platform <NUM> is embedded within or inserted into the base plate <NUM>. In such embodiments, an elevation of the top surface <NUM> of the build platform <NUM> is equal to an elevation of downstream end portion <NUM> of the contoured surface <NUM>. Accordingly, both the downstream end portion <NUM> of the contoured surface <NUM> and the upstream end portion <NUM> of the build platform <NUM> are disposed at the first elevation <NUM>. In any case, the contoured surface <NUM> extends from the second elevation <NUM> of the lower gas inlet <NUM> to the first elevation <NUM> of the build platform <NUM>, and thus enables the lower gas flow <NUM> to flow from the lower gas inlet <NUM> toward the build platform <NUM>.

In certain embodiments, the contoured surface <NUM> does not extend the entire distance to the build platform <NUM>. In such embodiments, a portion of the bottom wall <NUM> is disposed between the downstream end portion <NUM> of the contoured surface <NUM> and the upstream end portion <NUM> of the build platform <NUM>. This portion of the bottom wall <NUM> will be referred to herein as a spacing portion <NUM>, which extends parallel to the x-direction <NUM>. The spacing portion <NUM> increases a separation distance between the channel outlet <NUM> and the powder material disposed on the build platform <NUM>. Accordingly, the spacing portion <NUM> may reduce, or substantially eliminate a likelihood of powder material, or other foreign matter generated during the AM process entering the channel outlet <NUM> during operation of the AM system <NUM>. The spacing portion <NUM> thus mitigates the aggregation of powder material and/or other foreign matter within the channel <NUM> and on the contoured surface <NUM>. In some embodiments, a length of the spacing portion may be between <NUM> centimeters (cm) and about <NUM>, between about <NUM> and about <NUM>, or greater than <NUM>. As noted above, the powder application device <NUM> may traverse the chamber <NUM> in the y-direction <NUM> to deposit powder material onto the build platform <NUM>. That is, the powder application device <NUM> travels generally parallel to the second width <NUM> (as shown in <FIG>) of the channel outlet <NUM>. This configuration may additionally mitigate undesirable powder deposition within the channel <NUM>, as the powered application device <NUM> does not traverse across the channel outlet <NUM> during each deposition period for such embodiments.

As shown in the illustrated embodiment, the AM system <NUM> includes an intermediate wall <NUM> that forms an upper portion of the channel <NUM>. The intermediate wall <NUM> is defined by a portion of the bottom wall <NUM>, a portion of the rear wall <NUM>, and an additional contoured surface <NUM> that extends between these two portions. The additional contoured surface <NUM> is offset from the contoured surface <NUM> by a predetermined offset distance. Accordingly, a height <NUM> (e.g., a distance between the contoured surface <NUM> and the additional contoured surface <NUM>) and a profile of the channel <NUM> may remain substantially equal along the length of the channel <NUM>. In some embodiments, the offset distance may be between about <NUM> and <NUM>. However, in other embodiments, the offset distance may be greater than or less than <NUM>. In yet further embodiments, the height <NUM> of the channel <NUM> may be non-uniform, such that the channel <NUM> converges or diverges (e.g., with respect to the z-axis <NUM>) from the lower gas inlet <NUM> to the channel outlet <NUM>. As a non-limiting example, a height of the channel <NUM> near the channel outlet <NUM> may be approximately one half, one third, or one quarter of the height <NUM> of the channel <NUM> proximate the lower gas inlet <NUM>. Accordingly, the dimensions of the channel <NUM> may be used to adjust certain flow parameters of the lower gas flow <NUM> in addition to, or in lieu of, the lower flow generating device <NUM>. For example, decreasing the height <NUM> of the channel <NUM> near the channel outlet <NUM> may increase a flow velocity and a pressure of the lower gas flow <NUM> discharging from the channel <NUM>. Conversely, increasing the height <NUM> of the channel <NUM> near the channel outlet <NUM> may decrease the flow velocity and the pressure of the lower gas flow <NUM> discharging from the channel <NUM>. Accordingly, the height <NUM> of the channel <NUM> may be adjusted to achieve desired flow characteristics of the lower gas flow <NUM> and/or strengthen the fluid guiding effect near the channel outlet <NUM> (e.g., across the convex portion <NUM> of the contoured surface <NUM>). The additional contoured surface <NUM> may thus facilitate guiding the lower gas flow <NUM> from the lower gas inlet <NUM> to the channel outlet <NUM>.

In some embodiments, the additional contoured surface <NUM> may induce an additional fluid guiding effect that is configured to guide the lower gas flow <NUM> in addition to, or in lieu of, the fluid guiding effect generated by the contoured surface <NUM>. For example, the additional contoured surface <NUM> may induce the Coanda effect, or any other fluid dynamics effect (e.g., fluidic pressure fluctuations) that facilitates guiding the lower gas flow <NUM> from the second elevation <NUM> to the first elevation <NUM>. In further embodiments, the contoured surface <NUM> and the additional contoured surface <NUM> may cooperate similar to a pair of cascaded airfoils to direct the lower gas flow <NUM> along a particular flow trajectory.

Advantageously, integrating the lower gas inlet <NUM> and the channel <NUM> within the base plate <NUM> of the housing <NUM> may reduce a volume of space occupied by the lower gas delivery system <NUM> within certain portions of the chamber <NUM>, such as a tooling area <NUM> disposed beneath the plenum <NUM>. For example, because the lower gas inlet <NUM> is disposed below the build platform <NUM> and the bottom wall <NUM> of the chamber <NUM> (e.g., at the second elevation <NUM>), tools <NUM> of the AM system <NUM> and/or other operational equipment of the AM system <NUM>, such as one or more replacement build platforms, may occupy substantially all of a height <NUM> of the tooling area <NUM>, without interfering with the lower gas delivery system <NUM>. Moreover, because the tools <NUM> are disposed upstream (e.g., with respect to a flow direction of the lower gas flow <NUM>) of the channel outlet <NUM>, the tools <NUM> do not obstruct a flow path of the lower gas flow <NUM>. Accordingly, fluidic turbulences within the lower gas flow <NUM> may be mitigated, or substantially eliminated, such that the lower gas flow <NUM> may flow across the build platform <NUM> at a substantially uniform flow rate and/or a substantially uniform flow velocity. In addition, integrating the channel outlet <NUM> within the bottom wall <NUM> of the chamber <NUM> allows the bottom wall <NUM> to remain substantially flat (e.g., parallel to the x-direction <NUM>) along the length <NUM> of the chamber <NUM>. Therefore, the tools <NUM> of the AM system <NUM> may traverse laterally along the length <NUM> of the bottom wall <NUM> of the chamber <NUM> without obstruction by the lower gas delivery system <NUM>.

It should be noted that the intermediate wall <NUM> may be omitted in certain embodiments of the AM system <NUM>. In such embodiments, the AM system <NUM> does not include the channel <NUM>, but rather, includes only the contoured surface <NUM> that extends between the lower gas inlet <NUM> and the build platform <NUM>. In other words, the intermediate wall <NUM> does not form a channel (e.g., the channel <NUM>) between the contoured surface <NUM> and a surface of the intermediate wall <NUM> (e.g., the additional contoured surface <NUM>). In further embodiments, the lower gas inlet <NUM> may be disposed above, rather than below the build platform <NUM>. For example, as shown in the embodiment of the AM system <NUM> illustrated in <FIG> which is not an embodiment of the invention, the lower gas inlet <NUM> may be disposed vertically above (e.g., with respect to the z-axis <NUM>) the build platform <NUM>. Accordingly, the first elevation <NUM> of the build platform <NUM> is less than the second elevation <NUM> of the lower gas inlet <NUM>. In other words, the lower gas inlet <NUM> is disposed above the build platform <NUM> by the distance <NUM>. In such embodiments, the convex portion <NUM> of the contoured surface <NUM> is disposed upstream of the concave portion <NUM> of the contoured surface <NUM>. As discussed above, the fluid guiding effect causes the lower gas flow <NUM> to adhere to a profile of the convex portion <NUM> while the lower gas flow <NUM> is directed across the contoured surface <NUM>. Accordingly, the convex portion <NUM> redirects the lower gas flow <NUM> entering the chamber <NUM> in the x-direction <NUM> (e.g., via the lower gas inlet <NUM>) to an intermediate direction (e.g., a direction toward the build platform <NUM>). The lower gas flow <NUM> is subsequently directed along the intermediate portion <NUM> of the contoured surface <NUM> toward the bottom wall <NUM> of the chamber <NUM>, and is then redirected from the intermediate direction to the x-direction <NUM> via the concave portion <NUM>. Accordingly, the lower gas flow <NUM> discharges from the concave portion <NUM> at an elevation substantially equal to the first elevation <NUM> of the build platform <NUM> and flows across the build platform <NUM> in the x-direction <NUM>.

Returning now to <FIG>, in some embodiments, the controller <NUM> is communicatively and operatively coupled to the lower flow generating device <NUM> and may be configured to instruct the lower flow generating device <NUM> to maintain a desired flow rate and/or a desired flow velocity of the lower gas flow <NUM> during operation of the AM system. In some embodiments, the desired flow rate and/or the desired flow velocity are previously determined and correspond a flow rate and/or a flow velocity of the lower gas flow <NUM> that enhances an influence of the fluid guiding effect. Accordingly, the controller <NUM> may ensure that the lower gas flow <NUM> is guided along the convex portion <NUM> during operation of the AM system <NUM>, and thus, mitigate a likelihood of flow separation between the lower gas flow <NUM> and the convex portion <NUM>. For example, computer simulation tools (e.g., computation fluid dynamics software) and/or empirical trials may be used to determine a target flow rate of the lower gas flow <NUM> and/or a target flow velocity of the lower gas flow <NUM> at which the fluid guiding effect is enhanced (e.g., a flow rate and/or a flow velocity at which substantially all of the lower gas flow <NUM> is redirected by the convex portion <NUM> of the contoured surface <NUM>). This target flow rate and target flow velocity may be stored in the memory circuitry <NUM> of the controller <NUM>. In some embodiments, the target flow rate may be between about <NUM> and <NUM> cubic meters per minute (m<NUM>/min), between about <NUM><NUM>/min and <NUM><NUM>/min, or between about <NUM><NUM>/min and <NUM><NUM>/min, and the target flow velocity may be between <NUM> meters per second (m/s) and about <NUM>/s, between about <NUM>/s and about <NUM>/s, or between about <NUM>/s and about <NUM>/s. The controller <NUM> may monitor an actual flow rate and/or an actual flow velocity of the lower gas flow <NUM> during operation of the AM system <NUM> using the sensors 144b, and may adjust an operational speed of the lower flow generating device <NUM> such that the actual flow rate and/or the actual flow velocity of the lower gas flow <NUM> is maintained within a tolerance of the target flow rate and/or the target flow velocity.

For example, the sensors 144b may be disposed within a portion of the lower gas delivery device <NUM>, the lower conduit <NUM>, the channel <NUM>, or any other suitable portion of the AM system <NUM>. The sensor <NUM> may include a flow rate sensor, a flow velocity monitor, mass flow sensor, or any other suitable sensor configured to provide the controller <NUM> with feedback indicative of an actual flow rate and/or an actual flow velocity of the lower gas flow <NUM>. For example, in certain embodiments, if the actual flow rate and/or the actual flow velocity of the lower gas flow <NUM> deviates from the target flow rate and/or the target flow velocity by a more than a predetermined threshold amount, the controller <NUM> instructs the lower flow generating device <NUM> to increase or decrease a flow rate and/or a flow velocity of the lower gas flow <NUM> (e.g., by increasing or decreasing the operational speed of the lower flow generating device <NUM>), such that the actual flow rate and/or the actual flow velocity of the lower gas flow <NUM> approaches the target flow rate and the target flow velocity, respectively.

In some embodiments, the controller <NUM> adjusts a flow rate and/or a flow velocity of the lower gas flow <NUM> based on thermodynamic properties of the lower gas flow <NUM>, based on a composition of the lower gas flow <NUM>, or both. For example, a surface temperature of the contoured surface <NUM>, a temperature of the lower gas flow <NUM>, and/or a composition of the lower gas flow <NUM> may affect a target flow rate and/or a target flow velocity of the lower gas flow <NUM> at which the fluid guiding effect is strengthened. Similar to the discussion above, computer simulation tools, empirical trials, or both may be used to determine a correlation between the thermodynamic properties and the compositional properties of the lower gas flow <NUM> and a stability of the fluid guiding effect (e.g., an ability of the lower gas flow <NUM> to adhere to the convex portion <NUM>). Correlations between the thermodynamic and compositional properties of the lower gas flow <NUM> and the corresponding target flow rate and target flow velocity of the lower gas flow <NUM> may be stored in the memory circuitry <NUM> (e.g., as equations, look-up tables, etc.).

Similar to the discussion above, the controller <NUM> may monitor the thermodynamic and compositional properties of the lower gas flow <NUM> during operation of the AM system <NUM> via the sensors 144b to determine whether adjustments in the flow rate and/or the flow velocity of the lower gas flow <NUM> are desired. For example, the sensors 144b may further include, but are not limited to, temperature sensors, such as such a thermocouples, resistance temperature detectors, or thermistors, and gas detector sensors, such as electrochemical sensors, ultrasonic sensors, or particulate/smoke sensors. The controller <NUM> may compare whether an actual flow rate and/or an actual flow velocity of the lower gas flow <NUM> corresponds to the respective target values of the flow rate and/or the flow velocity that are associated with the measured thermodynamic and compositional properties of the lower gas flow <NUM>. If the actual flow rate and/or the actual flow velocity of the lower gas flow <NUM> deviates from the target flow rate and/or the target flow velocity, the controller <NUM> instructs the lower flow generating device <NUM> to increase or decrease a flow rate and/or a flow velocity of the lower gas flow <NUM>, such that the actual flow rate and/or the actual flow velocity of the lower gas flow <NUM> approaches the target value(s). Accordingly, the controller <NUM> may ensure that the fluid guiding effect within the lower gas flow <NUM> is preserved during operation of the AM system <NUM>. Additionally or otherwise, the controller <NUM> may adjust the flow rate and/or the flow velocity of the lower gas flow <NUM>, the upper gas flow <NUM>, or both, using feedback generated by the sensors 144b indicative of any suitable operating parameter of the AM system <NUM>.

With the foregoing in mind, <FIG> is a flow chart of an embodiment of a process <NUM> whereby the AM system <NUM> may be operated during fabrication of an article. The following discussion references element numbers used throughout <FIG>. It should be noted that one or more of the steps of the process <NUM> may be stored in the memory circuitry <NUM> and executed by the processing circuitry <NUM> of the controller <NUM>. For the embodiment illustrated in <FIG>, the process <NUM> begins with depositing (step <NUM>) a quantity of a powder material onto the build platform <NUM> within the chamber <NUM> of the AM system <NUM>. For example, the controller <NUM> instructs the powder application device <NUM> to deposit the powder material onto the build platform <NUM>. The controller <NUM> instructs the positioning system <NUM> to move the powder application device <NUM> and/or the build platform <NUM> to any suitable positions relative to one another along the x-, y-, and z- axis <NUM>, <NUM>, <NUM>, or a combination thereof, to deposit the powder material in a layer-by-layer manner during each deposition period of the powder application device <NUM>.

The illustrated embodiment of the process <NUM> continues with supplying (step <NUM>) the lower gas flow <NUM> into the chamber <NUM>. For example, the controller <NUM> instructs the associated gas delivery system (e.g., the lower gas delivery system <NUM>) to supply the lower gas flow <NUM> into the chamber <NUM> (e.g., via the lower gas inlet <NUM>). By way of specific example, the controller <NUM> instructs the lower gas delivery system <NUM> to control the flow characteristics of the lower gas flow <NUM>, such as flow distribution, flow rate (e.g., mass flow rate, volume flow rate), flow temperature, or any combination thereof. The method includes directing (step <NUM>) the lower gas flow <NUM> along the contoured surface <NUM> from the second elevation <NUM> of the lower gas inlet <NUM> to the first elevation <NUM> of the build platform <NUM>. For example, as discussed above, the contoured surface <NUM> is configured (e.g., shaped, arranged) to induce the fluid guiding effect, such that the convex portion <NUM> of the contoured surface <NUM> may be used together with the concave portion <NUM> to adjust a flow direction of the lower gas flow <NUM>. Accordingly, the convex portion <NUM> and the concave portion <NUM> of the contoured surface <NUM> may cooperate to direct the lower gas flow <NUM> from the second elevation <NUM> to the first elevation <NUM>. In some embodiments, the controller <NUM> may adjust a flow rate of the lower gas flow <NUM> (e.g., via the lower flow generating device <NUM>), such that an actual flow rate of the lower gas flow <NUM> is substantially equal to a target flow rate that is favorable to generate of the fluid guiding effect. For example, if the actual flow rate of the lower gas flow <NUM> exceeds or falls below the target flow rate by a threshold amount, the fluid guiding effect may not sufficiently guide the lower gas flow <NUM> along a curvature of the convex portion <NUM>, such that the lower gas flow <NUM> turbulently discharges into the chamber <NUM> and does not traverse substantially parallel to the build platform <NUM>. Accordingly, the controller <NUM> may ensure that the fluid guiding effect is preserved during the desired portion of the operation of the AM system <NUM> by maintaining the actual flow rate of the lower gas flow <NUM> substantially similar to the target flow rate. In certain embodiments, the controller <NUM> also instructs the lower gas delivery system <NUM> to control content (e.g., argon, nitrogen, any other suitable inert gas, or a combination thereof) of the lower gas flow <NUM>.

In the illustrated embodiment, the process <NUM> includes supplying (step <NUM>) an upper gas flow into the chamber <NUM>. For example, the controller <NUM> instructs the associated gas delivery system (e.g., the upper gas delivery system <NUM>) to supply the upper gas flow <NUM> into the chamber <NUM>. By way of specific example, the controller <NUM> instructs the upper gas delivery system <NUM> to control the flow characteristics of the upper gas flow <NUM>, such as flow distribution, flow rate (e.g., mass flow rate, volume flow rate), flow temperature, or any combination thereof. In certain embodiments, the controller <NUM> instructs the upper gas delivery system <NUM> to control content (e.g., argon, nitrogen, any other suitable inert gas, or a combination thereof) of the upper gas flow <NUM>. As noted above, certain embodiments of the AM system <NUM> do not include the upper gas delivery system <NUM>. Accordingly, in such embodiments, the process <NUM> does not include the step <NUM>.

In some embodiments, the controller <NUM> may instruct the upper and lower gas delivery systems <NUM>, <NUM> to control the flow velocities of the upper gas flow <NUM> and the lower gas flow <NUM>, such that a ratio between the two gas flow velocities is controlled at a desirable value or range. For example in some embodiments, the flow velocity of the lower gas flow <NUM> is in a range between about <NUM> times and about <NUM> times the flow velocity of the upper gas flow <NUM>, between about <NUM> times and about <NUM> times the flow velocity of the upper gas flow <NUM>, or about <NUM> times the flow velocity of the upper gas flow <NUM>. In certain embodiments, the ratio between the lower gas flow <NUM> and the upper gas flow <NUM> may be tuned to facilitate evacuating smoke and/or particulate matter from the chamber <NUM> via the gas outlet <NUM>.

The illustrated embodiment of the process <NUM> includes selectively applying (step <NUM>) a focused energy beam to the quantity of a powder material deposited on the build platform <NUM>. For example, the controller <NUM> instructs the energy generating system <NUM> to apply the focused energy beam <NUM>, such as a laser beam, to portions of the powder bed <NUM>. The focused energy beam <NUM> selectively melts and/or sinters the powder material of the powder bed <NUM> in a predefined manner to form a solidified layer while the upper and/or lower gas flows <NUM>, <NUM> are supplied.

In some embodiments, the supplying the lower gas flow <NUM> in the step <NUM>, directing the lower gas flow <NUM> along the contoured surface <NUM> in the step <NUM>, and supplying the upper gas flow <NUM> in the step <NUM> may be performed simultaneously. In some embodiments, supplying the lower gas flow <NUM> in the step <NUM> and directing the lower gas flow <NUM> along the contoured surface <NUM> in the step <NUM> may be performed before or after supplying the upper gas flow <NUM> in the step <NUM>. In some embodiments, the applying the focused energy beam <NUM> in the step <NUM> may be performed simultaneously to supplying the lower gas flow <NUM> and directing the lower gas flow <NUM> along the contoured surface <NUM> in the steps <NUM> and <NUM>, and supplying the upper gas flow <NUM> in the step <NUM>. In some embodiments, applying the focused energy beam <NUM> in the step <NUM> may be performed before supplying the lower gas flow <NUM> and directing the lower gas flow <NUM> along the contoured surface <NUM> in the steps <NUM> and <NUM> or before supplying the upper gas flow <NUM> in the step <NUM>. In some embodiments, the process <NUM> may repeat the steps <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> to form additional solidified layer on the previously formed solidified layer. In some embodiments, the process <NUM> may include performing the steps <NUM>, <NUM>, and <NUM> every time after performing the step <NUM>. In some embodiments, the process <NUM> may include repeating the steps <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> multiple times to form successive additional solidified layers to form the desired article (e.g., applying the focused energy beam <NUM> in the step <NUM> is continuously performed while suppling the lower gas flow <NUM> in the step <NUM>, directing the lower gas flow along the contoured surface <NUM> in the step <NUM>, and supplying the upper gas flow <NUM> in the step <NUM>).

The technical effects of the present disclosure include improving the performance and efficiency of an AM system by removing from the chamber smoke and/or other particulate matter generated during the AM process. The disclosed AM system employs a combination of an upper gas flow that is supplied from a side wall in the upper portion of the chamber and is directed substantially parallel to a build platform, and a lower gas flow that is supplied from below or above the build platform and is directed toward the build platform via a contoured surface. The contoured surface is configured to utilize the fluid guiding effect to direct the lower gas flow from a lower gas inlet to the build platform, such that the lower gas flow is directed across the build platform in a direction substantially parallel to the build platform. Introducing the lower gas flow into the chamber via the contoured surface may mitigate an amount of space occupied by a lower gas delivery system within the chamber. Accordingly, an amount of usable volume within the chamber of the AM system is enhanced. Moreover, directing the lower gas flow substantially parallel to the build platform may mitigate interaction between the lower gas flow and a powder bed disposed on the build platform. The combination of the upper and lower gas flows may thus substantially reduce or eliminate gas recirculation within the chamber, and facilitate the exhaust of smoke and/or particulate matter from inside the chamber through an exhaust outlet of the AM system.

Claim 1:
An additive manufacturing system (<NUM>), comprising:
a housing (<NUM>) defining a chamber (<NUM>);
a build platform (<NUM>) disposed in a lower portion (<NUM>) of the chamber (<NUM>) at a first elevation (<NUM>) with respect to the chamber (<NUM>);
a lower gas inlet (<NUM>) disposed proximate an upstream end portion (<NUM>) of the chamber (<NUM>) and configured to supply a lower gas flow (<NUM>), wherein the lower gas inlet (<NUM>) is disposed at a second elevation (<NUM>) with respect to the chamber (<NUM>);
a contoured surface (<NUM>) extending between the lower gas inlet (<NUM>) and the build platform (<NUM>) and configured to direct the lower gas flow (<NUM>) from the second elevation (<NUM>) to the first elevation (<NUM>), wherein the contoured surface (<NUM>) discharges the lower gas flow (<NUM>) in a direction (<NUM>) substantially parallel to the build platform (<NUM>);
one or more gas delivery devices (<NUM>) coupled to the lower gas inlet (<NUM>) and configured to regulate one or more flow characteristics of the lower gas flow (<NUM>); and
a gas outlet (<NUM>) disposed in a downstream end portion of the chamber (<NUM>), wherein the gas outlet (<NUM>) is configured to discharge the lower gas flow (<NUM>) from the chamber (<NUM>);
characterised in that the additive manufacturing system further comprises: an additional contoured surface (<NUM>) offset from the contoured surface (<NUM>) by a distance (<NUM>) to define a channel (<NUM>) extending a length from the lower gas inlet (<NUM>) to a channel outlet (<NUM>) defined within a bottom wall (<NUM>) of the chamber (<NUM>).