Patent Description:
Additive manufacturing, also called three dimensional (<NUM>-D) printing, encompasses many methods to "print" three dimensional objects by depositing layer upon layer of material and fusing them together. The technology has progressed so that complex industrial end-use parts can now be fabricated. Additive manufacturing techniques include, among others, directed energy deposition, binder jetting, material extrusion, powder bed fusion, sheet lamination, material jetting, and vat photo polymerization. Directed energy deposition, for example, precisely deposits a layer of material, such as a powdered metal layer. During deposition, a laser or electron beam thermally fuses the powdered metal. By continuing to precisely deposit powdered metal layers and fusing them together, a desired <NUM>-D object or component can be fabricated within a build chamber.

Because additive manufacturing can be used to fabricate final end use parts, it has become an important alternative to machining, casting, and injection molding. It can be used for the production of metal, composite, and polymer components for the most demanding of applications. As with any manufacturing process, undesirable internal defects such as voids, cracks, and porosity may sometimes be introduced during fabrication. Detection of these defects, however, must wait for completion of the additive manufacturing process. Using nondestructive methods such as computer tomography or ultrasonic techniques, defects in a completed object fabricated by additive manufacturing can be detected.

<CIT> describes an apparatus for manufacturing a three dimensional shaped object includes: a manufacturing unit that manufactures a three dimensional shaped object in which a plurality of solidified layers are built up together by repeating to manufacture a solidified layer, which is layered, by performing solidification processing upon a material that is positioned in a region set according to a shape of the three dimensional shaped object that is to be manufactured, to supply a new material upon an upper portion of the solidified layer that has been manufactured, to perform the solidification processing upon the new material and thus to manufacture a new solidified layer; and an inspecting unit that inspects the solidified layer that has already been built up, while the plurality of solidified layers are being built up together.

According to the present teachings, a method for detecting defects during additive manufacturing is provided as defined in claims <NUM>, <NUM> and <NUM>. According to the present teachings, an inspection system for additive manufacturing is provided and defined in claims <NUM> and <NUM>.

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate the present disclosure and together with the description, serve to explain the principles of the present disclosure.

Reference will now be made in detail to exemplary implementations of the present disclosure, examples of which are illustrated in the accompanying drawings. In the following description, reference is made to the accompanying drawings that form a part thereof, and in which is shown by way of illustration specific exemplary implementations in which the present disclosure may be practiced. These implementations are described in sufficient detail to enable those skilled in the art to practice the present disclosure and it is to be understood that other implementations may be utilized and that changes may be made without departing from the scope of the present disclosure. The following description is, therefore, merely exemplary.

Currently, additively manufactured objects must complete fabrication and be removed from the build chamber before they can be inspected. Continuing fabrication of an object with an internal defect, however, wastes time, material, and money. Removing the object from the build chamber prior to completion of fabrication for inspection, however, is difficult and time consuming. In some additive manufacturing methods, such as those that require an inert atmosphere or vacuum in the build chamber, removing the object prior to completion cannot be done without irreparable damage to the object. Furthermore, the build chamber can contain smoke, particles, and liquids that can impeded even visual inspection during additive manufacturing. Implementations of the present disclosure address the need for a system and method to nondestructively inspect an object in real time as it is being fabricated by additive manufacturing.

The disclosed x-ray based system and method can nondestructively detect defects within an object in real time, as the object is being fabricated, by additive manufacturing. Inspection can be accomplished without needing to modify or otherwise disrupt the environment inside the build chamber, for example a vacuum, inert gas, or elevated temperature environment. Being x-ray based, the disclosed system and method is not limited by the type and size of the build chamber or the type of additive manufacturing technique being used. Moreover, the disclosed system and method is not affected by smoke, particles, or liquid that may be present in the build chamber. Real time detection of defects during additive manufacturing can save time, material, and money by stopping or correcting the process immediately upon detection of a defect instead of waiting until completion of the additive manufacturing process.

<FIG> shows an inspection system <NUM> according to the present invention. Inspection system <NUM> includes an x-ray tube <NUM>, an aperture <NUM>, an actuator <NUM>, a linear x-ray detector array <NUM>, a computer <NUM>, a controller <NUM>, and an image analyzer <NUM>.

X-ray tube <NUM> is positioned adjacent to and outside of a build chamber <NUM>. X-ray tube <NUM> can be, for example, an x-ray tube used for baggage screening in airports. The type of x-ray tube <NUM> can depend on the objected being additively manufactured, its composition, and the type of additive manufacturing technique being used. For example, x-ray tube <NUM> can be glass or ceramic and have power ranging from about <NUM> to about <NUM> watts and voltages ranging from about <NUM> to about <NUM> kV. Suitable x-ray tubes are manufactured by, for example, Phillips, Varian, and General Electric. X-ray tube <NUM> further includes a cooling system, for example, circulating water or closed cycle cooling to control the temperature of the x-ray tube.

Aperture <NUM> is positioned between build chamber <NUM> and x-ray tube <NUM> to provide a collimated fan beam directed to an object being fabricated inside of build chamber <NUM>. Aperture <NUM> can be formed of any material that blocks x-rays, including but not limited to lead, steel, and tungsten. Aperture <NUM> is controlled by controller <NUM> to provide pulses of about <NUM> second to about <NUM> seconds directed at an object being fabricated inside of build chamber <NUM>. Aperture <NUM> can be, for example, a linear aperture formed of lead or steel.

Actuator <NUM> is disposed within a build chamber <NUM> and either directly or indirectly supports the object being fabricated. Actuator <NUM> can be a rotary actuator, such as a turntable, that rotates under the control of controller <NUM>, at a speed from about one revolution per second to about one revolution per <NUM> minutes. This allows the x-ray pulse to interact with the entire volume of the object being fabricated. Actuator <NUM> can be a motorized turntable with an optical encoder that provides accurate positioning so the x-ray image can correlate to the positon of the object being formed inside of build chamber <NUM>. Alternatively, actuator <NUM> can be a linear actuator that supports and moves the object being fabricated in a linear direction, for example, into and out of the page, as shown in <FIG>. The linear actuator can move under the control of controller <NUM> at a speed from about <NUM>/sec to about <NUM>/minute to allow the x-ray pulse to interact with the entire volume of the object being fabricated. For example, the linear actuator can move the object being fabricated so that the entire volume of the object is scanned by the x-ray pulse.

Linear x-ray detector array <NUM> is positioned outside of build chamber <NUM> to detect the x-ray pulse after it passes through and interacts with an object being fabricated on actuator <NUM>. Linear x-ray detector array <NUM> can be, for example, a one-dimensional x-ray detector consisting of at least one row of x-ray sensitive detectors. Data from linear x-ray detector array <NUM> is digitized and sent to a computer <NUM> and analyzed by image analyzer <NUM>. By moving either the object being fabricated or the detector in a direction perpendicular to the length of linear x-ray detector array <NUM>, a two dimensional image of the object can be created. As shown in <FIG>, actuator <NUM> is a turntable that rotates the object being fabricated in a direction perpendicular to the length dimension of linear x-ray detector array <NUM>. Linear x-ray detector array <NUM> can be, for example, a silicon (Si) or complementary metal-oxide-semiconductor (CMOS) based detector with scintillating materials on top. Scintillating materials can be, for example, Csl:Na, Gd<NUM>O<NUM>S, or CaWO<NUM>, to convert x-rays to visible light. In the case where actuator <NUM> is a linear actuator, the linear actuator moves the object being fabricated in a direction into and out of the page, so that the entire volume of the object being fabricated is scanned by the linear x-ray pulse and the x-rays are detected by linear x-ray detector array <NUM> subsequent to the x-rays interacting with the object being fabricated.

Inspection system <NUM> further includes computer <NUM>, controller <NUM>, and image analyzer <NUM>. Computer <NUM> is operably coupled to x-ray tube <NUM>, aperture <NUM>, actuator <NUM>, and linear x-ray detector array <NUM>. Computer <NUM> includes processors and a memory system including one or more non-transitory computer readable media storing instructions that, when executed, synchronizes actions by x-ray tube <NUM>, aperture <NUM>, actuator <NUM>, and linear x-ray detector array <NUM>. In particular, computer <NUM>, through controller <NUM>, synchronizes via processors and software, the rotation or linear movement of actuator <NUM> with the exposure time of linear x-ray detector array <NUM> to maintain regular image geometry. This provides accurate positioning so the x-ray image can correlate with the position of the object being formed for pinpointing the defect location. This also allows accurate determination of when failure occurs in the additive manufacturing process. Controller <NUM> further controls aperture <NUM> to provide an x-ray pulse having the desired pulse width and controls operation of x-ray tube <NUM> to provide the desired energy.

Image analyzer <NUM> can include, for example, software to create x-ray images from data received from linear x-ray detector array <NUM>. Image analyzer <NUM> can further include software to identify defects in the x-ray images, for example, pattern recognition software that compares the x-ray images to defect-free x-ray images. For example, by comparing an x-ray image of the object being formed to an x-ray image of a defect free object, the pattern recognition software can identify anomalies or defects, such as unplanned voids or inconsistencies, in the x-ray image of the object being formed. One of ordinary skill in the art will understand that other components may be included in inspection system <NUM>. For example other software/devices can be used to capture, manipulate, analyze, and display the x-ray images or to control other devices such as the hardware related to the additive manufacturing system including build material deposition and fusing.

Build chamber <NUM>, shown in cross section in <FIG>, is generally part of an additive manufacturing system. It can take on many forms depending on the type of additive manufacturing technique, but is generally an enclosure in which additive manufacturing occurs. Build chamber <NUM> can range from a simple glass or polymer enclosure to a complex enclosure in which temperature and/or pressure and/or atmospheric content is tightly controlled. An advantage of the disclosed system and method, is that it is independent of the type of build chamber because x-rays can penetrate most materials.

<FIG> shows a method <NUM> for nondestructive inspection of an object during fabrication by additive manufacturing according to the present invention. Method <NUM> is described herein with respect to a metal powder fed additive manufacturing system <NUM> shown in <FIG>. Metal powder fed additive manufacturing systems are also known as laser cladding, directed energy deposition, and laser metal deposition systems. One of ordinary skill in art will understand that reference to metal powder fed system <NUM> is for descriptive purposes and that the disclosed system and method can be used in other types of additive manufacturing systems and is not limited to additive manufacturing of metal objects.

At <NUM> of method <NUM> shown in <FIG>, deposition and fusing of material to form an object by additive manufacturing is paused. <FIG> shows a metal powder fed additive manufacturing system <NUM> including a build chamber <NUM>, a metal powder feeder <NUM>, and a laser beam <NUM>. During additive manufacturing, metal powder feeder <NUM> deposits metal powder while laser beam <NUM> fuses the metal powder at the surface of an object <NUM> being formed layer by layer. Metal powder feeder can include, for example, a nozzle mounted on a <NUM> or <NUM> axis arm. The type of laser can depend on the powdered metal being deposited. Because directed energy deposition systems often require an inert atmosphere, access to build chamber <NUM> during fabrication by additive manufacturing is limited.

Real time, nondestructive inspection of object <NUM> during additive manufacturing by metal powder fed system <NUM> can be accomplished by incorporating an x-ray tube <NUM>, a linear aperture <NUM>, an actuator <NUM>, a linear x-ray detector array <NUM>, a computer <NUM>, a controller <NUM>, and image analyzer <NUM>. Additive manufacturing systems, for example metal powder fed system <NUM> used for descriptive purposes herein, may already include a computer and controller that can be utilized. One of ordinary skill in the art will understand that software or hardware components may need to be added to the existing computer and controller of the additive manufacturing system to incorporate control of x-ray tube <NUM>, linear aperture <NUM>, actuator <NUM>, and/or linear x-ray detector array <NUM>. Alternatively, another computer and controller, separate from the computer and controller of the additive manufacturing system, can be used.

At <NUM> of method <NUM>, metal powder feeder <NUM> pauses depositing metal powder and fusing by laser beam <NUM>, for example by turning off the laser that provides laser beam <NUM> or redirecting laser beam <NUM> away from object <NUM>. Build chamber <NUM> does not need to be opened, the environment inside does not need to be changed, and object <NUM> does not need to be removed from the build chamber. This can minimize the amount of time the additive manufacturing process is paused. Pausing the additive manufacturing process can be simply stopping deposition and fusing of the build material for a brief period of time, for example, after formation of one layer and prior to formation of the next layer. When to pause the additive manufacturing process can be determined based on a number of factors including, but not limited to, the size and complexity of the object being fabricated, the number of inspections desired, and the type of additive manufacturing being used. For example, pausing at <NUM> can occur subsequent to fabrication of a complex portion of object <NUM> but prior to completion of fabrication of object <NUM>.

At <NUM> of method <NUM>, actuator <NUM>, such as a turntable, rotates object <NUM> in a direction perpendicular to a length dimension of linear x-ray detector array <NUM>. Controller <NUM> can control the speed of rotation, as well as the start and stop of the rotation. Rotation of actuator <NUM> can begin either before, during, or after x-rays interact with object <NUM>. The speed of rotation can depend on the size of object <NUM> and/or the x-ray pulse width and can range from about one revolution per second to about one revolution per <NUM> minutes.

Where actuator <NUM> is a linear aperture, actuator <NUM> moves object <NUM> in a linear direction perpendicular and between linear x-ray detector array <NUM> and x-ray tube <NUM>. Controller <NUM> can control the linear speed, as well as the start and stop of the linear motion. Movement of object being formed <NUM> by actuator <NUM> can begin either before, during, or after x-rays interact with object <NUM>. The speed of movement can depend on the size of object <NUM> and/or the x-ray pulse width and can range from about <NUM>/sec to about <NUM>/min.

At <NUM> of method <NUM>, an x-ray pulse is directed towards object <NUM>. The x-ray pulse can occur at a time T<NUM>. Time T<NUM> is subsequent to a time T<NUM> and prior to a time TF, wherein time T<NUM> is a start of additive manufacturing of object <NUM> and time TF is a completion of additive manufacturing of object <NUM> within build chamber <NUM>. Referring to <FIG>, x-rays are generated by x-ray tube <NUM>. Linear aperture <NUM>, under the control of controller <NUM>, provides a collimated fan shaped x-ray pulse that interacts with object <NUM> as it is being rotated by actuator <NUM>. The x-ray pulse can have a pulse duration of about <NUM> second to about <NUM> seconds and an energy of about <NUM> to about <NUM> keV. Current can range from about <NUM> to about <NUM> mA. The x-ray pulse duration allows x-rays to interact with the object being formed as the object is being rotated or moved linearly. Factors influencing pulse width include the size of the object being formed and the speed of rotation or linear movement. Typically, a larger object or slower rotation or movement will require a longer pulse width. Energy and current of the x-ray pulse are determined by the size and composition of the object being formed so that the x-rays can penetrate the object being formed and the build chamber before being detected. Linear aperture <NUM> provides a collimated fan beam having a narrow width. The collimated fan beam can further have a length, for example, long enough to inspect object <NUM> at its largest dimensions when fabrication is completed. The path and pulse shape of the x-ray pulse are depicted in <FIG> as an x-ray pulse <NUM>.

At <NUM> of method <NUM>, x-ray pulse <NUM> is detected by linear x-ray detector array <NUM>. The speed of actuator <NUM> moving object <NUM> and the pulse width of x-ray pulse <NUM> allow linear x-ray detector array <NUM> to detect the x-ray subsequent to interaction with an entire volume of object <NUM>. For example, where actuator <NUM> is a turntable, the turntable can rotate object <NUM> one half turn to allow x-ray pulse <NUM> to interact with object <NUM>. As used herein, one half turn refers to object <NUM> rotating one half of one full rotation with respect to turntable or object <NUM>. Because x-rays will pass completely through object <NUM>, the one half turn will allow x-ray pulse <NUM> to interact with the entire volume of object <NUM>. In another example, actuator <NUM> can rotate object <NUM> one full turn or more. The data collected by linear x-ray detector array <NUM> is sent to computer <NUM>. At this point, controller <NUM> under the direction of computer <NUM> can stop rotation of actuator <NUM>. Controller <NUM> controls actuator <NUM>, whether a turntable or linear actuator, so that object <NUM> is at the same position after rotation or linear movement. In other words, controller <NUM> returns object <NUM> to the same position relative to metal powder feeder <NUM> and laser beam <NUM> so that additive manufacturing can continue.

At <NUM> of method <NUM>, an x-ray image is created based on the x-rays detected by linear x-ray detector array <NUM>. Using signals provided by linear x-ray detector array <NUM>, an x-ray image representing a volume of object <NUM> can be created. The x-ray image can be, for example, a digital image created by image analyzer <NUM>. The x-ray image is analyzed at <NUM> of method <NUM> by image analyzer <NUM>. For example, image analyzer <NUM> can use pattern recognition to compare the x-ray image of object <NUM> to control image, for example, an x-ray image of an object with no defects. Defects of about <NUM> and larger can be detected.

If a defect is detected in object <NUM>, additive manufacturing can be stopped at <NUM>. Stopping the additive manufacturing process at this point, prior to completion of fabrication, can save time, material, and cost.

If a defect is not detected in object <NUM>, the additive manufacturing can resume fabrication of object <NUM>, as shown at <NUM> of method <NUM>. Referring to <FIG>, resuming additive manufacturing means that actuator <NUM>, for example, the turntable, under the direction of controller <NUM>, has stopped rotating and metal powder feeder <NUM> begins to deposit metal powder while laser beam <NUM> fuses the metal powder at the surface of object <NUM>. One of ordinary skill in the art will understand that fabrication can resume at any time after detection of the x-rays by linear x-ray detector array <NUM>. In other words, additive manufacturing can resume before completion of the analysis of whether a defect exists.

At <NUM> of method <NUM>, fabrication of object <NUM> can continue to completion. If another inspection is desired, for example at a time T<NUM>, where T<NUM> is subsequent to time T<NUM> and prior to time TF , fabrication of object <NUM> can again be paused and can return to <NUM> of method <NUM> as shown in <FIG>. Operations <NUM> thru <NUM> of method <NUM> can then be repeated as desired or until fabrication is complete. In other words, between time T<NUM> and TF and subsequent to T<NUM>, x-rays can be directed at object <NUM> and x-ray images created as many times as desired. For example, subsequent to time T<NUM> and prior to time TF, x-rays can be directed at object <NUM> and x-ray images created at a time TN where time TN is an integer greater than <NUM>. For small or non-complex shapes, only one inspection may be desired. For a large or complex shape and/or for an object formed of expensive build materials, the additive manufacturing process can be paused and the object inspected, for example, <NUM> times so that <NUM> x-ray images are formed at times T<NUM> thru T<NUM>, respectively. Furthermore, when during the fabrication process each of the pauses occurs can also be determined as desired. For example, T<NUM> (or TN) can be set to occur after fabrication of a particularly complex portion of object <NUM>. Additionally, the timing of multiple pauses of the additive manufacturing process and inspection of the object does not have to be evenly spaced and can occur any time during fabrication.

As disclosed herein, some or all of method <NUM> can be advantageously automated. For example, resuming or stopping the additive manufacturing process is accomplished without an operator by using, for example, computer <NUM>, controller <NUM>, and image analyzer <NUM>. Determining whether a defect exists using image processing and pattern recognition software can increase consistency of results. If desired, however, a trained technician can be used to perform the inspection and/or determination of whether a defect exists.

<FIG> and <FIG> show another inspection system and method used for real time inspection during additive manufacturing, according to the present invention. Instead of rotating the object being formed, here the object being formed is stationary while one or both of the x-ray tube and the linear x-ray detector array is moved. As before, the inspection system and method are described with reference to metal powder fed system <NUM>. Metal powder fed system <NUM> includes a build chamber <NUM>, a fabrication stand <NUM>, a metal powder feeder <NUM>, and a laser beam <NUM>. Metal powder feeder <NUM> can include, for example, a nozzle mounted on a <NUM> or <NUM> axis arm. The type of laser can depend on the powdered metal being deposited. Because directed energy deposition systems often require an inert atmosphere, access to build chamber <NUM> during fabrication by additive manufacturing is limited. An x-ray tube <NUM>, an aperture <NUM>, a linear x-ray detector array <NUM>, a computer <NUM>, a controller <NUM>, and an image analyzer <NUM> can be incorporated into metal powder fed system <NUM>. The path and pulse shape of the x-ray pulse provided by x-ray tube <NUM> depicted in <FIG> as an x-ray pulse <NUM>. Additionally, an x-ray tube actuator <NUM> can be used to move one or both of x-ray tube <NUM> and aperture <NUM>. And, linear x-ray detector array aperture <NUM> can be used to move linear x-ray detector array <NUM>.

In this system, fabrication stand <NUM> remains stationary and can support an object being fabricated <NUM>. For example, x-ray tube <NUM> and linear x-ray detector array <NUM> can both move linearly. Alternatively, one of x-ray tube <NUM> and linear x-ray detector array <NUM> can rotate while the other moves in an arc to maintain a same relative distance between the two. Moving the x-ray tube and the linear x-ray detector array relative to the stationary fabrication stand can reduce disruption of the additive manufacturing process because the change in relative position of object being fabricated <NUM> to the positions of metal powder feeder <NUM> and laser beam <NUM> can be minimized.

To facilitate linear, arc, or rotational motion of one or both of x-ray tube <NUM> and linear x-ray detector array <NUM>, actuators can be used. For example, x-ray tube <NUM> can be attached to x-ray tube actuator <NUM> that moves both x-ray tube <NUM> and aperture <NUM> in a linear manner, for example into and out of the page depicted in <FIG>. Similarly, linear x-ray detector array <NUM> can be attached to linear x-ray detector array actuator <NUM> that also moves linearly, for example, into and out of the page of <FIG> and in a synchronized manner with the movement of x-ray tube <NUM> and aperture <NUM>. Alternatively, linear x-ray detector array actuator <NUM> can rotate linear x-ray detector array <NUM> to match the movement of x-ray tube actuator <NUM> that moves both x-ray tube <NUM> and aperture <NUM> in arc. In another alternative, linear x-ray detector array actuator <NUM> can move linear x-ray detector array <NUM> in an arc to match the rotation of x-ray tube actuator <NUM> that rotates both x-ray tube <NUM> and aperture <NUM>. By rotating one of x-ray tube <NUM> and linear x-ray detector array <NUM> and moving the other in an arc, the distance between the two can be maintained.

With reference to <FIG>, inspection during additive manufacturing can proceed as shown in <FIG>. A method <NUM> for real time inspection during additive manufacturing is similar to the method <NUM> shown in <FIG>. In this case, controller <NUM> can control the speed, as well as the start and stop of the motion of both x-ray tube actuator <NUM> and linear x-ray detector array actuator <NUM>. Controller <NUM> also synchronizes their movement to scan the entire volume of object being fabricated <NUM>. The speed of movement of one or both actuators can depend on the size of object being fabricated <NUM> and/or the x-ray pulse width and can range from about <NUM>/sec to about <NUM>/min.

Method <NUM> is described herein with respect to a metal powder fed additive manufacturing system <NUM> shown in <FIG>. One of ordinary skill in art will understand that reference to metal powder fed system <NUM> is for descriptive purposes and that the disclosed system and method can be used in other types of additive manufacturing systems and is not limited to additive manufacturing of metal objects.

At <NUM> of method <NUM> shown in <FIG>, deposition and fusing of material to form an object by additive manufacturing is paused, for example, by stopping deposition of metal powder and turning off the laser that provides laser beam <NUM> or redirecting laser beam <NUM> away from object <NUM>. Build chamber <NUM> does not need to be opened, the environment inside does not need to be changed, and object <NUM> does not need to be removed from the build chamber. This can minimize the amount of time the additive manufacturing process is paused.

At <NUM> of method <NUM>, x-ray tube actuator <NUM> and linear x-ray detector array actuator <NUM> can move x-ray tube <NUM> and linear x-ray detector array <NUM>, respectively, in a linear manner, for example, into and out of the page of <FIG>. Controller <NUM> synchronizes the linear motion so the object being fabricated <NUM> is scanned by x-ray pulse <NUM> and subsequently detected by linear x-ray detector array <NUM>. X-ray tube actuator <NUM> also moves aperture <NUM> in a synchronized manner with x-ray tube <NUM> and linear x-ray detector array <NUM>.

Alternatively, at <NUM> of method <NUM>, x-ray tube actuator <NUM> and linear x-ray detector array actuator <NUM> can rotate one of x-ray tube <NUM> and linear x-ray detector array <NUM>, and the other of x-ray tube actuator <NUM> and linear x-ray detector array actuator <NUM> can move in an arc. This can maintain the distance between x-ray tube <NUM> and linear x-ray detector array <NUM>. X-ray tube actuator <NUM> also moves aperture <NUM> in a synchronized manner with x-ray tube <NUM> and linear x-ray detector array <NUM>. Controller <NUM> synchronizes the motion of aperture <NUM>, x-ray tube <NUM>, and linear x-ray detector array <NUM> so the object being fabricated <NUM> is scanned by x-ray pulse <NUM> and subsequently detected by linear x-ray detector array <NUM>.

At <NUM> of method <NUM>, an x-ray pulse is directed towards object <NUM> at the same time as x-ray tube actuator <NUM> moves x-ray tube <NUM> and aperture <NUM>, and linear x-ray detector array actuator <NUM> moves linear x-ray detector array <NUM>. In this manner, object <NUM> is scanned by the x-ray pulse as one or both of the x-ray tube and linear x-ray detector array are moved linearly, in an arc or rotated. The x-ray pulse can occur at a time T<NUM>. Time T<NUM> is subsequent to a time T<NUM> and prior to a time TF, wherein time T<NUM> is a start of additive manufacturing of object <NUM> and time TF is a completion of additive manufacturing of object <NUM> within build chamber <NUM>. Referring to <FIG>, x-rays are generated by x-ray tube <NUM>. Linear aperture <NUM>, under the control of controller <NUM>, provides a collimated fan shaped x-ray pulse that interacts with object <NUM>. The x-ray pulse can have a pulse duration of about <NUM> second to about <NUM> seconds and an energy of about <NUM> to about <NUM> keV. Current can range from about <NUM> to about <NUM> mA. The x-ray pulse duration allows x-rays to interact with the object being formed as the x-ray tube and/or linear x-ray detector array is being moved linearly or in an arc. The collimated fan beam can further have a length, for example, long enough to inspect object <NUM> at its largest dimensions when fabrication is completed.

At <NUM> of method <NUM>, x-ray pulse <NUM> is detected by linear x-ray detector array <NUM>. The speed of actuators <NUM> and <NUM> moving object <NUM> and the pulse width of x-ray pulse <NUM> allow linear x-ray detector array <NUM> to detect the x-rays subsequent to interaction with an entire volume of object <NUM>. In other words, scanning of the entire volume of object <NUM> can be accomplished by controlling the pulse width and speed of actuators <NUM> and <NUM>. The data collected by linear x-ray detector array <NUM> is sent to computer <NUM>. At this point, controller <NUM> under the direction of computer <NUM> can stop motion of actuators <NUM> and <NUM>.

If a defect is not detected in object <NUM>, the additive manufacturing can resume fabrication of object <NUM>, as shown at <NUM> of method <NUM>. Referring to <FIG>, resuming additive manufacturing means that metal powder feeder <NUM> begins to deposit metal powder while laser beam <NUM> fuses the metal powder at the surface of object <NUM>. One of ordinary skill in the art will understand that fabrication can resume at any time after detection of the x-rays by linear x-ray detector array <NUM>. In other words, additive manufacturing can resume before completion of the analysis of whether a defect exists.

Claim 1:
A method (<NUM>) for detecting defects during additive manufacturing comprising:
pausing additive manufacturing of an object (<NUM>) within a build chamber (<NUM>, <NUM>) at a time T<NUM> , wherein T<NUM> is subsequent to a time T<NUM> and prior to a time TF, wherein time T<NUM> is a start of additive manufacturing of the object (<NUM>) being formed and time TF is a completion of additive manufacturing of the object (<NUM>) being formed in the build chamber (<NUM>, <NUM>);
moving linearly or rotating the object (<NUM>) in the build chamber (<NUM>, <NUM>) in a direction perpendicular to the length dimension of a linear x-ray detector (<NUM>, <NUM>) and a linear aperture (<NUM>, <NUM>), wherein the linear aperture (<NUM>, <NUM>) and the linear x-ray detector (<NUM>, <NUM>) are disposed outside of the build chamber (<NUM>, <NUM>);
directing an x-ray pulse from an x-ray tube (<NUM>) through the linear aperture (<NUM>, <NUM>) towards the object (<NUM>) being formed and rotated or moved inside of the build chamber (<NUM>, <NUM>) to scan the object (<NUM>) being formed;
detecting the x-ray pulse, by the linear x-ray detector array (<NUM>, <NUM>), subsequent to interaction of the x-ray pulse and the object (<NUM>) being formed and rotated; and
creating an x-ray image of the object (<NUM>) being formed based on the x-ray pulse that was detected,
wherein the rotation or movement of the object (<NUM>) is such that the entire volume of the object is scanned by the x-ray pulse.