Laser energy source failure detection in additive manufacturing systems and methods

Abstract

Methods for registering one or more laser energy pixels on a build surface to at least one laser energy source of the plurality of laser energy sources and / or determining an operating state of the at least one laser energy source are described. In some embodiments, a photosensitive detector may capture at least one image of the build surface with one or more laser energy pixels formed thereon. A reference frame of the photosensitive detector may be registered with a reference frame of the one or more laser energy pixels based at least in part on an identified location of the one or more laser energy pixels within the at least one image. This may include using a characteristic spatial frequency of the laser energy pixels within the at least one image. In some embodiments, at least one image including a weld pattern of a part being formed may be compared to an expected weld pattern to determine an operating state of the at least one laser energy source during operation.

Description

LASER ENERGY SOURCE FAILURE DETECTION IN ADDITIVE MANUFACTURING SYSTEMS AND METHODSRELATED APPLICATION

[0001] This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Application No. 63 / 470,611, filed June 2, 2023, the content of which is incorporated by reference in its entirety for all purposes.FIELD

[0002] Disclosed embodiments are generally related to methods and systems of calibrating and determining failures.BACKGROUND

[0003] Additive manufacturing systems employ various techniques to create three- dimensional objects from two-dimensional layers. After a layer of precursor material is deposited onto a build surface, a portion of the layer may be fused through exposure to one or more energy sources to create a desired two-dimensional geometry of solidified material within the layer. In some additive manufacturing systems, these energy sources may correspond to tens or hundreds of laser energy sources. After forming a current layer, the build surface may be indexed, and another layer of precursor material may be deposited. For example, in conventional systems, the build surface may be indexed by a distance corresponding to a thickness of a layer. This process may be repeated layer-by-layer to fuse multiple two-dimensional layers into a three-dimensional object.SUMMARY

[0004] In some embodiments, a method of monitoring a plurality of laser energy sources of an additive manufacturing system may include obtaining a weld pattern for one or more parts being formed by the additive manufacturing system, obtaining at least one image of a build surface as the one or more parts are formed by the additive manufacturing system, and comparing the at least one image to the weld pattern to determine an operating state, such as a failure state, of at least one laser energy source of the plurality of laser energy sources. The method may also include analyzing the at least one image to identify at least one location of the plurality of laser energy pixels in the at least one image.

[0005] In some embodiments, an additive manufacturing system may include a build surface, a plurality of laser energy sources configured to direct laser energy from the plurality of laser energy sources toward the build surface to form a plurality of laser energy pixels on the build surface, a photosensitive detector configured to image at least a portion of the build surface including the plurality of laser energy pixels when the plurality of laser energy pixels are formed thereon, and at least one processor. The at least one processor may be configured to perform the steps of obtaining a weld pattern for one or more parts being formed by the additive manufacturing system, obtain at least one image of the build surface as the one or more parts are formed by the additive manufacturing system using the photosensitive detector, and compare the at least one image to the weld pattern to determine an operating state of at least one laser energy source of the plurality of laser energy sources.

[0006] In some embodiments, a method of registering a photosensitive detector may include obtaining at least one image of a build surface with one or more laser energy pixels of a plurality of laser energy pixels formed thereon, analyzing the at least one image to identify at least one location of the one or more laser energy pixels in the at least one image, and registering a reference frame of the photosensitive detector with a reference frame of the one or more laser energy pixels based at least in part on the identified location of the one or more laser energy pixels in the at least one image. The method may also include determining an intensity of the one or more laser energy pixels based at least in part on the at least one identified location of the one or more laser energy pixels and intensity values of the at least one image and / or registering a plurality of laser energy sources with the plurality of laser energy pixels formed on the build surface.

[0007] In some embodiments, an additive manufacturing system may comprise a build surface, a plurality of laser energy sources configured to direct laser energy from the plurality of laser energy sources toward the build surface to form a plurality of laser energy pixels on the build surface, a photosensitive detector configured to image at least a portion of the build surface including the plurality of laser energy pixels when the plurality of laser energy pixels are formed thereon, and at least one processor. The processor may be configured to perform the steps of obtaining at least one image of the build surface with one or more laser energy pixels of the plurality of laser energy pixels formed thereon with the photosensitive detector, analyzing the at least one image to identify at least one location of the one or more laser energy pixels in the at least one image, and registering a reference frame of the photosensitive detector with a reference frame of the one or more laser energypixels based at least in part on the identified location of the one or more laser energy pixels in the at least one image.

[0008] In some embodiments, non-transitory computer readable memory may include processor executable instructions that when executed by one or more processors perform any one of the above disclosed methods.

[0009] It should be appreciated that the foregoing concepts, and additional concepts discussed below, may be arranged in any suitable combination, as the present disclosure is not limited in this respect. Further, other advantages and novel features of the present disclosure will become apparent from the following detailed description of various nonlimiting embodiments when considered in conjunction with the accompanying figures.

[0010] Other advantages and novel features of the present disclosure will become apparent from the following detailed description of various non-limiting embodiments of the disclosure when considered in conjunction with the accompanying figures.BRIEF DESCRIPTION OF DRAWINGS

[0011] The accompanying drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component that is illustrated in various figures may be represented by a like numeral. For purposes of clarity, not every component may be labeled in every drawing. In the drawings:

[0012] Fig. 1 shows a schematic representation of an additive manufacturing system according to one embodiment;

[0013] Fig. 2 shows the optical paths present in an additive manufacturing system according to one embodiment;

[0014] Fig. 3 shows an additive manufacturing system according to one embodiment;

[0015] Fig. 4 shows a schematic representation of an optical assembly and a build surface with laser energy pixels formed thereon, according to one embodiment;

[0016] Fig. 5 depicts a flowchart detailing a method of identifying locations and intensity values of one or more laser energy pixels projected by at least one laser energy sources onto a build surface, according to one embodiment;

[0017] Fig. 6 depicts a flowchart detailing a method of determining an operating state of at least one laser energy source, according to one embodiment;

[0018] Fig. 7A is a schematic depiction of imaging and processing of a weld pattern to generate a linear array of maximum intensity values, according to one embodiment;

[0019] Fig. 7B is a close-up of a section of the linear array of intensity values from Fig. 8A, according to one embodiment;

[0020] Fig. 8A is a graph of intensity data of an image of a build surface taken along a line passing through the laser energy pixels formed on the build surface, according to one embodiment;

[0021] Fig. 8B depicts a transformation of the intensity data of Fig. 8A into a spatial frequency domain, according to one embodiment;

[0022] Fig. 8C is a graph of a sinusoid plotted from characteristics identified from the spatial frequency domain graph of Fig. 8B, according to one embodiment;

[0023] Fig. 8D shows the sinusoid of Fig. 8C and the intensity data of Fig. 8A aligned on the same axis, according to one embodiment;

[0024] Fig. 8E shows registration of each peak of the sinusoid to the intensity data, according to one embodiment;

[0025] Fig. 8F shows the registered intensity values and pixel location of each peak of the sinusoid, according to one embodiment;

[0026] Fig. 8G shows a plot of the registered intensity of each operating laser energy source of the plurality of laser energy sources, according to one embodiment; and

[0027] Fig. 9 is a spot cloud of a plurality of laser energy pixels, according to one embodiment.

[0028] It should be understood that aspects of the disclosure are described herein with reference to the figures, which show illustrative embodiments. The illustrative embodiments described herein are not necessarily intended to show all aspects of the disclosure, but rather are used to describe a few illustrative embodiments. Thus, aspects of the disclosure are not intended to be construed narrowly in view of the illustrative embodiments. In addition, it should be understood that aspects of the disclosure may be used alone or in any suitable combination with other aspects of the invention.DETAILED DESCRIPTION

[0029] With the advancement of additive manufacturing systems, increased demands have been placed on every part of the system. Additive manufacturing systems have gotten faster, larger, and more intricate. For example, additive manufacturing systems exhibit increasingly complex optical modules which may include up to hundreds and potentially thousands of individual laser energy sources. The use of these increasing numbers of laserenergy sources have enabled systems to produce parts at an increased rate, on larger build areas, as well as with increased intricacy. However, the increased complexity and scale of additive manufacturing systems have also increased the probability of failures and the costs associated such failures. For example, as the number of laser energy sources in a system has increased, the probability that one or more of the laser energy sources will fail in a given time period has also increased.

[0030] Current methods to detect operating states of laser energy sources, including failure states, are limited to per-channel solutions, e.g., coupling a sensor to each laser energy source to individually detect the state of each laser energy source. Per-channel solutions are both expensive as well as difficult to implement and / or maintain as the number of laser energy sources increases, e.g., in systems with more than ten laser energy sources. Spatial requirements associated with per-channel solutions may also be prohibitive with an increased number of laser energy sources. Another common method of monitoring laser failures may be to monitor the amount of power consumed by the plurality of laser energy sources versus the amount of power delivered by the laser energy sources, but this method is not capable of detecting the state of individual laser energy sources and only offers a broad overview of the system. Other methods of detecting laser failure are very dependent on operator skill and / or input. For example, it may be complex and difficult for an operator to reliably identify failure states on a large scale, especially when these failure states may be transient and / or partial failures. For instance, partial failures may include a flickering laser energy source, which may require constant surveillance from an operator to catch. Other partial failures, such as a laser energy source with decreased intensity, may also be difficult for an operator to distinguish from normal operation. Furthermore, with hundreds of laser energy sources, and thus hundreds of laser energy pixels and / or laser fields present projected onto the build surface, correctly registering laser energy pixels to specific corresponding laser energy sources in addition to distinguishing the operating states of those laser energy sources may be impossible with only operator oversight. This may result in delays and / or inability of an operator to take appropriate corrective actions in instances in which a laser energy source failure occurs. As such, the Inventors have recognized that it may be desirable to provide methods and systems to monitor and reliably detect operating states of laser energy sources of an additive manufacturing system.

[0031] In view of the above, the Inventors have recognized that it may be desirable to monitor the laser energy pixels of an additive manufacturing system using one or morephotosensitive detectors. Specifically, one or more photosensitive detectors may be used to image at least a portion of, or in some embodiments an entire build surface including a plurality of laser energy pixels formed thereon during operation of the system. These images may then be used to monitor the state of the plurality of laser energy pixels of the additive manufacturing system as elaborated on further below. However, in some embodiments, variations in height between the photosensitive detector and the build surface may occur during movement of an optical assembly, gantry, or other type of movement system associated with the photosensitive detector in addition to variations in the height of the build surface itself due to variations in powder distribution. These variations in distance to the build surface may result in corresponding variations in the relative positioning and size of the laser energy pixels within the captured images which may complicate the identification and analysis of laser energy pixels using such images.

[0032] In view of the above, the Inventors have recognized a need for methods and systems for accurately and reliably analyzing the one or more images of a build surface to monitor the operating states of the laser energy pixels of an additive manufacturing system. Thus, in some embodiments, it may be desirable to register a reference frame of the one or more photosensitive detectors of a system with a reference frame of a build surface with one or more laser energy pixels formed thereon. For example, this may include registering laser energy pixels imaged on a build surface by one or more photosensitive detectors of a system with their corresponding laser energy sources which may be contained in an array of laser energy sources. More specifically, in some embodiments, registration may include analyzing at least one image of the build surface to identify a location of at least one, and in some instances multiple, laser energy pixels of the plurality of laser energy pixels within the at least one image. This analysis of the image to identify the laser energy pixels may be performed in any appropriate manner with a specific method elaborated on further below. Once the laser energy pixels have been identified within the at least one image, a reference frame of the photosensitive detector may be registered with a reference frame of the laser energy pixels and / or build surface based at least in part on the identified locations of the one or more laser energy pixels in the at least one image. Once the at least one photosensitive detector has been appropriately registered to a reference frame of the system, information related to the separate laser energy pixels may be associated with separate groups of pixels of the at least one photosensitive detector to permit parameters associated with the separate laser energy pixels to be independently monitored using the at least one photosensitive detector. Again this maybe contrasted with the use of individual sensors associated with each laser energy pixel used in typical additive manufacturing systems.

[0033] As noted above, photosensitive detectors may capture images of the build surface with different variable heights between the photosensitive detector and the build surface due to variable positioning of the photosensitive detector and / or variations in powder layer height. In some embodiments, a robust method for identifying locations of the one or more laser energy pixels in the reference frame of the at least one image irrespective of variations in the distance between the photosensitive detector and the build surface may include analyzing a captured image by converting the captured image to a spatial frequency domain. The converted image in the spatial frequency domain may include information representative of periodic characteristics of detected features within the original image. For example, in an additive manufacturing system, the plurality of laser energy sources may be organized in an array in the optics assembly such that a plurality of laser energy pixels are projected onto the build surface in a periodically arranged array which may exhibit uniform periodic spacings in one or more directions between adjacent laser energy pixels. This may include periodic spacings in one direction for a one dimensional array and periodic spacings in two or more directions for a two dimensional array (e.g., rectangular and non-rectangular arrays). The plurality of laser energy pixels may correspondingly form surface features on the build surface with similar periodic spacings (e.g., melt pools formed on the build surface in a similar uniform and / or periodic array on the build surface). As such, a characteristic spatial frequency may be associated with the periodic spacing of the laser energy pixels and / or melt pools on the build surface in the one or more characteristic directions of the array of laser energy pixels.

[0034] This above noted characteristic spatial frequency may be determined based at least in part on the converted image in the spatial frequency domain. For instance, in some embodiments, a peak frequency may be identified as the characteristic spatial frequency corresponding to the spatial frequency of the pixels. Alternatively or additionally, at least one spatial frequency threshold based on the properties of the additive manufacturing system may be used to aid in identifying the characteristic spatial frequency. The one or more spatial frequency thresholds may be based on the arrangement of the plurality of laser energy sources in the optics assembly, and may represent an expected maximum spatial frequency, and / or a range of spatial frequencies, of repetition for the laser energy pixels and / or melt pools on the build surface for the expected variations in distance between the photosensitivedetector and the build surface. For example, features with a spatial frequency greater than a first threshold may be identified as corresponding to the laser energy pixels and features with spatial frequencies less than the first threshold may be excluded. Similarly, in some optional embodiments, features with a spatial frequency less than a second threshold may be identified as corresponding to the laser energy pixels and features with spatial frequencies greater than the second threshold may be excluded. Again, this range between the two thresholds may be selected to correspond to an expected range of variation of the laser energy pixels within the images for the expected variations in distance between the photosensitive detector and the build surface. In either case, the spatial frequency identified using the above method may correspond to the spacing of the laser energy pixels within the original image. Additionally, the above noted thresholds may be used in combination with identifying a peak frequency. In either case, once identified, the characteristic spatial frequency may then be used to register the reference frame of the photosensitive detector to the reference frame of the laser energy pixels and build surface as elaborated on further below.

[0035] It should be understood that the captured images may be converted to the spatial frequency domain using any appropriate type of transform. This may include, for example, the use of a Fourier transformation in some embodiments. Possible methods of Fourier transforms include Fourier series, Fourier integrals, Discrete Fourier Transforms, and Fast Fourier Transformations (FFT). In some embodiments, it may be desirable to use Fast Fourier Transformations as FFT may provide reduced computing costs and increased speed as compared to other methods of Fourier transforms. Of course it should be understood that other types of transformations may be used as the disclosure is not so limited.

[0036] As noted above, once appropriately registered to a reference frame of an array of laser energy pixels and / or build surface using either the currently disclosed registration methods or other appropriate registration methods, one or more photosensitive detectors of an additive manufacturing system may be used to monitor one or more parameters associated with the laser energy pixels and the associated laser energy sources. This may include determining an operating state of the one or more laser energy pixels of an additive manufacturing system based at least in part on the images of the build surface during an additive manufacturing process. For example, in some embodiments, at least one captured image including the laser energy pixels, corresponding melt pools, and / or weld patterns may be compared to an expected weld pattern and / or locations of a plurality of laser energy pixels on the build surface to determine an operating state of at least one laser energy source of theplurality of laser energy sources. This may include determining an expected weld pattern for one or more parts being formed by the additive manufacturing system using a build plan for the parts. For example, the build plan may include information including but not limited to locations of the plurality of laser energy pixels on the build surface during the build process, trajectories of the laser energy pixels across the build surface, a list of the operating parameters for the laser energy pixels, expected intensity values of laser energy pixels projected onto the build surface, the expected radiation emissions and / or reflections of welds and / or melt pools (expected weld signature), and other appropriate parameters. These commanded parameters for each laser energy pixel may then be compared to the corresponding parameters in the image for the corresponding laser energy pixel of the plurality of laser energy pixels to identify an operating state of each laser energy pixel that is currently being operated.

[0037] In some embodiments, a comparison between an expected weld pattern and an observed weld pattern may be performed during a build process as a method of monitoring the operating states of the laser energy sources in real time. Through a series of steps disclosed below, the observed weld pattern may be registered to a reference frame of the plurality of laser energy sources and laser energy pixels such that any portion of the observed weld pattern can be matched to at least one corresponding laser energy source and laser energy pixel. The resulting weld pattern and / or locations of the laser energy pixels captured by the photosensitive detector in any portion of a build process are expected to coincide with the expected weld pattern and / or expected locations of the plurality of the laser energy pixels in the same portion of the build process, which may be used to register the laser energy pixels in its own reference frame to the laser energy pixels in the reference frame of the at least one captured image. As such, a comparison between the observed weld pattern to the expected weld pattern may be desirable as it may offer direct information on the operating states of the laser energy sources. For example, if a portion of the expected weld pattern is completely absent in the observed weld pattern, the comparison may reveal that the laser energy source associated with that portion of the expected weld pattern is failing to produce any light. Similarly, a comparison between the expected and observed weld patterns may allow identification of misfiring laser energy sources, e.g., firing at an incorrect location or firing during an off period. In some embodiments, a weld pattern may further comprise information regarding the expected size of the melt pools present at the location of the laser energy pixels. For example, the center of each melt pool may represent the location where a laser energysource was directed onto the build surface as a laser energy pixel. The dimensions of a melt pool may be an indicator of the amount of energy absorbed from a laser energy source. Thus, a difference in the observed dimensions of a melt pool may also indicate a failure state in an associated laser energy source, as a difference in dimensions may be attributed to a difference in projected laser intensity.

[0038] It should be understood that any appropriate parameter or set of parameters may be used to monitor the operating states of the one or more laser energy sources of an additive manufacturing system. Appropriate parameters may include but are not limited to intensity of the laser energy pixels, shape of the laser energy pixels, size of the laser energy pixels, pattern of the laser energy pixels, locations of the laser energy pixels, and any other applicable parameter. The one or more parameters may be used at least in part to determine an operating state of the laser energy sources, including full functionality, full failure, and partial failure. In some embodiments, a full failure may include a broken laser energy source and / or the laser energy pixel of a corresponding laser energy source existing in an unexpected location. Laser energy source operating states may also include partial failures where a laser energy source still maintains partial functionality, but fails to operate within a desired operational window. For example, partial failures may include unexpected intermittent operation during a build process, as the laser energy source turns on and off unexpectedly. Alternatively, a laser energy source may also exhibit partial failures corresponding to decreased delivery of laser power to a desired location without completely failing. Partial failures may also include identifying laser energy pixels that are directed onto the build surface at incorrect locations. These partial failures may lead to failures including but not limited to: partially-fused powder layers in completed parts, as the laser energy source may not have provided enough energy to melt and fuse the entire layer in a desired build area; out of tolerance parts, and / or other types of part defects.

[0039] It should be understood that the above noted failures may be associated with failures of the laser energy source itself. However, in some instances, these failures may be associated with other components of the additive manufacturing system in addition to the plurality of laser energy sources. For example, if a laser energy pixel directed onto the build surface by a functional laser energy source is absent and / or misaligned, the absence and / or misalignment may reveal other parts of optics assembly to be malfunctioning, e.g., a faulty connector between the laser energy source and a corresponding optical fiber, misalignment of the mirrors and / or lenses associated with the laser energy source, misalignment of thephotosensitive detector, the presence of contaminants on the optics assembly partly scattering or absorbing the laser energy, and / or any other applicable situation. In some cases, an absence and / or misalignment of a laser energy pixel may also be caused by malfunctions within the broader additive manufacturing system, such as misaligned gantry systems, insufficient powder on the build surface, and any other applicable malfunctions. Thus, it should be understood that the disclosed failure states of a laser energy source, and the associated laser energy pixel, may correspond to any number of different types of failures that result in the laser energy pixels projected onto a surface being outside of a desired set or operational ranges.

[0040] In some embodiments, the laser energy sources may be continuously monitored throughout a build process, e.g., during and / or after the formation of each build layer due to the plurality of laser energy sources being operated to fuse one or more portions of the build surface. During operation, one or more photosensitive detectors may capture at least one image of the build surface with the laser energy pixels formed thereon during the build process by imaging the build surface. In some embodiments, the one or more photosensitive detectors may capture multiple images of the build surface during a formation process. For example, the one or more photosensitive detectors may capture a video of the build surface in the form of a stream of images as the laser energy pixels are scanned across the build surface. The frequency and / or number of images captured may depend on a desired rate of monitoring of the build surface.

[0041] As noted previously, the Inventors have recognized numerous advantages associated with the ability to continuously monitor the operating state of the laser energy sources. For example, additive manufacturing systems including larger numbers of laser energy sources may be more prone to failure of one or more laser energy sources, and thus, may benefit from continuous monitoring of the laser energy sources to determine any laser energy source failures (e.g., full or partial failures) such that a build process may be appropriately modified and / or repairs may be promptly made to maintain process efficiency. This may include controlling operation of the laser energy sources, the associated optics assembly, and / or any other appropriate portion or process of the additive manufacturing system based at least in part on the identified operating states of the laser energy sources. For example, more complicated build processes, where the produced part is more easily affected by laser energy source failures, may also benefit from continuous monitoring of the laser energy sources to prevent laser failures from affecting the quality of the produced part.However, in some embodiments, the plurality of laser energy sources may be intermittently monitored throughout a build process, e.g., the photosensitive detector may perform intermittent monitoring of the laser energy sources where one or more images of the build surface may be captured at predetermined intervals. The rate of monitoring associated with intermittent monitoring may either be constant or random, e.g., images of the build surface may be captured at different intervals. In either case, it should be understood that the current systems and methods are not limited to only continuous monitoring.

[0042] The currently disclosed systems and methods offer multiple potential benefits for additive manufacturing systems. Specifically, as noted above as the number of laser energy sources increases, the chance of any laser energy source failing in a given time period also increases. In some embodiments, if a given laser energy source fails during a build process, receiving notification and / or information about the failure state may be advantageous to determining a subsequent action. In some situations, a laser failure may lead to increased part defects, and as such, efficiency of the additive manufacturing system may be improved if the build process was modified and / or stopped to either remedy / prevent defects or in instances where a print cannot be remedied to prevent the waste of additional time and resources. Furthermore, receiving information about any failing and / or malfunctioning laser energy sources may be advantageous in order to identify laser energy sources for subsequent repair. Additionally, many failures are difficult for an operator to observe and categorize properly during a build process, and thus automating such monitoring may improve the timely and accurate identification of such failures without relying on operator skill. Thus, the disclosed systems and methods may offer both accurate and timely monitoring of the operating states of the plurality of laser energy sources with little to no operator skill requirements which may increase efficiency of the system and quality of the produced parts. However, instances in which other benefits are provided that are different from those noted above are also contemplated.

[0043] It should be understood that any appropriate type and / or number of photosensitive detectors may be used to implement the systems and methods disclosed herein. However, in some embodiments, the photosensitive detectors disclosed herein may be a line scan camera. In other embodiments, a camera including a two dimensional array of pixels may be used. In either case, a photosensitive detector (e.g., a photosensitive sensor) may be configured to image at least a portion of the build surface, where the portion of the build surface includes a location of at least one, and in some instances all of the laser energypixels of a system on the build surface if the laser energy pixels were in an active state. The photosensitive detector may have a sufficient resolution capable of distinguishing the at least one laser energy pixel directed onto the build surface, e.g., a resolution (i.e., pixel field of view size) equal to or less than a minimum transverse dimension (e.g., a width, diameter, or similar dimension) of the plurality of laser energy pixels on the build surface. Thus, it should be understood that any type of photosensitive detector or multiple photosensitive detectors capable of imaging or otherwise detecting the light within one or more wavelength ranges associated with the processes disclosed herein may be used as the disclosure is not limited to any particular type of camera, imaging device, or other type of photosensitive detector.

[0044] In some embodiments, the photosensitive detector may be mounted vertically above the build surface, e.g., mounted on a gantry system and / or an optics assembly of the additive manufacturing system. The photosensitive detector may remain stationary, or if the photosensitive detector is mounted to a gantry system and / or optics assembly, the photosensitive detector may travel in a direction parallel to the build surface with the gantry and / or optics assembly such that the photosensitive detector may be scanned across the build surface such that a stream of images corresponding to the different portions of the build surface may be captures. In such an embodiment, the photosensitive detector may be configured to move in sync with the optics assembly.

[0045] In some embodiments, when a photosensitive detector captures at least one image of the build surface, the photosensitive detector may be configured to capture the light emitted from features on the build surface, e.g., melt pools, during a build process of the additive manufacturing system. For example, in some embodiments, wavelengths of light of interest emitted during a build process of an additive manufacturing system may range from about 400 nanometers (nm) to about 1500 nm. In further embodiments, the wavelengths of light of interest may range from about 780 nm to about 1.0 millimeter (mm). These ranges may include wavelengths of light emitted from plasma, wavelengths of light within the Nearinfrared (NIR) range (e.g., 800 nm to 1,200 nm), wavelengths associated with laser energy, wavelengths of light within the visible spectrum (e.g., 380 nm to 700 nm), wavelengths of light within the infrared (IR) range (e.g., 700 nm to 800 nm), and / or any other appropriate range. In some embodiments, capturing images of the build surface in the NIR range may provide greater contrast of the weld pools and associated welds than capturing an image of the build surface in the visible spectrum. Furthermore, NIR detection may be effective at identifying temperature gradient present in the melt pools formed by the plurality of laserenergy sources. In some embodiments, a photosensitive detector may be capable of detecting and capturing multiple spectrums of light. Alternatively, separate photosensitive detectors configured to image different wavelength ranges may be used. In some embodiments, the photosensitive detector may be a commercially available weld monitoring camera.

[0046] In some embodiments, a photosensitive detector may also capture a weld signature of a build process. A weld signature may comprise light in a wavelength range associated with at least one selected from a group of weld radiation emissions, weld radiation reflections, melt pool radiation emissions, and melt pool radiation reflection. The radiation of the weld signature captured by the photosensitive detector may include light spectrums as previously discussed, including but not limited to wavelengths of light emitted from plasma, wavelengths of light within the Near-infrared (NIR) range (e.g., 800 nm to 1,200 nm), wavelengths associated with laser energy, wavelengths of light within the visible spectrum (e.g., 380 nm to 700 nm), wavelengths of light within the infrared (IR) range (e.g., 700 nm to 800 nm), and / or any other appropriate range. For example, a melt pool may emit radiation, which may be caused by phase changes of a solid material to liquid on the build surface, heat radiating from the melt pool, plasma, and / or any other applicable factors. A melt pool may also reflect radiation, due to colors and / or reflective properties of the powder material on the build surface in a liquid, solid, and / or plasma state. For example, a melt pool may comprise a top layer of melted powder material in a liquid state, where the liquid top layer comprises a smooth surface geometry that may determine at least in part an amount of radiation reflected from sources including but not limited to laser energy sources, environmental conditions, and neighboring melt pools. In some embodiments, at least one external radiation source, e.g. an external radiation source array, may also emit radiation onto the build surface, which may be reflected by melt pools and / or welds on the build surface. The signals detected by a photosensitive detector associated with the above noted ranges may thus be associated with one or more parameters of the weld pool and / or weld and thus can be considered to be indicative of the “weld signature” and may be used to determine a quality or other appropriate parameter associated with the welds as elaborated on below.

[0047] In some embodiments, melt pool radiation reflections from the at least one external radiation source, laser energy sources, and / or environmental conditions may be used to determine at least in part information about the build process and / or the additive manufacturing system. As previously described, a melt pool may comprise a top liquid layer of powder material which may reflect radiation differently from a solid and / or plasma-statepowder material. In some embodiments, a liquid top layer of a melt pool may reflect more light than a solid top layer of a melt pool, and such differences may be captured by a photosensitive detector as a weld signature. In some embodiments, a captured weld signature may be compared to an expected weld signature to determine at least in part build quality, failure states, and / or any other applicable situations. Types and intensities of radiation captured in the weld signature may be compared to expected types and intensities of radiation from an expected weld signature. For example, if a type of radiation and / or expected intensity of radiation is not present in a captured weld signature but is present in an expected weld signature, such a difference may indicate that a weld and / or melt pool is performing unexpectedly. In some situations, a melt pool may not reflect and / or emit expected types and / or intensities of radiation due to an insufficient depth and / or insufficiently thick liquid top layer. Such a difference in the liquid top layer properties may represent a failure state present in the additive manufacturing system, e.g. the laser energy sources may not be achieving the necessary power to generate a liquid top layer of appropriate dimensions in the melt pool and / or improper distribution of powder material on the build surface. Additionally, in some embodiments, ideal melt pools may absorb more laser energy from the laser energy sources due to the topology of the molten powder material. Thus, the above noted signatures may be used as parameters for comparison during the methods disclosed herein to aid in determining an operating state of an additive manufacturing system.

[0048] As used herein, the term build plan and other similar terms may refer to the planned paths, e.g. trajectories, traced by the energy sources in the additive manufacturing process, including the thickness of each build layer, to form the plurality of build layers of one or more parts on a build plate. Build plans may additionally include other information such as a list of functional laser energy sources, the intensities at which the energy sources may operate at different locations along the build surface in each layer, the velocity of the optics assembly and laser energy pixels relative to a build surfaces, locations of laser energy pixel on the build surface during a build process, and other appropriate processing parameters. The paths traced by the one or more laser energy sources and / or laser energy pixels, referenced as trajectories, may be determined prior to the start of the manufacturing process and / or may be generated or updated in real time in instances where real time planning is implemented for an additive manufacturing process. In some embodiments, processing parameters may be associated with individual layers of the build plan, such as energy source intensity, and may be adjusted during a build process. For example, a build plan may includeper-layer build information which may be used to monitor the status of a part. Per-layer build information may include an expected build pattern during and / or after each layer is printed, expected dimensions of the part after each layer is printed, and any other applicable build information. Furthermore, a build plan may include specific energy source power settings, weld or formation speed, recoating rates, expected laser energy pixel shapes and / or sizes, expected weld pool shapes and / or sizes, and / or other process related information. The various processing parameters, including power settings and weld or formation speed, may be actively changed during a build based on the measured information associated with the different laser energy pixels. In some embodiments, processing parameters, such as the expected locations of the plurality of laser energy pixels, may be obtained independently from a weld pattern and / or build plan. Additionally, some processing parameters, such as the commanded locations of the laser energy pixels on the build surface, may be calculated from other information present in the build plan, including laser energy source trajectories, operation timing, timing, and any other applicable information.

[0049] As used herein, registering to the reference frame of a laser energy source and / or laser energy pixel may be used interchangeably. For example, registering the reference frame of a laser energy pixel and / or laser energy source with a reference frame of a photosensitive detector may refer to associating the laser energy source used to form the corresponding laser energy pixel on the build surface with a corresponding group of one or more pixels of a photosensitive detector. Similarly, determining and / or identifying an operating state, such as a failure state, of a laser energy source and / or a laser energy pixel may be used interchangeably.

[0050] In view of the above, the Inventors have recognized the opportunities associated with the rise in use and capabilities of controllable manufacturing systems, such as additive manufacturing and / or any other desired manufacturing processes associated with the usage laser energy sources. Specifically, the Inventors have recognized that accurate monitoring and determination of operating states of a plurality of laser energy sources may enable large scale manufacturing processes to operate more effectively and / or efficiently. For example, other manufacturing processes in which the current systems and methods may be implemented, and which may realize benefits from large scale monitoring of laser energy sources, may include laser thermal processing, laser cutting, laser thermal annealing, laser scanning, and / or any other desired laser manufacturing processes and / or systems.

[0051] In some embodiments, incident laser spots on a build surface may be arranged in a line with a long dimension and a short dimension, or in an array. In either case, according to some aspects, a line, or array, of incident laser energy consists of multiple individual laser energy pixels arranged adjacent to each other that can have their respective power levels individually controlled. Each laser energy pixel may be turned on or turned off independently and the power of each pixel can be independently controlled. The resulting pixel-based line or array may then be scanned across a build surface to form a desired pattern thereon by controlling the individual pixels during translation of the optics assembly.

[0052] Depending on the particular embodiment, an additive manufacturing system according to the current disclosure may include any suitable number of laser energy sources. For example, in some embodiments, the number of laser energy sources may be at least 5, at least 10, at least 50, at least 100, at least 500, at least 1,000, at least 1,500, or more. In some embodiments, the number of laser energy sources may be less than 2,000, less than 1,500, less than 1,000, less than 500, less than 100, less than 50, or less than 10. Additionally, combinations of the above-noted ranges may be suitable. Ranges both greater and less than those noted above are also contemplated as the disclosure is not so limited.

[0053] Additionally, in some embodiments, a power output of a laser energy source (e.g., a laser energy source of a plurality of laser energy sources) may be between about 50 W and about 2,000 W (2 kW). For example, the power output for each laser energy source may be between about 100 W and about 1.5 kW, and / or between about 500 W and about 1 kW. Moreover, a total power output of the plurality of laser energy sources may be between about 500 W (0.5 kW) and about 4,000 kW. For example, the total power output may be between about 1 kW and about 2,000 kW, and / or between about 100 kW and about 1,000 kW.Ranges both greater and less than those noted above are also contemplated as the disclosure is not so limited.

[0054] Depending on the embodiment, an array of laser energy pixels (e.g., a line array or a two dimensional array) may have a uniform power density along one or more axes of the array including, for example, along the length dimension (i.e. the longer dimension) of a line array. In other instances, an array can have a non-uniform power density along either of the axes of the array by setting different power output levels for each pixel’s associated laser energy source. Moreover, individual pixels on the exterior portions of the array can be selectively turned off or on to produce an array with a shorter length and / or width. In some embodiments, the power levels of the various pixels in an array of laser energy may beindependently controlled throughout an additive manufacturing process. For example, the various pixels may be selectively turned off, on, or operated at an intermediate power level to provide a desired power density within different portions of the array.

[0055] Generally, laser energy produced by a laser energy source has a power area density. In some embodiments, the power area density of the laser energy transmitted through an optical fiber is greater than or equal to 0.1 W / micrometer2, greater than or equal to 0.2 W / micrometer2, greater than or equal to 0.5 W / micrometer2, greater than or equal to 1 W / micrometer2, greater than or equal to 1.5 W / micrometer2, greater than or equal to 2 W / micrometer2, or greater. In some embodiments, the power area density of the laser energy transmitted through the optical fiber is less than or equal to 3 W / micrometer2, less than or equal to 2 W / micrometer2, less than or equal to 1.5 W / micrometer2, less than or equal to 1 W / micrometer2, less than or equal to 0.5 W / micrometer2, less than or equal to 0.2 W / micrometer2, or less. Combinations of these ranges are possible. For example, in some embodiments, the power area density of the laser energy transmitted through the optical fiber is greater than or equal to 0.1 W / micrometer2and less than or equal to 3 W / micrometer2.

[0056] Depending on the application, output of the optics assembly may be scanned across a build surface of an additive manufacturing system in any appropriate fashion. For example, in one embodiment, one or more galvo scanners may be associated with one or more laser energy sources to scan the resulting one or more laser pixels across the build surface. Alternatively, in other embodiments, an optics assembly may include an optics head that is associated with one or more appropriate actuators configured to translate the optics head in a direction parallel to a plane of the build surface to scan the one or more laser pixels across the build surface. In either case, it should be understood that the disclosed systems and methods are not limited to any particular construction for scanning the laser energy across a build surface of the additive manufacturing system.

[0057] For the sake of clarity, transmission of laser energy through an optical fiber is described generically throughout. However, with respect to various parameters such as transverse cross-sectional area, transverse dimension, transmission area, power area density, and / or any other appropriate parameters related to a portion of an optical fiber that the laser energy is transmitted through, it should be understood that these parameters refer to either a parameter related to a bare optical fiber and / or a portion of an optical fiber that the laser energy is actively transmitted through such as an optical fiber core, or a secondary optical laser energy transmitting cladding surrounding the core. In contrast, any surroundingcladding, coatings, or other materials that do not actively transmit the laser energy may not be included in the disclosed ranges.

[0058] As used herein, the term “obtaining” may be taken to mean at least one of the following: downloading, determining locally on a processor, determining on a remotely- accessed server and / or processor, importing, capturing from a sensor, and any other applicable methods of obtaining. The action of “obtaining” may be applied to information, physical objects, data, and any other applicable concepts.

[0059] For the sake of clarity, the embodiments described below are primarily described using an additive manufacturing process. However, it should be understood that any of the embodiments disclosed herein may be used with any appropriate additive and / or subtractive manufacturing process in which a plurality of laser energy sources may be used as the disclosure is not so limited. Therefore, any reference to the use of an additive manufacturing system herein should be understood to refer to corresponding processes being implemented for use with a subtractive manufacturing system as well.

[0060] It will be appreciated that any embodiments of the systems, components, methods, and / or programs disclosed herein, or any portion(s) thereof, may be used to form any part suitable for production using additive manufacturing. For example, a method for additively manufacturing one or more parts may, in addition to any other method steps disclosed herein, include the steps of selectively fusing one or more portions of a plurality of layers of precursor material deposited onto the build surface to form the one or more parts. This may be performed in a sequential manner where each layer of precursor material is deposited on the build surface and selected portions of the upper most layer of precursor material is fused to form the individual layers of the one or more parts. This process may be continued until the one or more parts are fully formed.

[0061] It will be appreciated that any embodiments of the systems, components, methods, and / or programs disclosed herein, or any portion(s) thereof, may be used to form any part suitable for production using additive manufacturing. For example, a method for additively manufacturing one or more parts may, in addition to any other method steps disclosed herein, include the steps of selectively fusing one or more portions of a plurality of layers of precursor material deposited onto the build surface to form the one or more parts. This may be performed in a sequential manner where each layer of precursor material is deposited on the build surface and selected portions of the upper most layer of precursormaterial is fused to form the individual layers of the one or more parts. This process may be continued until the one or more parts are fully formed.

[0062] Turning to the figures, specific non-limiting embodiments are described in further detail. It should be understood that the various systems, components, features, and methods described relative to these embodiments may be used either individually and / or in any desired combination as the disclosure is not limited to only the specific embodiments described herein.

[0063] FIG. 1 shows, according to some embodiments, a schematic representation of an additive manufacturing system 100, including a plurality of laser energy sources 102 that deliver laser energy to an optics assembly 104 positioned within a machine enclosure 106. For example, the machine enclosure may define a build volume in which an additive manufacturing process may be carried out. In particular, the optics assembly may direct laser energy 108 towards a build surface 110 positioned within the machine enclosure to selectively fuse powdered material on the build surface. As described in more detail below, the optics assembly 104 may include a plurality of optics defining an optical path within the optics assembly that may transform, shape, and / or direct laser energy within the optics assembly such that the laser energy is directed onto the build surface as an array of laser energy pixels. In some embodiments, the optics assembly may be movable within machine enclosure 106 to scan laser energy 108 across build surface 110 during a manufacturing process. For example, the optics assembly may be associated with appropriate actuators, rails, motors, and / or any other appropriate structure capable of optics assembly relative to the surface. Alternatively, embodiments in which the optics assembly includes galvomirrors or other appropriate components that are configured to scan the laser energy 108 across the build surface while the optics assembly is held stationary relative to the build surface are also contemplated.

[0064] In some embodiments, the additive manufacturing system 100 further includes one or more optical fiber connectors 112 positioned between the laser energy sources 102 and the optics assembly 104. As illustrated, a first plurality of optical fibers 114 may extend between the plurality of laser energy sources 102 and the optical fiber connector 112. In particular, each laser energy source 102 may be coupled to the optical fiber connector 112 via a respective optical fiber 116 of the first plurality of optical fibers 114. Similarly, a second plurality of optical fibers 118 extends between the optical fiber connector 112 and the optics assembly 104. Each optical fiber 116 of the first plurality of optical fibers 114 is coupled to acorresponding optical fiber 120 of the second plurality of optical fibers 118 within the optical fiber connector. In this manner, laser energy from each of the laser energy sources 102 is delivered to the optics assembly 104 such that laser energy 108 can be directed onto the build surface 110 during an additive manufacturing process (i.e., a build process). Of course other methods of connecting the laser energy sources 102 due to the optics assembly 104 are also contemplated.

[0065] In some embodiments, the additive manufacturing system 100 further comprises a photosensitive detector 140. The photosensitive detector 140 may be mounted vertically above the build surface 110 such that the detector may capture at least a portion of the build surface. In some embodiments, the photosensitive detector 140 may be at least partially contained within or mounted on the optics assembly 104. However, in other configurations, the photosensitive detector 140 may be separately mounted to a separate gantry system, other movement stage, or any other appropriate part of the additive manufacturing system that permits the camera to either directly or indirectly image either a portion of, or the entire, build surface.

[0066] Fig. 2 shows a schematic representation of another embodiment of an additive manufacturing system 200. Similar to the embodiment discussed above in connection with Fig. 1, the additive manufacturing system 200 includes a plurality of laser energy sources 202 coupled to the optics assembly 204 within the machine enclosure 206 via the optical fiber connector 212. The first plurality of optical fibers 214 extends between the laser energy sources 202 and the optical fiber connector 212, and the second plurality of optical fibers 218 extends between the optical fiber connector 212 and optics assembly 204. In particular, each optical fiber 216 of the first plurality of optical fibers is coupled to a laser energy source 202 and corresponding optical fiber 220 of the second plurality of optical fibers 218. In the depicted embodiment, optical fibers 216 are coupled to corresponding optical fibers 220 via fusion splices 222 within the optical fiber connector 212. However, embodiments, in which the optical fibers positioned within the connector are optically coupled using other types of connections and / or single continuous optical fibers are used are also envisioned.

[0067] In the depicted embodiment, the optical fibers 220 of the second plurality of optical fibers 218 are optically coupled to an optics assembly 204 of the system. For example, an alignment fixture 224 is configured to define a desired spatial distribution of the optical fibers used to direct laser energy into the optics assembly. For example, the alignment fixture may comprise a block having a plurality of v-grooves or holes in which theoptical fibers may be positioned and coupled to in order to accurately position the optical fibers within the system.

[0068] Fig. 2 also depicts exemplary optics that are optically coupled to and positioned downstream from the second plurality of optical fibers 218. The various optics included in the optics assembly may be configured to direct laser energy 208 from the second plurality of optical fibers 218 on the build surface 210 to form a desired array pattern of laser energy pixels on the build surface. For example, the optics assembly may include beam forming optics such as lenses 226 and 228 (which may be individual lenses, lens arrays, and / or combined microlenses), mirrors 230, and / or any other appropriate type of optics disposed along the various optical paths between the optical fibers and the build surface 210 which may shape and direct the laser energy within the optics assembly. Once appropriately sized and shaped, the laser energy 208 may be directed onto the build surface 210 either through direct transmission and / or using a light directing element such as the depicted mirror 230.

[0069] In some embodiments, the additive manufacturing system 200 further comprises a photosensitive detector 240. The photosensitive detector 240 may be mounted vertically above the build surface 210 such that the detector may capture at least a portion of the build surface. Though instances in which the photo sensitive detector is not mounted vertically above the build surface are also contemplated. In some embodiments, the photosensitive detector 240 may be at least partially contained within or coupled to the optics assembly 204. However, in other configurations, the photosensitive detector 240 may be separately mounted to a gantry system, other movement state, or any other appropriate part of the additive manufacturing system.

[0070] Fig. 3 depicts one embodiment of an additive manufacturing system at the beginning of a build process. The additive manufacturing system includes a build plate 302 mounted on a fixed plate 304, which is in turn mounted on one or more vertical supports 306 that attach to a base 308 of the additive manufacturing system. In the depicted embodiment, the one or more vertical supports may correspond to one, two, and / or any other appropriate number of supports configured to support the build plate, and the corresponding build surface, at a desired position and orientation. For example, the supports depicted in the figure may correspond to one or more vertical motion stages configured to control a vertical position and orientation of the build plate. A powder containment shroud 310 may at least partially, and in some embodiments completely, surround a perimeter of the build plate 302to support a volume of precursor material on the build surface 302a, such as a volume of powder, disposed on the build plate and contained within the shroud. The shroud may be supported on the base 308 or by any other appropriate portion of the system.

[0071] The additive manufacturing system may include a powder deposition system in the form of a recoater 312 that is mounted on a horizontal motion stage 314 that allows the recoater to be moved back and forth across either a portion, or entire, surface of the build plate 302. As the recoater traversers the build surface 302a of the build plate, it deposits a precursor material on the build surface, such as a powder, onto the build plate and smooths the surface to provide a layer of precursor material with a predetermined thickness on top of the underlying volume of fused and / or unfused precursor material deposited during prior formation steps.

[0072] In some embodiments, the supports 306 of the build plate 302 may be used to index the build surface 302a of the build plate 302 in a vertical downwards direction relative to a local direction of gravity. In such an embodiment, the recoater 312 may be held vertically stationary for dispensing precursor material, such as a precursor powder, onto the exposed build surface 302a of the build plate as the recoater is moved across the build plate each time the build plate is indexed downwards.

[0073] In some embodiments, the additive manufacturing system may also include an optics assembly 318 that is supported vertically above and oriented towards the build plate 302. As detailed above, the optics assembly may be optically coupled to one or more laser energy sources, not depicted, to direct laser energy in the form or one or more laser energy pixels onto the build surface 302a of the build plate 302. To facilitate movement of the laser energy pixels across the build surface 302a, the optics assembly may be configured to move in one, two, or any number of directions in a plane parallel to the build surface of the build plate. To provide this functionality, the optics assembly may be mounted on a gantry 320, or other actuated structure, that allows the optics unit to be scanned in plane parallel to the build surface 302a of the build plate.

[0074] In the above embodiment, the build plate is indexed vertically while the remaining active portions of the system are held vertically stationary. However, embodiments, in which the build plate is held vertically stationary and the shroud 310, recoater 312, and optics assembly 318 are indexed vertically upwards relative to a local direction of gravity during formation of successive layers are also contemplated. In such an embodiment, the recoater horizontal motion stage 314 may be supported by vertical motionstages 316 that are configured to provide vertical movement of the recoater relative to the build plate. Corresponding vertical motion stages may also be provided for the shroud 310, not depicted, to index the shroud vertically upward relative to the build plate in such an embodiment. In some embodiments, the additive manufacturing system may also include an optics assembly 318 that is supported on a vertical motion stage 316 that is in turn mounted on the gantry 320 that allows the optics unit to be scanned in the plane of the build plate 302.

[0075] In the above embodiment, the vertical motion stages, horizontal motion stages, and gantry may correspond to any appropriate type of system that is configured to provide the desired vertical and / or horizontal motion. This may include supporting structures such as: rails; linear bearings, wheels, threaded shafts, and / or any other appropriate structure capable of supporting the various components during the desired movement. Movement of the components may also be provided using any appropriate type of actuator including, but not limited to, electric motors, stepper motors, hydraulic actuators, pneumatic actuators, electric actuators, and / or any other appropriate type of actuator as the disclosure is not so limited.

[0076] In addition to the above, in some embodiments, the depicted additive manufacturing system may include one or more controllers 324 that is operatively coupled to the various actively controlled components of the additive manufacturing system. For example, the one or more controllers may be operatively coupled to the one or more supports 306, recoater 312, optics assembly 318, the various motion stages, and / or any other appropriate component of the system. In some embodiments, the controller may include one or more processors and associated non-transitory computer readable memory. The non- transitory computer readable memory may include processor executable instructions that when executed by the one or more processors cause the additive manufacturing system to perform any of the methods disclosed herein.

[0077] In some embodiments, the additive manufacturing system 300 further comprises one or more photosensitive detectors 340. The one or more photosensitive detectors 340 may be mounted vertically above the build surface 302a in some embodiments such that the detector may be configured to image at least a portion, or an entirety, of the build surface. In some embodiments, the photosensitive detector 340 may be at least partially contained within or mounted to the optics assembly 318. However, in other configurations, the photosensitive detector 340 may be separately mounted to a gantry system, other motion stage, or any other appropriate part of the additive manufacturing system that permits the photosensitive detector to image the build surface 302a. While the one or more photosensitivedetectors may be scanned across the build surface in some embodiments, embodiments in which the one or more photosensitive detectors are mounted to a stationary portion of the system and are maintained stationary relative to the build surface are also contemplated.

[0078] Fig. 4 depicts one embodiment of an optics assembly 318 of an additive manufacturing system. Optics assembly 318 comprises a laser array 350 comprising a plurality of laser energy sources, which may be operated to selectively direct one or more corresponding laser energy pixels onto a build surface 302a, which may be coated with a precursor material (e.g., a fusible powder material such as a metal or thermoplastic powder). The currently operated laser energy sources and corresponding laser energy pixels may cause the formation of one or more corresponding melt pools 351 on the build surface. While only four laser energy sources and four corresponding melt pools are depicted in Fig. 4 for the sake of clarity, the disclosure is not so limited and may include any number of laser energy sources, laser energy pixels, and melt pools. In some embodiments, the laser energy pixels may be appropriately spaced from one another relative to a scanning direction of the optics assembly such that adjacent melt pools may be maintained as separate melt pools and avoid coalescence into a combined melt pool of uncontrolled size. A photosensitive detector 340, coupled to the optics assembly 318 or other appropriate portion of the system, may be used to capture at least one image of a portion of the build surface 302a including the laser energy pixels as well as the corresponding melt pools, welds, and / or other features formed on the build surface. In this embodiment, the photosensitive detector 340 captures a rectangular portion 341 of the build surface, but any other appropriately- shaped and / or sized portion of the build surface may be captured as well using any appropriate number of photosensitive detectors.

[0079] In some embodiments, multiple frames may be captured by the photosensitive detector. Again, this may correspond to the capture of a sequential series of images of the build surface. Further, depending on timing of the control of the laser energy sources and the photosensitive detector, the ability of the system to identify and sense information related to the various laser energy pixels may be impacted. For example, in some embodiments, the photosensitive detector may have a frame rate between 500-1000Hz and a frame time of 50 microseconds (ps) to avoid motion blur in the captured images. However, an additive manufacturing system may have a laser control rate of lOps. Additionally, due to mechanical limitations, frame time may vary either backwards or forwards by as much as half a frame. As such, in some cases, information related to a particular time point, may be located withinan image that is either one frame backwards and / or forwards from an expected time point associated with a build plan. The analysis and use of these time resolved images is elaborated on further below. However, it should be understood that in some alternative embodiments, the frame rate of the photosensitive detector may be the same and / or faster than the laser control rate of the additive manufacturing system in which case the above noted phenomenon may not be present in a system.

[0080] In the above described embodiment, the photosensitive detector 340 is mounted to the optics assembly 318, and thus, may move in sync with the optics assembly across the build surface. However, in other embodiments, the photosensitive detector may remain stationary and / or move separately from the optics assembly, as the disclosure is not so limited.

[0081] Fig. 5 depicts one embodiment of a registration method 400 for determining the locations and intensity values of one or more laser energy pixels projected onto a build surface by at least one laser energy source. To start, at least one image of at least a portion of a build surface with a plurality of laser energy pixels formed thereon may be captured in step 401. Alternatively, the at least one image may be obtained in an alternative fashion including recall from an associated non-transitory computer readable memory. The at least one image may be captured during weld formation where at least one laser energy source is activated to project one or more laser energy pixels onto the build surface to form one or more melt pools leading to the formation of one or more corresponding welds on the build surface. In some embodiments, the at least one image may be captured by a photosensitive detector, e.g., captured in the reference frame of the photosensitive detector. The photosensitive detector may be configured to capture the build surface in at least one dimension, e.g., using a line camera, though instances in which a photosensitive detector including a two dimensional array of pixels is used to capture the images are also contemplated. The melt pools, or other feature on or adjacent to the build surface, may emit light including in one or more wavelength ranges and with a corresponding intensity in the monitored one or more wavelength ranges.

[0082] In some embodiments, due to size, resolution, and quantity of the captured images, it may be desirable to compress the intensity values to decrease an amount of computation and / or storage required with further analysis of the captured images associated with registering the reference frame of the laser energy sources and the at least one photosensitive detector. Accordingly, in some embodiments, a maximum intensity of eachcolumn of pixels in the at least one captured image may be determined in step 402 using any appropriate comparison strategy. In some instances the columns may correspond to a smaller dimension of the array of photosensitive pixels and may extend in a direction that is at least partially parallel to a direction of motion of the optics assembly. Due to variations in laser energy pixel location as well as the above noted timing mismatch between laser energy source control and image integration, determining the maximum intensity values of each column of pixels may assist in providing a more consistent parameter to evaluate the captured intensity values and minimize the effect of any noise and / or variations. However, determining the maximum intensity values of intensity values may be optional.

[0083] In some embodiments, a one-dimensional array may be determined based at least in part on the previously determined maximum intensity values of the columns of a captured image, as shown in step 403. In embodiments where step 402 is performed, obtaining a one-dimensional array of the maximum intensity values may be desired to again reduce complexity and computational expense. This may include generating a onedimensional array with the previously determined maximum intensity values of each column of the at least one captured image indexed by pixel location. However, instances in which the full array of pixel intensity values are analyzed as well as instances in which a linear photosensitive detector, such that further compression of the measured signal may not be possible, are used are also contemplated. Steps 402 - 403 may be repeated for each image of the at least one image of the build surface captured by the photosensitive detector. However, embodiments in which the process is conducted for a subset of the images and / or for a single image are also contemplated.

[0084] In some embodiments, the intensity values may not be compressed into a onedimensional array, therefore skipping step 403. Instead, a two-dimensional array may be determined based at least in part on the intensity of a captured image, e.g., intensity values of a two-dimensional image may be left as a two-dimensional array. The determined two- dimensional array may then be used for the rest of the steps for analyzing the at least one captured image.

[0085] Due to variations in laser energy pixel operation over time as well as variations in height of the photosensitive detector relative to the build surface, it may be desirable to average a portion, and in some instances, all of the sequence of images together to reduce the influence of variations that may be present in any single image. Specifically, in some embodiments, the intensity values of the one dimensional arrays, or two dimensionalarrays of pixels, may be averaged with the corresponding pixels in a portion or the entire set of captured images at 404. Averaging may comprise taking a median or mean of the intensity values, as the disclosure is not so limited. As previously noted, averaging a one-dimensional array resulting from step 403 may decrease computational costs, but step 404 may be performed without prior compression of the intensity value arrays as well. Depending on the embodiment, the set of averaged images may be between or equal to 20 images and 100 images, though numbers of images both greater than and less than this may also be used.

[0086] In step 405, the averaged image, either compressed into a one-dimensional array or left in the original format of the image, may be transformed to a spatial frequency domain. The conversion of the averaged image into a spatial frequency domain may be performed using a Fourier transformation or other appropriate type of transform, though as previously noted, a Fast Fourier Transformation (FFT) may be preferred due to decreased computational costs and computational time. The spatial frequency domain may help with identifying any periodic properties present in the original captured image. For example, the periodic locations of the laser energy pixels on the build surface, due to a periodic arrangement of the plurality of laser energy sources projecting onto the build surface, may be displayed as a frequency with a relatively high power or amplitude, and thus may be easily identified as a peak amplitude present in the transformed image. Additional characteristic properties of the transformed image may be identified in step 406. In some embodiments, identified characteristic properties may comprise a characteristic frequency, an associated phase, and / or an associated amplitude. Some characteristic properties, such as the characteristic frequency, may be identified based at least in part on at least one property of the additive manufacturing system. In some embodiments, additive manufacturing system properties, such as a minimum expected laser energy pixel spacing, may be used to identify a minimum frequency threshold and may include but are not limited to at least one of an arrangement of a plurality of laser energy sources, a height of the photosensitive detector, and / or a resolution of the photosensitive detector. For example, in some systems, a minimum frequency threshold of the characteristic frequency of any images captured by the photosensitive detector in the spatial domain may be less than the spatial frequency associated with the spacing of the laser energy pixels on the build surface in the additive manufacturing system. Accordingly, a peak frequency greater (e.g., the frequency with the largest amplitude) than this minimum threshold frequency may be identified using anyappropriate peak identification method which may then be identified as a characteristic spatial frequency of the pixels within the images.

[0087] After the characteristic properties of the transformed image are determined in the spatial frequency domain, in some embodiments, the true locations of the laser energy pixels formed on the build surface in the captured images may be determined based at least in part of the identified characteristic properties, including, for example, a characteristic spatial frequency, at step 407. As previously described, in some embodiments, due to noise and / or interference in the surface features on the build surface, it may be difficult to directly obtain the true locations of the laser energy pixels accurately. As such, it may be desirable to use the periodic properties of the laser energy sources, e.g., even spacing within a laser array, consistent angles of the laser energy sources, and any other applicable forms of formulaic and / or predictable organization, to determine the true locations of the laser energy pixels within the captured images.

[0088] In one embodiment, determining the locations of the laser energy pixels within the images may include plotting, or otherwise, generating information related to a sinusoid, an equivalent cosine function, or any other appropriate periodic function using the identified characteristic properties. For example, step 407 may comprise plotting a sinusoid with the following equation: y(x~)= Acos(2 fx+ <p~) where f represents the identified characteristic spatial frequency, cp represents the identified phase, and A represents the identified amplitude. Methods to identify the phase, amplitude, and characteristic frequency of the transformed image may be obtained from the transformed image using any appropriate method including, but not limited to, Fourier transforms such as Fourier series, Fourier integrals, Discrete Fourier Transforms, and Fast Fourier Transformations (FFT). The plotted sinusoid may be plotted on an axis of pixel locations, and the peaks of each sinusoid may represent the locations of each laser energy pixel. The peaks of the sinusoid, or other periodic function, may represent locations on the build surface where the intensity values are the highest, which may be the locations where the laser energy pixels are projected on the build surface in the captured image, and these peak locations may be identified as a location of the laser energy pixels in the image. Furthermore, as amplitude does not affect the periodic properties of the plotted sine, or other periodic, function, it may be desirable to plot the sinusoid without using the identified amplitude in some embodiments, as shown in the equation below:y(x~)= cos(2nfx+ <p~)Thus, in some embodiments, the amplitude may not be determined or used.

[0089] In step 408, after the locations of the laser energy pixels in the image are acquired, intensity values of the laser energy pixels may be obtained. In some embodiments, the laser energy pixel intensities may be obtained by matching the averaged intensity values of the captured images from step 404 at the identified locations of the laser energy pixels determined in step 407 with a corresponding laser energy pixel. The averaged intensity values from step 404 and the identified laser energy pixel locations from 407 may be correlated with one another to determine intensities of the different laser energy pixels.

[0090] The determination of the locations of the one or more laser energy pixels on the build surface within the image may be used at least in part to register a reference frame of the photosensitive detector with a reference frame of the one or more laser energy pixels and system at 410. Specifically, the identified locations of the laser energy pixels within the image may be associated with separate groups of one or more pixels of a photosensitive detector. These separate groups of one or more pixels may then be correlated with the corresponding separate laser energy source and laser energy pixel of the system such that information associated with the separate laser energy pixels may be determined by measuring the parameters sensed by these separate groups of pixels of the photosensitive detector. It should be understood that this registration may be performed either with all of the laser energy pixels activated during registration and / or with a subset of the laser energy pixels as the periodic functions may be extended to include laser energy pixel positions that were not operated during image capture. In either case, the now registered photosensitive detector may be used to separately sense parameters associated with the separate laser energy pixels even though it is a single sensor. However, it should be understood that the disclosed method may be used on any number of photosensitive detectors as the disclosure is not so limited.

[0091] After the registration method 400 is complete, the information obtained in the registration method, including the obtained true locations and intensities of the laser energy pixels, may be used at least in part in additional processes, such as determining an operating state of at least one of the plurality of laser energy sources, controlling operation of one or more systems of an additive manufacturing system, and / or any other desired use.

[0092] Fig. 6 depicts one embodiment of a method 410 for determining an operating state of at least one laser energy source of a plurality of laser energy sources, as well as potential subsequent actions that may be taken following the determination of the operatingstates. In some embodiments, a method 410 for determining an operating state of at least one laser energy source may include obtaining a build plan of a part being produced at step 411. The build plan may be obtained from a build plan module configured to generate the build plan, or the build plan may be uploaded to the system, recalled from non-transitory computer readable memory, or obtained in any other appropriate manner. In some embodiments, the build plan may include processing parameters about the build process such as trajectory, timing, power, velocity, travel path, dimensions of the part and / or build surface, weld pattern, and / or expected locations and / or timing of the plurality of laser energy pixels firing on the build surface. In other embodiments, a build plan may not include an expected weld pattern and / or locations of the laser energy pixels, but may include other processing parameters which can be used to obtain expected locations of the plurality of laser energy pixels and / or an expected weld pattern. For example, from the timing of the firing of the plurality of laser energy sources, velocity of the optics assembly, and direction of travel, an expected weld pattern may be determined. Furthermore, in some embodiments, the expected weld pattern and / or expected locations of the plurality of laser energy pixels versus time may be obtained independently from a build plan, as shown in step 412. For example, the expected weld pattern and / or expected locations of the plurality of laser energy pixels may be directly imported and / or inputted into the additive manufacturing system.

[0093] After an expected weld pattern, which again may include the expected locations of the plurality of laser energy pixels versus time, during a build process is obtained, at least one image of the build surface may be captured for determining an operating state of at least a portion, and in some instances each, of the laser energy pixels. In some embodiments, the at least one photosensitive detector used to capture this image may already be registered to a reference frame of the laser energy pixels and overall system using the previously described registration process, or other appropriate registration process, such that a location of each laser energy pixel within the one, or serial time sequenced series, of images may be known. The image of the weld pools, which may be considered to correspond to the laser energy pixels, may be then compared at least in part to the expected weld pattern in step 413. The weld pattern may comprise information regarding a list of operating laser energy sources, their trajectories across the build surface, and / or their expected intensity values at a given time point. In some embodiments, a weld pattern may correspond to entire tracks of welds formed to a current point in a layer of powder and / or individual spots of expected locations of melt pools on the build surface depending on the specificimplementation of the disclosed methods. In some embodiments, a comparison process may include a pattern matching process. As noted above, due to variable distances between the photosensitive detector and the build surface, a method to analyze information robust to variable distances between a photosensitive detector and a build surface may be desirable in some embodiments. As such, the inventors have recognized that pattern matching may be desirable as pattern matching disregards the need for any physical measurements of the additive manufacturing system and / or measurements of the captured images, which may be affected by the variable distances between the photosensitive detector and the build surface. For example, in an additive manufacturing system, a list of operating laser energy sources may identify that a pattern of fifty contiguous laser energy sources is functional, and due to an even arrangement of the laser energy sources, the laser energy sources may be directed as a corresponding pattern of fifty contiguous laser energy pixels onto the build surface.

[0094] With such information, a comparison may then be made between an expected pattern of the plurality of laser energy pixels on the build surface and a captured pattern of the plurality of the laser energy pixels on the build surface. The pattern matching comparison may also allow each captured laser energy pixel on the build surface to be registered to at least one associated laser energy source in step 414. For example, a pattern matching comparison may determine that the pattern of the laser energy pixels on the build surface and the pattern of the functional laser energy sources are matching; and as such, the laser energy pixels may be registered to corresponding laser energy sources according to the matching pattern. Once the locations of the pixels within the image are known, one or more operating parameters associated with the separate laser energy pixels may then be sensed in step 415 using the separate groups of one or more pixels corresponding to the laser energy pixel locations within the image. Such operating parameters may include, but are not limited to an intensity, size, shape, or other appropriate parameter related to the operation of each of the separate laser energy sources of the plurality of laser energy sources.

[0095] While the above example describes the observed weld pattern and the expected weld pattern as completely matching, the laser energy pixels in an observed weld pattern may be registered with associated at least one associated laser energy source without the observed weld pattern matching completely with an expected weld pattern. For example, as known to those skilled in the art, a degree of tolerance may exist such that identical portions of a first and a second pattern can be identified and matched together despite the first and second patterns not being completely identical. Furthermore, in some embodiments, abuild plan and / or weld pattern may comprise information about laser energy pixels associated with various portions of the expected weld pattern. As such, any differences between the observed weld pattern and the expected weld pattern may also be used to help determine the operating states of the laser energy sources, which may occur in step 416 as elaborated on further below. For example, if all the laser energy sources are supposedly operating during a build process, pattern matching may predict that the expected weld pattern matches with an observed weld pattern of the build process. As such, any deviation in the observed weld pattern either in intensity, location, shape, or other operating parameter of the laser energy sources from the expected weld pattern may indicate that a failure has obtained, e.g., a failure state has occurred in at least one of the operating laser energy sources. Depending on the type of failure, this may either be viewed as a full failure or a partial failure. In some embodiments, the absence of a predicted laser energy pixel from an observed weld pattern may indicate a full failure in the associated laser energy source, e.g., a broken laser, as no intensity is emitted. However, in other embodiments, a missing predicted laser energy pixel may indicate a full or partial failure in the form of a misdirected and / or mis-orientated laser energy pixels. For example, the laser energy source may be functional and operating but firing at an incorrect location, which may be caused by a misalignment and / or misorientation in the plurality of laser energy sources in the optics assembly. Alternatively, an intensity of the laser energy pixel may be less than expected based on the commanded weld pattern.

[0096] Furthermore, in addition to pattern matching, the comparison step 413 may utilize other methods of comparing and registering the weld pools and corresponding laser energy pixels present in the at least one captured image to the expected weld pattern for registering the sensed information with the corresponding laser energy sources. For example, while pattern matching may be used to register imaged weld pools and laser energy sources in an image with the corresponding laser energy sources, the disclosure is not limited to only using pattern matching. For example, in some embodiments, a registration process such as that disclosed in Fig. 5 may have already been used to register a reference frame of the one or more photosensitive detectors to a reference frame of the build surface with the laser energy pixels and melt pools formed thereon. In such an embodiment, a location of each laser energy pixel within the single captured image, or the sequence of serially captured images, may be known such that information sensed by corresponding separate groups of pixels may be associated with the corresponding laser energy source without a need to perform a separate pattern matching process. In either case, operating parameters such as any one or more of anintensity, size, shape, or other appropriate parameter related to the operation of each of the separate laser energy sources of the plurality of laser energy sources may be sensed using the one or more photosensitive detectors.

[0097] Once the operating parameters of the laser energy sources have been obtained, an operating state of each laser energy source that is currently commanded to be in an active state with a laser energy pixel projected onto the build surface may be determined at 416. This determination may be based at least in part on the sensed one or more operating parameters associated with the different laser energy pixels and the corresponding expected operating parameters obtained from the build plan, and in some instances an expected weld pattern for the time period corresponding to the time period during which the image was captured. Potential methods for determining the operating state of the laser energy sources are detailed further below.

[0098] In some embodiments, an expected weld pattern may include information such as the size of any expected melt pools formed on the build surface, and the expected melt pool sizes may be compared to the sizes of the melt pools captured in an image by the photosensitive detector on the build surface. In some embodiments, due to the variable distance between the photosensitive detector and the build surface, it may be desirable to compare the size of the melt pools relatively to each other. For example, a build plan, or the weld pattern obtained from the build plan, may command the laser energy sources to form melt pools of either a single or multiple sizes. Thus, the sizes of the melt pools on the build surface may be compared to each other to determine relative differences between the imaged melt pools. When relative differences in the melt pool sizes that are greater than or less than those expected from the commanded size differences, this may be associated with a laser energy source failure for the laser energy source that is associated with a melt pool that is outside of an expected relative size threshold. Of course, embodiments in which the actual imaged melt pool size is compared to a size threshold directly are also contemplated.

[0099] In some embodiments, the operating determination step 416 may also include comparing the intensity values of the laser energy pixels in the at least one image to the intensity values of the expected weld pattern, which may be used at least in part to determine an operating state of at least one laser energy source of the plurality of laser energy sources. In some situations, a laser energy pixel may be present in an expected location but may exhibit a lower intensity value than commanded in the weld pattern, which may indicate the presence of a partial failure of the laser energy source associated with such a laser energypixel. For example, the lower intensity value may be caused by the associated laser energy source not receiving enough power, the associated laser energy source may be burning out, contamination may be present along the laser energy path extending through the optics system, and / or any other appropriate type of fault capable of causing a low intensity state of a laser energy source may be present. In some embodiments, an operating state of a laser energy source may be determined using a minimum intensity threshold below which the intensity of a laser energy pixel of a laser energy source may be classified as being in a failure state. This may help to avoid incorrect identifications of laser energy source failures due to variations in observed intensity due to variable heights between the photosensitive detector and the build surface, light interference from neighboring laser energy pixels, or other source of interference in the observed intensity signal for a given laser energy pixel.

[0100] While specific methods for identifying an operating state of the laser energy pixels are provided above, it should be understood that the operating states of the laser energy pixels, and thus the associated laser energy sources, may be determined in any appropriate manner using any appropriate sensed operating parameter of the laser energy pixels as the disclosure is not limited in this manner.

[0101] While not depicted in the flowchart of Fig. 6, in some embodiments, a visual representation of the determined operating states of the plurality of laser energy sources may be generated. For example, a point cloud may be a graphical representation with the determined operating states of each laser energy source depicted in a similar organization to the arrangement of laser energy sources. The point cloud, or any other visual representation, may allow for easy observation of failing laser energy sources and serve for visual inspection by an operator. An example of a visual representation is further described in Fig. 9.

[0102] In some embodiments, a confidence score of the additive manufacturing system may be optionally determined in step 417. A confidence score is associated with a level of confidence of a certainty of a determined operating state of each laser energy source. A higher confidence score may be associated with an increased probability that any determined operating state of any of the laser energy sources correctly reflects the real operating state of said laser energy sources. For example, depending on various circumstances a captured image may or may not include a laser energy pixel in the expected location for a given weld pattern. Specifically, as detailed previously above, a sequence of images may not include time points that are perfectly synchronized with the weld pattern for a given time point due to integration times associated with the images. Therefore, in someembodiments, if an expected laser energy pixel position is not identified in an image, a processor of a system may perform a similar analysis for a predetermined number of images (e.g., 1 image, 2 images, etc.) on either side of selected time point for a time sequenced series of images. In instances in which the expected weld pattern is identified in one of the other images, the properties associated with the one or more laser energy pixels in the identified image may be determined using any of the methods disclosed herein. If the one or more laser energy pixels are not identified in any of the selected images, it may be determined that the associated laser energy source may be in a failure state.

[0103] In addition to the above, a confidence level associated with a particular determined laser energy source may be updated over time. For example, if a specific operating state is identified once for a single image, the confidence score may be less than a confidence score for an operating state that is consistently identified at multiple sequential time points. Therefore, while any appropriate parameters may be used to determine a confidence score associated with a laser energy source operating state, in some embodiments, a confidence score may be based at least in part on: a number of identifications of an operating state; if an identified operating state is constant over a period of time; a severity of the identified operating state (e.g., a full failure versus partial failure); and / or any other appropriate consideration for determining a confidence score. Thus, a confidence score associated with an operating state of the one or more laser energy sources of a system, and the associated laser energy pixels, may be updated continuously during operation of a system.

[0104] Finally, operation of one or more systems or processes of the additive manufacturing system may be optionally controlled based at least in part on the determined operating states of one or more laser energy sources in step 418. For example, the additive manufacturing system may be programmed to respond to detected failures of the laser energy sources, and optionally based on a determined confidence score of the determined operating states. For example, an operating state of one or more laser energy sources associated with a confidence score greater than a threshold confidence score may be used to control operation of the one or more systems of an additive manufacturing system. This may include changing the laser energy sources used to perform a manufacturing process, generating a new build plan for forming parts with the operational laser energy pixels, changing an operating parameter of one or more laser energy pixels to be within a desired operating range, and / or any other appropriate operation of the additive manufacturing system. In some embodiments, an operation may be automatically taken by the system following a change in at least onedetected operating state of the laser energy sources. However, in alternative embodiments, an operation may be triggered by an operator in response to the detected change in at least one operating state. Furthermore, in some embodiments, any subsequent operation based at least in part on a determined operating state of one or more lasers may be also based at least in part on a determined confidence score of the additive manufacturing system. For example, an operating state associated with a higher confidence score is more likely to match a real operating state of the associated laser energy source, and a system may be more likely to implement changes in a commanded additive manufacturing process, or other process, based on a detected change in an operating state of one or more laser energy sources.

[0105] As noted above, in some circumstances, an additive manufacturing system with increased complexity, e.g., an increased number of lasers, larger parts, and / or more layers, may have an increased chance of failure in a given time period. Therefore, it may be desirable to repeat the registration and / or laser energy source operating state monitoring methods described in Figs. 5-6. Either one or both of these methods may be repeated continuously during a manufacturing process to monitor the state of the laser energy sources and / or at periodic intervals during a manufacturing process. This may include, for example, performing either or both of these methods during the formation of each layer, after the formation of each layer, after a predetermined number of layers have been formed, and / or with any other desired frequency as the disclosure is not limited in this fashion.

[0106] The above methods may be implemented by one or more controllers including at least one processor operatively coupled to the various controllable portions of an additive manufacturing system as disclosed herein. The methods may be embodied as computer readable instructions stored on non-transitory computer readable memory associated with the at least one processor such that when executed by the at least one processor the additive manufacturing system may perform any of the actions related to the methods disclosed herein. Additionally, it should be understood that the disclosed order of the steps is exemplary and that the disclosed steps may be performed in a different order, simultaneously, and / or may include one or more additional intermediate steps not shown as the disclosure is not so limited.

[0107] Example: Compressing a captured image into a ID array

[0108] Figs. 7A-7B depict one embodiment of compressing an image captured by a photosensitive detector into a one-dimensional array.

[0109] Fig. 7A depicts one embodiment of a method of analyzing at least one captured image of the build surface of an additive manufacturing system. The image 801 may be an image captured by a photosensitive detector, though instances in which a sequence of serially captured images are also contemplated as represented by a set of images 804. The photosensitive detector may detect variances in the build surface through properties such as intensity and / or temperature changes, which may result in surface features such as melt pools 802 being imaged on the build surface. While the melt pools 802 are depicted as being evenly spaced and symmetrical in Fig. 7A, in some embodiments they may overlap and / or comprise asymmetrical features. In this embodiment, the image 801 is collapsed into a onedimensional array 803, which may comprise the maximum intensity values of the captured image across its width which may correspond to the columns of the photosensitive detector in some embodiments. The one-dimensional array may be plotted on an axis associated with the pixel dimensions of the captured image. For example, Fig. 7B shows a close-up view of a portion of the one-dimensional array 803 from Fig. 7A in which the data is converted into a one-dimensional array of pixels with the identified maximum intensity values for each column. Locations in the one-dimensional array 803 with high intensity 805 may correspond to melt pools, while locations with low intensity 806 may correspond to portions of the build surface in the image 801 without any surface features. In this embodiment, the pixels intensities are represented as being either of high intensity or of low intensity in the onedimensional array 803, but values in the one-dimensional array may be more varied in practical applications where intermediate intensity values may also be present.

[0110] Example: Determining intensity values of a plurality of laser energy pixels

[0111] Fig. 8A-8G depict one example of a registration process.

[0112] Fig. 8A depicts a plot of the intensity values of an image of a build surface captured by a photosensitive detector. The raw signal may be collapsed into one dimension, and may indexed in terms of the pixels along a longitudinal axis of the image. In some embodiments, the raw signal may be collapsed into a one dimension by taking the maximum intensity along each column of the captured image as previously detailed above. In some embodiments, the raw signal may also comprise multiple captured images of the same trajectory, and the intensity values of the multiple captured images may be averaged to produce a representative intensity plot of the trajectory. From the intensity plot, areas of the image with surface features, e.g., melt pools, may be clearly identified. For example, the intensity plot clearly distinguishes higher intensity values around an amplitude of 2500 in the630 frame pixel to 950 frame pixel region, which may correspond to the melt pools present on the build surface.

[0113] Due to the properties of the additive manufacturing system, the laser energy sources of the system may be directed onto the build surface and form melt pools in an organized grid. The location where a laser energy pixel is directed onto the build surface may correspond to the highest intensity values observed in the image or collapsed one dimensional array, and due to the organized grid of the laser energy sources, a captured intensity plot of the build surface may include evenly spaced out peaks similar to the organized grid of the laser energy sources. However, as observed in the intensity plot of Fig. 8A, while the peaks of the intensity values may be somewhat organized, they are not perfectly evenly spaced out. The observed peaks may be subject to factors such as light interference and / or heat diffusion from nearby laser energy pixels on the build surface, which may affect the size and / or depth of any adjacent melt pools. Furthermore, due to factors such as powder layer thickness and gantry height, the distance between the photosensitive detector and the build surface may be variable. The variable distance may increase the difficulty of physically measuring the spacing and / or sizing of the laser energy pixels on the build surface. Thus, in order to accurately identify the locations of the laser energy pixels within the image, the image may be analyzed in a spatial frequency domain for its own characteristic properties, such as phase, amplitude, and / or characteristic spatial frequency.

[0114] For example, as seen in Fig. 8B, the intensity plot of Fig. 8A may be converted into the spatial frequency domain using any appropriate transform including for example a Fourier transform. In the spatial frequency domain, common observed frequencies of the intensity data may be expressed, and a characteristic frequency 901 corresponding to a peak frequency may be observed. The characteristic spatial frequency represents a common spacing identified in the captured images at which the surface features repeat. Due to physical properties of the additive manufacturing system, an appropriate frequency threshold less than an expected spatial frequency of the laser energy pixels may already be known and be used at least in part to identify the characteristic frequency. For example, the additive manufacturing system of Figs. 8A-8E may have a laser energy pixel spacing of 0.1 pixel'1, and as such, 0.1 pixel'1may be used as a minimal frequency threshold, wherein dimensions of a pixel are determined by properties of the photosensitive detector. In some embodiments, the photosensitive detector may be able to detect a pixel size greater than or equal to 10 pm and less than or equal to 1000 pm, which may correspond to a spatial frequency greater thanor equal to 1 mm'1and less than or equal to 100 mm'1. The minimal frequency threshold may recognize that the correct characteristic spatial frequency is greater than 0.1 pixel'1as the spatial frequency of the laser energy pixels is greater than this threshold. Thus, a peak frequency corresponding to a frequency with the maximum intensity greater than the frequency threshold may be used to identify the characteristic spatial frequency in some embodiments. This is reflected in Fig. 8B, where the identified characteristic frequency 901 was about 0.15 pixel'1.

[0115] It should be understood that while a specific frequency threshold and characteristic spatial frequency are shown in the figure, other additive manufacturing systems may have different laser energy pixel spacings and / or system properties, and the registration process may be adjusted accordingly. The characteristic frequency 901 may represent the laser energy pixel spacings within the one or more captured images, and may be used to identify the laser energy pixel locations and corresponding sensed parameters associated with the separate laser energy pixels. While not depicted, the spatial frequency domain may also be converted into a phase versus spatial frequency plot, and the characteristic frequency may be identified from the phase versus spatial frequency plot, and / or using any other appropriate method.

[0116] In the depicted example, a location of the one or more laser energy pixels in the reference frame of the photosensitive detector (e.g., the photosensitive sensor) was determined by using the identified characteristic properties of the image in the spatial frequency domain to plot a sinusoid. For example, in Fig. 8C, a sinusoid was plotted with the characteristic frequency and phase identified using the intensity plot in the spatial frequency domain in Fig. 8B. In Fig. 8C, the independent axis of the plotted sinusoid is in units of pixels and the peaks of the plotted sinusoid corresponded to the locations of the laser energy pixels within the image. The amplitude of the sinusoid does not affect the locations of the peaks and thus does not affect the locations of the laser energy pixels, and so in some embodiments. Thus, the amplitude of the transformed image in the spatial frequency domain was omitted in the sinusoid equation. The sinusoid in Fig. 8C may propagate infinitely, as such, only the range of pixels corresponding to the high intensity regions associated with detected surface features from Fig. 8A were examined. Furthermore, in some embodiments, limiting the generation of the sinusoid to the range of pixels associated with the detected melt pools may be advantageous by decreasing the amount of time and power associated with computing the sinusoid. In order to obtain the intensity values of the laser energy pixels intheir identified locations, as shown in Fig. 8D, the plotted sinusoid of Fig. 8C may be aligned with the intensity value plot of Fig. 8A. The plots may be aligned along their shared pixel axis.

[0117] Fig. 8E depicts a close-up view of a section of the aligned intensity and sinusoid plots form Fig. 8D. In Fig. 8E, the peaks of the sinusoid are registered with their corresponding peak intensity values in the actual intensity plot. The actual intensity values of the laser energy pixel locations within the image are indicated in Fig. 8F, where the laser energy pixel locations are evenly spaced out according to the peaks of the sinusoid.However, in Fig. 8F, there may exist outliers, ranging from around 600-620 pixels and from 960-970 pixels, wherein the predicted laser energy pixel locations do not demonstrate the high intensity values associated with the presence of melt pools. In some embodiments, a deviation from an expected intensity value may identify a laser failure. But in this embodiment, with prior information about the expected weld pattern of the additive manufacturing system, a pattern matching process may determine that the locations from 600-620 pixels and 960-970 pixels do not contain laser energy pixels. For example, the weld pattern may comprise a list of operating lasers, and in the embodiment of Fig. 8A-8E, there were fifty contiguous operating lasers. Since Fig. 8F shows over fifty potential locations for laser energy pixels, the fifty contiguous high intensity laser energy pixel locations were determined to be actual laser energy pixel locations and the separate pixels, or groups of pixels, associated with the different laser energy pixel locations with the images were registered with the corresponding laser energy pixel / laser energy source such that registered photosensitive detector may be used to separately monitor information related to the separate laser energy pixels. The intensity values associated with the actual laser energy pixel locations within the image are plotted in Fig. 8G.

[0118] Example : A visual representation of the operating state of the plurality of laser energy sources

[0119] Fig. 9 shows one embodiment of a visual representation, i.e., a point cloud, of the operating states of a plurality of laser energy sources. The point cloud may represent the plurality of laser energy sources in an array similar to how the plurality of laser energy sources are organized in the optics assembly, wherein each laser energy source is represented with a circle. In this embodiment, the presence of a circle at the location of a laser energy source may represent that that particular laser energy source is functional, and a lack of a circle may represent that the laser energy source is failing. The visual representation of thepoint cloud is advantageous as the lack of any circles may allow an operator to easily identify any failing laser energy sources. In alternative embodiments, a point cloud may be designed such that the point cloud is capable of representing partial failures such as intermittent operation, partial power, and any other applicable partial failures may be identified. For example, in some embodiments, the circles of a point cloud may be filled in to represent full functionality, and a partial power failure may be represented with a partially filled circle and / or a circle filled in with decreased intensity.

[0120] The above-described embodiments of the technology described herein can be implemented in any of numerous ways. For example, the embodiments may be implemented using hardware, software or a combination thereof. When implemented in software, the software code can be executed on any suitable processor or collection of processors, whether provided in a single computing device or distributed among multiple computing devices. Such processors may be implemented as integrated circuits, with one or more processors in an integrated circuit component, including commercially available integrated circuit components known in the art by names such as CPU chips, GPU chips, microprocessor, microcontroller, or co-processor. Alternatively, a processor may be implemented in custom circuitry, such as an ASIC, or semicustom circuitry resulting from configuring a programmable logic device. As yet a further alternative, a processor may be a portion of a larger circuit or semiconductor device, whether commercially available, semi-custom or custom. As a specific example, some commercially available microprocessors have multiple cores such that one or a subset of those cores may constitute a processor. Though, a processor may be implemented using circuitry in any suitable format.

[0121] Further, it should be appreciated that a computing device including one or more processors may be embodied in any of a number of forms, such as a rack-mounted computer, a desktop computer, a laptop computer, or a tablet computer. Additionally, a computing device may be embedded in a device not generally regarded as a computing device but with suitable processing capabilities, including a Personal Digital Assistant (PDA), a smart phone, tablet, or any other suitable portable or fixed electronic device.

[0122] Also, a computing device may have one or more input and output devices. These devices can be used, among other things, to present a user interface. Examples of output devices that can be used to provide a user interface include display screens for visual presentation of output and speakers or other sound generating devices for audible presentation of output. Examples of input devices that can be used for a user interfaceinclude keyboards, individual buttons, and pointing devices, such as mice, touch pads, and digitizing tablets. As another example, a computing device may receive input information through speech recognition or in other audible format.

[0123] Such computing devices may be interconnected by one or more networks in any suitable form, including as a local area network or a wide area network, such as an enterprise network or the Internet. Such networks may be based on any suitable technology and may operate according to any suitable protocol and may include wireless networks, wired networks or fiber optic networks.

[0124] Also, the various methods or processes outlined herein may be coded as software that is executable on one or more processors that employ any one of a variety of operating systems or platforms. Additionally, such software may be written using any of a number of suitable programming languages and / or programming or scripting tools, and also may be compiled as executable machine language code or intermediate code that is executed on a framework or virtual machine.

[0125] In this respect, the embodiments described herein may be embodied as a computer readable storage medium (or multiple computer readable media) (e.g., a computer memory, one or more floppy discs, compact discs (CD), optical discs, digital video disks (DVD), magnetic tapes, flash memories, RAM, ROM, EEPROM, circuit configurations in Field Programmable Gate Arrays or other semiconductor devices, or other tangible computer storage medium) encoded with one or more programs that, when executed on one or more computers or other processors, perform methods that implement the various embodiments discussed above. As is apparent from the foregoing examples, a computer readable storage medium may retain information for a sufficient time to provide computer-executable instructions in a non-transitory form. Such a computer readable storage medium or media can be transportable, such that the program or programs stored thereon can be loaded onto one or more different computing devices or other processors to implement various aspects of the present disclosure as discussed above. As used herein, the term "computer-readable storage medium" encompasses only a non-transitory computer-readable medium that can be considered to be a manufacture (i.e., article of manufacture) or a machine. Alternatively or additionally, the disclosure may be embodied as a computer readable medium other than a computer-readable storage medium, such as a propagating signal.

[0126] The terms “program” or “software” are used herein in a generic sense to refer to any type of computer code or set of computer-executable instructions that can be employedto program a computing device or other processor to implement various aspects of the present disclosure as discussed above. Additionally, it should be appreciated that according to one aspect of this embodiment, one or more computer programs that when executed perform methods of the present disclosure need not reside on a single computing device or processor, but may be distributed in a modular fashion amongst a number of different computers or processors to implement various aspects of the present disclosure .

[0127] Computer-executable instructions may be in many forms, such as program modules, executed by one or more computers or other devices. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types. Typically the functionality of the program modules may be combined or distributed as desired in various embodiments.

[0128] The embodiments described herein may be embodied as a method, of which an example has been provided. The acts performed as part of the method may be ordered in any suitable way. Accordingly, embodiments may be constructed in which acts are performed in an order different than illustrated, which may include performing some acts simultaneously, even though shown as sequential acts in illustrative embodiments.

[0129] Further, some actions are described as taken by a “user” and / or “operator.” It should be appreciated that a “user” and / or “operator” need not be a single individual, and that in some embodiments, actions attributable to a “user” and / or “operator” may be performed by a team of individuals and / or an individual in combination with computer-assisted tools or other mechanisms.

[0130] While the present teachings have been described in conjunction with various embodiments and examples, it is not intended that the present teachings be limited to such embodiments or examples. On the contrary, the present teachings encompass various alternatives, modifications, and equivalents, as will be appreciated by those of skill in the art. Accordingly, the foregoing description and drawings are by way of example only.

Claims

CLAIMS1. A method for monitoring a plurality of laser energy sources of an additive manufacturing system, the method comprising: obtaining a weld pattern for one or more parts being formed by the additive manufacturing system; obtaining at least one image of a build surface as the one or more parts are formed by the additive manufacturing system; and comparing the at least one image to the weld pattern to determine an operating state of at least one laser energy source of the plurality of laser energy sources.

2. The method of claim 1, further comprising obtaining a build plan for the one or more parts being formed by the additive manufacturing system, wherein obtaining the weld pattern includes determining the weld pattern based at least in part on the build plan.

3. The method of any one of claims 1-2, wherein obtaining the at least one image of the build surface comprises imaging the build surface with a photosensitive detector.

4. The method of claim 1, further comprising registering a plurality of laser energy pixels to the plurality of laser energy sources, and wherein determining the operating state of the at least one laser energy source is based at least in part on the registered plurality of laser energy pixels.

5. The method of claim 4, wherein registering the laser energy pixels to the plurality of laser energy sources comprises registering a reference frame of a photosensitive detector used to image the plurality of laser energy pixels with a reference frame of the plurality of laser energy pixels based at least in part on an the at least one image.

6. The method of claim 4, further comprising analyzing the at least one image to identify at least one location of the plurality of laser energy pixels in the at least one image.

7. The method of claim 1, wherein the operating state of the at least one laser energy source of the plurality of laser energy sources is a failure state.

8. The method of claim 7, wherein the failure state is at least one selected from a full failure and a partial failure.

9. The method of claim 1, wherein comparing the at least one image to the weld pattern comprises comparing intensity values of a plurality of laser energy pixels in the at least one image to the weld pattern.

10. The method of any one of claims 1-9, further comprising controlling one or more systems of the additive manufacturing system based at least in part on the determined operating state of the at least one laser energy source.

11. The method of claim 1, further comprising determining a confidence score associated with the determined operating state of the at least one energy source, and wherein controlling the one or more systems of the additive manufacturing system is based at least in part on the confidence score.

12. The method of any one of claims 1-11, wherein obtaining the at least one image of a build surface and comparing the at least one image to the weld pattern is performed continuously during a manufacturing process.

13. A non-transitory computer readable memory including processor executable instructions that when executed by one or more processors perform any one of the methods of any one of claims 1-12.

14. An additive manufacturing system comprising: a build surface; a plurality of laser energy sources configured to direct laser energy from the plurality of laser energy sources toward the build surface to form a plurality of laser energy pixels on the build surface; a photosensitive detector configured to image at least a portion of the build surface including the plurality of laser energy pixels when the plurality of laser energy pixels are formed thereon; andat least one processor configured to: obtain a weld pattern for one or more parts being formed by the additive manufacturing system; obtain at least one image of the build surface as the one or more parts are formed by the additive manufacturing system using the photosensitive detector; and compare the at least one image to the weld pattern to determine an operating state of at least one laser energy source of the plurality of laser energy sources.

15. The additive manufacturing system of claim 14, further comprising an optics assembly movable relative to the build surface and configured to direct the laser energy from the plurality of laser energy sources toward the build surface to form the plurality of laser energy pixels, wherein the photosensitive detector is configured to move in sync with the optics assembly.

16. The additive manufacturing system of claim 14, wherein the at least one processor is configured to obtain a build plan for the one or more parts being formed by the additive manufacturing system, and wherein the at least one processor is configured to obtain the weld pattern based at least in part on the build plan.

17. The additive manufacturing system of claim 14-16, wherein the at least one processor is configured to obtain the at least one image of the build surface by imaging the build surface with the photosensitive detector.

18. The additive manufacturing system of claim 14, wherein the at least one processor is configured to register the plurality of laser energy pixels to the plurality of laser energy sources.

19. The additive manufacturing system of any one of claims 17-18, wherein the at least one processor is configured to register the plurality of laser energy pixels to the plurality of laser energy sources by registering a reference frame of the photosensitive detector with a reference frame of the plurality of laser energy pixels based at least in part on the at least one image.

20. The additive manufacturing system of claim 14, wherein the operating state of the at least one laser energy source of the plurality of laser energy sources is a failure state.

21. The additive manufacturing system of claim 20, wherein the failure state is at least one selected from a full failure and partial failure.

22. The additive manufacturing system of claim 14, wherein the at least one processor is configured to compare the at least one image to the weld pattern by comparing intensity values of a plurality of laser energy pixels in the at least one image to the weld pattern.

23. The additive manufacturing system of claim 14, wherein the at least one processor is configured to analyze the at least one image to identify at least one location of the plurality of laser energy pixels in the at least one image.

24. The additive manufacturing system of claim 23, wherein the at least one processor is configured to register a reference frame of the photosensitive detector with a reference frame of the plurality of laser energy pixels based at least in part on the identified at least one location of the plurality of laser energy pixels in the at least one image.

25. The additive manufacturing system of any one of claims 14-24, wherein the at least one processor is configured to control one or more systems of the additive manufacturing system based at least in part on the determined operating state of the at least one laser energy source.

26. The additive manufacturing system of claim 25, wherein the at least one processor is configured to determine a confidence score associated with the determined operating state of the at least one energy source, and wherein the at least one processor is configured to control the one or more systems of the additive manufacturing system based at least in part on the confidence score.

27. The additive manufacturing system of claim 14, wherein the at least one processor is configured to obtain the at least one image of the build surface and compare the at least one image to the weld pattern continuously during a manufacturing process.

28. The additive manufacturing system of claim 14, wherein the photosensitive detector is disposed in a plane vertically above the build surface during a manufacturing process.

29. The additive manufacturing system of claim 14, wherein the photosensitive detector comprises a resolution equal to or greater than a pixel size of the plurality of laser energy pixels on the build surface.

30. The additive manufacturing system of claim 14, wherein the photosensitive detector is configured to capture light from at least one selected from an infrared, near-infrared, and visible spectrum.

31. The method of any one of claims 1-12, further comprising fusing precursor material on a build surface with laser energy from the at least one laser energy source of the plurality of laser energy sources to form the one or more parts on the build surface.

32. A part manufactured using the method of claim 31.

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