Optical fiber including an end cap for use in additive manufacturing - Patents.com

Abstract

Additive manufacturing systems and methods are generally described. In accordance with certain aspects, an end cap is provided that is optically coupled to an optical fiber of an additive manufacturing system. In some aspects, a method is provided for reducing the power areal density of laser energy within the end cap. The end caps described herein may be used to at least partially mitigate thermal cycling that may result from the transmission of laser energy through an interface of an additive manufacturing system.

Description

[Technical field]

[0001] Related Applications This application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Application No. 63 / 234,816, entitled “OPTICAL FIBERS INCLUDING ENDCAPS FOR USE IN ADDITIVE MANUFACTURING,” filed August 19, 2021, which is incorporated by reference in its entirety for all purposes.

[0002] Generally, systems and methods for manipulating laser energy using end caps in additive manufacturing systems are described. [Background technology]

[0003] The manufacturing speed and throughput of some additive manufacturing systems, such as powder bed fusion systems, is limited by the rate at which powder materials can be fusion bonded. The rate of material fusion bonding depends on several factors, including the total power delivered to the powder material in the build volume of the system, as well as the energy per unit mass used to fusion bond the powder material. In some instances, such as systems that utilize one or more laser energy sources to deliver power to the build volume, the rate of fusion bonding can be increased by including multiple laser energy sources. For example, by increasing the number of laser energy sources that can simultaneously fusion bond powder in a powder bed fusion process, the total power delivered to the build volume can be increased, which in turn can increase the rate of fusion bonding. Summary of the Invention

[0004] The subject matter of the present disclosure may in some cases involve interrelated products, alternative solutions to a particular problem, and / or a number of different uses of one or more systems and / or articles.

[0005] In one aspect, an additive manufacturing system is provided. In some embodiments, the additive manufacturing system includes a laser energy source, an optical assembly configured to direct laser energy from the laser energy source onto a build surface to form a laser energy spot on the build surface, an optical fiber optically coupled to the laser energy source, and an end cap disposed on and optically coupled to a distal end of the optical fiber, wherein a surface area of ​​a distal surface of the end cap is greater than a cross-sectional area of ​​the distal end of the optical fiber, the end cap optically coupled to the optical assembly.

[0006] In another aspect, an additive manufacturing system is provided that, in some embodiments, includes a laser energy source, an optical assembly configured to direct laser energy from the laser energy source onto a build surface to form a laser energy spot on the build surface, an optical fiber optically coupled to the laser energy source, and an end cap disposed on a distal end of the optical fiber and optically coupled to the optical fiber, the end cap configured to increase a transmission area of ​​laser energy transmitted from the laser energy source to reduce a power areal density of the transmitted laser energy.

[0007] In yet another aspect, a method of additive manufacturing is provided, in some embodiments, that includes transmitting laser energy from a laser energy source along an axial dimension of an optical fiber, reducing a power areal density of the transmitted laser energy by increasing a transmission area of ​​the transmitted laser energy within an end cap disposed on and optically coupled to the optical fiber, and directing the laser energy output from the end cap onto a build surface to form a laser energy spot on the build surface.

[0008] In another aspect, a method of additive manufacturing is provided. In some embodiments, the method of additive manufacturing includes a plurality of laser energy sources, an optical assembly configured to direct laser energy from the plurality of laser energy sources onto a build surface to form an array of laser energy spots on the build surface, a plurality of optical fibers optically coupled to the plurality of laser energy sources, and one or more end caps disposed on and optically coupled to a distal end of each of the optical fibers, each end cap of the one or more end caps having a distal surface area greater than a cross-sectional area of ​​a distal end of an optical fiber disposed therein, the plurality of optical fibers forming an array.

[0009] Other advantages and novel features of the present disclosure will become apparent from the following detailed description of various non-limiting embodiments of the present disclosure, when considered in conjunction with the accompanying drawings. In the event that this specification and a document incorporated by reference include conflicting and / or inconsistent disclosure, the present specification shall control. [Brief description of the drawings]

[0010] Non-limiting embodiments of the present disclosure will now be described, by way of example, with reference to the accompanying drawings. The drawings are schematic and are not intended to be drawn to scale unless otherwise indicated. In the drawings, each identical or nearly identical component illustrated is typically represented by a single numeral. For clarity, not every component is labeled in every figure, nor are every component of each embodiment of the present disclosure shown unless illustration is necessary to enable a person skilled in the art to understand the present disclosure.

[0011] [Figure 1] 1 illustrates an additive manufacturing system comprising a laser energy source, an optical fiber, an optical assembly, and a build surface, in accordance with certain embodiments. [Diagram 2]1 illustrates an additive manufacturing system comprising a laser energy source, an optical fiber, an end cap, an optical assembly, and a build surface, in accordance with certain embodiments. [Figure 3A] 1 illustrates an exemplary cylindrical end cap optically coupled to an optical fiber, according to certain embodiments. [Figure 3B] 1 illustrates an exemplary prism end cap optically coupled to an optical fiber, according to certain embodiments. [Figure 3C] 1 illustrates an exemplary end cap optically coupled to two optical fibers, according to certain embodiments. [Figure 3D] 1 illustrates an exemplary microlens end cap optically coupled to an optical fiber, according to certain embodiments. [Figure 3E] 1 illustrates an exemplary end cap optically coupled to an optical fiber, according to certain embodiments. [Figure 3F] 1 illustrates an exemplary end cap with two convex microlens portions optically coupled to two optical fibers, according to certain embodiments. [Figure 4A] 1 illustrates an exemplary alignment fixture and a linear array of exemplary end caps, in accordance with certain embodiments. [Figure 4B] 1 illustrates an exemplary alignment fixture and a two-dimensional array of exemplary end caps, in accordance with certain embodiments. [Diagram 5] 1 illustrates an exemplary alignment fixture with an optical fiber and a corresponding end cap positioned therein, in accordance with certain embodiments. [Figure 6] 1 illustrates an exemplary alignment fixture with an optical fiber and a corresponding end cap positioned therein, in accordance with certain embodiments. [Figure 7] 1 illustrates an exemplary alignment fixture with an optical fiber and a corresponding end cap positioned therein, in accordance with certain embodiments. [Figure 8]1 illustrates the transmission of laser energy from an optical fiber optically coupled to an end cap in an exemplary alignment fixture to individual microlenses in accordance with certain embodiments. [Figure 9] 1 illustrates the transmission of laser energy from an optical fiber optically coupled to an end cap in an exemplary alignment fixture to a microlens array in accordance with certain embodiments. [Figure 10] 1 illustrates the transmission of laser energy from an optical fiber optically coupled to an end cap in an exemplary alignment fixture to a macro lens in accordance with certain embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The inventors have realized that additive manufacturing systems utilizing multiple optical fibers to deliver laser energy from one or more laser energy sources to a powder within a build volume may present additional challenges. For example, it may be difficult to precisely align the exit surface of the optical fiber with respect to downstream optics (e.g., lenses, lens arrays, mirrors, etc.). The distal surfaces of the optical fibers also act as interfaces that may result in scattering, back-reflection, and / or absorption of a portion of the laser energy transmitted through each of the optical fibers. Thus, when the laser energy sources are operated to deliver large power to the build surface, these interfaces may result in undesirable heating of the ends of the optical fibers as well as undesirable back-reflection of the laser energy toward the associated laser energy source or sources. As the lasers are repeatedly cycled between on and off states during the additive manufacturing process, this may result in damage to the laser source or sources as well as cyclic heating and cooling of the distal ends of the optical fibers. Additionally, at sufficiently high power settings, this heating of the distal ends of the optical fibers may even result in melting of the optical fibers.

[0013] The inventors have recognized that the above-mentioned problems may become more pronounced as the laser power associated with an additive manufacturing process is increased. Accordingly, the inventors have recognized and appreciated the numerous advantages associated with reducing the power areal density of energy emitted from an interface located at the distal end of one or more optical fibers connected to an additive manufacturing system. For example, in some embodiments, an additive manufacturing system may include one or more end caps optically and physically coupled to the distal end of one or more associated optical fibers used to provide laser energy to the additive manufacturing system. The end caps may reduce the power areal density of the transmitted laser energy prior to transmission through the distal surface of the end cap by providing an increased transmission area of ​​the laser energy relative to the cross-sectional area of ​​the optical fiber without the end cap.

[0014] In some embodiments, an end cap disposed on and optically coupled to one or more associated optical fibers may have a distal surface with a surface area that may be greater than a cross-sectional area of ​​the distal end of the one or more optical fibers coupled to the end cap. According to certain embodiments, the increased surface area of ​​the distal surface of the end cap relative to the surface area of ​​the distal end of the optical fiber may provide a desired reduction in the power areal density of laser energy transmitted from the one or more end caps.

[0015] In some embodiments, the end caps associated with one or more optical fibers of the system may be constructed from any suitable material that is optically transparent to the transmitted laser energy. Also, in some instances, the end caps may be the same material as the associated optical fiber, which may help to avoid scattering at the interface between the optical fiber and the connected end cap. Suitable materials for the optical fibers and / or end caps may include, but are not limited to, fused silica, fused quartz, germanium doped silica, sapphire, rare earth doped fused silica, and / or any other suitable material.

[0016] The end caps of the various embodiments disclosed herein may be optically and physically connected to the associated optical fiber in any suitable manner. However, in some embodiments, it may be advantageous to melt bond the distal end of the optical fiber to the associated end cap. This may be accomplished by melting and joining adjacent portions of the optical fiber and the end cap, thereby eliminating the interface between these components. Eliminating this interface may reduce scattering and back reflection of the transmitted laser energy. Suitable methods for melt bonding the optical fiber and the end cap may include, but are not limited to, arc fusion, CO2 laser, optical contact bonding, and / or any other suitable fusion bonding method. Of course, embodiments are contemplated in which different types of connections are used between the optical fiber and the end cap, including, for example, index-matched optical adhesives, hydroxide bonding, and / or any other suitable type of connection.

[0017] As described in more detail below, the end caps described in various embodiments herein may have any suitable size and / or shape to provide the desired functionality. For example, the end cap may be configured such that the transmitted laser energy is transmitted through a curved distal surface, such as a microlens, a flat distal surface, or any other suitably shaped distal surface. A curved distal surface configured to act as a lens may, according to certain embodiments, advantageously help to shape the transmitted laser energy and reduce the portion of the laser energy that is reflected back through the optical fiber to the laser energy source. However, embodiments of the end cap having shapes different from those described above are also contemplated, as the disclosure is not limited in this manner.

[0018] Depending on the application, the additive manufacturing system may include any suitable number of one or more end caps and one or more corresponding optical fibers. For example, in some embodiments, each of the end caps may be optically coupled to a distal end of an individual optical fiber of either one or more optical fibers (e.g., at least two optical fibers). According to another embodiment, each of the end caps may be coupled to a distal end of a separate group of optical fibers, each group including multiple optical fibers. Of course, embodiments in which combinations of the above arrangements are used are also contemplated. Specific examples of these configurations are detailed further below.

[0019] In some embodiments, the additive manufacturing system may include a laser energy source (e.g., multiple laser energy sources) and an optical assembly configured to direct laser energy from the laser energy source (e.g., multiple laser energy sources) onto the build surface. According to some embodiments, one or more end caps are optically coupled to one or more laser energy sources and one or more associated optical fibers as described above. Correspondingly, the one or more end caps may be optically coupled to the optical assembly of the additive manufacturing system in any suitable manner. In one such embodiment, the laser energy output from the one or more end caps may be directed onto the build surface through one or more optical components (e.g., lenses, optical fibers, galvo scanners, lens arrays, etc.) of the intervening optical assembly to form a laser energy spot on the build surface. Exposure of the laser energy to the powder material on the build surface may be used to melt and bond at least a portion of the powder to form a desired geometry on the build surface. In some examples, the optical assembly may be configured to form an array of laser energy spots on the build surface from the laser energy from each laser energy source. For example, the optical assembly may be configured to direct the laser energy from each laser energy source to form one or more corresponding laser energy spots in the array. According to certain embodiments, the array of laser spots may be a linear array. However, according to certain embodiments, the array of laser spots may be a two-dimensional array. Additionally, additive manufacturing systems in which only a single laser energy spot is used are also contemplated, as the disclosure is not limited in this manner.

[0020] One or more fiber optic connectors may be used to facilitate connection of the laser to the additive manufacturing system. In one such embodiment, the system may further include a fiber optic connector coupled to any one or more of the laser energy sources (e.g., of the multiple laser energy sources and the optical assembly). For example, a first optical fiber or multiple optical fibers may be optically coupled to one or more corresponding laser energy sources and extend to and connect with the fiber optic connector. Also, a second optical fiber or multiple optical fibers may extend from the fiber optic connector to an optical assembly to which the second multiple optical fibers may be optically coupled. As described in more detail below, the fiber optic connector may be configured such that one or more second optical fibers may be optically coupled to corresponding ones of the one or more first optical fibers in the fiber optic connector. In this manner, laser energy from the laser energy source or multiple laser energy sources may be transmitted via the first optical fiber or multiple optical fibers to the fiber optic connector and then via the second optical fiber or multiple optical fibers to the optical assembly, whereby the laser energy may be delivered to the build surface. In some embodiments, the fiber optic connector may be connected to either a stationary or a movable optical assembly. In either case, the disclosed optical fibers and associated end caps may be used at any interface between a laser source and an optical assembly where it may be desirable to reduce the power areal density of the laser energy transmitted through the system. This may include, for example, one or both of the above-mentioned connections between individual optical fibers and optical fibers that comprise an optical assembly. Thus, it should be understood that the use of the disclosed optical fibers and associated end caps is not limited to only the specific configurations and embodiments described herein.

[0021] In various embodiments described herein, the laser energy may be generated by one or more independently controllable laser energy sources that operate to deliver the laser energy to the optical assembly through one or more individual optical fibers associated with the laser energy sources. It should be understood that any suitable type of optical fiber may be used, including, for example, a solid core optical fiber. However, in other embodiments, the one or more optical fibers may include fiber segments spliced ​​together to form a single optical fiber. Alternatively or additionally, a single optical fiber path may be created by using an optical connector to couple the ends of two fibers together.

[0022] Regardless of the specific optical fiber structure, each optical fiber optically connected to one or more laser energy sources of the additive manufacturing system may be appropriately routed and optically connected to the optical assembly of the additive manufacturing system. In some embodiments, the distal ends of one or more optical fibers may be disposed and optically coupled to end caps housed in a mounting fixture (e.g., a fiber holder), with the mounting fixture ensuring that the end caps of the optical fibers are properly aligned. For example, when the additive manufacturing system includes multiple optical fibers, according to certain embodiments, the distal end portions of the optical fibers may be oriented parallel to one another, and the distal ends of the end caps may be aligned to one another at predetermined axial positions within the mounting fixture. This may facilitate coupling of the mounting fixture and associated optical fibers to the optical assembly of the system. Specific structures and mechanisms for aligning the end caps of the system are described in more detail below with reference to the figures.

[0023] As mentioned above, in some embodiments, an optical fiber extends between a laser energy source (and / or multiple laser energy sources) and an optical assembly of an additive manufacturing system. The optical fiber may be used to transmit laser energy from the laser energy source along the axial dimension of the optical fiber, according to certain embodiments. The optical fiber may be directly connected to the laser energy source and / or the optical assembly. For example, according to some embodiments, the optical fiber is directly connected to both the optical assembly (e.g., at the distal end of the optical fiber) and the laser energy source (e.g., at the proximal end of the optical fiber). In some embodiments, the optical fiber is directly connected only to either the optical assembly or the laser energy source. For example, according to certain embodiments, one end of the optical fiber is connected to an optical connector as described herein and another optical fiber is connected to the optical assembly. In some further embodiments, the optical fiber is not directly connected to either the laser energy source or the optical assembly. The optical fibers and associated end caps disclosed herein may be incorporated in any suitable location between the laser energy source and the optical assembly where it would be desirable to reduce the power areal density of the laser energy transmitted through the system.

[0024] According to certain embodiments, the optical fiber may be a single optical fiber or one of a plurality of optical fibers. In some embodiments, a plurality of optical fibers according to certain embodiments may be aligned in corresponding predetermined positions and orientations. In particular, according to certain embodiments, the optical fibers may be axially aligned with one another in an optical assembly as described herein. For example, the optical fibers may be axially aligned such that distal ends of end caps associated with the plurality of optical fibers are positioned within a predetermined range (i.e., tolerance) of a desired axial position in the system. The optical fibers may also be aligned in one or more transverse directions relative to the axial direction of the optical fibers. For example, the optical fibers may be aligned with one another relative to the width and / or thickness direction of the optical fibers in an array arrangement of optical fibers. In some embodiments, the optical fibers and end caps may be aligned in a linear array. According to other embodiments, the optical fibers and end caps may be aligned in a two-dimensional array. The alignment of the optical fibers may provide advantageous placement of the laser energy pixels and favorable positioning of the end caps of the plurality of optical fibers relative to downstream optical elements, according to certain embodiments.

[0025] As discussed above, it may be desirable to precisely locate and position the ends of the optical fibers and / or associated end caps within a system. Accordingly, in some embodiments, one or more optical fibers of a system may be coupled to an alignment fixture. For example, the alignment fixture may define a desired spatial distribution and / or orientation of the ends of the optical fibers and associated end caps. In one such embodiment, the alignment fixture may orient each optical fiber to be oriented in a parallel direction such that light traveling through the optical fiber may exit the alignment fixture along one or more paths parallel to a desired transmission direction. To improve this desired directionality, in some embodiments, a distal surface of one or more end caps associated with one or more optical fibers held within the alignment fixture may be optically polished after being positioned within the alignment fixture. The alignment fixture may also facilitate precise positioning of one or more optical fibers in a predetermined location relative to a width and / or thickness of the alignment fixture, where the width and thickness directions may be perpendicular to the length of the alignment fixture parallel to the longitudinal axis of the portion of the optical fiber positioned within the alignment fixture. In certain embodiments, the alignment fixture may include a plurality of alignment features, such as v-grooves, holes, optical wedges, optical blocks, and / or any other suitable alignment features, into which the optical fibers and / or end caps are positioned, glued, or otherwise suitably positioned or engaged, such that the alignment fixture is configured to properly position the optical fibers and / or end caps. In some embodiments, the alignment features may be arranged in any suitable manner to define a desired spatial distribution of the ends of the optical fibers held within the alignment fixture.

[0026] In some embodiments, the incident laser spot on the build surface may be arranged in a line having a major dimension and a minor dimension, or in an array. In either case, according to some aspects, the line or array of incident laser energy consists of a number of individual laser energy pixels arranged adjacent to one another, each of which may have its power level individually controlled. Each laser energy pixel may be independently turned on or off, and the power of each pixel may be independently controlled. Since the resulting pixel-based line or array, in some embodiments, is scanned primarily perpendicular to the major axis of the line, the advancement speed and pixel power density may be limited by roughly the same power and speed limitations as a conventional single spot laser selective melting process. However, since there are multiple spots directly adjacent to one another, the effective process speed may be roughly N times the single pixel speed, where N is the number of available pixels. Also, since each pixel can be individually turned on or off, the effective part resolution and accuracy remain comparable to a single spot system. The system can be operated as a single spot system by turning on only a single pixel or by relying on a single optical fiber extending between a single end cap and a single laser energy source, in which case the effective system speed will be substantially the same as a single spot system.

[0027] In some embodiments, an additive manufacturing system according to the present 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. Combinations of the above ranges may also be suitable. Both larger and smaller ranges than those stated above are contemplated, as the disclosure is not so limited.

[0028] Additionally, in some embodiments, the power output of a laser energy source (e.g., one of the laser energy sources) can be from about 50 W to about 2,000 W (2 kW). For example, the power output of each laser energy source can be from about 100 W to about 1.5 kW, and / or from about 500 W to about 1 kW. Also, the total power output of the multiple laser energy sources can be from about 500 W (0.5 kW) to about 4,000 kW. For example, the total power output can be from about 1 kW to about 2,000 kW, and / or from about 100 kW to about 1,000 kW. Both larger and smaller ranges than those stated above are contemplated, as the disclosure is not so limited.

[0029] In some embodiments, 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 the line array. In other examples, the array may have a non-uniform power density along any of the axes of the array by setting different power output levels for each pixel's associated laser energy source. Also, individual pixels outside the array may be selectively turned off or on to generate an array having a shorter length and / or width. In some embodiments, the power levels of various pixels within the laser energy array may be independently controlled throughout the additive manufacturing process. For example, various pixels may be selectively turned off, on, or operated at intermediate power levels to provide a desired power density within different portions of the array.

[0030] According to some aspects of the present disclosure, the optical path of the incident laser beam after exiting the optical fiber can be important to obtain a uniform line shape on the powder surface. In some embodiments, the optical path of the additive manufacturing system includes a lens array (e.g., one or more microlens arrays) including one or more microlenses, followed by one or more objective lenses. In some embodiments, beams from independent laser energy sources can pass through the same lens array and the same objective lens in the optical assembly.

[0031] In general, the laser energy generated by the laser energy source has a power areal density. In some embodiments, the power areal density of the laser energy transmitted through the optical fiber is 0.1 W / sq micrometer or more, 0.2 W / sq micrometer or more, 0.5 W / sq micrometer or more, 1 W / sq micrometer or more, 1.5 W / sq micrometer or more, 2 W / sq micrometer or more, or more. In some embodiments, the power areal density of the laser energy transmitted through the optical fiber is 3 W / sq micrometer or less, 2 W / sq micrometer or less, 1.5 W / sq micrometer or less, 1 W / sq micrometer or less, 0.5 W / sq micrometer or less, 0.2 W / sq micrometer or less, or less. Combinations of these ranges are possible. For example, in some embodiments, the power areal density of the laser energy transmitted through the optical fiber is 0.1 W / sq micrometer or more and 3 W / sq micrometer or less.

[0032] The power areal density of the laser energy transmitted from the distal end of the optical fiber into the associated end cap can be reduced in some embodiments by increasing the transmission area of ​​the transmitted laser energy in the end cap. For example, according to certain embodiments, the power areal density is reduced by at least a factor of 1.1, at least a factor of 1.2, at least a factor of 1.5, at least a factor of 2, at least a factor of 2.5, at least a factor of 3, at least a factor of 4, at least a factor of 5, at least a factor of 10, or at least a factor of 15, or more, in the end cap relative to the power areal density in the associated optical fiber. The reduction in power areal density can also be 50, 20, 15, 10, or 5 times less than the power areal density in the associated optical fiber. In view of the above, in certain embodiments, the transmission area of ​​the transmitted laser energy, such as the distal surface area of ​​the end cap oriented towards one or more downstream optical elements, may be correspondingly increased by at least 1.1 times, at least 1.2 times, at least 1.5 times, at least 2 times, at least 2.5 times, at least 3 times, at least 4 times, at least 5 times, at least 10 times, or at least 15 times, or more, in the end cap relative to the cross-sectional area in the associated optical fiber (e.g., the cross-sectional area of ​​the core of the optical fiber). The transmission area of ​​the transmitted laser energy in the end cap may also be 50 times or less, 20 times or less, 15 times or less, 10 times or less, or 5 times or less as large as the transmission area (e.g., cross-sectional area) of the associated optical fiber. Combinations of the foregoing ranges are contemplated, including, for example, that the reduction in power areal density in the end cap optically coupled to the optical fiber may be between or equal to 1.1 times or less and 50 times or less than the power areal density in the optical fiber. Correspondingly, the transmission area within the end cap may be between or equal to 1.1 or more and 50 or more times the transmission area of ​​the associated optical fiber, and of course, both ranges greater than and less than those stated above are contemplated as the disclosure is not so limited.

[0033] In some embodiments, the additive manufacturing system may include an optical path disposed in an optical assembly (e.g., an optics box) to generate a line or array of pixels on a build surface using any suitable arrangement and / or combination of different optical elements, which may also be referred to herein as optical components or optical elements. For example, a set of lenses and / or lens arrays may be disposed in series downstream along the optical path relative to one or more associated optical fibers and one or more end caps. Alternatively or additionally, a mirror or mirrors may be added to the beam path downstream of the one or more optical fibers and one or more end caps for beam redirection or folding, and / or a galvo scanner may be added to the beam path for uniaxial scanning of the powder bed. As described in more detail below, in some embodiments, the output from the optical assembly may be directed toward the powder bed using a galvo scanner and then passed through a lens or lens assembly, such as an f-theta lens or a telecentric lens, to minimize beam shape distortion of non-normal incidence on the powder bed.

[0034] In some applications, the output of the optical assembly may be scanned in a primary direction using a galvo scanner, while the entire optical assembly is scanned in a secondary direction perpendicular to the primary direction using a motorized stage actuator. Alternatively, the output of the optical assembly may be scanned in a primary direction with a fast motion using a galvo scanner, while the optics box is scanned in the primary direction and in a secondary direction perpendicular to the primary direction with a slower motion using a motorized stage mounted at a right angle. In other embodiments, the output from the optical assembly may be scanned using only motorized stage movement, without a galvo scanner stage. In further embodiments, the optical assembly may be mounted such that the pixel array output from the optical assembly is oriented at a fixed angle relative to the motion stage, whereby both stages may be actuated to move a line perpendicular to the long axis of the pixel line. Alternatively, this may be accomplished by the output from the optical assembly being scanned using a galvo scanner. In other embodiments, the output from the optical assembly may be dynamically rotated relative to the motion stage during motion. Alternatively, the dynamic rotation of the optics box may be coupled with a galvo scanner that is fixed relative to the optics box. Thus, in view of the above embodiments, it should be understood that the laser pixels may be moved relative to the build surface using any suitable structure, as the disclosure is not limited in this manner.

[0035] In some instances, it may be desirable to reduce the reflection of light from a distal interface, i.e., a surface, of one or more end caps included in the system. Thus, in some embodiments, the end caps of the system may be at least partially (e.g., completely) coated with an anti-reflective coating or other desired coating. The anti-reflective coating may, in some embodiments, reduce the reflection of laser energy from the surface of the end cap. The anti-reflective coating may be applied using sputtering, ion beam sputtering, ion beam magnetron sputtering, evaporation techniques, and / or any other suitable method for applying a coating to a transparent substrate. This may advantageously increase the power areal density of the transmitted laser energy while reducing undesired reflections of the laser energy back toward the laser energy source.

[0036] For clarity, the transmission of laser energy through the optical fiber is generally described throughout. However, with respect to various parameters, such as cross-sectional area, lateral dimension, transmission area, power area density, and / or any other suitable parameters related to the portion of the optical fiber through which the laser energy is transmitted, it should be understood that these parameters refer to either the parameters related to the portion of the optical fiber through which the laser energy is actively transmitted, such as the bare optical fiber and / or the optical fiber core, or a secondary optical laser energy transmitting cladding surrounding the core. In contrast, any surrounding cladding, film, or other material that does not actively transmit the laser energy may not be included in the disclosed scope.

[0037] Specific non-limiting embodiments will be described in more detail with reference to the drawings. It should be understood that the present disclosure is not limited to only the specific embodiments described herein, and that the various systems, components, mechanisms, and methods described with respect to these embodiments can be used individually and / or in any desired combination.

[0038] FIG. 1 is a schematic diagram of one embodiment of an additive manufacturing system 100 including multiple laser energy sources 102 delivering laser energy to an optical assembly 104 positioned within a machine housing 106. For example, the machine housing may define a build volume in which an additive manufacturing process may be performed. In particular, the optical assembly may direct laser energy 108 toward a build surface 110 positioned within the machine housing to selectively melt and bond powder material on the build surface. As described in more detail below, the optical assembly may include multiple optical elements that define an optical path within the optical assembly, which may transform, shape, and / or direct the laser energy within the optical assembly such that the laser energy is directed onto the build surface as an array of laser energy pixels. The optical assembly may be movable within the machine housing 106 to scan the laser energy 108 across the build surface 110 during the manufacturing process, although embodiments in which the optical assembly is stationary relative to the build surface are also contemplated.

[0039] The additive manufacturing system 100 further includes a fiber optic connector 112 positioned between the laser energy sources 102 and the optical assembly 104. As shown, a first plurality of optical fibers 114 extend between the plurality of laser energy sources 102 and the optical fiber connector 112. In particular, each laser energy source 102 is 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 extend between the optical fiber connector 112 and the optical assembly 104. Each optical fiber 116 of the first plurality of optical fibers 114 is coupled to a corresponding 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 optical assembly 104, such that the laser energy 108 can be directed onto the build surface 110 during an additive manufacturing process (i.e., a build process).

[0040] In some examples, the laser energy source 102 and the fiber optic connector 112 may be stationary relative to the machine housing 106. In this manner, the optical fibers 116 of the first plurality of optical fibers 114 may remain substantially stationary throughout the build process, which may help to avoid applying stress to the optical fibers and / or optical fiber connections or couplings that may lead to optical fiber failure. In some embodiments, the optical fibers 120 of the second plurality of optical fibers 118 may be movable relative to the stationary optical fiber connector 112 as they are coupled to the movable optical assembly 104. Although such movement may impart stress to the optical fibers and / or optical fiber connections or couplings, aspects described herein may facilitate quick and easy replacement of the optical fibers 120.

[0041] 2 is a schematic diagram of another embodiment of an additive manufacturing system. Similar to the embodiment described above in connection with FIG. 1, the additive manufacturing system 200 includes a plurality of laser energy sources 202 coupled to an optical assembly 204 within a machine housing 206 via a fiber optic connector 212. A first plurality of optical fibers 214 extend between the laser energy source 202 and the fiber optic connector 212, and a second plurality of optical fibers 218 extend between the fiber optic connector 212 and the optical assembly 204. In particular, each optical fiber 216 of the first plurality of optical fibers is coupled to the laser energy source 202 and to a corresponding optical fiber 220 of the second plurality of optical fibers 218. In the illustrated embodiment, the optical fibers 216 are coupled to the corresponding optical fiber 220 via a fusion splice 222 in the fiber optic connector 212. However, embodiments are also contemplated in which the optical fibers positioned within the connector include end caps as described herein.

[0042] In the illustrated embodiment, the optical fibers 220 of the second plurality of optical fibers 218 are optically coupled to one or more corresponding end caps 250 disposed at the distal ends of the second plurality of optical fibers. The end caps 250 are optically coupled to the optical assembly 204 of the system. For example, an alignment fixture 224 configured to define a desired spatial distribution of the optical fibers and end caps may be used to direct laser energy into the optical assembly. For example, the alignment fixture may comprise a block having a number of v-slots or holes into which each end cap 250 may be positioned and coupled to precisely position the optical fibers and end caps within the system. Additional embodiments and examples of end caps and alignment fixtures are further described below.

[0043] The alignment fixture may be used to align each of the optical fibers 220 of the second plurality of optical fibers 218 with one or more corresponding optical components of the optical assembly 204. As a result, individual alignment operations for each optical fiber 220 (corresponding to each laser energy source 202) may be unnecessary, which may facilitate rapid replacement of the second plurality of optical fibers 218 if necessary or otherwise desired (e.g., if one or more optical fibers 220 fail).

[0044] 2 illustrates exemplary optical elements optically coupled downstream from the second plurality of optical fibers 218 and associated end cap 250. Various optical elements may be included in the optical assembly to direct the laser energy from the second plurality of optical fibers 218 onto the build surface 210 and to form a desired array of laser energy 208 on the build surface. For example, the optical assembly may include beam forming optical elements such as lenses 226 and 228 (which may be individual lenses, lens arrays, and / or combined macro lenses), mirrors 230, and / or any other suitable type of optical element disposed along various optical paths between the end cap and the build surface that may shape and direct the laser energy within the optical assembly. In some embodiments, the lenses 226 and 228 may include one or more of a microlens array and an objective lens. For example, a microlens array may be positioned to collimate the laser energy output from each optical fiber 220 and transform the beam shape of the laser energy, and an objective lens may be positioned to define the focal length of the combined array of laser energy and function to demagnify or magnify the output from the microlens array. In some examples, this demagnification or magnification may be used to adjust the spacing of the laser energy pixels in the array of laser energy formed on the build surface. For example, the objective lens may be positioned to demagnify the array such that there is no spacing between adjacent pixels. It should also be understood that the present disclosure is not limited to a particular shape, spacing, and / or arrangement of the laser energy pixels in the array of laser energy 208 formed on the build surface. For example, the array may be a rectangular array having regularly spaced pixels of laser energy, or the array may be an irregular shape with non-uniform spacing between the pixels.

[0045] The optical fibers described herein have a transverse dimension and an axial dimension, according to certain embodiments. Generally, the axial dimension of the optical fiber extends along the entire length of the optical fiber. Generally, the transverse dimension of the optical fiber lies in a cross-section of the fiber perpendicular to the axial dimension. The axial dimension of the optical fiber may be substantially longer (e.g., 100 times, 1000 times, 10,000 times, 100,000 times, or more than 100,000 times) than the maximum transverse dimension (e.g., diameter) of the optical fiber, according to certain embodiments. In some embodiments, the laser energy is transmitted through the optical fiber along the axial dimension of the optical fiber. For example, in FIG. 2, the laser energy transmitted from the laser energy source 202 is transmitted through the optical fiber 216 along the axial dimension of the fiber 216. In some examples, the angle between the direction of transmission of the laser energy and the axial dimension in the optical fiber is 3 degrees or less, 2 degrees or less, 1.5 degrees or less, 1 degree or less, 0.5 degrees or less, 0.2 degrees or less, or less.

[0046] In some examples, the optical fiber has a maximum transverse dimension (e.g., diameter) perpendicular to the axial direction of the optical fiber. For example, according to certain embodiments, the maximum transverse dimension of the optical fiber is 30 microns or more, 50 microns, 75 microns, 100 microns, 125 microns, 150 microns, or more. According to certain embodiments, the maximum transverse dimension of the optical fiber is 200 microns or less, 175 microns or less, 150 microns or less, 125 microns or less, 100 microns or less, 75 microns or less, 50 microns or less, or less. Combinations of these ranges are possible. For example, according to certain embodiments, the maximum transverse dimension of the optical fiber is 30 microns or more and 200 microns or less. Of course, optical fibers having maximum transverse dimensions greater than or less than the above-mentioned ranges are also contemplated, as the disclosure is not so limited.

[0047] According to certain embodiments, the fiber comprises a core through which the laser energy is transmitted. In some examples, the maximum transverse dimension of the optical fiber core (e.g., the maximum core diameter of the optical fiber) is 5 microns or more, 10 microns, 20 microns, 25 microns, 35 microns, 40 microns, or more. According to certain embodiments, the maximum transverse dimension of the optical fiber core is 60 microns or less, 55 microns, 50 microns, 45 microns, 40 microns, 35 microns, or less. Combinations of these ranges are possible. For example, according to certain embodiments, the maximum transverse dimension of the optical fiber is 5 microns or more and 60 microns or less. Of course, optical fibers comprising cores having larger and smaller maximum transverse dimensions than those mentioned above are also contemplated, as the disclosure is not limited in this manner.

[0048] The lateral dimensions of the core can present challenges in coupling light (e.g., laser energy) into and out of an optical fiber because most of the light coupled into the optical fiber must be focused onto a spot smaller than the lateral dimensions of the fiber (e.g., core diameter), and the light may need to be focused into the optical fiber at a divergence angle smaller than the divergence angle of the optical fiber. This may require precise alignment of the optical fiber in the additive manufacturing system because light that is not properly focused into the core of the optical fiber may leak into the cladding of the optical fiber surrounding the core, which may lead to undesirable loss of power transfer efficiency and / or heating of the optical fiber.

[0049] According to certain embodiments, the divergence angle of the light leaving the core of the optical fiber can be between about 0.3 degrees and about 1.5 degrees. In some embodiments, the divergence angle of the light leaving the core is 0.2 degrees or more, 0.25 degrees or more, 0.3 degrees or more, 0.35 degrees or more, 0.4 degrees or more, 0.5 degrees or more, or more. In some embodiments, the divergence angle of the light leaving the core is 2 degrees or less, 1.8 degrees or less, 1.5 degrees or less, 1.3 degrees or less, 1.1 degrees or less, or less. Combinations of these ranges are possible. For example, in some embodiments, the divergence angle of the light leaving the core is 0.2 degrees or more and 2 degrees or less. Of course, optical fibers with divergence angles greater and less than those described above are also contemplated, as the disclosure is not limited in this manner.

[0050] 3A-3E show perspective views of example end caps having different shapes that may be coupled to an optical fiber for use in an additive manufacturing system, according to certain embodiments, although it should be understood that end caps having any suitable size and / or shape may be used to provide the desired reduced power areal density for laser energy transmission, as the disclosure is not limited in this manner.

[0051] In Figure 3A, end cap 250 is a cylindrical end cap that is disposed on and optically coupled to a distal end 260 of optical fiber 220. For example, optical fiber 220 may be fusion coupled to end cap 250 at distal end 260. In the example of Figure 3A, end cap 250 is a cylindrical end cap. According to certain embodiments, cylindrical end caps may aid in the alignment of an associated optical fiber. For example, in some embodiments, cylindrical end caps may be more easily aligned using an alignment fixture, as described in further detail below.

[0052] In FIG. 3A, end cap 250 further comprises a distal surface 262 in some embodiments. The surface area of ​​the distal surface of the end cap may be greater than the cross-sectional area of ​​the optical fiber. For example, as shown in FIG. 3A, distal surface 262 of end cap 250 has a surface area greater than the cross-sectional area of ​​distal end 260 of optical fiber 220. As discussed above, this may provide an increased transmission area within the end cap for laser energy transmitted from a laser energy source. For example, laser energy transmitted from a laser energy source through optical fiber 220 into end cap 250 may diverge within end cap 250, resulting in an increased transmission area for laser energy transmission.

[0053] In various embodiments described herein, the optical fiber may have a cross-sectional area of ​​25 square microns or more, 50 square microns or more, 100 square microns or more, 200 square microns or more, 500 square microns or more, 1,000 square microns or more, 2,000 square microns or more, 5,000 square microns or more, 10,000 square microns or more, or more than that. In some embodiments, the cross-sectional area may be 25,000 square microns or less, 10,000 square microns or less, 5,000 square microns or less, 2,000 square microns or less, 1,000 square microns or less, 500 square microns or less, 200 square microns or less, 100 square microns or less, 50 square microns or less, or less than that. Combinations of these ranges are possible. For example, in some embodiments, the cross-sectional area of ​​the optical fiber may be 25 square microns or more and 25,000 square microns or less. Of course, areas smaller and larger than those stated above are also contemplated as the disclosure is not limited in this manner.

[0054] In various embodiments described herein, the distal surface of the end cap oriented toward a downstream optical element optically coupled to the end cap may have a surface area of ​​0.01 mm2 or more, 0.05 mm2 or more, 0.1 mm2 or more, 0.5 mm2 or more, 1 mm2 or more, 2 mm2 or more, 5 mm2 or more, or more. In some embodiments, the distal surface of the end cap has a surface area of ​​20 mm2 or less, 15 mm2 or less, 10 mm2 or less, 5 mm2 or less, 1 mm2 or less, 0.5 mm2 or less, 0.1 mm2 or less, or less. Combinations of these ranges are possible. For example, in some embodiments, the distal surface of the end cap has a surface area of ​​0.01 mm2 or more and 20 mm2 or less. Of course, areas smaller and larger than those described above are also contemplated as the disclosure is not limited in this manner.

[0055] The end caps disclosed herein may have a maximum transverse dimension (e.g., diameter, or width measured parallel to the transverse dimension of the distal end of the optical fiber disposed in the end cap) according to certain embodiments. In some embodiments, the maximum transverse dimension of the end cap is 125 microns or more, 250 microns or more, 500 microns or more, 750 microns or more, 1 mm or more, 1.5 mm or more, or more. In some embodiments, the maximum transverse dimension of the end cap is 2 mm or less, 1.5 mm or less, 1 mm or less, 750 microns or less, 500 microns or less, 250 microns or less, or less. Combinations of these ranges are possible. For example, in some embodiments, the maximum transverse dimension of the end cap is 125 microns or more and 2 mm or less, although larger and smaller maximum transverse dimensions than those stated above are also contemplated.

[0056] The various end caps disclosed may have any suitable length (e.g., the length extending axially from the distal end of the optical fiber disposed in the end cap). In some embodiments, the end cap has a length of 100 microns or more, 200 microns or more, 500 microns or more, 1 mm or more, 2 mm or more, 3 mm or more, or more. In some embodiments, the end cap has a length of 5 mm or less, 4 mm or less, 3 mm or less, 2 mm or less, 1 mm or less, 500 microns or less, or less. Combinations of these ranges are possible. For example, in some embodiments, the end cap may have a length of 100 microns or more and 5 mm or less. Of course, lengths greater and less than those stated above are contemplated.

[0057] FIG. 3B illustrates another embodiment of an optical fiber having an end cap similar to FIG. 3A, except that in this embodiment, the end cap 250 disposed at and optically coupled to the distal end of the optical fiber 220 is a prism. Any suitable prism may be used. For example, the prism in FIG. 3B is a right-angle prism. However, any suitable size and shape prism may be used as the disclosure is not limited in this manner. In some embodiments, the use of prisms as end caps is advantageous. For example, in some embodiments, the prisms may be mosaic, which may facilitate alignment of the end caps into an array. According to certain embodiments, each end cap of one or more end caps optically coupled to a plurality of optical fibers is a prism.

[0058] In the above embodiment, each optical fiber is optically coupled to a separate end cap. However, in some embodiments, two or more optical fibers of the plurality of optical fibers may be coupled to a single end cap. In some embodiments, optically coupling two or more optical fibers to an end cap may advantageously simplify alignment of the optical fibers, for example, by using the end cap to enforce the relative position of the two or more optical fibers. FIG. 3C illustrates one such embodiment. In the illustrated embodiment, the distal ends 260 of two optical fibers 220 are coupled to an end cap 250. Although in the illustrated embodiment, the end cap 250 is coupled to two fibers, in some embodiments, the number of optical fibers coupled to an end cap in such an embodiment may be two, at least five, at least ten, and / or any other suitable number of optical fibers. In some embodiments, the number of optical fibers coupled to an end cap may be up to 50, 40, 30, 20, 10, and / or any other suitable number of optical fibers. Combinations of these ranges are possible. In some embodiments, all of the optical fibers in an additive manufacturing system are coupled to a single end cap, while in other embodiments, multiple groups of optical fibers connected to individual end caps may be used.

[0059] FIG. 3D illustrates another exemplary end cap for an optical fiber 220, according to certain embodiments. In this embodiment, the end cap 250 is a microlens (e.g., a convex microlens) disposed on and optically coupled to the distal end 260 of the optical fiber 220. In this embodiment, the end cap has the same maximum lateral dimension as the distal end 260 of the optical fiber 220, but the surface area of ​​the distal surface 262 of the end cap 250 is larger than the cross-sectional area of ​​the distal end 260 of the optical fiber 220 (e.g., the transmission area of ​​the core of the optical fiber). In this embodiment, the end cap may act as a microlens and advantageously focus the transmitted laser energy to a desired focal point as it exits the optical fiber. This may reduce the need for subsequent focusing using a microlens array and other optical components disposed downstream from the optical fiber. Additionally, the curvature of the distal surface 262 may reduce back reflection of the laser energy in the upstream axial direction toward the associated laser source. This may advantageously reduce the portion of the reflected laser energy that reaches the laser energy source.

[0060] While the microlens end cap shown in FIG. 3D has the same maximum lateral dimension as an optical fiber, other variations of end caps with microlenses are possible. For example, FIG. 3E shows an exemplary end cap 250 disposed on and optically coupled to a distal end of an optical fiber 220, the end cap comprising a proximal cylindrical portion and a distal convex microlens portion. Similar to the embodiment described in FIG. 3A-3D, the distal surface 262 of the end cap 250, which is the exterior surface of the distal convex microlens portion of the end cap 250, has a surface area greater than the cross-sectional area of ​​the distal end 260 of the optical fiber 220. As above, such a structure may increase the transmission area of ​​the transmitted laser energy and may focus the transmitted laser energy leaving the end cap. FIG. 3F shows an embodiment in which the distal ends 260 of two optical fibers 220 are coupled to the end cap 250. In FIG. 3F, the end cap 250 is similar to the end cap 250 of FIG. 3B, with the body of the end cap optically coupled to multiple optical fibers. However, the end cap also includes a distal surface 262 oriented away from the optical fibers that includes two convex microlens portions 264 similar to the convex microlens portions of the end cap 250 shown in FIG. 3E. Thus, in some embodiments, an end cap includes multiple microlens portions, each aligned with a corresponding one of the multiple optical fibers. In some embodiments, the multiple microlens portions may act as individual microlenses. For example, the microlens portions may form an array of microlenses distributed along the distal surface of the end cap oriented away from the optical fibers. As a non-limiting example, the end cap 250 of FIG. 3F includes two convex microlens portions 264. However, in other embodiments, the number of convex microlens portions coupled to an end cap in such an embodiment may be two, at least five, at least ten, at least twenty, and / or any other suitable number of convex microlens portions.In some embodiments, the number of convex microlens portions in an end cap is 50 or less, 40, 30, 20, 10, and / or any other suitable number of convex microlens portions. Combinations of these ranges are possible, including, for example, an end cap having between or equal to 2 and 50 microlens portions formed thereon, which are aligned with a corresponding number of optical fibers. As discussed above, in some embodiments, each optical fiber in the additive manufacturing system is optically coupled to a single convex microlens portion. For example, optical fiber 220 in FIG. 3E is optically coupled to a convex microlens portion of end cap 250 formed by distal end 262 of end cap 250. In some embodiments, all optical fibers in the additive manufacturing system are coupled to different convex microlens portions. For example, referring again to FIG. 3F, each optical fiber 220 is optically coupled to a different convex microlens portion.

[0061] 3A-3F depict possible end cap configurations, it should be understood that these are non-limiting and that any suitable end cap geometry may be used. Additionally, embodiments are contemplated in which a combination of different types of end caps are used within a single system.

[0062] That said, in some embodiments, each end cap of the one or more end caps is selected from the group consisting of a block, a cylinder, a prism, and a microlens disposed on and optically coupled to a distal end of one or more associated optical fibers.

[0063] 4A-4B show front views of an exemplary alignment fixture 224 and end cap 250 according to certain embodiments. In the embodiment illustrated in FIG. 4A, the alignment fixture includes a plurality of v-grooves formed in a first portion of the fixture. Each of the v-grooves includes two opposing angled surfaces that are inclined inwardly such that an optical fiber and / or end cap 250 positioned in a given v-groove is disposed against the inwardly angled surface of the associated v-groove. The v-grooves may be parallel to each other such that they extend in an axial direction oriented into the plane of the figure. This may help to align the optical fiber and end cap with the desired transmission direction. Additionally, by appropriately controlling the width and depth of the V-grooves and the corresponding lateral dimensions of the optical fiber and / or end cap, the optical fiber and / or end cap may be easily positioned in both horizontal and vertical directions that may be perpendicular to the axial length of the optical fiber extending into the plane of the figure shown.

[0064] In the illustrated embodiment, the optical fibers and / or end caps 250 may be held in the associated v-grooves 280 by a second portion of the alignment fixture 224 disposed against a surface of the optical fibers and / or end caps opposite the first portion of the alignment fixture in which the v-grooves are formed. The first and second portions of the alignment fixture may be coupled together in any suitable manner, including but not limited to adhesives, fasteners, mechanical interlocking mechanisms, welding, and / or any other suitable type of connection. In the illustrated embodiment, the v-grooves are formed in a single portion of the alignment fixture and are uniformly spaced from one another such that the end caps positioned in the v-grooves are positioned in a linear array. However, as shown in FIG. 4B, the alignment fixture may include v-grooves formed in multiple portions of the alignment fixture. For example, a first set of optical fibers and / or end caps may be positioned in a first set of v-grooves formed in a first portion of the alignment fixture. The first set of optical fibers and / or end caps may be held in the first set of v-grooves with the first set of optical fibers and / or end caps disposed therebetween by a second portion of the alignment fixture disposed thereon. A second set of v-grooves may be formed in the second portion of the alignment fixture opposite the first portion of the alignment fixture to receive a second set of optical fibers and / or end caps disposed therein. This layered arrangement may be continued through any number of layers to provide a desired number of rows in the two-dimensional array, although in the illustrated embodiment, a third portion of the alignment fixture is disposed over the second portion of the alignment fixture with the second set of optical fibers and / or end caps disposed therebetween.

[0065] In the above embodiments, the end caps may be aligned in any suitable orientation and / or position within the alignment fixture. For example, the end caps of the linear array of FIG. 4A may be regularly spaced or irregularly spaced depending on the desired application. Similarly, the two-dimensional array of FIG. 4B may include a plurality of regularly and / or irregularly spaced optical fibers and / or end caps. The two-dimensional array may have any suitable configuration. For example, the two-dimensional array may be a square array, a rectangular array, a hexagonal array, a monoclinic array, and / or any other suitable layout.

[0066] In certain embodiments, multiple optical fibers are optically coupled to one or more end caps. In certain applications, it may be desirable to position the distal-most end of the one or more end caps within a predetermined range of a desired axial location. This may allow the end cap to be properly positioned relative to other optical elements downstream from the end cap, thereby providing desired optical properties and / or control of the laser energy delivered onto the build surface of the additive manufacturing system. In some such embodiments, the distal end of each of the one or more end caps may be positioned within 20 microns, 15 microns, 12 microns, 10 microns, 5 microns, 2 microns, or any other suitable distance of a predetermined axial location in the system. In some embodiments, it may also be desirable to maintain the uniformity of the length of the one or more end caps within a predetermined tolerance of the target length. This tolerance on the length of the one or more end caps may be the same as or less than the ranges described above for the overall tolerance of the axial location of the distal-most surface of the one or more end caps. Of course, while tolerance ranges related to the positioning and length of the end caps are set forth above, it should be understood that any suitable tolerances greater than or less than those set forth above are also contemplated, as the disclosure is not limited in this manner.

[0067] FIG. 5 illustrates a top view of a portion of an alignment fixture 224 having two end caps 250 and corresponding optical fibers 220, according to certain embodiments. In this embodiment, the end caps 250 are disposed within and supported by the v-grooves 280. In some embodiments, the optical fibers may also be disposed within individual corresponding v-grooves, not shown, that are aligned with the v-grooves associated with the end caps, which may help support the portion of the optical fiber connected to the end cap within the alignment fixture. As discussed above, it may be desirable to precisely position a portion of the distal end of one or more end caps relative to a predetermined axial location. In one such embodiment, a distal surface 282 of the end cap may be disposed against a proximal surface of one or more transmissive structures, such as a block, sheet, or other structure including a flat proximal surface, disposed in the distal portion of the alignment fixture. The proximal surface of one or more permeable structures can be precisely positioned such that by placing the distal ends of one or more end caps against this surface, the distal ends of the end caps can be precisely and easily aligned with one another at a predetermined axial position.

[0068] In another embodiment, alignment of the distal ends of one or more end caps of the system at a predetermined axial location may be provided by alignment of a proximal surface of the end cap (e.g., a surface of the end cap oriented in an upstream direction relative to the direction of transmission of laser energy through the optical fiber) to a support structure. For example, FIG. 6 shows a view of a portion of an alignment fixture 224 with an optical fiber 220 disposed within an illustrated v-groove 280, but with an end cap 250 extending out beyond the v-groove of the alignment fixture 224. A proximal surface 288 of the end cap may be disposed on a distally oriented surface 286 of the portion of the alignment fixture in which the v-groove is formed, or on other suitable structure. Precise control of the position and uniformity of this support surface may allow the distal surfaces 282 of the end caps to be easily and accurately aligned with one another at a predetermined axial location. In such an embodiment, alignment of the most distal ends of one or more end caps may also depend on the relative uniformity of the lengths of the individual end caps.

[0069] 7 illustrates yet another embodiment of a portion of the alignment fixture 224 with the optical fiber 220 and end cap 250 disposed within corresponding v-grooves 280. As above, the distal surface 282 of the end cap may be disposed against the proximal surface of the transmissive structure 284 to align the distal ends of the end caps relative to one another at a predetermined axial location, although in this embodiment the end cap may be received in a correspondingly sized and shaped recess formed in the transmissive structure.

[0070] In the above embodiments, specific structures and v-grooves have been shown for positioning and orienting the optical fiber and end cap within the alignment fixture. However, it should be understood that other suitable types of alignment mechanisms may also be used. For example, the end cap may be received in one or more corresponding holes that may extend partially or completely through the corresponding portion of the alignment fixture. Other suitable types of alignment mechanisms may include, but are not limited to, v-grooves, holes, optical wedges, and optical blocks. Additionally, the end cap may be aligned with the desired axial location in these various types of alignment fixtures using any suitable structures, including the structures shown in the above embodiments, as well as other structures using v-grooves, holes, optical wedges, optical blocks, and / or any other alignment mechanisms that can properly position the distal end of the end cap, as the disclosure is not limited in this manner.

[0071] FIG. 8 illustrates the transmission of laser energy from a linear array of end caps to a linear array of microlenses, according to certain embodiments. Similar to FIGS. 5-7, FIG. 8 illustrates a top view of a portion of alignment fixture 224, end caps 250, and optical fibers 220, according to certain embodiments. In this embodiment, similar to FIG. 5, end caps 250 are aligned in v-groove 280 against proximal surface 284 of transmissive structure 282, such that the distal-most end of end cap 250 is aligned with a desired axial location. However, any suitable alignment fixture having one or more optical fibers and end caps positioned therein may be used. In this embodiment, laser energy 208 transmitted from end caps 250 is directed to a plurality of individual microlenses 276 arranged in an array aligned with the array of end caps. FIG. 9 is similar to FIG. 8. However, in this embodiment, microlenses 276 are provided in the form of a microlens array in which the individual microlenses are formed of a unitary structure. FIG. 10 is similar to FIGS. 8-9. However, in this embodiment, laser energy 208 transmitted from the distal surface of one or more end caps is directed onto a macro lens 278 that can be used to focus the laser energy transmitted from the one or more end caps.

[0072] In the above embodiments, the transmitted laser energy is illustrated as being incident on a microlens or a macrolens. However, it should be understood that any suitable combination of optical elements downstream from the optical fiber and associated end cap may be used as the disclosure is not so limited. For example, both macrolenses and microlenses may be used in combination with one another and downstream relative to the optical fiber and end cap. Thus, the illustrated embodiments should not be construed as limiting the use of the disclosed optical fibers and end caps to any particular system configuration.

[0073] The following examples are intended to illustrate certain embodiments of the present disclosure, but do not exemplify the full scope of the disclosure.

[0074] Although several embodiments of the present disclosure have been described and illustrated herein, those skilled in the art will readily envision various other means and / or structures for performing the functions and / or obtaining one or more of the results and / or advantages described herein, and each such variation and / or modification is deemed to be within the scope of the present disclosure. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are intended to be exemplary, and that the actual parameters, dimensions, materials, and / or configurations will depend on the specific application or applications for which the teachings of the present disclosure are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the present disclosure described herein. Thus, it should be understood that the foregoing embodiments are presented by way of example only, and that the present disclosure may be practiced otherwise than as specifically described and claimed, within the scope of the appended claims and equivalents thereof. The present disclosure is directed to each and every feature, system, article, material, and / or method described herein. Additionally, any combination of two or more such features, systems, articles, materials, and / or methods is included within the scope of the present disclosure, if such features, systems, articles, materials, and / or methods are not mutually inconsistent.

[0075] The indefinite articles "a" and "an," as used in the specification and claims, unless expressly stated to the contrary, should be understood to mean "at least one."

[0076] The phrase "and / or" as used in the specification and claims should be understood to mean "one or both" of the elements so conjoined, i.e., elements that are present conjunctively in some cases and disjunctively in other cases. Unless expressly stated to the contrary, other elements may optionally be present other than the elements specifically identified by the "and / or" clause, whether related or unrelated to those specifically identified elements. Thus, as a non-limiting example, when used in connection with open-ended language such as "comprising," "A and / or B" may refer in one embodiment to A without B (optionally including elements other than B), in another embodiment to B without A (optionally including elements other than A), in yet another embodiment to both A and B (optionally including other elements), and so forth.

[0077] As used herein and in the claims, "or" should be understood to have the same meaning as "and / or" as defined above. For example, when separating listed items, "or" or "and / or" shall be interpreted as inclusive, i.e., including at least one of the several or listed elements, but also including more than one, and optionally including additional unlisted items. Only terms expressly indicating otherwise, such as "only one of" or "only one of," or, when used in the claims, "consisting of," refer to the inclusion of only one of the several or listed elements. In general, the term "or" as used herein shall only be interpreted as indicating exclusive alternatives (i.e., "one or the other, but not both") when preceded by a term of exclusivity, such as "either," "one of," "only one of," or "only one of." "Consisting essentially of," when used in the claims, shall have its ordinary meaning as used in the field of patent law.

[0078] As used herein and in the claims, the phrase "at least one" referring to one or more listed elements should be understood to mean at least one element selected from any one or more of the elements in that list of elements, but not necessarily including at least one of each and every element specifically listed in that list of elements, and not excluding any combinations of elements in that list of elements. This definition also allows for the optional presence of elements other than those specifically identified in the list of elements to which the phrase "at least one" refers, whether related or unrelated to the specifically identified elements. Thus, as a non-limiting example, "at least one of A and B" (or, equivalently, "at least one of A or B," or, equivalently, "at least one of A and / or B") can refer in one embodiment to at least one, and optionally more than one, A, with no B (and optionally including elements other than B); in another embodiment to at least one, and optionally more than one, B, with no A (and optionally including elements other than A); in yet another embodiment to at least one, and optionally more than one, A and at least one, and optionally more than one, B (and optionally including other elements); and so forth.

[0079] Some embodiments may be embodied as a method, various examples of which have been described. The acts performed as part of the method may be ordered in any suitable manner. Thus, even if acts are specifically shown in the embodiments described above as being performed sequentially, embodiments may be constructed in which the acts are performed in an order different from that illustrated, which may include different (e.g., more or fewer) acts than those described and / or may involve performing some acts simultaneously.

[0080] The use of sequence terms such as "first," "second," "third," etc. in the claims to modify elements does not, in and of itself, imply any priority, precedence, or order of one element over another, or the chronological order in which acts of a method are performed, but is used solely as a marker to distinguish one element having a particular name from another element having the same name (apart from the use of sequence terms) in order to distinguish the elements.

[0081] In the claims and in the above specification, all transitional phrases such as "comprising," "including," "carrying," "having," "containing," "accompanying," "holding," and the like, are to be understood as open-ended, i.e., meaning including but not limited to. As set forth in the United States Manual of Patent Examining Procedures, Chapter 2111.03, only the transitional phrases "consisting of" and "consisting essentially of" are to be closed or semi-closed transitional phrases, respectively.

Claims

1. A laser energy source, an optical assembly configured to direct laser energy from the laser energy source onto a build surface to form a laser energy spot on the build surface, an optical fiber optically coupled to the laser energy source, and an end cap disposed at and optically coupled to a distal end of the optical fiber, wherein a surface area of a distal surface of the end cap is larger than a cross-sectional area of the distal end of the optical fiber, the end cap is optically coupled to the optical assembly, and the end cap has at least one microlens configured to focus the laser energy from the laser energy source onto the build surface to melt material on the build surface, an additive manufacturing system.

2. The additive manufacturing system of claim 1, wherein the end cap is configured to reduce a first power area density of the laser energy transmitted from the distal end of the optical fiber to one tenth or less than one tenth of a second power area density within the optical fiber within the end cap.

3. The additive manufacturing system of claim 1, wherein the end cap is configured to increase a transmission area of the laser energy transmitted from the laser energy source to reduce a power area density of the transmitted laser energy.

4. A laser energy source, an optical assembly configured to direct laser energy from the laser energy source onto a build surface to form a laser energy spot on the build surface, an optical fiber optically coupled to the laser energy source, and an end cap disposed at and optically coupled to a distal end of the optical fiber, wherein the end cap is configured to increase a transmission area of the laser energy transmitted from the laser energy source to reduce a power area density of the transmitted laser energy, and the end cap has at least one microlens configured to focus the laser energy from the laser energy source onto the build surface to melt material on the build surface, an additive manufacturing system. **Claim 5**: The end cap is configured to increase the transmission area of the laser energy transmitted from the laser energy source and to reduce the power area density of the transmitted laser energy to one tenth or less in the end cap with respect to a second power area density in the optical fiber. The additive manufacturing system according to claim 4. **Claim 6** The surface area of the distal surface of the end cap is larger than the cross-sectional area of the distal end of the optical fiber. The additive manufacturing system according to claim 4 or 5. **Claim 7** The distal end of the optical fiber is fusion-bonded to the end cap. The additive manufacturing system according to claim 1 or 4. **Claim 8** The additive manufacturing system according to claim 1 or 4, further comprising one or more lenses disposed downstream of the end cap and optically coupled to the end cap. **Claim 9** The end cap is selected from the group consisting of a cylinder, a prism, and a microlens. The additive manufacturing system according to claim 1 or 4. **Claim 10** The axial position of the distal end of the end cap is within 20 microns of a predetermined axial position. The additive manufacturing system according to claim 1 or 4. **Claim 11** Transmitting laser energy along the axial dimension of the optical fiber from a laser energy source; Reducing the power area density of the transmitted laser energy by increasing the transmission area of the transmitted laser energy within an end cap disposed on and optically coupled to the optical fiber, the end cap having at least one microlens configured to focus the laser energy from the laser energy source onto a build surface to melt material on the build surface; Directing the laser energy output from the end cap onto the build surface to form a laser energy spot on the build surface; An additive manufacturing method comprising: **Claim 12** The surface area of the distal surface of the end cap is larger than the cross-sectional area of the distal end of the optical fiber. The method according to claim 11. **Claim 13** The method of claim 11, wherein the distal end of the optical fiber is fusion bonded to the end cap.

14. The method of claim 11, further comprising one or more lenses disposed downstream of the end cap and optically coupled to the end cap.

15. The method of claim 11, wherein the end cap is selected from the group consisting of a cylinder, a prism, and a microlens.

16. The method of claim 11, wherein an axial position of the distal end of the end cap is within 20 microns of a predetermined axial position.

17. A plurality of laser energy sources; an optical assembly configured to direct laser energy from the plurality of laser energy sources onto a build surface to form an array of laser energy spots on the build surface; a plurality of optical fibers optically coupled to the plurality of laser energy sources; one or more end caps disposed at and optically coupled to a distal end of each optical fiber, wherein each end cap of the one or more end caps has a surface area of a distal surface that is larger than a cross-sectional area of the distal end of the optical fiber disposed therein, and each end cap of the one or more end caps has at least one microlens configured to focus the laser energy exiting the distal end of the optical fiber disposed thereon onto the build surface to melt material on the build surface; wherein the plurality of optical fibers form an array; An additive manufacturing system.

18. The additive manufacturing system of claim 17, wherein the one or more end caps are configured to reduce a first power area density of the laser energy transmitted from the distal end of each optical fiber to one tenth or more lower than a second power area density within the one or more end caps with respect to the second power area density within each optical fiber.

19. The additive manufacturing system of claim 17, wherein the one or more end caps are configured to increase a transmission area of the laser energy transmitted from the plurality of laser energy sources to reduce a power area density of the transmitted laser energy.

20. The distal end of each optical fiber is fusion-bonded to the one or more end caps, the additive manufacturing system according to any one of claims 17 to 19.

21. The additive manufacturing system according to any one of claims 17 to 19, further comprising one or more lenses disposed downstream of the one or more end caps and optically coupled to the one or more end caps.

22. The additive manufacturing system according to any one of claims 17 to 19, further comprising an alignment and fixing jig configured to position and orient the one or more end caps.

23. The additive manufacturing system according to claim 22, wherein the alignment and fixing jig comprises a V-groove.

24. The additive manufacturing system according to any one of claims 17 to 19, wherein the array is a linear array.

25. The additive manufacturing system according to any one of claims 17 to 19, wherein the array is a two-dimensional array.

26. The additive manufacturing system according to any one of claims 17 to 19, wherein two or more of the plurality of optical fibers are optically coupled to a single end cap of the one or more end caps.

27. The additive manufacturing system according to any one of claims 17 to 19, wherein each optical fiber of the plurality of optical fibers is optically coupled to an individual end cap of the one or more end caps.

28. The additive manufacturing system according to any one of claims 17 to 19, wherein each end cap of the one or more end caps is selected from the group consisting of a cylinder, a prism, and a microlens.

29. The additive manufacturing system according to any one of claims 17 to 19, wherein the axial position of the distal end of each end cap of the plurality of end caps is within 20 microns of a predetermined axial position.

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