ADDITIVE MANUFACTURING

RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Patent Application Serial No. 62/515,323, filed June 5, 2017 and entitled "SYSTEMS AND METHODS FOR ALIGNING ANISOTROPIC PARTICLES FOR ADDITIVE MANUFACTURING," which is hereby incorporated by reference in its entirety.

BACKGROUND

[0002] Additive manufacturing (sometimes referred to as 3D printing) can be used to fabricate complex three-dimensional structures using materials such as polymers, metals, and ceramics. The printing of polymers can be accomplished by extrusion-based direct-write techniques or by stereolithography (SLA) based photo-polymerization techniques, for example. Printed polymers can be lightweight but relatively weak. Thus, 3D printing is now moving toward manufacturing fiber-reinforced polymer composites.

SUMMARY

[0003] One aspect of the subject matter described in this disclosure can be implemented in a system for additive manufacturing. The system can include a reservoir configured to contain a precursor material comprising a matrix material and a plurality of anisotropic particles. The system can include a build plate configured to move towards a lower surface of the reservoir to allow the build plate to be at least partially submerged in the precursor material. The system can include an actuator configured to cause relative motion between the reservoir and the build plate to expose the precursor material to a shear force causing a portion of the plurality of anisotropic particles to become oriented in a selected alignment direction based on a direction of the shear force. The system can include a radiation source configured to emit radiation towards the reservoir to solidify a portion of the precursor material.

[0004] In some implementations, the actuator can be configured to cause rotational motion of at least one of the reservoir and the build plate. In some implementations, the actuator can be configured to cause translational motion of at least one of the reservoir and the build plate. In some implementations, the system can include a rail coupled to the reservoir. The reservoir can be configured to move along the rail. In some implementations, the actuator can be coupled to the reservoir and configured to move the reservoir along the rail. In some implementations, the system can include a controllable XY stage including the actuator. In some implementations, the actuator can be coupled to the build plate and configured to move the build plate within the precursor material.

[0005] In some implementations, the actuator can be configured to cause relative motion between the reservoir and the build plate in a first direction to cause the portion of the plurality of anisotropic particles to become oriented along the first direction. The radiation source can be configured to emit the radiation towards the reservoir in a first pattern corresponding to a shape of a first region of a layer of a part to solidify the portion of the precursor material corresponding to the first region of the layer.

[0006] In some implementations, the actuator can be configured to cause relative motion between the reservoir and the build plate in a second direction to cause a second portion of the plurality of anisotropic particles to become oriented along the second direction. The radiation source can be configured to emit the radiation towards the reservoir in a second pattern corresponding to a shape of a second region of the layer of the part to solidify the portion of the precursor material corresponding to the second region of the layer. In some implementations, the first direction is different from the second direction. In some implementations, the first region and the second region are non-overlapping.

[0007] In some implementations, the actuator can be configured to cause relative motion between the reservoir and the build plate in a second direction to cause a second portion of the plurality of anisotropic particles to become oriented along the second direction. The radiation source can be configured to emit the radiation towards the reservoir in a second pattern corresponding to a shape of a region of a subsequent layer of the part to solidify the portion of the precursor material corresponding to the region of the subsequent layer.

[0008] In some implementations, the actuator can be configured to cause relative motion between the reservoir and the build plate in a series of directions to cause the portion of the plurality of anisotropic particles to become oriented along a first direction. The radiation source can be configured to emit the radiation towards the reservoir in a first pattern corresponding to a shape of a first region of a layer of a part to solidify the portion of the precursor material corresponding to the first region of the layer.

[0009] In some implementations, the reservoir can include a surface that is transparent to the radiation emitted by the radiation source. In some implementations, the radiation source can be configured to emit ultraviolet radiation.

[0010] Another aspect of the subject matter described in this disclosure can be implemented in a method of producing a composite part. The method can include providing a precursor material including a matrix material and a plurality of anisotropic particles. The method can include exposing the precursor material to a first shear force to cause at least a first portion of the plurality of anisotropic particles to become oriented in a first alignment direction based on a direction of the first shear force. The method can include solidifying a first region of the precursor material with the first portion of the plurality of anisotropic particles oriented in the first alignment direction. The method can include exposing the precursor material to a second shear force to cause at least a second portion of the plurality of anisotropic particles to become oriented in a second alignment direction based on a direction of the second shear force. The method can include solidifying a second region of the precursor material with the second portion of the plurality of anisotropic particles oriented in the second alignment direction.

[0011] In some implementations, the plurality of anisotropic particles can include fibers. In some implementations, the matrix material can include a polymer. In some implementations, the first alignment direction can be different from the second alignment direction.

[0012] In some implementations, the solidified first region of the precursor material can adhere to a build plate to form a first layer of a part. The solidified second region of the precursor material can adhere to the solidified first region of the precursor material to form a second layer of the part. In some implementations, the first region and the second region are included within a single layer of a part. In some implementations, at least one of the first shear force and the second shear force comprises a rotational shear force.

[0013] These and other aspects and arrangements are discussed in detail below. The foregoing information and the following detailed description include illustrative examples of various aspects and arrangements, and provide an overview or framework for understanding the nature and character of the claimed aspects and arrangements. The drawings provide illustration and a further understanding of the various aspects and arrangements, and are incorporated in and constitute a part of this specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The accompanying drawings are not intended to be drawn to scale. Like reference numbers and designations in the various drawings indicate like elements. For purposes of clarity, not every component may be labeled in every drawing.

[0015] FIG. 1 is a perspective view of an example system that can be used to align anisotropic particles in an additive manufacturing process, according to an illustrative implementation.

[0016] FIG. 2 is a flowchart of an example method for aligning anisotropic particles in an additive manufacturing process, according to an illustrative implementation.

[0017] FIGS. 3 A-3H show various stages of construction of a part that can be fabricated according to the method shown in FIG. 2, according to an illustrative implementation.

DETAILED DESCRIPTION

[0018] Following below are more detailed descriptions of various concepts related to, and implementations of systems and methods for aligning anisotropic particles for additive manufacturing. The concepts introduced above and discussed in greater detail below may be implemented in any of numerous ways, as the described concepts are not limited to any particular manner of implementation. Examples of specific implementations and applications are provided primarily for illustrative purposes.

[0019] Discontinuous fiber composites (or composites including other types of anisotropic particles) are strong, lightweight and have high fracture toughness. A challenge to adapting additive manufacturing technology to discontinuous fiber-reinforced composites is the ability to control the orientation of fibers during the printing process. A fiber aligned with the applied stress reinforces the encompassing matrix, while an orthogonal fiber acts as a defect, weakening the polymer matrix. Randomized fibers (standard for systems without control) perform in the region between these two extremes resulting in negligibly impacting composite strength while severely sacrificing ductility.

[0020] Systems and methods for producing a composite part are provided that enable control over the fiber or other particle orientation within each layer of the part during manufacturing by combining shear force alignment techniques and additive manufacturing to fabricate composite materials with complex microstructural particle orientation. The systems and methods employ directed colloidal assembly during a layer-by-layer manufacturing process to provide programmable control over the orientation of particles within a composite material. As an example, with these systems and methods, reinforcement architectures can be produced that enable composite materials to exhibit enhanced mechanical properties, such as, without limitation, greater stiffness, increased strength, hard and soft phases on the order of microns, and higher fracture energy properties, as well as multi-functional performance. In addition to enhanced mechanical properties, composite parts with other enhanced properties, such as thermal, electrical, and optical properties, can be produced. The methods are robust, low cost, scalable, sustainable, and can enable a new class of strong, lightweight composite parts with programmable properties.

[0021] Employing the systems and methods described herein, a composite part can be formed from a precursor material that includes anisotropic particles, such as fibers, dispersed within a matrix material in a precursor liquid form. The anisotropic particles can have any desired shape or configuration to impart the intended properties to the finished composite part. Examples include, without limitation, discontinuous fibers, rods, platelets, flakes, and whiskers.

[0022] The matrix material can be capable of being consolidated, for example by polymerization upon exposure to ultraviolet radiation. Consolidation of the matrix material is sufficient to maintain the anisotropic particles in a desired orientation in the consolidated portion of the matrix material. Consolidation can include, without limitation, solidification, partial curing, full curing, polymerization, and cross- linking.

[0023] The precursor material can be introduced into an additive manufacturing apparatus. The additive manufacturing apparatus can include a processor unit that includes instructions and a data file for producing a composite part layer by layer. The data file can be a computer aided design file (for example, .stl) that specifies the architecture of the part to be produced. The data file can include the desired orientation of the anisotropic particles within each layer of the part. From layer to layer, particles can have differing orientations. In addition, particles can have differing orientations within each individual layer. The data file can include data defining each portion of each layer having a comparable particle orientation. For example, each layer can be defined by an array of voxels (volumetric pixels), and each portion of a layer can be defined by a subset of voxels from the array of voxels. Each portion of a layer can include particles that are discretely-aligned in a direction that may differ from the direction of alignment of particles in other portion of the layer. In some implementations, voxel resolution can be at least about 50 x 50 x 50 microns. Voxel resolution can be adjusted based on the fiber size and target mechanical properties.

[0024] FIG. 1 is a perspective view of an example system 100 that can be used to align anisotropic particles in an additive manufacturing process, according to an illustrative implementation. The system 100 includes a reservoir 105 supported on a platform 110. The reservoir 105 is configured to contain the precursor material and includes a transparent lower surface. A radiation source 115 is positioned beneath the lower surface of the reservoir 105 and configured to direct radiation (e.g., UV light) through the transparent lower surface of the reservoir 105 to consolidate layers of the precursor material. A build plate 120 provides the surface on which the part is manufactured. The build plate 120 is coupled to frame 125 that supports the build plate 120 over the reservoir 105. The frame 125 allows the build plate 120 to be raised and lowered into and out of the reservoir 105 as the part is manufactured. For example, the frame 125 can allow the build plate 120 to be at least partially submerged in the precursor material contained within the reservoir 105.

[0025] The precursor material contained within the reservoir 105 is used to build the part one layer at a time. To build the first layer, the build plate 120 is lowered into the precursor material towards the lower surface of the reservoir 105. The radiation source 115 is then activated to selectively consolidate portions of the precursor material in a pattern selected according to a desired shape of the first layer of the part. In some implementations, the radiation source 115 can be a projector configured to project radiation as an image having a shape corresponding to the desired cross-sectional shape of the first layer of the part. In some other implementations, the radiation source 115 can be a laser configured to trace the cross- sectional shape of the first layer of the part. Exposure to the radiation from the radiation source 115 causes the precursor material to become selectively consolidated in the appropriate shape and, in some implementations, to adhere to the surface of the build plate 120, thereby forming the first layer of the part. Subsequent layers can be formed in a similar way. For example, the build plate can be raised vertically by a distance equal to the height of a single layer of the part, and the radiation source 115 can be activated again to selectively consolidate the precursor material and to cause the selectively consolidated portion of the precursor material to adhere to the previous layer. These steps can be repeated for each subsequent layer of the part until the complete part has been formed.

[0026] As described above, the precursor material can include anisotropic particles, such as fibers, which when aligned in a particular manner may impart beneficial characteristics to the finished part (e.g., increased strength or rigidity). For example, the precursor material can be formed from a liquid matrix material in which the anisotropic particles are suspended. Generally, the alignment of the various anisotropic particles may be random, and aligning the anisotropic particles can be time-consuming and expensive. To address these issues, the system 100 is further configured to allow anisotropic particles in the precursor material to be aligned quickly and easily before each layer is consolidated. For example, the platform 110 includes two rails 130 on which the reservoir 105 is mounted. The reservoir 105 and the rails 130 can be configured such that the reservoir 105 may be moved laterally along the rails (i.e., in the left and right directions shown in FIG. 1). In some implementations, the rails 130 can be part of a controllable mechanism, such as an XY positioning stage, having an actuator configured to control the position of the reservoir 105 along the rails 130. Thus, in some examples, the system 100 may include other components (not shown) that allow the reservoir to be moved in other directions within a plane parallel to the surface of the platform 110, such as a second set of rails oriented perpendicularly with respect to the rails 130. In some implementations, the reservoir 105 may be stationary while the build plate 120 moves in the plane parallel to the surface of the platform 110. The relative motion between the reservoir 105 and build plate 120 can be used to impart shear forces within the precursor material that cause the anisotropic particles to become aligned in a region beneath the build plate 120.

[0027] After the particles have been aligned, the radiation source 115 can be activated to consolidate at least a portion or region of a layer, to maintain the alignment of the particles within the consolidated portion. In some implementations, multiple regions of a single layer can be consolidated separately, in order to form a part having different particle alignment within different regions of each layer. For example, each layer of the part can be divided into any number of regions, each of which may be non-overlapping with the other regions for that layer. Relative motion between the reservoir 105 and the build plate 120 can be used to align the particles in a selected direction, and the radiation source 115 can be activated to consolidate the precursor material in a selected region of a layer. This technique can be repeated to align the particles in a different direction, and the radiation source can again be activated to consolidate the precursor material in another selected region of the layer. These steps can be repeated any number of times within a single layer, such that each layer may have any number of regions each having a selected direction of particle alignment, which may be different from the direction of particle alignment for other regions of that layer. This alignment technique is described further below.

[0028] It should be understood that the principles illustrated in FIG. 1 and described above also can be used in different configurations not illustrated. For example, in some

implementations, the reservoir 105 may be supported in a different manner without use of a platform 110. In some implementations, the reservoir 105 may be suspended from above or supported by posts. In some implementations, the reservoir 105 and the platform 110 may be formed as a single integrated part of the system 100. In some implementations, the platform 110 may be implemented as any type of support structure capable of supporting the reservoir 105. For example, the platform 110 may include any portion of the system 100, such as a tower or gantry, which may be formed integrally with or coupled to the frame 125.

[0029] In some implementations, the system 100 may include an actuator configured to cause the build plate 120 or the reservoir 105 to rotate about an axis normal to the build surface. When relative rotation between the surfaces of the build plate 120 and the reservoir 105 is created about the axis, shear forces can be created concentrically about that axis with increasing shear rate farther from the axis of rotation. Such shear forces can be used to align a plurality of anisotropic particles in any 360-degree alignment direction based on their position relative to the axis of rotation. In some cases, these shear forces may be used to optimally reinforce the fibers around circular features, such as a hole formed through a part.

[0030] In some implementations, an actuator included in the system 100 can be configured to cause any type of translational or rotational movement of the reservoir 105. For example, the actuator can be or can include a linear rod, a piston, a constrained lead screw, a belt drive, a rack and pinion system, a pivoted angular motion system, any type of mechanical linkage system, or any other type of actuator configured to cause the reservoir to translate or rotate within a plane. In some implementations, the system 100 can include an actuator coupled to the build plate 120, rather than to the reservoir 105. For example, the actuator coupled to the build plate can cause rotational or translational motion of the build plate 120, while the reservoir 105 remains stationary.

[0031] FIG. 2 is a flowchart of an example method 200 for aligning anisotropic particles in an additive manufacturing process, according to an illustrative implementation. FIGS. 3A- 3H show various stages of construction of a part that can be fabricated according to the method shown in FIG. 2, according to an illustrative implementation. FIGS. 2 and 3A-3H are discussed together below.

[0032] Referring now to FIG. 2, in brief overview, the method 200 includes providing a precursor material including a matrix material and a plurality of anisotropic particles (step 205). The method 200 includes exposing the precursor material to a first shear force to cause at least a first portion of the plurality of anisotropic particles to become oriented in a first alignment direction based on a direction of the first shear force (step 210). The method includes solidifying a first region of the precursor material with the first portion of the plurality of anisotropic particles oriented in the first alignment direction (step 215). The method 200 includes exposing the precursor material to a second shear force to cause at least a second portion of the plurality of anisotropic particles to become oriented in a second alignment direction based on a direction of the second shear force (step 220). The method 200 includes solidifying a second region of the matrix material with the second portion of the plurality of anisotropic particles oriented in the second alignment direction (step 225). [0033] Referring again to FIG. 2, and in greater detail, the method 200 includes providing a precursor material including a matrix material and a plurality of anisotropic particles (step 205). In some implementations, the precursor material can include a liquid matrix, which may be a polymer material. The matrix material can be capable of being consolidated in response to exposure to radiation, such as UV light. In some implementations, the anisotropic particles can be fibers or whiskers selected to provide increased strength to the finished part. In some implementations, the precursor material can be provided in a reservoir configured to receive a build plate. The results of this step are illustrated in FIG. 3 A, which shows a cross-sectional view of a reservoir 305 containing a precursor material 312. The precursor material includes a liquid matrix material and a plurality of fibers, such as the fiber 314, illustrated by lines within the precursor material 312. As shown, the orientation of the plurality of fibers within the precursor material 312 is random. A build plate 320 is shown suspended over the reservoir 305. In some implementations, the reservoir 305 and the build plate 320 can be similar to the reservoir 105 and the build plate 120, respectively, shown in FIG. 1. While the build plate 320 is depicted in FIG. 3 A as suspended over the reservoir 305 for illustrative purposes, it should be understood that the build plate 320 can be configured to be lowered into the reservoir 320 such that it is submerged in the precursor material 312.

[0034] The method 200 includes exposing the precursor material to a first shear force to cause at least a first portion of the plurality of anisotropic particles to become oriented in a first alignment direction based on a direction of the first shear force (step 210). In some implementations, the shear force can be created by a difference in relative motion of the reservoir and the build plate. For example, as described above in connection with FIG. 1, the reservoir can be mounted to a controllable XY positioning stage. The build plate can be lowered into the precursor material contained within the reservoir, and the reservoir can be moved laterally to create a shear force within the precursor material. [0035] In some implementations, shear forces can be applied to the precursor material in more than one direction. For example, the anisotropic particles can include platelets, which may be disk shaped. Such particles may be aligned in a direction via exposure to shear forces alternating between at least two directions, which may be offset from one another by a predetermined angle such as 90 degrees. Thus, the precursor material can be exposed to a series of shear forces in different directions in order to align the anisotropic particles in step 210.

[0036] The results of this step are illustrated in FIG. 3B. As shown, the build plate 320 has been lowered into the reservoir 305, such that the lower surface of the build plate is separated from the reservoir by a small distance. In some implementations, this distance can be selected to be equal to the desired thickness of a first layer of the part to be manufactured. The reservoir 305 is moved laterally in the direction shown by the arrow 318, while the build plate remains stationary. Because the build plate 320 is separated from the bottom of the reservoir 305 by a small distance, the relative motion of the build plate 320 and the precursor material 312 within the reservoir 305 imparts shear forces on the precursor material 312 in the region between the lower surface of the build plate 320 and the bottom of the reservoir 305. These shear forces cause the anisotropic particles within this region of the precursor material 312 to become aligned. As shown, the direction of alignment is parallel to the direction of motion of the reservoir 305 (and therefore parallel to the direction of the applied shear force). The anisotropic particles in other regions of the precursor material 312 are not subjected to such large shear forces, and therefore may remain substantially unaligned (i.e., aligned randomly throughout the precursor material).

[0037] In some instances, the build plate 320 may move back and forth along the same direction to achieve the desired fiber alignment direction (i.e., both directions of the arrow 318 shown in FIG. 3B). The shear force caused by moving in a first linear direction can have a similar alignment effect as the shear force caused by moving in a linear direction that is 180° different from the first direction. By moving back and forth in 180° increments, fibers or other anisotropic particles may be aligned on thin features of the part, where motion in a single direction would not be able to affect alignment due to the small area under the feature for fibers to rotate into alignment. In some other implementations, as described above, the build plate 320 may move in alternating directions which may be offset from one another at a predetermined angle, such as 90 degrees, in order to cause alignment of the anisotropic particles.

[0038] The method 200 includes solidifying a first region of the precursor material with the first portion of the plurality of anisotropic particles oriented in the first alignment direction (step 215). In some implementations, consolidation can occur as a result of exposure to radiation, such as UV light. A depiction of this step is illustrated in FIG. 3C. A radiation source 315 is positioned beneath the lower surface of the reservoir 305, and is activated to direct radiation through the lower surface of the reservoir 305, as shown by the broken arrows in FIG. 3C. In some implementations, the lower surface of the reservoir 305 can be formed from a material that is transparent to the radiation emitted by the radiation source 315, thereby allowing the radiation to pass through the reservoir 305 and contact the precursor material 312 in the region beneath the build plate. In some implementations, the radiation source 315 can be configured to emit radiation in a pattern corresponding to a desired shape of the first layer of the part to be manufactured, such that the precursor material 312 becomes selectively solidified or consolidated in the desired shape and adheres to the lower surface of the build plate 320. Thus, when the radiation source 315 is deactivated and the build plate 320 is subsequently raised out of the precursor material 312, the first layer 322 of the part remains attached to the build plate 320, as illustrated in FIG. 3D. [0039] In some implementations, the first layer 322 may be divided into two or more regions, each of which may include anisotropic particles aligned in a different direction. For example, in such an implementation, the radiation source 315 may be activated to emit radiation in a shape that corresponds to only a single region of the first layer 322, rather than the shape of the entire layer 322. After the region is consolidated, the anisotropic particles can be realigned in a different direction by exposing the precursor material to a shear force in a manner similar to that described above, and the radiation source 315 can be activated to consolidate another region of the first layer 322. This process can be repeated any number of times until the first layer 322 is complete (i.e., until every region of the first layer 322 has been consolidated).

[0040] The method 200 includes exposing the precursor material to a second shear force to cause at least a second portion of the plurality of anisotropic particles to become oriented in a second alignment direction based on a direction of the second shear force (step 220). In some implementations, the process for generating the second shear force can be similar to that used to generate the first shear force. Thus, the build plate 320 can be lowered into the reservoir 305 such that the lower surface of the first layer 322 of the part is positioned near the bottom surface of the reservoir 305, as illustrated in FIG. 3E. The reservoir 305 can be moved laterally in the direction of the arrow 326 to create a shear force within the precursor material 312 between the first layer 322 of the part and the bottom of the reservoir 305, thereby causing alignment of the anisotropic particles in the precursor material 312. It should be noted that, in some implementations, the direction of motion of the reservoir 305 during this step (and thus the direction of the resulting shear force) can be different from the direction of motion used to generate the first shear force in step 210. In other implementations, the direction of motion of the reservoir 305 during step 220 can be the same as the direction of motion used to generate the first shear force in step 210. In some other implementations, as described above, the build plate 320 may move in a series of alternating directions in this step, which may be offset from one another at a predetermined angle, such as 90 degrees, in order to cause alignment of the anisotropic particles.

[0041] The method 200 includes solidifying a second region of the precursor material with the second portion of the plurality of anisotropic particles oriented in the second alignment direction (step 225). Solidification of the second region of the matrix material can be achieved in a manner similar to that used for solidifying the first region in step 215. The results of this stage are illustrated in FIG. 3F. The radiation source 315 emits radiation towards the lower surface of the reservoir 305 in a pattern corresponding to a desired shape for the second layer of the part. Thus, the second region of the precursor material 312 becomes solidified or consolidated, and adheres to the first layer 322 of the part, forming a second layer 324 of the part as illustrated in FIG. 3G. In some implementations, the steps of exposing the precursor material to a shear force to cause alignment of the anisotropic particles, and solidifying a successive region of the precursor material, can be repeated any number of times to form additional layers of the part, until the complete part has been fabricated.

[0042] In some implementations, the second layer 324 may be divided into two or more regions, each of which may include anisotropic particles aligned in a different direction. For example, in such an implementation, the radiation source 315 may be activated to emit radiation in a shape that corresponds to only a single region of the second layer 324, rather than the shape of the entire second layer 324. After the region is consolidated, the anisotropic particles can be realigned in a different direction by exposing the precursor material to a shear force in a manner similar to that described above, and the radiation source 315 can be activated to consolidate another region of the second layer 324. This process can be repeated any number of times until the second layer 324 is complete (i.e., until every region of the second layer 324 has been consolidated).

[0043] In some implementations, steps 220 and 225 of the method 200 can be repeated any number of times. For example, repeating these steps can cause an additional layer of the part to be formed. Thus, a part having many layers can be constructed by repeating these steps for each additional layer of the part after the second layer. The part may be constructed to have any number of layers. For example, in some implementations the part may have tens, hundreds, or thousands of layers.

[0044] FIG. 3H shows a top-down view of the reservoir 305 and the build plate 320 after the first layer 322 and the second layer 324 of the part have been consolidated on the build plate 320. Also depicted in FIG. 3H is an enlarged view 328 of a portion of the part including a first consolidated region 330 and a second consolidated region 332. As shown, the alignment direction of the anisotropic particles within the first consolidated region 330 can be different from the alignment direction of the anisotropic particles within the second consolidated region 330. In some implementations, the first consolidated region 330 can be included in the same layer of the part as the second consolidated region 332. For example, the first consolidated region 330 and the second consolidated region 332 may both be included within the first layer 322, or may both be included within the second layer 324. In some other implementations, the first consolidated region 330 and the second consolidated region 332 can be included in different layers of the part. For example, the first consolidated region 330 may be included in the first layer 322, while the second consolidated region 332 is included in the second consolidated region 324. It should be understood that, in some implementations, the part may include any number of additional layers, and the alignment direction of the anisotropic particles within each layer may be selected independent of the alignment direction of the anisotropic particles within other layers. In addition, each layer may include any number of regions (such as the consolidated regions 330 and 332 shown in FIG. 3H), and the alignment direction of the anisotropic particles within each region may be selected independent of the alignment direction of the anisotropic particles within other regions within the same layer.

[0045] While the above description focuses on the use of shear forces to align the anisotropic particles in the precursor material 312, other techniques also may be used in combination with the application of shear forces. For example, in some implementations some or all of the anisotropic particles may be formed from magnetically responsive materials. One or more magnetic fields may be applied to the precursor material in the region beneath the build plate 320 to cause alignment of the magnetically responsive anisotropic particles in that region, prior to (or during) solidification of a layer of the precursor material 312. In some other implementations, other alignment techniques also can be combined with the techniques described above to further align the anisotropic particles in the precursor material 312.

[0046] As shown within the enlarged view 328 is a portion of the build plate 320, the first layer 322 and the second layer 324 (as well as any additional layers included within the part) may have complex shapes that correspond to the shape of the regions of the precursor material that were selectively consolidated during fabrication of each respective layer. In some implementations, the part may be shaped such that it does not cover the entire surface of the build plate 320, thereby leaving a portion of the build plate 320 visible in the enlarged view 328 of FIG. 3H.

[0047] Various modifications to the implementations described in this disclosure may be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other implementations without departing from the spirit or scope of this disclosure. Thus, the claims are not intended to be limited to the implementations shown herein, but are to be accorded the widest scope consistent with this disclosure, the principles and the novel features disclosed herein.

[0048] Certain features that are described in this specification in the context of separate implementations also can be implemented in combination in a single implementation.

Conversely, various features that are described in the context of a single implementation also can be implemented in multiple implementations separately or in any suitable

subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed

combination may be directed to a subcombination or variation of a subcombination.

[0049] Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. Further, the drawings may schematically depict one more example processes in the form of a flow diagram. However, other operations that are not depicted can be incorporated in the example processes that are schematically illustrated. For example, one or more additional operations can be performed before, after, simultaneously, or between any of the illustrated operations. In certain circumstances, multitasking and parallel processing may be advantageous. Moreover, the separation of various system components in the implementations described above should not be understood as requiring such separation in all implementations, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products. Additionally, other implementations are within the scope of the following claims. In some cases, the actions recited in the claims can be performed in a different order and still achieve desirable results.