Patent Application
20190202131
The present disclosure relates generally to an additive manufacturing system and, more particularly, to a system and method for additively manufacturing functional elements into existing components.
Traditional additive manufacturing is a process of creating three-dimensional parts by depositing overlapping layers of material under the guided control of a computer. A common form of additive manufacturing is known as fused deposition modeling (FDM). Using FDM, a thermoplastic is passed through and liquified within a heated print head. The print head is moved in a predefined trajectory (a.k.a., a tool path) as the material discharges from the print head, such that the material is laid down in a particular pattern and shape of overlapping 2-dimensional layers. The material, after exiting the print head, cools and hardens into a final form. A strength of the final form is primarily due to properties of the particular thermoplastic supplied to the print head and a 3-dimensional shape formed by the stack of 2-dimensional layers.
A recently developed improvement over traditional FDM manufacturing involves the use of continuous fibers embedded within material discharging from the print head (a.k.a., Continuous Fiber 3D Printing—CF3D™). In particular, a matrix is supplied to the print head and discharged (e.g., extruded and/or pultruded) along with one or more continuous fibers also passing through the same head at the same time. The matrix can be a traditional thermoplastic, a powdered metal, a liquid matrix (e.g., a UV curable and/or two-part resin), or a combination of any of these and other known matrixes. Upon exiting the print head, a cure enhancer (e.g., a UV light, an ultrasonic emitter, a heat source, a catalyst supply, etc.) is activated to initiate and/or complete curing of the matrix. This curing occurs almost immediately, allowing for unsupported structures to be fabricated in free space. And when fibers, particularly continuous fibers, are embedded within the structure, a strength of the structure may be multiplied beyond the matrix-dependent strength. An example of this technology is disclosed in U.S. Pat. No. 9,511,543 that issued to Tyler on Dec. 6, 2016 (“the '543 patent”).
It is known to use CF3D™ to embed functional elements into a structure during fabrication. Specifically, one or more of the continuous fibers making up the structure can include wires (electrical leads) and/or optical tubes (e.g., fiber-optic cables). These wires and/or optical tubes can then be used as heaters, strain gauges, and/or signal conductors. Although this technology may provide expanded functionality for newly fabricated structures, the application of this technology to existing structures may be problematic.
The disclosed system and method are directed to overcoming one or more of the problems set forth above and/or other problems of the prior art.
In one aspect, the present disclosure is directed to a system for additively manufacturing a composite structure. The system may include a head having a matrix reservoir, a nozzle fluidly connected to the matrix reservoir and configured to discharge a composite material into a feature of an existing component. a guide configured to detect a location of the feature, and a cure enhancer configured to expose composite material discharging from the nozzle to a cure energy. The system may also include a support configured to move the head in multiple dimensions, and a controller in communication with the cure enhancer and the support. The controller may be configured to cause the support to move the head during discharge of the composite material into the feature based on the detected location of the feature.
In another aspect, the present disclosure is directed to another system for additively manufacturing a composite structure. This system may include a head having a matrix reservoir, a nozzle fluidly connected to the matrix reservoir and having a plurality of separate channels arranged sequentially in a direction of travel of the head, and a cure enhancer configured to expose composite material discharging from the nozzle to a cure energy. The system may also include a support configured to move the head in multiple dimensions, and a controller in communication with the cure enhancer and the support. The controller may be configured to cause the support to move the head during discharge of the composite material into the feature.
Head 16 may be configured to receive or otherwise contain a matrix. The matrix may include any type of material (e.g., a liquid resin, such as a zero-volatile organic compound resin; a powdered metal; etc.) that is curable. Exemplary matrixes include thermosets, single- or multi-part epoxy resins, polyester resins, cationic epoxies, acrylated epoxies, urethanes, esters, thermoplastics, photopolymers, polyepoxides, thiols, alkenes, thiol-enes, and more. In one embodiment, the matrix inside head 16 may be pressurized, for example by an external device (e.g., an extruder or another type of pump—not shown) that is fluidly connected to head 16 via a corresponding conduit (not shown). In another embodiment, however, the matrix pressure may be generated completely inside of head 16 by a similar type of device. In yet other embodiments, the matrix may be gravity-fed through and/or mixed within head 16. In some instances, the matrix inside head 16 may need to be kept cool and/or dark to inhibit premature curing; while in other instances, the matrix may need to be kept warm for the same reason. In either situation, head 16 may be specially configured (e.g., insulated, chilled, and/or warmed) to provide for these needs.
The matrix may be used to coat, encase, or otherwise at least partially surround any number of continuous reinforcements (e.g., separate fibers, tows, rovings, ribbons, and/or sheets of material) and, together with the reinforcements, make up at least a portion (e.g., a wall, a floor, a ceiling, a filling, etc.) of composite structure 12. The reinforcements may be stored within (e.g., on separate internal spools—not shown) or otherwise passed through head 16 (e.g., fed from external spools). When multiple reinforcements are simultaneously used, the reinforcements may be of the same type and have the same diameter and cross-sectional shape (e.g., circular, square, flat, etc.), or of a different type with different diameters and/or cross-sectional shapes. The reinforcements may include, for example, carbon fibers, vegetable fibers, wood fibers, mineral fibers, glass fibers, metallic wires, optical tubes, etc. It should be noted that the term “reinforcement” is meant to encompass both structural and non-structural types of continuous materials that can be at least partially encased in the matrix discharging from head 16.
The reinforcements may be exposed to (e.g., coated with) the matrix while the reinforcements are inside head 16, while the reinforcements are being passed to head 16 (e.g., as a pre-preg material), and/or while the reinforcements are discharging from head 16, as desired. The matrix, dry reinforcements, and/or reinforcements that are already exposed to the matrix (e.g., wetted reinforcements) may be transported into head 16 in any manner apparent to one skilled in the art.
The matrix alone, the reinforcement alone, and/or the matrix-wetted reinforcement may be discharged from head 16 via at least two different modes of operation. In a first mode of operation, the matrix and/or reinforcement are extruded (e.g., pushed under pressure and/or mechanical force) from head 16, as head 16 is moved by support 14 to create the 3-dimensional shape of structure 12. In a second mode of operation, at least the reinforcement is pulled from head 16, such that a tensile stress is created in the reinforcement during discharge. In this mode of operation, the matrix may cling to the reinforcement and thereby also be pulled from head 16 along with the reinforcement, and/or the matrix may be discharged from head 16 under pressure along with the pulled reinforcement. In the second mode of operation, where the matrix is being pulled from head 16, the resulting tension in the reinforcement may increase a strength of structure 12, while also allowing for a greater length of unsupported material to have a straighter trajectory (i.e., the tension may act against the force of gravity to provide free-standing support for structure 12).
The reinforcement may be pulled from head 16 as a result of head 16 moving away from an anchor point 18. In particular, at a start of structure-formation, a length of matrix and/or matrix-impregnated reinforcement may be adhered to anchor point 18 (e.g., via curing of the matrix). Thereafter, head 16 may be moved away from anchor point 18, and the relative movement may cause the reinforcement to be pulled from head 16. It should be noted that the movement of the matrix and/or reinforcement through head 16 could be assisted (e.g., via internal feed mechanisms), if desired. In some embodiments, the discharge rate of the reinforcement from head 16 may primarily be the result of relative movement between head 16 and anchor point 18, such that tension is created within the reinforcement. It is contemplated that anchor point 18 could be moved away from head 16 instead of or in addition to head 16 being moved away from anchor point 18.
One or more cure enhancers (e.g., one or more light sources, an ultrasonic emitter, a laser, a heater, a catalyst dispenser, a microwave generator, a chiller, etc.) 20 may be mounted proximate (e.g., within, on, and/or trailing from) head 16 and configured to enhance a cure rate and/or quality of the matrix as it is discharged from head 16. In some embodiments, cure enhancer 20 may be controlled to selectively expose internal and/or external surfaces of structure 12 to cure energy (e.g., light energy, electromagnetic radiation, vibrations, heat, a chemical catalyst or hardener, etc.) during the formation of structure 12. In these embodiments, the energy may increase a rate of chemical reaction occurring within the matrix, sinter the material, harden the material, or otherwise cause the material to cure as it discharges from head 16. In other embodiments, cure enhancers 20 may function to remove energy from the matrix, thereby causing the matrix to cool and harden.
A controller 22 may be provided and communicatively coupled with support 14, head 16, and any number and type of cure enhancers 20. Controller 22 may embody a single processor or multiple processors that include a means for controlling an operation of system 10. Controller 22 may include one or more general- or special-purpose processors or microprocessors. Controller 22 may further include or be associated with a memory for storing data such as, for example, design limits, performance characteristics, operational instructions, matrix characteristics, reinforcement characteristics, characteristics of structure 12, and corresponding parameters of each component of system 10. Various other known circuits may be associated with controller 22, including power supply circuitry, signal-conditioning circuitry, solenoid/motor driver circuitry, communication circuitry, and other appropriate circuitry. Moreover, controller 22 may be capable of communicating with other components of system 10 via wired and/or wireless transmission.
One or more maps may be stored in the memory of controller 22 and used during fabrication of structure 12. Each of these maps may include a collection of data in the form of models, lookup tables, graphs, and/or equations. In the disclosed embodiment, the maps are used by controller 22 to determine desired characteristics of cure enhancers 20, the associated matrix, and/or the associated reinforcements at different locations within structure 12. The characteristics may include, among others, a type, quantity, and/or configuration of reinforcement and/or matrix to be discharged at a particular location within structure 12, and/or an amount, intensity, shape, and/or location of desired curing. Controller 22 may then correlate operation of support 14 (e.g., the location and/or orientation of head 16) and/or the discharge of material from head 16 (a type of material, desired performance of the material, cross-linking requirements of the material, a discharge rate, etc.) with the operation of cure enhancers 20, such that structure 12 is produced in a desired manner
As shown in
As also shown in
Referring to
Referring back to the embodiment of
Head 16 may be moved by support 14 to follow a pre-programmed path associated with feature 24, thereby allowing nozzle 30 to fill feature 24 with material. In some applications, it may be beneficial to assist and/or alternatively control movements of head 16 with a detected location of feature 24. A guide 34 may be used for this purpose. It should be noted that, although guide 34 is shown as being connected to head 16, guide 34 could alternatively be located offboard head 16 (e.g., connected directly to support 14 or connected to an independent support—not shown).
In the embodiment of
In some applications, it may be beneficial to compact the material being discharged by nozzle 30. For example, compacting may provide for a greater density of reinforcements, situate the reinforcements at a desired location (e.g., at a center) within the matrix, and/or provide a desired texture to an outer surface of the material. In the depicted example, this compaction is provided by way of a shoe 40 that trails behind nozzle 30 (e.g., between nozzle 30 and cure enhancer 20). It is contemplated, however, that another device (e.g., a compaction wheel) could additionally or alternatively be used for this purpose, if desired.
Shoe 40 may be biased (e.g., via a spring 42—shown only in
Another exemplary head 16 that may be used to fill feature 24 within component 26 is illustrated in
Head 16 of
Head 16 of
Thermoset channel 48a may be configured to discharge a reinforcement (e.g., fiberglass) that has been wetted with a thermoset epoxy or the thermoset epoxy alone (e.g., an epoxy contained within matrix reservoir 28). First reinforcement channel 48b may be configured to discharge a matrix-wetted or dry reinforcement of a first size. Second reinforcement channel 48c may be configured to discharge a matrix-wetted or dry reinforcement of a second size. In the disclosed embodiment, first and second reinforcement channels are fluidly isolated from matrix reservoir 28. It is contemplated, however, that one or both of first and second reinforcement channels 48b, 48c could be fluidly connected to matrix reservoir 28, if desired. Thermoplastic channel 48d may be configured to discharge a thermoplastic matrix only or a thermoplastic-wetted reinforcement. Thermoplastic channel 48d may be fluidly isolated from matrix reservoir 28. A trailing edge of each channel 48 may be rounded to reduce breakage of any associated reinforcements.
The thermoset-wetted reinforcement discharging from channel 48a may form a bed within feature 24 for one or both of the reinforcements subsequently discharged from channels 48b and/or 48c. In particular, it has been found that thermoset epoxies may not always readily coat and/or cling to metallic wires and/or optical tubes. However, when placing a wetted-fiber adjacent these other reinforcements, the associated matrix material within the fiber will spread and adequately coat the metallic wires and optical tubes. The thermoplastic material discharging from channel 48d may be substantially identical to the material making up component 26 (or at least formulated to readily bond with the component material in a desirable manner), thereby allowing for sealing of feature 24.
In the embodiment of
Depending on a distance between thermoset and thermoplastic channels 48a, 48d, it may become difficult for nozzle 30 to accurately lay down material within feature 24. For example, it may be problematic to lay down material into feature 24 when a turn radius of feature 24 is smaller than a distance between channels 48a, 48b. Accordingly, in some embodiments, one or more of channels 48 may be pivotally connected to each other (e.g., via one or more hinges 58). Hinge(s) 58 may allow for a sharper turn radius of nozzle 30. In other embodiments, one or more of channels 48 are features of a monolithic nozzle body.
The heat may be provided via a separate heating mechanism 50 that is associated with thermoplastic channel 48d. For example, heat may be conducted from heating mechanism 50 to a thermoplastic feedstock passing through channel 48, causing the feedstock to soften and/or melt within nozzle 30. Some of this heat may also be conducted toward channel 48a, allowing the associated thermoset epoxy within channel 48a to warm to an initiation threshold just prior to discharge from nozzle 30. In some situations, this heat, alone, may be sufficient to fully cure the thermoset epoxy. In other situations, however, cure enhancers 20 may still be utilized and curing may simply be assisted by the heat from mechanism 50.
It is contemplated that, instead of or in addition to heat being conducted from heating mechanism 50 toward the thermoset epoxy, one or more of the reinforcements within structure 12 could be electrically charged during fabrication of structure 12. For example, a first end (e.g., an end already placed into feature 24) of one or more of the reinforcements could be grounded, while a second end (e.g., an end within a supply located upstream of or inside of head 16) could be charged. A current would then pass from the second end to the first end, causing the reinforcement to heat. The heat from this reinforcement would then be conducted into the surrounding thermoset epoxy, facilitating curing thereof.
Component 26 may benefit from reinforcements of different sizes at different locations within feature 24. Based on component specifications and signals from guide 34 and/or scanner 46 (referring to
The reinforcement being discharged through any channel 48 may have unique characteristics that allow for increased functionality within structure 12. For example, the reinforcement may include one or more functional elements 60 connected to or otherwise forming an integral portion of the reinforcement. Functional elements 60 may include, for example, resisters, capacitors, light-emitting diodes (LED), RFID tags, switches, batteries, fuses, filters (e.g., low-pass filters), etc. For example, a particular reinforcement may have, at a particular axial distance along its length, an LED that is integrally joined between opposing first and second ends. At this location, the LED may function as a continuity indicator, for example, illuminating any time a current of a minimum magnitude passes from the first end to the second end. Functional elements 60 may become an integral portion of the reinforcements prior to the reinforcements passing through head 16.
In the disclosed embodiments, the material discharging from channel 48d includes a reinforcement that is braided and/or is made from a metallic foil (e.g., a solid or perforated foil), as well as a thermoset matrix having suspended metallic particles and/or that is electrically conductive and grounded at particular locations. It is also contemplated that the thermoset matrix may be transparent at particular locations, such that the functional elements 60 described above may be observed.
The disclosed system, head, and nozzle may be used to impart functionality to existing structures. For example, wiring harnesses, electrical grids, sensors, heaters, etc. may be embedded into the skins of existing automobiles, aircraft, watercraft, and other types of machine, where light-weight, low-cost, small-footprint, and high-performance are important. These functional elements may be embedded at low-cost, due to the reduction in dedicated tooling for each configuration, and due to the ability to redesign and make on-the-fly adjustments. The associated components embedded into the machines may have a low footprint, because they are fabricated directly in place on machine 12. In addition, the disclosed system may impart high-performance due to the unique ways that particular reinforcements, functional elements 60, and matrix materials can be used and laid out within the components. Operation of system 10 will now be described in detail, with reference to
At a start of a manufacturing event, information regarding a desired structure 12, feature 24, and/or component 26 may be loaded into system 10 (e.g., into controller 22 that is responsible for regulating operation of support 14, cure enhancer(s) 20, shoe 40, heating mechanism 50, feed mechanisms 52, cutter 54, and/or any other associated components). This information may include, among other things, a size (e.g., diameter, wall thickness, length, etc.), a contour (e.g., a trajectory), surface features (e.g., ridge size, location, thickness, length; flange size, location, thickness, length; etc.), connector geometry (e.g., locations and sizes of couplings, tees, splices, etc.), location-specific matrix stipulations, location-specific reinforcement stipulations, location-specific conductor stipulations, desired cure rates, cure locations, cure shapes, cure amounts, surface contours, etc. It should be noted that this information may alternatively or additionally be loaded into system 10 at different times and/or continuously during the manufacturing event, if desired.
Based on the component information, and one or more different (e.g., different sizes, shapes, and/or types of) reinforcements and/or matrix materials may be selectively installed within system 10 and/or continuously supplied into print head 16. The corresponding reinforcements (e.g., prepreg or dry fibers, tows, ribbons, sheets, wires, optical tubes, etc.) may be threaded through matrix reservoir 28 and/or channels 48 of print head 16 and nozzle 30, and thereafter connected to a pulling machine (not shown) and/or to a mounting fixture (e.g., to anchor point 18 and/or feature 24). Installation of the matrix material may include filling matrix reservoir 28 with resin and/or directing feedstock into channel 48d.
Print head 16 may be moved by support 14 under the regulation of controller 22 to cause matrix only, reinforcement only, and/or matrix-coated reinforcements to be placed against a surface of feature 24 and/or on a corresponding anchor point 18. Cure enhancers 20 may then be selectively activated to cause hardening of the matrix material(s), thereby bonding the reinforcements to anchor point 18 and/or feature 24. In some embodiments, activation of cure enhancers 20 may be unnecessary, and heat from heating mechanism 50 may be sufficient for initial anchoring.
The component, feature, and/or materials information may then be used to control operation of system 10. For example, the reinforcement(s) may be submerged within associated matrixes, and pulled through the corresponding channels 48 to at least partially fill feature 24. As described above, head 16 may additionally fabricate feature 24 prior to filling, in some applications. Controller 22 may selectively cause support 14 to move print head 16 in a desired manner at this time (e.g., based on input and/or feedback from guide 34 and/or scanner 46), such that the discharging composite material follows a desired trajectory inside of feature 24. In addition, cure enhancers 20 may be selectively activated by controller 22 during material discharge to initiate, speed up, or complete hardening of the matrix material. As feature 24 is filled with thermoset matrix, fibers, wires, and/or optical tubes, the exposed side of feature 24 may be sealed off with thermoset matrix (and additional reinforcements, if desired).
As described above, during filling of feature 24, nozzle 30 may be oriented generally normal to the surface of component 26, and ride along sides of feature 24. This may allow matrix located at the tip end of nozzle 30 to contact walls of feature 24. This contact may result in extra (e.g., up to about 20% extra) matrix being drawn out of nozzle 30 than would normally be pulled out by movement of reinforcement only.
Once an end of feature 24 has been reached, the reinforcements may be disconnected (e.g., severed) from print head 16 in any desired manner In some embodiments, the severed ends of the reinforcement(s) may then be joined to connectors (e.g., power sources, grounds, etc.), if desired, thereby completing fabrication of component 26.
It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed, system, head, nozzle, and fabrication method. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed system, head, nozzle, and fabrication method. For example, it is contemplated that a groove cleaner (not shown), similar to cutting mechanism 44, could be used to clean feature 24 (e.g., an existing feature or the feature created by cutting mechanism 44. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents.
