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Title:
SYSTEMS AND METHODS FOR 3D COEXTRUSION PRINTING
Document Type and Number:
WIPO Patent Application WO/2018/044759
Kind Code:
A1
Abstract:
Systems and methods for 3D printing that involve coextruding two or more substantially immiscible materials to create a coextruded printing strand that is used to free-form fabricate a 3D object. In some embodiments, the ratio(s) of the two or more materials can be precisely controlled and/or varied as coextrusion progressing to differing material profiles throughout the coextruded printing strand. This allows, for example, for the creation of 3D objects having one or more properties (e.g., optical, mechanical, electrical, etc.) that precisely vary, continuously and/or abruptly as desired, within the 3D object.

Inventors:
LEE, Patrick, C. (Given Building E201, 89 Beaumont AvenueBurlington, VT, 05405, US)
Application Number:
US2017/048820
Publication Date:
March 08, 2018
Filing Date:
August 28, 2017
Export Citation:
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Assignee:
THE UNIVERSITY OF VERMONT AND STATE AGRICULTURAL COLLEGE (Given Building E201, 89 Beaumont AvenueBurlington, VT, 05405, US)
International Classes:
B29C67/00; B29C69/00
Foreign References:
US20100252105A12010-10-07
US20160136887A12016-05-19
US20140027952A12014-01-30
US20140291886A12014-10-02
Attorney, Agent or Firm:
HELLER, Morgan, S., II (Downs Rachlin Martin PLLC, 199 Main Street P.O. Box 19, Burlington VT, 05402-0190, US)
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Claims:
What is claimed is:

1. A method of forming a 3D object, the method comprising:

producing a coextruded printing strand containing two or more substantially immiscible

materials coextruded with one another; and

controllably depositing the coextruded printing strand so as to continually build the 3D object from the coextruded printing strand.

2. The method according to claim 1, wherein said producing a coextruded print flow includes

feeding the two or more substantially immiscible materials into a coextruder aboard a 3D printer.

3. The method according to claim 2, wherein the coextruder is designed and configured to produce a multilayered coextruded printing strand.

4. The method according to claim 2, wherein the coextruder is designed and configured to produce a core portion and an outer shell portion surrounding the core portion.

5. The method according to claim 4, wherein the core portion comprises a structural material and the external portion comprises a bonding material for bonding a later deposit of the coextruded printing strand to an earlier deposit of the coextruded printing strand.

6. The method according to claim 1, wherein said producing a coextruded printing strand includes providing the two or more substantially immiscible materials at corresponding respective flow rates, the method further comprising varying at least one of the flow rates relative to at least one other of the flow rates during said depositing so as to create a varying longitudinal cross- sectional profile within the coextruded printing strand.

7. The method according to claim 6, wherein the 3D object has a physical property that varies from one region to another, wherein said varying the at least one of the flow rates to at least one other of the flow rates causes the physical property to vary.

8. The method according to claim 7, wherein the physical property is stiffness.

9. The method according to claim 7, wherein the physical property is strength.

10. The method according to claim 7, wherein the physical property is density.

11. The method according to claim 7, wherein the physical property is thermal resistance.

12. The method according to claim 7, wherein the physical property is capacitance.

13. The method according to claim 7, wherein the physical property is light-frequency emittance.

14. The method according to claim 1, wherein said producing a coextruded print flow includes

feeding a filament containing the two or more substantially immiscible materials into a heater aboard a 3D printer.

15. A 3D printing system for printing a 3D object, the 3D printing system comprising:

a coextruded-printing-strand generator designed and configured to output a coextruded printing strand having a desired transverse cross-sectional profile composed of two or more substantially immiscible materials, the coextruded-printing-strand generator including: a coextruder designed and configured to coextrude the two or more substantially immiscible materials; and

a nozzle downstream of the coextruder;

wherein the coextruder and nozzle work in conjunction with one another to output the coextruded printing strand;

a printing platform designed and configured to support the 3D object during printing;

a movement system designed and configured to continually change position of the nozzle relative to the printing platform so as to effect 3D printing using the coextruded printing strand; and

a controller in operative communication with the coextruded-printing-strand generator and the movement system so as to control, in response to printer-control instructions, operations of the coextruded-printing-strand generator and the movement system to print the 3D object.

16. The 3D printing system according to claim 15, wherein the coextruded-printing-strand generator includes at least two filament feed systems for feeding at least two differing material in filament form to the coextruder.

17. The 3D printing system according to claim 16, wherein the controller is designed and configured to independently control each of the at least two filament feed systems so as to vary rates at which the at least two filament feed systems feed the at least two differing materials to the coextruder.

18. The 3D printing system according to claim 15, wherein the coextruded-printing-strand generator includes at least two extrusion feed systems for feeding at least two differing materials in extruded form to the coextruder.

19. The 3D printing system according to claim 18, wherein the controller is designed and configured to independently control each of the at least two extrusion feed systems so as to vary rates at which the at least two extrusion feed systems feed the at least two differing materials to the coextruder.

20. The 3D printing system according to claim 15, wherein the coextruder comprises a plurality of layer multipliers in series with one another.

21. The 3D printing system according to claim 20, wherein the coextruder is designed and

configured to generate a multilayer coextruded output strand comprising layers each having a thickness of less than 10 nm.

22. The 3D printing system according to claim 15, wherein the coextruded printing strand has a longitudinal cross-sectional profile, and the coextruded-printing-strand generator is designed and configured to vary the longitudinal cross-sectional profile.

23. The 3D printing system according to claim 22, wherein the coextruded-printing-strand generator includes at least one of a diverter and a valve for varying the longitudinal cross-sectional profile of the coextruded printing strand.

24. The 3D printing system according to claim 22, wherein the controller is designed and configured for controlling, in response to the printer-control instructions, the coextruded-printing-strand generator in a manner that varies the longitudinal cross-sectional profile of the coextruded printing strand.

25. The 3D printing system according to claim 15, wherein the coextruded-printing-strand generator is designed and configured so that the transverse cross- sectional profile of the coextruded printing strand has a core and a shell surrounding the core.

26. The 3D printing system according to claim 25, wherein the coextruded-printing-strand generator is designed and configured so that the core is composed of a single material.

7. The 3D printing system according to claim 25, wherein the coextruded-printing-strand generator is designed and configured so that the core is composed of multiple layers of at least two of the two or more substantially immiscible materials.

Description:
SYSTEMS AND METHODS FOR 3D COEXTRUSION PRINTING

RELATED APPLICATION DATA

[0001] This application claims priority of U.S. Provisional Application Serial No. 62/381,874 filed on August 31, 2016, and titled "3D Coextrusion Printing", which is incorporated by reference herein in its entirety.

FIELD OF THE INVENTION

[0002] The present invention generally relates to the field of 3D printing. In particular, the present invention is directed to systems and method for 3D coextrusion printing.

BACKGROUND

[0003] Three-dimensional (3D) printing is used to make a wide variety of objects, from prototypes to final products or components for prototypes and final products. Challenges exist, however, with printing objects having a property that varies from one region of the object to another region.

BRIEF DESCRIPTION OF THE DRAWINGS

[0004] For the purpose of illustrating the invention, the drawings show aspects of one or more embodiments of the invention. However, it should be understood that the present invention is not limited to the precise arrangements and instrumentalities shown in the drawings, wherein:

FIGS. 1A to ID are transverse cross sections of coextruded print strands of the present disclosure, illustrating examples of different transverse cross- sectional profiles that can be achieved;

FIG. 2 is a partial block diagram/partial diagrammatic view of an exemplary 3D coextrusion printing system made in accordance with the present invention;

FIG. 3 is diagram illustrating components of an exemplary filament-type 3D coextrusion printer, a coextruder of the printer, a portion of an object printed using the printer, and an enlarged detail of several deposited strands of the object;

FIG. 4 is a diagram illustrating an exemplary coextruded-printing- strand generator for creating a multilayer coextruded printing strand;

FIG. 5 is a diagram illustrating an exemplary coextruded-printing- strand generator for creating a nanolayer coextruded printing strand; FIG. 6 is a diagram illustrating an exemplary 3D coextrusion printer capable of generating a micron- scale coextruded printing strand;

FIG. 7 is a diagram illustrating a coextruder + nozzle combination designed and configured to form and output a coextruded printing strand having a rectangular cross-sectional shape;

FIG. 8 is a longitudinal cross section of an exemplary two-material coextruded printing

strand/deposited strand illustrating a gradual longitudinal variation in the compositional profile of strand/strand;

FIGS. 9A to 9C are, respectively, transverse cross sections of the strand/strand of FIG. 8 at, respectively, sections 9A-9A, 9B-9B, and 9C-9C.

FIG. 10 is a longitudinal cross section of an exemplary two-material coextruded printing

strand/deposited strand illustrating an abrupt longitudinal variation in the compositional profile of strand/strand; and

FIGS. 11A to l lC are, respectively, transverse cross sections of the strand/strand of FIG. 10 at, respectively, sections 11 A- 11 A, 11B-11B, and 11C-11C.

SUMMARY

[0005] In one implementation, the present disclosure is directed to a method of forming a 3D object. The method includes producing a coextruded printing strand containing two or more substantially immiscible materials coextruded with one another; and controllably depositing the coextruded printing strand so as to continually build the 3D object from the coextruded printing strand.

[0006] In one implementation, the present disclosure is directed to a 3D printing system for printing a 3D object. The 3D printing system includes a coextruded-printing- strand generator designed and configured to output a coextruded printing strand having a desired transverse cross- sectional profile composed of two or more substantially immiscible materials, the coextruded- printing-strand generator including a coextruder designed and configured to coextrude the two or more substantially immiscible materials; and a nozzle downstream of the coextruder; wherein the coextruder and nozzle work in conjunction with one another to output the coextruded printing strand; a printing platform designed and configured to support the 3D object during printing; a movement system designed and configured to continually change position of the nozzle relative to the printing platform so as to effect 3D printing using the coextruded printing strand; and a controller in operative communication with the coextruded-printing-strand generator and the movement system so as to control, in response to printer-control instructions, operations of the coextruded-printing-strand generator and the movement system to print the 3D object.

DETAILED DESCRIPTION

[0007] In some aspects, the present disclosure is directed to 3D printing using two or more differing, and substantially immiscible, fabrication materials that are coextruded with one another to form a coextruded printing strand used to free-form fabricate, or "print," a 3D object by depositing the coextruded printing strand upon previously deposited strands of the coextruded printing strand or other structure. By virtue of the coextrusion, at any given cross-section the coextruded printing strand has discrete regions of the differing materials, with little to no mixing of the differing materials in immediately adjacent regions. As used herein and in the appended claims, the arrangement of discrete regions of differing materials is referred to as the "cross-sectional profile" of the coextruded printing strand. Two common cross sections are transverse and longitudinal cross sections, which yield corresponding respective "transverse cross-sectional profiles" and

"longitudinal cross-sectional profiles."

[0008] In some embodiments, the coextruded printing strand is formed by feeding two or more substantially immiscible materials into a layer multiplier or a series of layer multipliers to provide a desired number of discrete layers of the differing materials. In one example, two substantially immiscible materials fed into a single doubling-type multiplier as a pair of discrete layers produces a layered flow containing 4 layers of alternating material. Feeding that 4-layer flow into another doubling-type multiplier produces a layered flow containing 8 layers of alternating material, and so on. In some embodiments, the printing-material flow is formed by coextruding a core portion with an outer portion, wherein each of the core portion and outer portion may be composed on one or more materials kept discrete from one another. Fundamentally, there are no limitations on the cross- sectional profile of the coextruded printing strand beyond the ability of any particular configuration to be formed by coextrusion of two or more substantially immiscible materials. It is noted that each layer multiplier can provide any of a variety of multiplication factors, such as 2X, 4X, 6X, etc. In addition, it is noted that in some embodiments each coextruded printing strand can be on the order of about 100 microns in diameter or smallest dimension to a couple of millimeters in diameter or largest dimension. In other embodiments, these dimensions can be smaller or larger. [0009] The overall cross-sectional shape of a coextruded printing strand of the present disclosure may be any shape desired and/or suited to a particular application. For example, the overall cross-sectional shape may be circular, rectangular, triangular, oval, sawtooth on one or more sides, etc. Fundamentally, there are no limitations on the overall cross-sectional shape of a coextruded print flow other than it is able to be coextruded. In addition, coextruded print flows may be, for example, hollow, corrugated, curved, or have any other configuration that can result from coextrusion. A small set of examples of cross-sectional profiles of coextruded printing strands are illustrated in FIGS. 1A to ID.

[0010] FIG. 1A illustrates an exemplary coextruded printing strand 100 having a circular overall transverse cross-sectional shape and a layered transverse cross-sectional profile comprising a plurality of layers 102 (only a few labeled) of differing materials, here, two differing materials represented by different shading. Those skilled in the art will readily appreciate that the layers extend along the length (not shown) of coextruded printing strand 100. FIG. IB illustrates another exemplary coextruded printing strand 110 also having a circular overall transverse cross-sectional shape, but having an "islands in a sea" type transverse cross-sectional profile, here composed of two differing materials arranged in "islands" 112 (only a few labeled) of a first material disposed in a "sea" 114 of a second material. Those skilled in the art will readily appreciate that the islands are actually fiber-like and extend along the length (not shown) of coextruded printing strand 110.

[0011] FIG. 1C illustrates an exemplary coextruded printing strand 120 having a rectangular overall cross-sectional shape and composed of two differing materials, with one of the materials forming a core 122 and the other material forming a shell 124 surrounding the core. While core 122 is shown as composed of a single material, the core may have another transverse cross-sectional profile, such as a layered profile as seen in FIG. ID. In some embodiments, the material of shell 124 may include a material, such as an adhesive or highly cohesive material, that forms a strong bond with one or more already deposited strands (not shown) of coextruded printing strand 120, which may have already at least partially cooled or cured such that deposition of the material of core 122 alone on the one or more already deposited strands may result in a weaker structure.

[0012] FIG. ID illustrates another exemplary coextruded printing strand 130 having a generally rectangular overall transverse cross-sectional shape, but having a plurality of layers 132 (only a few labeled) of two differing materials forming a central portion 134 of the transverse cross-sectional profile of the coextruded printing strand. Coextruded printing strand 130 also includes lateral side portions 136(1) and 136(2) of a third material coextruded with the other two materials. As those skilled in the art will readily appreciate, coextruded printing strand 130 may be used in situations in which it is desired to enhance the lateral face-to-face bonding between already deposited strands (not shown) of the coextruded print strand, which is typically the weakest bonding within a mass of deposited strands. In such situations, the third material of lateral side portions 136(1) and 136(2) may be a material, such as an adhesive or highly cohesive material, that is particularly suited for bonding central portion 134 to an already deposited strand of coextruded printing strand 130.

[0013] As mentioned in the Background section, challenges exist in conventional 3D printing for printing objects having a physical property that varies from one location to another. A 3D printer made in accordance with the present disclosure, however, can be configured to allow for such varying of a physical property. Examples of physical properties of an object that can be varied using a 3D printer made in accordance with the present disclosure include, but are not limited to, stiffness, strength, resiliency, capacitance, and reflectance. The manner in which a physical property can be varied using coextrusion printing techniques of the present disclosure depends on the cross-sectional profile of the coextruded printing strand and the configuration of the coextruder used to create the cross-sectional profile of the coextruded printing strand. Varying the cross-sectional profile of the coextruded printing strand can be accomplished in any one or more of a variety of ways including, but not limited to, varying the relative ratios of the feedstock materials provided to the coextruder, changing the number and/or type of coextrusion devices (e.g., layer multipliers, flow combiners, feedblocks, etc.) used from one segment or region of coextruded printing strand to another, changing the location and/or number of material inputs to the coextruded printing strand within the coextruder, and changing at least one of the materials provided to the coextruder, and any combination thereof, among others.

[0014] As simple illustrations of varying the longitudinal cross-sectional profile of a coextruded printing strand/deposited strand, FIGS. 8 and 10 illustrate, respectively, a coextruded printing strand/deposited strand 800 having a relatively gradual change in longitudinal cross-sectional profile and a coextruded printing strand/deposited strand 1000 having a relatively abrupt change in longitudinal cross-sectional profile. In FIG. 8, the gradual change in profile of coextruded printing strand/deposited strand 800 occurs in a second region 804 between a first region 808 that has relatively more of a Material A than of a Material B to a third region 812 that has relative less of Material A than of Material B. FIGS. 9A to 9C illustrate, respectively, transverse cross-sectional profiles 900, 904 and 908 of coextruded printing strand/deposited strand 800 in first, second, and third regions 804, 808, and 812. It is noted that the coextrusion of Materials A and B could proceed in either direction, i.e., from first region 804 to third region 812 or vice versa. In FIG. 10, the relatively abrupt change in profile of coextruded printing strand/deposited strand 1000 occurs in a second region 1004 between a first region 1008 that has relatively more of a Material A than of a Material B to a third region 1012 that has relative less of Material A than of Material B. Coextruded printing strand 1000 has the additional feature of a third Material C added in three layers 1016(1) to 1016(3) before or after the abrupt change in second region 1004 (depending on the direction of extrusion). Depending on the extrusion direction, layers 1016(1) to 1016(3) can be ended or started by shutting off or turning on a flow of Material C to a suitable layering device (not shown) within the corresponding extruder (not shown). FIGS. 11A to 11C illustrate, respectively, transverse cross- sectional profiles 1100, 1104 and 1108 of coextruded printing strand/deposited strand 800 in first, second, and third regions 1004, 1008, and 1012. Those skilled in the art will readily appreciate that these are two simple examples of changing the longitudinal cross-sectional profile of a coextruded printing strand/deposited strand that are provided for the sake of illustration and not limitation.

[0015] Among many different types of 3D printing processes, fused deposition modeling (FDM) is one of the fastest growing processes that allows for the rapid prototyping of complex geometries by layering filaments of a thermoplastic material extruded from a heated nozzle.

However, the FDM process has several inherent limitations, including: (i) single-material prototypes with limited physical and mechanical properties, (ii) poor surface quality due to a large filament size (-100 um), and (iii) anisotropic properties (i.e., weak z-direction properties). These shortcomings can be addressed by a multi-material 3D coextrusion printing technology disclosed herein.

Nowadays, most new polymeric products contain two or more polymers and functional additives, such as carbon fiber, carbon nanotubes, boron nitride, silicon oxide, etc., to deliver combined properties of each component.

[0016] In contrast to conventional FDM processes, a 3D coextrusion printing process of the present disclosure is a single-step process starting with two or more polymeric and/or hybrid materials that are simultaneously extruded and shaped in a coextruder to form coextruded printing strand having multi-material transverse and longitudinal cross-sectional profiles, such as multilayer profiles having individual layers of nanoscale thickness. This advanced nano-layering is accomplished by using uniquely designed layer-multiplication dies, or "layer multipliers," as described herein. [0017] Developing a next generation 3D printing technology based on the cost effective FDM process with the multi-material nano-layering capability is highly desirable. This new and novel technology can print highly customizable, spatially tunable property prototypes in a relatively short period of time. With this advanced capability in 3D printing, the potential application areas are limitless; for example, a functionally complex part which requires both highly conductive and insulated portions can be printed with this new technology in a continuous manner. Another example is to manufacture a prototype with various portions of different stiffness and modulus within a part. By continuously controlling the ratios of Materials A and B (more materials can be introduced in other embodiments) in the coextruded printing strand, multi-phase nanostructures of functionally tunable materials can be created.

[0018] With general features and aspects described above in mind, reference is now made to FIG. 2, which illustrates an exemplary 3D coextrusion printing system 200 made in accordance with the present invention. In this example, 3D coextrusion printing system 200 includes a printing platform 204 that supports one or more objects (one partially formed object 208 shown for convenience) printed by the printer. Coextrusion printing system 200 also includes a coextruder 212 that feeds a print nozzle 216 that ultimately outputs one or more coextruded print strands 220 that are used to form object 208. Coextruder 212 may be composed of any number of coextrusion devices 212(1) to 212(N), such as feed blocks, flow splitters, layer multipliers, flow diverters, flow combiners, dies, etc. suitable for configuring the cross-sectional arrangement of two or more immiscible materials, such as materials 224(1) to 224(N), input into the coextruder. In some embodiments, coextruder 212 may include a controller 228 that can be used to control the flow of materials 224(1) to 224(N) in the coextruder (e.g., using valves, diverters, etc.), to control configuration of one or more passageways within the coextruder (e.g., by changing the cross- sectional size and/or shape), and/or to control the number of coextrusion devices 212(1) to 212(N) active at any particular time. Those skilled in the art will readily understand that the vast variety and number of coextrusion devices 212(1) to 212(N) that can be used and the vast variety of cross- sectional profiles of coextruded printing strand 220 that can be generated by coextruder 212 makes it impractical to recite even a moderate number of alternatives. Consequently, only a few examples are provided herein for the sake of illustration and not limitation.

[0019] Print nozzle 216 may be configured, typically in conjunction with the configuration of coextruder 212, to provide coextruded printing strand 220 with a desired overall cross-sectional shape, such as any of the shapes mentioned above, to note a few. It is noted that print nozzle 216 may be an outlet of coextruder 212 or it may be a separate structure located downstream of the coextruder relative to coextruded printing strand 220. In some embodiments, nozzle 216 may be located fairly remotely from coextruder 212 and/or connected to a flexible conduit (not shown) that carries coextruded printing strand 220 from the coextruder to the nozzle. Not shown, but which may be needed, are one or more heaters that may be needed to keep coextruded printing strand 220 at the proper temperature for delivery to object 208.

[0020] Materials 224(1) to 224(N) may be provided to coextruder 212 via any suitable material supply system 232(1) to 232(N). For example, each of one or more or all of materials 224(1) to 224(N) may be provided via a corresponding filament of the pertinent material, such that the corresponding supply system 232(1) to 232(N) is a filament supply system. Examples of a filament supply system are illustrated in FIGS. 3 and 6, which are described below. As another example, each of one or more or all of material supply systems 232(1) to 232(N) may be an extruder that receives the corresponding material in a raw form, heats the raw material, and forces it into coextruder 212 in an appropriate molten state. Filament-based material supply systems are generally known as extrusion systems. Therefore, the fundamentals of these systems need not be described herein in detail for those skilled in the art to appreciate these aspects of the present invention.

[0021] In order to effect the printing of object 208, 3D coextrusion printing system 200 includes one, the other, or both of a print-head movement system 236 and a printing platform movement system 240. Print-head movement system 236, if present, moves nozzle 216 and any other component(s) (such as coextruder 212), as may be present, in one or more degrees of freedom, depending on the configuration of 3D coextrusion printing system 200. Printing platform movement system 240, if present, moves a print platform 204 in one or more degrees of freedom, depending on the configuration of 3D coextrusion printing system 200. Following are some examples of versions of 3D coextrusion printing system 200 with and without one or the other of print-head-movement system 236 and printing platform movement system 240.

[0022] In one version of 3D coextrusion printing system 200, only print-head movement system 236 is present, such that printing platform 204 is fixed, and provides movement of nozzle 216 at least along the X, Y, and Z axes. In addition to this three-axis movement, print-head movement system 236 may also be configured to provide additional degrees of freedom, for example, by pivoting nozzle 216 in one or more planes and/or by rotating the nozzle along its outflow axis. In another version of 3D coextrusion printing system 200, only printing platform movement system 240 is present, such that printing nozzle 216 is fixed, and provides movement of printing platform 204 at least along X, Y, and Z axes. In addition to this three-axis movement, printing platform movement system 240 may also be configured to provide additional degrees of freedom, for example, by printing platform 204 in one or more planes and/or by rotating the printing platform about an axis perpendicular to its upper surface (relative to FIG. 2). In yet other versions of 3D coextrusion printing system 200, both print-head movement system 236 and printing platform movement system 240 may be present, for example, with each one providing one or more degrees of freedom that the other one does not. For example, print-head movement system 236 may move print nozzle 216 in the X-Y plane, while printing platform movement system 240 moves printing platform in the Z direction, or vice versa, among other splits of movements.

[0023] Controller 228 may control some or all functions aboard the 3D coextrusion printing system. Relative to printing an object, such as object 208, functions that controller 228 may provide include, but are not limited to, controlling relative location of printing nozzle 216 to object 208, controlling the relative orientation of the print nozzle to the object, controlling the flow rate of coextruded print strand 220, and controlling the cross-sectional profile of the coextruded print strand, with the last-listed one of these being particularly useful when varying a physical property within the object.

[0024] As those skilled in the art will readily appreciate, controller 228 may be responsive to printer-control instructions 244, which may be based on a 3D computer model 248 (e.g., a CAD model) of the object(s) to be printed. 3D computer model 248 includes the geometry of an object and may optionally include a specification of physical properties, including a variation in at least one property in at least one region of the object. Correspondingly, printer-control instructions 244 include instruction for controlling 3D coextrusion printing system 200 to form proper geometry of the object and, if present, to vary the at least one material property according to 3D computer model 248. Controlling the relative location and/or orientation of a print nozzle is known in the art. However, special instructions for varying the cross- sectional profile and/or material makeup of coextruded print strand 220 may be needed and need to account for the specific configuration and operational parameters of 3D coextrusion printing system 200, such as the length of the flow paths from material supply systems 232(1) to 232(N) to the tip of nozzle 216 and the flow rates of materials 224(1) to 224(N) through coextruder 212 and the nozzle, in order to properly form the regions of differing material properties. Those skilled in the art will readily understand the design considerations when designing and assembling these special instructions for a particular version of 3D coextrusion printing system 200.

[0025] In addition to controlling one, the other, or both of print-head movement system 236 and printing platform movement system 240, controller 228 may control coextruder 212 and/or one or more of material supply systems 232(1) to 232(N) so as to effect variation of the cross-sectional profile and/or material makeup of coextruded printing strand 220. For example, if any of material supply systems 232(1) to 232(N) are of the filament feed type, controller 228 may vary the relative ratios among materials 224(1) to 224(N) by varying the feed speed of one or more of the

corresponding respective filaments (not shown), for example, by controlling the speed of a feed motor (not shown). As another example, if any of material supply systems 232(1) to 232(N) are of the extruder type, controller 228 may vary the relative ratios among materials 224(1) to 224(N) by varying the extrusion speed of one or more of the corresponding respective extruders (not shown). Other examples of how controller 228 can vary the cross-sectional profile and/or material makeup of coextruded printing strand 220 include controlling one or more flow valves and/or flow diverters (not shown) within coextruder 212 and/or between material supply systems 232(1) to 232(N) and the coextruder to change the flow(s) of one or more of materials 224(1) to 224(N) within and/or into the diverter. These examples are not meant to be exhaustive but merely exemplary.

[0026] FIG. 3 illustrates a filament-type 3D coextrusion printer 300 that generates a coextruded printing strand 304 composed of two materials, Material A and Material B, arranged into many layers, as seen in the already deposited strands 308 in view 312 and especially in the transverse cross-sectional profiles 316 in enlarged view 320. In this example, each of Materials A and B is provided as a corresponding filament 324A and 324B from a respective spool 328A and 328B to a print head 332 that includes a coextruder 336 and a nozzle 340. Filaments 324A and 324B are heated to an appropriate temperature by one or more heaters 344 at print head 332 so that the corresponding Materials A and B flow properly through coextruder 336 and nozzle 340 and remain suitably immiscible throughout the printing process. In this example, coextruder 336 includes a plurality of layer multipliers 336(1) to 336(6).

[0027] FIG. 4 illustrates an exemplary layer-type coextruded-printing- strand generator 400 for generating a coextruded printing strand 404 composed of multiple micro-scale (i.e., 1 micron to 1000 microns) layers numbering from about two to twelve layers. In the example shown, coextruded printing strand 404 is composed of three layers 404(1) to 404(3) of two differing immiscible materials, Material A and Material B. Coextruded-printing-strand generator 400 comprises a coextruder 408 that includes a feedblock 408A that is fed by a first extruder 412 that provides Material A to the feedblock and a second extruder 416 that provides Material B to the feedblock. It is noted that each of one or both of extruders 412 and 416 can be replaced by another source of material, such as a filament feed system, among others.

[0028] FIG. 5 illustrates another exemplary layer-type coextruded-printing-strand generator 500 for generating a coextruded printing strand 504 composed of nano-scale (i.e., less than 1 micron) layers numbering tens to thousands, each, for example, equat to or less than 10 nm thickness per layer. In the example shown, coextruded printing strand 504 is composed of multiple layers of two differing immiscible materials, Material A and Material B. Coextruded-printing-strand generator 500 comprises a coextruder 508 that includes a plurality of multipliers 508A (only some labeled) and a feedblock 508B that is fed by a first extruder 512 that provides Material A to the feedblock and a second extruder 516 that provides Material B to the feedblock. As seen at the bottom of FIG. 5, coextruder 508 provides the function of providing an initial three-layer feedstrand 520, dividing the feedstrand into divisions 524, stretching the divisions of the feedstrand to create reduced-thickness strands 528, and combining the reduced-thickness strands into coextruded printing strand 504. The number of layer multipliers determines the number of layers in output coextruded printing strand 504. It is noted that each of one or both of extruders 512 and 516 can be replaced by another source of material, such as a filament feed system, among others.

[0029] FIG. 6 illustrates parts of exemplary 3D coextrusion printer 600 made in accordance with the present invention. In this example, 3D coextrusion printer 600 includes a printhead 604, a Z-axis computer numeric control (CNC) machine 608, and a controller 612. In this example, printhead 604 is of a filament type in which the materials to be extruded are provided to the printhead in the form of separate filaments 616(1) and 616(2). Printhead 604 includes a support structure 620 that supports a coextruder + nozzle combination 624 and a pair of feed motors 628(1) and 628(2) that feed, respectively, filaments 616(1) and 616(2) to the coextruder + nozzle combination, here via corresponding guide tubes 632(1) and 632(2). A heater 636 is in thermal communication with coextruder + nozzle combination 624 to melt filaments 616(1) and 616(2) and to keep the respective materials at the appropriate temperature(s) for coextrusion and deposition. Feed motors 628(1) and 628(2) can be operated at differing speeds to vary the relative flow ratio of the two materials in order to vary the cross-sectional composition of the 3D printing strand 640 being coextruded, for example, for the reasons noted above. The operations of feed motors 628(1) and 628(2) may be controlled, for example, by controller 612 or another controller (not shown) aboard 3D coextrusion printer 600. Z-axis CNC machine 608 rigidly supports support structure 620 and moves printhead 604 along the Z-axis during printing. Not shown, but working in conjunction with Z-axis CNC machine 608 during printing is an X-Y stage that is movable along the X and Y axes and provides a print base. Z-axis CNC machine 608 and X-Y stage may be controlled by controller 612.

[0030] FIG. 7 illustrates an exemplary coextruder + nozzle combination 700 that is designed and configured to coextrude, in coextruder 704, two differing input materials (not shown), input into the coextruder via corresponding respective inputs 708(1) and 708(2), and output, via nozzle 712, a coextruded printing strand (not shown) having a rectangular overall transverse cross-sectional shape. In the embodiment shown, coextruder 704 is designed and configured to create a strand (not shown) having a transverse cross- sectional profile composed of 8 layers of A-B alternating layers from A and B materials (not shown) input to the extruder via inputs 708(1) and 708(2). Of course, exemplary coextruder + nozzle combination 700 is provided as an example and should in no way be considered as limiting.

[0031] The foregoing has been a detailed description of illustrative embodiments of the invention. It is noted that in the present specification and claims appended hereto, conjunctive language such as is used in the phrases "at least one of X, Y and Z" and "one or more of X, Y, and Z," unless specifically stated or indicated otherwise, shall be taken to mean that each item in the conjunctive list can be present in any number exclusive of every other item in the list or in any number in combination with any or all other item(s) in the conjunctive list, each of which may also be present in any number. Applying this general rule, the conjunctive phrases in the foregoing examples in which the conjunctive list consists of X, Y, and Z shall each encompass: one or more of X; one or more of Y; one or more of Z; one or more of X and one or more of Y; one or more of Y and one or more of Z; one or more of X and one or more of Z; and one or more of X, one or more of Y and one or more of Z.

[0032] Various modifications and additions can be made without departing from the spirit and scope of this invention. Features of each of the various embodiments described above may be combined with features of other described embodiments as appropriate in order to provide a multiplicity of feature combinations in associated new embodiments. Furthermore, while the foregoing describes a number of separate embodiments, what has been described herein is merely illustrative of the application of the principles of the present invention. Additionally, although particular methods herein may be illustrated and/or described as being performed in a specific order, the ordering is highly variable within ordinary skill to achieve aspects of the present disclosure. Accordingly, this description is meant to be taken only by way of example, and not to otherwise limit the scope of this invention.

[0033] Exemplary embodiments have been disclosed above and illustrated in the accompanying drawings. It will be understood by those skilled in the art that various changes, omissions and additions may be made to that which is specifically disclosed herein without departing from the spirit and scope of the present invention.