System and method for fabricating a three-dimensional (3D) article

Abstract

A three-dimensional (3D) article fabrication system is disclosed. The 3D article fabrication system may include: a hardening liquid supply unit comprising a hardening liquid reservoir in liquid connection with at least one hardening liquid nozzle for injecting an amount of hardening liquid into an environment providing microgravity conditions; and one or more boundary-condition forming elements located in the environment, and comprising a material adherable to a surface of the hardening liquid.

Description

SYSTEM AND METHOD FOR FABRICATING A THREE-DIMENSIONAL(3D) ARTICLECROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority of U.S. Provisional Patent Application No. 63 / 663,144, entitled “SYSTEM AND METHOD FOR FABRICATING A THREE- DIMENSIONAL (3D) ARTICLE”, filed 23 une 2024, the contents of which are all incorporated herein by reference in their entirety.FIELD OF THE INVENTION

[0002] The present invention relates generally to systems and methods of fabricating articles. More specifically, the present invention relates to a systems and methods for three- dimensional (3D) article fabrication.BACKGROUND OF THE INVENTION

[0003] Manufacturing of 3D articles in microgravity conditions (e.g., in orbit, in space, etc.) is extremely challenging As most production methods benefit from gravitational process. Specifically, 3D printing, casting, and the like, rely on a molten material to flow downwards towards a substrate or a mold.

[0004] Conducting other manufacturing processes, such as machining or extrusion, in microgravity conditions, and more specifically in space, is therefore challenging.

[0005] In 2014, NASA together with Made In Space Inc. introduced a 3D printer in the international space station (ISS). However, the 3D printing technologies operated in the ISS were introduced into a manufacturing envelope or, in other words, a box. The size of the box often limits the scale and size of the manufactured elements.

[0006] Accordingly, there is a need for a simple fabrication method for 3D articles, that can be implemented in, and may benefit from, microgravity conditions.SUMMARY OF THE INVENTION

[0007] Some aspects of the invention may be directed to a three-dimensional (3D) article fabrication system. The 3D article fabrication system may include: a hardening liquid supply unit comprising a hardening liquid reservoir in liquid connection with at least one hardeningliquid nozzle for injecting an amount of hardening liquid into an environment providing microgravity conditions; and one or more boundary-condition forming elements located in the environment, and comprising a material adherable to a surface of the hardening liquid.

[0008] In some embodiments, the 3D article fabrication system, further comprising a hardening unit, configured to controllably harden at least a portion of the hardening liquid, to fabricate the 3D article. In some embodiments, the environment may be an immersion liquid, providing neutral buoyancy. In some embodiments, the system further may include an immersion liquid container holding the immersion liquid. In some embodiments, the system may further include a chamber configured to hold the immersion liquid; and an immersion liquid provision unit comprising at least an immersion liquid reservoir. In some embodiments, the immersion liquid provision unit may further include an immersion liquid inlet, in liquid connection to the immersion liquid reservoir, located in the chamber. In some embodiments, the 3D article fabrication system may further include at least two immersion liquid inlets, and wherein one of the at least two immersion liquid inlets is configured to inject immersion liquid into a portion of the hardening liquid inside the chamber, in order to form a hollow 3D article from the hardening liquid.

[0009] In some embodiments, the environment may be selected from an orbit, and a deep space. In some embodiments, the hardening liquid may be selected to have evaporation rate in space to resist the vacuum conditions for at least 5 minutes. In some embodiments, the environment may be a gas in space, and the system may be in a fluid connection with a container holding the gas. In some embodiments, the 3D article fabrication system may further include at least one gas inlet, and wherein the at least one gas inlet is configured to inject gas into a portion of the hardening liquid, thereby inflating a hollow 3D article from the hardening liquid.

[0010] In some embodiments, the one or more boundary condition-forming elements may be elements formed in situ by hardening a portion of the hardening liquid. In some embodiments, the one or more boundary condition-forming elements may be formed prior to at least one of, prior to introducing the initial amount of hardening liquid for forming the 3D article, and as a portion of the 3D article.

[0011] In some embodiments, the one or more boundary condition-forming elements may be prefabricated solid elements selected from, a frame, a wire, a mesh, a rod, a string, a beam, and a strut. In some embodiments, at least one boundary-forming element mayinclude an actuator configured to move at least one boundary-forming element, thereby allowing displacing or deforming of the boundary conditions applied on a surface of the hardening liquid.

[0012] In some embodiments, the hardening liquid may be selected from a polymeric material, alloys having a melting temperature lower than 100 °C, and a phase change material.

[0013] Some additional aspects of the invention may be directed to a method of fabricating of three-dimensional (3D) articles. The method may include: injecting hardening liquid into an environment providing microgravity conditions; providing one or more boundarycondition forming elements into the environment; manipulating a 3D structure of the hardening liquid using the at least one boundary-condition element; and hardening the 3D structure of the hardening liquid to form a solid 3D article.

[0014] In some embodiments, providing may include attaching at least a portion of at least one boundary-condition element to the hardening liquid at at least one point.BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of operation, together with objects, features, and advantages thereof, may best be understood by reference to the following detailed description when read with the accompanying drawings in which:

[0016] Figs. 1A,1B, 1C, and ID are illustrations of article fabrication systems according to some embodiments of the invention;

[0017] Fig. IE is a block diagram of the controllable components of the article fabrication system according to some embodiments of the invention;

[0018] Fig. 2A is a flowchart of a method for fabrication of three-dimensional (3D) articles according to some embodiments of the invention;

[0019] Fig. 2B includes illustration of various steps of the method for fabrication of 3D articles according to some embodiments of the invention;

[0020] Figs. 3A, 3B and 3C show in-process images of an article according to some embodiments of the invention;

[0021] Fig. 3D shows in-process images of another article according to some embodiments of the invention;

[0022] Figs. 4A, 4B, 4C, and 4D show in-process images of an article according to some embodiments of the invention;

[0023] Figs. 5A, 5B, 5C, and 5D show in-process images of another article according to some embodiments of the invention;

[0024] Figs. 6A, 6B, 6C, 6D and 6E show in-process images of a hollow article according to some embodiments of the invention; and

[0025] Figs. 7A, 7B, 7C, 7D and 7E shows images of 3D articles according to some embodiments of the invention.

[0026] It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements.DETAILED DESCRIPTION OF THE PRESENT INVENTION

[0027] One skilled in the art will realize the invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The foregoing embodiments are therefore to be considered in all respects illustrative rather than limiting of the invention described herein. Scope of the invention is thus indicated by the appended claims, rather than by the foregoing description, and all changes that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

[0028] A system and a method according to embodiments of the invention may allow fabricating 3D articles in microgravity conditions. The system is mold-less and therefore, does not require any molds or substrates. The microgravity conditions may be natural microgravity conditions, such as, the ones exist in orbit, or space, or artificial microgravity conditions created by using an immersion liquid, providing neutral buoyancy.

[0029] Such a system and method may allow fabricating either full or hollow 3D articles, and may control the structure of the articles by applying different boundary conditions to the surface of the article during the fabrication method.

[0030] In some embodiments, a hardening liquid may be provided / injected into an environment providing microgravity conditions. The surface of the hardening liquid may be manipulated using one or more boundary-condition forming elements located in theenvironment, during and / or after the inj ection, in order to form the desired 3D article. At the end of the injection / manipulation process, the hardening liquid in the form of the 3D article may be hardened, either naturally (e.g., by drying, natural solidification, natural radiation in space, etc.) or artificially, for example, using UV curing and the like.

[0031] In some embodiments, the term “hardening liquid” refers to one or more fluid(s) capable of undergoing hardening or solidification. In some embodiments, the terms “curable liquid” and “hardening liquid” are used interchangeably. In some embodiments, the hardening liquid is capable of undergoing solidification, so as to result in a solid or a semisolid state. In some embodiments, the hardening liquid is in a solid state upon hardening or solidification. In some embodiments, the hardening liquid is capable of undergoing solidification, so as to substantially reduce its flowability. In some embodiments, the hardening liquid is or comprises a liquid. In some embodiments, the hardening liquid comprises a liquid capable of undergoing curing. In some embodiments, the hardening liquid is in a liquid state. In some embodiments, the hardening liquid comprises a liquid polymer. In some embodiments, the liquid polymer is curable. In some embodiments, hardening liquid is selected from a curable polymeric material, alloys having a melting temperature lower than 100°C, a phase changing material and the like.

[0032] In some embodiments, the hardening liquid is selected to have evaporation rate in space to resist the vacuum conditions for at least 5 minutes. In some embodiments, the hardening liquid is a liquid polymer, a molten metal, a molten glass, and the like.

[0033] In a nonlimiting example, a hardening liquid of the invention may refer to a composition comprising at least one of: a monomer, an oligomer, a polymer or a mixture thereof, wherein the composition is at least partially polymerizable (e.g. via free-radical polymerization) upon exposure to light in the UV and / or visible range. In some embodiments, the hardening liquid is a liquid polymer comprising any methacrylate or acrylate resin which polymerizes upon exposure to UV light. In some embodiments, the polymerization occurs in the presence of a free radical photoinitiator. In some embodiments, the liquid polymer comprises one or more low molecular weight materials, such as methacrylates, dimethacrylates, triacrylates, and diacrylates, or any combination thereof.

[0034] In some embodiments, the hardening liquid may include a photoinitiator, for example, an alpha-cleavage type (unimolecular decomposition process) photoinitiator or a hydrogen abstraction photosensitizer-tertiary amine synergist, operable to absorb UV light,preferably between 200 nm and 400 nm or between 300 nm and 385 nm, to yield free radical(s).

[0035] In some embodiments, the liquid polymer comprises a photopolymer. Some nonlimiting examples of photo-polymerizable molecules comprise: styrene, N- Vinylpyrrolidone, allyl acrylate, diacrylates (such as epoxides, urethanes, ethers, or esters functionalized by acrylate), tetrahydrofurfuryl methacrylate, triethylene glycol dimethacrylate, 2-phenoxyethyl methacrylate, lauryl methacrylate, ethoxylated trimethylolpropane triacrylate, tricyclodecane dimethanol diacrylate, 2- phenoxyethylacrylate, triethylene glycol diacrylate, a monofunctional aliphatic urethane acrylate, polypropylene glycol monomethacrylate, polyethylene glycol monomethacrylate, cyclohexane dimethanol diacrylate, tridecyl methacrylate, tri(meth)acrylates (e.g., 1,1- trimethylolpropane triacrylate or methacrylate, ethoxylated or propoxylated 1,1,1- trimethylolpropanetriacrylate or methacrylate, ethoxylated or propoxylated glycerol triacrylate, pentaerythritol monohydroxy triacrylate or methacrylate, hydroxyethyl methacrylate (HEMA), and tris(2-hydroxy ethyl) isocyanurate triacrylate) or any combination thereof.

[0036] In some embodiments, the surface of the fabricated articles may be substantially smooth, which is the result of the hardening process being held inside the environment providing microgravity conditions. For example, curing a polymer inside the immersion liquid the curable polymer solidified, while maintaining the nature of the Hquid / hquid interface, therefore, obtaining a ver ’ high-quality surface (e.g., optical quality’).

[0037] Reference is now made to Fig. 1A, IB, 1C and ID which are illustrations (perspective views and an exploded view) of an article fabrication systems and to Fig. IE, which is a block diagram of controllable components of the article fabrication system according to some embodiments of the invention. An article fabrication system 100 may include a hardening liquid supply unit 10 comprising a hardening liquid reservoir 15 in liquid connection with at least one hardening liquid nozzle 12 for injecting an amount of hardening liquid 5 into an environment 8 providing microgravity conditions.

[0038] In some embodiments, hardening liquid supply unit 10 may include a pump, a pressurized gas tank, or any other mechanism that may allow injecting a controlled amount of hardening liquid into the environment. In some embodiments, the pump may be selectedfrom, a plunger pump (e.g., a syringe pump), a positive displacement pump, a gear pump, a roots-type pump, a peristaltic pump, and the like.

[0039] In some embodiments, environment 8 is selected from Earth's orbital environment, and deep space environment. In some embodiments, environment 8 may be a container filled with gas (e.g., ISS) traveling in orbit, or in deep space.

[0040] In some embodiments, environment 8 is an immersion liquid, providing neutral buoyancy. In such case, system 100 may further include an immersion liquid container 40 holding the immersion liquid. In some embodiments, system 100 may further include an immersion liquid provision unit 45 comprising at least an immersion liquid reservoir (illustrated in Fig. IE). In some embodiments, container 40 may be placed / held / attached to a base 42, shown in Fig. IB and ID.

[0041] Immersion liquid provision unit 45 may include an immersion liquid pump and an immersion liquid inlet in liquid connection to the immersion liquid reservoir. The immersion liquid inlet may be located inside the immersion liquid container.

[0042] In some embodiments, the amount of immersion liquid is sufficient for immersion of at least one surface of the hardening liquid. In some embodiments, the volume of the immersion liquid is sufficient for providing a buoyancy force to the hardening liquid. In some embodiments, the volume of the immersion liquid is sufficient for contacting the surfaces of the hardening liquid. In some embodiments, the density of the immersion liquid is determined according to a desired topography.

[0043] In some embodiments, the immersion liquid of the invention is characterized by sufficient rheological properties, such as viscosity, suitable for use thereof as an immersion liquid. One skilled artisan will appreciate, that an immersion liquid should enable the formation of the desired topography, and / or geometric shape of the hardening liquid volume immersed therewithin. In some embodiments, the immersion liquid of the invention is characterized by sufficient density so as to enable immersion of the hardening liquid volume in the immersion liquid. In some embodiments, the density of the immersion liquid is set to provide a predetermined buoyancy (e.g. buoyancy sufficient for predefining a curvature of at least one surface of the hardening liquid).

[0044] In some embodiments, the density of the immersion liquid may be set to provide neutral buoyancy conditions. In some embodiments, the density of the immersion liquid is set to provide conditions being within 30%, within 25%, within 20%, within 15%, within10%, within 5%, within 3% deviation from the neutral buoyancy, including any range therebetween. In some embodiments, the immersion liquid of the invention is immiscible with the curable liquid. In some embodiments, the immersion liquid comprises a hydrophilic liquid and the curable liquid is hydrophobic. In some embodiments, the immersion liquid of the invention comprises a lipophilic liquid and the curable liquid is hydrophilic. In some embodiments, the immersion liquid comprises a polar solvent (e.g., ionic aqueous solution). In some embodiments, the immersion liquid of the invention comprises water.

[0045] In some embodiments, the immersion liquid of the invention has a density different from the density of the hardening liquid of the invention. In some embodiments, the density of the immersion liquid is greater than the density of the hardening liquid. In some embodiments, the density of the immersion liquid of the invention is less than the density of the hardening liquid of the invention.

[0046] In some embodiments, the immersion liquid of the invention comprises an aqueous solution. In some embodiments, the immersion liquid of the invention comprises an aqueous solution of a glycol. In some embodiments, the immersion liquid of the invention comprises an aqueous solution of a polyol. In some embodiments, the immersion liquid of the invention comprises glycerol or a mixture of glycerol and water. In some embodiments, the immersion liquid comprises water as a solvent and an additive, such as an organic and / or an inorganic salt (e.g. acetate, carbonate, halide, hydroxide, sulfate, thiosulfate, or bicarbonate salt), an organic water miscible compound (such as glycerin, methanol, ethanol, acetone). In some embodiments, the immersion liquid is chemically stable under curing conditions. In some embodiments, the immersion liquid has a boiling point compatible with the manufacturing conditions. In some embodiments, the immersion liquid is chemically inert with respect to the curable liquid. In some embodiments, the immersion liquid comprises a fluorocarbon oil. Such fluorocarbon oils are immiscible with most other liquids, and can thus serve as an immersion liquid for a variety of curable liquids. The density of the fluorocarbon oils can be controlled by mixing several types of fluorocarbon oils, or by mixing with specific organic compounds that are miscible therewith (e.g. Hexane). Such fluorocarbon oils comprise inter alia perfluoroperhydrophenanthrene, tetradecafluorohexane, methoxyperfluorobutane, 1H,1H,2H,2H-Perfluoro-1 -octanol, Kritox, Fluorinert, Cytop, etc.

[0047] In some embodiments, article fabrication system 100 may further include one or more boundary-condition forming elements 20, 20a, 20b, 20c etc., located in environment 8and comprising a material adherable to a surface of the hardening liquid. Therefore, one or more boundary-condition forming elements 20, 20a, 20b, 20c etc. may be made from a material adherable to a surface of hardening liquid or may be at least partially coated with adhesive adherable to the hardening liquid.

[0048] In some embodiments, boundary-condition forming element 20a may include hardening liquid nozzle 12, as illustrated in Figs 1A and 1C. Accordingly, the hardening liquid may be injected into an environment 8 via an opening in boundary-condition forming element 20a.

[0049] In some embodiments, one or more boundary-condition forming elements 20 may be formed in situ by hardening a portion of the hardening liquid. In such case, an initial amount of hardening liquid may be injected into environment 8. In some embodiments, hardening liquid 5 may be injected from at least one additional hardening liquid nozzle 12, to come in contact with a surface of hardening liquid injected from the former hardening liquid nozzle 12. In some embodiments, these boundary-condition forming elements 20 may be in a liquid state, as discussed with respect to Figs. 5 A-5D and 6A-6E.

[0050] In some embodiments, at least some of boundary-condition forming elements 20 may be hardened, either naturally or by using a hardening unit 30. In such case, one or more boundary condition-forming elements 20 may be formed prior to at least one of, prior to introducing the initial amount of hardening liquid for forming the 3D article, and as a portion of the 3D article. For example, following the hardening of boundary-condition forming element 20, an additional amount of hardening liquid may be injected into the environment in order to form the 3D element, as discussed with respect to Figs. 2B, and 4A-4D.

[0051] In some embodiments, one or more boundary-condition forming elements 20 may be prefabricated solid elements selected from: a frame, a wire, a mesh, a rod, a string, a beam, a strut and the like. A nonlimiting example for such a boundary -forming element 20 is shown in Figs. 1A-1D, 2B, and 3A-3D.

[0052] In the nonlimiting example, shown in Figs. 1A-1D, and 2B boundary-forming elements 20, 20a, 20b, and 20c are rounded truncated cones, configured to be adhered to the surface of hardening liquid 5. In some embodiments, at least some of boundary -forming elements 20, 20a, 20b, and 20c may include gas inlets allowing for the introduction / inj ection of gas / immersion liquid after or during the injection of hardening liquid 5, in order to form hollow shapes, as discussed with respect to Figs. 4A-4D and 6A-6E.

[0053] In some embodiments, boundary-forming elements 20, 20a, 20b, and 20c may include a surface pattern, or a structure that may form a connecting area / element that may allow the final object (e.g., article 6 illustrated in Fig. 2B) to be connected to external components / elements. For example, boundary-forming elements 20, 20a, 20b, and 20c may include pattern for forming: a thread (e.g., for a screw), a clip, a press stud, a snap and the like.

[0054] In some embodiments, system 100 may include at least one holder 25 for holding one or more boundary -forming elements 20, 20a, 20b, and 20c, as illustrated in Fig. IB. Holder 25 may hold boundary-forming elements 20, 20a, 20b, and 20c in a symmetrical configuration (as illustrated), or in an asymmetrical configuration. In some embodiments, boundary -forming elements 20, 20a, 20b, and 20c may be fixed to holder 25. Alternatively, boundary -forming elements 20, 20a, 20b, and 20c may be configured to move along holder 25 (e.g., slide) by, for example, an actuator.

[0055] In some embodiments, system 100 may further include an actuator 60, shown in Fig. ID, configured to move at least one boundary-forming element 20, thereby allowing displacing or deforming of the boundary conditions applied on a surface of the hardening liquid.

[0056] In some embodiments, a controller 50, shown in Fig. IE, may control the movement of one or more boundary-condition forming elements 20 based on a predetermined scheme in order to form the 3D article. In some embodiments, actuator may be or may include, at least one of: a robotic arm (as illustrated), an arm attached to an XY table, an electrical motor and a gear unit, a hydraulic motor and a gear unit, a pneumatic motor and a gear unit, and the like. Actuator 60 may include one or more connectors for holding one or more boundarycondition forming elements 20. In some embodiments, boundary-condition forming element 20 may be held by a single arm. Additionally or alternatively, two or more boundarycondition forming elements 20 may be held by a single arm.

[0057] In the nonlimiting example of Fig. ID actuator 60 is a robotic system is a 6-degree- of-freedom robotic arm. One or more boundary-condition forming elements 20 may be connected to an end effector 65 of the robotic arm.

[0058] Article fabrication system 100 may further include a hardening unit 30, configured to controllably harden at least a portion of the hardening liquid, to fabricate the 3D article. In some embodiments, when hardening liquid 5 is a curable polymer, hardening unit 30 mayinclude one or more lamps 32 for providing light in the UV and / or visible range. For example, hardening liquid 5 may emit UV light, between 200 nm and 400 nm or between 300 nm and 385 nm, and the like. Some nonlimiting examples for hardening unit 30 may include an array of light-emitting-diodes (LEDs), discharge lamps, halogen lamps, and incandescent light bulbs and the like. Alternatively, hardening unit 30 may be a drying cabinet, a cooler, and the like.

[0059] In some embodiments, system 100 may further include a hardening sphere 35 illustrated in Fig. IB and ID. Hardening sphere 35 may include a plurality of hardening units 30 (for example, a plurality of Light-Emitting-Diodes (LEDs)). In a nonlimiting example, each LED may be covered by a baffle such that hardening liquid 5 is not illuminated directly by the light sources and instead receives light that has been diffused by sphere 35. When integrated into a robotic system, as illustrated in Fig. ID, hardening sphere 35 may have a notch 36 allowing end effector 65 holding boundary-condition forming elements 20 to move, while encompassing hardening liquid 5. In some embodiments, hardening sphere 35 may include two parts, a lower part 35 attached to base 42 and an upper part covering the lower part.

[0060] In some embodiments, system 100 may include an additional hardening unit 34, illustrated in Fig. 1C, that may be configured to harden (e.g., cure) predefined portions of the hardening liquid, while maintaining the rest of hardening liquid unhardened (e.g., uncured). For example, hardening unit 34 may be controlled to direct a light beam (e.g., in the UV range) to specific locations in or on hardening liquid 8. Therefore, hardening unit 34 may cause only this portion to harden, thereby forming in situ, boundary-condition forming element 20. This boundary-condition forming element 20 may be included in the final 3D article, or may be removed from the 3D article.

[0061] In some embodiments, at least one of boundary -forming elements 20, 20a, 20b, and 20c may be left and included in the final 3D article. In some embodiments, additional elements may be included in the final 3D article. These boundary-forming elements, or additional elements, may be introduced into the environment prior to the hardening process, or may be glued or attached to the final 3D article following the hardening. In a nonlimiting example, the boundary-forming elements 20, 20a, 20b, and 20c or the additional elements, may be embedded in the hardening liquid, in order to connect all connection points / connectors to the final 3D article, and / or to add mechanical rigidity. In such cases,boundary-forming elements 20, 20a, 20b, and 20c, and / or the additional elements, may include fiber-reinforced polymers for structural rigidity.

[0062] Article fabrication system 100 may further include a controller 50, illustrated in Fig. IB, configured to control components of system 100, for example, hardening liquid supply unit 10, one or more boundary-condition forming elements 20, and hardening unit 30.

[0063] Controller 50 may include a processor 52 that may be, for example, a central processing unit (CPU) processor, a chip or any suitable computing or computational device. Processor 52 (or one or more processors, possibly across multiple units or devices) may be configured to carry out methods described herein, and / or to execute or act as the various modules, units, etc. More than one computing controller 52 may be included system 100 according to embodiments of the invention.

[0064] Controller 50 may include a memory 54 that may be or may include, for example, a Random Access Memory (RAM), a read only memory (ROM), a Dynamic RAM (DRAM), a Synchronous DRAM (SD-RAM), a double data rate (DDR) memory chip, a Flash memory, a volatile memory, a non-volatile memory, a cache memory, a buffer, a short term memory unit, a long term memory unit, or other suitable memory units or storage units. Memory 154 may be or may include a plurality of possibly different memory units. Memory 54 may be a computer or processor non-transitory readable medium, or a computer non- transitory storage medium, e.g., a RAM. In one embodiment, a non-transitory storage medium such as memory 54, a hard disk drive, another storage device, etc. may store instructions or code which when executed by a processor may cause the processor to carry out methods as described herein.

[0065] Memory 54 may be stored thereon, at least one of: an operating system, an executable code, and a database according to some embodiments of the invention.

[0066] Controller 50 may further include a communication unit 56 that may include one or more input and output devices. For example, the input devices may be or may include any suitable input devices, components or systems, e.g., a detachable keyboard or keypad, a mouse and the like. In another example, the output devices may include one or more (possibly detachable) displays or monitors, speakers and / or any other suitable output devices. Any applicable input / output (VO) devices may be connected to controller 150. For example, a wired or wireless network interface card (NIC), a universal serial bus (USB) device or external hard drive may be included in the input devices and / or the output devices.

[0067] In some embodiments, may further include at least one sensor 55. Sensor 55 may be a pressure sensor, a flowmeter, a thermometer, a wavefront sensor, a 3D scanner, a light intensity meter and the like. In some embodiments, the 3D scanner (e.g., a wavefront sensor) is configured to measure the shape of the final article. In some embodiments, the intensity meter may measure the UV radiation.

[0068] In some embodiments, system 100 may further include a gas provision system (not illustrated) comprising a gas reservoir and at least one gas inlet configured to inject gas into a portion of the hardening liquid, for example, for inflating a hollow 3D article of the hardening liquid.

[0069] Reference is now made to Fig. 2A which is a flowchart of a method of fabricating 3D articles and to Fig. 2B which include illustrations of some of the method steps, according to some embodiments of the invention. The method may be performed by system 100 under the supervision of controller 50.

[0070] In step 210, the method may include injecting hardening liquid into an environment providing microgravity conditions. For example, controller 50 may control hardening liquid supply unit 10 (e.g., a pump) to inject a predetermined amount of hardening liquid 5 into environment 8. In some embodiments, environment 8 may be space, a gas held in a container in orbit (e.g., in a space station), or may be an immersion liquid held in container 40 on earth configured to provide neutral buoyancy.

[0071] In step 220, the method may include providing one or more boundary-condition forming elements into the environment. For example, controller 50 may control an actuator to move at least one solid boundary-condition forming element 20 to approach specific point / points on the surface of hardening liquid 5. In yet another example, controller 50 may control hardening liquid supply unit 10 to provide an amount of hardening liquid 5, and further control hardening unit 30 to harden the amount of hardening liquid 5 in order to form boundary-condition forming element 22. In such a case, boundary-condition forming element 22 may be formed using boundary-condition forming element 20 combined with injection nozzle 12. Boundary-condition forming element 22 may be hardened and used for altering the boundary-condition of an additional amount of hardening liquid 5.

[0072] In yet another example, controller 50 may control hardening unit 30 to harden a portion of the hardening liquid injected at step 210, to form boundary-condition forming element 20 as illustrated and discussed with respect to Figs. 4A-4D. In such cases, boundary-condition forming element 20 may be part of the final 3D object or may be removed from the final 3D object.

[0073] In some embodiments, providing the one or more boundary-condition forming elements into the environment may include, in step 230, attaching at least a portion of at least one boundary-condition element to the hardening liquid at at least one point. For example, controller 50 may attach boundary-condition forming element 20 the specific point on the surface of hardening liquid 8. In some embodiments, the specific point may be selected according to the required final shape of the 3D object. Some nonlimiting examples of such objects are given in the images in Figs. 7 A to 7E.

[0074] In step 240, the method may include manipulating a 3D structure of the hardening liquid using the at least one boundary-condition element 20 or 22. For example, controller 50 may control an actuator to move at least one boundary-condition element 20 to alter the surface of the hardening liquid (e.g., steps 240 and 240A in Fig. 2B), such that, for example, a yoyo or a wine-glass are formed, as shown in Fig. 5A. In some embodiments, controller 10 may further control hardening liquid provision unit 10 to extract some of the hardening liquid in order to further alter the shape of a final article 6, as illustrated in step 240B in Fig. 2B.

[0075] In some embodiments, controller 50 may control hardening unit 30 to partially harden a portion of the hardening liquid, to form at least one boundary-condition element 20, and then move the at least one boundary-condition element 20 inside an immersion liquid to form a final flower structure as shown in Figs. 4A-4D and Fig. 7B.

[0076] In some embodiments, the method may include forming hollow a 3D article. Accordingly, prior to, during or after step 240, the method may include injecting one of, immersion liquid or gas into the hardening liquid to form a solid hollow 3D article, as shown in Figs. 6A to 6D. For example, when the environment is in far space, in orbit or gas held in a tank in space, the method may include injecting gas, form the gas provision unit, to one or more specific location in the hardening liquid to form voids. In yet another example, if the environment is an immersion liquid, the method may include injecting additional immersion liquid, from immersion liquid inlet, in one or more specific location in the hardening liquid to form voids in the hardening liquid (e.g., filled with immersion liquid).

[0077] In step 250, the method may include hardening the 3D structure of the hardening liquid to form a solid 3D article. For example, controller 50 may control hardening unit 30to provide UV radiation in order to cure, the hardening liquid, or at least the portion of the hardening liquid left unhardened. Alternatively, controller 50 may control a dryer to dry the hardening liquid, a cooler to cool down a molten hardening liquid, or simply may leave hardening liquid to naturally solidify.

[0078] In some embodiments, the method may further include, separating at least one boundary-condition element 20 from the article, using any known method, for example, sowing, machining, laser cutting, and the like. In some embodiments, at least a portion of at least one boundary-condition element 20 may remain a part of the 3D article.

[0079] Reference is now made to Figs. 3 A, 3B and 3C which show in-process images of an article according to some embodiments of the invention. Fig 3 A shows step 210 at which hardening liquid 5 was injected into an immersion liquid environment. Fig. 3B shows steps 220 and 230 at which two solid boundary-condition forming elements 20 are introduced into the immersion liquid and attached to the surface of hardening liquid 5. Fig. 3C shows the structural outcome of the manipulation of the two solid boundary-condition forming elements. The hardening liquid 5 of Fig. 3C was then cured using a UV source to produce the 3D article. The boundary-condition forming elements 20 were cut from the final article.

[0080] Reference is now made to Fig. 3D which includes in-process images of another article according to some embodiments of the invention. In the nonlimiting example of Fig. 3D, an initial amount of hardening liquid 5 may be injected into an immersion liquid and may come into contact with three boundary-condition elements 20a, 20b, and 20c. During the following steps a constant amount / volume of hardening liquid 5 is maintained, therefore the total volume of the various forms remains constant along the steps. The shape of the final object 6 is received by manipulating the locations of boundary condition elements 20a, 20b, and 20c. As shown, boundary condition elements 20a, 20b, and 20c may move toward or away from the center of the immersion liquid cylindrical tank (depicted with black arrow). Hardening liquid 5 may be transformed as a result of each movement on boundary condition elements 20a, 20b, and 20c. resulting in the “Napoleon” hat article 6 shown.

[0081] Reference is now made to Figs. 4A, 4B, 4C and 4D which show in-process images of another article according to some embodiments of the invention. In the process shown in Figs. 4A-4D, the boundary-condition forming elements are formed from the hardening liquid and remine part of the final article. Fig. 4A shows step 210 at which hardening liquid was injected into an immersion liquid environment. The hardening liquid was injected suchthat a hollow “bubble- like” shape was made. Fig. 4B shows steps 220 and 230 at which boundary-condition forming element 20 is formed by partially curing the upper part of the hardening liquid (indicated by arrows). Fig. 4C shows the volumetric manipulation conducted by moving boundary-condition forming element 20 thereby decreasing the volume of the “bubble-like” shape. Fig. 4B shows the end of the manipulation. The article lost it’s “bubble-like" shape and a “flower-like” shape immerged. The “flower-like” shape was hardened using UV curing.

[0082] Reference is now made to Figs. 5 A, 5B, 5C, and 5D, which show in-process images of another article according to some embodiments of the invention. In the process shown in Figs. 5A-5D, boundary condition elements 22 are all made from hardening liquid 5, and are injected together. Hardening liquid 5 is injected from 3 boundary condition elements 20 surfaces. Each one of the injected hardening liquids 5 may act as a boundary condition element 22 to the other injected hardening liquids 5. As shown in the nonlimiting example of Figs 5C and 5D, three spheres 22 coalesce, creating a single continuous shape.

[0083] Reference is now made to Figs. 6A, 6B, 6C, 6D, and 6E, which show in-process images of a hollow article according to some embodiments of the invention. In a similar process to the one discussed above with respect to Figs. 5 A-5D, 3 spheres of hardening liquid may be injected and expanded by injecting gas / immersion liquid in order to form 3 hollow spheres. Each hollow sphere may act as a boundary condition element 22 to the other hollow spheres. The final hollow article 6 is shown in Fig. 6E.

[0084] In some embodiments, the objects formed using the process shown in Figs. 2B, 5A- 5B, and 6A-6B, may be used as connectors when an asymmetrical connection between elements is required. For example, in architecture, such asymmetrical connectors may allow designing buildings and constructions that are unique and cannot be constructed otherwise.

[0085] Reference is now made to Figs. 7A, 7B, 7C, 7D, and 7E which show images of final 3D articles fabricated using system 100 and the method of Fig. 2. All the articles were fabricated in an immersion liquid composed of glycerol in water, providing neutral buoyancy. Fig. 7A shown the fabrication of a yoyo toy and a glass of wine from UV resin VidaRosa™ J-2D-UVDJ250G, Dongguan, China. Fig. 7B a toilet made from the same polymer. Fig. 7C and 7B were made using in situ boundary-condition forming element 20, as discussed with respect to Figs. 4A-4B. The articles in Figs. Fig. 7C and 7B were made from the same polymer.

[0086] Articles 6 in Fig. 7E are asymmetrical connectors as discussed above.

[0087] Unless explicitly stated, the method embodiments described herein are not constrained to a particular order or sequence. Furthermore, all formulas described herein are intended as examples only and other or different formulas may be used. Additionally, some of the described method embodiments or elements thereof may occur or be performed at the same point in time.

[0088] While certain features of the invention have been illustrated and described herein, many modifications, substitutions, changes, and equivalents may occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.

[0089] Various embodiments have been presented. Each of these embodiments may of course include features from other embodiments presented, and embodiments not specifically described may include various features described herein.

Claims

CLAIMS1. A three-dimensional (3D) article fabrication system, comprising: a hardening liquid supply unit comprising a hardening liquid reservoir in liquid connection with at least one hardening liquid nozzle for injecting an amount of hardening liquid into an environment providing microgravity conditions; and one or more boundary-condition forming elements located in the environment, and comprising a material adherable to a surface of the hardening liquid.

2. The 3D article fabrication system of claim 1, further comprising: a hardening unit, configured to controllably harden at least a portion of the hardening liquid, to fabricate the 3D article.

3. The 3D article fabrication system of claim 1 or claim 2, wherein the environment is an immersion liquid, providing neutral buoyancy.

4. The 3D article fabrication system of claim 3, wherein the system further comprises an immersion liquid container holding the immersion liquid.

5. The 3D article fabrication system of claim 3, wherein the system further comprises: a chamber configured to hold the immersion liquid; and an immersion liquid provision unit comprising at least an immersion liquid reservoir.

6. The 3D article fabrication system of claim 5, wherein the immersion liquid provision unit further comprises an immersion liquid inlet, in liquid connection to the immersion liquid reservoir, located in the chamber.

7. The 3D article fabrication system of claim 6, comprising at least two immersion liquid inlets, and wherein one of the at least two immersion liquid inlets is configured to inject immersion liquid into a portion of the hardening liquid inside the chamber, in order to form a hollow 3D article from the hardening liquid.

8. The 3D article fabrication system of claim 1, where in the environment is selected from an orbit, and a deep space.

9. The 3D article fabrication system of claim 8, wherein the hardening liquid is selected to have evaporation rate in space to resist the vacuum conditions for at least 5 minutes.

10. The 3D article fabrication system of claim 8, wherein the environment is a gas in space, and the system is in a fluid connection with a container holding the gas.

11. The 3D article fabrication system of any one of claims 8 to 10, further comprising at least one gas inlet, and wherein the at least one gas inlet is configured to inject gas into a portion of the hardening liquid, thereby inflating a hollow 3D article from the hardening liquid.

12. The 3D article fabrication system according to any one of claims 1 to 11, wherein the one or more boundary condition-forming elements are elements formed in situ using at at least a portion of the hardening liquid.

13. The 3D article fabrication system of claim 12, wherein the one or more boundary condition-forming elements comprise hardening liquid injected via at least one additional hardening liquid nozzle.

14. The 3D article fabrication system of claim 12 or 13, wherein the one or more boundary condition-forming elements are formed prior to at least one of, prior to introducing the initial amount of hardening liquid for forming the 3D article, and as a portion of the 3D article.

15. The 3D article fabrication system according to any one of claims 1 to 9, wherein the one or more boundary condition-forming elements are prefabricated solid elements selected from, a frame, a wire, a mesh, a rod, a string, a beam, and a strut.

16. The 3D article fabrication system according to any one of claims 1 to 15, wherein at least one boundary-forming element comprises an actuator configured to move at least one boundary-forming element, thereby allowing displacing or deforming of the boundary conditions applied on a surface of the hardening liquid.

17. The 3D article fabrication system according to any one of claims 1 to 16, wherein the hardening liquid is selected from a polymeric material, alloys having a melting temperature lower than 100 °C, and a phase change material.

18. A method of fabricating of three-dimensional (3D) articles, comprising:injecting hardening liquid into an environment providing microgravity conditions; providing one or more boundary-condition forming elements into the environment; manipulating a 3D structure of the hardening liquid using the at least one boundary-condition element; and hardening the 3D structure of the hardening liquid to form a solid 3D article.

19. The method of claim 18 wherein providing comprises attaching at least a portion of at least one boundary-condition element to the hardening liquid at at least one point.

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