Systems for negative 3D printing machine at high resolution

Abstract

Methods and apparatus for the fabrication of solid three-dimensional objects from liquid polymerizable materials at high resolution. A material is coated on a film non-digitally, excess material is removed digitally, by laser, leaving an image of a layer to be printed, and the image is then engaged with existing portions of an object being fabricated and exposed to a non-digital UV curing light source. Since the only part of the process that is digital is the material removal, and this part is done by laser, the speed of printing and the robustness of the manufacturing process is improved significantly over conventional additive or 3D fabrication techniques.

Claims

1. A system, comprising a coating system configured to coat a substrate with a uniform layer of liquid polymerizable material and provide the coated substrate to a negative printing unit, the negative printing unit configured to remove portions of the liquid polymerizable material from the coated substrate and provide a resulting version of the coated substrate with remaining segments of the liquid polymerizable material to a sample building unit that is spatially separated from the negative printing unit, the sample building unit configured to engage the coated substrate with the remaining segments of the liquid polymerizable material that represents an image of a layer of an article under fabrication with a sample and cure said remaining segments of the liquid polymerizable material with ultra-violet (UV) light when the remaining segments of the liquid polymerizable material are in contact with the sample.

2. The system of claim 1, wherein the coating system includes one of: a screen-printing module configured to coat the liquid polymerizable material on a screen or stencil of film with well-defined holes using a blade or a squeegee, and further to subsequently transfer the liquid polymerizable material to the substrate in a soft or hard engage; a dispenser configured to print the liquid polymerizable material onto the substrate; an inkjet head configured to print the liquid polymerizable material onto the substrate; a gravure or micro-gravure system configured to coat the substrate with the uniform layer of the liquid polymerizable material; a slot-die system configured to coat the substrate with the uniform layer of the liquid polymerizable material; a roller coating system configured to coat the substrate with the uniform layer of the liquid polymerizable material; and a syringe of the liquid polymerizable material, a pump that drives the liquid polymerizable material from the syringe onto the substrate, and an actuator which is configured to transport the coated substrate towards and through a gap between rollers or knifes to create the uniform layer of the liquid polymerizable material on the substrate with a thickness that is defined by the gap.

3. The system of claim 2, wherein the coating system is inside a closed cell with a controlled environment.

4. The system of claim 2, wherein the coating system is configured to coat the substrate with more than one liquid polymerizable material.

5. The system of claim 2, wherein the coating system includes the gap and is configured to translate the substrate bidirectionally through the coating system while adjusting a width of the gap.

6. The system of claim 2, wherein the liquid polymerizable material is a UV light curable material.

7. The system of claim 2, wherein the negative printing unit is a laser-based system that contains a laser configured to jet material from the coated substrate to a material reuse system.

8. The system of claim 2, wherein the substrate is one of: a continuous transparent film substrate, a transparent film substrate coated by a metal layer, or a transparent film substrate coated by a metal layer and a dielectric layer.

9. The system of claim 2, further comprising a support material addition unit configured to inject support material on the sample.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention is illustrated by way of example, and not limitation, in the figures of the accompanying drawings, in which:

(2) FIG. 1 illustrates, in overview form, an embodiment of the invention, which includes coating a film with a material, removing excess material into a recovery system, and then exposing the coated film to a non-digital curing system (UV or heat based) during contact with the sample, thereby reducing waste and eliminating the need for support material.

(3) FIG. 2 illustrates schematically a system configured in accordance with one embodiment of the invention, highlighting a coating process, negative printing with a material recovery unit, and curing during contact with a sample; an optional sample release unit is also shown.

(4) FIGS. 3a-3m illustrate aspects of a process in accordance with an embodiment of the present invention, including negative jetting of a material (FIG. 3a-3c) with optional initial curing (FIG. 3d), sample contact (FIG. 3e-3f), curing (FIG. 3g), a release process (FIG. 3h-3j), sample surface cleaning (FIG. 3k), and the overall result and structure (FIG. 3l-3m).

(5) FIG. 4 illustrates an example of a system configured in accordance with present invention, with reels and rollers for coating a material on a film and moving the film through a laser jetting unit towards sample contact during exposure to UV light for curing.

(6) FIG. 5 illustrates a further example of the system shown in FIG. 4, with several layers having been printed.

(7) FIG. 6 illustrates yet a further example of the system shown in FIG. 4, with several layers having been printed with the optional addition of a support material between layers.

(8) FIG. 7 illustrates yet a further example of the system shown in FIG. 4, with several layers having been printed and including a support addition system configured for injection of the support material.

(9) FIGS. 8a and 8b illustrate aspects of an embodiment of the invention in which multiple materials are used during printing, both before (FIG. 8a) and after (FIG. 8b) contact with the sample.

(10) FIGS. 9a and 9b illustrate aspects of an embodiment of the invention in which printing uses an anti-sticking foil to prevent sample distortion during curing (FIG. 9a) and sample release (FIG. 9b) processes.

(11) FIG. 10 illustrates aspects of an embodiment of the invention in which printing includes using a mechanical release system to enable fast and accurate sample building.

(12) FIG. 11 illustrate aspects of an embodiment of the invention in which printing includes using a material recovery system to reduce the waste of excess material during sample building.

DESCRIPTION OF THE INVENTION

(13) The present invention concerns methods and apparatus for the fabrication of solid 3D objects from liquid polymerizable materials at high resolution. In one embodiment, a system configured in accordance with the invention employs laser jetting of a negative image of an initial coated film by polymerizable liquid at a high resolution, and exposure of the image to a corresponding light source during contact between the film and a sample to produce the sample's next layer. Since this is a continuous sequence production process, the rate of 3D object formation and its versatility is improved over conventional 3D printing processes. Before describing the invention in detail, however, it is helpful to present an overview. FIG. 1 provides such an overview, illustrating several constituents of a system 100 configured in accordance with the invention: coating a film with a material 10, removal of excess material into a recovery system 12, and exposure of the coated film to a non-digital curing system (UV or heat based) during contact with a sample 14.

(14) By working with the negative picture of the desired image several important key features of the current invention are revealed: First, any excess of material resulting from the coating process can be reused, and no significant waste is produced during the sample building process. Second, the need for support material is eliminated (although as discussed below, use of supporting material remains an option). The negative picture is supported by the film from its top side during the curing and contact, thereby eliminating the need for supporting material in most instances. There are some structures that may require or benefit from additional support, and so the present invention accommodates such options. Third, systems configured in accordance with the present invention have the ability to print at a very high rates since the jetting and building take place in two different areas and those process can be performed simultaneously. The main constraint on printing speed is either the curing process or the negative printing time, but timings of these individual processes are not additive, meaning that the overall print speed is not limited by an additive combination of the curing time and the negative printing time. There are also fewer limitations for the UV light source used in curing than in conventional 3D printing processes, since the curing process is not digital.

(15) The negative printing unit can be a laser assisted deposition/laser dispensing system with a pulsed laser having enough energy to jet the negative image of the material from the film surface to the recovery unit. The laser can be a UV, IR, CO.sub.2, or any other laser.

(16) If the printing unit is a laser assisted deposition/laser dispensing system, a uniformly coated substrate has an important role in the robustness of the system. Therefore, an additional coating system is added before the printing unit. This coating system can be a traditional coating system, like a coating system based on micro gravure or slot die coater or a roller coating system. It can also be a screen-printing based coating system, a dispenser, or an inkjet system. In one embodiment of the invention, the coating system can be based on a syringe and gap system as shown in FIG. 4. In such a system 400, material 402 is dispensed from a syringe 404 to a substrate 406 (e.g., by an air or mechanical pump that drives the material from the syringe onto the substrate) and the coated substrate 408 is moved (e.g., by motor-driven rollers or other actuators) towards and through a well-defined gap 410. The gap can be defined by blades or other kind of barrier, as shown in FIG. 4, or by two cylinders (e.g., rollers) spaced close together.

(17) After passing through the gap 410, a uniform layer 412 of material is formed on the substrate and the laser assisted deposition/laser dispensing system 414 can jet material from the coated substrate to a material recovery system. From the laser assisted deposition/laser dispensing system 414, the coated substrate 416 is passed to the curing station 418, where it is brought into contact with a receiving substrate 420 in the presence of a UV light and/or heat, thereby curing the material to form a new layer of the article being fabricated.

(18) In other embodiments of the invention, the coating system may include a screen-printing module where the printed substrate is coated on a screen or stencil of film with well-defined holes and, using a blade or a squeegee, the material is transferred to a substrate in a soft or hard engage. Alternatively, the coating system may include a dispenser or an inkjet head to print the material onto a carrier substrate. Or the coating system may be a gravure or micro-gravure system that coats a substrate with a highly uniform layer of material. In still further embodiments of the invention, the coating system may be a slot-die system that coats a substrate with a highly uniform layer of material. Or the coating system may be a roller coating system that coats a substrate with a highly uniform layer of material.

(19) In any of these and/or other embodiments of the invention, the coating system may be disposed inside of a closed cell with a controlled environment (temperature, pressure, etc.) to prevent evaporation of solvent from the printed material or to prevent material oxidation, thereby helping to prolong the pot life of the material.

(20) In some embodiments of the invention, the coating system contains more than one material. This creates the possibility for printing a plurality of materials onto an intermediate substrate (e.g., a film such as substrate 406 in FIG. 4) in a controlled sequence, making it possible to print more than one material onto a final substrate (e.g., receiving substrate 420 in FIG. 4).

(21) In one embodiment of the invention, the intermediate substrate of the coating system is translatable forwards and backwards (from the standpoint of applying material to the intermediate substrate) in a controlled manner, while opening the gap between the coater rollers, creating the possibility for recoating the same area of the intermediate substrate with the printed material multiple times without contamination to the rollers. Such a process also reduces (or eliminates) the amount of intermediate substrate consumed during the initial printing process, preventing waste.

(22) In some embodiments, after a current uniform layer of material coated on the intermediate substrate has been consumed (fully or partially) by printing in the printing unit, the intermediate substrate may loop back to the coating system for recoating or translate back to the coating system for application of a new uniform coated layer for the next printing process.

(23) The film (or other intermediate substrate) used for printing can be a substrate that is transparent at the laser wavelength with or without a metal (or other) coating. Examples of such a film (substrate) are PET, BOPP, PI, etc. The film may be coated with a metal or polymer coating with additive(s) that adsorb at the laser wavelength and create transparent areas digitally with exposure to the laser negative jetting system.

(24) Among the materials for printing that may be used in systems configured in accordance with the invention are any liquid or paste materials. However, the benefits of the present systems are chiefly present when highly viscous materials that cannot be printed properly in high resolution by other methods are employed. For example, UV-/visible light-cured material formulations and UV-cured monomers and polymers of viscose or sensitive materials can be printed using systems configured in accordance with the invention. Other materials that can be printed with systems configured in accordance with the invention are acrylates, epoxies, urethanes, adhesives, pastes, and inks using either UV curing or heat curing. Still further materials that can be printed with systems configured in accordance with the invention are UV-cured monomers and polymers with additives such as ceramics, metals, organic additives, fiber reinforcement, etc. Also, materials such as UV-cured waxes, low or high viscosity materials that are cured or even partially cured by light, epoxy based, urethane based, or silicone family materials with or without UV curable ends, where the reaction is initiated by heat or other catalyst (Pt, OH, etc.), ceramic and metal pastes, and solder pastes, bio-compatible materials, and thermoplastic materials (at room temperature or at elevated temperatures with adjustment of the environment temperature) can all be printed with systems configured in accordance with the invention. Possible basic formulations and mechanisms can use monomers and polymers of acrylate, epoxy, urethane, or other UV or light sensitive materials with a light sensitive initiators or/and co-initiators or sensitizers, for example: acetophenones, thioxanthones, phosphine oxides, iodonium and sulfonium salts, etc.

(25) FIG. 2 shows a system 200 configured in accordance with one embodiment of the invention. In this system, material 202 is first dispensed onto a transparent substrate 204 by a coating system 206, for example one using a syringe and gap system, as discussed above. The material-coated substrate 208 is provided to a negative printing unit 210 in which a negative image of the layer to be added to the sample is created by eliminating (e.g., via laser jetting) excess material (i.e., that part of the coated material that will not be added to the sample) from the coated substrate. As illustrated, this excess material may be collected by a material reuse system 212 and provided back to the coating system 206 for reuse. As shown in this view, the remaining material 214 on the coated substrate is provided to a curing system (e.g., a UV curing system) 216 and/or an imaging system on its way to the sample building unit 218 where UV curing and/or drying can be used during contact with the sample 220. By curing/drying the material while it is in contact with the sample (that is, previously formed portions of the article under fabrication, which are disposed on a receiving substrate 222), the sample's next layer is printed directly thereon. A sample release system 224 then effects release of the sample 220 from the transport substrate 204.

(26) FIGS. 3a-3m illustrate in detail various steps involved in the overall printing process. Referring first to FIG. 3a, the negative jetting process 300 is illustrated. A layer 302 of material has been coated on an intermediate substrate (e.g., a film or foil) 304. A laser 306 is used to jet the negative of the image (of the next layer to be printed to the sample) from the coated substrate using the material's or the coated metal film's laser absorption properties. The jetted material 308 is collected 310 in a material recovery unit 312 (or units, if several materials are in use) and the material can be reused later (FIGS. 3a and 3b). Only segments of the image material 314 stay on the film 304 for further use (FIG. 3c).

(27) Optionally, as shown in FIG. 3d, the image material 314 on the film can be exposed to low power UV light 326 or temperature before contact with the sample. Because some materials, mostly liquid ones, need enhanced definition of image material boarders before such contact, e.g., to avoid a severe reduction in printing resolution, this procedure allows the boundaries of the portions of material image 314 to be well defined. In such a process, a UV partial curing station 318 may include a gas diffusion system 320 for introducing an inert gas (e.g., Ar, CO.sub.2, He, Ne, etc.) 322 into a workspace 324 in which UV light 326 from the UV light source 316 will be incident upon the material layer 314. The inert gas flows in from one or more gas inlets 328 and out through a diffuser 330 towards the workspace 324. A gas pressure homogenizer may be used to ensure constant pressure throughout the system.

(28) Preferably, the intermediate substrate 304 is coated with a thin metal foil 332, for example, a 20 nm thick layer of Ti. The layer of metal foil will substantially reduce transmission of the UV light 326 where present, ensuring that only the edge of the material layer 314 near the area of contact with the intermediate substrate 304 is cured or partially cured. As an example, a 20 nm thick layer of Ti will transmit only approximately one tenth of the UV light 326 that an unprotected area of the intermediate substrate 304 will transmit. In areas where the metal foil has been eliminated, e.g., as by laser ablation or other process, the UV light 326 will be incident upon the edges of the segments of the material layer 314, again ensuring that it is these edges only that are cured or partially cured. As an additional safeguard to prevent unwanted curing or over curing of the segments of the material layer 314, the gas diffusion system 320 may be made of a non-reflective material so that UV light 326 is not reflected towards the segments of the material layer 314.

(29) The presence of inert gas 322 pumped through the diffuser purges any oxygen from the workspace 324. The thickness of this workspace region is related to the gas pressure as it is forced through the diffuser 330. With the segments of material layer 314 maintained in the area of the workspace from which oxygen has been purged, the UV curing system then cures the bottom and edges of these segments through exposure to UV light 326 from the UV light source 316.

(30) FIGS. 3e and 3f provide before and after views of the contact between the film 304 (i.e., the segments of coated material 314 on the film) and the sample, while FIG. 3g illustrates the UV exposure and building of the sample. This stage may use either UV exposure or exposure to high temperature (a coated polyimide film such as Kapton can be used in such cases) to effect transfer of the material to the sample. As shown, the film 304 is brought into an area at which the receiving substrate 334 is present, and the receiving substrate (or an existing layer of the sample, if present) is brought into contact with the segments of coated material 314 on the film (e.g., by raising a state on which the receiving substrate is present). Then, the segments of coated material 314 are cured through exposure to UV light 336 from a UV light source 338. This may be the same or a different UV light source as mentioned above. The exposure to the UV light 336 (and/or heat) cures the segments of coated material to form segments of a new layer 340 of the sample (i.e., the object undergoing fabrication).

(31) After curing, the sample remains connected to the film 304 (through the segments of the newly cured layer 340). Therefore, a release mechanism is preferably provided. To that end, the laser itself (used for the negative printing) 306 can be used as a sample release unit since the metal coat of the film 304 is still beneath the now-cured material and can be used for laser wavelength absorption and sample release as shown in FIGS. 3h-3j. The laser 306 irradiates the positioned at which the segments of the newly cured layer 340 are present, permitting such separation. The laser can also be used for cleaning the sample of metal residues 342 that may have detached from the film 304 during sample release (FIG. 3k), leaving a clean, cured layer 340 present on the sample (FIG. 3l). The result 350 of printing several layers 340 is presented at FIG. 3m.

(32) FIGS. 4-7 show examples of configurations of systems for performing the methods of the present invention. In one embodiment of the invention, only one material is provided for printing only one layer. FIG. 4 illustrates such a configuration: Material 402 is coated on film 406; a laser system 414 removes the image negative, and multiple samples 420 are moved into contact with the film 406 sequentially. The material 416 is cured during contact, and a new sample replaces the old one.

(33) FIG. 5 illustrates a 3D version of the configuration shown in FIG. 4. This time, the same sample 520 is brought into repeated contact with the film 406 and each time a new layer 522a, 522b, etc., is added (printed) to the sample. The curing takes place during contact of the top of the sample with the material in a new layer 524 on the film. However, it is important to note that if there is no direct contact between the material on the film and the sample, the transfer from the film to the sample will not occur. Therefore, the transfer depends on the area of each unit of material on the film and the surface structure of the sample.

(34) One way to overcome this issue is to add a support material 602 that will come in contact with the film 406 and therefore will transfer all the material 524 on the film to the sample. FIG. 6 illustrates the use of support material 602 in order to collect all the material from the film to the sample.

(35) FIG. 7 illustrates the use of an optional unit 702 for 3D negative printing with a support material. The optional unit 702 injects the support material 704 mechanically (e.g., via a syringe 706) to even the sample height that will be in contact with the film 406 during curing. The sample 520 is moved back and forth between the curing position 710 and the support injection position 712 between layers.

(36) An even more advanced configuration of a system configured in accordance with embodiments of the invention is one for the 3D printing of multiple materials. In such cases, several coating units are placed to provide different materials to the transfer film(s) and different materials are coated on the film or films, negative images for each respective material are removed from the film(s), and the materials are brought into contact with the sample and transferred thereto. FIG. 8a-8b illustrate before and after views of the contact between a substrate 802 that includes a second material 804 and a sample 334 that already contains the first material 314. The negative images of the different materials are compatible so that they can co-exist in the same layer.

(37) The film itself could be a transparent anti-stick foil. For example, PTFE or PFE or other anti-stick foils can used in order to ensure the easy release of the sample from the film after curing. FIGS. 9a-9b illustrate before and after views of the release process based on anti-stick properties of a film 902. That approach for sample release could be a complementary approach to the laser release mechanism mentioned above or the only release mechanism to be used.

(38) Yet another approach for sample release could be a dominantly mechanical approach. FIG. 10 illustrates a mechanical release system 1002 that can work with or without the formerly mentioned release mechanisms. Any of several mechanical approaches can be used. For example, a low angle release towards a “Y”-axis, by moving the film 406 at a small angle away from the sample 1004, can be used. Alternatively, two Z-axes, one for a frame (holding the film 406) and one for the sample 1004 may be used. Another approach would be to use acoustic vibrations to release the film 406 from the sample 1004.

(39) FIG. 11 illustrates one additional feature of a system configured in accordance with embodiments of the invention: the material reuse system 1102. In order to reduce waste, the negative image printing can be done above a tray or other vehicle that collects unused material and injects it back into the syringe 404 of the coating unit.

(40) Not shown in the above-described views are one or more units that control the operation of the various systems. Persons of ordinary skill in the art will appreciate that such units, often called controllers or similar names, are processor-based units that are programmable to carry out the above-escribed processes by issuing signals to elements of the coating system, the negative printing unit, the material reuse system, the curing system(s) and the sample release system. In some cases, these signals will actuate end effectors, rollers, lasers, UV or IR lighting/heating systems, and other elements to carry out the above-described tasks. Such a controller generally includes a processor or processors that execute(s) computer-readable instructions (i.e., computer programs or routines) defining methods as described herein, which methods are instantiated and run on non-transitory computer-readable media. Such processes may be rendered in any computer language and executed on any suitable programmable logic hardware. Processor-based controllers upon or with which the methods of the present invention may be practiced will typically include a bus or other communication mechanism for communicating information; a main memory, such as a RAM or other dynamic storage device, coupled to the bus for storing information and instructions to be executed by the processor and for storing temporary variables or other intermediate information during execution of instructions to be executed by the processor; and a ROM or other static storage device coupled to the bus for storing static information and instructions for the processor. A storage device, such as a hard disk or solid-state drive, may also be included and coupled to the bus for storing information and instructions. The subject controller may, in some instances, include a display coupled to the bus for displaying information to a user. In such instances, an input device, including alphanumeric and/or other keys, may also coupled to the bus for communicating information and command selections to the processor. Other types of user input devices, such as cursor control devices may also be included and coupled to the bus for communicating direction information and command selections to the processor and for controlling cursor movement on the display.

(41) The controller may also include a communication interface coupled to the processor, which provides for two-way, wired and/or wireless data communication to/from the controller, for example, via a local area network (LAN). The communication interface sends and receives electrical, electromagnetic, or optical signals which carry digital data streams representing various types of information. For example, the controller may be networked with a remote unit to provide data communication to a host computer or other equipment operated by a user. The controller can thus exchange messages and data with the remote unit, including diagnostic information to assist in troubleshooting errors, if needed.

(42) Thus, methods and apparatus for the fabrication of solid three-dimensional objects from liquid polymerizable materials at high resolution have been described.