Patent Description:
Liquid metal jet printing, such as magnetohydrodynamic (MHD) liquid metal jet printing, includes ejecting liquid or molten metal drops from a printhead to a substrate, which may be a heated stage or a previously deposited metal, to form a workpiece or article. Generally, liquid metal jet printing includes utilizing a direct current pulse applied by an electromagnetic coil to expel molten metal drops toward the substrate. As the metal drops contact the substrate, the metal drops cool to form the article. While liquid metal jet printing has made great progress, the articles fabricated from conventional liquid metal jet printing systems often exhibit inconsistencies with respect to build strength, adhesion, porosity, surface finish, cracking, fractures, z-height errors, or the like.

In view of the foregoing, secondary or post-printing processes, such as machining and finishing, are often implemented to address the inconsistencies in the articles fabricated from conventional liquid metal jet printing systems. The post-printing processes, however, greatly reduces productivity and correspondingly increases cost of fabricating the article via liquid metal jet printing.

What is needed, then, are improved liquid metal jet printing systems and methods for the same.

<CIT> discloses an additive manufacturing tool configured to receive a metallic material and to supply a plurality of droplets to a part at a work region of the part, wherein each droplet of the plurality of droplets comprises the metallic material and a heating system comprising a primary laser system configured to generate a primary laser beam to heat a molten zone of a substrate of the part and a secondary laser system configured to generate a secondary laser beam to heat a transition zone of the substrate of the part.

<CIT> discloses a method of three-dimensional printing comprises heating a first portion of a build surface on a platform by impinging a laser beam on the build surface so as to provide a preheated drop contact point having a first deposition temperature.

<CIT> discloses a system comprising a base plate; a 3D printed object mounted on the base plate; a controller; a motion system connected with the base plate and controlled by the controller for enabling movement in Z axis and at least one more axis; and at least one treating device; the at least one treating device configured to be directed towards the 3D printed object for heating a target spot area on one of the outer surface and the inner surface of the 3D printed object during the movement of the base plate.

<CIT> discloses a method for shaping a three-dimensional shaped object using a cutting tool configured to perform cutting at a first length at maximum in a predetermined cutting direction.

The following presents a simplified summary in order to provide a basic understanding of some aspects of one or more embodiments of the present teachings. This summary is not an extensive overview, nor is it intended to identify key or critical elements of the present teachings, nor to delineate the scope of the disclosure. Rather, its primary purpose is merely to present one or more concepts in simplified form as a prelude to the detailed description presented later.

The present disclosure provides an additive manufacturing device for fabricating an article in accordance with appended claim <NUM>.

In some examples, the targeted heating system may be configured to heat the droplets deposited on the substrate, the area proximal the substrate, or combinations thereof to a temperature of about ± <NUM>% to about ± <NUM>% of a melting point of the build material.

In some examples, the printhead and the targeted heating system may be coupled with one another.

In some examples, the targeted heating system may include one or more lasers.

In some examples, the one or more lasers may include an irradiance of from about <NUM>,<NUM> W/cm<NUM> to about <NUM>,<NUM> W/cm<NUM>.

In some examples, the one or more lasers may include a high power laser imager.

In some examples, the high power laser imager may include a 1D imager or a 2D imager.

In some examples, the targeted heating system may be configured to operate at temperatures of from greater than or equal to about <NUM> to less than or equal to about <NUM>.

In some examples, the targeted heating system may include a monogon system, the monogon system comprising one or more monogon scanners, one or more Galvo mirrors, or combinations thereof.

In some examples, the monogon system may include a monogon scanner. The monogon scanner may be substantially free of a reflective coating.

In some examples, the additive manufacturing device may further include a monitoring system. The monitoring system may be configured to monitor a portion of the additive manufacturing device.

In some examples, the monitoring system may include a pyrometer configured to measure a temperature of the substrate, the area proximal the substrate, or combinations thereof.

In some examples, the additive manufacturing device may further include: a computing system operably coupled with the printhead and the targeted heating system; and a monitoring system operably coupled with the computing system and configured to monitor the additive manufacturing device.

In some examples, the build material may include one or more metals or metal alloys. The one or more metals or metal alloys may include one or more of aluminum, an aluminum alloy, brass, bronze, chromium, a cobalt-chrome alloy, copper, a copper alloy, an iron alloy, nickel, a nickel alloy, a nickel-titanium alloy, stainless steel, tin, titanium, a titanium alloy, gold, silver, molybdenum, tungsten, or combinations thereof.

In some examples, the build material may include one or more polymers. The one or more polymers may include one or more of acrylonitrile butadiene styrene (ABS), polycarbonate (PC), polylactic acid (PLA), high density polyethylene (HDPE), polyphenylsulfone (PPSU), poly(meth)acrylate, polyetherimide (PEI), polyether ether ketone (PEEK), high impact polystyrene (HIPS), thermoplastic polyurethane (TPU), a polyamide, composites thereof, or combinations thereof.

The present disclosure provides a method in accordance with appended claim <NUM> for fabricating an article with any one or more of the additive manufacturing devices disclosed herein.

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present teachings. These and/or other aspects and advantages in the embodiments of the disclosure will become apparent and more readily appreciated from the following description of the various embodiments, taken in conjunction with the accompanying drawings of which:.

The following description of various typical aspect(s) is merely exemplary in nature and is in no way intended to limit the disclosure, its application, or uses.

Any value within the range may be selected as the terminus of the range. In addition, all references cited herein are hereby incorporated by reference in their entireties.

As used herein, the term "or" is an inclusive operator, and is equivalent to the term "and/or," unless the context clearly dictates otherwise. The term "based on" is not exclusive and allows for being based on additional factors not described, unless the context clearly dictates otherwise. In the specification, the recitation of "at least one of A, B, and C," includes embodiments containing A, B, or C, multiple examples of A, B, or C, or combinations of A/B, A/C, B/C, AlBIB/ BIB/C, A/B/C, etc. In addition, throughout the specification, the meaning of "a," "an," and "the" include plural references. The meaning of "in" includes "in" and "on.

Reference will now be made in detail to exemplary embodiments of the present teachings, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same, similar, or like parts.

The present disclosure is directed to additive manufacturing devices or 3D printers and methods for the same. Particularly, the present disclosure is directed to targeted heating systems for the 3D printers and methods for the same. Forming structures with molten metal droplets is a complex thermo-fluidic process that involves re-melting, coalescence, cooling, and solidification. Voids and cold lap (lack of fusion) are caused by poor re-melting and insufficient metallurgical bonding under inappropriate temperatures at the interface formed between the molten metal droplets and previously deposited material or substrates (e.g., droplets). The interfacial temperature is determined primarily by the droplet temperature and the surface temperature of the previously deposited material or substrate. Obtaining and retaining accurate part shape and z-height are also negatively impacted by the same factors. An interfacial temperature that is too low results in the formation of voids and cold laps from insufficient re-melting and coalescence. For an interfacial temperature that is too high, the new droplets flow away from the surface of previously deposited material before solidification, which leads to the malformation of part shape and z-height error. The interfacial temperature can be affected by the initial droplet temperature, the build part surface temperature, the build plate temperature, drop frequency, and part z-height. It can be controlled at some level through process parameter optimization, but the thermal processes involved may be too slow to keep up with the changes and dynamics that occur during part printing that can result in unacceptable interfacial temperatures. As further described herein, the targeted heating systems may be capable of or configured to modify interfacial temperatures and/or temperature gradients of a substrate and/or an area proximal the substrate to control grain size, growth, and/or structure of the metal forming an article prepared by the 3D printer to address the aforementioned issues. For example, the targeted heating system may be capable of or configured to modify interfacial temperatures and/or temperature gradients of a melt pool to control grain size, growth, and/or structure of the metal forming the article, thereby improving build strength, adhesion, porosity, and/or surface finish, and preventing cracks and fractures in the article.

<FIG> illustrates a schematic cross-sectional view of an exemplary additive manufacturing layering device or 3D printer <NUM> incorporating a targeted heating system <NUM>, according to one or more embodiments. The 3D printer <NUM> may be a liquid metal jet printing system, such as a magnetohydrodynamic (MHD) printer. It should be appreciated, however, that any additive manufacturing device may utilize the targeted heating system <NUM> and methods disclosed herein. The 3D printer <NUM> may include a printhead <NUM>, a stage <NUM>, a computing system <NUM>, the exemplary targeted heating system <NUM>, or any combination thereof. The computing system <NUM> may be operably and/or communicably coupled with any one or more of the components of the 3D printer <NUM>. The computing system <NUM> may be capable of or configured to operate, modulate, instruct, receive data from, or the like from any one or more of the components of the 3D printer <NUM>. The printhead <NUM> may include a body <NUM>, which may also be referred to herein as a pump chamber, one or more heating elements (one is shown <NUM>), one or more metallic coils <NUM>, or any combination thereof, operably coupled with one another. As illustrated in <FIG>, the heating elements <NUM> may be at least partially disposed about the body <NUM>, and the metallic coils <NUM> may be at least partially disposed about the body <NUM> and/or the heating elements <NUM>. As used herein, a substrate <NUM> may refer to a surface of the stage <NUM>, a previously deposited metal (e.g., metal droplets), an article <NUM> fabricated from the 3D printer <NUM> or a portion thereof, a platen <NUM>, such as a heated platen or build plate disposed on the stage <NUM>, and/or respective surfaces thereof. As illustrated in <FIG>, the substrate <NUM> may be disposed on or above the stage <NUM> and below the body <NUM>. The body <NUM> may have an inner surface <NUM> defining an inner volume <NUM> thereof. The body <NUM> may define a nozzle <NUM> disposed at a first end portion of the body <NUM>.

In an exemplary operation of the 3D printer <NUM> with continued reference to <FIG>, a build material (e.g., metal) from a source <NUM> may be directed to the inner volume <NUM> of the body <NUM>. The heating elements <NUM> may at least partially melt the build material contained in the inner volume <NUM> of the body <NUM>. For example, the build material may be a solid, such as a solid metal, and the heating elements <NUM> may heat the body <NUM> and thereby heat the build material from a solid to a liquid (e.g., molten metal). The metallic coils <NUM> may be coupled with a power source (not shown) capable of or configured to facilitate the deposition of the build material on the substrate <NUM>. For example, the metallic coils <NUM> and the power source coupled therewith may be capable of or configured to generate a magnetic field, which may generate an electromotive force within the body <NUM>, thereby generating an induced electrical current in the molten metal disposed in the body <NUM>. The magnetic field and the induced electrical current in the molten metal may create a radially inward force on the liquid metal, known as a Lorentz force, which creates a pressure at the nozzle <NUM>. The pressure at the nozzle <NUM> may expel the molten metal out of the nozzle <NUM> toward the substrate <NUM> and/or the stage <NUM> in the form of one or more drops to thereby form at least a portion of the article <NUM>.

The targeted heating system <NUM> is be capable of or configured to heat at least a portion of the substrate <NUM> and/or an area proximal the substrate <NUM>. For example, the targeted heating system <NUM> may be capable of or configured to heat at least a portion of the platen <NUM>, a portion of the article <NUM>, respective surfaces thereof, and/or areas proximal thereto. The targeted heating system <NUM> may heat the portion of the substrate <NUM> before, during, and/or after deposition of the one or more drops of the molten metal on the substrate <NUM> and/or an area proximal the substrate <NUM>. In an exemplary embodiment, the targeted heating system <NUM> heats the portion of the substrate <NUM> before and/or during the deposition of the drops on the substrate <NUM>. It should be appreciated that the deposition of the drops on the substrate <NUM> may create or form a melt pool on the substrate <NUM>, and the targeted heating system <NUM> may be capable of or configured to at least partially modulate (e.g., increase, decrease, alter, etc.) an interfacial temperature or a temperature gradient of the melt pool to thereby control one or more properties of the resulting solid metal forming the article <NUM>. For example, modulating the temperature gradient of the melt pool may allow the 3D printer <NUM> to control a grain size, grain growth, grain structure, grain orientation, and/or grain boundaries, of the resulting solid metal forming the article <NUM>. It should be appreciated that metal grain formation, structure, and/or properties (e.g., size, growth, orientation, boundaries, etc.) may at least partially determine one or more mechanical properties of the resulting portion of the article <NUM>. For example, the grain formation and/or structure may at least partially determine a yield stress, ductility, hardness, fatigue life, or combinations thereof, of the resulting solid metal forming the article <NUM>. As such, the targeted heating system <NUM> may be capable of or configured to at least partially heat the portions of the substrate <NUM> to thereby controls one or more properties of the solid metal forming the article <NUM>.

The targeted heating system <NUM> may also be capable of or configured to reheat or re-melt a previously deposited drop or section of the article <NUM> to control the interfacial temperature and/or temperature gradient of the melt pool as the molten metal drops and the previously deposited metals are coalescing to thereby improve the mechanical and/or build qualities of the article <NUM>. It should be appreciated that an amount of heat or thermal energy needed to sufficiently control the temperature gradient of the melt pool may be minimal as a temperature of the article <NUM> and/or the melt pool or the coalescing region thereof is already maintained at a relatively high temperature. As such, the targeted heating system <NUM> may be cost effectively operated and provide sufficient thermal energy to control the temperature gradient of the melt pool. It should further be appreciated that the targeted heating system <NUM> may be operated in an in-line manner such that productivity is not reduced. For example, the targeted heating system <NUM> may be operated alongside the other components of the 3D printer <NUM> to provide articles <NUM> with improved properties and without an off-line secondary or post-printing process.

In addition to the foregoing, the targeted heating system <NUM> may be capable of or configured to at least partially heat a portion of the substrate <NUM> near or proximal the deposition of the drops and/or near or proximal the melt pool. For example, the targeted heating system <NUM> may be capable of or configured to at least partially heat a portion of the substrate <NUM> adjacent to or outside of the deposition of the drops and/or the melt pool. It should be appreciated that heating the portion of the substrate <NUM> near, proximal, or adjacent the deposition of the drops and/or the melt pool may reduce surface roughness and/or provide improved surface finishing capabilities as compared to a surface without heating from the targeted hearing system <NUM>.

The targeted heating system <NUM> may directly heat an area having a diameter of from about <NUM> to about <NUM>. For example, the output (e.g., laser beam) of the targeted heating system <NUM> may have a diameter or a major axis of from about <NUM> to about <NUM>. In at least one embodiment, the output of the targeted heating system <NUM> may have a diameter or a major axis of from about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, or about <NUM> to about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, or about <NUM>.

The substrate <NUM>, the area proximal the substrate <NUM>, and/or near the article <NUM> being fabricated may be maintained at a temperature of from about <NUM> to about <NUM>. For example, the temperature may be from greater than or equal to about <NUM>, greater than or equal to about <NUM>, greater than or equal to about <NUM>, greater than or equal to about <NUM>, greater than or equal to about <NUM>, greater than or equal to about <NUM>, greater than or equal to about <NUM>, or greater than or equal to about <NUM>, and less than or equal to about <NUM>. In another example, the temperature may be from greater than or equal to about <NUM> or greater than or equal to about <NUM> to less than or equal to about <NUM>, less than or equal to about <NUM>, less than or equal to about <NUM>, less than or equal to about <NUM>, less than or equal to about <NUM>, or less than or equal to about <NUM>. It should be appreciated that all or substantially all the components of the targeted heating system <NUM> may be capable of or configured to operate in the temperatures of the substrate <NUM>, the area proximal the substrate <NUM>, and/or near the article <NUM>.

The targeted heating system <NUM> may be capable of or configured to heat the substrate <NUM> and/or the area proximal the substrate <NUM> to a temperature of at least <NUM>% to about <NUM>% of a melting point of the build material. For example, the targeted heating system <NUM> may be capable of or configured to heat the substrate <NUM> and/or the area proximal the substrate <NUM> to a temperature of at least <NUM>%, at least <NUM>%, at least <NUM>%, at least <NUM>%, at least <NUM>%, at least <NUM>%, at least <NUM>%, or at least <NUM>% to about <NUM>% of the melting point of the build material. In another embodiment, the targeted heating system <NUM> may be capable of or configured to increase a temperature of the substrate <NUM> and/or the area proximal the substrate <NUM> (e.g., a coalescence area or melt pool) about ± <NUM>%, ± <NUM>%, ±<NUM>%, ± <NUM>%, ± <NUM>%, ± <NUM>%, ± <NUM>%, ± <NUM>%, or ± <NUM>% of a melting point of the build material.

In at least one embodiment, the build material may be or include one or more metals and/or alloys thereof. Illustrative build materials may be or include, but are not limited to, aluminum, aluminum alloys, brass, bronze, chromium, cobalt-chrome alloys, copper, copper alloys, iron alloys (Invar), nickel, nickel alloys (Inconel), nickel-titanium alloys (Nitinol), stainless steel, tin, titanium, titanium alloys, gold, silver, molybdenum, tungsten, or the like, or alloys thereof, or any combination thereof. It should be appreciated that the droplet and substrate temperatures will be different for different metals.

In another embodiment, the build material may be or include one or more polymeric materials or polymers, or composites thereof. The polymers may be or include functional polymers. Illustrative functional polymers may include, but are not limited to, heat resistant polymers, conductive polymers, piezoelectric polymers, photosensitive polymers, or any combination thereof. The polymers may also be or include, but are not limited to, polyolefin-based polymers, acryl-based polymers, polyurethane-based polymers, ether-based polymers, polyester-based polymers, polyamide-based polymers, formaldehyde-based polymers, silicon-based polymers, or any combination thereof. For example, the polymers may include, but are not limited to, poly(ether ether ketone) (PEEK), TORLON®, polyamide-imides, polyethylene (PE), polyvinyl fluoride (PVF), polyvinyl chloride (PVC), polyvinylidene fluoride (PVDF), polyvinylidene chloride (PVDC), polychlorotrifluoroethylene (PCTFE), polytetrafluoroethylene (PTFE), polypropylene (PP), poly(<NUM>-butene), poly(<NUM>-methylpentene), polystyrene, polyvinyl pyridine, polybutadiene, polyisoprene, polychloroprene, styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene terpolymer, ethylene-methacrylic acid copolymer, styrene-butadiene rubber, tetrafluoroethylene copolymer, polyacrylate, polymethacrylate, polyacrylamide, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl ether, polyvinylpyrrolidone, polyvinylcarbazole, polyurethane, polyacetal, polyethylene glycol, polypropylene glycol, epoxy resins, polyphenylene oxide, polyethylene terephthalate, polybutylene terephthalate, polydihydroxymethylcyclohexyl terephthalate, cellulose esters, polycarbonate, polyamide, polyimide, any copolymers thereof, or any combination thereof. In at least one embodiment, the polymer may be or include an elastomer, synthetic rubber, or any combination thereof. Illustrative elastomeric materials and synthetic rubbers may include, but are not limited to, VITON®, nitrile, polybutadiene, acrylonitrile, polyisoprene, neoprene, butyl rubber, chloroprene, polysiloxane, styrene-butadiene rubber, hydrin rubber, silicone rubber, ethylene-propylene-diene terpolymers, any copolymers thereof, or any combination thereof.

In an exemplary embodiment, the polymer includes acrylonitrile butadiene styrene (ABS), polycarbonate (PC), polylactic acid (PLA), high density polyethylene (HDPE), polyphenylsulfone (PPSU), poly(meth)acrylate, polyetherimide (PEI), polyether ether ketone (PEEK), high impact polystyrene (HIPS), thermoplastic polyurethane (TPU), polyamides (nylon), composites thereof, or combinations thereof.

In at least one embodiment, the 3D printer <NUM> may include a monitoring system <NUM> capable of or configured to control and/or monitor one or more components or portions of the 3D printer <NUM>, the formation of the article <NUM>, one or more portions of the substrate <NUM>, one or more areas proximal the substrate <NUM>, and/or the deposition of the droplets. For example, the monitoring system <NUM> may include one or more illuminators (not shown) capable of or configured to measure droplet, build part, build plate, and substrate temperatures, measure build part shape and z-height, measure droplet size and rate, or the like, or any combination thereof. Illustrative illuminators may be or include, but are not limited to, lasers, LEDs, lamps of various types, fiber optic light sources, or the like, or combinations thereof. In another example, the monitoring system <NUM> may include one or more sensors (not shown) capable of or configured to measure a temperature of one or more components or portions of the 3D printer <NUM>. Illustrative sensors may be or include, but are not limited to, pyrometer, thermistors, imaging cameras, photodiodes, or the like, or combinations thereof. The monitoring system <NUM> may also be capable of or configured to provide feedback or communicate with the computing system <NUM>.

In at least one embodiment, any one or more components of the 3D printer <NUM> may move independently with respect to one another. For example, any one or more of the printhead <NUM>, the stage <NUM> and the platen <NUM> coupled therewith, the targeted heating system <NUM>, the monitoring system <NUM>, or any combination thereof may move independently in the x-axis, the y-axis, and/or the z-axis, with respect to any one or more of the other components of the 3D printer <NUM>. In another embodiment, any two or more of the components of the 3D printer <NUM> may be coupled with one another; and thus, may move with one another. For example, the printhead <NUM> and the targeted heating system <NUM> may be coupled with one another via a mount (not shown) such that the movement or translation of the printhead <NUM> in the x-axis, the y-axis, and/or the z-axis results in a corresponding movement of the targeted heating system <NUM> in the x-axis, the y-axis, and/or the z-axis, respectively. Similarly, the targeted heating system <NUM> and the stage <NUM> may be coupled with one another via a mount (not shown) such that the movement of the targeted heating system <NUM> in the x-axis, the y-axis, and/or the z-axis results in a corresponding movement of the stage <NUM> in the x-axis, the y-axis, and/or the z-axis, respectively.

<FIG> illustrates a schematic view of another exemplary additive manufacturing layering device or 3D printer <NUM> incorporating an exemplary targeted heating system <NUM>, according to one or more embodiments. The 3D printer <NUM> illustrated in <FIG> may be similar in some respects to the 3D printer <NUM> described above and therefore may be best understood with reference to the description of <FIG>, where like numerals designate like components and will not be described again in detail.

As illustrated in <FIG>, the targeted heating system <NUM> of the 3D printer <NUM> may include one or more lasers (two are shown <NUM>). The lasers <NUM> may include external optical components like filters, collimating optics, focusing optics and beam shaping optics to achieve desired irradiance levels, irradiance pattern (i.e., circular, elliptical, etc.) and irradiance profiles (i.e., Gaussian, top-hat, doughnut mode, multimode, etc.). As further illustrated in <FIG>, the lasers <NUM> may be coupled with the printhead <NUM> via a mount <NUM>. While <FIG> illustrates the lasers <NUM> of the targeted heating system <NUM> coupled with the printhead <NUM>, it should be appreciated, as discussed above, that the targeted heating system <NUM> or the lasers <NUM> thereof may be coupled with any other component of the 3D printer <NUM>. As illustrated in <FIG>, any one or more of the lasers <NUM> may be capable of or configured to direct a laser beam on or proximal the substrate <NUM> to thereby heat the substrate <NUM> or a portion thereof.

The lasers <NUM> of the targeted heating system <NUM> may be or include any suitable laser that is capable of or configured to sufficiently heat the substrate <NUM> and/or an area proximal the substrate <NUM>. In at least one embodiment, the type of the lasers <NUM> utilized may be at least partially dependent on the build material, such as the type of metal being deposited to fabricate the article <NUM>. In another embodiment, the type of the lasers <NUM> utilized may at least partially depend on a rate at which the drops are deposited on the substrate <NUM> or the deposition rate.

In at least one embodiment, the laser <NUM> may be or include, but is not limited to, an in-line high power laser imager capable of or configured to deliver targeted high power laser energy to the substrate <NUM> and/or an area proximal the substrate <NUM>. The high power laser imager may be a 1D imager or a 2D imager. The in-line high power laser imager may utilize one or more of a high power laser, arrays of independently addressable diode lasers or vertical cavity surface emitting lasers (VCSELs), an illumination optical system, a spatial light modulator, a pixelated spatial light modulator, a projection optical system, or combinations thereof. The illumination optical system may be capable of or configured to shape the laser emission and deliver it onto the spatial light modulator. The projection optical system may be capable of or configured to image the spatial light modulator onto the substrate <NUM> and/or an area proximal the substrate <NUM>. A pixelated line image or 1D image may be produced with a linear spatial light modular, or linear arrays of diode lasers or VCSELs. Illustrative linear spatial light modulators may be or include, but are not limited to, a Grating Light Valve (GLV), digital Micromirror Device (DMD), a Liquid-Crystal on Silicon (LCOS) spatial light modulator, or the like, or combinations thereof. A pixelated area image or 2D image may be produced with a spatial light modulator or 2D arrays of VCSELs. Illustrative spatial light modulators for producing the 2D image may be or include, but are not limited to, a 2D digital Micromirror Device (DMD), a 2D Liquid-Crystal on Silicon (LCOS) spatial light modulator, or the like, or combinations thereof. The 1D or 2D imager may be capable of or configured to pattern over a line or area to delivery targeted laser energy to more than one droplet location on the substrate <NUM> and/or an area proximal the substrate <NUM>. The 1D or 2D imager may be capable of or configured to shape the laser beam profile within one or more droplet locations to alter local thermal gradients within the melt pool of the one or more droplets at the substrate <NUM> and/or proximal an area of the substrate <NUM>. This is especially important for systems that employ printheads with multiple independent ejectors that enable parallel printing for faster build part fabrication and higher throughput.

In an exemplary embodiment, the lasers <NUM> may have an irradiance of from about <NUM> W/cm<NUM> to about <NUM>,<NUM> W/cm<NUM>. For example, any one or more of the lasers <NUM> may have an irradiance of from about <NUM> W/cm<NUM> up to <NUM>,<NUM> W/cm<NUM>, about <NUM>,<NUM> W/cm<NUM>, about <NUM>,<NUM> W/cm<NUM>, about <NUM>,<NUM> W/cm<NUM>, or about <NUM>,<NUM> W/cm<NUM> to about <NUM>,<NUM> W/cm<NUM>, about <NUM>,<NUM> W/cm<NUM>, about <NUM>,<NUM> W/cm<NUM>, about <NUM>,<NUM> W/cm<NUM>, about <NUM>,<NUM> W/cm<NUM>, or about <NUM>,<NUM> W/cm<NUM>. It should be appreciated that much lower power lasers or laser arrays could also be used depending on the application, metal, configuration and spot size. It should further be appreciated that any one or more of the lasers <NUM> may include a combination of power and optical configurations, including collimated and non-collimated lasers, that may achieve the desired irradiance.

As further illustrated in <FIG>, the monitoring system <NUM> may include a pyrometer <NUM> capable of or configured to measure a temperature of the substrate <NUM> or an area near or proximal the substrate <NUM>. For example, the pyrometer <NUM> may be capable of or configured to measure an area at and/or proximal the substrate <NUM> heated by the lasers <NUM> of the targeted heating system <NUM>. In another example, the pyrometer <NUM> may be capable of or configured to measure a temperature of the droplets from the printhead <NUM> or any other components of the 3D printer <NUM>.

<FIG> illustrates a schematic view of another exemplary additive manufacturing layering device or 3D printer <NUM> incorporating an exemplary targeted heating system <NUM>, according to one or more embodiments. The 3D printer <NUM> illustrated in <FIG> may be similar in some respects to the 3D printers <NUM>, <NUM> described above and therefore may be best understood with reference to the description of <FIG> or <FIG>, where like numerals designate like components and will not be described again in detail.

As illustrated in <FIG>, not according to the claimed invention, the targeted heating system <NUM> may include one or more fiber lasers <NUM>, such as a fiber-coupled laser. As further illustrated in <FIG>, the fiber laser <NUM> may be coupled with the printhead <NUM> via the mount <NUM>. The fiber laser <NUM> of the targeted heating system <NUM> may be or include any suitable fiber laser <NUM> capable of or configured to sufficiently heat the substrate <NUM> and/or an area proximal the substrate <NUM>. In at least one embodiment, the fiber laser <NUM> utilized may be at least partially dependent on the build material, such as the type of metal being deposited to fabricate the article <NUM>. In another embodiment, the fiber laser <NUM> utilized may at least partially depend on a rate at which the drops are deposited on the substrate <NUM> or the deposition rate.

The fiber laser <NUM> may be capable of or configured to output a continuous wave (CW). The fiber laser <NUM> may also be capable of or configured to output a pulsed wave beam. The fiber laser <NUM> may be polarized or unpolarized. The output light of the fiber laser <NUM> may be delivered by an optical single mode or an optical multimode output fiber. The output light of the fiber laser <NUM> may be collimated and/or shaped with an external optical system. The fiber laser <NUM> may be capable of or configured to operate at high ambient temperatures, such as temperatures of the 3D printers described herein. In at least one embodiment, at least a portion of the fiber laser <NUM> may be cooled, such as water-cooled. In yet another embodiment, at least a portion of the fiber laser <NUM> may be located outside a high temperature area of the 3D printers described herein. For example, at least a portion of the fiber laser <NUM> may be disposed in an area having temperatures of less than <NUM>, less than <NUM>, less than <NUM>, or less than <NUM>. It should be appreciated that the operating temperatures of the 3D printer may at least partially depend on the metal being deposited.

The fiber laser <NUM> may provide or form a laser or an output having a wavelength of from about <NUM> to about <NUM>. Though, it should be appreciated that other wavelengths could be used as they become commercially available from laser suppliers and manufacturers. For example, the output from the fiber laser <NUM> may be from about <NUM>, about <NUM>, about <NUM>, about <NUM>, or about <NUM> to about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, or about <NUM>.

<FIG> illustrates the inventive laser system <NUM> that is utilized in place of the fiber laser <NUM> of the targeted heating system <NUM> of <FIG>. The laser system <NUM> illustrated in <FIG> utilizes a fiber coupled laser. The laser system <NUM> includes a fiber coupled laser module <NUM>, an output fiber <NUM>, one or more collimators (one is shown <NUM>), one or more polarizers (three are shown <NUM>, <NUM>, <NUM>), one or more polarization rotators (one is shown <NUM>), one or more variable retarders (one is shown <NUM>), one or more wave retarders (one is shown <NUM>), or combinations thereof. In an exemplary embodiment, the laser system <NUM> may consist of or consist essentially of the fiber coupled laser module <NUM>, the fiber output <NUM>, the collimator <NUM>, the one or more polarizers <NUM>, <NUM>, <NUM>, the polarization rotator <NUM>, the variable retarder <NUM>, and the wave retarder <NUM>.

The one or more polarizers <NUM>, <NUM>, <NUM> may be or include, but are not limited to, a polarizing beam splitter (PBS), a linear polarizer, or combinations thereof. The polarization rotator <NUM> may be or include, but is not limited to, a ferroelectric liquid crystal polarization rotator. The variable retarder <NUM> may be or include, but is not limited to, a nematic liquid crystal (LC) variable retarder. The wave retarder <NUM> may be or include, but is not limited to, a quarter wave retarder.

As illustrated in <FIG>, the fiber coupled laser module <NUM> is coupled with the output fiber <NUM>. The fiber coupled laser module <NUM> and the output fiber <NUM> coupled therewith may be capable of or configured to generate and output unpolarized light or laser. The collimator <NUM> is disposed downstream of the output fiber <NUM>. The one or more polarizers <NUM>, <NUM>, <NUM> is disposed downstream of the collimator <NUM>. As illustrated in <FIG>, a first polarizer <NUM>, a second polarizer <NUM>, and a third polarizer <NUM> are disposed downstream of the collimator <NUM>. The polarization rotator <NUM> may be disposed downstream any one or more of the polarizers <NUM>, <NUM>, <NUM> and/or upstream any one or more of the polarizers <NUM>, <NUM>, <NUM>. For example, as illustrated in <FIG>, the polarization rotator <NUM> may be interposed between the first polarizer <NUM> and the second polarizer <NUM>. In another embodiment, further described herein, the polarization rotator <NUM> may be interposed between the second polarizer <NUM> and the third polarizer <NUM>. The variable retarder <NUM> is disposed upstream of the wave retarder <NUM>. Similarly, the wave retarder <NUM> is disposed downstream the variable retarder <NUM>. In at least one embodiment, the variable retarder <NUM> and the wave retarder <NUM> may be disposed downstream any one or more of the polarizers <NUM>, <NUM>, <NUM> and/or upstream any one or more of the polarizers <NUM>, <NUM>, <NUM>. For example, as illustrated in <FIG>, the variable retarder <NUM> and the wave retarder <NUM> may be interposed between the second polarizer <NUM> and the third polarizer <NUM>.

In at least one embodiment, the polarization rotator <NUM>, which may be a ferroelectric LC polarization rotator, may be operably coupled with any one or more of the polarizers <NUM>, <NUM>, <NUM> (e.g., PBS or linear polarizer) to form a liquid crystal shutter. The combination of the polarization rotator <NUM> and the one or more of the polarizers <NUM>, <NUM>, <NUM> may form the liquid crystal shutter that may operate at about <NUM>% duty cycle with about <NUM> microsecond rise and fall times. The liquid crystal shutter may modulate the beam "on" by allowing the beam to remain P-polarized and pass through the polarization beam splitter <NUM>, <NUM>, <NUM> or modulate the beam "off' by switching the beam to an S-polarized state; and thus, having it reflect off of the polarizers <NUM>, <NUM>, <NUM> into a beam dump <NUM>.

The liquid crystal shutter formed from the polarization rotator <NUM> and any one or more of the polarizers <NUM>, <NUM>, <NUM> may be capable of or configured to have varying shutter speeds to thereby match a droplet rate of the printhead <NUM>. Matching the droplet rate may allow the liquid crystal shutter to deliver the laser energy to the substrate <NUM> and/or an area proximal the substrate <NUM> just before or as the drop is deposited. The ability to vary or modify the shutter rate of the liquid crystal shutter may also reduce the amount of errors in the shutter rate.

In at least one embodiment, the variable retarder <NUM>, which may be a nematic liquid crystal variable retarder, may be combined with the wave retarder <NUM>, which may be a quarter-wave retarder, to form a nematic liquid crystal variable polarization rotator <NUM>. In operation, the wave retarder <NUM> may be capable of or configured to convert elliptical polarization from the variable retarder <NUM> to form linear polarization.

The nematic liquid crystal variable polarization rotator <NUM> may be operably coupled with any one or more of the polarizers <NUM>, <NUM>, <NUM>. The combination of the nematic liquid crystal variable polarization rotator <NUM> and any one or more of the polarizers <NUM>, <NUM>, <NUM> may be capable of or configured to change an amplitude and/or power level of the laser directed to the article <NUM> (see <FIG>). The nematic liquid crystal variable polarization rotator <NUM>. It should be appreciated that a drive current directed to the fiber coupled laser module <NUM> may also be adjusted to modulate the output power level of the laser system <NUM>.

The laser system <NUM> may include one or more additional accessories and/or optics capable of or configured to adjust, focus, and/or shape a beam profile thereof. The beam profile may have a Gaussian, Top-Hat, or multimode profile. Illustrative accessories may be or include, but are not limited to, lenses, axicons, collimators, phase plates, beam expanders, or the like, or combinations thereof.

<FIG> illustrates another exemplary laser system <NUM> that may be utilized in place of the fiber laser <NUM> of the targeted heating system <NUM> of <FIG>, according to one or more embodiments. The laser system <NUM> illustrated in <FIG> may be similar in some respects to the laser system <NUM> described above and therefore may be best understood with reference to the description of <FIG>, where like numerals designate like components and will not be described again in detail.

As illustrated in <FIG>, the laser system <NUM> may include components similar to the laser system <NUM> illustrated in <FIG>. The nematic liquid crystal variable polarization rotator <NUM> of the laser system <NUM>, however, is interposed between the first polarizer <NUM> and the second polarizer <NUM>. Further, the polarization rotator <NUM> is interposed between the second polarizer <NUM> and the third polarizer <NUM>.

It should be appreciated that any one or more of the lasers described herein may be substituted or used in conjunction with other types of laser such as gas lasers, diode lasers, VCSELs, diode laser arrays, VCSEL arrays, diode-pumped solid state lasers, lasers in the near UV wavelength range (i.e., violet and blue) or visible wavelength range can also be used, or the like, or combinations thereof.

Adhesion of the 3D printed part or article <NUM> to the build plate or platen <NUM> must be strong enough to keep the part from separating from the build plate or platen <NUM>. During the printing process, the build part <NUM> experiences shearing forces caused by accelerations due to direction changes and speed changes as the part <NUM> is moved under the printhead <NUM>. On the other hand if the adhesion between the 3D printed part <NUM> and build plate <NUM> is too strong, secondary machining operations must be performed to cut or remove the part <NUM> from the build plate. Secondary operations increase cost and reduce productivity. Therefore, another use of the targeted heating systems <NUM> disclosed herein is to deliver laser energy to the localized area of the build plate <NUM> where the next molten metal droplet will be deposited to promote stronger adhesion or produce weaker adhesion depending on what is needed for the particular deposited metal type and build plate <NUM> coating or material. For example a higher local build plate temperature could induce greater wetting of the droplet onto the surface of the build plate <NUM> to increase adhesion. For some materials increasing the temperature would produce more oxidation on the droplet surface and decrease the adhesion. This would effectively create a release layer that can be used to separate the 3D printed part <NUM> from the build plate <NUM> by applying a shearing mechanical shock or a thermal shock. This would eliminate the need for secondary operations to remove the part <NUM> from the build plate <NUM>.

<FIG> illustrates a schematic view of another exemplary additive manufacturing device or 3D printer <NUM> incorporating the exemplary targeted heating system <NUM>, according to one or more embodiments. The 3D printer <NUM> illustrated in <FIG> may be similar in some respects to the 3D printers <NUM>, <NUM>, <NUM> described above and therefore may be best understood with reference to the description of the respective Figures, where like numerals designate like components and will not be described again in detail.

As illustrated in <FIG>, the targeted heating system <NUM> may include one or more monogon systems (one is shown <NUM>). The monogon system <NUM> may be capable of or configured to sufficiently heat the substrate <NUM> and/or an area proximal the substate <NUM>. In at least one embodiment, the monogon system <NUM> and/or the components thereof utilized may be at least partially dependent on the build material, such as the type of metal being deposited to fabricate the article <NUM>. In another embodiment, the monogon system <NUM> and/or the components thereof utilized may at least partially depend on a rate at which the drops are deposited on the substrate <NUM> or the deposition rate.

The monogon system <NUM> may include one or more monogon scanners (one is shown <NUM>), one or more mirrors (one is shown <NUM>), or combinations thereof. The mirror <NUM> may be capable of or configured to receive an output source, such as a high power laser beam, and reflect or redirect the output source to the monogon scanner <NUM>. The monogon scanner <NUM> may be capable of or configured to receive the output source from the mirror or another source and reflect or redirect the output source to the substrate <NUM> and/or an area proximal the substrate <NUM>.

Any suitable monogon scanner <NUM> may be utilized. In at least one embodiment, illustrated in <FIG>, the monogon scanner <NUM> may be or include a rotating monogon total internal reflection (TIR) scanner capable of or configured to be rotated about an axis (e.g., vertical axis) thereof. The monogon scanner <NUM> may be rotated about the axis to direct or control a position of the output beam on the substrate <NUM> and/or an area proximal the substrate <NUM>. Illustrative monogon scanners <NUM> may be or include, but are not limited to, a fused silica monogon optical scanner, or the like. The monogon scanner <NUM> may be capable of or configured to scan greater than <NUM>° in azimuth by axial rotation of the monogon scanner <NUM>. The monogon scanner <NUM> may also be capable of or configured to scan about <NUM>° in altitude when utilized with the mirror <NUM> (e.g., galvo mirror). The monogon scanner <NUM> may be capable of or configured to operate under high ambient temperatures of from about <NUM> or <NUM> to about <NUM>, or about <NUM> to about <NUM>. The monogon scanner <NUM> may be capable of or configured to operate with high laser powers (e.g., 1W to several kW).

In at least one embodiment, the monogon scanner <NUM> may be free or substantially free of a coating, such as a reflective coating or an anti-reflection coating. It should further be appreciated that the monogon system <NUM> may utilize a source of output (e.g., laser source or optical beam) outside of the high temperature area of the 3D printer <NUM>. While <FIG> illustrates a single monogon system <NUM>, it should be appreciated that a plurality of monogon systems <NUM> may be independently operated to heat the substrate <NUM> and/or the area proximal the substrate <NUM>.

In an exemplary operation of the 3D printer <NUM>, with continued reference to <FIG>, the stage <NUM> and the substrate <NUM> may be configured to move with one another relative to the printhead <NUM> in the x-axis, y-axis, and/or the z-axis. For example, the stage <NUM> and the substrate <NUM> may be configured to move with one another in the x-axis, y-axis, and the z-axis while the printhead <NUM> remains stationary. In another example, the printhead <NUM> may be configured to move in the x-axis, y-axis, and the z-axis while the stage <NUM> and the substrate <NUM> are stationary. In yet another example, the printhead <NUM> may move in the z-axis and the stage <NUM> and the substrate <NUM> may move in the x-axis and the y-axis. Similarly, the stage <NUM> and the substrate <NUM> may move in the z-axis while the printhead <NUM> may move in the x-axis and the y-axis.

The printhead <NUM> may direct droplets of the build material along a build path on the platen <NUM> or substrate <NUM> to form the article <NUM> drop by drop in a layer by layer manner. The time between the current jetted drop and the previously jetted drop that the current jetted drop will coalesce with may vary while moving along the build path, which may be at least partially determined by a shape and/or design of the article <NUM>. The current jetted drop may be directed on a previously jetted drop, which may be surrounded by varying amounts of previously jetted material (e.g., below and/or adjacent). As such, it should be appreciated that the current and/or the previously jetted drops may be maintained at varying temperatures. For example, heat conduction pathways may at least partially depend on the shape and/or design of the article <NUM>. As such, the temperature of the previously jetted drops and/or the current jetted drops may be maintained at different temperatures. In operation, the targeted heating system <NUM> may be capable of or configured to adjust a temperature of the substrate <NUM> and/or an area proximal the substrate <NUM>. The targeted heating system <NUM> may be operated to be at least partially dependent on one or more of a time difference between previous and current droplets of the build material, heat conduction differences along varying portions of the article <NUM>, the build path, the type of build material utilized, or combinations thereof.

In at least one embodiment, the energy or power of the targeted heating system <NUM> may be determined a priori from one or more of the following: shape and/or design of the article <NUM>, the build path along with the layers of the article <NUM> are formed or printed, the thermal environment, material parameters, printing parameters utilized, or combinations thereof. Illustrative printing parameters may be or include, but are not limited to, drop frequency, drop temperature, platen <NUM> temperature, or combinations thereof. In an exemplary embodiment, the energy or power of the targeted heating system <NUM> may be determined according to Formula (<NUM>): <MAT> where:.

The parameters or printer parameters may be or include, but are not limited to, initial droplet temperature, build plate or platen temperature, drop frequency, initial droplet ejection height, laser wavelength, or the like, or combinations thereof. Material parameters may be or include, but are not limited to, melting temperature, light absorption coefficient, density, specific heat, thermal conductivity, enthalpy, solidus temperature, liquidus temperature, or the like, or combinations thereof. Environmental parameters may be or include, but are not limited to, ambient temperature, humidity, sheath gas concentration, or the like, or combinations thereof. It should be appreciated that other or additional parameters and weights may be used in the equation to further optimize and refine the amount of the laser power or energy to the build part or article <NUM> and/or the build plate <NUM>.

The heat provided by the targeted heating system <NUM> and directed to the substrate <NUM> and/or an area proximal the substrate <NUM> may be utilized to heat, soften, remelt, or any combination thereof, previously and/or current drops or layers of the build material. The heat provided by the targeted heating system <NUM> may also be capable of or configured to affect a thermal gradient of the melt pool of the droplets during cooling to control various features of the article <NUM>. For example, the heat provided by the targeted heating system <NUM> may affect one or more of build strength, adhesion, porosity, surface finish, crack and/or fracture formation, grain size, grain orientation, structure, or the like, in the article <NUM>.

Claim 1:
An additive manufacturing device (<NUM>, <NUM>, <NUM>, <NUM>) for fabricating an article (<NUM>), comprising:
a stage (<NUM>) configured to support a substrate (<NUM>);
a printhead (<NUM>) disposed above the stage (<NUM>), the printhead configured to heat a build material to a molten build material and deposit the molten build material on the substrate (<NUM>) in the form of droplets to fabricate the article (<NUM>);
a targeted heating system (<NUM>) disposed proximal the printhead, the targeted heating system (<NUM>) configured to control a temperature or temperature gradient of the droplets deposited on the substrate (<NUM>), an area proximal the substrate (<NUM>), or combinations thereof, wherein the targeted heating system (<NUM>) comprises a laser system (<NUM>, <NUM>), the laser system (<NUM>, <NUM>) characterised therein by comprising:
a fiber coupled laser module (<NUM>);
an output fiber (<NUM>) coupled with the fiber coupled laser module;
a collimator (<NUM>) disposed downstream of the fiber output;
a polarization rotator (<NUM>) disposed downstream of the collimator (<NUM>);
a variable retarder (<NUM>) disposed downstream of the collimator (<NUM>); and
a wave retarder (<NUM>) disposed downstream of the variable retarder (<NUM>);
a first polarizer (<NUM>), a second polarizer (<NUM>), and a third polarizer (<NUM>), wherein:
the first polarizer (<NUM>) is disposed between the collimator (<NUM>) and the polarization rotator (<NUM>), the second polarizer (<NUM>) is disposed between the polarization rotator (<NUM>) and the variable retarder (<NUM>), and the third polarizer (<NUM>) is disposed downstream of the wave retarder (<NUM>), optionally wherein the polarization rotator (<NUM>) is disposed upstream of the variable retarder (<NUM>) and the wave retarder (<NUM>), or
the first polarizer (<NUM>) is disposed between the collimator (<NUM>) and the variable retarder (<NUM>), the second polarizer (<NUM>) is disposed between the wave retarder (<NUM>) and the polarization rotator (<NUM>), and the third polarizer (<NUM>) is disposed downstream of the polarization rotator (<NUM>), optionally wherein the variable retarder (<NUM>) and the wave retarder (<NUM>) are disposed upstream of the polarization rotator (<NUM>).