Gray-scale area printing for additive manufacturing

Abstract

The additive manufacturing system includes one or more light sources and one or more light valves. A two-dimensional gray-scale pattern can be written to the light valve, and the two-dimensional gray-scale pattern is added by the light valve to the beam from one or more light sources to obtain one or more patterned beams. The one or more patterned beams are directed to each of a plurality of regions on the powder layer. A two-dimensional gray-scale pattern is selected to achieve the desired material properties at each pixel position of the patterned beam incident on the powder layer. The light valve can modulate one or more of amplitude, phase, or coherence. The material properties can include one or more of Young's modulus, porosity, particle size, and crystal microstructure.

Description

Technical Field

[0001] [Cross - Reference to Related Applications] This application is a continuation - in - part of U.S. Patent Application No. 17 / 091,915, filed on November 6, 2020, which is a continuation - in - part of U.S. Patent Application No. 15 / 337,507, filed on October 28, 2016, which claims the benefit of the following provisional applications:

[0002] U.S. Patent Application No. 62 / 248,758, filed on October 30, 2015,

[0003] U.S. Patent Application No. 62 / 248,765, filed on October 30, 2015,

[0004] U.S. Patent Application No. 62 / 248,770, filed on October 30, 2015,

[0005] U.S. Patent Application No. 62 / 248,776, filed on October 30, 2015,

[0006] U.S. Patent Application No. 62 / 248,783, filed on October 30, 2015,

[0007] U.S. Patent Application No. 62 / 248,791, filed on October 30, 2015,

[0008] U.S. Patent Application No. 62 / 248,799, filed on October 30, 2015,

[0009] U.S. Patent Application No. 62 / 248,966, filed on October 30, 2015,

[0010] U.S. Patent Application No. 62 / 248,968, filed on October 30, 2015,

[0011] U.S. Patent Application No. 62 / 248,969, filed on October 30, 2015,

[0012] U.S. Patent Application No. 62 / 248,980, filed on October 30, 2015,

[0013] U.S. Patent Application No. 62 / 248,989, filed on October 30, 2015,

[0014] U.S. Patent Application No. 62 / 248,780, filed on October 30, 2015,

[0015] U.S. Patent Application No. 62 / 248,787, filed on October 30, 2015,

[0016] U.S. Patent Application No. 62 / 248,795, filed on October 30, 2015,

[0017] U.S. Patent Application No. 62 / 248,821, filed on October 30, 2015,

[0018] U.S. Patent Application No. 62 / 248,829, filed on October 30, 2015,

[0019] U.S. Patent Application No. 62 / 248,833, filed on October 30, 2015,

[0020] U.S. Patent Application No. 62 / 248,835, filed on October 30, 2015,

[0021] U.S. Patent Application No. 62 / 248,839, filed on October 30, 2015,

[0022] U.S. Patent Application No. 62 / 248,841, filed on October 30, 2015,

[0023] U.S. Patent Application No. 62 / 248,847, filed on October 30, 2015, and

[0024] U.S. Patent Application No. 62 / 248,848, filed on October 30, 2015.

[0025] This application is a continuation-in-part of U.S. Patent Application No. 15 / 977,476, filed on May 11, 2018, which claims the benefit of U.S. Provisional Patent Application No. 62 / 504,853, filed on May 11, 2017.

[0026] This application is a continuation-in-part of U.S. Patent Application No. 17 / 506,349, filed on October 20, 2021, which claims the benefit of U.S. Provisional Patent Application No. 63 / 105,066, filed on October 23, 2020.

[0027] This application is a continuation-in-part of U.S. Patent Application No. 17 / 513,005, filed on October 28, 2021, which claims the benefit of U.S. Provisional Patent Application No. 63 / 107,077, filed on October 29, 2020.

[0028] This application is a continuation-in-part of U.S. Patent Application No. 17 / 513,402, filed on October 28, 2021, which claims the benefit of U.S. Provisional Patent Application No. 63 / 107,303, filed on October 29, 2020.

[0029] This application is a continuation-in-part of U.S. Patent Application No. 17 / 513,230, filed on October 28, 2021, which claims the benefit of U.S. Provisional Patent Application No. 63 / 107,310, filed on October 29, 2020.

[0030] This application is a continuation-in-part of U.S. Patent Application No. 17 / 670,149, filed on February 11, 2022, which claims the benefit of U.S. Provisional Patent Application No. 63 / 148,788, filed on February 12, 2021. All of the foregoing documents are incorporated herein by reference.

[0031] [Technical Field] The present disclosure relates generally to optical systems for additive manufacturing, and more specifically to additive manufacturing that includes melting powder with a laser.

Background Art

[0032] Current Energy Deposited Printed Bed Fusion Additive Manufacturing (ED-PBF-AM) uses a single point of energy to melt powder (metallic, ceramic, glass, or vitreous materials) to form / print three-dimensional parts. This enables the rapid production of parts and the production of parts that cannot be manufactured with conventional machining techniques. Parts manufactured with this technology can be used for prototyping and can have sufficient strength and accuracy for product parts.

Brief Description of the Drawings

[0033] Non-limiting and non-exhaustive embodiments of the present disclosure are described with reference to the following drawings, and like reference numerals refer to like parts throughout the various drawings unless otherwise specified.

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DETAILED DESCRIPTION OF THE INVENTION

[0034] In the following description, reference is made to the accompanying drawings which form a part of the description and which illustrate, in a manner showing how the disclosure may be implemented, specific exemplary embodiments in which the disclosure may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the concepts disclosed herein, and it is understood that various changes may be made to the disclosed embodiments without departing from the scope of the disclosure and that other embodiments may be utilized. Therefore, the following detailed description should not be taken in a limiting sense.

[0035] The present disclosure proposes an optical system suitable for reducing the light discarded in an additive manufacturing system due to the waste of light that is unnecessary for the pattern to be printed. The proposed optical system can be used, for example, in laser-based additive manufacturing techniques where masking is applied to light, but is not limited thereto. Advantageously, in various embodiments of the present disclosure, the discarded energy can be recycled and used as homogenized and patterned light to maintain a high throughput rate. Further, the discarded energy can be recycled and reused to increase the intensity for printing of more difficult materials.

[0036] By recycling and reusing the wasted light, the strength of the system can be increased in proportion to the percentage of the wasted light. As a result, all energy can be utilized to maintain a high printing speed. Furthermore, the recycling of light potentially enables "bar" printing where a single bar sweeps across the build platform. Instead, the recycling of patterns can enable the creation of a solid-state matrix coextensive with the build platform that does not require movement to print across the entire area of the build platform.

[0037] In one embodiment, an additive manufacturing system is disclosed that has one or more energy sources positioned to emit one or more beam energies, such as one or more laser beams or electron beams. The beam shaping optics can receive the one or more beam energies from the energy source and form a single beam. The energy patterning unit can receive or generate the single beam, transfer a two-dimensional pattern onto the beam, and discard unused energy not in the pattern. The image relay receives the two-dimensional patterned beam and focuses the beam as a two-dimensional image at a desired location on a build platform (e.g., a powder bed) with a fixed or movable height. In certain embodiments, some or all of any wasted energy from the energy patterning unit is reused.

[0038] In various examples, multiple beams from a laser array are combined using a beam homogenizer. The combined beam can be directed to an energy patterning unit that includes a pixel-addressable light valve, either transmissive or reflective. In one embodiment, the pixel-addressable light valve includes both a liquid crystal module with a polarization element and a light projection unit that supplies a two-dimensional input pattern. The two-dimensional image focused by the image relay can be sequentially directed to multiple locations on the powder bed to build a three-dimensional structure.

[0039] An additive manufacturing system can use a grayscale pattern to control material properties corresponding to each pixel position of the pattern. The material properties can include Young's modulus, porosity, particle size, and microcrystalline structure. The grayscale pattern can be added to the beam by a light valve that modulates one or more of amplitude, phase, and coherence.

[0040] As seen in FIG. 1, an additive manufacturing system 100 has an energy patterning system 110 with an energy source 112 that can direct one or more beams of continuous or intermittent energy to a beam shaping optic 114. After shaping, if necessary, generally some energy is directed to a waste energy processing unit 118 while the beam is patterned by an energy patterning unit 116. The patterned energy is typically relayed by an image relay 120 to an article processing unit 140 as a two-dimensional image 122 focused near a floor 146. The floor 146 (with optional walls 148) can form a chamber containing a material 144 metered by a material dispenser 142. The patterned energy directed by the image relay 120 can melt, fuse, sinter, coalesce, change the crystal structure, impart a stress pattern, or otherwise chemically or physically alter the metered material 144 to form a structure having the desired properties.

[0041] The energy source 112 generates photons (light), electrons, ions, or other suitable beam energy or flux that can be directed, shaped, and patterned. Multiple energy sources can be used in combination. The energy source 112 can include a laser, white light, concentrated sunlight, other light sources, an electron beam, or an ion beam. Possible types of lasers include, but are not limited to, gas lasers, chemical lasers, dye lasers, metal vapor lasers, solid state lasers (e.g., fiber), semiconductor (e.g., diode) lasers, free electron lasers, gas dynamic lasers, "nickel-like" samarium lasers, Raman lasers, or nuclear-excited lasers.

[0042] The gas laser may include lasers such as a helium-neon laser, an argon laser, a krypton laser, a xenon ion laser, a nitrogen laser, a carbon dioxide laser, a carbon monoxide laser, or an excimer laser.

[0043] The chemical laser may include lasers such as a hydrogen fluoride laser, a deuterium fluoride laser, a COIL (chemical oxygen iodine laser), or an Agil (all-gas-phase iodine laser).

[0044] The metal vapor laser may include lasers such as a helium-cadmium (HeCd) metal vapor laser, a helium-mercury (HeHg) metal vapor laser, a helium-selenium (HeSe) metal vapor laser, a helium-silver (HeAg) metal vapor laser, a strontium vapor laser, a neon-copper (NeCu) metal vapor laser, a copper vapor laser, a gold vapor laser, a manganese (Mn / MnCl2) vapor laser.

[0045] The solid state laser includes a ruby laser, a Nd:YAG laser, a NdCrYAG laser, an Er:YAG laser, a neodymium YLF (Nd:YLF) solid state laser, a neodymium-doped yttrium orthovanadate (Nd:YVO4) laser, a neodymium-doped yttrium calcium oxoborate Nd:YCa4O(BO3) 3 Or simply Nd:YCOB, a neodymium glass (Nd:glass) laser, a titanium sapphire (Ti:sapphire) laser, a thulium YAG (Tm:YAG) laser, a ytterbium YAG (Yb:YAG) laser, a ytterbium:2O3 (glass or ceramic) laser, a ytterbium-doped glass laser (rod, plate / chip, and fiber), a holmium YAG (Ho:YAG) laser, a chromium ZnSe (Cr:ZnSe) laser, a cerium-doped lithium strontium (or calcium) aluminum fluoride (Ce:LiSAF, Ce:LiCAF), a promethium 147-doped phosphate glass (147Pm +3: It may include lasers such as glass solid-state lasers, chromium-doped chrysoberyl (alexandrite) lasers, erbium-doped and erbium-yttrium co-doped glass lasers, trivalent uranium-doped calcium fluoride (U:CaF2) solid-state lasers, divalent samarium-doped calcium fluoride (Sm:CaF2) lasers, or F-center lasers.

[0046] Semiconductor lasers may include laser media such as GaN, InGaN, AlGaInP, AlGaAs, InGaAsP, GaInP, InGaAs, InGaAsO, GaInAsSb, lead salts, vertical-cavity surface-emitting lasers (VCSELs), quantum cascade lasers, hybrid silicon lasers, or combinations thereof.

[0047] For example, in one embodiment, a single Nd:YAG q-switch laser can be used together with a plurality of semiconductor lasers. In another embodiment, an electron beam can be used together with an ultraviolet semiconductor laser array. In yet another embodiment, a two-dimensional array of lasers can be used. Pre-patterning of the beam energy can be achieved by selectively activating and deactivating the energy source.

[0048] The beam shaping unit 114 can include a wide variety of imaging optical systems for combining, focusing, branching, reflecting, refracting, homogenizing, adjusting the intensity, adjusting the frequency, or otherwise shaping one or more beam energies received from the energy source 112 and directing them to the energy patterning unit 116. In one embodiment, multiple optical beams having different optical wavelengths can be combined using a wavelength-selective mirror (e.g., dichroic) or a diffractive element. In other embodiments, multiple beams can be homogenized or combined using a polygon mirror, a microlens, and refractive or diffractive optical elements.

[0049] The energy patterning unit 116 may include static or dynamic energy patterning elements. For example, photons, electrons, or ion beams may be blocked by masks in fixed or movable elements. Pixel-addressable masking, image generation, or transmission may be used to increase the degree of freedom and ease of image patterning. In some embodiments, the energy patterning unit includes a single addressable light valve or a combination with other patterning mechanisms for providing patterning. The light valve may transmit, reflect, or use a combination of transmission elements and reflective elements. The pattern may be dynamically changed using electrical or optical addressing. In one embodiment, a transmissive optically addressed light valve acts to rotate the polarization of light passing through the valve, together with optically addressed pixels that form a pattern defined by a light projection source. In another embodiment, a reflective optically addressed light valve includes a write beam for changing the polarization of a read beam. In yet another embodiment, an electronic patterning device receives an address pattern from an electrical or photon stimulation source and generates a patterned emission of electrons.

[0050] The waste energy processing unit 118 is used to dissipate, redirect, and utilize the energy that has passed through the non-patterned energy pattern image relay 120. In one embodiment, the waste energy processing unit 118 may include passive or active cooling elements that remove heat from the energy patterning unit 116. In other embodiments, the waste energy processing unit may include a "beam dump" for absorbing any beam energy not used in the definition of the energy pattern and converting it to heat. In yet other embodiments, the wasted beam energy may be recycled using the beam shaping optics 114. Alternatively, or in addition, the wasted beam energy may be directed to the article processing unit 140 for heating or further patterning. In some embodiments, the wasted beam energy may be directed to an additional energy patterning system or the article processing unit. Any of the above-described techniques may be used in combination in the waste energy processing unit 118 to dissipate, redirect, or utilize the energy that has passed through the non-patterned energy pattern image relay 120.

[0051] The image relay 120 receives the patterned image (typically two-dimensional) from the energy patterning unit 116 and directs it to the article processing unit 140. In a manner similar to the beam shaping optics 114, the image relay 120 may include optics for combining, focusing, splitting, reflecting, refracting, adjusting the intensity, adjusting the frequency, or otherwise shaping and directing the patterned image.

[0052] The article processing unit 140 may include a walled chamber 148, a floor 144, and a material dispenser 142 for dispensing materials. The material dispenser 142 can dispense materials, remove them, mix them, provide a gradation or change in the type of material or the size of the particles, or adjust the thickness of the layer. The materials can include metals, ceramics, glasses, polymer powders, other soluble materials that can be thermally induced from solids to liquids and back to solids, or combinations thereof. The materials can further include composite materials of soluble and insoluble materials, in which either only the insoluble material remains, or either or both components are selectively targeted by the image relay system to dissolve the soluble component while undergoing either evaporation / destruction / combustion or other destructive processes. For example, slurries, sprays, paint films, wires, pieces, or sheets of materials can be used. Unwanted materials can be removed for disposal or recycling by means of a blower, the use of a vacuum system, sweeping of the floor 146, vibration, shaking, tilting, or inversion.

[0053] In addition to the material processing components, the article processing unit 140 may include components for holding and supporting three-dimensional structures, mechanisms for heating or cooling the chamber, auxiliary or supporting optical systems, and sensors and control mechanisms for monitoring or adjusting the materials or environmental conditions. The article processing unit may enable a vacuum or gas atmosphere, either in whole or in part, to reduce the risk of fire or explosion (especially with highly reactive metals) and to reduce unwanted chemical interactions.

[0054] The control processor 150 can be connected to control any component of the additive manufacturing system 100. The control processor 150 can be connected to various sensors, actuators, heating or cooling systems, monitors, and controllers to coordinate operations. A wide range of sensors can be used, including imaging devices, light intensity monitors, thermal sensors, pressure sensors, or gas sensors, to provide information for control or monitoring. The control processor can be a single central controller or, alternatively, can include one or more independent control systems. The control processor 150 has an interface through which manufacturing instructions can be input. The wide use of sensors enables various feedback control mechanisms that can improve quality, manufacturing throughput, and energy efficiency.

[0055] FIG. 1B is a diagram illustrating a floor 146 that supports a material 144. Using a series of two-dimensional patterned beam energy images (the quadrilateral of the dotted outline 124) applied continuously, the structure 149 is additionally manufactured. Of course, image patterns with non-rectangular boundary lines can be used, overlapping or interpenetrating images can be used, and images can be provided by two or more energy patterning systems. In other embodiments, the image can be formed with directed electron or ion beams or with printing or selective spraying systems.

[0056] FIG. 2 is a flowchart illustrating one embodiment of an additive manufacturing process enabled by the disclosed opto-mechanical components. In step 202, the material is positioned on a floor, in a chamber, or other suitable support. The material can be a powder that can be melted, fused, sintered, or induced to change its crystal structure, that affects the formation of a structure having desired properties, or that has a stress pattern that is chemically or physically altered.

[0057] In step 204, the unpatterned energy is emitted by one or more energy emitters including, but not limited to, a solid state laser or a semiconductor laser, or a power supply device that passes electrons under the wire. In step 206, the unpatterned energy is shaped and modified (e.g., the intensity is modulated or focused). In step 208, this unpatterned energy is patterned together with the energy that does not form part of the pattern being processed in step 210 (which may include conversion to waste heat or recycling as patterned or unpatterned energy). In step 212, the patterned energy that is currently forming the two-dimensional image is relayed towards the material. In step 214, the image is applied to the material to build part of the three-dimensional structure. These steps can be repeated (loop 218) until the image (or a different subsequent image) is applied to all the required areas of the top layer of the material. When the application of energy to the top layer of the material is complete, a new layer can be applied to continue building the three-dimensional structure (loop 216). If any remaining excess material can be removed or recycled, the loop of these steps continues until the three-dimensional structure is complete.

[0058] Figure 3A is an embodiment of an additive manufacturing system 300 that uses a plurality of semiconductor lasers as part of an energy patterning system 310. A control processor 350 can be connected to various sensors, actuators, heating or cooling systems, monitors, a controller for coordinating the operation of the plurality of lasers 312, the optical patterning unit 316, the image relay 320, and any other components of the system 300. These connections are generally indicated by the dotted outline 351 surrounding the components of the system 300. As will be understood, the connections can be wired or wireless, can be continuous or intermittent, and can include a feedback function (e.g., heating can be adjusted according to the sensed temperature). The plurality of lasers 312 can emit a beam 301 of light having a wavelength of 1000 nm that is, for example, 90 mm wide at a height of 20 mm. The beam 301 is sized by an imaging optical system 370 to create a beam 303. In one example, the beam 303 is 6 mm high and 6 mm wide and is incident on a light homogenizer 372 that mixes the light to create a mixed beam 305. The beam 305 then enters an imaging assembly 374 that reshapes the light into a beam 307 and then enters a thermo - cold mirror 376. The mirror 376 can allow transmission of light of a first wavelength but reflect a second wavelength. For example, it can pass light at 1000 nm but reflect 450 nm. An optical projector 378 capable of projecting low - power light at 450 nm with, for example, 1080p pixel resolution emits a beam 309, which then enters the thermo - cold mirror 376. The beam 309 can be a two - dimensional pattern (e.g., an image) where each pixel of the pattern can be independently controlled. The intensity of each pixel can be independently set within a range of possible values such that the two - dimensional pattern is a grayscale pattern. As used herein, "grayscale" should be understood to mean at least three levels including zero intensity, maximum intensity, and one or more intensities between zero and maximum. For example, the number of levels can be at least 8, at least 16, at least 32, at least 64, at least 128, or any value of 2^N or more where N is greater than 1.The grayscale patterns or images used in this specification do not necessarily include each of several levels. Rather, they should include at least three levels that are not identical to each other, and each level can be selected from the available range of levels. Beams 307 and 309 are superimposed on beam 311, and both are imaged on the optical address light valve 380, for example, with an image having a width of 20 mm and a height of 20 mm. The images formed from the homogenizer 372 and the projector 378 are recreated and superimposed on the light valve 380.

[0059] The optical address light valve 380 is stimulated by light (the wavelength of the light in the example can have a width from 400 to 500 nm) and embosses a polarization rotation pattern onto the transmitted beam 313 incident on the polarizer 382. The polarizer 382 splits the two polarization states, transmits the p-polarization into beam 317, and reflects the s-polarization into beam 315, which is then sent to the beam dump 318 that processes the waste energy. Naturally, in other embodiments, the polarizations could be swapped such that the s-polarization is formed in beam 317 and the p-polarization is reflected into beam 315. Beam 317 enters the final imaging assembly 320 that includes an optical system 384 that sizes the patterned light. This beam is reflected from the movable mirror 386 to beam 319 and terminates in a focused image applied to the material bed 344 in the article processing unit 340. The depth of field of the image is selected to spread over multiple layers, and optimal focus is provided within the range of a few layers of error or offset.

[0060] The optical address light valve 380 can be implemented as various optical devices that affect other characteristics of the beam 307 output by the laser 312 in response to the patterned beam 309, which can be a grayscale patterned beam. The frequency used for the patterned beam 309 corresponds to the frequencies required to add patterns to the various optical devices used in the following example.

[0061] In a first alternative example, the polarizer 382 is omitted and the light valve 380 is implemented as the light valve described in 17 / 506,349. In such an embodiment, the light valve 380 may include a photoconductive layer and an electro-optic layer between transparent conductive oxide layers. The patterned beam 309 illuminates the photoconductive layer as a scan beam that creates a two-dimensional grayscale pattern defining a two-dimensional grayscale pattern or a two-dimensional image. In either case, the intensity and / or wavelength at each position within the two-dimensional pattern is independently controllable to add the two-dimensional grayscale pattern to the photoconductive layer. Due to the two-dimensional grayscale pattern added to the photoconductive layer, the corresponding two-dimensional grayscale pattern is added to the beam 307 incident on the light valve 380, and as a result, the output beam 313 exits the light valve 380 with the corresponding grayscale pattern. Thereafter, the output beam 313 enters the final imaging optics 320 without first passing through the polarizer 382.

[0062] In a second alternative example, the light valve 380 adds a patterned phase change to the beam 307 and the polarizer 382 is implemented as a pattern separator with phase-dependent transmissivity as described in 17 / 513,005. The light valve 380 may include a phase change material (e.g., crystal, amorphous, liquid crystal, glass, ceramic, polymer, quantum dot, artificial dielectric, plasmon or metal material). In other examples, a pixel strained phase change light valve is used. The phase change light valve is written by a two-dimensionally patterned write beam that can be a grayscale pattern. As the beam 307 passes through the phase change light valve, it passes through a two-dimensional pattern of localized phase changes to obtain a beam 313 with a two-dimensional phase pattern added. The beam 313 then passes through a pattern separator with phase-dependent transmissivity, resulting in a beam 317 with a two-dimensional amplitude pattern corresponding to the two-dimensional grayscale pattern.

[0063] In a third alternative embodiment, the polarizer 382 is omitted, and the light valve 380 is a quantum dot resonance-based light valve (QDRLV) or a diffractive light valve controlled by quantum dot resonance, as described in 17 / 513,402, that includes a two-dimensional gray scale pattern and is illuminated by the patterned beam 309. The beam 307 is incident on the light valve 380, and the beam 313 exiting the light valve 380 has a two-dimensional amplitude pattern corresponding to the two-dimensional gray scale pattern. The beam 313 may then be incident on the final imaging optics 320.

[0064] In a fourth alternative embodiment, the polarizer 382 is omitted, and the light valve 380 is a holographic light valve as described in 17 / 670,149. The holographic light valve 380 may include a photoconductive layer illuminated by a two-dimensional gray scale writing pattern in the beam 309. The beam 309 has a first frequency and is applied to a plurality of transparent conductive oxide (TCO) layers to form a photoconductive layer for adding a corresponding two-dimensional patterned field. As the beam passes through the TCO layer, the TCO layer adds a corresponding two-dimensional phase pattern to the beam 307. A lambda magic mirror (LMM) is illuminated by a two-dimensional gray scale writing pattern at a second frequency different from the first frequency. The LMM adds a gray scale amplitude pattern to the phase-patterned beam output by the TCO layer such that the beam 313 output from the light valve 380 is a high-flux beam that is phase-patterned and amplitude-patterned. The beam 313 may then be incident on the final imaging optics 320.

[0065] In a fifth alternative embodiment, the light valve is an LMM as described in 17 / 513,402. When the beam 307 is incident, the coherence changes locally across the LMM, and a portion of the beam 307 is directed according to the change in coherence, resulting in a beam 313 having a two-dimensional amplitude pattern corresponding to the two-dimensional gray scale writing pattern. The LMM is illuminated by the two-dimensional gray scale writing pattern from the projector 378.

[0066] In the sixth example, the light valve 380 is replaced by a high-speed electron beam addressable reflective light valve (EBA-RLV) as described in 17 / 091,915 and 17 / 513,230. The beam 307 is incident on the EBA-RLV. The projector 378 and polarizer 382 can be emitted and replaced by an electron beam scanner. The electron beam is scanned across the EBA-RLV, and a two-dimensional grayscale pattern is added thereto. The voltage of the electron beam can be modulated to add a two-dimensional grayscale pattern to the EBA-RLV when scanned across it. The beam 307 is incident on the EBA-RLV, and the reflective portion having a two-dimensional amplitude pattern corresponding to the two-dimensional grayscale pattern is used as the beam 313. The beam 313 can then be incident on the final imaging optics 320.

[0067] The bed 390 can be raised and lowered (vertically pulled) within the chamber wall 388 containing the material 344 quantitatively supplied by the material dispenser 342. In some embodiments, the bed 390 can remain fixed, and the optics of the final imaging assembly 320 can be raised and lowered vertically. The dispensing of the material is supplied by a sweep mechanism 392 that can uniformly spread the powder held in the hopper 394 and can supply a new layer of material as needed. For example, an image 6 mm high and 6 mm wide is sequentially directed by the movable mirror 386 at various positions on the bed.

[0068] In this additive manufacturing system 300, when using a powdered ceramic or metal material, as the part is built, the powder can spread into a thin layer about 1 to 3 particles thick above the top of the substrate (and subsequent layers). When the powder is melted, sintered, or fused by the patterned beam 319, the powder bonds to the underlying layer, creating a solid structure. The patterned beam 319 can operate in a pulsed mode at 40 Hz and move to subsequent 6 mm × 6 mm image positions at intervals of 10 ms to 0.5 ms (in various examples the interval range is 3 ms to 0.1 ms) until the selected patterned area of the powder is melted. The bed 390 then lowers itself by a thickness corresponding to one layer, and the sweep mechanism 392 spreads a new layer of the powder material. This process is repeated until a three-dimensional structure with the desired two-dimensional layers is built. In some embodiments, the article processing unit 340 can have a controlled atmosphere. This allows reactive materials to be manufactured in an inert gas or vacuum environment without the risk of oxidation or chemical reaction (when highly reactive metals are used), or fire or explosion.

[0069] Figure 3B illustrates the operation of the optical patterning unit 316 of Figure 3A in more detail. As seen in Figure 3B, a representative input pattern 333 (seen here as the digit "9") is defined by an 8×12 pixel array of light projected as beam 309 towards mirror 376. The white pixels are unlit and each gray pixel represents a bright pixel. In practice, each pixel can have various light levels including light-free, partial light intensity, and maximum light intensity. The unpatterned light 331 forming beam 307 is directed and passed through the thermo-cooled mirror 376 where the light 331 combines with the patterned beam 309. The patterned beam 309 is generated by an optical projector 378 controlled by computer X3 via cable X5. After reflection by the thermo-cooled mirror 376, a patterned light beam 311 is formed from the superposition of beam 307 and beam 309 in beam 311 and both are imaged onto the optical address light valve 380. The optical address light valve 380, which rotates the polarization state of the unpatterned light 331, is stimulated by the patterned light beams 309 / 311 and the electrical signal arriving from computer X3 via cable X4 so as not to selectively rotate the polarization state of the polarized light 307 / 311 in the pattern of the digit "9" into beam 313. The non-rotated light representing pattern 333 in beam 313 can then pass through the polarizer mirror 382 resulting in beam 317 and pattern 335. The light polarized in the second rotation state is discarded by the polarizer mirror 382 into beam 315 carrying the negative pixel pattern 337 composed of the digit "9" with no light.

[0070] Other types of light valves may be substituted for, or used in combination with, the described light valve. Reflective light valves, or light valves based on diffraction or refraction, may also be used. In some embodiments, non-optical addressable light valves may be used. These may include, but are not limited to, electrically addressable pixel elements, movable mirrors or micromirror systems, piezoelectric or microactuated optical systems, fixed or movable masks, or stencils, or other conventional systems that can provide high contrast patterning. For electron beam patterning, these valves may selectively emit electrons based on the address position, and as a result, a pattern may be infiltrated onto the beam of electrons leaving the valve.

[0071] Figure 3C illustrates the details and operation of the energy switching unit X0. As seen in Figure 3C, a beam of light 311 carrying a representative input pattern 376 in the S polarization state (here seen as the number "9" in an 8×12 pixel array) is incident on a single pixel liquid crystal (LC) cell 380. The LC cell 380, which rotates the polarization state of the beam 311 if desired, is a computer X3 that is electrically stimulated via cable X4 to selectively rotate the polarization state of the polarization 311 to the p polarization state at beam 313, so that the entire beam then passes through the polarizer 382 to become a beam 317 carrying image information 335. Alternatively, the LC cell 380 may be instructed by the computer X3 via cable X4 not to rotate the polarization state of the beam 311, thereby maintaining the S polarization state of the beam 313 and causing reflection to a beam 315 carrying image information 337. The polarizer 382 may also be used to receive light from the source beam X1 carrying the image information X2. The route of the beam X1 is completely passive based on its polarization state, reflecting to the beam 317 if X1 is in the S polarization state and proceeding to the beam 315 if in the p polarization state (or vice versa).

[0072] As an alternative to or in combination with the LC cell described above, other types of energy switching devices may be used. The reflective LC cell or energy switching device may be based on mechanical movement such as a movable mirror, or selective refraction may also be utilized, and piezoelectric or microactuated optical systems, fixed or movable masks, or reticles, or any other conventional system capable of providing high-intensity energy switching may also be used. With respect to an electron beam, these switching mechanisms may consist of a large electromagnetic field array that directs the beam to various channels or routes.

[0073] Figure 3D is an embodiment of an additive manufacturing system that includes a switched system capable of reusing patterned two-dimensional energy. Similar to the embodiment discussed with respect to Figure 1A, the additive manufacturing system 220 has an energy patterning system with an energy source 112 that directs one or more continuous or intermittent beam energies to a beam shaping optics 114. After shaping, the beam generally has some energy directed to a waste energy processing unit 222 and is two-dimensionally patterned by an energy patterning unit 230. The patterned energy is typically relayed by one of a plurality of image relays 232 towards one or more article processing units 234A, 234B, 234C, or 234D as a two-dimensional image focused near a floor of variable or fixed height. The floor (along with optional walls) may form a chamber containing material metered by a material dispenser. The patterned energy directed by the image relay 232 may melt, fuse, sinter, fuse, change to a crystal structure, impart a stress pattern, or otherwise chemically or physically alter the metered material 144 to form a structure having the desired properties.

[0074] In this embodiment, the waste energy processing unit has a plurality of components to enable the reuse of patterned waste energy. Repeaters 228A, 228B, and 228C can respectively relay energy to generator 224, heating / cooling thermal management system 225, or energy damper 226. Optionally, repeater 228C can direct the patterned energy to image repeater 232 for further processing. In other embodiments, the patterned energy can be directed by repeater 228C to repeaters 228B and 228A for insertion into the beam energy supplied by energy source 112. Using image repeater 232, the reuse of the patterned image is also possible. The image can be redirected, inverted, reflected, sub-patterned, or converted for distribution to one or more article processing units 234A through D. Advantageously, the reuse of the patterned light can improve the energy efficiency of the additive manufacturing process, and in some cases, can improve the energy intensity directed to the floor, or reduce the manufacturing time.

[0075] FIG. 3D is a diagram 235 illustrating a simple geometric transformation of waste beam energy for reuse. Input pattern 236 is directed to image repeater 237, which can supply mirror image pixel pattern 238. As can be understood, more complex image transformations are possible, including geometric transformations or pattern rearrangement of individual pixels and groups of pixels. Instead of being discarded in a beam dump, this rearranged pattern can be directed to an article processing unit to improve manufacturing throughput or beam intensity.

[0076] FIG. 3E is a diagram 235 illustrating multiple transformations of waste beam energy for reuse. Input pattern 236 is directed to a series of image repeaters 237B - E that can supply pixel pattern 238.

[0077] In another embodiment that supports optical recycling and reuse, multiple beams of light from one or more light sources are provided. The multiple beams of light may be reshaped and mixed to provide a first beam of light. A spatial polarization pattern may be applied to the first beam of light to provide a second beam of light. The polarization state of the second beam of light may be split to reflect a third beam of light and may be reshaped into a fourth beam of light. The fourth beam of light may be introduced as one of the multiple beams of light and may result in a fifth beam of light. In fact, this or a similar system may reduce the energy costs associated with an additive manufacturing system. By collecting, beam combining, homogenizing, and reintroducing unwanted light discarded by a spatial polarization valve or optical valve operating in a polarization change mode, the overall transmitted optical power may not be affected by the pattern applied by the optical valve. This advantageously results in an effective redistribution of the light passing through the desired pattern via the optical valve and increases the light intensity in proportion to the amount of the patterned area.

[0078] Combining beams from multiple lasers into a single beam is one way to increase beam intensity. In one embodiment, multiple optical beams each having a different optical wavelength may be combined using either a wavelength selective mirror or a diffractive element. In some embodiments, reflective optical elements that are not sensitive to the effects of wavelength-dependent refraction may be used to direct multi-wavelength beams.

[0079] The patterned light can be directed using a movable mirror, prism, diffractive optical element, or a solid-state optical system that does not require substantial physical movement. In one embodiment, the intensity of the incident light at the position of the top surface of the powder bed and the magnification and image distance associated with the pixel size can be determined for an additive manufacturing 3D printing job. One of the plurality of lens assemblies can be an assembly of both a first set of optical lenses and a second set of optical lenses, and also a second set of optical lenses exchangeable from the lens assembly, configured to provide incident light having the magnification. The rotation of one or more sets of mirrors mounted on a compensating gantry and a final mirror mounted on a build platform gantry can be used to direct the incident light from a preceding mirror to the position of the top surface of the powder bed. The translational movement of the compensating gantry and the build platform gantry can also make the distance of the incident light from the preceding mirror to the position of the top surface of the powder bed substantially equal to the image distance. In fact, this leads to ensuring high availability of the system while enabling rapid changes in the emission size and intensity of the optical beam across the position of the build area for various powder materials.

[0080] A plurality of build chambers, each having a build platform for holding a powder bed, can be used with a plurality of optomechanical assemblies optionally arranged to receive and direct one or more incident beam energies into the build chambers. The plurality of chambers enables simultaneous printing of one or more printing jobs inside one or more build chambers. Movable chamber sidewalls can facilitate removal of printed objects from the build chamber and enable rapid exchange of powder materials. The chamber can also include adjustable process temperature control.

[0081] One or more build chambers may have a build chamber in which the optical system is vertically movable while being maintained at a fixed height, as described above. The distance between the final optical system of the lens assembly and the uppermost surface of the powder bed can be managed to be constant in principle by pulling the final optical system upward by a distance equal to the thickness of the powder layer while keeping the build platform at a fixed height. Advantageously, since an accurate micron-scale movement of the continuously changing mass of the build platform is not required compared to moving the build platform vertically, larger and heavier objects can be manufactured more easily. Typically, build chambers targeted at metal powders having a volume exceeding 0.1 to 0.2 cubic meters (i.e., heavier than 100 to 200 liters or 500 to 1000 kg) will benefit most from keeping the build platform at a fixed height.

[0082] Optionally, a portion of the layer of the powder bed can be selectively melted or fused to form one or more temporary walls outward from the melted portion of the layer of the powder bed to enclose another portion of the layer of the powder bed on the build platform. Fluid passages can be formed in one or more of the first walls to improve thermal management.

[0083] Improved powder handling can be another aspect of an improved additive manufacturing system. The build platform supporting the powder bed can be tiltable, invertible, and vibratable to substantially separate the powder bed from the build platform in a hopper. The powder material forming the powder bed may be collected in the hopper for reuse in subsequent printing jobs. The powder collection process may be automated, and a vacuum or gas injection system may also be used to assist in the removal and evacuation of the powder.

[0084] Some embodiments of the disclosed additive manufacturing systems may be configured to readily process parts that are longer than the available chambers. A continuous (long) part may sequentially advance vertically from a first zone to a second zone. In the first zone, selected particles of the particulate material may be fused. In the second zone, unfused particles of the particulate material may be removed. The last portion of the continuous part is formed within the first zone, and the first portion of the continuous part may advance from the second zone to a third zone while maintaining the first portion in the same position in the lateral and transverse directions occupied by the first portion within the first and second zones. In fact, additive manufacturing and cleaning (e.g., separation and / or recycling or reuse of unfused particulate material) may be performed in parallel (i.e., simultaneously) at different positions or zones on the part conveyor without the need to stop for removal of the particulate material and / or parts.

[0085] Optionally, the additive manufacturing capabilities may be enhanced by use of an enclosure that restricts the exchange of gases between the interior and exterior of the enclosure. The hermetic chamber has a plurality of additive manufacturing chambers and provides a contact between their interior, including the supported powder bed melting, and the exterior. The gas management system maintains the gas oxygen inside below the limiting oxygen concentration, thereby increasing the freedom in the types of powders and processes that can be used within the system.

[0086] Performance may be enhanced by having a three-dimensional printer contained within the enclosure, the three-dimensional printer being capable of creating parts having a weight of 2000 kilograms or more. The gas management system may maintain the gas oxygen within the enclosure at a concentration below the atmospheric concentration. In some embodiments, the hermetic chamber serves as a buffer between the gas environment inside the enclosure and the gas environment outside the enclosure, so that the vehicle may carry parts from the inside of the enclosure to a location outside the enclosure and the hermetic chamber via the hermetic chamber.

[0087] Optionally, collecting a sample can be collecting a powder sample in real time in a powder bed fusion additive manufacturing system. An intake system is used for in-process collection and characterization of the powder sample. The collection may be performed periodically, and the results of the characterization lead to adjustments to the powder bed fusion process. The intake system can be used incidentally to one or more audits, process adjustments, or operations, such as changing printer parameters or verifying proper use of an approved powder material.

[0088] Yet another improvement of the additive manufacturing process is provided by the use of manipulation devices such as cranes, lifting gantries, robotic arms, or the like that can manipulate parts that are difficult or impossible for a person to move. The manipulation device can grasp various permanent or temporary additive manufacturing operation points on the part so as to reposition or manipulate the part.

[0089] According to the present disclosure, an optical system is provided that can recycle discarded, unwanted, and / or unused light. Recycling and reusing unwanted light can increase the intensity of the laser emission light provided to the build platform. Further, recycling and reusing unwanted light can reduce the energy costs associated with the system. By collecting, beam combining, homogenizing, and reintroducing the discarded unwanted light with a spatial polarization valve or light valve operating in a polarization change mode, the overall transmitted optical power may not be affected by the pattern applied by the light valve. This advantageously results in an effective redistribution of the light passing through the desired pattern through the light valve, increasing the light intensity in proportion to the amount of the patterned area. This relates to advanced additive manufacturing methods using powder bed fusion techniques (such as those described herein from FIGS. 1A to 3B), and in particular, applications using laser additive manufacturing. This is because the increased intensity enables shortening of the dwell time and increase of the printing speed, increasing the material conversion rate while maintaining efficiency.

[0090] By means of a light valve or a light modulator, the spatial pattern of light can be engraved into the light beam. When the light intensity is related to the concern or performance index of an optical system, the maintenance of system power is a priority. Liquid crystal-based devices can pattern a polarized beam by selectively rotating the "pixels" in the polarized beam and then passing the polarized beam through a polarizer to separate the rotated pixels from the non-rotated pixels. Instead of emitting the discarded polarization state, photons can be combined with and homogenized with the first input beam towards the light valve. The optical path can be separated into three segments: 1) the optical transmission fraction (denoted as f1 in this specification) between the light source and the light valve, 2) the optical transmission fraction (denoted as f2 in this specification) between the light valve and the light, such as in a loop portion, and the fraction of the light valve that is patterned for the desired transmission state (denoted as f p as shown). The final optical power can be expressed as in Equation 1 below. Equation 1

Number

[0091] Thus, according to Equation 1, as the transmission fractions f1 and f2 increase to the perfect value of 1, the final power becomes equal to the initial power regardless of the fraction of the patterned beam. The final intensity rises relative to the initial intensity that is proportional to the amount of the patterned area. This increased intensity requires compensation in the dwell time, which is obvious.

[0092] One exemplary implementation of this concept is in the field of additive manufacturing that uses a laser to melt layers of powder of a material. Without beam recycling, as the curvature factor of the area to be patterned decreases, the material printing speed also decreases, thereby reducing the overall mass production speed of the printer. The compensation in dwell time due to light recycling is such that the dwell time becomes non-linearly shorter due to the higher intensity. The shorter dwell time tends to result in an even higher printing speed and overall mass conversion speed. Thanks to this ability to increase the speed of material printing for low curvature factor printing areas, additive manufacturing machines are able to maintain a high level of powder up to engineered shape conversion rates, which leads to higher performance products.

[0093] A further exemplary implementation of this concept is in the use of a bar of light that is modulated on and off to create a two-dimensional (2D) layer of individuals from a powder substance as it sweeps across a build platform. The use of recycled light in this example is novel. To use a bar that sweeps across the entire build platform, it needs to be able to print at 100% curvature factor all the time. However, typically only 10 to 33% of the build platform has been used. This low curvature factor means that the capital equipment for laser power is on average 3 to 10 times excessive for the system. However, when the light is recycled, the sweep speed of the bar is adjusted to match the required dwell time that is proportional to the curvature factor, and the printing speed can be increased to be close to the optimal curvature factor efficiency. In such a case, the capital equipment can be fully utilized. Thanks to the ability to print with a bar of sweeping light, printing in a single direction becomes possible, and the gantry system required to move the light around can be simplified. Thanks to such an ability, the integration of the powder sweep mechanism also becomes easier.

[0094] A further exemplary implementation of the printed bar concept includes a powder dispensing system that places the next layer of powder following the bar as the previous layer is printed. Advantageously, this can minimize the system's downtime.

[0095] Another exemplary implementation of light recycling is to share light with one or more other printing chambers. Thanks to this example, the available laser light can appear to be a substantially on-demand resource, just like electricity is available from a wall outlet.

[0096] As described above with reference to FIG. 2, light recycling need not be limited to the reuse of a homogenized and patternless light beam. Reuse of a patterned image is also possible, and the discarded light pattern can be inverted, reflected, sub-patterned, or otherwise converted for distribution to one or more article processing units. One embodiment of recycling light is shown in FIG. 4A, which illustrates an energy patterning binary tree system 400 that can generate 2 n images from one input 401 and (2 n -1) patterning levels 402a-d. At each stage, “positive” light patterns and “negative” or discarded light pattern counterparts can be created and directed to additional patterning units or can be directed as patterned output 408. Each light pattern can be further modified through a multi-stage transformation 404 that can modify the pattern, reduce the intensity in selected pattern regions, or change the characteristics of the light.

[0097] Figure 4B is a diagram 410 illustrating the reuse of a pattern from one input 411 to multiple outputs 414 by the combined use of optical patterning and the directing mechanism 412. In this example, four output paths are provided. That is, a first possible output path without patterned light, a second output path having a reduced light intensity and the same pattern as the input pattern 411 except for being reflected, a third output path having a new pattern created by optical pixel redirection, and a fourth output path having a pattern that is sufficiently small and has an increased intensity. As will be understood, these patterns are merely examples, and with appropriate adjustment, a wide variety of output patterns with smaller, larger, different-shaped, or lower / higher light intensity patterns can be formed. In some embodiments, the output pattern can be changed by, for example, light reflection or inversion of the entire input image, and in other embodiments, adjustment at the pixel block level or individual pixel level is possible.

[0098] Figure 4C is a diagram 420 illustrating the reuse of a pattern from multiple inputs 421 to an output 424 by the combined use of optical patterning and the directing mechanism 422. In this example, the four input patterns are combined into a high-intensity output 424 by rotating or inverting the optical input patterns 2, 3, and 4 to match and combine with the input pattern 1. Similar to Figure 4B, it should be understood that these patterns are merely examples and that pattern and light intensity changes are possible at the level of the entire image, pixel blocks, or individual pixels.

[0099] Figure 4D is a schematic example of the implementation of a switchyard concept for additive manufacturing, with each image showing details of two mask patterning steps and beam redirection that are only accessible to half of the energy directing unit. In this example, one image is only accessible to beam directing units 471, 462, 472, 466, and the second image is accessible to beam directing units 470, 473, 455, 474. In operation, a non-patterning infrared beam 430 in the S polarization state is incident on an energy patterning unit 432 that is addressed from a projector via a beam 434 by a patterned ultraviolet image 433 (here, a representation of the number "9" in an 8×12 pixel format). Whenever UV light is incident on the energy patterning unit, the polarization state of beam 431 containing image information 433 is maintained. Upon incidence of 430 through a polarization element, the energy patterning unit 432 splits the beam and directs an image 446 in the p polarization state along a beam 435 towards an energy switching unit 447 (as denoted by X0 in FIG. 3C, for example). Image 437 in the s polarization state is then sent along a beam 436 towards a second energy patterning unit 438 that is addressed by a UV beam 440 containing image information 439. The energy patterning unit 438 sends an image 442 in the p polarization state along a beam 441 towards an energy switching unit 449. Image 444 in the s polarization state from the energy patterning unit 438 is sent along a beam 443 towards a beam dump 445, where image 444 may be discarded or utilized.

[0100] The first image, illustrated as 446, is incident on the energy switching unit 447, which receives the beam 435 that contains the image information 446 and is in the p-polarized state, and in this example, without changing the beam, passes it on as the beam 457 that still contains the image information 446, maintains the p-polarized state, and then is incident on the energy switching unit 458. The energy switching unit 458 receives the beam 457 that contains the image information 446 and, in this example, converts it to the s-polarized state, still contains the image information 446, and then passes it on as the beam 463 that is incident on the energy switching unit 464. The energy switching unit 464 receives the beam 463 that contains the image information 446 and, in this example, maintains the s-polarized state, still contains the image information 446, and then passes it on as the beam 465 that is incident on the energy directing unit 466. The energy directing unit 466, which can be a mechanical (rotary) galvanometer or other solid state device or rotary device, then directs the beam 465 towards the desired tile position on the print bed within its movable range.

[0101] The second image, illustrated as 442, is incident on the energy switching unit 449, which receives the beam 441 containing the image information 442 and in the p-polarized state, and in this example, without changing the beam, still maintains the p-polarized state while containing the image information 442, and then passes it through to the beam 450 incident on the energy switching unit 451. The energy switching unit 451 receives the beam 450 containing the image information 442, and in this example, maintains the p-polarized state and still contains the image information 442, and then passes it through to the beam 467 incident on the energy switching unit 468. The energy switching unit 468 receives the beam 467 containing the image information 442, and in this example, maintains the p-polarized state, still contains the image information 442 and then passes it through to the beam 469 incident on the energy directing unit 470. The energy directing unit 470, which can be a mechanical (rotary) galvanometer or other solid state device or rotary device, then directs the beam 469 towards the desired tile position on the printing bed within its movable range. In this example, an image relay as at least described in the disclosure regarding FIGS. 3D and 5A through 5C occurs between the beam 435 / 441 and the energy directing unit. Lenses, mirrors and other pre-optics, post-optics, intermediate optics are not depicted in this FIG. 4D but can be utilized as needed.

[0102] Figure 4E is a schematic example of the implementation of the switchyard concept, showing the details of two steps of the light valve patterning and beam redirection, where switching is described to access the entire energy steering unit. In this example, one image is accessible to the beam steering units 471, 462, 472, 466, 470, 473, 455, and 474. The non-patterning infrared beam 430 in the s polarization state is addressed from the projector via the beam 434 by the patterned ultraviolet image 433 (here, the representation of the digit "9" in an 8×12 pixel format) to the energy patterning unit 432 (such as described as 316 in Figure 3B). Whenever UV light is incident on the energy patterning unit, the polarization state of the beam 431 containing the image information 430 is maintained. Upon incidence on 430, the energy patterning unit 432 splits the beam and directs the image 446 in the p polarization state along the beam 435 towards the energy switching unit 447 (as marked at X0 in Figure 3C, for example). The image 437 in the s polarization state is then sent along the beam 436 towards the second energy patterning unit 438 addressed by the UV beam 440 containing the image information 439. The energy patterning unit 438 sends the image 442 in the p polarization state along the beam 441 towards the energy switching unit 449. The image 444 in the s polarization state from the energy patterning unit 438 is sent along the beam 443 towards the beam dump 445, where the image 444 is either discarded or utilized.

[0103] The first image 446 is incident on an energy switching unit 447, which receives a beam 435 containing the image information 446 and in a p-polarized state, and in this example modifies the polarization state to an s-polarized state, thereby causing switching to a beam 448 that still contains the image information 446 and is then incident on an energy switching unit 449. The energy switching unit 449 receives the beam 448 containing the image information 446 and, in this example, without changing the beam, maintains the s-polarized state and still contains the image information 446 and then passes it through to a beam 450 that is incident on an energy switching unit 451 (this process is detailed by the interaction of beam X1 and polarizer 382 to beam 317 in FIG. 3C). The energy switching unit 451 receives the beam 450 containing the image information 446 and, in this example, passes the beam through to a beam 452 that maintains the s-polarized state and still contains the image information 446 and is then incident on an energy switching unit 453. The energy switching unit 453 receives the beam 452 containing the image information 446 and, in this example, passes the beam through to a beam 454 that maintains the p-polarized state and still contains the image information 446 and is then incident on an energy directing unit 455. The energy directing unit 455, which can be a mechanical (rotary) galvanometer or other solid state device or rotary device, then directs the beam 454 towards the desired tile position on the print bed within its movable range.

[0104] The second image, illustrated as 442, is incident on the energy switching unit 449. The energy switching unit 449 receives the beam 441 that contains the image information 442 and is in the p-polarized state, and in this example, modifies the polarization state to the s-polarized state, thereby causing switching to the beam 456 that still contains the image information 442 and then is incident on the energy switching unit 447. The energy switching unit 447 receives the beam 456 that contains the image information 442, and in this example, without changing the beam, maintains the s-polarized state and still contains the image information 442 and then passes it through to the beam 457 that is incident on the energy switching unit 458 (this process is detailed by the interaction of the beam X1 and the polarizer 382 to the beam 317 in FIG. 3C). The energy switching unit 458 receives the beam 457 that contains the image information 442, and in this example, modifies the beam to the p-polarized state and still contains the image information 442 and then passes it through to the beam 459 that is incident on the energy switching unit 460. The energy switching unit 460 receives the beam 459 that contains the image information 442, and in this example, modifies the beam to the S-polarized state and still contains the image information 446 and then passes it through to the beam 461 that is incident on the energy directing unit 462. The energy directing unit 462, which can be a mechanical (rotary) galvanometer or other solid-state device or rotary device, then directs the beam 461 towards the desired tile position on the print bed within its movable range. In this example, an image relay, at least as described in the disclosure regarding FIGS. 3D and 5A - 5C, occurs between the beam 435 / 441 and the energy directing unit. Lenses, mirrors, and other pre-optics, post-optics, intermediate optics are not depicted in this FIG. 4E but can be utilized as needed.

[0105] FIG. 5A is a diagram 500 illustrating area printing of a plurality of tiles using a print bar concept. The print bar 506 can include a galvanometer mirror set or a solid state system that does not necessarily require a movable mirror. The plurality of input patterns 503 are redirected by the plurality of image relays 504 to the print bar 506 that has an integrated image pipe and solid state array of optics. The print bar 506 can be moved while selectively irradiating one or more tiles 512 across the powder bed 510 along a single axis as illustrated. In other embodiments using a larger powder bed, the print bar can be moved along both the X and Y axes to handle the powder bed 510. In some embodiments, the optics associated with the print bar can be fixed to enable a single tile size, while in other embodiments, a movable optic can be utilized to expand or contract the tile size, or to compensate for movement of the print bar along the z-axis. In other embodiments, a patterned image, including but not limited to the energy patterning binary tree system as described in FIG. 4A, can be created using a recycled light pattern. In some embodiments, a plurality of tiles can be printed simultaneously within a given time period. Alternatively, if full utilization is not possible due to available patterned energy, heat issues, or other print bar configuration issues, a subset of tiles can be printed at different times.

[0106] Figure 5B is Figure 501 illustrating area printing of a plurality of tiles using an overhead fixed array that includes a plurality of beam steering units. The beam steering unit as the defined unit cell of 508 can include a movable mirror (galvanometer) or an alternative solid state beam steering system. A plurality of input patterns 503 are redirected by a plurality of image relays 504 to a matrix 508 that integrally includes an array of optical systems. The matrix 508 is sized to be coextensive with the powder and need not be moved across the powder bed 510. This substantially reduces errors associated with movement of the print bar and simplifies system assembly and operation. In some embodiments, the optical system that interfaces with the matrix can be fixed to enable a single tile size, and in other embodiments, a movable optical system can be utilized to expand or contract the tile size or to compensate for movement along the z-axis of the matrix 508. Patterned images, including, without limitation, an energy patterning binary tree system as described in FIGS. 4A, 4D, or 4E, as in the embodiment described in FIG. 5A, can be created using recycled light patterns. In some embodiments, a plurality of tiles can be printed simultaneously during a given time period. Alternatively, if full utilization is not possible due to available patterned energy, heat issues, or other matrix configuration issues, a subset of tiles can be printed at different times.

[0107] Figure 5C is FIG. 502 illustrating area printing of a plurality of tiles using an alternative hierarchical system. A plurality of input patterns 503 are redirected by a plurality of image relays 504 to individual beam steering units 510, which in turn direct the patterned image to a matrix 508 that integrally includes a plurality of optical systems and beam steering units. The matrix 508 is sized to be coextensive with the powder and need not be moved across the powder bed 510. Similar to the embodiments described in connection with FIG. 5A, a patterned image, including without limitation an energy patterning binary tree system as described in FIG. 4A, can be created using a recycled light pattern. In certain embodiments, a plurality of tiles can be printed simultaneously during a given time period. Alternatively, if full utilization is not possible due to available patterned energy, heat issues, or other matrix configuration issues, a subset of tiles can be printed at different times.

[0108] Referring to FIGS. 6A - 6D, in the method described above, a high - flux beam energy (e.g., beam 307) is an image patterned in a two - dimensional pattern, which is then transferred to a powder bed where the pattern is transferred to a pool of molten metal on the powder bed with a spatial positive correlation to the two - dimensional pattern. As described above, the two - dimensional pattern can be a grayscale pattern. The methods described below in connection with FIGS. 6A - 6C use a two - dimensional grayscale pattern to achieve desirable material characteristics rather than simply selecting which areas of the powder to melt. In particular, local control of the spatial temperature gradient and heat flux can be achieved by the selection of the two - dimensional grayscale pattern. The methods below in connection with FIGS. 6A - 6C can also be implemented while adjusting the duty cycle (on - period and off - period durations) for each pixel of the two - dimensional pattern using binary intensity levels (e.g., 0% and 100% intensity).

[0109] FIG. 6A illustrates a method 600a for grayscale area printing for additive manufacturing (AM). In a first example 602, an amplitude-based method may be used to perform area printing in AM. In a second example, a phase-based method 604 may be used to perform area printing in AM. Examples of amplitude-based and phase-based methods using a two-dimensional grayscale pattern were described above with respect to FIG. 3A.

[0110] In both the amplitude-based method and the phase-based method, an unpatterned high-flux light (HFL) beam 606 (such as a laser beam, for example) is generated. The HFL beam 606 may include light from a plurality of different light sources that are mixed and combined to form a single beam. The HFL beam 606 passes through a patterning device 608, which modifies some optical properties of the HFL and impresses the desired two-dimensional grayscale image to be printed on the powder bed onto this property. In some implementations, the patterning device 608 may include another optical element that separates the desired pattern from the unwanted waste (beam) and sends the desired pattern to the bed, while the unwanted pattern proceeds to a switching system for recycling or to a beam dump.

[0111] The patterning device 608 may include one or more optically addressable light valves (OALVs). For example, the patterning device 608 may include one or more OALVs each implemented according to any of the methods described above to implement the light valve 380 described above in connection with FIG. 3A. The OALVs may be used to print an image of the light valve (a “tile”) onto a layer of metal powder on the powder bed. The flux of the HFL beam 606 at the OALV is limited by the laser-induced damage threshold (LiDT) of the OALV. In another embodiment, the patterning device 608 is patterned by an electron beam as described above in connection with FIG. 3B.

[0112] In the first example, the patterning device 608 includes a first OALV 610 illuminated by the HFL beam 606 and a second OALV 612 illuminated by a diode laser (DL) beam 614 from one or more diode lasers (DLs). The DL beam 614 and the HFL beam 606 can have different wavelengths. For example, the DL beam can have a longer wavelength than the HFL beam 606. The HFL beam 606 can also have a much shorter pulse duration compared to the pulse length of the DL beam 614, because this can damage the high peak flux OALV 610 of the HFL beam 606. To obtain the patterned HFL beam 606 and the patterned DL beam 616b, the OALVs 610, 612 each impart a pattern to the HFL beam 606 and the DL beam. The patterned beams 616a and 616b are directed at the printing plane 618. The patterns added to the beams 606 and 614 can be the same or different.

[0113] At the printing plane 618, the patterned DL beam 616a raises the temperature of the metal powder to just below the melting point, and the shorter pulses of the patterned HFL beam 616b cause the powder regions (“tiles”) to melt with the patterning imparted to the HFL beam 606 by the OALV 610 valve. The maximum size of the tiles to be printed depends on the laser flux that the OALV can withstand without laser damage. When the light from the patterned beams 616a and 616b overlaps, the flux rises above the threshold for powder melting.

[0114] The patterned beams 616a and 616b can be directed to the printing plane 618 by one or more galvo / turning mirrors 620, and the one or more galvo / turning mirrors 620 direct the patterned beams 616a and 616b to various regions of the printing plane 618, where the beams 616a and 616b melt the powder to generate a printed pattern 622 corresponding to the pattern of the patterned beams 616a and 616b. The beams 616a and 616b can pass through one or more optical components before entering the one or more galvo / turning mirrors 620. Other beam directing modalities, such as liquid crystals, can also be used.

[0115] In a second example 624, phase-based grayscale generation is performed using multiple beams having a certain degree of coherence across the tile size in the printing plane 618. The coherence can be used to generate a two-dimensional pattern such that, in some embodiments, the HFL beam has a certain degree of coherence in the printing plane 618. In contrast, the DL beam heats the powder but does not melt it, and may not be patterned in the printing plane 618 and may have no coherence.

[0116] In a phase-based grayscale, the high-flux beam 606 enters the patterning unit 608, which generates a patterned beam 616a that is later separated into several beamlets 626 that travel along different optical paths. Phase patterning can be added to the high-flux beam 606 before separation, or can be added individually to each beamlet 626 by different regions of a separate OALV or the same OALV. In some embodiments, higher coherence and improved modulation are obtained when patterning is added to the high-flux beam 616 before separation. The beamlets 626 can be arranged using an optical system so as to finally combine at the printing plane 618. The optical system can include optical paths for each beamlet 616 and can also include compensating optics to adjust the phase delay of each optical path to obtain an improved dynamic range at the printing bed. The beamlets 626 can then be reflected from the galvo / folding mirror 620 before combining and overlapping 628 at the printing plane 618. Interference between the beamlets 626 creates a two-dimensional intensity pattern that dissolves into a two-dimensional printed pattern 622 at the build plane.

[0117] The patterning unit 608 can be implemented as a phase interference device for adding a grayscale pattern as described in U.S. Application Serial No. 17 / 670,149.

[0118] Figure 6B illustrates an example 600b of controlling the Young's modulus of a printed portion using grayscale printing. In these examples, the printing plane 618 includes, as an example, a layer 630 and a volume 632 shown separated from the layer 630 and beneath the print. This volume 632 consists of the current printing layer 630a and one or more previous printing layers 630b and 630c. The volume 632 includes a structural material that is printed using grayscale printing to create its lattice structure and modify particle features within the lattice structure.

[0119] By using the printing area method described herein, each printing tile may consist of millions of pixels. Here, "pixel" is used to refer to a controlled individual area of a melt pool associated with a specific two-dimensional pattern of HFL beams incident towards the elements of a two-dimensional image. The intensity of the flux received by each pixel can be controlled across the grayscale dynamic range using any of the methods described above. For example, adjacent pixels may have different grayscale values. In an example where the pixels are different, the grayscale values are also different, and there are multiple different flux levels in the melt pool. Thereby, the temperature gradient goes from pixels of higher flux (higher temperature as more energy is transferred) to pixels of lower flux (vice versa).

[0120] With a timely global switch for the HFL pulses of the HFL beam and the heating pulses of the DL beam, the heat flux can be stabilized in the direction from high flux to low flux. The particle structure that begins to form after the HFL pulse ends is in this same direction, and thus the particle structure follows the heat flux from high flux to low flux. For example, the particle structure can be affected by both the temperature to which a metal structure is heated towards its temperature and the cooling time. In various examples, the particle size increases with the temperature rise. In other examples, the particle structure increases as the cooling time lengthens. Thus, the particle structure can be affected by the temperature to which the melt pool is heated and / or the cooling cycle. The temperature profile applied to each pixel of the melt pool also has an impact on the microstructure of the particles themselves. For example, the type(s) of crystal within each particle, and the mixture of various crystal types within each particle. For example, in the case of steel, the crystals grow in the form of martensite dendrites and austenite. Thus, the temperature profile can control the formation of martensite and austenite within each particle.

[0121] The relationship between the particle size and the microstructure of the particles regarding the temperature profile controlled at the level of each pixel can be obtained using the methods described in the following references, which are hereby incorporated by reference in their entirety. Ryan R, Dehoff, “Electron Beam Melting Technology Improvements,” Oak Ridge National Laboratory (January 2019) Jorge Mireles et al., ”Closed Loop Automatic Feedback Control in Electron Beam Melting,” Int. J. Adv. Manuf. Technol. 78:1193 - 1199 (2015) Timothy Horn, ”material Development for Electron Beam Melting,” Center for Additive Manufacturing and Logistics, NC State University (2015) T. Mahale et al., ”Advances in Electron Beam Melting of Aluminum Alloys,” 2007 International Solid Freeform Fabrication Symposium Tomas Kellner, “This Electron Gun Builds Jet Engines,” General Electric, (August 18, 2014) Sciaky Inc., “Sciaky to Deliver Industry - Leading Electron Beam additive manufacturing system to EWI, Sciaky Inc. (July 20, 2016)

[0122] Material properties such as stiffness have a direct correlation to this particle growth and the resulting microstructure. Stiffness can be controlled by controlling the thermal gradient to control the direction in which the particles can grow and / or the local chemical properties of each particle such as solute elements at the walls of each particle that can affect the Young's modulus. For example, stiffness can increase with an increase in particle size. Thus, stiffness is higher in regions with a particle size larger than average and lower in regions with a particle size lower than average. Thus, the stiffness of an object created using the additive manufacturing process described above can be controlled on a pixel-by-pixel basis depending on the flux received by each pixel and the temperature by which each pixel is heated.

[0123] In other examples, along with the particle size, the lattice structure of the material being cooled can be controlled based on the thermal gradient. For example, it is possible to control the level of epitaxial growth and affect the overall structure of the material by controlling the thermal gradient of adjacent or nearby pixels and / or cooling the pixels.

[0124] The particle structure between layers can be controlled by grayscale printing performed with temporal flux control of the beam such that cooling occurs from the bottom upwards with columnar grain growth to follow the degree of cooling. The particle growth in this direction can be associated with a characteristic dimension. For example, acoustic resonance can occur in the plane of layer 630 where acoustic resonance can occur in all three dimensions. There may be cases where the acoustic resonance in the direction from layer to layer is different from the acoustic resonance in the plane of print layer 630 for better control in the plane of print layer 630.

[0125] In one example, one or more low-temperature pixels that are still above the sintering point will have a first rigidity, one or more moderately heated pixels that are above the melting point will have a second rigidity, and one or more pixels with the highest temperature will have a third rigidity. For regions within a tile that exhibit a thermal gradient (due to the differences in flux described above), the coefficients will vary between levels. Although the coefficients are described as having "levels", it should be noted that this does not necessarily refer to distinct changes, but rather the variations are continuous.

[0126] Both the particle structure and the lattice structure can affect the thermal and acoustic properties of the cooled and finished part, and both the thermal and acoustic properties can be independently adjusted, at least in part, depending on the structures created and whether these structures resonate with the sound field. As shown in FIG. 634 of volume 632 in the normal direction 636 with respect to the printing plane 618, volume 632 can include one or more types of lattices. For example, two or more types of lattices with a first periodicity 638 and a second periodicity 640 that are orthogonal to each other can be discerned. The width of each lattice feature in two dimensions (e.g., dimensions "X" and "Y") orthogonal to each other in the printing plane 618 can resonate at a specific acoustic frequency.

[0127] The acoustic properties can be formed according to a grayscale. For example, a grayscale along "X" and intersecting "Y" can have a periodicity corresponding to the desired lattice spacings 638, 640. The spacing at the lattice openings can also resonate at the same or different frequencies. In one embodiment, the acoustic resonance is a macroscopic result of the variation of the Young's modulus within and between tiles, as shown in FIG. 634. When viewed parallel to a plane along direction 642, the printed volume 632 may show the direction of particle growth occurring between layers, such as two or more lattice types with a second periodicity (e.g., in the X or Y direction) and a third periodicity 646 (e.g., in the Z direction) as shown in FIG. 644.

[0128] In another embodiment, heat may be conducted in a specific way to adjust thermal control by controlling the Young's modulus and the large cross-sectional area of the desired path. By increasing the density of components within a layer from another layer or from any lateral volume into a lateral volume, a heat path may be established within the component, thereby enabling the user to design and assemble a heat circuit for enhancing cooling in the finished component. For example, referring to a normal (e.g., top to bottom) view of the printed layer 630, the first layer 630b may have a first density and the second layer 630c may have a second density. For example, the first layer 630b may have a lower density and the second layer 630c may have a higher layer, or vice versa. In the example illustrated in FIG. 1B, the increase in density is depicted as an increase in density from layer to layer, while in other exemplary implementations, the increase in density may be in-plane or may be connected in any desired volume shape. With the grayscale printing technology described herein, heat paths may be created within the tile, in-plane, or across the layers for generating these volumes. The density may be further controlled to adjust the porosity such that heat pipes may be formed within the material along the X, Y, or Z directions or in paths that are not orthogonal to these directions, i.e., that curve.

[0129] FIG. 6C illustrates an example 600c of macroscopically aligned crystallography using grayscale printing. The build plane 618 has a print target volume 640 that includes a volume 642 detailed in FIG. 6C. The volume 642 may represent one or more tile positions or a portion of one tile position in a plane parallel to the build plane 618. Each tile may include millions of image pixels. Each image pixel has an independent flux value within the range of flux values added by the OALV in any of the manners listed above.

[0130] The top surface of the currently printed volume 640 is on top of the previously printed layer. Most of these layers consist of crystal structures 644 with a similar orientation, and other portions exhibit different crystal structures 646, 648, such as polycrystalline structures. The structures 644, 646, 648 can exist across multiple layers of the volume 640, and can have the same shape in each layer, or different shapes between layers, having a curved outer shape or other shaped outer shapes, and can form structures 644, 646, 648 having a boundary line that is not orthogonal to the build plane 618.

[0131] The crystal structures 644, 646, 648 can be formed layer by layer using grayscale printing across the tiles forming the structures 644, 646, 648. Each grayscale level in the printed image represents various fluxes corresponding to the powder / its pixels and also represents the various temperatures reached by the melt pool. If there are different grayscale levels in the image across the tiles, there can be a temperature gradient from a higher flux melt pool to a lower flux melt pool (representing a higher temperature gradient to a lower temperature gradient). As the HFL flux weakens, these melt pools begin to crystallize according to the time pulse function of the HFL associated with the thermal gradient and the formation of polycrystals of the material. Short or long particle structures are formed along these gradients that depend on these factors (the characteristics of the HFL beam, the gradient, and the crystal orientation). Various material properties are derived from both the crystal orientation and the particle type (short or long and orientation), and the particle type includes yield strength, plasticity, creep, fatigue, elongation, thermal conduction and acoustic conduction, acoustic response and acoustic resonance, the reaction of the glass (ability to self-heal or stop crack propagation), and fracture strength.

[0132] In addition to the structures 644, 646, 648 that exist across multiple layers, one or more layers 652 can be created within the volume 640 using a crystal structure different from that of the layer 650, either above or below the one or more layers 652. This can be useful in relieving stress in the volume, planned delamination, stopping crack propagation in the volume, or achieving similar control of the face during sharper edges or microflaking. Additionally, these unique features / defects can be used to integrate desirable thermal paths or other controlled phononic features within the volume 640.

[0133] These features / defects can be phononic resonators that can enhance, control, or eliminate local or global acoustic resonances or thermoionic resonances for better operational performance and can also give rise to new mechanical capabilities. There is a large body of knowledge in using "phononic crystals" that can be used to create, manipulate, control, increase, and eliminate phonons with varying frequencies and time - space bandwidth products, enabling the integration of existing and new applications into additive - manufactured parts. For example, if appropriate parts are made with various phononic resonators scattered (by design) within a volume, an external stimulus applied to a specific point on the outer surface of the finished part can cause a series of acoustic resonances. By varying the location and nature of the stimulus, other resonances leading to other desirable behaviors can be induced.

[0134] Figure 6D illustrates an example 600d of the temporal structuring of grayscale printing in the control of material characteristics. The build plane 618 has a print target volume 660 being printed, with the current print layer 662 of the print target volume 660 shown as being in the process of being printed. The current layer 662 is shown in detail as a shape 664 formed from a matrix of tiles 666, each of the tiles 666 containing an array of print target pixels. Each tile 668 of each of the tiles 666 is shown as an array of individual pixels 670. The magnitude (grayscale value) and duration of the flux can be controlled for each pixel 670 of each tile 668. The magnitude and duration of the flux can be selected to control the characteristics at each pixel location when printed as the current layer 662 within each layer corresponding to each pixel 670. The number of pixels shown is for example, and more or fewer pixels can be used depending on the resolution of the optical components being used.

[0135] As shown in FIG. 6D, a tile 668 can include regions of pixels 670 having different material properties (illustrated by the gray and white sections). A pixel matrix 672 shows exemplary timings 674 for each pixel 670 of a portion of the tile 668. For each pixel 670, a value t n having n = 0, 1, 2, or 3 (or any other number) depending on which region that pixel occupies is shown for the timing 674. The time variable t n can define some or all of the pulse duration, the interval between pulses, and the pattern of the pulses for each pixel 670. Some or all of the pulse duration, the interval between pulses, and the pattern of the pulses can be defined for one or both of the HFL beam and the DL beam.

[0136] For example, FIG. 6D shows a timing diagram 674 of the pulse pattern of pixel 670 where the horizontal axis is time and the vertical axis is the intensity or amplitude of the flux. Higher (higher intensity) bars may correspond to the flux of the HFL beam, and lower (lower intensity) bars may correspond to the DL beam. In the first pattern 676, the DL beam has a single pulse with a first pulse period, and the HFL beam has a plurality of second pulses with a second period during which all of them occur during the first period of the HFL beam. The second pulses may be separated by periods of zero flux. The second pulses may be of equal or unequal duration, and the periods of zero flux between the second pulses may be of equal or unequal duration. As shown, the first pulse may start before the first second pulse and may continue after the last second pulse of pattern 676. The duration of the first pulse before the first second pulse and the duration of the first pulse after the last second pulse may be equal or unequal.

[0137] In one example, pattern 676 represents a baseline pattern corresponding to t0. Patterns corresponding to t1, t2, t3, or other timing values may be configured in various ways. In the first example, the patterns corresponding to t1, t2, t3 respectively correspond to the number of repetitions of pattern 676. For example, pattern 678 includes pulses 680, 682, 684 that may each represent a second pulse of the HFL beam or an example of pattern 676. In any case, pulses 680, 682, 684 may occur within the period of the first single pulse of the DL beam. In one example, pulse 680 corresponds to t1, pulse 682 corresponds to t2, and pulse 684 corresponds to t3.

[0138] In the second example, the periods of zero HFL beam intensity preceding and / or following pattern 676 are different for each of the patterns t1, t2, t3. In the third example, the patterns corresponding to t1, t2, t3 include a second pulse having a different intensity and / or period from the second pulse of the baseline pattern 676. The variables of pulse period, pulse intensity, the period of zero intensity between pulses, and the periods of zero intensity before and after the second pulse define a design space from which a pattern can be defined to achieve the desired material properties for a given pixel. In particular, the period of zero HFL intensity may allow for cooling during or after the execution of pattern 676. The first pulse is shown as being constant in intensity, but may have an intensity that varies over time across pattern 676 achieved using the techniques described herein for creating a grayscale patterned beam.

[0139] In the illustrated example, using the timing sequences t0, t1, t2, t3 of matrix 672 results in various regions 686a - 686d of pixels within tile 668, each of those regions creating various material features at the corresponding pixel locations in the current print layer 662. For example, the first region 686a receives flux pattern t0, region 686b receives flux pattern t1, region 686c receives flux pattern t3, and region 686d receives flux pattern t0. In regions 686a, 686d, the material features may correspond to the grayscale intensity levels of a second pulse that is modified relatively little for control of the cooling rate. In contrast, regions 686b, 686c may have different material properties due to different patterns that provide modification by the cooling rate determined by the period of zero HFL beam flux during which the second pulse and cooling occur.

[0140] The period of the first pulse, the second pulse, and the zero-intensity periods between the pulses can have a minimum period determined by the switching period of the OALVs used to pattern the HFL beam and the DL beam. Similarly, the increment by which the period of the pulse can be changed can be a function of the switching period of the OALVs being used. For example, the OALV can have a switching period from 10 ms to 50 ms.

[0141] FIG. 7 illustrates an exemplary use of the grayscale additive manufacturing described herein. The component 700 can include a protrusion 702 having a distal end 704 that is closer to the printing plane 618 than a proximal end 706 of the protrusion 702 is attached to the remainder of the component 700. Since layers closer to the printing plane 618 are printed before layers farther from the printing plane 618, the distal end 704 is printed before the proximal end 706. Thus, a support 708 can be printed and exist between the printing plane 618 and the distal end 704 to maintain the distal end 704 in place while the next layer of the distal end 704 is being printed. The support 708 is not part of the component 700 and should thus be removed. In some embodiments, grayscale printing is used such that the support 708 has different material properties than the component 700. For example, the support 708 can be made more brittle, softer, and / or more porous than the material forming the component 700.

[0142] FIG. 8 illustrates another exemplary use of the grayscale additive manufacturing described herein. FIG. 8 illustrates a portion of the pixels of a part in a plane parallel to or orthogonal to the printing plane 618. The blank pixels represent non-print target pixels such that the area of the powder located within the tile projected during printing remains undissolved. The pixels marked "A" correspond to the edges of the part to be printed at the boundary between the non-print target pixels and the print target pixels. The pixels marked "B" correspond to the interior of the part that forms a boundary with the non-print target pixels. Since the non-print target pixels are not melted, the rate of heat flow exiting the A pixels is different from that of the B pixels. To compensate for this, the intensity and / or duration of the flux applied at each pixel position of the tile can be adjusted by using a grayscale pattern. For example, the A pixels can receive a flux of higher intensity and / or a longer duration of flux from the HFL beam compared to the B pixels. In addition to this, the non-print target pixels can still be illuminated by the DL beam to reduce the rate of heat flow from the A pixels. The illustrated pixels can represent pixels in a plane parallel to or orthogonal to the printing plane 618.

[0143] Referring to FIG. 9, in a more general case, each pixel 900 can be understood as the central pixel in a 3×3×3 array 902 that includes the pixel 900 and all surrounding pixels. Tests, modeling, or a combination of the two can be performed for a wide range of arrangements of the 3×3×3 array of pixels 902. In particular, modeling and / or testing can be performed for different arrangements of printable and non-printable pixels per pixel, different values of various material properties (Young's modulus, porosity, hardness, strength, particle size, microcrystalline structure, etc.), and various gradients in which the material properties vary across the 3×3×3 array of pixels 902 accordingly. Modeling and / or testing can be performed to determine the two-dimensional grayscale pattern and / or timing pattern that can be applied to each layer of the 3×3×3 array of pixels 902 to achieve any of the above arrangements. Since all pixels other than the central pixel 900 will be adjacent to other pixels, if the properties of the pixel 900 and the surrounding pixels are defined by the arrangement, the grayscale intensity value and / or timing pattern of the pixel 900 can be determined by modeling and testing. Other array sizes, such as 5×5×5, 7×7×7, or N×M×P where N, M, and P are integers greater than 3 and can be the same or different, can be modeled and / or tested.

[0144] Hereinafter, for any component and the desired properties for each pixel of that component, the grayscale flux value and / or timing pattern per pixel can be selected based on the desired material properties (printable / non-printable, Young's modulus, porosity, hardness, strength, particle size, microcrystalline structure, etc.) and the desired material properties of adjacent pixels. In particular, a matching array 902 can be identified, and the grayscale flux value and / or timing pattern can be selected for each pixel of the component based on the grayscale flux and / or timing pattern of the central pixel 900 of the matching array 902.

[0145] In some situations, there may not be an array that exactly matches. To address this, various techniques can be used, such as rotating the matrix 902 to fit the contour and / or gradient of the component. In some embodiments, curve fitting, machine learning, or other techniques can be used to associate the material properties of the matrix 902 with the grayscale flux value and / or timing pattern of the central pixel 900. When machine learning is used, a neural network, convolutional neural network (CNN), deep neural network (DNN), or other type of machine learning model can be trained with data entries each containing a matrix 902 of one or more material properties (printable / non-printable, Young's modulus, porosity, hardness, strength, particle size, etc.) with respect to each pixel of the 3D array and the grayscale flux value and / or timing pattern of the central pixel 900 (or other pixel position) of the 3D array as the desired output. Each training data entry can be processed using a machine learning model to obtain an estimated value. The estimated value can be compared with the desired output of the training data entry. The parameters of the machine learning model can be adjusted according to a loss function corresponding to the difference between the estimated value and the desired output. The machine learning model can then be utilized by inputting a 3D array of the desired properties to obtain the grayscale flux value and / or timing pattern for one or more pixels (e.g., the central pixel) of the 3D array.

[0146] Those of ordinary skill in the art having the benefit of the techniques presented in the foregoing description and the associated drawings will appreciate many modifications and other embodiments of the invention. It is therefore understood that the invention is not to be limited to the specific embodiments disclosed and that modifications and embodiments are intended to be included within the scope of the appended claims. It is also understood that other embodiments of this invention may be practiced excluding elements / steps not specifically disclosed herein.

Claims

1. A method comprising: accumulating a layer of powder on a printing plane; writing a two-dimensional grayscale pattern on a light valve; radiating a first light beam from a light source onto the light valve to obtain a patterned beam having a two-dimensional flux pattern corresponding to the two-dimensional grayscale pattern; and directing the patterned beam onto an area of the layer of powder to obtain a dissolved portion, the dissolved portion having material properties that vary two-dimensionally corresponding to the two-dimensional grayscale pattern, the directing.

2. The method according to claim 1, wherein the two-dimensional grayscale pattern has at least three intensity levels.

3. The method according to claim 1, wherein the two-dimensional grayscale pattern has at least three intensity levels selected from a range of at least 128 levels.

4. The method according to claim 1, wherein to obtain the patterned beam, the light valve modulates the amplitude of the first light beam.

5. The method according to claim 1, wherein to obtain the patterned beam, the light valve modulates the phase of the first light beam.

6. The method according to claim 1, wherein to obtain the patterned beam, the light valve modulates the coherence of the first light beam.

7. The method according to claim 1, wherein the light source is a first light source, the light valve is a first light valve, the two-dimensional grayscale pattern is a first two-dimensional grayscale pattern, the patterned beam is a first patterned beam, and the method further comprises: writing a second two-dimensional grayscale pattern on a second light valve; radiating a low-flux beam onto the second light valve to obtain a low-flux patterned beam, the low-flux beam being insufficient to dissolve the layer of powder and having a lower flux than the first patterned beam; and directing the low-flux patterned beam onto the area simultaneously with directing the first patterned beam onto the area.

8. The method according to claim 7, wherein The method wherein the first patterned beam includes one or more first pulses, the low flux beam includes one or more second pulses, and the one or more second pulses are longer than the one or more first pulses. **Claim 9** The method according to claim 1, wherein the material property includes Young's modulus. **Claim 10** The method according to claim 1, wherein the material property includes porosity. **Claim 11** The method according to claim 1, wherein the material property includes particle size. **Claim 12** The method according to claim 1, wherein the material property includes crystal microstructure. **Claim 13** A system comprising: a powder delivery system configured to deposit a layer of powder on a build plane; a light valve; a patterning unit configured to write a series of two-dimensional grayscale patterns to the light valve; a light source configured to emit a first light beam onto the light valve such that the light valve outputs a patterned beam corresponding to each two-dimensional grayscale pattern of the series of two-dimensional grayscale patterns; a beam director configured to direct the patterned beam to a plurality of regions of the build plane to selectively melt portions of the layer of powder according to the series of two-dimensional grayscale patterns; and a controller connected to the light source, the patterning unit, and the beam director and configured to generate the series of two-dimensional grayscale patterns to achieve a material property that varies two-dimensionally within the portion. **Claim 14** The system according to claim 13, wherein the controller is further configured to generate the series of two-dimensional grayscale patterns to apply a pattern of pulses to each of the plurality of regions. **Claim 15** The system according to claim 14, wherein the series of two-dimensional grayscale patterns defines an array of pixel positions and the controller is configured to independently control the pattern of pulses for each pixel position of the array of pixel positions. **Claim 16** The system according to claim 13, The light source is a first light source, the light valve is a first light valve, the first light beam is a first first light beam, the patterned beam is a first patterned beam, and the series of two-dimensional grayscale patterns is a series of first two-dimensional grayscale patterns. The system further a second light valve, and a second light source configured to emit a second first light beam onto the second light valve, the second light source having a flux insufficient to melt the layer of powder lower than that of the first light source, the second light source; comprising The patterning unit is configured to write a series of second two-dimensional grayscale patterns to the second light valve such that the second light valve outputs a second patterned beam corresponding to each second two-dimensional grayscale pattern in the series of second two-dimensional grayscale patterns, and the series of first two-dimensional grayscale patterns and the series of first two-dimensional grayscale patterns define an array of pixel positions, and the controller independently controls a first pattern of a first pulse in the first patterned beam for each pixel position in the array of pixel positions, and for each pixel position in the array of pixel positions, independently controls a second pattern of a second pulse in the second patterned beam. A system programmed to do so.

17. The system according to claim 16, wherein the first light source is a high-flux laser and the second light source is a diode laser.

18. The system according to claim 13, wherein the controller is configured to perform at least one pattern of the series of two-dimensional grayscale patterns including at least three intensity levels selected from a range of at least 128 levels.

19. The system according to claim 13, wherein the light valve is the amplitude of the first light beam to obtain the patterned beam, the phase of the first light beam to obtain the patterned beam, or the coherence of the first light beam to obtain the patterned beam, configured to modulate one of them.

20. The system according to claim 13, The system, wherein the material properties include one or more of Young's modulus, porosity, particle size, and crystal microstructure.

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