Powder Bed Measurement for Additive Manufacturing

Abstract

The print engine of the additive manufacturing system supporting the powder measurement system includes a print bed capable of holding powders of various sizes, a laser energy patterning system directable relative to the print bed, and a backscatter sensing system positioned to evaluate the scattered light distribution from the powder on the print bed to determine powder size.

Description

[Technical Field]

[0001] [Related Applications] This disclosure is part of a non-provisional patent application claiming the benefit of priority to U.S. Patent Application No. 63 / 387,607, filed December 15, 2022, which is incorporated herein by reference in its entirety.

[0002] [Technical field] FIELD OF THE DISCLOSURE The present disclosure relates generally to systems and methods for powder bed diagnostics in additive manufacturing. In some embodiments, particle size and particle distribution in a powder bed are provided using various backscatter measurements. [Background technology]

[0003] Traditional component fabrication often relies on the removal of material by drilling, cutting, or grinding to form a part. In contrast, additive manufacturing, also known as 3D printing, typically involves the sequential layer-by-layer addition of material to build a part. Starting with a 3D computer model, additive manufacturing systems can be used to create complex parts from a variety of materials.

[0004] One additive manufacturing technique, known as powder bed fusion additive manufacturing (PBF-AM), uses one or more focused energy sources to print a pattern into a thin layer of powder by melting the powder and bonding it to the layer below, gradually forming a 3D printed part. The powder can be plastic, metal, glass, ceramic, quartz, other fusible materials, or a combination of fusible and infusible materials (i.e., plastic and wood or metal and ceramic). The packing density of the powder prior to melting can play a significant role in the density of the final printed part. Pores, voids, and cracks (print defects) can occur due to low packing density or unwanted variations in powder spreading or distribution.

[0005] To reduce printing errors, systems and methods are needed to enable testing and diagnosis of powder properties, including particle size and particle distribution. Ideally, diagnostics of the powder layer before and during printing would be available to determine the quality of the powder size distribution, the thickness of the powder bed layer, and how the powder size distribution is distributed. This information can be used to adjust beam printing parameters and to predict and determine remelt post processing beam profiles for any printed layer. [Brief explanation of the drawings]

[0006] Non-limiting, non-exclusive embodiments of the present disclosure are described with reference to the following drawings, in which like reference numerals refer to like parts throughout the various views unless otherwise stated. [Figure 1] 1 illustrates an additive manufacturing system suitable for use in conjunction with the described diagnostic systems and methods. [Figure 2A] 1 illustrates one embodiment of a diagnostic and measurement technique that relies on backscatter measurements for powder size determination in a print bed. [Figure 2B] Illustrates an example of the use of backscatter and controlled coherence systems to determine powder size and powder depth. [Figure 2C] 1 illustrates an example of a volumetric printing system in additive manufacturing using adaptive optics technology with backscatter coherence analysis. [Figure 2D] 1 illustrates an example of a diagnostic imaging system for assessing real-time print quality using backscattered light from an off-axis source. [Figure 2E] FIG. 1 illustrates a block diagram of an exemplary additive manufacturing system suitable for processing and measuring characteristics of virgin or recycled powders. [Figure 3] 1 illustrates an additive manufacturing system capable of measuring characteristics of new or recycled powder and directing a one- or two-dimensional light beam to melt the powder and form structures. [Figure 4]Illustrates a method for the operation of an additive manufacturing system capable of measuring characteristics of new or recycled powder and directing a one- or two-dimensional light beam to melt the powder and form a structure. [Figure 5] 1 illustrates an additive manufacturing system that uses a switchyard system and is capable of directing a one- or two-dimensional light beam to measure characteristics of new or recycled powder and melt the powder to allow the formation of structures. DETAILED DESCRIPTION OF THE INVENTION

[0007] In the following description, reference is made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration specific exemplary embodiments in which the present disclosure may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the concepts disclosed herein, it being understood that modifications may be made to the various disclosed embodiments and other embodiments may be utilized without departing from the scope of the present disclosure. Accordingly, the following detailed description is not to be taken in a limiting sense.

[0008] FIG. 1 illustrates one embodiment of an additive manufacturing system 100 that uses multiple semiconductor laser devices as part of an energy patterning system 110. A control processor 150 or 152 may be connected to various sensors, actuators, heating or cooling systems, monitors, and controllers to coordinate the operation of the multiple laser devices 112, the light patterning unit 116, and the image relay (final imaging assembly) 120, as well as any other components of the system 100. As will be understood, connections may be wired or wireless, continuous or intermittent, and may have feedback capabilities (e.g., thermal heating may be adjusted in response to a sensed temperature). The multiple laser devices 112 may emit a beam of light 101. In one embodiment, a 1000 nm wavelength beam may be used. In an example, the beam may be 90 mm wide and 20 mm high. The beam 101 may be resized by imaging optics 170 to create beam 103. In an example, beam 103 may be 6 mm wide and 6 mm high and enters light homogenizer 172, which mixes the light to create mixed beam 105. Beam 105 may then enter imaging assembly 174, which reshapes the light into beam 107. Beam 105 then enters hot / cold mirror 176, which allows light of a first wavelength to pass but reflects light of a second wavelength. For example, light of 1000 nm may pass but light of a 450 nm wavelength may be reflected. Light projector 178 is capable of projecting low-power light. For example, light projector 178 may project light at 1080p pixel resolution and 450 nm. Light projector 178 may emit beam 109, which then enters hot / cold mirror 176. Beams 107 and 109 overlap beam 111, and both are imaged onto optically addressed light valve 180. The images formed from light uniformizer 172 and projector 178 are recreated and overlapped on light valve 180.

[0009] The optically addressed light valve 180 is stimulated by light (e.g., the wavelength of the light can be in the 400-500 nm range) to imprint (add) a polarization rotation pattern onto the transmitted beam 111 that is incident on the polarizer 182. The polarizer 182 separates the two polarization states, transmitting the p-polarized light as beam 117 and reflecting the s-polarized light as beam 115. The beam 115 is then sent to a beam dump 118, which processes the waste energy. As will be understood, in other embodiments, the polarizations can be reversed, such as s-polarized light being beam 117 and beam 115 being reflected as p-polarized light. The beam 117 enters the final imaging assembly (image relay) 120, which includes optics 184 that resize the patterned light. This beam is reflected by a movable mirror 186 into beam 119, which terminates in a focused image that is applied to a material bed (material) 144 in the article processing unit 140. The depth of field of the image is selected to span multiple layers, providing an optimal focus for a range of several layers of error or offset.

[0010] Article processing unit 140 may be connected to one or both of control processors 150 and 152. Control processor 150 or 152 may be connected to various sensors, actuators, heating or cooling systems, monitors, and controllers to coordinate the operation of components of bed 190 and article processing unit 140. These may include a camera 160 and a photodiode 155 to monitor energy patterning system 110 (e.g., including a high flux laser (HFL), a diode laser (DL), or a light valve (LV)) and to monitor bed and powder conditions at article processing unit 140. As will be understood, processors 150 and 152 may be connected to each other or to other control units not shown, and may operate independently or in conjunction with each other.

[0011] In one embodiment, the bed 190 can be raised and lowered (slid vertically) within the chamber wall 188 containing the material (material bed) 144 dispensed by the material dispenser 142. Materials (material bed) 144 applicable to these techniques can include metals, ceramics, glasses, and polymers. For example, any metal available in powder form (including, but not limited to, steel, copper, aluminum, titanium, tungsten, various alloys, and others). In various examples, the size of the metal powder can range from less than 1 micron to less than 1 millimeter (100 nanometers to less than 1 millimeter). In other examples, ceramic or glass in powder form can be used. The ceramic or glass powder can be composed of a material with a close glass transition temperature. The powder size of the ceramic or glass powder can range from less than 1 micron to less than 1 millimeter (100 nanometers to less than 1 millimeter). In the plastic category, any semi-crystalline polymer (including but not limited to polyamide, polystyrene, polypropylene, thermoplastic elastomers, and polyaryletherketone), the size of the plastic powder can range from sub-micron to sub-millimeter (100 nanometers to sub-millimeter).

[0012] In one embodiment, the floor 190 can remain fixed and the optics of the final imaging assembly (image relay) 120 can be raised or lowered vertically. Material distribution is provided by a sweeper mechanism 192 that can evenly spread the material powder held in a hopper 194 and provide a new layer of material as needed. The image can be continuously directed to various locations on the floor by a movable mirror 186.

[0013] When using powdered ceramic or metallic materials in this additive manufacturing system 100, the powder can be spread in thin layers, approximately 1-1 grains thick, on top of the base substrate (and subsequent layers) as the part is built. When melted, sintered, or fused by the patterned beam 119, the powder bonds to the layers below, creating a solid structure. The patterned beam 119 can be operated in a pulsed manner, for example, at 40 Hz pulses. Six subsequent image locations can be moved, for example, at intervals of 10 ms to 0.5 ms (0.1 ms), with intervals of 3 ms to 0.1 ms being preferred, until the selected area of ​​the patterned powder is melted. The bed 190 then lowers by a thickness corresponding to one layer, and the sweeper mechanism 192 spreads a new layer of powder material. This process is repeated until the 2D layers build the desired 3D structure. In some embodiments, the article processing unit 140 can be atmospherically controlled. This allows highly reactive materials to be produced in an inert gas or vacuum environment without the risk of oxidation or chemical reaction, or (if highly reactive metals are used) fire or explosion.

[0014] FIG. 2A illustrates one embodiment of a diagnostic and measurement technique (suitable for use in conjunction with a system such as that described with respect to FIG. 1) that relies on backscatter measurements for determining powder size in the print bed. In some embodiments, incident scattering by small particles longer than the wavelength of light will result in a set of ray angles that depend on the particle's size (i.e., small particles will scatter light into wider angles than larger particles). Additionally, because all particles receive equal amounts of laser flux, the integrated energy per scattered solid angle favors small versus larger particles, and when the optical system is configured to perform an optical Fourier transform on the sensing plane, the power relative to the received amount will fall within distinct spatial imaging bins. As seen with respect to optical measurement system 200A, an input probe beam 5A enters a galvanometer system 10A of an additive manufacturing printer, is reflected by the galvanometer system 10A, and strikes powder 25A on a build plate 20A. Typically, the flux of incident beam 15A is uniform, striking the powder uniformly throughout. If the powder consists of a distribution of powder particles (e.g., large to small spheres 30A and 35A) that, when struck by beam 15A, scatter into a collection of discrete range reflections 45A, each of which corresponds to the size of 30A, 40A, and 35A, respectively, this distribution of scattered light from 15A interacting with 25A will produce a collection of rays ranging from those striking 10A to those at larger angles. These high-angle rays pass through 50A at the edge of 10A and are picked up by one or more stray light reflectors 55A, which redirect them to lens 60A. If lens 60A is placed one focal length away from sensing surface 75A, the optical Fourier transform of 55A at 75A occurs. By optical Fourier transform (OFT), the angled light is transformed to spatial positions on 75A near the center of the axis of rotation of 60A, forming a distribution 70A that correlates with the size of the particle that produced it.The larger the angle (correlated to smaller particles), the larger the distribution on 75A. The response of small diameter spheres to 15A is illustrated by the detected spread of 70A on 75A, and the response of large diameter spheres is illustrated by 72A on 75A. Exemplary OFT response curves for distributions of three sphere sizes are shown in 77A, with each distribution shown as a dotted line below the combined curve 74A.

[0015] In an alternative embodiment, the main HFL or DL ​​beam is used to illuminate 25A while the OFT detection remains as shown. In another embodiment, the backscatter field is moved outside the chamber. Advantageously, this reduces the cost and complexity associated with moving the optical measurement system 200A along with the optics of the galvo system 10A.

[0016] 2B illustrates an example of the use of backscatter and controlled coherence system 200B to determine powder size and powder depth. In one example, the coherence of probe beam 5B is controlled by an electro-optic phase delay, either in the gain cavity or before it reaches system 200B. In some embodiments, the coherence of probe beam 5B can be adjusted so that the backscattered light is interfered (optically mixed) at the detection surface, registering certain sizes and not detecting smaller particles. This allows a depth profile to be determined based on the coherence (depth) and scattering profile (sphere diameter).

[0017] In the example, probe beam 5B enters galvo system (10B) and is reflected by 10B to become 15B before interacting with powders of various diameters (25B) on the build plate (20B). Backscatter (40B) from 15B interacting with 25B creates an angled light collection consisting of a portion of high-angle light 50B that is not reflected again by 10B but is collected by 55B before being collimated by lens 60B. This collected light enters beam splitter 70B, which merges it with the delayed sample of 5B, now 65B (which serves as the reference beam). The combined reference and sample scattered beams pass through OFT lens (75B) where they are focused onto detector plane (80B) so that their interference pattern (85B) can be detected and recorded. For a particular optical delay introduced by its phase LV in 65B, an exemplary scattering interference pattern for three sphere distributions with distinct patterned responses (90B) with respect to sphere size consistent with a common coherence function for 5B and 65B can be seen in this 87B. By adjusting the coherence of 5B and 65B, it is possible to sweep a range of sphere sizes in a specific plane parallel to 20B and within 25B. This ability to adjust sphere size is unique to optical coherence sources whose described readout uses an interferogram. As the coherence of 5B / 65B is varied, other curves become apparent, such as 95B and 100B. Assuming that 100B is associated with a small sphere while 90B is due to a large sphere and this is evident at one extremum of the coherence function, if one shifts the 5B / 65B coherence function towards the other extremum, first 95B will become evident then decrease and then 100B will become evident towards the other extremum of the coherence function while the curve shown by 90B will weaken.

[0018] By adjusting the phase delay between 5B and 65B in the phase LV (not shown), a scan can be performed at the depth depicted at 105B. The peak depicted at 87B is depicted at 105B because the decaying curves are not clear scans with stable peak locations (the peaks are related to sphere size). The decrease in distribution intensity (Y-axis in these curves) indicates depth and the amount of scattering loss that depth to 25B causes at 40B. Thus, adjusting the 5B / 65B coherence provides the sphere size (from the 87B curve), and adjusting the phase at 65B provides a measure of depth. By adjusting the 5B / 65B coherence function at 105B, as at 87B, it is possible to "dial in" the sphere size at 120B, which is linked to 90B, and the 110B distribution at 100B within 25B.

[0019] While the phase delay at 65B does not need to be pixelated (the LV in this case could be substituted with a non-pixelated electro-optic phase cell—it does not need to be programmable to allow for tailored analysis), pixelated adjustability allows for depth compensation in the measurement due to fine scattering and non-uniformity of the distribution to be measured at any depth. In addition, the 5B / 65B area measurement of the pixelated phase LV delay at 65B allows the user to interrogate any portion of the voxel volume provided by the 5B / 65B (single plane) coherence function, with the phase delay of each pixel overlapping between 5B and 65B (the third / depth dimension in the interferogram resulting when these two image planes interfere at 80B).

[0020] Other embodiments of this system could use a set of static phase plates instead of the phase LV at 65B, which could reduce cost at the expense of voxel spatial resolution. Another embodiment could use an HFL or diode beam instead of the probe beam. Such an embodiment could reduce system complexity, but could require a faster image generator at 80B depending on how timing works due to interference with short pulse sources.

[0021] Yet another embodiment is to use HFL / diode (HFL / diode beam) as 5B / 65B and use discarded light from the patterning LV and pass this discarded light through a switchyard system for reformatting and patterning conditions, where 5B is the patterning HFL / diode (HFL / diode beam) and 65B is the reformatted discarded light.

[0022] Yet another embodiment is to use this technique either on a pre-processed build plate before printing or on the top layer of a current print to determine the remelt requirements in either case.

[0023] Yet another alternative is to use other interferometer configurations; collinear combination at 200B (60B) is performed using beam splitter 70B. Alternatively, a Mach-Zehnder configuration (Mach-Zehnder interferometer) can be used if 5B and 65B are polarized. Additionally, if polarized light is used, this procedure can be used to gain understanding of stress or the part currently being printed.

[0024] FIG. 2C illustrates an example of a volumetric printing system 200C for additive manufacturing using adaptive optics techniques including backscatter coherence analysis. This technique utilizes vector processing of the HFL / diode beam and applies adaptive optics in conjunction with holographic LV. A flow logic diagram of backscatter coherence analysis is depicted in FIG. 5C, in which a probe beam interacts with the powder bed before printing occurs, and the probe beam's phase information is used along with the coherence function to determine complex scattering parameters from the powder layer (20C). This complex scattering response typically perturbs the patterned HFL / diode beam (10C), allowing only the top surface of the powder layer (20C) to be printed with the HFL pattern (25C). In this system, the probe beam response produced by 5C becomes the input to a holographic LV that applies vector modifications (intensity, angle, phase) to the HFL / diode beam, which allows voxel printing to occur by forming voxel images in the powder when these interact with 20C in the form of 15C (30C).

[0025] FIG. 2D illustrates an example diagnostic imaging system 200D for real-time print quality assessment using backscattered light. In this system 200D, a print (5D) is in progress on a build plate 1D while the current print surface (10D) is inspected by various imaging modalities (40D, diagnostic imaging system). A patterned HFL / diode (15D, HFL / diode beam) enters the build chamber and is reflected by a galvanometer mirror (25D) to form 10D. An off-axis illumination system (20D) illuminates 10D, generating backscattered light, some of which extends beyond the angular range of 25D and is captured by a backscatter optical system consisting of a rotating mirror (30D) and a diagnostic imaging system (imaging modality) 40D. Side illumination can be at multiple positions around 10D using more illuminators, resulting in fewer shadows in the final image. Illumination and modalities can be at wavelengths and polarizations not used by 15D to reduce optical noise detection and enhance diagnostic contrast capabilities. The illumination may be pulsed or synchronized to avoid overlap with the temporal emission of the HFL / diode (HFL / diode beam) to enhance diagnostic electrical contrast capabilities and contribute to eliminating electrical noise while expanding the spatiotemporal bandwidth received from the 20D.

[0026] Other embodiments may use the HFL / diode beam as illumination for the part with focus as shown in addition to light passing through 25D for a second diagnostic to measure the characteristics of the melt pool and the dynamics as this pool cools / condenses and solidifies.

[0027] FIG. 2E illustrates an additive manufacturing system 200E that can enable the various control and diagnostic monitoring described with respect to FIGS. 1 and 2A-D. The system 200E includes various potential stations in a printing facility (station) 2E. In some embodiments, the powder bed is provided by a removable cartridge that can be loaded into the station. In some embodiments, multiple article handling units, cartridges, or build chambers, each with a build platform for holding a powder bed, can be used with multiple opto-mechanical assemblies arranged to receive and direct one or more incident energy beams into the cartridge. Multiple cartridges enable the simultaneous printing of one or more print jobs. An example of a station can be a print station with a cartridge to which an energy source (laser or electron beam) is transferred from a laser engine (station) to print parts. Typically, a laser engine is used only in conjunction with the print station to convert the combination into a print engine. The stations can be arranged and connected to each other to form a manufacturing system. The manufacturing system may include many stations with cartridges, captured within a frame apparatus and coordinated by a control system, supporting stations that receive printing instructions from users to fulfill print orders / jobs. These other functional stations may include soiling processes to reduce human exposure in the creation of 3D parts. Additionally, system interfaces may be provided for interaction with various diagnostic systems. The control system and database 4E may communicate with cartridges or other print bed or article handling systems, either separately or when connected to any one of the listed stations (2E, printing equipment) or while operated by the transporter 5E. The listed stations are not an all-inclusive list, but include the print engine (consisting of a print station and a laser engine), storage (rack) stations, equipment stations, and powder preparation / powder removal stations. The powder preparation station may include removal of powder that has already been printed and may be a station for preparing the powder bed.These two functions (powder bed preparation and powder removal) may be performed in one station or in two separate stations, in which case the preparation station may be referred to as "prep" and the powder removal station may be referred to as "powder removal." Other stations may include surface coating stations, heat treatment stations, CNC / machining stations, surface finishing stations, prep service stations, deburring stations, powder resieving stations, powder surface treatment / coating stations, diagnostic stations, other volumetric and surface diagnostic stations, and other processing stations. The laser engine may be coupled to and interact with the printing station, the surface coating station, and the diagnostic station (to form a printing engine), and may interact with the heat treatment station and the surface finishing station.

[0028] Printing stations, surface coating stations, heat treatment stations, CNC / machining stations, surface finishing stations, and deburring stations can be used for post-processing of printed parts. The surface coating station works in conjunction with a laser engine on the printed part to add a functional layer to selected surfaces, such as on drill bits, airfoil surfaces, turbine blades, or medical implants. The heat treatment station can work in conjunction with a laser engine to perform surface annealing and hardening, or this form of post-processing can be performed using other conventional methods, such as standard heat sources or directed energy non-laser sources. The CNC / machining station performs standard subtractive manufacturing on the printed part for its final shape and form. The surface finishing station can interact with the laser engine to perform surface smoothing through mass transport / surface tension or laser peening / hardening. The surface finishing station can also work in more traditional subtractive methods. The deburring station can use conventional subtractive processing methods to improve the surface finish of the printed part.

[0029] The prep service station is used to service the system 200E and may be used in conjunction with the powder station and equipment station. At the prep station, consumables are replaced in a manner that minimizes human interaction with the dirty environment. Gases and fluids are removed for post-processing through the equipment station. Used powder is removed and transferred to the powder re-sieving station for powder reuse.

[0030] The powder processing / coating station processes the powder for chemical reactions or emissivity enhancement, which may depend on which powder / metal is being used, but may include chemical or oxide treatments to enhance emissivity by adding chemical dopants to the powder for specific printing parameters (e.g., increasing the absorption of copper or steel by surface treating the powder).

[0031] A diagnostic station may be coupled to the laser engine to volumetrically scan the printed parts to improve print accuracy, density, and defect statistics. Additionally, volumetric or other diagnostics, including those described with respect to Figures 1 and 2A-D, may be used in conjunction with the storage station and laser engine to determine the functionality of the printed parts under conditions such as high or low temperatures, high pressure, partial vacuum, or other extreme environments or operations to ensure the printed parts will withstand static operational performance requirements.

[0032] Other diagnostic stations may include X-ray tomography, surface scanning imaging, high resolution surface and thermographic imaging, and select some way in which the printed part is manipulated while minimizing damage during processing and avoiding exposing humans to dangerous measurement methods (as is the case with X-ray tomography).

[0033] In another embodiment, illustrated with respect to FIG. 3, an additive manufacturing system is represented by various modules that form the additive manufacturing method and system 300. As seen in FIG. 3, the laser source and amplifier 312 can be made as a continuous or pulsed laser device. In other embodiments, the laser source includes a pulsed electrical signal source, such as an arbitrary waveform generator, or equivalent that operates on a continuous laser source, such as a laser diode. In some embodiments, this can also be achieved via a fiber laser source or a fiber launched laser source that is subsequently modulated by an acousto-optic or electro-optic modulator. In some embodiments, a high repetition rate pulse source using a Pockels cell can be used to create pulse trains of any length.

[0034] Possible laser types 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-pumped lasers.

[0035] Gas lasers may include lasers such as helium-neon lasers, argon lasers, krypton lasers, xenon ion lasers, nitrogen lasers, carbon dioxide lasers, carbon monoxide lasers, or excimer lasers.

[0036] Chemical lasers may include lasers such as hydrogen fluoride lasers, deuterium fluoride lasers, COIL (chemoenzymatic iodine lasers), or Agil (all vapor phase iodine lasers).

[0037] Metal vapor lasers can include lasers such as helium-cadmium (HeCd) metal vapor lasers, helium-mercury (HeHg) metal vapor lasers, helium-selenium (HeSe) metal vapor lasers, helium-silver (HeAg) metal vapor lasers, strontium vapor lasers, neon-copper (NeCu) metal vapor lasers, copper vapor lasers, gold vapor lasers, manganese (Mn / MnCl) vapor lasers, etc. Rubidium or other alkali metal vapor lasers can also be used. Solid-state lasers include ruby ​​lasers, Nd:YAG lasers, NdCrYAG lasers, Er:YAG lasers, neodymium YLF (Nd:YLF) solid-state lasers, neodymium-doped yttrium orthovanadate (Nd:YVO4) lasers, neodymium-doped yttrium calcium oxoborate Nd:YCa4O(BO3)3 or simply Nd:YCOB, neodymium-glass (Nd:glass) lasers, titanium sapphire (Ti:sapphire) lasers, thulium YAG (Tm:YAG) lasers, yttrium YAG (Yb:YAG) lasers, yttrium:2O3 (glass or ceramic) lasers, yttrium-doped glass lasers (rod, plate / The lasers may include lasers such as fluorine-doped uranium (Ce:YAG) lasers, chromium ZnSe (Cr:ZnSe) lasers, cerium-doped lithium strontium (or calcium) aluminum fluoride (Ce:LiSAF, Ce:LiCAF), promethium-147 doped phosphate glass (147Pm+3:glass) solid-state lasers, chromium-doped chrysoberyl (alexandrite) lasers, erbium-doped 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.

[0038] The semiconductor laser device may include laser media such as GaN, InGaN, AlGaInP, AlGaAs, InGaAsP, GaInP, InGaAs, InGaAsO, GaInAsSb, lead salt, vertical cavity surface emitting laser (VCSEL), quantum cascade laser, hybrid silicon laser, or combinations thereof.

[0039] As shown in FIG. 3 , additive manufacturing system 300 uses a laser device capable of providing one- or two-dimensional directed energy as part of energy patterning system 310. In some embodiments, one-dimensional patterning can be directed as straight or curved strips, as rastered lines, as spiral lines, or in other suitable forms. Two-dimensional patterning can include separated or overlapping tiles or images with varying laser intensity. Two-dimensional image patterns with non-rectangular boundaries can be used, overlapping or interpenetrating images can be used, and images can be provided by two or more energy patterning systems. Energy patterning system 310 uses a laser source and amplifier 312 to direct one or more continuous or intermittent energy beams to beam shaping optics 314. After shaping, the beam is patterned, if necessary, by energy patterning unit 316, and generally some energy is directed to waste energy processing unit 318. The patterned energy is relayed by image relay 320 toward article processing unit 340. In one embodiment, two-dimensional image 322 is focused near floor 346. Article processing unit 340 may include a cartridge as described above. Article processing unit 340 has a plate or floor 346 (with walls 348) that together form an enclosed cartridge chamber containing material 344 (e.g., metal powder) to be dispensed by a powder hopper or other material dispenser 342. The dispensed powder may be crafted or recycled as described herein. The patterned energy directed by image relay 320 may melt, melt, sinter, fuse, change crystalline structure, affect stress patterns, or otherwise chemically or physically alter the dispensed, dispersed material 344 to form a structure with desired properties.Control processor 350 may be connected to various sensors, actuators, heating or cooling systems, monitors, and controllers to coordinate the operation of laser source and amplifier 312, beam shaping optics 314, laser patterning unit 316, and image relay 320, as well as any other components of system 300. As will be understood, connections may be wired or wireless, may be continuous or intermittent, and may have feedback capability (e.g., thermal heating may be adjusted in response to a sensed temperature).

[0040] In some embodiments, the beam shaping optics 314 may include a variety of imaging optics to combine, focus, diverge, reflect, refract, homogenize, intensity adjust, frequency adjust, or otherwise shape one or more laser beams received from the laser source and amplifier 312 and direct them toward the laser patterning unit 316. In one embodiment, multiple light beams, each having a different optical wavelength, may be combined using wavelength-selective mirrors (e.g., dichroic) or diffractive elements. In other embodiments, multiple beams may be homogenized or combined using polygonal mirrors, microlenses, and refractive or diffractive optical elements.

[0041] The laser patterning unit 316 may include static or dynamic energy patterning elements. For example, the laser beam may be interrupted by a mask with fixed or movable elements. Pixel-addressable masking, image generation, or transmission may be used to increase the flexibility and ease of image patterning. In some embodiments, the laser patterning unit includes addressable light valves alone or in combination with other patterning mechanisms to provide the patterning. The light valves may be transmissive, reflective, or may use a combination of transmissive 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, with optically addressed pixels forming a pattern defined by the optical projection source. In another embodiment, a reflective optically addressed light valve includes a write beam to modify the polarization of a read beam. In some embodiments, non-optically addressed light valves may be used. These may include, but are not limited to, electrically addressable pixel elements, movable mirror or micromirror systems, piezoelectric or micro-actuated optical systems, fixed or movable masks or shielding plates, or other conventional systems capable of providing high intensity light patterning.

[0042] The waste energy processing unit 318 can be used to dissipate, redirect, and utilize energy that was not patterned and passed through (skipped) the image relay 320. In one embodiment, the waste energy processing unit 318 can include passive or active cooling elements to remove heat from both the laser source and amplifier 312 and the laser patterning unit 316. In other embodiments, the waste energy processing unit can include a "beam dump" to absorb and convert to heat any beam energy not used to define the laser pattern. In yet other embodiments, the wasted laser beam energy can be recycled using the beam shaping optics 314. Alternatively or additionally, the wasted beam energy can be directed to the article processing unit 340 for heating or further patterning. In some embodiments, the wasted beam energy can be directed to an additional energy patterning system or article processing unit.

[0043] In one embodiment, a "switchyard" type optical system may be used. The switchyard system is suitable for reducing light wasted in additive manufacturing systems due to unwanted light waste caused by the pattern to be printed. The switchyard involves redirecting a complex pattern from its generation (in this case, a plane where a spatial pattern is imparted to a structured or unstructured beam) to its transmission through a series of switch points. Each switch point may optionally modify the spatial profile of the incident beam. The switchyard optical system may be utilized in, for example, but not limited to, laser-based additive manufacturing techniques where a mask is applied to the light. Advantageously, in various embodiments of the present disclosure, wasted energy may be recycled, either in a homogenized form used to maintain high power efficiency or high throughput, or as patterned light. Furthermore, wasted energy may be recycled and reused to increase intensity for printing more challenging materials.

[0044] Image relay 320 may receive the patterned image (whether one-dimensional or two-dimensional) from laser patterning unit 316 directly or through a switchyard and direct it toward article processing unit 340. In a manner similar to beam shaping optics 314, image relay 320 may include optics to combine, focus, split, reflect, refract, adjust intensity, adjust frequency, or otherwise shape and direct the patterned light. The patterned light may be directed using moveable mirrors, prisms, diffractive optical elements, or solid-state optical systems that do not require substantial physical movement. One of the lens assemblies may be configured to provide incident light having the magnification at both the first set of optical lenses and the second set of optical lenses, and at the second set of optical lenses that are interchangeable from the lens assemblies. Rotation of a set of one or more mirrors mounted on a compensating gantry and a final mirror mounted on the build platform gantry can be used to direct the incident light from the leading mirror to the desired location. Translational movement of the compensating gantry and the build platform gantry can also ensure that the distance of the incident light from the leading mirror to the article handling unit 340 is substantially equal to the image distance. In practice, this allows for rapid change of the optical beam transmission size and intensity across the build zone location for various powder materials while ensuring high system availability.

[0045] A material dispenser 342 (e.g., a powder hopper) within the article processing unit 340 (e.g., a cartridge) can disperse, remove, or mix materials, provide gradations or variations in material type or particle size, or adjust the thickness of a material layer. Materials can include metals, ceramics, glasses, polymer powders, other dissolvable materials capable of undergoing a heat-induced phase change from solid to liquid and vice versa, or combinations thereof. Materials can also include composites of dissolvable and indissolvable materials, in which either or both components can be selectively targeted with an image relay system to melt the dissolvable component, while either leaving only the indissolvable material or subjecting it to evaporation, destruction, combustion, or other destructive processes. In certain embodiments, slurries, sprays, coatings, wires, strips, or sheets of material can be used. Unwanted material may be removed by using a blower, a vacuum system, sweeping, vibrating, shaking, sloping, or inverting the floor 346 for disposal or recycling.

[0046] In addition to material processing components, the article processing unit 340 may include components for holding and supporting three-dimensional structures, mechanisms for heating or cooling the chamber, auxiliary or supporting optics, and sensors and control mechanisms for monitoring or adjusting material or environmental conditions. The article processing unit may, in whole or in part, support a vacuum or inert gas atmosphere to reduce unwanted chemical interactions and reduce the risk of fire or explosion (especially with reactive metals). In some embodiments, the article processing unit may be configured with an inert gas atmosphere, such as Ar, He, Ne, Kr, Xe, CO2, N2, O2, SF6, CH4, CO, N2O, C2H2, C2H4, C2H6, C3H6, C3H8, i-C4H10, C4H10, 1-C4H8, cic-2, C4H7, 1,3-C4H6, 1,2-C4H6, C5H12, n-C5H12, i-C5H12, n- Various pure or mixtures of other atmospheres may be used, such as atmospheres containing C6H14, C2H3Cl, C7H16, C8H18, C10H22, C11H24, C12H26, C13H28, C14H30, C15H32, C16H34, C6H6, C6H5-CH3, C8H10, C2H5OH, CH3OH, iC4H8. In some embodiments, refrigerants or large, inert molecules (including, but not limited to, sulfur hexafluoride) may be used. An enclosure atmospheric composition having at least about 1% helium by volume (or number density) and a selected proportion of an inert / non-reactive gas may be used.

[0047] The control processor 350 can be connected to control any component of the additive manufacturing system 300 described herein, including the laser, laser amplifiers, optics, heating controls, build chamber, and manipulation devices. The control processor 350 can be connected to various sensors, actuators, heating or cooling systems, monitors, and controllers to coordinate their operation. A wide range of sensors can be used to provide information used for control or monitoring, including imaging devices, light intensity monitors, heat, pressure, or gas sensors. The control processor can be a single central controller, or alternatively, can include one or more independent control systems. The control processor 350 is provided with an interface that allows for input of manufacturing instructions. The use of a wide range of sensors enables a variety of feedback control mechanisms that improve quality, manufacturing throughput, and energy efficiency.

[0048] One embodiment of the operation of a manufacturing system suitable for additive or subtractive manufacturing is illustrated in FIG. 4. In this embodiment, a flowchart 400 illustrates one embodiment of a manufacturing process supported by the described optical and mechanical components and including the use of various optical diagnostic systems as described herein above. In step 401, a powder of material, created or recycled as described in this disclosure, is formed. In step 402, the powder material is positioned in a cartridge, bed, chamber, or other suitable support. In some embodiments, the material may be a metal plate for laser cutting using subtractive manufacturing techniques, or a powder that can be melted, fused, sintered, altered by additive manufacturing techniques to change crystal structure, affect stress patterns, or otherwise chemically or physically modified to form a structure with desired properties.

[0049] In step 404, unpatterned laser energy is emitted by one or more energy emitters, including, but not limited to, solid-state or semiconductor laser devices, and then amplified by one or more laser amplifiers. In step 406, the unpatterned laser energy is shaped and modified (e.g., intensity modulated or focused). In step 408, the unpatterned laser energy is patterned, whereby energy that does not form part of the pattern is processed in step 410 (this may include conversion to waste heat, recycling as patterned or unpatterned energy, or waste heat generated in cooling the laser amplifiers in step 404). In step 412, the patterned energy, now forming a one- or two-dimensional image, is relayed toward the material. In step 414, the image is applied to the material to produce part of a 3D structure, whether by subtractive or additive manufacturing. Information obtained from applying the patterned laser energy to the material can be used to identify powder size or other necessary diagnostics or measurements (step 415). In the case of additive manufacturing, these steps may be repeated (loop 418) until the image (or another subsequent image) has been applied to all required areas of the top layer of material. Once the application of energy to the top layer of material is complete, a new layer may be applied (loop 416) to continue building the 3D structure. These processing loops continue until any remaining excess material can be removed or recycled and the 3D structure is complete.

[0050] FIG. 5 illustrates one embodiment of an additive manufacturing system including a phase-change light valve and switchyard system that enables two-dimensional patterned energy recycling. Additive manufacturing system 520 includes an energy patterning system with a laser source and amplifier 512 that directs one or more continuous or intermittent laser beams into shaping optics 514. Residual heat can be transferred into a waste energy processing unit 522, which may include an active light valve cooling system. After shaping, the beam is patterned in two dimensions by energy patterning unit 530, and approximately some of the energy is directed into waste energy processing unit 522. The patterned energy is relayed by one of multiple image relays 532 to one or more article processing units 534A, 534B, 534C, or 534D, typically as a two-dimensional image focused near a moving or fixed floor. The floor can be in a cartridge containing a powder hopper or similar material dispenser. The patterned laser beam directed by the image relay 532 may melt, melt, sinter, fuse, change the crystal structure, affect stress patterns, or otherwise chemically or physically modify the dispensed material to form a structure with desired properties.

[0051] In this embodiment, the waste energy processing unit has multiple components to enable reuse of the patterned waste energy. Coolant from the laser amplifier and source 512 can be directed to one or more of the generator 524, the heating / cooling thermal management system 525, or the energy dump 526. Additionally, repeaters 528A, 528B, and 528C can each transfer energy to the generator 524, the heating / cooling thermal management system 525, or the energy dump 526. Optically, repeater 528C can direct the patterned energy to image repeater 532 for further processing. In other embodiments, the patterned energy can be directed by repeater 528C to repeaters 528B and 528A for insertion into the laser beam provided by the laser source and amplifier 512. Using image repeater 532, reuse of the patterned image is also possible. The image may be redirected, inverted, reflected, sub-patterned, or converted for distribution to one or more article processing units 534A-D. Advantageously, recycling of patterned light may improve the energy efficiency of the additive manufacturing process and, in some cases, may improve the intensity of energy directed to the bed or reduce production time. In some embodiments, information obtained from applying patterned laser energy to material in one or more of the article processing units 534A-D may be used to identify powder size or for other necessary diagnostics or measurements using the diagnostic module 540 and the techniques and systems described above with respect to FIGS. 1 and 2A-D.

[0052] Many modifications and other embodiments of the invention will occur to those skilled in the art having the benefit of the teachings presented in the foregoing description and the associated drawings. It is understood, therefore, that the invention is not 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 the invention may be practiced that exclude elements / steps not specifically disclosed herein.

Claims

1. 1. A print engine of an additive manufacturing system supporting a powder measurement system, comprising: a printing bed capable of holding powders of various sizes; a laser energy patterning system directable to the print bed; and a backscatter detection system capable of evaluating the scattered light distribution from the powder on the print bed and determining powder size; The print engine.

2. 10. The print engine of claim 1, wherein the laser energy patterning system is capable of directing a two-dimensional laser image onto the print bed. The print engine.

3. 10. The print engine of claim 1, wherein the laser energy patterning system comprises a high flux laser. The print engine.

4. 10. The print engine of claim 1, wherein the laser energy patterning system comprises a diode laser device. The print engine.

5. 10. The print engine of claim 1, wherein the backscatter detection system uses an optical Fourier transform. The print engine.

6. 1. A print engine of an additive manufacturing system supporting a powder measurement system, comprising: a printing bed capable of holding powders of various sizes; a laser energy patterning system directable to the print bed; and a detection system capable of determining powder size and powder depth using a coherent probe beam and backscatter response that combine to provide an interference pattern; The print engine.

7. 7. The print engine of claim 6, wherein the laser energy patterning system is capable of directing a two-dimensional laser image onto the print bed. The print engine.

8. 7. A print engine as recited in claim 6, wherein the backscatter detection system uses a static phase plate. The print engine.

9. 7. The print engine of claim 6, wherein the backscatter detection system uses discarded light from a light valve in the laser energy patterning system. The print engine.

10. 7. The print engine of claim 6, wherein the backscatter detection system uses a Mach-Zehnder interferometer. The print engine.

11. 1. A print engine of an additive manufacturing system supporting a powder measurement system, comprising: a printing bed capable of holding powders of various sizes; a laser energy patterning system having a holographic light valve capable of patterning laser energy directable to the print bed; and a detection system capable of determining powder size and powder depth using a coherent probe beam and backscatter response; The print engine, wherein the sensing system response is used to modify input to the holographic light valve to enable volumetric voxel printing using the laser energy patterning system.

12. 12. The print engine of claim 11, wherein the laser energy patterning system is capable of directing a two-dimensional laser image onto the print bed. The print engine.

13. 1. A print engine of an additive manufacturing system supporting a powder measurement system, comprising: a printing bed capable of holding powders of various sizes; a laser energy patterning system having a high flux laser directable to the print bed; a detection system capable of determining powder size and powder depth using off-axis backscatter illumination timed to illuminate the print bed and any contained articles when the high flux laser device is not emitting; The print engine.

14. 14. The print engine of claim 13, wherein the laser energy patterning system is capable of directing a two-dimensional laser image onto the print bed. The print engine.

15. 1. A laser energy patterning system comprising: a plurality of semiconductor laser devices directed at a light homogenizer that forms a mixed beam that is directed at a hot / cold mirror that passes light at a first wavelength and reflects light at a second wavelength; an optical projector that projects light at the second wavelength toward the hot-cold mirror and allows the mixed beam to overlap with projector light reflected from the hot-cold mirror; and a light valve stimulated by light of a second wavelength incident thereon to form an image pattern on the light valve, the light valve transmitting a first portion of the mixed beam and reflecting a second portion of the mixed beam to a beam dump; the laser energy patterning system comprising:

16. 16. The laser energy patterning system of claim 15, wherein the first portion of the mixed beam transmitted through the light valve is directed toward a print bed capable of holding powders of various sizes. The laser energy patterning system.

17. 17. The laser energy patterning system of claim 16, further comprising a detection system capable of determining powder size and powder depth in the print bed using a coherent probe beam and backscatter response that combine to provide an interference pattern. The laser energy patterning system further comprises:

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