HK40016483B - Method and system for additive manufacturing with powder material - Google Patents

Description

Methods and systems for material additive manufacturing using powders

Technical Field

In some embodiments, the present invention relates to the field of additive manufacturing, and more particularly, but not exclusively, to methods and systems for generating three-dimensional printed models having a high material density.

Background

Many different methods of manufacturing solid objects by additive manufacturing of successive layers of powder material are known. Some known additive manufacturing techniques selectively apply a liquid bonding material based on a three-dimensional model of an object, bonding the powdered material together layer-by-layer to build a solid structure. In some processes, at the end of the build process, the object is heated and/or sintered to further strengthen the bonding of the materials.

Selective Laser Sintering (SLS) uses a Laser as a power source to sinter layers of material of a powder. The laser is controlled to aim at a plurality of points in space defined by a three-dimensional model, bonding the materials together layer by layer to build a solid structure. Selective Laser Melting (SLM) is a comparable technique to Selective laser sintering, which involves complete melting of the material rather than sintering. Selective laser melting is often used when the melting temperature of the powder is uniform, for example when pure metal powders are used as building materials.

U.S. patent No. 4,247,508, entitled "MOLDING PROCESS," which is incorporated herein by reference, describes a MOLDING PROCESS for layer-by-layer formation of three-dimensional articles. In one embodiment, the planar layer of material is deposited sequentially. In each layer, an area of a portion thereof is cured to define the portion of the article in that layer prior to deposition of the next layer. Selective curing of each layer may be achieved by using heat and a selected mask or by using a controlled thermal scanning process. A separate mask and a heat source may be used for each layer instead of using a laser to selectively fuse each layer. The mask is placed over its associated layer and a heat source is placed over the mask. The heat through the mask openings will fuse the particles exposed through the mask openings. Particles that are not exposed to direct heat will not melt.

U.S. patent No. 5076869 entitled "materials systems FOR SELECTIVE BEAM SINTERING" (multi MATERIAL SYSTEMS FOR SELECTIVE BEAM SINTERING) describes a method and apparatus FOR selectively SINTERING a powder layer to produce a component comprising a plurality of sintered layers, the contents of which are incorporated herein by reference. The apparatus includes a computer that controls a laser to direct energy of the laser onto the powder to create a fired cake. For each cross-section, the target of the laser beam is to scan over a powder layer and turn on the beam to sinter only the powder within the boundaries of the cross-section. The powder is applied and successive layers sintered until a complete part is formed. Preferably, the powder comprises a plurality of materials having different dissociation or bonding temperatures. Preferably, the powder comprises a mixed or coated material.

International patent publication No. WO 2015/170330, entitled "METHOD AND APPARATUS FOR three-dimensional printing BY selective sintering (METHOD AND APPARATUS FOR 3D PRINTING BY SELECTIVE SINTERING"), the contents of which are incorporated herein BY reference, discloses a METHOD of forming an object BY three-dimensional printing, the METHOD comprising providing a layer of powder on a building tray, pressing the layer, sintering the layer, the layer being pressed molded BY selective laser sintering or selective laser melting, AND repeating the providing, pressing AND sintering each layer until the three-dimensional object is completed. The disclosed selective sintering is performed by a mask pattern that defines a negative of a portion of the layer to be sintered.

Disclosure of Invention

According to an aspect of some embodiments of the present invention, there is provided a system and method for post-processing a powder compact built by additive manufacturing using multiple powder layers. In some exemplary embodiments, aluminum alloy powder is used as the build material. Alternatively, other materials may be used, such as pure aluminum, other metal powders, ceramic powder materials, polymeric plastic powder materials, or powder materials in any combination. Optionally, at the end of the layer-by-layer build process, the formation of a powder compact mass includes a pattern embedded therein, the pattern defining one or more green objects. According to some exemplary embodiments, the powder compact is compacted by Cold Isostatic Pressing (CIP). Optionally, a cold isostatic press is applied to increase the density of one or more green bodies, e.g., a plurality of green objects embedded in a compact (e.g., a compact block). The cold isostatic pressing may increase the density of the material forming the plurality of green objects to about 90 to 97% of the processed density of the build material. The remaining 3 to 10% may be air. Alternatively, a density of the plurality of green bodies prior to cold isostatic pressing may be 85 to 90% of the processing density of the build material.

After cold isostatic pressing, the plurality of green objects embedded in the powder compact may be separated from the surrounding plurality of support elements and may be sintered. In some example embodiments, a second cold isostatic pressing process may be applied to further increase the density of the plurality of green object bodies (or one green object body) prior to sintering. Optionally, a second cold isostatic pressing process is applied to the plurality of green objects after the cured ink and support material in the powder compact are removed. In some exemplary embodiments, the second cold isostatic pressing process may cause the density of the material forming the object to be greater than 95% and close to 100% of its processing density.

According to an aspect of some exemplary embodiments, there is provided a method of producing a three-dimensional model by additive manufacturing, the method comprising: constructing a green compact block in a layer-by-layer manner using a powdered material and a solidified non-powdered material, the green compact block including a green-usable model; removing said solidified non-powder material from said green block and removing said green usable model from said green block; increasing the density of the green usable model by applying cold isostatic pressing; and sintering the green utilizable model to produce a three-dimensional model.

Optionally, the cold isostatic press is applied to the green block, the green block comprising the green usable model.

Optionally, the cold isostatic press is applied to the green usable model after the green usable model is removed from the green block.

Optionally, a first cold isostatic press is applied to the green block, the green block comprising the green usable model, and a second cold isostatic press is applied to the green usable model after the green usable model is separated from the green block.

Optionally, the green usable model is a powder compact of a usable model.

Optionally, the step of building the green compact in the layer-by-layer manner is performed by an additive manufacturing system configured to build a layer by: (1) printing a pattern using a cured non-powder material to trace the contours of the green usable model; (2) dispensing and coating a powdered material over the pattern; and (3) compacting the powder layer using the pattern.

Optionally, the powder material is selected from the group consisting of an alloy powder, a pure metal powder, a ceramic powder, a polymer powder, and any combination or mixture thereof.

Optionally, the material of the powder is an aluminum alloy.

Optionally, the cured non-powder material is a cured ink selected from the group consisting of a plurality of photo-curable inks, a wax, a plurality of thermosetting inks, and any combination thereof.

Optionally, the step of removing the solidified non-powder material from the green compact is performed by heating the green compact to melt, burn or evaporate the solidified non-powder material.

Optionally, the green usable mold shape is extracted from the green block by removing a plurality of green support elements.

Optionally, applying the cold isostatic press to the green compact comprises inserting the green compact into a wet bag, optionally removing air from the wet bag, placing the wet bag into a cold isostatic press chamber, and applying an isostatic press to the wet bag containing the green compact.

Optionally, the isostatic pressure is up to 2500 bar (bar).

Optionally, applying a cold isostatic press to the green usable model after removing the green usable model from the green block comprises inserting the green usable model with a buffer material into a wet bag, optionally removing air from the wet bag, placing the wet bag into a cold isostatic press chamber, and applying an isostatic press to the wet bag, the wet bag comprising the green usable model.

Optionally, the isostatic pressing is applied in two steps, wherein the first step comprises applying a first isostatic pressing sufficient to melt the buffer material to flow the buffer material within the hollow structure of the green usable model, and the second step comprises applying a second isostatic pressing to compact the green usable model.

Optionally, the buffer material is wax powder, the first isostatic pressure is up to 50 bar, and the second isostatic pressure is up to 2600 bar.

Optionally, a temperature applied during cold isostatic pressing is about 40 ℃.

According to an aspect of some exemplary embodiments, there is provided a method of generating a plurality of three-dimensional models by additive manufacturing, the method comprising: constructing a green compact in a layer-by-layer manner using a powdered material and a solidified non-powdered material, the green compact including one or more powder compacts of a usable model and one or more powder compacts of a plurality of support elements, wherein the usable model and the support elements are defined by a plurality of pattern lines formed by selectively depositing the solidified non-powdered material; increasing the density of one or more powder compacts of the usable model by applying a cold isostatic press to the green compact; heating the green block to remove the solidified non-powder material; extracting one or more powder compacts of the usable mold from the green compact by removing the one or more powder compacts of the plurality of support elements; and sintering the one or more powder compacts of the usable model to produce a plurality of three-dimensional models.

According to an aspect of some exemplary embodiments, there is provided a method of generating a plurality of three-dimensional models by additive manufacturing, the method comprising: constructing, in a layer-by-layer manner, a green compact using a powdered material and a solidified non-powdered material, the green compact including one or more powder compacts of a usable model and one or more powder compacts of a plurality of support elements, wherein the usable model and the support elements are defined by a plurality of pattern lines formed by selective deposition of the solidified non-powdered material; increasing the density of one or more powder compacts of the usable mold by applying a first cold isostatic press to the green compact; heating the green block to remove the solidified non-powder material; extracting one or more powder compacts of the usable model from the green compact block by removing the one or more powder compacts of the plurality of support elements; further increasing the density of the one or more powder compacts of the usable model by applying a second cold isostatic press to the one or more powder compacts after the one or more powder compacts are removed from the green compact; and sintering the one or more powder compacts of the usable model to produce a plurality of three-dimensional models.

According to an aspect of some exemplary embodiments, there is provided a method of generating a plurality of three-dimensional models by additive manufacturing, the method comprising: constructing, in a layer-by-layer manner, a green compact using a powdered material and a solidified non-powdered material, the green compact including one or more powder compacts of a usable model and one or more powder compacts of a plurality of support elements, wherein the usable model and the support elements are defined by a plurality of pattern lines formed by selective deposition of the solidified non-powdered material; heating the green compact to remove the cured non-powder material; extracting one or more powder compacts of the usable model from the green compact block by removing the one or more powder compacts of the plurality of support elements; increasing the density of the one or more powder compacts of the usable model by applying a cold isostatic press to the one or more powder compacts after the one or more powder compacts are removed from the green compact; and sintering the one or more powder compacts of the usable model to produce a plurality of three-dimensional models.

According to an aspect of some exemplary embodiments, there is provided a method for increasing a density of a usable green model, the method comprising: inserting the green usable model with a cushioning material into a wet bag, optionally removing air from the wet bag, placing the wet bag into a cold isostatic chamber, and applying isostatic pressure to the wet bag to increase the density of the green usable model.

Optionally, the isostatic pressing is applied in two steps, wherein a first step comprises applying a first isostatic pressing sufficient to melt the buffer material and flow the buffer material within the plurality of hollow structures of the green usable model, and a second step comprises applying a second isostatic pressing to increase the density of the green usable model while the buffer material helps maintain the structural integrity of the green usable model.

Optionally, the buffer material is wax powder, the first isostatic pressure is up to 50 bar, the second isostatic pressure is up to 2600 bar.

According to an aspect of some exemplary embodiments, there is provided a system for generating a three-dimensional model by additive manufacturing, the system comprising: an additive manufacturing system comprising a print station, a powder dispensing station, a powder coating station, and a compaction station; an additional independent compaction station; and a sintering station.

Optionally, the additional independent compaction station is a cold isostatic pressing station.

Optionally, the powder dispensing station and the powder coating station are comprised in a single powder transfer station.

Unless defined otherwise, all technical and/or scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of embodiments of the present invention, exemplary methods and/or materials are described below. In case of conflict, the present specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting.

Drawings

Some embodiments of the invention herein are described, by way of example only, with reference to the accompanying drawings. With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of embodiments of the present invention. In this regard, the description taken with the drawings make apparent to those skilled in the art how the embodiments of the invention may be practiced.

In the drawings:

fig. 1 is a simplified schematic diagram of an exemplary additive manufacturing system according to some embodiments of the invention; and

FIG. 2 is a simplified schematic diagram of an exemplary per-layer build process (side view) according to some embodiments of the invention;

FIG. 3 is a simplified block diagram of an exemplary cyclical process for building multiple layers in accordance with some embodiments of the present invention; and

fig. 4A and 4B are simplified schematic diagrams of an exemplary compaction system in an undamped and compressed state (side view), respectively, according to some embodiments of the invention.

FIGS. 5A and 5B are simplified schematic diagrams of exemplary patterns formed in a layer to build an object (top view), according to some embodiments of the invention;

FIG. 6 is a simplified block diagram of a green compact including multiple compacted powder layers being processed in a cold isostatic pressing station according to some embodiments of the present invention;

FIG. 7 is a simplified flow diagram of an exemplary method for fabricating a three-dimensional model according to some embodiments of the invention;

FIG. 8 is a simplified block diagram of a powder compact of a usable mold being compacted in a cold isostatic pressing station according to some embodiments of the present invention;

FIG. 9 is a simplified diagram of example pressures applied during a cold isostatic pressing of a powder compact of a workable model, according to some embodiments of the invention;

FIG. 10 is a simplified flow diagram of another exemplary method for fabricating a three-dimensional model according to some embodiments of the invention; and

FIG. 11 is a simplified flow diagram of another exemplary method for fabricating a three-dimensional model according to some embodiments of the invention.

Detailed Description

In some embodiments, the present invention relates to the field of additive manufacturing, and more particularly, but not exclusively, to methods, apparatuses and systems for generating three-dimensional printed models with high material density.

As used herein, the terms "green body" and "powder compact" are interchangeable. Further, as used herein, "multiple available molded powder compacts" and "multiple green bodies" are interchangeable. The terms "object", "model" and "available model" are used interchangeably herein.

Additionally, as used herein, "powder compacts of support elements," "discrete portions of a support area," and "discrete portions" are interchangeable.

As used herein, the terms "green body", "powder compact", "moldable powder compacts", "green bodies", "powder compacts for support elements" refer to a "block", a "compact", "moldable compacts", "bodies", and "compacts for support elements", respectively, the main component of which is a binder material, typically in the form of a binder powder, prior to a sintering process.

Furthermore, the terms "mask", "pattern", "mask pattern", or "print pattern" are considered to refer to a pattern formed from a cured non-powder material, such as cured ink.

Some additive manufacturing processes produce a powder compact that includes multiple powder layers and a non-powder solidified material that is printed or deposited separately from the multiple powder layers. In some embodiments, the green compact may be produced by compacting a plurality of layers of powder, wherein for at least some of the compacted layers a solidified non-powder material has been deposited prior to compaction. The green compact typically includes a powder compact (also referred to as an "object") that can be molded, a powder compact of a support member, and a non-powder cured material, such as an ink that has been deposited by an inkjet print head, and cured after jetting (also referred to as "cured ink"). In some embodiments, the cured ink is deposited in a particular pattern to define the contours or shape of a mold and to separate its surface from the surface of the support element within other molds or blocks. In some embodiments, the solidified ink is selectively dispensed by a three-dimensional printer during the additive manufacturing process after compacting a previous layer of powder. The printed pattern may define a boundary, e.g., physical separation between the object and the material of the surrounding powder. The pattern may also divide the support area within the block into a plurality of discrete portions to facilitate removal of the support element when separating or removing the moldable powder compact from the block. During the additive manufacturing process, each layer may be compression molded to remove excess air from the layer. Optionally, the powder layer may reach a density of 85-90% of the processed density of the material forming the powder.

In some embodiments, the pattern is printed using a cured non-powder material, such as a cured ink. As referred to herein, a cured ink refers to an ink material that is solid at ambient temperature and liquid when printed. Non-limiting examples of cured inks include photo-cured inks, waxes, thermoset inks, and any combination thereof. As used herein, heat-set inks and phase-change inks are interchangeable terms and can be defined as materials that are solid at room temperature, have a melting point below 120 ℃, have a viscosity below 50cPs between the melting point temperature and 120 ℃, and evaporate at temperatures above 100 ℃ without carbon marking. Essentially, the absence of carbon marks can be defined as less than 5 wt% or 1 wt% of the cured ink. The thermoset ink has a melting temperature of 55-65 deg.C, a working temperature of about 65-75 deg.C, and a viscosity of 15-17 cPs. The thermoset ink is configured to evaporate in response to heating and has little or no carbon tracking.

According to some exemplary embodiments, the plurality of moldable powder compacts may be further post-processed, for example, the powder may be further compacted in one or more steps to remove excess air prior to sintering. The post-treatment process may include a Cold Isostatic Pressing (CIP) process, a pattern removal process (also commonly referred to as a "dewaxing process"), and a furnace sintering process. According to some exemplary embodiments, at the end of the green block building process, further compaction of the green block is achieved using a cold isostatic pressing station. The cold isostatic pressing station may be used to increase the density of a plurality of available molded powder compacts contained within a green block prior to sintering. In some example embodiments, the green body may optionally be wrapped in a fabric and sealed in a wet bag during cold isostatic pressing. Before sealing the wet bag, a vacuum may be applied to remove air from the wet bag. The cold isostatic press may be applied with a cured ink contained in the green block. In this manner, the density of the plurality of useful molded powder compacts included within a block may be increased from about 85-90% to about 90-95% of the processing density of the build material. Due to the presence of solidified non-powder material in the green compact, it is difficult to achieve a density above 95% of the process density of the build material because solidified non-powder material may be incompressible or less compressible than powder material.

According to some exemplary embodiments, at the end of the cold isostatic pressing, the green compact may be placed in a "dewaxing" station where the green compact may be heated to a temperature that causes the solidified non-powder material (e.g., solidified ink) to burn, liquefy, or evaporate (i.e., the dewaxing process). For example, temperatures in the range of about 100-1000 deg.C, 200-800 deg.C, 300-600 deg.C, or 350-500 deg.C may be applied. After removing the solidified non-powder material, the plurality of moldable powder compacts included in the green compact may be separated or removed from the green compact by removing the powder compacts of the plurality of support elements. A plurality of green usable models may then be sintered.

According to a further exemplary embodiment, a cold isostatic pressing process may be applied after the dewaxing process and before sintering to further increase the density of the plurality of green usable models after separating or removing the plurality of green usable models from the green compact mass. During such cold isostatic pressing, a plurality of green useful models may be inserted into a wet bag and may be packed or surrounded and/or filled with a material intended to cushion the plurality of models and maintain their structural integrity during the cold isostatic pressing. In some embodiments, the cushioning material may be a powder formed from a wax, such as paraffin. The air may be removed prior to sealing the wet bag. During cold isostatic pressing, the pressure may first be raised to a first level, e.g., a level at which the cushioning material will melt and begin to flow. The flow of the cushioning material may allow it to penetrate into a plurality of hollow portions, such as slits, channels, tubes or holes, included in the object, thereby fully supporting the geometry of the object (i.e., preventing its deformation) during the cold isostatic pressing. The viscosity of the buffer material may be selected so as to avoid a plurality of pores within the fill that may collapse during compaction. After a defined delay, the pressure may be further increased to a second level to compact a plurality of available green models. Optionally, the cold isostatic pressing process compacts the plurality of green bodies with the mold to remove substantially all air between the plurality of powder particles in the object, such that the material forming the object has a density of 100% of the processed density, or close to 100% of the density, such as 97% and above.

Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not necessarily limited in its application to the details of construction and to the arrangements of the components and/or methods set forth in the following description and/or illustrated in the drawings and/or examples. The invention is capable of other embodiments or of being practiced or carried out in various ways.

Referring now to fig. 1, a simplified block diagram of an exemplary additive manufacturing system is shown, according to some embodiments of the invention. According to some embodiments of the invention, an additive manufacturing system 100 includes a work platform 500 on which a build tray 200 is advanced through a plurality of stations to build a green compact, e.g., a plurality of powder layers 15, one layer at a time. Typically, a precision station 250 advances the build disk 200 to each station in a cyclic process. The plurality of stations may include a print station 30 for printing a pattern of a non-powder solidified material; a powder dispensing station 10 for dispensing a layer of powder; a powder coating station 20 for coating a layer of the dispensed powder; and a compaction station 40 for compacting the layer of powder and/or the printed pattern. Typically, for each layer, build tray 200 advances to each station, and the process is then repeated until all layers have been printed. According to some embodiments of the present invention, a controller 300 controls the operation of each station on a work platform 500 and coordinates the operation of each station by positioning and/or moving the disk 200 on the precision platform 250. Generally, the controller 300 includes and/or is associated with memory and processing capabilities. Alternatively, the powder dispensing station 10 and the powder coating station 20 are combined into a single powder delivery station.

According to some exemplary embodiments, the additive manufacturing system includes an additional compaction station 60, such as a cold isostatic pressing station. In some exemplary embodiments, after the layer building process is completed, the green compact blocks produced on the work platform 500 may be further compacted in an additional compaction station 60. Optionally, prior to compaction, the green compact is placed in a wet bag and air is evacuated from the wet bag. A wet bag is a flexible enclosure through which fluid does not pass, such as a rubber bag. In some exemplary embodiments, an additional compaction station 60 may be used to compact the green compact and to re-compact the powder compacts of the plurality of available models once removed from the green compact.

In some embodiments, furnace sintering may be applied after one or both cold isostatic pressing processes. The temperature and duration of sintering generally depend on the material of the powder used and, optionally, on the size of the object. Optionally, the sintering is performed in an inert gas environment. Optionally, the inert gas source 510 is a nitrogen gas source.

In some exemplary embodiments, the additive manufacturing systems described herein provide improved printing speeds. For example, the print time for each layer may be between 25-35 seconds, and an estimated build time for a green compact comprising 400 layers may be about 4 hours. The green compact 15 built on the build plate 200 may include a plurality of available green models, for example, 1-15 models. An exemplary occupied area of a block may be 20 × 20 cm.

The sintering station 70 and the additional compaction station 60 may be separate stations from the work platform 500. Alternatively, the green compact block 15 is manually positioned into the additional compaction station 60 and then into the sintering station 70, and not through the precision station 250. Optionally, each additional compacting station 60 and sintering station 70 has a separate controller for operating the respective station.

Reference is now made to FIG. 2, which illustrates a simplified schematic diagram of an exemplary per-layer build process, according to some embodiments of the invention. Fig. 2 illustrates the process of building an exemplary third layer 506 over an exemplary first layer 502 and second layer 504. In some exemplary embodiments, a three-dimensional printer is utilized to assign a pattern 510 per layer. According to some exemplary embodiments, the pattern 510 is formed from a cured non-powder material, such as a cured ink. The pattern 510 may physically contact a pattern 510 in a previous layer or layers, such as layers 504 and 502, for example, or may be patterned over an area of a previous layer of material that includes powder. A height of the pattern 510 of each layer may be the same as a height of the layer, or alternatively, may be shorter than the height of the layer, e.g., portion 510A of pattern 510 in layer 504.

According to some examples, powder 51 is coated on pattern 510 and over an occupied area of a build disk 200. In some exemplary embodiments, the powder 51 is coated by a roller 25. Optionally, rollers 25 are actuated to both rotate about their axes 24 and move along an X-axis over build disk 200. Once the powder 51 is coated on the footprint of the pan 200, compaction 520 may be applied across the entire layer to compact the layer 506. Generally, a height of layer 506 is reduced due to the compaction process, and optionally, previous layers 502 and 504.

Referring now to fig. 3, a simplified block diagram of an exemplary cyclic process for building layers of green blocks is shown, according to some embodiments of the invention. According to some exemplary embodiments, an object (i.e., a powder compact of a usable model) may be built layer by layer within a green compact in a cyclic process. Each cycle of the cyclic process may comprise the steps of: printing a pattern at a print station 30 (block 250), dispensing (block 260) and coating (block 270) a powder of material over the pattern at a dispensing station 10 and a coating station 20, and compacting the powder layer including the pattern at a compaction station 40 (block 280). In some embodiments, the dispensing and coating stations 10 and 20 are combined into a single station, also referred to as a "powder transfer station". In some exemplary embodiments, the pattern is formed from a cured non-powder material, such as a cured ink. Compaction may include embossing of each layer. According to various embodiments of the present invention, one layer of green blocks is formed per cycle, and the cycle is repeated until all layers have been built. Alternatively, a pattern may not be required for one or more layers, and the step of printing the pattern may be excluded from a selected plurality of layers (block 250). Alternatively, one or more layers may not require powdered material, and the step of dispensing and coating a powdered material may be eliminated from selected layers (blocks 260 and 270). The cyclical process produces a green compact that includes one or more powder compacts of the plurality of available models, one or more powder compacts of the plurality of support members, and a solidified non-powder material.

Reference is now made to fig. 4A and 4B, which illustrate a simplified schematic diagram of an exemplary molding station in an relaxed and compressed state, respectively, according to some embodiments of the invention. A compaction station 40 may include a piston 42, with the piston 42 providing compaction pressure to compact a layer 300. During compaction, the piston 42 may be raised through an aperture 49 and optionally push the rod 42A into the work platform 500 or precision platform 250 and lift the build disk 200 toward a surface 45 above the disk 200. The rod 42A may function to reduce the distance required for the piston 42 to move to effect compaction.

Optionally, once layer 300 is in contact with surface 45, walls 43 close around layer 300 to maintain a constant footprint of layer 300 during compaction.

Build plate 200 may be secured to one or more linear rails 41 that travel along linear bearings 46 as piston 42 raises and/or lowers plate 200. Optionally, the disc 200 is lifted against one or more compression springs 47. Gravity and a plurality of springs 47 may provide the function of lowering the piston 42 after the layer 300 is compacted.

Pressures of up to 250 or 300 million pascals (MPa) may be applied to compact a layer. Typically, the applied pressure is used to remove air and force the powder in the layer 300 beyond its elastic state, thereby effecting permanent deformation of the layer. Optionally, the compacting provides increasing the relative density of the layer to a processed density of about 70% to 75% of the material of the powder. For several alloys, the relative density may reach a 90% work density. Alternatively, the compaction may reduce the thickness of the layer by up to 25%. Optionally, a compaction pressure of about 30-90 mpa is applied. Optionally, the compaction is performed at room temperature.

In some embodiments, the upper surface 45 may be heated, for example, preheated during compaction using a heating element 44. When surface 45 is heated, layer 300 may reach its plastic and/or permanent deformation state with little pressure exerted thereon. Alternatively, in the case of aluminum powder, upper surface 45 is heated to a temperature of 150 ℃, for example 150 ℃ to 200 ℃. There is often a trade-off between compaction temperature and pressure. Increasing the temperature during compaction may provide the objective of achieving plastic deformation at lower pressures. On the other hand, lowering the temperature of upper surface 45 reduces the energy efficiency of the compaction, as higher pressures may be required.

Reference is now made to fig. 5A and 5B, which are simplified pictorial diagrams illustrating exemplary patterns formed in a layer for building a three-dimensional object, in accordance with some embodiments of the present invention. According to exemplary embodiments, a solidified non-powder material, such as solidified ink, delineates an outline 150 of an object 750, and also divides the support region into portions that are easily separated from object 750 at the end of the green block building process by a plurality of patterning lines 155. Some of the support areas are divided into a plurality of large support portions 710. The other support areas may be divided into a plurality of smaller support portions 720 (fig. 5A), the plurality of smaller support portions 720 taking into account a geometry of object 750 more carefully and facilitating separation of the plurality of support portions 720 from object 750 at the end of the green block building process. In some exemplary embodiments, the plurality of support portions 720 may be defined to provide a desired draft angle to facilitate removal of the object 750 from the green block. The size and shape of the plurality of support portions 720 may be defined to facilitate removal of the object from the green block. A plurality of smaller support sections 720 may be defined near a surface of object 750 and a plurality of larger support sections 710 may be defined away from the surface of object 750.

Referring now to fig. 5B, a negative mask may be applied in a defined support region where it may be difficult to remove a plurality of entirely cured support portions, e.g., within a plurality of cavities defined by object 750. The negative mask creates a support portion 730, which support portion 730 will remain in a powder state after removal of the curable non-powder material and thus is easily removed from the cavity (i.e., as opposed to other multiple support regions that cure into multiple discrete portions during processing). According to some exemplary embodiments, the negative mask is formed by dithering a curable non-powder material in a defined region 730. The degree of jitter may be between 5-50% or 5-100% of the solidified non-powder material in the layer. Typically, a separator of cured non-powder material separates the negative mask from the object. Some portions of a layer may be patterned using a negative mask while other portions may include a pattern that divides the support region into a plurality of discrete portions 710. Curable non-powder materials may also be included in multiple regions of a layer to provide structural support to the green compact.

Referring now to fig. 6, a simplified block diagram of a green compact according to some embodiments of the invention includes a compacted powdered material, optionally including a solidified non-powdered material (e.g., solidified ink), in a cold isostatic pressing station. According to some exemplary embodiments, the additional compaction station 60 is a cold isostatic pressing station comprising a cold isostatic pressing chamber 650, wherein an object may be compacted 630 by applying a substantially uniform pressure around the object placed in a wet bag 620 using a fluid 615 contained in the chamber 650, wherein the fluid 615 is contained. At 650 chamber in some exemplary embodiments, a green compact 600 constructed by an additive manufacturing method is compacted in a chamber of a compaction station 60. The green compact 600 may include a powdered material and a non-solidified non-powdered material, such as: a cured ink. During compaction, the green compact 600 is inserted into the wet bag 620. Optionally, air is drawn from the volume of the wet bag 620 under a vacuum. The wet bag 620 including the green compact 600 may then be compacted by cold isostatic pressing. The cold isostatic pressing may maintain the proportions of the green compact 600 and the available mold(s) embedded therein during compaction. The cold isostatic pressing may be carried out at a pressure of up to about 2500 bar, optionally also at a temperature of up to 40 ℃. In some exemplary embodiments, the green block 600 is wrapped with a fabric prior to insertion into the wet pouch.

Referring now to FIG. 7, a simplified flow diagram of an exemplary method for fabricating a three-dimensional model is shown, according to some embodiments of the invention. A layer build process may be performed to build a green compact of powder-containing material and solidified non-powder material (e.g., a solidified ink), wherein one or more powder compacts of the plurality of workable models and one or more powder compacts of the plurality of support elements are defined by a solidified non-powder material (block 905). At the end of the build process, cold isostatic pressing may be applied to the green block to provide additional compaction (block 910). During cold isostatic pressing, an isostatic pressure may be applied through a liquid surrounding the block, as opposed to the unidirectional pressure applied to each layer during the layer building process. Upon termination of the cold isostatic pressing, the green compact may be heated to melt, burn, or evaporate the non-powder solidified material contained therein (block 915). Once the solidified non-powder material is removed, the green usable model(s) may be separated from the plurality of green support elements (block 920) and the green usable model(s) may be sintered (block 925).

Reference is now made to fig. 8, which illustrates a simplified block diagram of a green compact model being compacted in a cold isostatic pressing station, and fig. 9 illustrates a simplified diagram of exemplary pressures applied during the cold isostatic pressing process, according to some embodiments of the present invention. Optionally, the cold isostatic pressing process is intended to further compact the green model prior to sintering and is performed after a first cold isostatic pressing is applied to a green block comprising the green model and the green model is removed from the block. Optionally, during the cold isostatic pressing, substantially all air in the powder, e.g., used to build the green usable model, may be removed, e.g., resulting in a 100% processing density (or at least 97% or 98%) of the material of the powder used to build the object. During the cold isostatic pressing process, the green form may be inserted into a wet bag 620 with a cushioning material 640 (e.g., a wax powder). Air may be removed from the wet bag 620. The cold isostatic pressing process may be performed in two steps. In a first stage, the wet pocket 620 may be pressurized, for example, to a first pressure level 680 (fig. 9), for example, 50 bar, at which first pressure level 680 the cushioning material 640 in the wet pocket 620 may melt. Once the cushioning material 640 melts, it may flow into any hollow structures (e.g., channels, crevices) defined by the object geometry to help maintain the structural integrity of the mold during compaction. Alternatively, heat may be applied to melt the cushioning material. Once the buffer material melts and diffuses into the plurality of hollow structures, a second stage of the cold isostatic pressing process may be performed. In some exemplary embodiments, during the second stage, additional pressure (690) is applied for a defined duration to compact the green model 750. Alternatively, pressures up to 2600 bar may be applied. After the pressure 690 is released, the green model may be removed from the wet bag 620 and sintered. In some embodiments, the first pressure level 680 is applied during a time window of 1 to 60 minutes, 2 to 30 minutes, or 5 to 15 minutes. If a buffer material in the form of a powder, such as a wax powder, is used and the powder is melted by heating, the delay time to full pressure application can be shortened and can last for as long as 1 minute.

Reference is now made to FIG. 10, which is a simplified flowchart illustration of another exemplary method for fabricating a three-dimensional model, according to some embodiments of the invention. A layer building process may be performed to build a green body that includes a powder material and a non-powder material (e.g., a cured ink), wherein one or more of the plurality of moldable powder compacts and one or more of the plurality of support members are defined by a cured non-powder material (block 905). At the end of the build process, a cold isostatic press may be applied on the green compact to provide additional compaction (block 910). During cold isostatic pressing, the density of the build material forming the object may reach a processing density of about 85-90% to about 90-97% of the material. Upon termination of the cold isostatic pressing, the green body may be heated to a temperature at which the non-powder solidified material melts, combusts, or evaporates (block 915). Once the solidified material is removed, the one or more green models may be separated from the plurality of green support elements (block 920). The removed green models may then be compacted again in a second cold isostatic pressing process (block 922). During the second cold isostatic pressing process, the plurality of forms may be packed or surrounded and/or filled with a cushioning material to help maintain the structural integrity of the plurality of forms. In some embodiments, the cushioning material may be a powder formed from a wax, such as paraffin. The second cold isostatic pressing process may include applying a first pressure level at which the buffer material melts, and then applying a second pressure level at which the plurality of green molds are compacted to achieve a processing density of the material of the powder of approximately 100%. Alternatively, a continuous incremental pressure may be applied. After the second cold isostatic pressing process, the plurality of green models may be sintered to form a final plurality of three-dimensional models (block 925).

Reference is now made to FIG. 11, which is a simplified flowchart illustration of a method for fabricating another example of a three-dimensional printing model according to some embodiments of the present invention. A layer build process may be performed to build green bodies comprising a powder material and a non-powder cured material (e.g., a cured ink), wherein one or more moldable powder compacts and one or more support element powder compacts are defined by a cured non-powder material (block 905). At the end of the layer building process, the green body may be heated to a temperature at which the non-powder solidified material melts, burns, or evaporates (block 915). Once the non-powdered solidified material is removed, the one or more powder compacts of the plurality of molds may be separated from the plurality of support elements (block 920). The removed forms may then be compacted in a cold isostatic process (block 922), wherein the removed forms are packed or surrounded and/or filled with a cushioning material to help maintain the structural integrity of the forms. In some embodiments, the cushioning material may be a powder formed from a wax, such as paraffin. The cold isostatic pressing process may include applying a first pressure level at which the buffer material melts, and then applying a second pressure level at which the plurality of patterns are further compacted to achieve a processing density of approximately 100% of the material. Alternatively, a continuous incremental pressure may be applied. After the cold isostatic pressing process, the plurality of green models may be sintered to form a final plurality of three-dimensional models (block 925).

The terms "comprising", "including", "having" and variations thereof mean "including but not limited to".

The term "consisting of means" including and limited to ". .

The term "consisting essentially of" means that the composition, method, or composition may include additional ingredients and/or steps, but only if the additional ingredients and/or steps do not materially alter the basic and novel characteristics of the claimed composition or method.

It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination or in any other described embodiment suitable for the invention. The particular features described herein in the context of the various embodiments are not considered essential features of those embodiments, unless the embodiment is inoperative without those elements.

Claims (20)

1. A method of generating a three-dimensional model by additive manufacturing, the method comprising: constructing a green compact block in a layer-by-layer manner using a powdered material and a solidified non-powdered material, the green compact block including a green usable model, and one or more green support elements; removing the solidified non-powder material and the one or more green support elements from the green block to extract the green usable model from the green block; increasing the density of the green usable model by applying cold isostatic pressing; and sintering the green usable model after removing the one or more green support elements from the green block to produce a three-dimensional model.

2. The method of claim 1, wherein: applying the cold isostatic press to the green block, the green block comprising the green usable model.

3. The method of claim 1, wherein: after removing the green usable model from the green block, the cold isostatic press is applied to the green usable model.

4. The method of claim 1, wherein: applying a first cold isostatic press to the green block, the green block including the green usable model, and applying a second cold isostatic press to the green usable model after the green usable model is separated from the green block.

5. The method of claim 1, wherein: the green usable model is a powder compact of a usable model.

6. The method of any of claims 1 to 5, wherein: the step of building the green compact in the layer-by-layer manner is performed by an additive manufacturing system configured to build a layer by: (1) printing a pattern using a cured non-powder material to trace the contours of the green usable model; (2) dispensing and coating a powdered material over the pattern; and (3) compacting the powder layer using the pattern.

7. The method of any of claims 1 to 5, wherein: the powder material is selected from the group consisting of an alloy powder, a pure metal powder, a ceramic powder, a polymer powder, and any combination or mixture thereof.

8. The method of claim 7, wherein: the material of the powder is an aluminum alloy.

9. The method of any of claims 1 to 5, wherein: the cured non-powder material is a cured ink selected from the group consisting of a plurality of photo-curable inks, a wax, a plurality of thermosetting inks, and any combination thereof.

10. The method of claim 1, wherein: the step of removing the solidified non-powder material from the green compact is performed by heating the green compact to melt, burn or evaporate the solidified non-powder material.

11. The method of claim 2 or 4, wherein: applying the cold isostatic press to the green compact includes inserting the green compact into a wet bag, placing the wet bag into a cold isostatic press chamber, and applying an isostatic press to the wet bag containing the green compact.

12. The method of claim 11, wherein: removing air from the wet bag.

13. The method of claim 11, wherein: the isostatic pressure is up to 2500 bar.

14. The method of claim 3 or 4, wherein: applying a cold isostatic press to the green usable model after the green usable model is removed from the green block comprises inserting the green usable model with a buffer material into a wet bag, optionally removing air from the wet bag, placing the wet bag into a cold isostatic press chamber, and applying an isostatic press to the wet bag, the wet bag comprising the green usable model.

15. The method of claim 14, wherein: the isostatic pressing is applied in two steps, wherein the first step comprises applying a first isostatic pressing sufficient to melt the buffer material to flow the buffer material within the hollow structure of the green usable model, and the second step comprises applying a second isostatic pressing to compact the green usable model.

16. The method of claim 15, wherein: the buffer material is a wax powder, the first isostatic pressure being up to 50 bar, and the second isostatic pressure being up to 2600 bar.

17. The method of any of claims 1 to 5, wherein: one temperature applied during cold isostatic pressing was 40 ℃.

18. A method of generating a plurality of three-dimensional models by additive manufacturing, the method comprising: constructing, in a layer-by-layer manner, a green compact using a powdered material and a solidified non-powdered material, the green compact including one or more powder compacts of a usable model and one or more powder compacts of a plurality of support elements, wherein the usable model and the plurality of support elements are defined by a plurality of pattern lines formed by selective deposition of the solidified non-powdered material;

increasing the density of one or more powder compacts of the usable model by applying a cold isostatic press to the green compact;

heating the green block to remove the solidified non-powder material;

extracting one or more powder compacts of the usable mold from the green compact by removing the one or more powder compacts of the plurality of support elements; and

after removing the one or more powder compacts of the plurality of support elements, sintering the one or more powder compacts of the usable model to create a plurality of three-dimensional models.

19. A method of generating a plurality of three-dimensional models by additive manufacturing, the method comprising: constructing, in a layer-by-layer manner, a green compact using a powdered material and a solidified non-powdered material, the green compact including one or more powder compacts of a usable model and one or more powder compacts of a plurality of support elements, wherein the usable model and the plurality of support elements are defined by a plurality of pattern lines formed by selective deposition of the solidified non-powdered material;

increasing the density of one or more powder compacts of the usable mold by applying a first cold isostatic press to the green compact;

heating the green block to remove the solidified non-powder material;

extracting one or more powder compacts of the usable model from the green compact block by removing the one or more powder compacts of the plurality of support elements;

further increasing the density of the one or more powder compacts of the usable model by applying a second cold isostatic press to the one or more powder compacts after the one or more powder compacts are removed from the green compact; and

after removing the one or more powder compacts of the plurality of support elements, sintering the one or more powder compacts of the usable model to create a plurality of three-dimensional models.

20. A method of generating a plurality of three-dimensional models by additive manufacturing, the method comprising: constructing a green compact in a layer-by-layer manner using a powdered material and a solidified non-powdered material, the green compact including one or more powder compacts of a usable mold and one or more powder compacts of a plurality of support elements, wherein the usable mold and the plurality of support elements are defined by a plurality of pattern lines formed by selectively depositing the solidified non-powdered material;

heating the green block to remove the solidified non-powder material;

extracting one or more powder compacts of the usable model from the green compact block by removing the one or more powder compacts of the plurality of support elements;

increasing the density of the one or more powder compacts of the usable model by applying a cold isostatic press to the one or more powder compacts after the one or more powder compacts are removed from the green compact; and

after removing the one or more powder compacts of the plurality of support elements, sintering the one or more powder compacts of the usable model to create a plurality of three-dimensional models.