WO2021160338A1 - Procédé et dispositif pour éliminer un excès de poudre d'éléments produits par fabrication additive - Google Patents

Procédé et dispositif pour éliminer un excès de poudre d'éléments produits par fabrication additive Download PDF

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Publication number
WO2021160338A1
WO2021160338A1 PCT/EP2021/025015 EP2021025015W WO2021160338A1 WO 2021160338 A1 WO2021160338 A1 WO 2021160338A1 EP 2021025015 W EP2021025015 W EP 2021025015W WO 2021160338 A1 WO2021160338 A1 WO 2021160338A1
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WIPO (PCT)
Prior art keywords
powder
component
cake
melting
cryogen
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PCT/EP2021/025015
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English (en)
Inventor
Bartek KAPLAN
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Linde Gmbh
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Publication of WO2021160338A1 publication Critical patent/WO2021160338A1/fr

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
    • B22F10/60—Treatment of workpieces or articles after build-up
    • B22F10/66—Treatment of workpieces or articles after build-up by mechanical means
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
    • B22F10/20—Direct sintering or melting
    • B22F10/28—Powder bed fusion, e.g. selective laser melting [SLM] or electron beam melting [EBM]
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
    • B22F10/60—Treatment of workpieces or articles after build-up
    • B22F10/68—Cleaning or washing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
    • B22F10/70—Recycling
    • B22F10/73—Recycling of powder
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F12/00—Apparatus or devices specially adapted for additive manufacturing; Auxiliary means for additive manufacturing; Combinations of additive manufacturing apparatus or devices with other processing apparatus or devices
    • B22F12/70—Gas flow means
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C64/00—Additive manufacturing, i.e. manufacturing of three-dimensional [3D] objects by additive deposition, additive agglomeration or additive layering, e.g. by 3D printing, stereolithography or selective laser sintering
    • B29C64/30—Auxiliary operations or equipment
    • B29C64/35—Cleaning
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y10/00—Processes of additive manufacturing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y40/00—Auxiliary operations or equipment, e.g. for material handling
    • B33Y40/20—Post-treatment, e.g. curing, coating or polishing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
    • B22F10/30—Process control
    • B22F10/36—Process control of energy beam parameters
    • B22F10/362—Process control of energy beam parameters for preheating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F12/00—Apparatus or devices specially adapted for additive manufacturing; Auxiliary means for additive manufacturing; Combinations of additive manufacturing apparatus or devices with other processing apparatus or devices
    • B22F12/40—Radiation means
    • B22F12/41—Radiation means characterised by the type, e.g. laser or electron beam
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F2202/00—Treatment under specific physical conditions
    • B22F2202/03—Treatment under cryogenic or supercritical conditions
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy
    • B22F2998/10—Processes characterised by the sequence of their steps
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F2999/00—Aspects linked to processes or compositions used in powder metallurgy
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24C—ABRASIVE OR RELATED BLASTING WITH PARTICULATE MATERIAL
    • B24C1/00—Methods for use of abrasive blasting for producing particular effects; Use of auxiliary equipment in connection with such methods
    • B24C1/003—Methods for use of abrasive blasting for producing particular effects; Use of auxiliary equipment in connection with such methods using material which dissolves or changes phase after the treatment, e.g. ice, CO2
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24C—ABRASIVE OR RELATED BLASTING WITH PARTICULATE MATERIAL
    • B24C11/00—Selection of abrasive materials or additives for abrasive blasts
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/25—Process efficiency

Definitions

  • the present invention relates to a method and a device for removing excess powder from components produced by additive manufacturing (AM), particularly, but not exclusively, products made by electron beam melting (EBM).
  • AM additive manufacturing
  • EBM electron beam melting
  • A additive manufacturing
  • Some methods melt or soften the material to produce the layers, for example selective laser melting (SLM) or direct metal laser sintering (DMLS), selective laser sintering (SLS), fused deposition modeling (FDM), or fused filament fabrication (FFF), while others cure liquid materials using different sophisticated technologies.
  • SLM selective laser melting
  • DMLS direct metal laser sintering
  • SLS selective laser sintering
  • FDM fused deposition modeling
  • FFF fused filament fabrication
  • Selective laser sintering is an additive manufacturing (AM) technique that uses a laser as the power source to sinter powdered material, aiming the laser automatically at points in space defined by a 3D model, binding the material together to create a solid structure. It is similar to direct metal laser sintering (DMLS). Both are instantiations of the same concept but differ in technical details.
  • Selective laser melting uses a comparable concept, but in SLM the material is fully melted rather than sintered, allowing different properties (crystal structure, porosity, and so on).
  • SLS involves the use of a high power laser (for example, a carbon dioxide laser) to fuse small particles of plastic, metal, ceramic, or glass powders into a mass that has a desired three- dimensional shape.
  • the laser selectively fuses powdered material by scanning cross- sections generated from a 3-D digital description of the part (for example from a CAD file or scan data) on the surface of a powder bed. After each cross-section is scanned, the powder bed is lowered by one layer thickness, a new layer of material is applied on top, and the process is repeated until the part is completed. Because finished part density depends on peak laser power, rather than laser duration, a SLS machine typically uses a pulsed laser.
  • SLM Selective laser melting
  • AM Additive Manufacturing
  • each 2D slice of the part geometry is fused by selectively melting the powder. This is accomplished with a high-power laser beam, usually an ytterbium fiber laser with hundreds of watts. The laser beam is directed in the X and Y directions with two high frequency scanning mirrors. The laser energy is intense enough to permit full melting (welding) of the particles to form solid metal. The process is repeated layer after layer until the part is complete.
  • a high-power laser beam usually an ytterbium fiber laser with hundreds of watts.
  • the laser beam is directed in the X and Y directions with two high frequency scanning mirrors.
  • the laser energy is intense enough to permit full melting (welding) of the particles to form solid metal.
  • the process is repeated layer after layer until the part is complete.
  • Electron-beam additive manufacturing or electron-beam melting is a type of additive manufacturing, or 3D printing, for metal parts.
  • the raw material metal powder or wire
  • This technique is distinct from selective laser sintering as the raw material fuses having completely melted.
  • Metal powders can be consolidated into a solid mass using an electron beam as the heat source. Parts are manufactured by melting metal powder, layer by layer, with an electron beam in a high vacuum. This powder bed method produces fully dense metal parts directly from metal powder with characteristics of the target material.
  • the EBM machine reads data from a 3D CAD model and lays down successive layers of powdered material. These layers are melted together utilizing a computer-controlled electron beam. In this way it builds up the parts.
  • the process takes place under vacuum, which makes it suited to manufacture parts in reactive materials with a high affinity for oxygen, e.g. titanium.
  • the process is known to operate at higher temperatures (up to 1000 °C), which can lead to differences in the final microstructure compared to SLM due to the very different thermal history compared to materials processed by EBM.
  • the powder feedstock is typically pre-alloyed, as opposed to a mixture. That aspect allows classification of EBM with selective laser melting (SLM), where competing technologies like SLS and DMLS require thermal treatment after fabrication. Compared to SLM and DMLS, EBM has a generally superior build rate because of its higher energy density and scanning method.
  • SLM selective laser melting
  • Direct metal laser sintering is an additive manufacturing metal fabrication technology, occasionally referred to as selective laser sintering (SLS) or selective laser melting (SLM), that generates metal prototypes and tools directly from computer aided design (CAD) data. It is unique from SLS or SLM because the process uses a laser to selectively fuse a fine metal powder, whereas SLS or SLM can also be used with non- metals.
  • SLS or SLM uses a variety of alloys, allowing prototypes to be functional hardware made out of the same material as production components. Since the components are built layer by layer, it is possible to design organic geometries, internal features and challenging passages that could not be cast or otherwise machined. DMLS produces strong, durable metal parts that work well as both functional prototypes or end-use production parts.
  • the DMLS process begins with a 3D CAD model whereby a .stl file is created and sent to the machine’s computer program.
  • the DMLS machine uses a high- powered 200 watt Yb-fiber optic laser. Inside the build chamber area, there is a material dispensing platform and a built platform along with a recoater blade used to move new powder over the built platform.
  • the technology fuses metal powder into a solid part by melting it locally using the focused laser beam. Parts are built up additively layer by layer, typically using layers 20 micrometers thick.
  • additive manufacturing is a manufacturing technology that includes a methodology whereby a heat source melts a feedstock of material which is deposited onto a substrate.
  • Computer control of the movement of the heat source, and the source of the feedstock, makes it possible to build complex components.
  • the processing is not limited to the above-mentioned methods in which metal powders are processed but composites or polymers are processed.
  • the heat source can include (but is not limited to) the already mentioned laser beam or electron beam, an arc, or other plasma-based heat sources. All the techniques for additive manufacturing discussed above provide the possibility for producing parts of very complex geometries, including but not limited to hollow features such as channels and 3D honeycomb (or any other mesh type) structures.
  • EBM is typically performed on a powder bed, and selected parts are fused using the electron beam, which typically fully melts the powder in the track of the beam.
  • the powder bed is typically maintained at a high temperature (up to 1000°C), and under vacuum.
  • the conditions in the powder bed during an EBM process are often sufficient to cause light sintering of the powder particles that are not intended to be fused together. Accordingly, once an EBM process has been completed, the component is typically surrounded by a “cake” of lightly sintered powder. It is therefore necessary to remove the cake of sintered powder from the component.
  • An explosion of particles suspended in air may be referred to as a “dust explosion”.
  • the minimum ignition energy depends on various factors, including the temperature at which the blasting takes place and the size of the particles, as well as the availability of reactive gaseous species, e.g., oxygen.
  • the minimum ignition energy is lower for powders including smaller particles, so the risk of a dust explosion is higher for components that are made using powders that include particles of small size. Indeed, the risk of a dust explosion occurring during the blasting process has so far prevented parts from being made by EBM from powders having particle sizes below 45 pm.
  • other methods for metal additive manufacturing such as SLM, may utilize powder sizes down to 15 pm.
  • a method for removing a cake of powder from a component made by an additive manufacture process comprising applying a flow of pressurized gas to the component, wherein a plurality of particles of a solid cryogen are included in the flow of pressurized gas.
  • this method allows a cake of powder to be removed without the risk of a dust explosion occurring. This may enable parts to be made using finer powders, because with prior art methods of removing a cake of powder the risk of a dust explosion was increased for finer powders. Furthermore, the use of a solid cryogen may reduce or completely remove the risk for trapping powder particles into hollow geometrical features of the additively manufactured component.
  • the solid cryogen comprises solid CO2.
  • the diameter of the solid C02 particles is preferably between 1 micrometer up to 10 millimeters.
  • the solid C02 could be C02 snow, preferably with a diameter between 1 micrometer and 100 micrometer, or C02 micro pellets, preferably with a diameter between 100 micrometer and 3 mm, and/or C02 pellets with a diameter of more than 3 mm.
  • the flow of pressurized gas comprises a mixture of solid cryogen and abrasive particles.
  • the abrasives could for example be sodium bicarbonate or sodium hydrogen carbonate, corund, calcium carbonate, or nutshells broken into smaller particles. Such abrasives are particularly used together with solid C02 particles.
  • the pressurized gas comprises pressurized air.
  • the use of solid CO2 for blasting will remove one of the three fundamental necessities for the dust explosion, i.e., the generated heat from friction (the other two being fuel, i.e., the powder particles, and ambient oxygen). Measures must be taken remove the risk of charge buildup between nozzle and blasting chamber (i.e., the nozzle must be grounded).
  • the pressurized gas comprises inert gas.
  • inert gas Apart from being one of the three main risks for dust explosion (fuel, heat and oxygen are required for ignition), pressurized air installations will rarely reach the very dry conditions of industrial or laboratory gases. Humidity is known to cause surface oxidation and/or formation of hydroxides, which may affect the additive manufacturing process adversely. Use of a dry inert gas may additionally prevent the risk for a dust explosion as well as unintentional surface oxidation originating from moisture.
  • a method for producing a component comprising the steps of: providing a metal powder on a build platform, melting a portion of the metal powder with a heat source, and repeating the aforementioned steps, wherein the metal powder is heated to a temperature below its melting point prior to the step of melting the portion of the metal powder, such that a cake of powder is formed on an outer surface of the component, characterized in that the method comprises the subsequent step of removing the cake of powder by a method as described above.
  • the component is produced by electron beam melting (EBM).
  • EBM electron beam melting
  • a cake of powder is particularly likely to form around components made by EBM, because EBM processes usually take place with the whole powder bed at elevated temperature.
  • the temperature of the powder bed during an EBM process may be up to 1100 degrees C using state-of-the art equipment.
  • the powder bed temperature must be selected depending on the alloy being printed so that the melting point is never reached in the complete powder bed.
  • the invention is also applicable to remove a cake of powder in an additive manufacturing process where the component is produced by selective laser sintering (SLS) or selective laser melting (SLM).
  • SLS selective laser sintering
  • SLM selective laser melting
  • a system for generating a three-dimensional component comprising: a device for additive manufacturing comprising: a powder delivery system comprising a storage cylinder for metal powder and an application device for applying the powder onto a built platform; a heat source; and a built platform, the system further comprising a device for cryogenic blasting comprising: a source of cryogen; a source of compressed gas; and a nozzle arranged to direct a flow of the compressed gas towards the component, wherein the flow of compressed gas includes solid particles of the cryogen, thereby to remove a cake of powder from an outer surface of the component.
  • the device for additive manufacturing is a device for electron beam melting (EBM), and wherein the heat source comprises an electron beam.
  • EBM electron beam melting
  • the inventive system is used for additive manufacturing comprising a laser as heat source.
  • a laser as heat source.
  • such an additive manufacturing process could be selective laser sintering or selective laser melting.
  • the cryogen comprises CO2.
  • the pressurized gas comprises pressurized air.
  • the pressurized gas comprises a chemically inert gas, for example nitrogen or argon.
  • FIG 1 a rough schematic view of a system for powder bed additive manufacturing by Electron Beam Melting (EBM)
  • Figure 2 a rough schematic view of a cryogenic blasting system
  • Figure 3 a rough schematic view of a device for blasting a cake of powder off a component made by additive manufacture according to an embodiment of the present invention.
  • FIG 1 shows an apparatus for additive manufacturing 1 according to an embodiment of the present invention. It is clear that the present invention is applicable for all methods and devices for additive manufacturing disclosed in this description.
  • the apparatus 1 comprises a production cylinder 2, a delivery cylinder 3 and a heat source 4.
  • the heat source 4 comprises an electron beam and a corresponding scanner system for melting metal powder (not shown).
  • a corresponding scanner system for melting metal powder not shown.
  • other heat sources such as a laser in combination with a scanning system, are also possible.
  • the delivery cylinder 3 comprises a housing 5 with a wall 6 wherein a powder delivery piston 7 is disposed inside the housing 5.
  • a powder applying device 8 for example a roller, is provided for pushing a metal powder from the delivery cylinder 3 to the production cylinder 2.
  • the production cylinder 3 comprises a housing 9 with a wall 10.
  • a lift table 11 with a build platform 12 is disposed inside the wall 10 of the housing 9.
  • the lift table 11 and the corresponding built platform 12 embody a fabrication piston.
  • the wall 10 of the housing 9 and the built platform 12 of the lift table 11 of the production cylinder 2 define a built space 13.
  • the built space 13 houses the fabrication powder bed and therefore the object being fabricated.
  • the built platform 12 can be an integral part of the lift table 11 of the fabrication piston or a separate part connected to the lift table 11.
  • a processing chamber 17 is provided surrounding the production cylinder 2, the delivery cylinder 3 and the heat source 4.
  • the manufacturing space 20 is therefore the build space 13 of the production cylinder 2 defined by the 10 wall of the housing 9 of the production cylinder 2 and the lift table 11 with the built platform 12 disposed inside the wall 10 of the housing 9, and/or the manufacturing space is the room within the processing chamber 17.
  • the apparatus 1 may be used to produce parts by Electron Beam Melting (EBM) in the conventional way.
  • EBM Electron Beam Melting
  • the electron beam 4 may be controlled to heat the platform 12 and a first layer of powder to a predetermined temperature at which the process is to take place. This temperature must be below the melting point of the powder but is high enough to cause light sintering of the powder.
  • the predetermined temperature may be as high as 1000°C or more.
  • the scanner system controls the electron beam 4 to further heat selected portions of the first layer of powder so as to melt these portions.
  • a further layer of powder is then applied on top of the powder bed, and the electron beam is then controlled to first heat the further layer of powder to the predetermined temperature, and then to further heat selected regions so as to melt the selected regions.
  • the process is repeated until all of the parts of the component that are required to be fused have been melted by the electron beam 4. At this point, formation of the part is complete.
  • the melting process occurs in a gaseous atmosphere under “controlled vacuum” conditions.
  • the process may take place in a Helium atmosphere at a pressure that is preferably in the range of 1x10 3 mbar and 5x10 -3 mbar.
  • Helium is chosen as a process gas as it can prevent electron beam electron expansion.
  • the component will typically be surrounded by a “cake” of powder that is at least partially sintered together.
  • This sintering happens as a result of the high temperature at which the EBM process takes place, and helps to prevent the undesirable phenomenon of “smoke”, which can occur when incoming electrons cause an accumulation of charge in the powder bed, thereby causing repulsive forces between the powder particles that might otherwise exceed the forces holding the powder particles together.
  • FIG. 2 shows a rough schematic representation of a cryogenic blasting system 50, which may be used in cleaning applications.
  • System 50 comprises a pelletiser 52, which is supplied with liquid CO2 and is arranged to transform the liquid CO2 into pellets of solid CO2 (dry ice). These pellets are then transferred into hopper 56 via outlet 54.
  • the hopper 56 supplies the pellets of solid CO2 to a rotary dosing disc 58, which is provided with a plurality of holes (not shown) into which pellets of solid CO2 can fall.
  • a supply of compressed gas is also provided in conduit 60.
  • Conduit 60 passes the compressed air to the dosing disc 58, so that any pellets that are within the holes in the dosing disc that align with the outlet of conduit 60 are suspended in the flow of compressed air.
  • the compressed gas and suspended pellets then pass into blasting hose 62, which supplies the mixture of compressed gas and pellets of solid CO2 to nozzle 64, which may be controlled by an operator or a robot to direct the flow towards an object to be cleaned.
  • the nozzle 64 may be provided with a user input means that allows the user controlling the nozzle to stop and start the flow through the nozzle, and optionally to also control the flow rate.
  • a stream of compressed gas containing particles of a solid cryogen effectively cleans surfaces, because sublimation of the particles of solid cryogen occurs substantially immediately upon contact between the solid particles and the surface of the article to be cleaned. This results in a sudden expansion of the cryogen, which can help to dislodge dirt or other contaminants from the surface. Furthermore, the low temperature of the cryogen can cause any liquids in the dirt to freeze and crack, which may help with their removal from the surface.
  • a cryogenic blasting apparatus as shown in figure 2 could be used to remove a cake of sintered powder from a component produced by additive manufacturing.
  • the present invention may be particularly useful for removing a cake of lightly sintered powder from the outside of a component produced by Electron Beam Melting (EBM), as EBM processes typically takes place at elevated temperature, so that the particles of powder on the powder bed are likely to be lightly sintered together, even in areas that have not intentionally been fused by the electron beam.
  • EBM Electron Beam Melting
  • Figure 3 shows an apparatus for removing a cake of sintered powder from the outside of a component 70 in an embodiment of the present invention.
  • Component 70 may have been produced by any suitable additive manufacturing method that uses metal powder as a feedstock material.
  • the present invention is particularly useful for removing a cake of powder from the surface of a component produced by Electron Beam Melting (EBM).
  • EBM Electron Beam Melting
  • the component 70 is located within a chamber 72.
  • the chamber 72 may be the build chamber in which the component was manufactured, in which case some or all of the components shown processing chamber 17 in figure 1 may be present within the chamber 72. Flowever, the component will typically be transferred from the build chamber 17 to a different chamber 72 for removal of the cake of powder.
  • a nozzle 64 of a cryogenic blasting system 50 is provided within the chamber 72.
  • the nozzle 64 is configured to direct a flow of compressed gas having particles of a solid cryogen such as solid CO2 therein.
  • the nozzle 64 is mounted on a robot arm 76, so that the direction of the flow of compressed gas and pellets of solid cryogen can be aimed in a desired direction.
  • a controller (not shown) may be provided to control the robot arm 76 and nozzle, so as to allow control of the direction, position and flow rate of the flow exiting the nozzle 64.
  • the other components of the cryogenic blasting system 50 may be the same as the components of the system shown in figure 2.
  • the cryogen reduces the temperature within the chamber 72. Accordingly, removal of the cake of powder using solid cryogen effectively eliminates the risk of a dust explosion occurring during the powder removal.
  • the compressed gas may consist of inert gas, such as argon or nitrogen, instead of compressed air. This may enable parts to be made by AM processes such as EBM using powders having a smaller size than has previously been possible, since the risk of a dust explosion has previously been higher when the particle size in the powder is small. As will be understood by the skilled person, reducing the particle size may allow components with an improved surface finish to be made by AM.
  • a further advantage of the use of cryogenic blasting is that the pellets of solid CO2 cannot be further oxidized and will thus not provide any fuel to an ignition event.
  • the particles used in the blasting process heat up from friction when they impact on the nozzle. If the powder particles are large enough, these sparks may not have sufficient energy to cause a dust explosion, however, they still cause oxidation of the powder particle that impacted on the nozzle.
  • the powder that was used in the blasting process and the powder from the cake surrounding the component is typically not usable for future AM processes, because it is contaminated with oxidized powder.
  • the present invention therefore allows for the powder from the cake to be re-used for future AM processes.
  • the source of compressed air may be replaced with a source of a compressed inert gas such as nitrogen or argon. This may be advantageous for components in which little or no oxidation is acceptable and where further concerns on dust explosion safety must be satisfied. In such cases, the air in the chamber 72 may be purged before the blasting process is started.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Plasma & Fusion (AREA)
  • Mechanical Engineering (AREA)
  • Optics & Photonics (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Sustainable Development (AREA)
  • Powder Metallurgy (AREA)

Abstract

La présente invention concerne un procédé et un dispositif correspondant pour éliminer un gâteau de poudre d'un élément fabriqué par un procédé de fabrication additive, le procédé comprenant l'application d'un flux de gaz sous pression à l'élément, une pluralité de particules d'un cryogène solide étant incluses dans le flux de gaz sous pression. Un tel procédé élimine sensiblement le risque d'explosion de poussière se produisant pendant l'élimination du gâteau de poudre.
PCT/EP2021/025015 2020-02-13 2021-01-18 Procédé et dispositif pour éliminer un excès de poudre d'éléments produits par fabrication additive WO2021160338A1 (fr)

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EP20020065.7 2020-02-13

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CN116638768A (zh) * 2023-05-31 2023-08-25 浙江拓博环保科技有限公司 一种3d打印工件智能清粉方法及系统

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116638768A (zh) * 2023-05-31 2023-08-25 浙江拓博环保科技有限公司 一种3d打印工件智能清粉方法及系统
CN116638768B (zh) * 2023-05-31 2023-11-17 浙江拓博环保科技有限公司 一种3d打印工件智能清粉方法及系统

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