WO2018194481A1 - Technique de fabrication additive comprenant le chauffage résistif direct d'une pièce - Google Patents

Technique de fabrication additive comprenant le chauffage résistif direct d'une pièce Download PDF

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Publication number
WO2018194481A1
WO2018194481A1 PCT/RU2017/000249 RU2017000249W WO2018194481A1 WO 2018194481 A1 WO2018194481 A1 WO 2018194481A1 RU 2017000249 W RU2017000249 W RU 2017000249W WO 2018194481 A1 WO2018194481 A1 WO 2018194481A1
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WO
WIPO (PCT)
Prior art keywords
workpiece
additive manufacturing
metal material
current
layer
Prior art date
Application number
PCT/RU2017/000249
Other languages
English (en)
Inventor
Dmitry Leonidovich NESTERENKO
Original Assignee
Siemens Aktiengesellschaft
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Siemens Aktiengesellschaft filed Critical Siemens Aktiengesellschaft
Priority to PCT/RU2017/000249 priority Critical patent/WO2018194481A1/fr
Publication of WO2018194481A1 publication Critical patent/WO2018194481A1/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
    • B22F10/20—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
    • 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
    • B22F12/10—Auxiliary heating 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
    • 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
    • B22F12/10—Auxiliary heating means
    • B22F12/13—Auxiliary heating means to preheat the material
    • 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
    • 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
    • B29C64/20—Apparatus for additive manufacturing; Details thereof or accessories therefor
    • B29C64/295—Heating elements
    • 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
    • B33Y30/00—Apparatus for additive manufacturing; Details thereof or accessories therefor
    • 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

  • Additive Manufacturing technique including direct resistive heating of a workpiece
  • the present invention relates to additive manufacturing (AM) and in particular to systems and methods of additive manufacturing having direct resistive heating of a workpiece.
  • AM additive manufacturing
  • additive Manufacturing also known as Additive Layer Manufacturing (ALM)
  • ALM Additive Layer Manufacturing
  • additive manufacturing is a relatively new consolidation process that is able to produce a functional complex part, layer by layer, without moulds or dies.
  • This process uses a powerful heat source such as a laser beam or a welding arc to melt a controlled amount of additive material, for example metal in the form of metallic powder or wire, which is then deposited, initially, on a building platform or a surface of a prefabricated workpiece. Subsequent layers are then built up upon each preceding layer.
  • this computer-aided manufacturing (CAM) technology builds complete functional parts or, alternatively, builds features on existing components i.e. on a workpiece, by adding material to the workpiece layer by layer rather than by removing it as is done in machining.
  • Additive manufacturing often starts by slicing a three dimensional representation, for example a CAD model, of a part to be manufactured into very thin layers, thereby creating a two dimensional image of each layer.
  • the part to be manufactured can be a part that is to be built on a workpiece, for example during repairing of a chipped turbine blade the chipped turbine blade is the workpiece and the patch formed to fill or reform the chipped part is the part that is built on the workpiece.
  • the workpiece is positioned on a build platform.
  • SLM selective laser melting
  • SLS selective laser sintering
  • mechanical pre-placement of a thin layer of metal powder of precise thickness on a surface of the workpiece and in adjoining horizontal surface above the build platform is achieved by using a mechanical wiper or by a powder spreading mechanism to sweep or spread a uniform layer of the powder or to screed the layer, after which an energy beam, such as a laser, is indexed across the powder layer according to the two dimensional pattern of solid material for the respective layer.
  • an energy beam such as a laser
  • the build platform, and therefore the horizontal plane of deposited material is lowered and the process is repeated until the three dimensional part is completely built on the workpiece as desired.
  • the operation is usually performed under an atmosphere of inert gas, such as argon or nitrogen.
  • SLM Selective Laser Melting
  • SLS Selective Laser Sintering
  • DMLS Direct metal laser sintering
  • DMLM Direct metal laser melting
  • the SLM/SLS technologies become widely used in various applications, the SLM/SLS technologies have some limitations such as surface roughness, part accuracy, and the formation of layered residual stresses, which are reinforced by the high thermal gradients due to melting and solidification in a very short time.
  • the SLM/SLS technologies processing parameters including laser power, laser scan speed, layer thickness and preheating, need to be varied and controlled.
  • One of the existing approaches for preheating the substrate and powder bed during SLM/SLS processes is based on heating building platform by installing a heating element underneath the building platform.
  • the building platform In this approach the building platform, and the all the powder stacked on top of it are be heated up.
  • passive cooling use of insulation
  • active cooling are applied.
  • the temperature of the base plate is constantly monitored by a thermocouple probe.
  • the current preheating system can achieve temperatures up to 500°C for long runs.
  • Infra-red heating Another approach is to heat up surface of the powder bed by using Infra-red heating.
  • Infra-red heaters are generally placed above the building platform to maintain a desired temperature (up to 900°C) of the powder bed and the powder in the feed cartridge.
  • each powder bed layer is scanned in two stages, the preheating stage and the melting stage.
  • preheating stage a high current laser beam with a high scanning speed is used to preheat the powder layer (up to 0.4 - 0.6 of melting temperature) in multiple passes .
  • Yet another approach is to use Induction heating, in which the powder bed along with a workpiece is placed inside an Induction coil surrounding the powder bed and the workpiece placed therein, and thus resulting into heating of the powder bed and the workpiece .
  • none of the aforementioned techniques provide directed and specific heating i.e. they do not primarily heat up the workpiece surface or a region of spread powder layer that is required to be heated, on the contrary they heat up the entire powder bed or feed cartridge or building platform. It will be beneficial to provide a technique that ensures primarily heating of the workpiece and of a region of the spread powder layer that is limited on top of the workpiece or that is limited on top of a previously added layer formed on the workpiece, before the AM process is carried out for the spread layer.
  • an object of the present invention is to provide an additive manufacturing technique, in particular an additive manufacturing apparatus and an additive manufacturing method for preheating, primarily, of the workpiece and of a region of the spread powder layer that is limited on top of the workpiece or that is limited on top of a previously added layer formed on the workpiece.
  • the additive manufacturing apparatus hereinafter also referred to as the AM apparatus or the apparatus, includes a part building module, a direct resistive heating arrangement and an energy beam arrangement.
  • the part building module bounds a bed of powdered metal material and includes a building platform.
  • the building platform receives and supports the bed of powdered metal material and a workpiece embedded within the bed of powdered metal material.
  • the direct resistive heating arrangement provides electrical current to the workpiece.
  • the direct resistive heating arrangement includes a current source and electrical contacts. The electrical contacts are attached to the workpiece and provide electrical current to the workpiece when so attached.
  • the energy beam arrangement selectively scans portions of a surface of the bed of powdered metal material to melt or sinter the selectively scanned portions onto the workpiece.
  • the electrical ' current provided to the workpiece by the direct resistive heating arrangement flows through the workpiece and causes heating of the workpiece as a result of electrical resistance of the workpiece (resistive heating) , and since the electrical current is directly provided to the workpiece it is referred to as direct resistive heating.
  • the electrical contacts may be removably clipped on the workpiece.
  • the current source may include mechanism to modulate characteristics of the electrical current provided to the workpiece, such as amount, voltage, and/or frequency of the electrical current.
  • the direct resistive heating heats up the workpiece directly, i.e. the heating is not effected by heating up the entire powder bed or the building platform, as is done in the aforementioned conventional additive manufacturing techniques.
  • the amount of heating of the workpiece can be controlled. Lesser amount of electrical current provided to the workpiece results in lesser heating, and vice versa.
  • the powder of the powder bed that is directly in contact and closely surrounding the workpiece also heats up. This helps in heating up a region of the powder layer that is limited on top surface of the workpiece and which subsequently is selectively scanned to be added to the workpiece .
  • the current source is an alternating current source or an alternating current generator.
  • the current source is a high frequency source.
  • Alternating current (AC) sources/generators are well known and readily available, and thus make the AM apparatus easy to construct.
  • AC current is known to have skin effect and the same happens in the workpiece, and thus AC current is beneficial in heating up the surface of the workpiece and the region of the powder layer adjacent to the surface of the workpiece.
  • High frequency AC source/generator is especially advantageous due to increased skin effect.
  • the current source is a direct current source or a direct current generator. Direct current (DC) sources/generators are well known and readily available, and thus make the AM apparatus easy to construct .
  • At least one of the electrical contacts is configured to be movable along a side surface of the workpiece while maintaining contact with the workpiece such that the electrical contact remains at fixed relative position with respect to the surface of the bed of powdered metal material.
  • one of the electrical contacts for example pins, connectors
  • another electrical contact is attached to an upper part of the workpiece
  • the movable electrical contact does not get lowered along with the workpiece.
  • the movable contact in fact remains fixed in its position and allows the workpiece to slide down while still maintaining contact with the workpiece.
  • an additive manufacturing method hereinafter also referred to as the AM method or simply as the method.
  • a workpiece is positioned on a building platform of a part building module of an additive manufacturing apparatus. Electrical contacts are attached to the workpiece. The electrical contacts are connected to a current source. Thereafter, a layer of powdered metal material is spread on the building platform and a surface of the workpiece positioned on the building platform. Thus the workpiece is embedded in a bed of the powdered metal material . Subsequently, direct resistive heating of the workpiece is performed by providing the workpiece with the electrical current from the current source via the electrical contacts attached to the workpiece.
  • one or more portions of a surface of the layer of powdered metal material are selectively scanned by an energy beam arrangement, thereby melting or sintering the selectively scanned portions onto the underlying workpiece .
  • the electrical current provided to the workpiece flows in the workpiece and causes heating of the workpiece as a result of electrical resistance of the workpiece.
  • the electrical contacts may be removably clipped on the workpiece.
  • the direct resistive heating heats up the workpiece directly, i.e. the heating is not effected by heating up the entire powder bed or the building platform, as is done in the aforementioned conventional additive manufacturing methods .
  • the electrical current provided to the workpiece may be modulated, i.e. an amount, a voltage, and/or a frequency of the electrical current may be changed or adjusted. By increasing or decreasing the electrical current, the amount of heating of the workpiece is controlled. As a result of heating of the workpiece the powder of the powder bed that is adjacent to the workpiece also heats up.
  • the electrical current provided to the workpiece in performing direct resistive heating of the workpiece is alternating current.
  • the alternating current is high frequency alternating current.
  • Alternating current (AC) sources/generators are well known and readily available. AC current is known to have skin effect and the same occurs in the workpiece, and thus AC current is beneficial in heating up the surface of the workpiece and the region of the powder layer adjacent to the surface of the workpiece. High frequency AC current is especially advantageous due to increased skin effect.
  • the electrical current provided to the workpiece in performing direct resistive heating of the workpiece is direct current.
  • Direct current (DC) sources/generators are well known and readily available.
  • the building platform is lowered along with the workpiece and an existing bed of powdered metal material. The lowering of the building platform provides space on top of the existing bed of powdered metal material to accommodate a new layer of powdered metal material to be subsequently spread.
  • the workpiece at this stage of the method includes the previously formed layer.
  • the new layer of powdered metal material is spread on the existing bed of powdered metal material, i.e. supported on the building platform, and on a surface of the previously formed layer of the workpiece positioned on the building platform. Therefore, the new layer of powdered metal material spreads continuously over the existing bed of powdered metal material and the surface of the previously formed layer of the workpiece.
  • direct resistive heating of the workpiece is performed by providing the workpiece with the electrical current from the current source via the electrical contacts attached to the workpiece.
  • one or more portions of a surface of the new layer of powdered metal material are selectively scanned by the energy beam arrangement to melt or sinter the selectively scanned portions onto the workpiece.
  • the method can be repeated in a looped manner and each new layer added to the powder bed may be heated up using the method of the present technique before being melted or sintered, and consequently added, onto the workpiece.
  • the electrical current provided in performing direct resistive heating of the workpiece that includes the previously formed layer is alternating current.
  • the alternating current is high frequency alternating current .
  • the electrical current provided in performing direct resistive heating of the workpiece that includes the previously formed layer is direct current .
  • the electrical current from the current source via the electrical contacts is supplied to the workpiece continuously from the performing of direct resistive heating of the workpiece to the performing of direct resistive heating of the workpiece that includes the previously formed layer.
  • the rate of cooling of the previously formed layer may be controlled, as the cooling rate will depend on the amount of electrical current provided.
  • FIG 1 schematically illustrates a conventionally known additive manufacturing system
  • FIG 2 schematically illustrates an exemplary embodiment of an additive manufacturing apparatus having a direct resistive heating arrangement, in accordance with aspects of the present technique
  • FIG 3 schematically illustrates exemplary embodiment of positioning of a workpiece and of electrical contacts of the direct resistive heating arrangement during performance of the direct resistive heating in accordance with aspects of the present technique; schematically illustrates exemplary embodiment of a subsequent positioning, compared to the positioning depicted in FIG 3, of the workpiece and of the electrical contacts of the direct resistive heating arrangement during further performance .of the direct resistive heating in accordance with aspects of the present technique; presents a flow chart representing an additive manufacturing method of the present technique; schematically illustrates an exemplary embodiment of positioning of electrical contacts of the direct resistive heating arrangement where one of the electrical contacts is movable; schematically illustrates an exemplary embodiment of the movable electrical contact of the direct resistive heating arrangement; schematically illustrates another exemplary embodiment of the movable electrical contact of the direct resistive heating arrangement; schematically illustrates yet another exemplary embodiment of the movable electrical contact of the direct resistive heating arrangement; and schematically illustrates a further exemplary embodiment of the movable electrical contact of the direct resistive heating arrangement; in accordance with aspects of
  • the basic idea of the present technique is to heat a workpiece, onto which layers are to be added by using AM techniques, directly by using the electrical resistance of the workpiece.
  • electrical current is directly passed through the workpiece it results into heating of the workpiece depending on the characteristics of the electrical current provided and the electrical resistance of the workpiece. Therefore heating of the workpiece is direct, in the sense that it does not come from heating of the building platform or of the surrounding powder bed.
  • direct heating of the workpiece causes indirect heating of the powder adjoining the workpiece as a result of conduction of the heat from the workpiece to the adjoining powder, additionally the powder particles that are in direct contact with the workpiece surface also experience direct resistive heating.
  • FIG 1 schematically represents a conventionally known additive manufacturing system 2.
  • the system 2 generally includes a part building module 10, also known as the build chamber 10, in which a part is build by additive manufacturing (AM) for example by SLM or SLS processes.
  • the part building module 10, hereinafter also referred to as the module 10, is a container for example a box shaped or barrel shaped container and having a top side of the container open.
  • FIG 1 represents such a container having side walls 11, 12 and a bottom surface 15.
  • the side walls 11, 12 and the bottom surface 15 together define a space in which the part is built.
  • the space receives a workpiece 5 when the part is built onto the workpiece 5 for example as a part or integral addition to the workpiece 5.
  • the workpiece 5 is an object that is supposed to be worked on by the AM system and built upon by addition of layer after layer by a suitable AM process by adding layer after layer of powdered metal material 7.
  • the powder metal material 7 is provided by a powder storage module 20, also known as the feed cartridge 20, that stores the powdered metal material 7, hereinafter also referred to as the powder 7.
  • the powder 7 in the feed cartridge 20 is stored in an open top container having side walls 21, 22 and a bottom 26.
  • the bottom 26 is placed on top of a piston 28 that makes the bottom 26 slide or move in Z direction, as represented by the co-ordinate system shown in FIG 1.
  • the powder 7 from the container 20 is raised above and outside the container 20.
  • the powder 7 is then spread as top surface 9 of a bed 8 of the powder 7 in the module 10 by using a powder spreading mechanism 30 which evenly spreads a thin layer of the powder 7 on the module 10.
  • the layer spread has a thickness of few micrometers, for example between 20 ⁇ and 100 ⁇ .
  • the module 10 or the build chamber 10 binds the bed 8 of powdered metal material 7 limiting the bed 8 by the side walls 11, 12 and the bottom surface 15.
  • the module 10 also includes a building platform 16, and the bottom surface of the container of the module 10 is formed by the building platform 16, also known as the build platform 16 or simply as the platform 16.
  • the platform 16 receives and supports the bed 8 of powdered metal material 7 and also the workpiece 5 that is positioned on the platform 16 embedded within the bed 8.
  • the platform 16 is placed on top of a piston 18 that makes the platform 16 slide or move in Z direction, as represented by the co-ordinate system shown in FIG 1. When the piston 18 moves downward in the Z direction, i.e.
  • the bed 8, along with the workpiece 5, is lowered thereby creating a space at surface 9 of the container of the module 10 to accommodate the layer that is spread by the spreading mechanism 30.
  • the layer so spread by the spreading mechanism forms the surface 9 of the bed 8 and also covers a surface 55 of the workpiece 5.
  • the system 2 also includes an energy beam arrangement 40.
  • the energy beam arrangement 40 generally has an energy source 41 from which an energy beam 42 such as a Laser beam 42 or an electron beam 42 is generated, and a scanning mechanism 44 that directs the beam 42 to specific selected parts of the surface 9 of the powder bed 8 to melt or sinter the selectively scanned portions onto the workpiece 5.
  • the specific portions of the surface 9 to which the beam 42 is directed are referred to as scanned.
  • the selections of portions that are to be scanned by the beam 42 by action of scanning mechanism 44 are based on a 3D model, for example a CAD model, of the part that has to built on the workpiece 5.
  • the portions of the surface 9 that are selectively scanned by the beam 42 are generally limited on top of the surface 55 and thus are able to melt or sinter and be added to the surface 55 of the workpiece 5. Once added to the workpiece 5, the portions of the layer so added form part of the workpiece 5.
  • the build chamber 10, the feed cartridge 20, the spreading mechanism 30, and the energy beam arrangement 40 are well known in the art of additive manufacturing thus not described herein in further details for sake of brevity.
  • FIG 2 schematically represents an additive manufacturing apparatus 1 according to the present technique.
  • the additive manufacturing apparatus 1 hereinafter also referred to as the AM apparatus 1 or simply as the apparatus 1, includes the build chamber 10, the feed cartridge 20, the powder spreading mechanism 30, and the energy beam arrangement 40 as explained in reference to FIG 1. Additionally, the apparatus 1 includes a direct resistive heating arrangement 60.
  • the direct resistive heating arrangement 60 hereinafter also referred to as the heating arrangement 60 or simply as the arrangement 60, is configured to provide electrical current to the workpiece 5 and thus performing direct resistive heating of the workpiece 5.
  • the heating arrangement 60 includes a current source 62, electric connectors 64 and electrical contacts 66. The electrical contacts 66 are configured to be attached to the workpiece 5.
  • the electric contacts 66 are able to be removably attached, i.e. the contacts 66 may be attached and then detached without causing any change in shape or configuration of the workpiece 5.
  • One example of contacts 66 may be an electrical clip, like a binder clip, that is able to be clipped on to or attached to the workpiece 5 and then easily removed when desired by opening the clip.
  • the electric connectors 64 for example electrical wire, connect the current source 62 to the contacts 66 and thus allow flow of electrical current from the current source 62 to the contacts 66 and thereafter to the workpiece 5, when the contacts 66 are connected onto the workpiece 5.
  • the electrical connections 64 along with the contacts 66 may resemble one end of a jumper cable that is used to jump start a car by connecting it to a dead car battery, which resembles in this case the workpiece 5 , from a healthy car battery which resembles in this case the current source 62 that supplies the electrical current.
  • the electrical current provided to the workpiece 5 by the heating arrangement 60 flows in the workpiece 5 and consequently causes heating of the workpiece 5 as a result of electrical resistance of the workpiece 5.
  • the heating arrangement 60 or the current source 62 of the heating arrangement 60 may include mechanism to modulate characteristics of the electrical current provided to the workpiece 5, such as amount, voltage, and/or frequency of the electrical current.
  • the mechanism to modulate characteristics of the electrical current may be, but not limited to, a frequency changer or a frequency convertor, a voltage regulator, a voltage convertor, and so on and so forth.
  • a frequency changer or a frequency convertor By modulating the electric current i.e. by increasing or decreasing frequency and/or voltage of the electric current an amount of heating of the workpiece 5 is controlled.
  • the current source 62 may be an alternating current source or an alternating current generator.
  • the current source 62 is a high frequency source, which can be achieved by an AC current source 62 coupled with a frequency changer.
  • High frequency as used herein includes a frequency greater than 1kHz .
  • the current source 62 is a direct current source or a direct current generator, for example a battery.
  • the present technique also presents an additive manufacturing method 100, hereinafter also referred to as the AM method 100 or simply as the method 100, as depicted in the flow chart of FIG 5.
  • the method 100 is implemented by the AM apparatus 1 as explained hereinabove with respect to FIGs 1 and 2.
  • the method 100 of the flow chart of FIG 5 is explained hereinafter in combination with FIGs 3 and .
  • references have been made to the AM apparatus 1 and its components such as the building platform 16 that may be understood to be same as that explained in reference to FIGs 1 and 2.
  • a workpiece 5 is positioned on the building platform 16 of the build chamber 10 of an AM apparatus, for example the AM apparatus 1 of FIG 2.
  • the electrical contacts 66 are attached to the workpiece 5.
  • the electrical contacts 66 are connected to the current source 62.
  • FIG 3 depicts a workpiece positioned on the platform 16 and to which the contacts 66 are attached.
  • a layer 70 as shown in FIG 3, of powdered metal material 7 is spread on the platform 16 and the surface 55 of the workpiece 5.
  • the workpiece 5 along with the surface 55 is completely embedded in a bed 8 of the powdered metal material 7 after the layer 70 has been spread.
  • direct resistive heating of the workpiece 5 is performed by providing the workpiece 5 with the electrical current from the current source 62 via the electrical contacts 66 attached to the workpiece 5.
  • a step 150 one or more portions of the surface 9 of the layer 70 of the powder 7 are selectively scanned by the energy beam arrangement 40, thereby melting or sintering the selectively scanned portions onto the underlying workpiece 5, or more particularly to the surface 55 of the workpiece 5.
  • the electrical current provided to the workpiece 5 in the step 140 may be modulated, i.e. an amount, a voltage, and/or a frequency of the electrical current may be changed or adjusted during the step 140.
  • the surface 55 of the workpiece 5 also heats up
  • the powder 7 of the powder bed 8 that is adjacent to the workpiece 5 also heats up for example the powder 7 in a region 77 of the layer 70.
  • the region 77 is the portion of the layer 70 that is limited on top of the surface 55 of the workpiece 5.
  • the direct resistive heating performed in the step 140 causes a pre-heating of the powder 7 in the region 77 of the layer 70 i.e. the powder 7 in the region 77 of the layer 70 is heated before the selective scanning is performed in the step 150.
  • the electrical current provided to the workpiece 5 ' in the step 140 is alternating current.
  • the alternating current is high frequency- alternating current, for example AC in frequency greater than 1kHz .
  • the electrical current provided to the workpiece 5 in the step 140 is direct current.
  • the workpiece 5 now has an additional layer or an added layer 75, as shown in FIG 4, which is hereinafter referred to as the previously added layer 75 or previously formed layer 75 for further steps of the method 100. It may be noted that besides the portions of the layer 70 that were sintered or melted in the step 150 of the method 100, the remaining portions of the layer 70 are present in adjoining area of the sintered or melted portions and now form part of the powder bed 8, now also referred to as the existing powder bed 8.
  • the method 100 may be continued further as follows:
  • a step 160 following the step 150, the platform 16 is lowered in the direction 19 (shown in FIGs 1 and 2) along with the workpiece 5 and the existing bed 8 of powdered metal material 7.
  • a space on top of the existing bed 8 is generated.
  • the space so generated is same as the thickness of the next layer that is to be spread on the powder bed 8.
  • a new layer 80 is spread in a step 170 by using the spreading mechanism 30 and the powder 7 provided by the feed cartridge 20.
  • the space created in the step 160 accommodates the new layer 80 of powdered metal material 7 which now forms the surface 9 of the powder bed 8.
  • the new layer 80 also spreads continuously over the previously formed layer 75 of the workpiece 5.
  • the workpiece 5 at this stage has a surface 56, which includes a surface of the previously formed layer 75.
  • step 180 direct resistive heating of the workpiece 5 having the previously added layer 75 is performed, by providing the workpiece 5 with the electrical current from the current source 62 via the electrical contacts 66 attached to the workpiece 5.
  • step 180 the workpiece 5 including the surface 56 of the workpiece 5 heats up.
  • step 190 one or more portions of the surface 9 of the new layer 80 of powdered metal material 7 are selectively scanned by the energy beam arrangement 40 to melt or sinter the selectively scanned portions onto the workpiece 5.
  • the electrical current provided to the workpiece 5 in the step 180 may be modulated, i.e.
  • an amount, a voltage, and/or a frequency of the electrical current may be changed or adjusted during the step 180.
  • the surface 56 of the workpiece 5 also heats up
  • the powder 7 of the powder bed 8 that is adjacent to the workpiece 5 also heats up for example the powder 7 in a region 87 of the layer 70, as shown in FIG 4.
  • the region 87 is the portion of the layer 80 that is limited on top of the surface 56 of the workpiece 5.
  • the direct resistive heating performed in the step 180 causes a pre- heating of the powder 7 in the region 87 of the layer 80 i.e. the powder 7 in the region 87 of the layer 80 is heated before the selective scanning is performed in the step 190.
  • the electrical current provided to the workpiece 5 in the step 180 is alternating current.
  • the alternating current is high frequency- alternating current, for example having same frequency range as the AC provided in the step 140.
  • the electrical current provided to the workpiece 5 in the step 180 is direct current.
  • the electrical current may be provided intermittently i.e. only before the performance of the subsequent selective scanning steps such as the step 190.
  • electrical current may be provided or supplied continuously for example in another embodiment of the method 100, the electrical current is supplied to the workpiece 5 continuously from the step 140 to the step 180.
  • the electrical current when supplied continuously may be modulated to control the heating rate or cooling rate of the workpiece 5.
  • FIGs 6 to 10 are used to explain different type of the electrical contacts 66 that may be used in the AM apparatus 1 of FIG 2 and/or the AM method 100 of FIG 5.
  • the AM apparatus 1 may include at least one electrical contact 66 that is configured to be movable along a side surface 57 of the workpiece 5 while maintaining contact with the workpiece 5, and more particularly while maintaining contact with the side surface 57 of the workpiece 5.
  • Such an electrical contact 66 of the AM apparatus 1 is hereinafter referred to as the movable contact 67.
  • the AM apparatus 1 may include at least one movable electrical contact 67 that moves relative to the workpiece 5, along the side surface 57 of the workpiece 5, while maintaining contact with the workpiece 5 such that the movable contact 67 remains at fixed relative position with respect to the surface 9 of the bed 8 of powdered metal material 7.
  • the movable connector 67 includes a contact head 92, a spring- loaded element 94 and a contact base 96.
  • the contact head 92 established direct physical contact with the workpiece 5.
  • the contact base 96 is fixed to the or within the side wall 11 of the build chamber 10.
  • the contact base 96 supports the spring- loaded element 94 that extends out from the contact base 96 towards the workpiece 5, when present.
  • the spring-loaded element 94 is present between the contact head 92.
  • the spring-loaded element 94 is compressed when the workpiece 5 is positioned in the build chamber 10 and in the compressed position of the spring-loaded element 94 the contact head 92 pushes, albeit gently, against the side surface 57.
  • the contact head 92 for example may be, but not limited to, a gear-shaped pin as shown in FIG 7 or a ball-shaped pin as shown in FIGs 8 to 10.
  • the contact head 92 brushes along the side surface 57 of the workpiece 5 and allows the workpiece 5 to slide down, without causing bending or angular motion of the contact head 92. While the workpiece 5 moves down, the side surface 57 of the workpiece 5 brushing against the contact head 92, the contact head 92 remains pressed onto the side surface 57 due to the compressed state, of the spring-loaded element 94.
  • the contact base 96 may be present on the surface of the wall 11 or present embedded in the wall 11.
  • the spring- loaded element 94 may extend between the contact head 92 and the contact base 96 as shown in FIG 7 and 8. Alternatively a part of the spring-loaded element 94 or the entire spring- loaded element 94 may be present confined within the contact base 96 as shown in FIGs 9 and 10. While the present technique has been described in detail with reference to certain embodiments, it should be appreciated that the present technique is not limited to those precise embodiments. Rather, in view of the present disclosure which describes exemplary modes for practicing the invention, many modifications and variations would present themselves, to those skilled in the art without departing from the scope and spirit of this invention. The scope of the invention is, therefore, indicated by the following claims rather than by the foregoing description. All changes, modifications, and variations coming within the meaning and range of equivalency of the claims are to be considered within their scope.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Plasma & Fusion (AREA)
  • Powder Metallurgy (AREA)

Abstract

La présente invention concerne une technique de fabrication additive. Une pièce est positionnée sur une plate-forme de construction d'un module de construction de pièce d'un appareil de fabrication additive. Des contacts électriques sont fixés à la pièce. Les contacts électriques sont connectés à une source de courant. Une couche de matériau métallique en poudre est étalée sur la plate-forme de construction et sur une surface de la pièce positionnée sur la plate-forme de construction. Ainsi, la pièce est incorporée dans un lit du matériau métallique en poudre. Ensuite, un chauffage résistif direct de la pièce est effectué en fournissant à la pièce le courant électrique provenant de la source de courant par l'intermédiaire des contacts électriques fixés à la pièce. Enfin, une ou plusieurs parties d'une surface de la couche de matériau métallique en poudre sont balayées de manière sélective par un agencement de faisceau d'énergie, ce qui permet de faire fondre ou de fritter les parties balayées de manière sélective sur la pièce sous-jacente.
PCT/RU2017/000249 2017-04-19 2017-04-19 Technique de fabrication additive comprenant le chauffage résistif direct d'une pièce WO2018194481A1 (fr)

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DE102019003380A1 (de) * 2019-05-14 2020-11-19 Bundesrepublik Deutschland, vertr. durch das Bundesministerium der Verteidigung, vertr. durch das Bundesamt für Ausrüstung, Informationstechnik und Nutzung der Bundeswehr Verfahren zur Glättung einer Oberfläche eines additiv gefertigten, elektrisch leitenden Bauteiles
DE102019208836A1 (de) * 2019-06-18 2020-12-24 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Verfahren zur Herstellung von formkomplexen dreidimensionalen Bauteilen
DE102019208837A1 (de) * 2019-06-18 2020-12-24 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Verfahren zur Herstellung von formkomplexen dreidimensionalen Bauteilen
CN115135485A (zh) * 2020-04-17 2022-09-30 弗里曼特有限公司 粉末床的预热

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DE102019003380A1 (de) * 2019-05-14 2020-11-19 Bundesrepublik Deutschland, vertr. durch das Bundesministerium der Verteidigung, vertr. durch das Bundesamt für Ausrüstung, Informationstechnik und Nutzung der Bundeswehr Verfahren zur Glättung einer Oberfläche eines additiv gefertigten, elektrisch leitenden Bauteiles
DE102019208836A1 (de) * 2019-06-18 2020-12-24 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Verfahren zur Herstellung von formkomplexen dreidimensionalen Bauteilen
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